Symposium Organizers
Seung Min Han, Korea Advanced Institute of Science and Technology (KAIST)
Arief Budiman, Singapore University of Technology and Design
Amit Misra, University of Michigan–Ann Arbor
Ruth Schwaiger, Karlsruhe Institute of Technology
NM6.1: 3D Hierarchical Structures
Session Chairs
Tuesday PM, April 18, 2017
PCC West, 100 Level, Room 106 C
11:30 AM - *NM6.1.01
Resilient 3-Dimensional Nanocomposites—From Nano-Architected Meta-Materials to Human Bone
Julia Greer 1
1 , California Institute of Technology, Pasadena, California, United States
Show AbstractWe present the fabrication of 3-dimensional nano-lattices whose constituents vary in size from several nanometers to tens of microns to millimeters. We discuss the deformation and mechanical properties of nano-architected, often hierarchically-arranged, natural (bone) and synthesized (nanolattices) solids with different microstructures deformed in an in-situ nanomechanical instrument. Attention is focused on the interplay between each internal critical microstructural length scale of materials and their external limitations in revealing the physical mechanisms that govern the mechanical deformation, where competing material- and structure-induced size effects drive overall properties. We provide specific examples where such hierarchical 3-dimensional architected meta-materials have direct applications in ultra lightweight batteries, biomedical devices, cell scaffolding, and in developing damage-tolerant ultralightweight materials.
12:00 PM - NM6.1.02
Biomimetic, Strong Yet Tough Composites through 3D Printing
Yinning Zhou 1 , Ihor Radchenko 1 , Avinash Baji 1 , Arief Budiman 1
1 , Singapore University of Technology and Design, Singapore Singapore
Show AbstractNature has taught us fascinating strategies to fabricate novel materials that exhibit superior structural properties. Here, we utilized melt-electrospinning to mimic the molecular-level structures found in natural materials such as mantis dactyl club. Tensile tests revealed that these 3D helicoidal fibrous structures (fiber size with tens of microns) exhibited much higher toughness and ductility compared to unidirectional samples obtained using melt-electrospinning fibers and their bulk counterparts. However, the tensile strength of the helicoidal samples was seen to be lower. Toughness was estimated to be the area under engineering strain-stress curve. To improve the tensile strength of the helicoidal samples, functional groups (carboxyl and amino group) were added on each side of monolayer melt-electrospinning fiber samples using surface treatment techniques. Following this step, the monolayers were assembled to yield surface treated biomimetic helicoidal structure. These samples demonstrated much higher toughness than unidirectional melt-electrospinning fibers and its bulk counterpart. For example, toughness of surface treated helicoidal sample was two times higher than surface treated unidirectional sample and five times higher than helicoidal sample prepared without any surface treatment. Additionally, the tensile strength of these samples was also seen to be substantially increased. We believe this represent the first successful attempt to mimic the 3D helicoidal architectures in small scales, and we still have room to continue towards generating modeled architectures with even smaller fiber size. These lightweight synthetic analogue materials enabled by 3D printing methodologies would potentially display superior structural properties and functionalities such as high strength, extreme toughness and deformability.
12:15 PM - NM6.1.03
Nanomechanical Behavior of 3D Silicon-Based Kirigami Structures Using Flat Punch Indentation
Mohammad Humood 1 , Mengdi Han 2 , Yan Zheng 2 , Matt Pharr 1 , John Rogers 2 , Andreas Polycarpou 1
1 , Texas A&M University, College Station, Texas, United States, 2 , University of Illinois at Urbana Champaign, Champaign, Illinois, United States
Show AbstractWe have constructed complex three dimensional (3D) kirigami architectures of Si with enhanced mechanical robustness. Photolithography and reactive ion etching produced patterned cuts in 2D bilayers of Si and SU8 epoxy. Transfer printing enabled integration of these structures with a pre-stretched elastomeric substrate. Upon release of the pre-strain, the structures delaminated and buckled up from the substrate nearly everywhere but remained attached at pre-defined bonding sites.
Transfer of these 3D structures to Si substrates provided a rigid support for the subsequent indentation/compression experiments. Flat punch microindentation and nanoindentation enabled studies of the mechanical behavior of these structures under compression. Analysis of the load-displacement curves allowed for measurement of the effective modulus and buckling strength of various 3D structures. Moreover, the microindentation studies indicated distinct regimes in the compressive force/displacement curve. Cylic indentation demonstrated the flexibility of the structures when subjected to repeated loading and allowed for evaluation of their elastic recovery over time. Loading at various strain-rates lead to a better understanding of creep behavior and energy dissipation in these systems. Complementary computational modeling supports our experimental findings.
12:30 PM - NM6.1.04
Manipulation of Nanomaterials Using Ion Beams—Toward Scalable Fabrication of Solid-State Nanopores
Morteza Aramesh 1 3 , Livie Dorwling-Carter 1 , Ivan Shorubalko 2 , Tomaso Zambelli 1 , Janos Voros 1
1 Laboratory of Biosensors and Bioelectronics, ETH Zurich, Zurich Switzerland, 3 , Queensland University of Technology (QUT), Brisbane, Queensland, Australia, 2 , Empa–Swiss Federal Laboratories for Materials Science and Technology, Dubendorf Switzerland
Show AbstractSolid state nanopores have been widely used for the development of gene sequencing and nucleic acid detection. Fabrication of nano-meter sized pore structures have been limited to a few techniques, such as electron/ion-beam milling, electron/ion-beam sculpting and solution-based ion etching; none being efficient to produce long-range ordered arrays of nanopores.
Here we report a new approach for scalable fabrication of high-density array of nanopores in thin solid-state membranes. By manipulating ion-matter interactions at nanoscales, we were able to fabricate nanohole arrays in different materials such as alumina, silicon nitride and graphene 2D sheets. The fabrication process is a new generation of the so-called “ion shaping” approach which has been used for fabrication of single nanopores in thin membranes since 2001.[i] We implemented real-time ion-shaping using an ion microscope to reduce the size of the pores in highly-porous thin films.
This approach not only enables a straightforward fabrication of high-density (1011 pores/cm2) array of pores, but also could be adopted to fabricate single nanopores in fluidic devices. As a practical example, we have fabricated pores in so-called “Fluid Force Microscope”[ii] tips with nano-meter diameter precision. We will use these tips to investigate translocation of biomolecules through nanopores in-vitro.
Compared to other techniques, this approach substantially improves the processing times and because of its facile and scalable fabrication it can potentially revolutionize nanopore-based gene sequencing techniques.
[i] Li, Jiali, et al. "Ion-beam sculpting at nanometre length scales." Nature 412.6843 (2001): 166-169.
[ii] Meister, André, et al. "FluidFM: combining atomic force microscopy and nanofluidics in a universal liquid delivery system for single cell applications and beyond." Nano letters 9.6 (2009): 2501-2507.
12:45 PM - NM6.1.05
Additive Nanoparticle Assembly for Hierarchical 3D Micro-Architected Materials and their Mechanical Behavior
Mohammad S. Saleh 1 , Chunshan Hu 1 , Sepehr Nesaei 1 , Arda Gozen 1 , Jonghyun Park 2 , Rahul Panat 1
1 , Washington State University, Pullman, Washington, United States, 2 , Missouri University of Science and Technology, Rolla, Missouri, United States
Show AbstractSeveral natural materials have evolved to have 3-D hierarchical structures and have multi-functionality. For example, biological materials with hierarchical architectures over multiple length scales can be light-weight, mechanically strong, semi-selectively permeable, and strain tolerant. Artificially fabricated metal or ceramic foams can show high strength to weight ratio and can mimic the biological systems mentioned above. Fabrication of these materials, however, is challenging and many of the current methods utilize polymer templating and material removal methods that require the use of environmentally harmful chemical processes. Here, we present a bio-inspired additive method of direct pointwise printing of nanoparticles to fabricate 3-D micro-architected structures without any templating or complicated post processing. We assemble metal nanoparticles using condensation and evaporation of aerosolized microdroplets to directly craft complex 3-D materials with a size-scale control over five orders of magnitudes. Highly sophisticated 3-D micro-lattices, spirals, pillars, and stretchable interconnects are demonstrated. We also study the 3-D micro-lattices under compression for potential applications in strain tolerant materials with ultra-low density. Finally, FEA simulations are carried out to capture the compression behavior of these structures. The proposed assembly method could be adapted to the state-of-the-art droplet-on-demand printing technologies for fast and large scale fabrication of micro-architected materials and also extend the NP-based printed electronics to the spatial (third) dimension.
NM6.2: Biocomposites
Session Chairs
Tuesday PM, April 18, 2017
PCC West, 100 Level, Room 106 C
2:30 PM - *NM6.2.01
Molecular Design and Mechanical Behavior of Low-Density Hyper-Confined Molecular Hybrids
Reinhold Dauskardt 1
1 , Stanford University, Stanford, California, United States
Show AbstractThe exceptional mechanical properties of polymer nanocomposite hybrids are achieved through intimate mixing of the polymer and inorganic phases, which leads to spatial confinement of the polymer phase. The nature and degree of this confinement varies considerably, from macroscopic constraint in multilayer laminate systems to true nanoscale confinement in polymer nanocomposites. We probe the mechanical and fracture properties of polymers in the extreme limits of molecular confinement, where a stiff inorganic matrix phase confines the polymer chains to dimensions far smaller than their bulk radius of gyration.
We show that polymers confined at such molecular length scales dissipate energy through a novel, confinement-induced molecular bridging mechanism in which individual confined polymer chains pull out from a nanoporous matrix. This mechanism contrasts with toughening processes in bulk and weakly-confined polymers and describes behavior that cannot be explained by existing entanglement-based theories of polymer deformation and fracture. We support the molecular bridging mechanism with a model that captures the associated nanomechanical processes, including the sliding friction of chain pullout, the deformation and stretching of confined polymer chains, and the eventual backbone scission of polymer molecules under extreme loads.
We next describe the effects of controlling the interaction of the confined molecules with the confining matrix by surface functionalization of the matrix pores. Molecular mechanics models that describe the pore wall interactions are provided leading to unique insights into the frictional interaction of the polymer molecules with the matrix confinement itself. Finally, we have developed a new class of high-temperature light-weight hybrids that incorporate a polyimide molecular phase. We demonstrate remarkable polyimide filling, imidization and cross-linking reactions in the highly confined matrix pores despite the simultaneous imidization reactions that decrease their solubility and conformational freedom, and raise their glass transition temperature. The work provides new insight into the mechanical behavior of polymer chains under nanoscale confinement and suggests potential routes for the molecular design and processing of multifunctional nanocomposite hybrids.
3:00 PM - NM6.2.02
Effect of Additives on the Mechanical Properties of Calcite
Shefford Baker 1 , Joseph Carloni 1 , Lara Estroff 1
1 , Cornell University, Ithaca, New York, United States
Show AbstractCalcite is a common component in biogenic structures such as seashells. Although calcite in its pure crystalline form is brittle and weak, its strength in these applications is significantly enhanced (by about a factor of two) by the inclusion of magnesium and a variety of organic molecules. Recent efforts have focused on creation of synthetic nanocomposite calcite model systems to help determine how these additives contribute to strength. However, the physical size of synthetic crystals is typically quite small (about 20 µm). We have studied hardening mechanisms in biogenic and synthetic calcites using nanoindentation and have developed simple dislocation-based models to describe how inclusions ranging from atomic substitutions to occluded second phase particles contribute to strength. In particular, we have been able to describe the effects of occluded small molecules, which have attributes of both solutes and second phase particles, quite accurately using a model with no adjustable parameters. These models help us to understand the performance of the biogenic materials, and facilitate the development of stronger synthetic calcite-based nanocomposites for a variety of applications.
3:15 PM - NM6.2.03
Embedded Sensing of Damage Mechanics in a Composite Structure
Asha Hall 1
1 , U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland, United States
Show Abstract
The integrity of composite structures gradually degrades due to the onset of damage such as matrix cracking, fiber/matrix debonding, and delamination. Over the last two decades, great strides have been made in structural health monitoring (SHM) community using various sensing techniques such as acoustic emission, eddy current, strain gages, etc., to diagnose damage in aerospace, mechanical and civil infrastructures. Embedded sensing offers the prospects of proving for real-time, in-service monitoring of damage were weight savings is a major factor in Aerospace Industry. In this present work, magnetostrictive particles such as Terfenol-D were embedded in a composite structure, along with multiple SHM techniques, to capture the damage in an IM7-carbon fiber reinforced polymer composite system undergoing fatigue loading. As the internal stress state increases, the change in the magnetization flux intensity was captured using a non-contact magnetic field sensor. A damage diagnosis system was established along with an acoustic emissions technique to further validate the damage captured by the embedded system.
3:30 PM - NM6.2.04
Micro/Nanoscale Tribological and Mechanical Investigation of the Articular Surfaces of the Insect Species—Potential for Developing Bioinspired Lubrication Systems
Jun Kyun Oh 1 , Cengiz Yegin 1 , Luis Cisneros-Zevallos 1 , Mustafa Akbulut 1
1 , Texas A&M University, College Station, Texas, United States
Show AbstractNature has evolved to achieve a desired functionality of the materials from the macroscale to the molecular scale, thus can guide to fabricate promising tribological materials. Biomimetics derived from nature is the great interest in the field of tribology, which consider the friction, wear, efficiency, durability, and long-term sustainability, and also provide suitable solutions without losing the intrinsic tribological and mechanical properties. This work presents an experimental study on the structural examination focusing on the tribological and mechanical testing through the joints of the katydid (Orthoptera: Tettigoniidae). The tibial and femoral articular surfaces of the katydid joints showed the nanosmooth and micro/nanotextured surface characteristics, respectively. The articular surfaces with micro/nanoscale structural features demonstrated topographies for reducing the total number of the contact points. The micro/nanoscale periodic patterns (i.e., groove, lamellar, and hillock) with the hierarchical structures on the femoral articular surfaces which are in contact with the nanosmooth tibial articular surfaces allow enhancing the tribological properties, exhibiting considerably low friction. The friction coefficient (μ) values of 0.097 ± 0.002 (tibia-executicle), 0.064 ± 0.002 (femur-exocuticle), and 0.053 ± 0.001 (tibia-femur) were recorded against “tibia-attached tip” (tibia contact region) and “femur-attached tip” (femur contact region), respectively, in air under dry conditions. Furthermore, the tibia and femur contact regions showed the reduced elastic modulus (Er) ranging from 0.88 ± 0.01 GPa to 3.90 ± 0.11 GPa, whereas the exocuticle regions showed the Er ranging from 0.27 ± 0.01 GPa to 1.27 ± 0.07 GPa, as much as two times higher. Overall, this study can be valuable to the development of the innovative lubrication systems, energy efficient materials, and durable materials through the bioinspiration. We believe that our work will bring motivation to designing next generation tribological materials for the practical applications in the near future.
3:45 PM - NM6.2.05
Bio-Inspired Single-Walled Carbon Nanotubes as a Spider Silk Structure for Ultra-High Mechanical Property
Chengzhi Luo 1 , Chunxu Pan 1
1 School of Physics and Technology, Wuhan University, Wuhan China
Show AbstractDue to their high tensile strength and exceptional electron mobility, single-walled carbon nanotubes (SWCNTs) have been considered as a desired reinforcement in polymer composites for improving mechanical and electrical properties. To integrate the remarkable nanoscale property of SWCNTs into macroscopic composites, several challenges must be overcome, such as achieving a high degree of SWCNT alignment, optimizing the interactions between neighboring SWCNTs, and maximizing the interactions between SWCNTs and polymer matrix.
It is well-known that the natural spider silk features exceptional mechanical property due to its constituent molecules and the hierarchical assembly into silk. In this work, we imitate a unique structure of natural spider silk and directly prepare a kind of the bio-inspired spider silk single-walled carbon nanotube (BISS-SWCNT) film. The BISS-SWCNT film is composed of pure SWCNTs as skeleton, embedded Fe nanoparticles and a amorphous carbon layer. The carbon layer not only form the spider silk featured “skin-core” structure with SWCNTs, but also make the tube junction tougher. The embedded Fe nanoparticles act as glue spots of the spider silk that prevent interfacial slippages between the BISS-SWCNTs and reinforced matrix. With only 2.1 wt% BISS-SWCNTs adding, the tensile strength and Young’s modulus of the BISS-SWCNTs/PMMA composites have been improved by 300%. More importantly, the BISS-SWCNTs also retain the high conductivity and transmittance of pristine SWCNT film. This unique bio-inspired material will be of great importance in applications of multi-functional composite materials, and has important implications for the future of biomimetic materials.
NM6.3: Porous Metal Composites
Session Chairs
Tuesday PM, April 18, 2017
PCC West, 100 Level, Room 106 C
4:30 PM - *NM6.3.01
Mechanically Robust Nanocomposites via Liquid Metal Dealloying
Jonah Erlebacher 1 , Bernard Gaskey 1
1 , Johns Hopkins University, Baltimore, Maryland, United States
Show AbstractDealloying is a materials processing method whereby one component is dissolved out of a multi-component alloy under conditions where the remaining components reorganize into a tortured yet beautiful porous microstructure. Recently, we have helped extend our knowledge of fundamental dealloying mechanisms to predict and then discover a new class of nanocomposite metals based on dealloying Ti-refractory alloys in molten metals, a process known as "liquid metal dealloying", or, LMD. In molten copper, Ti is dealloyed from the alloy, leaving behind a porous refractory that is cooled to form a dense metal-metal composite. These composites have remarkable mechanical properties such as good ductility and high strength that increases with decreasing feature size and we envision applications for these new materials in extreme environments where a significant fraction of internal interfaces is a critical materials design parameter. An important challenge in LMD microstructures is the engineering of grain boundaries to enhance mechanical robustness and ductility. Here we discuss the addtion of a ternary component to the base Ti-alloy such that this addition precipitates out during LMD, enhancing properties of the composite.
5:00 PM - NM6.3.02
Nanomechanics and Testing of Core-Shell Composite Ligaments for High Strength, Light Weight Foams
David Bahr 1 , Raheleh Mohammad Rahimi 1 , Aiganym Yermembetova 1 , Chang-Eun Kim 1 , Jack Skinner 2 , Jessica Andriolo 2 , John Murphy 2
1 , Purdue University, West Lafayette, Indiana, United States, 2 , Montana Tech, Butte, Montana, United States
Show AbstractComposite nanostructured foams consisting of a metallic shell deposited on a polymeric core were formed by plating copper via electroless deposition on electrospun polycaprolactone (PCL) fiber mats. The final structure consisted of 500-nm scale PCL fibers coated with 100’s of nm of copper, leading to final core-shell thicknesses on the order of 1000 nm. The resulting open cell, core-shell foams had relative densities between 4 and 15%. Structure were analysed using electron microscopy, and mechanical properties were evaluated using flat punch nanoindentation. By controlling the composition of the adjuncts in the plating bath, particular the composition of formaldehyde, allowed for control of the relative thickness of copper coating as the fiber diameter was increased. The layer thickness and uniformity were improved using longer processing times and higher temperatures during copper deposition, particularly leading to more complete deposition within the thickness of the mat. As-spun PCL mats had a nominal modulus in compression on the order of 0.1 MPa; adding a metallic shell increased modulus up to 2 MPa for sub-10% relative density foams. A computational materials science analysis using density functional theory was used to explore the effects bath chemistry had on the density of nuclei formed during electroless plating.
5:15 PM - NM6.3.03
Mechanical Properties of Ligand Free Nanocrystal Superlattices
Santosh Shaw 1 , Julien Colaux 2 , Jennifer Hay 3 , Frank Peiris 4 , Ludovico Cademartiri 1
1 , Iowa State University, Ames, Iowa, United States, 2 , University of Namur, Namur Belgium, 3 , Nanomechanics, Oak Ridge, Tennessee, United States, 4 , Kenyon College, Gambier, Ohio, United States
Show AbstractWe report an approach to produce nanostructured polycrystals in the form of films by first crystallizing the “grains” first as ligand-capped nanocrystals synthesized in solution as colloids, then depositing them by self-assembly, and finally removing the ligands by plasma processing (i.e., “nanocrystal plasma polymerization”, NPP). Since this approach bypasses stochastic bulk nucleation, it can form polycrystals with uniform, nanoscale grain sizes, but the evolution of the structure, composition, and cohesiveness of the films during the removal of the ligands is unclear.
We will describe the structural, chemical, and mechanical evolution of films of colloidal nanoparticles upon exposure to an O2 plasma (500 mTorr, 7 W, 6 h to 168 h of exposure). The plasma removes the alkyl tails of the ligands over the course of several hours (carbon concentration is 1.3 ± 0.5 at. % after 168 hrs). Before finally settling into an all-inorganic polycrystal, the arrays go through an intermediate, highly porous state (~0.5 void fraction) where the particles are joined by necks of ligand molecules. This highly porous state obtained after ligand removal result in high surface area materials with 100% crystallinity, good mechanical properties, and bare inorganic surfaces that could be very attractive for any application involving interface processes (e.g., energy storage, photovoltaics, catalysis) and the study of these processes as a function of material structure.
Characterization of the mechanical properties through nanoindentation and the analysis through the mechanical model of Kendall et al. indicate that the nanocrystal superlattices behave as granular matter before processing as well as after the complete removal of the ligands, but with radically different moduli and hardnesses (modulus, E: 2.2 ± 0.3 vs 44.5 ± 2.6 GPa; hardness, H: 0.1 ± 0.02 vs 2.2 ± 0.1 GPa). The highly porous intermediate state (≈0.5 void fraction), where the particles are joined by necks of ligand molecules, displays nongranular behavior with approximately four times the strength of a comparable granular system of same porosity.
We'll further report the evolution of mechanical properties that result from sintering.
References:
Nanocrystals as Precursors for Flexible Functional Films
L. Cademartiri*, G. von Freymann, A. C. Arsenault, J. Bertolotti, D. S. Wiersma, V. Kitaev, G. A. Ozin*
Small 2005, 1 (12), 1184-1187
Building Materials from Colloidal Nanocrystal Arrays: Preventing Crack Formation During Ligand Removal by Controlling Structure and Solvation
S. Shaw, B. Yuan, X. Tian, K. J. Miller, B. M. Cote, J. L. Colaux, A. Migliori, M. G. Panthani, L. Cademartiri*
Advanced Materials, DOI: 10.1002/adma.201601872
Evolution of the Structure, Composition, and Mechanical Properties of Colloidal Nanocrystal Films Upon Removal of Ligands by O2 Plasma (communication)
Santosh Shaw, Julien L. Colaux, Jennifer L. Hay, Frank C. Peiris, Ludovico Cademartiri*
Advanced Materials, DOI: 10.1002/adma.201601873
5:30 PM - NM6.3.04
Micromechanical Compressive Behavior of Freestanding and Ceramic-Composite 3D Graphene Foams
Kenichi Nakanishi 1 , Adrianus Aria 1 , Matthew Berwind 2 , Christoph Eberl 2 , Stephan Hofmann 1
1 , University of Cambridge, Cambridge United Kingdom, 2 , Fraunhofer Institute for Mechanics of Materials, Freiburg Germany
Show AbstractTwo-dimensional (2D) materials, such as graphene, offer new and improved functionalities for a wide range of applications ranging from electronics and photonics to energy conversion and storage devices. However, their route to applications is often limited by their inherent planar nature. Several attempts have thus been made to synthesize graphene network in 3D form to further extend their potential applications, particularly as ultra-lightweight structures. Early attempts to synthesize graphene foams, the archetypical 3D graphene networks, involved the use of polymer scaffolds, hence the micromechanical characterization is thus far limited to polymer-composite graphene foams. Here we present a detailed study of synthesis routes for freestanding and conformal ceramic-composite graphene foams. By optimizing the CVD and ALD growth parameters, we show that we can fabricate high quality freestanding and ceramic-composite graphene foams with ultralow density similar to graphitic aerogels [1]. We have successfully used this new understanding to elucidate the micromechanical response of both structures under compressive loads and how it differs from that of polymer-composite graphene foams [2]. We show that the ceramic-composite graphene foams offer a superior compressive efficiency compared to the polymer-composite ones. The coupling of strength and elastic modulus to density along with failure mechanisms were further examined for these structures, targeting a holistic understanding of their mechanical behavior. We also discuss the relevance of these results to future device integration and the possible optimization of composite and hierarchical graphene structures.
[1] Aria et al., ACS Applied Materials & Interfaces (2016)
[2] Aria et al, submitted (2016)
5:45 PM - NM6.3.05
Evolution of Geometrically-Self Similarity in Coarsened Nanoporous Gold
Hansol Jeon 1 , Ju-Young Kim 1
1 , UNIST (Ulsan National Institute of Science and Technology), Ulsan Korea (the Republic of)
Show AbstractNanoporous gold (np-Au) made by dealloying is composed of a bicontinuous network of ligaments (solid) and pores. This material has attracted attention in a variety of applications, such as catalysis, sensors, and actuators, due to its low weight and high specific surface area. Several studies of the mechanical properties of np-Au have shown that the Gibson-Ashby scaling equation for open foam materials cannot be applied directly to np-Au. Accurate scaling laws for np-Au are challenging to derive because of complex issues such as ligament size effect, tension-compression asymmetry, and geometric structure. The change in yield strength with ligament coarsening relies on ligament-size-dependent mechanical behavior (the smaller is the stronger) on the assumption that microstructures of np-Au are self-similar regardless of whether ligaments are coarsened. Few researchers have looked at the relationship between network structure and mechanical properties as well as microstructure of np-Au in terms of morphology, and topology. Thus, it is important to identify the microstructural change of np-Au as coarsening and effect of microstructure on mechanical properties. This study validates change in 3D microstructure of np-Au as coarsening and looks at the relationship between microstructure and mechanical behavior. We fabricated several np-Au samples with various ligament sizes from 60 nm to 1 um, using thermal coarsening at different temperatures and studied the 3D np-Au structures by FIB/SEM tomography so as to look at whether or not np-Au structures are self-similar during structure coarsening. Furthermore, we investigated correlation of microstructure with mechanical behavior by nano-indentation testing and finite element method (FEM) compression simulation. We show that the number of well-connected ligaments that can serve as load-bearing in supporting an applied force affects np-Au mechanical behavior.
NM6.4: Poster Session I: Mechanical Behavior of Nanostructure Composites
Session Chairs
Wednesday AM, April 19, 2017
Sheraton, Third Level, Phoenix Ballroom
9:00 PM - NM6.4.01
Atomistic Simulation of Scratch Behavior of Ceramic/Metal Nanolaminates
Iman Salehinia 1 , Adnan Rasheed 1
1 , Northern Illinois University, DeKalb, Illinois, United States
Show AbstractCeramic/Metal nano-laminates are attracting many researchers owing to their improved mechanical and tribological properties. The idea of ceramic/metal nano-laminates was born from the objective of combining the superior properties of ceramics such as hardness, strength, and chemical resistivity with the favorable properties of metals such as ductility. A material with such characteristics can be used as a protective coating in several applications. This study focuses on the scratch behavior of ceramic/metal nanolaminates. Molecular dynamics atomistic simulations were performed on the scratch behavior of different models of niobium carbide (NbC)-niobium (Nb) quad-layer models using the 2nd neighbor modified embedded atom potential. Looking for the improved design of NbC/Nb nanolaminates, the models were differentiated by varying the layer thicknesses of Niobium and Niobium Carbide. The coefficient of friction was calculated at different depths of indentation by a spherical indenter. The effect of the interface characteristics on the scratch behavior of the model material was investigated. MD simulations have shown the existence of various coherent and incoherent regions on the NbC/Nb interface, including localized and extended nodes, and misfit dislocations. The dominant deformation mechanisms for various scratch depths were also studied. Temperature is known to have a profound effect on the mechanical properties of materials. So the effect of temperature on the scratch behavior was also studied. The results demonstrate how the change in the layer thickness of metal and ceramic along with the indentation depth affect the frictional coefficient of the model material.
9:00 PM - NM6.4.02
A Continuum Model of Deformation in Metals Coated with Nanolaminate Metallic System for Applications in High Energy Environments
Mohammed Anazi 1 , Hussein Zbib 1
1 , Washington State University, Pullman, Washington, United States
Show AbstractThis research aims to develop, and implement into a finite element code, a continuum model of deformation and damage in metals coated with nanolaminate metallic systems (NMS) for potential applications in high-energy environments. The model will be developed based on continuum mechanics within the elastic/viscoplastic framework, which are presented by constitutive equations that include, dislocation density, size effect, strain hardening, strain rate effect, and damage, as well as a set of evolution laws for damage and dislocation density. The aim of the model is to investigate the deformation behavior and strength in such materials, and to provide a predictive capability for designing engineering structures from such materials. Specifically, the model will be utilized to investigate the mechanical behavior of an API X70 steel pipe coated with NMS for applications in high-energy environments, such as high internal pressure. The model will be implemented into a user subroutine in LS-DYNA, which is based on the finite element method. Finally, a series of numerical investigations will be performed for various layer thickness, and geometries and will be compared with experimental data found in the literature.
9:00 PM - NM6.4.03
On Structure and Mechanical Properties of Friction Stir Welded AA5083 Nanocomposite Plates Produced by a Novel Two-Step Ultrasonic Casting Technique
Vishwanatha Hire Math 1 , Jayakumar Eravelly 1 , Sudipto Ghosh 1 , Cheruvu Siva Kumar 1 , Nisith R Mandal 1
1 , IIT Kharagpur, Kharagpur India
Show AbstractAA5083 is a widely accepted marine grade alloy because of its good formability and weldability especially in ship-building. The increasing use of AA5083 creates the need for enhancing the high strength to weight ratio property. During the last four decades, Aluminium matrix nanocomposites have gained great research attention as attractive materials for potential industrial applications. Ultrasonic casting has become a promising method for producing nanocomposites. Welding of nanocomposites is an important topic to be considered especially in the ship-building. The present work aims at characterizing the microstructure and mechanical properties of the friction stir welded hot rolled AA5083-1wt-%Al2O3 bulk nanocomposite plates produced by a novel Two-Step ultrasonic casting technique. This is a comparative study between friction stir welded AA5083 nanocomposite plates and AA5083 alloy plates. A definite enhancement was achieved in the mechanical properties of the nanocomposite and the friction stir welded joint. The enhancement in the microhardness of the nanocomposite is about 20%. Interestingly, the decrease in the hardness along the advancing side is lesser as compared to that of retreating side. The ultimate tensile strength of the welded nanocomposite is 30% higher than that of the welded alloy. The increase in the strength due to the dispersion of the nanoparticles did not result in the decrease of the ductility that was observed in the case of non-welded nanocomposite. Unprecedented uniform distribution of alumina particles is observed in the weld zone of the nanocomposite as compared to the non-weld zone. The relative hardness of weld zone with respect to non-weld zone was higher in case of welded AA5083 nanocomposite than in welded AA5083. A higher hardness ratio was achieved in the case of nanocomposite and the increase in the hardness was explained in terms of grain refinement due to enhanced dynamic recrystallization during welding.
9:00 PM - NM6.4.04
Evaluation of the In-Plane Size of Crystal within Nanometric Thin Layers by Non Coplanar Grazing Incidence X-Ray Diffraction
Ludovic Largeau 1 2 , Herve Montigaud 1 3 , Yann Cohin 3 , Edouard Villepreux 1 3
1 , CNRS, Marcoussis France, 2 , University Paris Saclay, Palaiseau France, 3 , Saint-Gobain, Aubervilliers France
Show AbstractFunctional glazings for many applications such as insulating windows present stack of thin layers onto the surface of the glass. These stacks have to combine high visible transparency with an optimized reflectance in the far-infrared wavelength. The low-emissivity property is mainly obtained by a thin layer of silver that the thickness range is around 10nm. It is embedded in other layers to enhance its crystallinity, to protect the metal and to adjust the optical properties. These thin layers stacks are deposited by PVD magnetron sputtering on flat glass substrates at ambient temperature.
The performance of this metallic layer is related to its conductivity. Its crystallinity and its microstructure are thus key parameters because the grain boundary scattering is one of the most predominant phenomenon which influences the electrons mobility [1].
In order to study the structural properties and more precisely to estimate the lateral size of such nanocrystallized coatings, we have developed a nondestructive route using laboratory non-coplanar grazing incidence X-ray Diffraction (GIXRD). Experiments have been carried out with a Smartlab Rigaku diffractometer equipped with a rotating anode and a 5-axis goniometer dedicated for in-plane diffraction. This non-coplanar diffraction allows to determine directly the grain size through the directions parallel to the substrate plan using an adapted Scherrer approach. The texture of the films is deduced by comparing the contribution of {111} and {220} planes to the in-plane diffraction.
By means of this original approach for the characterization of silver layer of low-E stack, we studied the impact of the Ag thickness and the influence of the nature of the underlayer such as a crystallized ZnO. Indeed, Zinc oxide obtained by this PVD technique exhibits a wurtzite structure with (002) perpendicular to the surface plan. Such textured ZnO underlayer promotes the growth of (111) silver crystals.
Non coplanar GIXRD study confirms this expected Ag texture and it shows that the Ag crystal lateral sizes increase with the layer thickness. Non coplanar GIXRD results were also compared with those obtained by AFM and Transmission Electron Microscopy.
[1] Martin Philipp, UPMC, PHD (2011)
9:00 PM - NM6.4.05
Physical and Mechanical Properties of Luminescent Silicon Nanocrystal Layers on PDMS
Alborz Izadi 1 , Yuheng Wang 1 , Mayank Sinha 1 , Sara Roccabianca 1 , Rebecca Anthony 1
1 , Michigan State University, East Lansing, Michigan, United States
Show AbstractFlexible and stretchable electronic and opto-electronic devices have numerous applications including light-emitting devices, solar photovoltaics sensors, health monitoring devices and communication technologies. However, to date there are few to no studies on the mechanical behavior of Nanocrystal (NC) films on stretchable substrates. Here we used experimental and theoretical techniques to explore the physical, optical, and mechanical properties of luminescent silicon NC (SiNC) layers deposited directly from a nonthermal plasma reactor directly onto polydimethylsiloxane (PDMS) substrates. Plasma reactors have been well-studied for synthesis of high-quality SiNCs, and also offer the opportunity to deposit NCs directly onto substrates from the vapor-phase via inertial impaction. This process occurs in complete avoidance of high-temperature or solvent processes, enabling facile deposition of NCs onto the PDMS without risking damage to the polymer. We found that the SiNC film porosity is affected by the stiffness of the substrate, as measured using spectroscopic ellipsometry and scanning electron microscopy. We found that lower SiNC layer porosities occurred for substrates with lower stiffness. In addition, we applied prestrain to the PDMS prior to SiNC deposition, initiating instabilities in the SiNC/PDMS layers. From there, we measured the mechanical properties of the SiNC+PDMS system as a whole and linked those properties to the physical properties of the instabilities in the SiNC/PDMS system.
9:00 PM - NM6.4.06
Mechanical Properties of Hard/Soft Copolymers Calculated by Coarse-Grained MD Simulations
Min Zhang 2 , Zhiwei Cui 1 , L. Catherine Brinson 3
2 Mechanical Engineering, Northwestern University, Evanston, Illinois, United States, 1 , General Motors, Detroit, Michigan, United States, 3 Mechanical Engineering, Material Science Engineering, Northwestern University, Evanston, Illinois, United States
Show AbstractElastomers like polyureas and polyurethanes have attracted increasing attention in structural systems subjected to impact loading since they possess low wave speeds, acoustic impedances and good dissipative properties. The microstructure of polyurea is typically characterized with a two-phase composition of hard and soft segments. The hard segments formed by hydrogen bonding of the urea-linkage tend to aggregate into larger domains (hard domains) which could increase the overall polymer strength due to its high glass transition temperature. At the same time, the soft chain segments consist of more flexible polyol chains and act as a flexible continuous matrix for the network of hard domains.
A coarse-grained molecular dynamic approach is employed to study the mechanical properties for this hard-soft block copolymers at various temperatures. We investigate the enhancement mechanism of such polymers by relating their microstructures with mechanical responses under tension and shear with pressure. The energy factor that denotes the interaction between hard beads dominate the micro-phase separation and morphology of hard domains, however, its effect is coupled with the volume fraction of hard beads when mechanical response is considered. Our numerical experiments also show that pressure is a crucial factor and larger pressure leads to higher shearing resistance of the copolymers.
The viscoelastic behaviors of those copolymers are also investigated. The time-dependent shear modulus is computed from the stress autocorrelation function (SACF), and fitted with the Prony series expansion using a two-step optimization method. Therefore, the storage and the loss modulus are computed in frequency domain. It clearly demonstrates that soft matrix are at rubbery state at room temperature and hard domains are more “crystalline-like” and can be viewed as elastic solids in a macroscale model.
Local elastic constants of hard domains in the studied copolymers are computed using the stress-strain fluctuation method. Local stress is calculated for each hard bead while the local strain is determined by minimizing the mean-square difference between the actual displacements of the neighboring molecules relative to the central one and the relative displacements that they would have if they were in a region of that local strain. As a comparison, elastic constants for the whole copolymers are also calculated. Poisson’s ratio are close to 0.5 for pure soft matrix and copolymers with smaller composition of hard beads and energy factors but are around 0.3 for hard domains with stronger interactions between hard beads. Both shear modulus and Young’s modulus are gradually increasing with VF and energy factors. The results can be used to help build macroscale models for copolymers and are able to provide guidelines for designing polymeric materials.
9:00 PM - NM6.4.08
Self-Dispersed Crumpled Graphene Balls in Oil for Friction and Wear Reduction
Xuan Dou 1 , Jiaxing Huang 1
1 , Northwestern University, Evanston, Illinois, United States
Show AbstractUltrafine particles are often used as lubricant additives because they are capable of entering tribological contacts to reduce friction and protect surfaces from wear. They tend to be more stable than molecular additives under high thermal and mechanical stresses during rubbing. It is highly desirable for these particles to remain well dispersed in oil without relying on molecular ligands. Borrowing from the analogy that pieces of paper that are crumpled do not readily stick to each other (unlike flat sheets), we expect that ultrafine particles resembling miniaturized crumpled paper balls should self-disperse in oil and could act like nanoscale ball bearings to reduce friction and wear. Here we report the use of crumpled graphene balls as a high-performance additive that can significantly improve the lubrication properties of polyalphaolefin base oil. The tribological performance of crumpled graphene balls is only weakly dependent on their concentration in oil and readily exceeds that of other carbon additives such as graphite, reduced graphene oxide, and carbon black. Notably, polyalphaolefin base oil with only 0.01–0.1 wt % of crumpled graphene balls outperforms a fully formulated commercial lubricant in terms of friction and wear reduction.
9:00 PM - NM6.4.09
Is Measured Strength Dependent on Anvil Hardness?
Lucy Morgan 1 , Dean Sayle 1
1 , University of Kent, Canterbury United Kingdom
Show AbstractWe predict, using MD simulation, that fracture strength and plastic deformation of a nanomaterial may occur at a much lower stress than currently reported. Such finding is pivotal to the predicted lifespan of nanomaterials under operational conditions, which may include: vibration, friction, and wear. In particular, we find that assuming a static, rather than dynamic, surface area may lead to the over-reporting of strength because the surface area of the material will increase as it deforms under imposed stress. In addition, anvils, used to communicate pressure upon a test material, will likely deform themselves under pressure; a ‘soft’ anvil, such as a metal [1], will likely suffer greater deformation than a ‘hard’ anvil, such as diamond [2]. Here, we calculate that the mechanical strength of nanoceria is 12 GPa using a ‘soft’ anvil but 18 GPa using a ‘hard’ anvil - an increase of 50%. This is because the soft anvil absorbs more of the imposed stress resulting in a lower stress-strain gradient.
In summary, we show how MD simulation can help experiment gain better insight into the mechanical properties of nanomaterials to help predict more accurate operational lifespans.
[1] Miyoshi, K.; Buckley, D.H. A S L E Transactions, 1984, 27(1), 15-23.
[2] Eremets, M. I.; Trojan, I. A.; Gwaze, P.; Huth, J.; Boehler, R.; Blank, V. D. Appl. Phys. Lett, 2005, 87, 141902-150.
9:00 PM - NM6.4.11
Physicochemical and Mechanical Properties of Biomimetic Nanostructured Composite Materials
Susana Alonso-Sierra 1 , Beatriz Millan-Malo 2 , Rodrigo Velazquez Castillo 1 , Eric Rivera Munoz 2
1 , Universidad Autonoma de Queretaro, Querétaro Mexico, 2 , Universidad Nacional Autonoma de Mexico, Queretaro, Queretaro, Mexico
Show AbstractDue to the fact that bone tissue consists of 70% (wt%) of inorganic phase (composed mainly by hydroxyapatite, Ca10(PO4)6(OH)2) and around 22% of organic phase, research to develop bone tissue substitutes has been focused on the obtaining of hydroxyapatite-based composite materials reinforced with polymers. In this work we report the synthesis of composite material using three different types of hydroxyapatite, one extracted from bovine bone, a commercial one and another synthesized by hydrothermal microwave-assisted method which produces hydroxyapatite nanofibers with crystalline preferential orientation. Modified Gel-Casting Process was used to molding ceramic scaffolds with interconnected micro and macroporosity. Subsequently, two different organic phases (obtained from natural sources) were added to the ceramics scaffolds, thus obtaining polymeric-ceramic composite material with physicochemical, structural and mechanical properties similar to those on natural bone tissue.
The composite materials were characterized by Scanning Electron Microscope (SEM) techniques, powder X-ray Diffraction (XRD) and Fourier Transform Infrared Spectrometry (FT-IR). Compression tests were carried out to characterize mechanical properties of final composite materials and to compare similarities and differences between the use of powdered and nanostructured hydroxyapatite in the mechanical performance. Finally, the relationship between the various parameters used and the mechanical behavior of the nanostructured composite materials is established.
9:00 PM - NM6.4.12
Modification of Nafion Fuel Cell Membrane with Sulfonated Graphene Oxide and Ceria
In Sung Jeon 1 , Han-Seung Ko 1 , Eunsuk Jeong 1 , Dongchan Seo 1 , Ikseong Jeon 1 , Jae Young Jho 1
1 , Seoul National University, Seoul Korea (the Republic of)
Show AbstractTo strengthen Nafion membrane for proton exchange fuel cell, reinforcement like graphene has been added. To extend the operating stability of the membrane and the device, radical scavenger like ceria was also employed. To enhance the strength and stability at the same time, reinforcement and stabilizer were added together. Sulfonated graphene oxide (SGO) and ceria nanoparticle were selected, respectively. SGO with higher concentration of sulfonic acid groups (hydrophilic) on the surface was expected to prevent deterioration in proton conductivities. The result showed an increase of 50% in Young’s modulus and 5% in tensile strength at 2 wt% of SGO and 1 phr of ceria. Both through-plane and in-plane were calculated based on the proton conductivity determined by impedance analyzer under the condition of RH 50 and RH 100 at 80 °C. The result showed higher conductivity and water uptake for SGO/ceria/Nafion composite membrane than GO/Nafion composite membrane. The chemical durability of the composite membrane appeared much enhanced by showing large reduction in the weight loss upon the exposure to Fenton’s reagent solution.
9:00 PM - NM6.4.13
Mechanical Properties and Bioactivity of Polyetheretherketone Modified with Graphene, Carbon Fiber, and Hydroxyapatite
Han-Seung Ko 1 , In Sung Jeon 1 , Jae Young Jho 1
1 , Seoul National University, Seoul, SE, Korea (the Republic of)
Show AbstractPolyetheretherketone (PEEK), a semi-crystalline super engineering plastic, has been a prime choice for orthopedic implant material due to its modulus and strength comparable to human bone. As the mechanical properties can be fine-tuned for specific application, reinforcing materials like carbon fiber have been added. Although PEEK is chemically and biologically inert by itself, materials like hydroxyapatite also have been added to enhance its bioactivity. In this study, graphene, carbon fiber, and hydroxyapatite were added to apply the composite as the material for spinal fusion. By using combinations of the additives for modification, the effect of choice and composition on the properties was investigated. Mechanical properties critical in spinal fusion application like modulus and compressive strength were measured, and tuned to match the required figures. Bioactivity of the composites was characterized by apatite formation on the surface of the composites immersed in simulated body fluid solution. Morphology of the composites was also examined.
Symposium Organizers
Seung Min Han, Korea Advanced Institute of Science and Technology (KAIST)
Arief Budiman, Singapore University of Technology and Design
Amit Misra, University of Michigan–Ann Arbor
Ruth Schwaiger, Karlsruhe Institute of Technology
NM6.5: Nanolayered Composites
Session Chairs
Amit Misra
Guang-Ping Zhang
Wednesday AM, April 19, 2017
PCC West, 100 Level, Room 106 C
9:30 AM - *NM6.5.01
Averting Flow Localization in Metal Nanocomposites by Tailoring Microstructure Morphology
Ian McCue 1 , Kumar Ankit 1 , Michael Demkowicz 1
1 , Texas A&M University, College Station, Texas, United States
Show AbstractMetal nanocomposites present significant advantages over conventional bulk metals, such as high uniaxial strength, fatigue and radiation resistance, and high strength-to-weight ratio. However, an impediment to their widespread technological application is that they often fail suddenly and with minimal uniform plastic deformation due to flow localization. I will describe an effort to create metal nanocomposites that resist flow localization by engineering the morphology of their microstructure. Our work builds on recent advances in the synthesis of bulk metal nanocomposites via liquid metal dealloying. By varying the compositions, initial structures, and processing histories of these materials, we generate a range of complex nanocomposite morphologies. We then investigate the effect of morphology on flow localization. By averting flow localization, we aim to impart to NMMs the ability to undergo large-scale, uniform plastic deformation, markedly advancing their potential for use in structural and functional applications.
10:00 AM - *NM6.5.02
High Temperature Deformation Behavior, X-Ray Nanotomography and Modeling of Al/SiC Nanolaminates
Carl Mayer 1 , Ling Wei Yang 2 , Saeid Lotfian 2 , Hrishikesh Bale 3 , C. Shashank Kaira 1 , John K. Baldwin 4 , Nan Li 4 , Nathan Mara 4 , Arno Merkle 3 , Jon Molina-Aldareguia 2 , Nik Chawla 1
1 , Arizona State University, Tempe, Arizona, United States, 2 , IMDEA, Madrid Spain, 3 , Carl Zeiss, Pleasanton, California, United States, 4 , Los Alamos National Laboratory, Albuquerque, New Mexico, United States
Show AbstractNanolaminate Al/SiC composites exhibit extremely high strength and toughness. In this talk we discuss the high temperature nanoindentation and micropillar compression behavior of these materials. The nanolaminates were processed by physical vapor deposition (PVD) using magnetron sputtering. Layer thickness and morphology was studied using a dual beam focused ion beam (FIB). The mechanical properties were characterized by high temperature nanoindentation at 100, 200, and 300oC. Post-deformation microstructural analysis was carried by FIB, in situ transmission electron microscopy (TEM) and atomic force microscopy (AFM) to provide insight into the deformation mechanisms. In situ nanotomography of micropillar compression of the nanolaminates, at ambient temperature, elucidated the evolution of damage and interplay between fracture of SiC and flow of the Al layers. Finite element simulations of the effect of interface strength on sliding and flow of the aluminum layers, during micropillar compression, will be described and discussed.
10:30 AM - NM6.5.03
Laser Treatment of Fe-Si-B Metallic Glass—Microstructure Evolution and Tensile Behavior
Sameehan Joshi 1 , Shravana Katakam 1 , Iman Ghamarian 2 , Peyman Samimi 2 , Peter Collins 2 , Narendra Dahotre 1
1 Materials Science and Engineering, University of North Texas, Denton, Texas, United States, 2 Materials Science and Engineering, Iowa State University, Ames, Iowa, United States
Show AbstractFe-Si-B metallic glass foils were subjected to a single linear laser track treatment using a continuous wave Nd:YAG laser. The input laser power was kept constant and laser beam scanning speeds were varied to have various laser fluences at the metallic glass sample surface. Microstructure attributes namely structural relaxation and crystallization were primarily investigated using X-ray diffraction and electrical resistivity measurements. Furthermore, transmission electron microscopy shed a light on the nature of crystallization, grain size, and phases evolved as a result of crystallization. Quantification of fraction of crystallized phases was done with the aid of differential scanning calorimetry. Tensile behavior of the laser treated metallic glass foils was evaluated using hydraulically driven Instron universal testing machine. Metallic glass foils treated with laser fluences lower than 0.49 J/mm2 underwent structural relaxation. On the other hand, laser treatment with higher laser fluences (>0.49 J/mm2) led to partial crystallization of these foils. Structural relaxation had a minimal influence on the tensile behavior of laser treated Fe-Si-B metallic glass. However, higher fractions of crystallization and evolution of hard intermetallic phase for higher laser fluence processing conditions severely reduced the strength of laser treated Fe-Si-B metallic glass. Furthermore, the fracture surfaces of representative samples including as cast, laser treated and structurally relaxed, and laser treated and partially crystallized samples were investigated using scanning electron microscopy and site specific transmission electron microscopy. The fractograph observations were coupled with effects of stress and temperature during the process of fracture to get an insight into tensile fracture behavior of laser treated Fe-Si-B metallic glass.
11:15 AM - *NM6.5.04
Understanding Interface Effects on Mechanical Behavior of Metallic Nanolayered Composites
Guang-Ping Zhang 1
1 , Institute of Metal Research, Chinese Academy of Sciences, Shenyang China
Show AbstractMetallic nanolayered composites made of two alternating metal layers with different interface structures and/or moduli can have strength up to about 1/3–1/2 of the theoretical strength as the individual layer thickness of the composites decreases from the micrometer scale to the nanometer scale. At such length scale, a heterogeneous layer interface not only dominates the resistance to dislocations transmission, leading to the peak strength, but also controls plastic deformation behavior of the nanocomposite through the complicated interaction between defects and interfaces. Thus, it is necessary to fully understand effects of the interface on mechanical behavior of the nanolayered composites. In this talk, we will present experimental and theoretical investigations of mechanical behavior of a few of metallic nanolayered composites, emphasizing effects of interface properties and structures. Three aspects will be focused. The first one is about atomic-scale chemical modulation for the resistance to dislocation crossing interface. The second one discusses effects of the interface on plastic deformation and fracture behavior of bi-constituent and tri-constituent nanolayered composites. The third one concentrates on the interface role in damage evolution of the nanolayered composites subjected to cyclic loading. A detailed analysis for the interface effects on mechanical behaviors will be given. It is expected that the findings may provide a potential clue to tailor heterogeneous interface properties for high performance nanolayered composites.
11:45 AM - *NM6.5.05
Microstructure and Mechanical Behavior of Bulk Nanolaminate Composites Produced by Accumulative Roll Bonding
Nathan Mara 1 , D.J. Savage 2 , J. Weaver 1 , John Carpenter 1 , Rodney McCabe 1 , Thomas Nizolek 3 , Tresa Pollock 3 , Nan Li 1 , Sven Vogel 1 , Marko Knezevic 2 , I.J. Beyerlein 1 3
1 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 2 Department of Mechanical Engineering, University of New Hampshire, Durham, New Hampshire, United States, 3 Department of Materials Science, University of California Santa Barbara, Santa Barbara, California, United States
Show AbstractTwo-phase nanolaminate thin film composites have demonstrated an unusually broad number of desirable properties, such as high strength, high strain to failure, thermal stability, and resistance to light-ion radiation. Recently we have shown that bi-phase HCP/BCC nanolaminates with individual layer thicknesses approaching 10 nm can be made via severe plastic deformation (SPD) in bulk sizes suitable for structural applications. Mechanical testing of these HCP/BCC nanolaminates shows exceptionally high strength and characterization via a suite of techniques including neutron diffraction, EBSD, and TEM indicates that the crystals are highly oriented. While the cause of these unusual properties can easily be associated with a high density of bimetal interfaces, how the interfaces physically control microstructural evolution and macroscopic properties remains an area of intense research. We will present these new results, and place them in the larger context of interface structure-property relationships of bulk nanocomposites. This presentation highlights our modeling and experimental efforts to understand and link the evolution of the nanostructure, the interface properties, and preferred texture during the SPD process.
12:15 PM - NM6.5.06
In Situ SEM Observation of Crack Growth in Metal-Metal Nanolayered Composites during Clamped Beam Bending
Ihor Radchenko 1 , Hashina Parveen Anwar Ali 1 , Qing Liu 2 , Arief Budiman 1
1 , Singapore University of Technology and Design, Singapore Singapore, 2 MSE, Nanyang Technological University, Singapore Singapore
Show AbstractDepending on layer thickness and interface structure, various deformation mechanisms may be present in metal-metal nanolayered composites (NC). The deformation mechanisms can largely affect its fracture behavior. Therefore, the fracture of NC may be dependent on its dimensionality and interface type. For the case of NC having incoherent interface, when the crystal structure is changing significantly across the interface, not much fracture data is present the literature. There are studies showing influence of layer thickness on crack propagation in NC, but there is no data available about the effect of interface structure. In this study, we have investigated crack propagation across the layers of fcc-bcc nanolayered composites using in situ SEM observation. The fracture testing was conducted using clamped beam bending geometry. If was found that crack propagation may be significantly different depending on interface structure and distance from sample surface. Various types of deformation mechanisms were observed - confined layer slip, interface crossing of single dislocation and interface shear. Moreover, few mechanisms may be present in NC at the same time leading to crack deflection during fracture.
12:30 PM - NM6.5.07
Bending Fatigue Behavior of Cu/Graphene Nanolayered Composites
Wonsik Kim 1 , Byung il Hwang 1 , Seoyoen Lim 1 , Sangmin Kim 1 , Seung Min Han 1
1 Graduate School of Energy Environment Water and Sustainability, Korea Advanced Institute of Science & Technology, Daejeon Korea (the Republic of)
Show AbstractGraphene is an excellent strength enhancer in the form of a metal/graphene nanolayered composite. One of the promising applications of such metal/graphene nanolayered composite is in interconnects for flexible electronics that would require extreme mechanical properties in order to withstand cyclic deformations. Graphene interface was previously reported to block dislocation propagation in metal/graphene nanolayers to cause ultra-high strengths; however, the fatigue behavior in response to cyclic bending strains has yet been studied. In this work, the ability of graphene to enhance the fatigue response of Cu/graphene nanolayers by blocking the crack propagation was evaluated. Bending fatigue tests were performed for both the Cu/graphene composite and Cu thin film that showed significantly enhanced reliability for Cu/graphene compared to the Cu thin film. Cross sectional SEM and TEM images showed that the crack was greatly hindered by the graphene interface thus enhancing the bending fatigue properties in Cu/graphene nanolayers, whereas cracks were initiated in Cu thin films that propagate through thickness of the film. In addition, molecular dynamics simulations were conducted that also confirmed the ability of graphene layers in blocking the crack propagations across the Cu/Gr interfaces. In the case of using Cu/graphene as an interconnect, it is critical that the conduction pathway remains intact during cyclic bendings imposed by a flexible device. Our results indicate that the conductivity can be sustained up to high bending fatigue cycles for Cu/graphene nanolayers since any initiated cracks do not propagate through the whole thickness in Cu/Gr composites to allow for prolonged conduction pathway, thus making it suitable for interconnect material design. This study has, therefore, have shown that the Cu/graphene nanolayers have excellent bending fatigue resistance due to the effectiveness of the graphene interface in blocking crack formations through thickness of the whole film, and this fatigue resistance mechanism allows for prolonged lifetime when used as an interconnect of a flexible device.
12:45 PM - NM6.5.08
Mechanical Reliability of CVD Graphene-Covered Copper Nanocomposites
Bin Zhang 1 , Zhi-Xuan Guo 1 , Guang-Ping Zhang 2
1 School of Materials Science and Engineering, Northeastern University, Shenyang China, 2 , Institute of Metal Research, Chinese Academy of Sciences, Shenyang China
Show AbstractExcellent mechanical properties of graphene have made it attractive in extensive applications of nanodevices, functional/structural composites and coatings. In order to explore potential roles and multi-functionalities of graphene in modification of nano-mechanical properties of materials, in this presentation we will report an experimental investigation of mechanical performance of a nanocomposite made of a pure copper foil covered by graphene, which was prepared by chemical vapor deposition (CVD) methods. Basic mechanical properties of the graphene-covered Cu composite were firstly investigated using the nanoindentation technique. The elastic modulus, strength and plastic deformation behavior of the graphene-covered Cu composites were evaluated. Then, the fatigue performance including fatigue strength and cracking behavior of the graphene-covered Cu composites was investigated under tension-tension fatigue loading, and compared with that of the bare Cu foils. We found that the CVD-graphene could not only evidently enhance strength and modulus, but also modify the fatigue performance of the Cu foils. Furthermore, the graphene also affects the critical shear stress for the onset of initial plasticity and the plastic deformation recovery of the pure Cu. The detailed analysis is conducted to understand the effective roles of the CVD-graphene in modifying mechanical reliability of nanocomposites.
NM6.6: Simulation and Modeling of Nanocomposites
Session Chairs
Wednesday PM, April 19, 2017
PCC West, 100 Level, Room 106 C
2:30 PM - *NM6.6.01
Interface Engineering: Improve Mechanical Properties and Irradiation Tolerance of Materials by Tailoring Interfaces in Solids
Jian Wang 1
1 , University of Nebraska–Lincoln, Lincoln, Nebraska, United States
Show AbstractInterfaces are common planar defects in solids. Interface can act as barriers, sinks and sources for other defects. By tailoring interface structures and properties, materials can be designed to achieve unusual properties, such as high strength, good ductility, high toughness, and high irradiation tolerance. This can be accomplished through two steps: (1) Discover unusual mechanical behavior (e.g., high strength and good ductility) of nanostructured composites, and Develop theory and fundamental understanding of unusual mechanical behavior. (2) Transform fundamental understanding of structural characters and deformation physics of nanostructured composites into a mesoscale capability of discovering, predicting, and designing superior nanostructured materials (strength, ductility, toughness, radiation). To achieve this goal, multi-scale methods including experiment and theory and modeling are necessary. In this talk, I will present fundamental principles in developing interface-dominated composites, and the development of experimental techniques and materials modeling tools at different scales.
3:00 PM - NM6.6.02
Computational Approach for Designing Heteroepitaxial Metamaterials with Novel Properties
Yang Wang 1 , Samuel Reeve 1 , Alejandro Strachan 1
1 Materials Engineering, Purdue University, West Lafayette, Indiana, United States
Show AbstractWe use the concept of free energy landscape engineering to explore the design of nanostructured metamaterials with unprecedented properties. By calculating the free energy as a function of lattice parameter (free energy landscape) for individual metals and orientations and combining those landscapes in epitaxial metamaterials, a variety of unprecedented mechanical properties can be designed. Ultra-low and tunable stiffness, as well as martensitic behavior from non-martensitic components are made possible in theory. We perform density functional theory (DFT) simulations as a function of lattice parameters and use generalized polynomial chaos to obtain a library of analytical free energy landscapes for a wide range of face-centered cubic (FCC) and body-centered cubic (BCC) metals. We then study all possible combination of landscapes to find desired features in the metamaterials. Interestingly, combining Pd and V energy landscape along epitaxial Bain path shows a low curvature minimum indicating very low stiffness and explicit DFT calculations on the heterostructure confirm that the stiffness of in-plane directions is only 1/3 of out-plane direction, a level of anisotropic not achievable in any other metal.
3:15 PM - NM6.6.03
Mechanics-Driven Design of Crystalline-Amorphous Nanolaminate Composites
Bin Cheng 1 , Jason Trelewicz 1
1 , Stony Brook University, Stony Brook, New York, United States
Show AbstractCrystalline-amorphous composites represent a unique class of hierarchically structured materials that have expanded the strength-ductility envelope for nanostructured and amorphous metals. The mechanistic coupling of dislocation and shear transformation zone (STZ) plasticity provides an effective pathway for accommodating strain while circumventing the formation of deleterious grain boundary voids and primary shear bands. A number of previous studies have demonstrated that the mechanical behavior can be tuned by changing the length scales of nanolaminates, such as amorphous-to-crystalline layer thickness ratio (tA/tC) and nanocrystalline grain size. However, design principles for simultaneously optimizing the multiple inherent structural length scales to tune plasticity at the nanoscale have yet to be established. In this study, columnar nanocrystalline-amorphous nanolaminate composites were designed and used to study the deformation behavior via molecular dynamic simulations. The layer thickness ratio and nanocrystalline grain size were systematically varied, and the mechanical response of the composites were characterized under uniaxial tensile loading employing deformation metrics for atomistic simulations. Illustrative compound deformation mechanisms maps were generated for each length scale combination rooted in the contributions of the three dominant deformation mechanisms: grain boundary, dislocation, and STZ plasticity. Combined with deformation snapshots, the compound mechanism maps provided new insights into the mechanistic transitions in crystalline-amorphous nanolaminates as a function of their microstructural length scales, which have important implications for the resulting mechanical properties. The effective yield strength was determined by the nanocrystalline grain size while the flow stress was dictated by the tA/tC ratio. The latter also controlled the transition from shear band-dominated plasticity to the formation of grain boundary voids. From these observations, mixed-mode deformation regions were identified where coupling between the disparate mechanisms operating the crystalline and amorphous layers dominated the deformation behavior. The results were compiled into an Ashby plot from which four unique deformation zones were identified to establish new mechanics-driven design principles for optimizing the performance of crystalline-amorphous nanolaminate composites.
NM6.7: Polymer and Amorphous Metal-Based Composites
Session Chairs
Wednesday PM, April 19, 2017
PCC West, 100 Level, Room 106 C
4:30 PM - *NM6.7.01
Strong, Stiff and Hard Isotropic Iron Oxide Nanocomposites with Organic Matrix—The Role of Chemical Crosslinking, Filler Percolation and Geometrical Confinement
Gerold Schneider 1
1 , Hamburg University of Technology, Hamburg Germany
Show AbstractThe widely accepted mechanical concept of bioinspired load bearing nanocomposites is based on the idea to combine elongated strong and stiff nanoparticles with a soft organic damage tolerant matrix. This mechanical concept provides likewise hard, stiff and strong as well as damage tolerant nanocomposites, which overcome the weakness of one material class and achieve multi-functionality. Recently, we showed that an FCC-superstructure of self-assembled monodisperse spherical iron oxide nanoparticles with oleic acid shells heat treated at 350°C leads to a very hard, stiff and strong nanocomposite. This investigation demonstrated that globular nanoparticles with a very thin organic shell may also lead to excellent mechanical properties. Also nature uses this concept as nacre’s aragonite platelets are built from nanograins with organic sheaths. The objective of this work is to show that this is a general concept, applicable to other iron oxide nanocomposites with different ligands. Using a,w-polybutadiene dicarboxylic acid instead of oleic acid our experiments show that despite a reduced processing temperature, an approximately 10 times higher molar mass and a more than 2 times higher volume fraction of approximately 40% in comparison to the oleic acid nanocomposite, the a,w-polybutadiene dicarboxylic acid/iron oxide nanocomposites are also very hard, stiff and strong. We attribute this astonishing result to a catalytically enhanced crosslinking reaction of the a,w-polybutadiene dicarboxylic acid polymer chains induced by oxygen (from air) or by sulfur at 145 °C and the microstructure of the nanocomposite.
5:00 PM - *NM6.7.02
Laminar Bulk Metallic Glass/Metal Composites via Accumulative Roll Bonding
Sina Shahrezaei 1 , Irene Beyerlein 2 , Suveen Mathaudhu 1
1 , University of California, Riverside, Riverside, California, United States, 2 Materials Department, University of California, Santa Barbara, Santa Barbara, California, United States
Show AbstractMonolithic bulk metallic glasses (BMG) are known to have high strengths and hardness, however, they are inherently brittle, making them not desirable for structural applications wherein plastic deformation must be supported. Laminar composites of BMG and other ductile metals fabricated by deposition methods allow extraordinary mechanical performances including high ductility and strength, and unique dislocation activity in the amorphous/crystalline interface, however are limited in size and scalability. Here we demonstrate the scalable fabrication of laminar Zr-based BMG/Ni composites using accumulating roll bonding. The Mechanical behavior of these composites is evaluated using micro- and nanoindentation probes and mechanical tension tests. The resulting microstructures are evaluated using SEM and EBSD, while the composition at the bonding interface is analyzed using EDX. The effect of these novel interfaces on dislocation activity will be reported. The results forecast the design of a variety of BMG/crystalline metal composites for high performance structural materials.
5:30 PM - NM6.7.03
Ultra-High Elastic Strain Energy Storage in AlOx-Infiltrated SU-8 Photoresist Composites at Small Length Scales
Seok-Woo Lee 1 , Keith Dusoe 1 , Aaron Stein 2 , Chang-Yong Nam 2
1 Materials Science and Engineering, University of Connecticut, Storrs, Connecticut, United States, 2 Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York, United States
Show AbstractAn understanding of the mechanical properties of materials at the nanometer length scales, including a material’s ability to store and release elastic strain energy, is of great significance in the effective miniaturization of actuators, sensors and microelectronics for use in micro-electro-mechanical systems (MEMSs). The fabrication of these systems is commonly carried out using lithographic techniques, which allows for patterning of complex nanostructures to be possible. In this work, nanopillars having diameters less than 500nm were lithographically patterned from SU-8 negative photoresist and served as a template, which underwent sequential infiltration synthesis (SIS) with trimethyl aluminum (TMA), an organometallic precursor for AlOx. Cyclical repetition of the vapor phase infiltration process produced a unique composite in which an interpenetrating polymer-alumina network occupies a depth of 50nm from the pillar surface. An opportunity for tunability of the elastic properties of the SU-8 polymeric material exists with this fabrication technique by varying the number of infiltration cycles or the organometallic precursor.
Mechanical testing of nanopillars, which had undergone 0, 8 and 16 iterations of sequential infiltration with TMA, was performed using an in-situ nanomechanical testing device in scanning electron microscope. An increase in the yield strength and Young’s modulus of SU-8 composite nanopillars was observed with increasing numbers of infiltration cycles. SU-8 composite nanopillars that were infiltrated with 16 cycles of SIS exhibited the high yield strength (500MPa) but unusually low Young’s modulus (7.5GPa) in uniaxial nanocompression tests. The composite presented, which features interpenetrating polymer and alumina networks, exhibited high compressive strengths but is very compliant, a combination of mechanical features which has not been available in the strength-modulus space of Ashby chart. Furthermore, the SU-8 nanopillars with 16 cycles of infiltration exhibits a modulus of resilience of nearly 17,000 kJ/m3, orders of magnitude greater than the modulus of resilience for most metals and polymers. This nanostructured composite will offer the design of ultra-high elastic component in MEMS devices for advanced actuation and sensor technologies.
5:45 PM - NM6.7.04
Modeling Viscoelasticity in CNT-Dispersed Epoxy Thermoset via Molecular Simulations
Nithya Subramanian 1 , Aditi Chattopadhyay 1
1 School for Engineering of Matter Transport and Energy, Arizona State University, Tempe, Arizona, United States
Show AbstractThe viscoelastic spectrum is one of the primary signatures of amorphous polymers and melts, conveying information on the relaxation processes in the system. The William-Landel-Ferry (WLF) equation is a relationship used to describe the dependence of relaxation times on temperature at atmospheric pressure. However, the characteristic relaxation time of the equilibrated system above but near the glass transition temperature is shown to diverge with a power-law form rather than the WLF relationship. Bulk level experimental efforts have shed light into the viscoelastic phenomena of polymers and the results have been used in semi-empirical and phenomenological models. However, the nanoscale physical and chemical mechanisms that manifest as bulk level viscoelasticity can be fully investigated only with physics-based lower length scale simulations.
Most molecular models that characterize viscoelastic behavior in polymers track the evolution of free volume subsequent to the removal of an applied virtual load. This paper implements a ‘material clock’ for CNT-dispersed polymers at a range of temperatures in order to explore nonlinear viscoelastic evolution and recovery under various modes of loading. The concept of a material clock has been used previously for glassy polymer to study the influence of entropy, stress and strain on the nonlinear behavior. In this paper, an all-atom configuration of the nanopolymer system is obtained and equilibrated until an energy convergence criterion. By setting the potential energy as a basis for the material clock, the relaxation times for various equilibrated states will be calculated from the center-of-mass diffusion coefficients, instead of the free volume. The diffusive relaxation phenomena and rates will also be related to the packing fraction of the molecular system. The potential energy and the total energy will be calculated under deformation. These constitutive models contain parameters that are easily related to physical quantities such as the shear and bulk moduli, thermal expansion coefficient, etc. to obtain a molecular understanding of viscoelasticity in CNT-dispersed polymer.
NM6.8: Poster Session II: Mechanical Behavior of Nanostructure Composites
Session Chairs
Thursday AM, April 20, 2017
Sheraton, Third Level, Phoenix Ballroom
9:00 PM - NM6.8.01
The Effect of the Aspect Ratio and Surface Chemistry of Functionalized Graphene Materials on Their Ability to Reinforce Epoxy Nanocomposites
Cristina Valles 1 , Laura Burk 2 , Rolf Mulhaupt 2 , Robert Young 1 , Ian Kinloch 1
1 , University of Manchester, Manchester United Kingdom, 2 , University of Freiburg, Freiburg Germany
Show AbstractGraphene has attracted increasing interest since it was first isolated in 2004, due to its remarkable properties [1]. A promising application is the use of graphene materials to reinforce polymer matrices. Our early experiments on the micromechanics of graphene in polymer matrices have shown that the behaviour of the graphene can be explained using continuum micromechanics, despite its atomic thickness. In particular, the graphene follows the shear-lag model which predicts a minimum flake length for reinforcement to occur [2,3]. Given the poor interface between graphene and polymer, very large diameter flakes (> 20 µm) are required to give reinforcement and, even then, the performance of the graphene is significantly lower than theoretically predicted. One solution to this challenge is to tune the graphene-polymer interface by functionalising the graphene.
Graphene oxide (GO) emerges as a good material to reinforce polymers due to the presence of a high number of oxygen-containing functionalities in the surface of the flakes, providing both strong graphene-polymer interfaces and good dispersions of the flakes in the matrix. Recently, a method for the large scale production of high aspect ratio thermally reduced graphene oxide (TRGO) has been developed, in which GO powder is annealed at high temperatures under an inert atmosphere to remove functionalities from the flakes, increasing the C/O ratios and restoring the Csp2 network [4].
Alternatively to the oxidation of graphite, a simple 'one-step' procedure for the production of functionalized graphene in high yields has been developed. It combines graphene delamination with mechano-chemical functionalization by dry ball milling under Ar, CO2 or N2 pressures [5], which leads to the production of low aspect ratio edge functionalized graphene nanoplatelets.
Herein, edge carboxylated-, hydroxylated- and nitrogen-doped graphene with small aspect ratios prepared by ball milling of graphite are incorporated into an epoxy matrix at loadings from 0.25 to 5 wt.% and the mechanical properties of the composites are studied. The experimental results obtained by tensile testing are compared with those previously found for GO and TRGOs as reinforcements in epoxy at similar loadings [6]. How different C/O ratios, surface chemistries and aspect ratios of functionalized graphene fillers influence the stress transfer at the interface graphene-polymer is evaluated by Raman spectroscopy. In addition to the mechanical properties, the rheological properties of the nanocomposites are investigated, as they are of great importance for the development of functional composite materials for industrial applications.
[1] Geim AK et al. Nat Mater. 2007;6(3):183.
[2] Vallés C et al. Faraday Discuss. 2014;173:379.
[3] Vallés C et al. CST. 2015;111:17.
[4] Steurer P et al. Macromol Rapid Commun. 2009;30(4-5):316.
[5] Beckert F et al. Macromol Mater Eng. 2014;299(12):1513.
[6] Vallés C et al. J. Polym Sci, Part B: Polym Phys. 2016;54:281.
9:00 PM - NM6.8.02
The Effect of Functionalization on Microstructure and Mechanical Properties of Multiwalled Carbon Nanotubes Reinforced Aluminium Nanocomposite Synthesized by Spark Plasma Sintering
Lavish Singh 1 , Alok Bhadauria 1 , Tapas Laha 1
1 , IIT Kharagpur, Kharagpur India
Show AbstractPhysio-chemical functionalization was performed over multiwalled carbon nanotubes (MWCNTs) and resulting morphological and structural changes were analysed via electron microscopy, X-ray diffraction and Raman spectroscopy. It was found that although functionalization caused some amount of structural damage to CNTs, it extensively improved their dispersion. 0.5 wt% pristine and functionalized MWCNT reinforcement were mixed individually with high energy ball milled nanocrystalline aluminium powders and were consolidated via spark plasma sintering. The strengthening efficiency of functionalized MWCNTs matched well with the volume fraction rule of discontinuous fibers. Functionalized nanocomposite exhibited uniformly distributed CNTs within the matrix and enhanced mechanical properties as compared to the pristine counterpart. Improvement in microhardness and elastic modulus up to 16% and 11% respectively was observed in functionalized CNT reinforced composite. Efficient dispersion of CNTs leading to low porosity and improved interfacial bonding between matrix and reinforcement were attributed to superior mechanical properties of functionalized nanocomposite. Yield strength of the matrix, grain refinement, load transfer via MWCNTs, thermal mismatch and Orowan mechanism were the contributors to composite strengthening.
9:00 PM - NM6.8.03
Fabrication and Mechanical Properties of Functionalized Graphene Nanoplatelets Reinforced Epoxy Matrix Nanocomposites
Joon Hui Kim 1 , Jaemin Cha 1 , Jun Ho Lee 1 , Soon Hyung Hong 1
1 , Korea Institute of Science and Technology, Daejeon Korea (the Republic of)
Show AbstractAfter publication of first Graphene, numerous journals treating with this novel material were published. Unlike origin material, Graphite, Graphene showed superb properties originated from its two dimensional structure geometry. Graphene nanoplatelet (GNP), which is fabricated from raw Graphite using intercalation and thermal expansion method is able to produce Graphene in industrial level.
The major applications of GNP is the polymer nanocomposite. Research on nanocomposite has attracted interests in fields of industry and academic, started from 1990’s Nylon-6 matrix research by Toyota. Unlike other polymer composites, polymer nanocomposites show superb property despite of low reinforcement material volume percent. Also polymer nanocomposite is easier to fabricate than conventional consolidation process. The major fabrication factor of polymer nanocomposite is dispersibility of reinforcement material in polymer matrix. But GNP agglomerates among themselves due to van der Waals force, so these problem needs to be solved.
To solve agglomeration and dispersion problem, we adopted functionalization process to give GNP proper dispersibility in solvent. Functionalization process is divided into two process, Covalent functionalization and Non-covalent functionalization. Covalent functionalization uses strong acid or solvents to develop defect on GNP and adds functional molecule onto GNP, which can functionalize GNP sufficiently. However, non-covalent functionalization uses relatively weak bonding between GNP and functional molecules so this process do not harm surface of GNP. Also this process could maintain superb properties of GNP. Since polymer nanocomposite’s issue is to improve its properties with relatively low percent of GNP we chose pi-pi stacking process as a functionalization process.
In this research we functionalized GNP to prevent agglomeration and increase own properties by using functional molecule considering 3 conditions. These conditions for functional molecules are 1) Have benzene ring for pi-pi interaction with Graphene surface, 2) Have functional group to be dispersed in polar solvents 3) Cost effectiveness. Our research group chose Melamine as a functional molecule and successfully functionalized GNP. After functionalization of GNP, functionalized GNP/Epoxy (f-GNP/Epoxy) composite were fabricated by solvent mixing. Mechanical properties of f-GNP/Epoxy composites were characterized by using Microforce testing machine.
Tensile properties of f-GNP/Epoxy composites showed twice reinforcement effect compared to raw GNP/Epoxy composites. This results can be explained by functional molecules stacked on surface of GNP flakes, which hindered agglomeration among GNP flakes. This results leads to homogeneous dispersion of f-GNP in Epoxy and successfully optimized mechanical properties of composites. Our team wish that these results can provide useful property criteria of Graphene Nanoplatelet for structural materials as industrial applications.
9:00 PM - NM6.8.04
Mechanochemical Structural Relationship of Extruded Graphene/Polysulfone Composite Films
Justin Hendrix 1 , Jennifer Lynch 1 , Thomas Nosker 1
1 , Rutgers University, Piscataway, New Jersey, United States
Show AbstractPolysulfone (PSU) is one of the few high glass transition temperature polymers with properties uniquely suited for uses in harsh environments. The diphenylene sulfone group in PSU gives the polymer inherent thermal stability, oxidation resistance, and antifouling ability to known biologics. For CBRN defense, this makes PSU a uniquely suitable matrix material with intrinsic protective measures. Graphene, having both exceptional mechanical and conductive properties, behave as a superior reinforcing agent for many emerging polymer composites. By attaining a high degree of dispersion and improved interfacial strength, a performance enhancement effect can be obtained for produced graphene composites. The relationship between the mechanical, chemical, and morphological properties attained in a graphene-polymer composites is still not fully understood. To provide a detailed picture of the performance enhancing properties of a graphene-PSU composite, we conduct an investigation of the mechanical performance to the chemical/morphological properties between produced graphene-PSU films. Graphite and PSU was mixed using a novel high shear batch process, yielding graphene in-situ. The mixed graphene composite was extruded into films for mechanical testing. A structural relationship of the graphene PSU composite was detailed using X-Ray Diffraction, Scanning Electron Microscopy, Transmission Electron Microscopy and X-ray photoelectron spectroscopy. A link providing more information on the performance enhancement effect, degree of dispersion , and interfacial properties was attained.
9:00 PM - NM6.8.05
Mechanical Properties of Metal Nano-Composites Embedded with One and Two-Dimensional Materials
Raghu Santhapuram 1 , Scott Muller 1 , Arun Nair 1
1 , University of Arkansas, Fayetteville, Arkansas, United States
Show AbstractMetal nanocomposites have gained attention in engineering due to their unique mechanical properties. In this study, we focus on studying the mechanical properties of metal nanocomposite embedded with one-dimensional and two-dimensional materials. Previous studies have shown that two-dimensional material such as graphene can effectively inhibit dislocation propagation within metal-graphene nanocomposites under compressive loading, there by increasing the mechanical strength of the nanocomposite. We use molecular dynamics to study the mechanical properties of Ni-graphene nanocomposite under mode I loading. Here we aim to uncover the optimal number, size, and spacing of graphene sheets within the nanocomposite to enhance the fracture strength. Our preliminary results indicate that the structural arrangement of graphene sheets changes the fracture behavior of Ni-graphene nanocomposite. We also investigate a one-dimensional material, carbyne, which is the strongest known allotrope of carbon. Recent research has shown that the synthesis of long carbyne chains is viable, and it has opened the door for the study of nanocomposites that can utilize this mechanically superior material. We use a multiscale approach to study the mechanical behavior of carbyne on a nickel surface. We use density functional theory (DFT) to study the fundamental interaction between Ni (111) surface and carbyne. Based on DFT studies, molecular dynamics simulations are preformed to predict the mechanical properties of carbyne as a function of the chain length. The commensurability of one or more carbyne chains on a Ni (111) surface will also be discussed. The results of this research will help guide the design of metal nanocomposite embedded with one and two-dimensional materials.
9:00 PM - NM6.8.06
Mechanical and Thermal Properties of Graphene/Ultrahigh Molecular Weight Polyethylene Nanocomposites
Sivakumar Reddy 1 , Methawee Choosri 1 , Kartik Varadarajan 2 , Brian Wardle 3 , S Kumar 1
1 Department of Mechanical and Materials Engineering, Masdar Institute, Abu Dhabi United Arab Emirates, 2 Department of Orthopaedic Surgery, Massachusetts General Hospital, Boston, Massachusetts, United States, 3 Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractIn this study, mechanical and thermal properties of graphene nanoplatelets (GNP)/ultra-high molecular weight polyethylene (UHMWPE) composites fabricated by solution mixing and compression molding techniques are reported. The microstructure of these nanocomposites was fully characterized using scanning electron microscopy (SEM) and Raman spectroscopic techniques. Thermal properties are measured using differential scanning calorimetric (DSC), and thermal gravimetric analysis (TGA). X-ray diffraction (XRD) measurements are carried out to find out the degree of crystallinity with increase in wt. % of GNP (0-1 wt. %) in UHMWPE. Tensile tests revealed that, yield strength of the nanocomposite increases up to 15 % with increasing in GNP loading. Elastic modulus of the nanocomposite enhanced nearly 20% at 1 wt. % GNP. The enhancement in mechanical and thermal properties suggests that UHMWPE/GNP composites are well suited for artificial implants/joints.
9:00 PM - NM6.8.07
Characteristics of Nylon 6,6 Composites Reinforced Carbon Fiber Grafted with Multi-Walled Carbon Nanotube
Eun yeob Choi 1 , So-Hyeon Hong 1 , Hyejin Park 1 , Chang Keun Kim 1
1 , Chung-Ang Univ, Seoul, SE, Korea (the Republic of)
Show AbstractNoncovalently functionalized carbon fiber (CF) and multi-walled carbon nanotube (MWCNT) hybrid were prepared for use in nylon 6,6 (PA66) composites. The 1-pyrenebutylic chloride (PBC) absorbed onto the CF and MWCNT surface by physisorption and the acyl chloride groups in the PBC reacted with the amine groups in the PA66 during the melt extrusion. As a result, PA66 was grafted with PBC at the surface of CF / MWCNT hybrid. Formation of noncovalently functionalized CF / MWCNT hybrid was confirmed by using Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and thermogravimetric analyses (TGA). The drop-on-fiber method was used to estimate interfacial adhesion energies between PA66 and CF / MWCNT hybrid. The PA66 composite containing functionalized CF / MWCNT hybrid showed the highest interfacial adhesion energy that can be achieved with PA66 composites containing CF / MWCNT hybrid. For fixed CF / MWCNT contents in the composite, the tensile properties and elongation of the PA66 composite containing functionalized CF / MWCNT hybrid was higher than that of PA66 composites containing pristine CF and CNTs.
9:00 PM - NM6.8.08
Nanoparticle and Nanotube Composite Structures for Sensitive and Durable Strain Sensors
Do Hoon Lee 1 , Taewan Kim 1 , Wonbin Song 1 , Byung Yang Lee 1
1 Department of Mechanical Engineering, Korea University, Seoul Korea (the Republic of)
Show AbstractIn this study, we demonstrate a strain sensor based on composite structures of tin-doped indium oxide (ITO) nanoparticles (NPs) and carbon nanotubes (CNTs) using a low cost, simple, and effective fabrication method. Patterns of ITO/CNT composite channels were formed on flexible substrates with prepatterned sacrificial structures by assembling ITO NPs and CNT using simple homemade pulling system. This enabled precise control on the electrical properties of the channels such as sensitivity and resistance by controlling the channel length, width, and thickness. Also, our pulling method enables minimization of material loss due to reusability of suspension and not involving etch process or high temperature process. The assembled ITO/CNT nanocomposite can be used as strain sensors with high gauge factor. Their gauge factors have comparable values to previous works using Cr or Au NPs. By fabricating arrays of parallel channels, we could minimize the crosstalk between the two orthogonal (transverse and longitudinal) bending directions. Also, our nanocomposite sensor showed stable sensing response to endure more than 400 times of cycling bending tests. Here, the incorporated CNT stabilizes the overall structure. We investigated the structural integrity of channels by observing the crack propagation in it using SEM. After a few hundreds of bending cycles, the cracks did not show further propagation. Furthermore, our sensors showed high optical transparency up to ~80% in the visible range owing to the high transmittance property of ITO. We expect that the ITO NP-based strain sensors can play an important role in in developing future applications such as wearable and stretchable electronic devices.
9:00 PM - NM6.8.09
Chemically Linked Particles Networks
Gabriel Iftime 1 , Junhua Wei 1 , David Johnson 1 , Jessy Rivest 1
1 , Palo Alto Research Center, Palo Alto, California, United States
Show AbstractThe Palo Alto Research Center is developing chemically linked particles networks, a novel composite material wherein inorganic particles are incorporated as “monomer” units into polymer chains. Compared to conventional dispersed particles polymer composites where particles can move easily within the polymer matrix when subjected to mechanical stress, in chemically linked particles networks the particles movement is restricted. This feature provides structures with enhanced mechanical properties.
We have demonstrated the concept with chemically linked graphene networks. Novel surface functionalized exfoliated graphene flakes have been synthesized, characterized and cured to produce networks of graphene flakes connected with polymer linkers. Formulations made with graphene nanoparticles dispersed in polymer base showed a 2X increase of the Young modulus with simultaneous decrease of the tensile strength (by 5X). This is the expected trend when adding particle fillers to polymer binders. On the contrary, formulations made with chemically bonded graphene flakes showed further increase of the Young modulus (3.3X) versus the base polymer but without decrease of the tensile strength. These results demonstrate the potential of chemically linked graphene networks to provide a viable path to the development of tough materials that have both high Young modulus and tensile strength.
9:00 PM - NM6.8.11
Investigation on Friction Properties of Diamond-Like Carbon against Alumina at High Temperature—A Tight-Binding Quantum Chemical Molecular Dynamics Simulation Approach
Yang Wang 1 , Jingxiang Xu 1 , Yusuke Ootani 1 , Takeshi Nishimatsu 1 , Yuji Higuchi 1 , Nobuki Ozawa 1 , Koshi Adachi 2 , Momoji Kubo 1
1 Institute for Materials Research, Tohoku University, Sendai, Miyagi, Japan, 2 Department of Mechanical Systems Engineering, Graduate School of Engineering, Tohoku University, Sendai, Miyagi, Japan
Show AbstractAlumina sliding bears are widely used in various industries such as the cars, aerospace instruments, and so on. To reduce the friction between alumina and the counter material, diamond-like carbon (DLC) is employed as a solid lubricant coated on the surface of the counter material. During the friction, friction heat causes a high temperature on the contact surface of DLC/alumina. Experimental studies reported that the friction behavior of DLC/alumina strongly dependes on the temperature. In order to improve the friction properties of DLC/alumina, it is essential to understand the friction mechanisms at various temperatures. However, experimental studies are difficult to investigate the detailed friction behavior at the atomic scale. In this study, we performed tight-binding quantum chemical molecular dynamics simulation to study the atomic-scale friction process of DLC/alumina at various temperatures. The friction simulations were performed at temperatures from 300 K to 1000 K with an interval of 100 K. At the low temperature from 300 K to 600 K, smooth sliding between DLC and alumina substrates was observed and the friction coefficients took low values of around 0.05. At 700 K and 800 K, the interfacial C-O and C-Al bonds were formed between DLC and alumina substrates during the sliding. The interfacial bonds resulted in an increase in friction coefficients. However, when temperature further increased to 900 K and 1000 K, we observed the graphitization of DLC substrate during the sliding. The graphite-like structure prevented the formation of interfacial C-O and C-Al bonds during the sliding, leading to a decrease in the friction coefficients. We revealed the effect of temperature on the friction process of DLC/alumina at the atomic scale: friction coefficients of DLC/alumina increased at 600 K ~ 800 K due to the formation of interfacial C-O and C-Al bonds, whereas friction coefficients decreased at the temperature higher than 800 K due to the graphitization of DLC.
9:00 PM - NM6.8.12
Stretchability of Nanolaminates with Alternating Amorphous Aluminum Oxide and Polymer Layers
Jeong-Hyun Woo 1 , Na-Ri Kang 1 , Ju-Young Kim 1 , Na-Hyang Kim 1
1 , UNIST, Ulsan Korea (the Republic of)
Show AbstractAmorphous structure aluminum oxide (Al2O3) films are used for various applications such as gas- and moisture-diffusion barriers. Al2O3 films deposited by atomic layer deposition (ALD) have good step coverage, high density and low surface roughness. However, these films contain more impurities and need longer processing time at lower growth temperatures. Plasma-enhanced ALD (PEALD) using trimethylaluminum (TMA) and O2 plasma was less temperature-dependent than thermal ALD (<150°C). By Griffith’s theory, the fracture strength of brittle materials increases with decreasing thickness and reaches an ideal strength at a critical thickness. Also, metallic glass-polymer nanolaminate composites had different mechanical behavior from metallic glass single layers, as reported by several authors: polymer layers suppressed catastrophic failure of metallic glass. So here we look at the critical thickness of amorphous Al2O3 films, which are ceramic materials, and the mechanical behavior of amorphous Al2O3 and polymer multilayer structures. The hole-nanoindentation method, which requires very simple sample preparation, was used here to measure mechanical properties of ultra-thin films. For sample preparation, 20 nm-thick chromium film and 100 nm-thick gold film were deposited as an adhesive and sacrificial layer by sputtering. We deposited Al2O3 films using PEALD at low temperatures (80, 120, 150°C) and different thickness (30, 90 nm). Then the gold layer was selectively etched using gold etchant TFA and the Al2O3 film was transferred to the hole-substrate. We analyzed effect of temperature and thickness on mechanical properties and found the critical thickness of Al2O3 film. We then made amorphous Al2O3-polymer nanolaminate composites and measured mechanical properties by hole-nanoindentation and tensile testing by an in-situ system.
Symposium Organizers
Seung Min Han, Korea Advanced Institute of Science and Technology (KAIST)
Arief Budiman, Singapore University of Technology and Design
Amit Misra, University of Michigan–Ann Arbor
Ruth Schwaiger, Karlsruhe Institute of Technology
NM6.9: Metal-Matrix Nanocomposites
Session Chairs
Thursday AM, April 20, 2017
PCC West, 100 Level, Room 106 C
9:30 AM - *NM6.9.01
The Promise of Nanotwins—Beyond Simple Alloys
Jessica Krogstad 1 , Megan Emigh 1 , Pralav Shetty 1 , Gi-Dong Sim 2 , Timothy Weihs 3 , Kevin Hemker 2
1 Department of Materials Science and Engineering, University of Illinois, Urbana-Champaign, Urbana, Illinois, United States, 2 Department of Mechanical Engineering, Johns Hopkins University, Baltimore, Maryland, United States, 3 Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland, United States
Show AbstractA high density of coherent intefaces within nanocrystalline metals have recently demonstrated a remarkable balance of strength and ductility. Numerous mechanisms have been proposed to explain this behavior including confined layer slip and detwinning. However, to date, a relatively limited range of materials with this unique microstructure have been fabricated and evaluated. Here we explore several Ni-based superalloy compositions fabricated in thin film form via DC magnetron sputtering. The resulting microstructures demonstrate a high density of nanotwins and result in outstanding strength as is expected from this morphology. We also confirm the stability of such nanotwins in these complex alloys upon thermal aging. However, upon additional annealing, we reveal a unique potential to tune the mechanical response through defect-assisted transformation pathways not accessible in bulk/conventionally-processed alloys of the same composition. These observations prompt a more thorough investigation of the interfacial (grain boundary and nanotwin) transport properties and suggest that the functionality of high-density nanotwins extends beyond mechanical properties.
10:00 AM - NM6.9.03
Creep Behavior of a Stable Nanocrystalline Alloy
Mansa Rajagopalan 1 , Kristopher Darling 2 , M. Komarasamy 3 , M. Bhatia 1 , B. Hornbuckle 2 , R. Mishra 3 , K. Solanki 1
1 , Arizona State University, Tempe, Arizona, United States, 2 Weapons and Materials Research Directorate, Army Research Laboratory, Aberdeen proving Ground, Maryland, United States, 3 , University of North Texas, Denton, Texas, United States
Show AbstractNanocrystalline (NC) materials, attract a lot of attention owing to their exceptional strength which stems from the reduction in grain size. However, this limits their practical application as their high strength generally comes with dramatic losses in other properties, such as creep resistance. The deformation in these conventional NC materials is said to be controlled by the high fraction of GBs with diffusion based mechanisms taking a predominance. A NC-material with never seen before exceptional property combinations, i.e., high strength with extremely high temperature creep resistance is presented in this study. The unusual combination of properties in these alloys is achieved through the creation of a unique architecture of Ta based nanoclusters that stabilizes the Cu-based microstructure at extreme conditions through Zener pinning mechanism even at a high homologous temperature of 0.64 (600 °C). The processing comprised of
high energy mechanical alloying and consolidation through equal channel angular processing (ECAE),and as processed microstructure consists of an average Cu matrix grain size of 50 ± 17.5 nm and with a wide dispersion of Ta particle sizes, ranging from atomic nanoclusters to much larger precipitates.In summary, this study points to a new beginning for innovative fundamental and applied science in designing NC-alloys with a range of exceptional properties. Further, the presented research on NC-Cu-10at.%Ta alloys proves immiscible based systems produced from non-equilibrium processing represent a new generation of materials for several applications that include extreme conditions.
10:15 AM - NM6.9.04
Sequential Electrophoretic Depositions for Free-Standing Ni-SiO2 Nanocomposite Inverse Opals with Enhanced Mechanical Properties
Pei Sung Hung 1 , Chen-Hong Liao 1 , Yu Cheng 1 , Tsung-Lin Hsieh 1 , Yu-Szu Chou 1 , PuWei Wu 1
1 , National Chiao Tung Univ, Hsinchu Taiwan
Show AbstractFree-standing inverse opaline films exhibit unique properties attributed to their distinctive large surface area and interconnected pores channels. However, a robust mechanical property is a serious challenge for possible applications in filters and membranes. In this work, we demonstrate sequential electrophoretic depositions to fabricate free-standing Ni-SiO2 nanocomposite inverse opaline film with improved mechanical properties. Relevant processing parameters are explored and optimized that allow for ordered assembly of polystyrene microspheres and nanoparticulate SiO2 as a colloidal template. Afterwards, we electroplate Ni to the interstitial voids within the colloidal template, followed by selective template removal via heat treatment in reducing atmosphere. With nanoindentation experiments, the Ni/SiO2 nanocomposite inverse opals possess improved toughness (up to 200%) and greater Young’s modulus (up to 400%) as compared to Ni inverse opals. SEM is conducted for structural observation over opaline and inverse opaline samples. The crystallinity and composition of the nanocomposite inverse opals are determined by XRD analysis.
10:30 AM - NM6.9.05
Effect of Graphene Nano Platelets (GNPs) on the Mechanical Properties and Fracture Behavior of Spark Plasma Sintered Aluminum Based Nanocomposite
Alok Bhadauria 1 , Lavish Kumar Singh 1 , Tapas Laha 1
1 Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur India
Show AbstractHigh energy ball-milled aluminum powders, mixed with 0.5 wt% graphene nanoplatelets (GNPs) was consolidated via spark plasma sintering to understand the effect of grain size, reinforcement dispersion behavior and consequent effect on mechanical and tribological properties of Al-based nanocomposite. Microstructural variation in the sintered composites with variation in grain size was analyzed using field emission scanning electron microscopy equipped with electron dispersive spectroscopy, atomic force microscopy, transmission electron microscopy, X-ray diffraction and Raman spectroscopy. GNPs were uniformly distributed throughout the matrix without any segregation and chemical reaction at the interface of Al and GNP. Mechanical and tribological properties were evaluated through nanoindentation, tensile and nanoscratch test. Nanocrystalline Al-0.5 wt% GNP nanocomposite exhibited higher hardness and wear resistance without significant pile-ups, as well as 85% increment in yield strength in comparison to pure microcrystalline Al. Detailed fractography study revealed various modes of fracture viz. ductile, mix and brittle types according to the morphology and microstructure of the nanocomposites.
NM6.10: Graphene or CNT Containing Composites
Session Chairs
Thursday PM, April 20, 2017
PCC West, 100 Level, Room 106 C
11:15 AM - *NM6.10.01
Recent Work of Proximity Field Nanopatterning toward Large Area, Three-Dimensional Nanostructures
Seokwoo Jeon 1
1 Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of)
Show AbstractNumerous three dimensional (3D) nanofabrication methods have been proposed for novel applications in mechanical metamaterials. However, highly periodic 3D fabrication in large area and volume has limited success. Here I present our recent efforts to expand the limit in size of highly periodic 3D nanostructures through Proximity field nanoPatterning (PnP) which uses conformal phase masks with outstanding scalability and easiness of the large area patterning. After brief overview of 3D nanofabrication technique and potential application fields, mechanical behaviors of nanocomposites based on 3D nanostructures will be discussed. Recently, many researchers have reported mechanically enhanced layered materials via alternating lamination of target materials (metal/graphene or metal/ceramic). Although this multilayer approach can result in strengthening, there are limitations in scaling-up to bulk synthesis as well as having highly anisotropic mechanical properties. Here, we present a novel approach using PnP for developing ultra-strong, light materials by i) converting 2D layered structures into 3D interdigitated structure of submicron metallic grains, and ii) selectively locating ultrastrong 2D materials (i.e. graphene), or thin ceramics, at the boundary of the metallic grains. This approach will not only guarantee high mechanical strength (close to the theoretical strength), but also result in more isotropic, high strength that can enhance the load bearing capability in all 3 directions.
11:45 AM - NM6.10.02
Probing Interfacial Mechanics in Ceramic Nanocomposites Reinforced with 1D/2D Carbon Nanostructures
Yingchao Yang 1 , Xin Liang 2 , Maria Ramirez 5 , Brian Sheldon 3 , Jun Lou 4
1 , Rice University, Houston, Texas, United States, 2 , Changzhou University, Changzhou China, 5 , Brown University, Providence, Rhode Island, United States, 3 , Brown University, Providence, Rhode Island, United States, 4 , Rice University, Houston, Texas, United States
Show AbstractOne-dimensional (1D) CNTs, two-dimensional (2D) graphene, and their derivatives including functionalized CNTs, CNT based core/shell nanostructures, and graphene oxides (GO) have tremendous potential in nanocomposite applications owing to their exceptional mechanical properties. The mechanical performance of these nanocomposites not only depends on the strength of 1D and 2D fillers, but also strongly depends on the interface between the filler and matrix. In this study, we developed and utilized a nanomechanical testing platform to carry out in-situ pull-out experiments in a scanning electron microscope and quantify the interfacial shear strength between individual CNT and polymer derived ceramic (PDC) matrix, and between individual sheet of graphene (graphene oxide) and PDC. For CNTs, an atomic layer deposited (ALD) Al2O3 and HfO2 were also coated onto CNTs to modulate the surface roughness in order to take advantage of the interfacial interlocking mechanism. The carefully designed comparative study makes it possible to better understand the interfacial interactions between 1D/2D fillers and ceramic matrices.
12:00 PM - NM6.10.03
Investigation of Nanoscale Toughening Mechanism in MoS2 Dispersed Epoxy Composite System
Dhriti Nepal 1 , John Ryan 1 , Samit Roy 2 , Robert Wheeler 1
1 , Air Force Research Laboratory, Wright Patterson AFB, Ohio, United States, 2 , University of Alabama, Tuscaloosa, Alabama, United States
Show AbstractMultifunctional materials with nanoparticles embedded into a polymer matrix are expected to enhance structural integrity and induce smart sensing capability in ways critical to next-generation materials. However, an understanding of the nature of the fracture and subsequent prediction of material properties is still very premature, owing to a lack of a) characterization techniques to capture the mechanics at sub-100 nm scale, and b) accurate models for the estimation of failure modes. Current models based on linear fracture mechanics fail to capture sub-nanometer crack-tip formation or describe the role of nanoinclusion on the fracture toughness of the material. This study incorporates the crack-tip stress field in molecular dynamics simulations to evaluate fracture toughness using MoS2-epoxy composites as a model system. This allows direct measurement of the near-tip strain field, enabling an understanding of the mechanism of toughness enhancement by nanoparticles. Excellent dispersion of MoS2 nanoparticles is prepared in DGEBA epoxy system by controlled chemistry and processing conditions. The detailed characterization using FT-IR, DSC, DMA, AFM-IR enabled insights into the nanosheet-polymer network system. High-resolution TEM, SEM, and AFM as well as nano-X-ray computed tomography provided an understanding of 3D dispersion status of these nanosheets. Experiments associated with nanoscale visualization of fracture in the composite are conducted using in-house in situ tensile testing stages placed within SEM and AFM. These experiments provide in-depth knowledge of the influence of flaw size, and platelet size, thickness and dispersion of nanoparticles on fracture toughness and will be indispensable in guiding the refinement of multi-scale models.
12:15 PM - NM6.10.04
Mechanical and Morphological Investigation of TiO2/Graphene Heterostructures
Changhong Cao 1 , Sankha Mukherjee 4 , Jian Liu 2 , Biqiong Wang 2 , Maedeh Amirmaleki 1 , Jane Howe 3 , Doug Perovic 2 , Chandra Veer Singh 2 1 , Yu Sun 1 , Tobin Filleter 1
1 Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario, Canada, 4 Department of Materials Science and Engineering, University of Toronto, Toronto, Ontario, Canada, 2 Department of Mechanical and Materials Engineering, University of Western Ontario, London, Ontario, Canada, 3 , Hitachi High-Technologies Canada, Inc., Toronto, Ontario, Canada
Show AbstractGraphene was integrated in many heterogeneous structures not only because of their excellent electronic or photonic properties but also due to their superior mechanical properties. However, the mechanical behavior of thin film based heterogeneous structures is not simply the combinational behavior of each heterogeneous component. The complex mechanical response of heterogeneous films has not been well understood. Here, we studied ALD synthesized TiO2/graphene, as a representative material, to investigate the mechanical and morphological behaviors of thin film based heterostructures using an experiment-computational combined approach. Results showed that the Modulus enhancement effect of graphene to the heterostructures is only present when TiO2 was deposited in a certain thickness range, beyond which, the Modulus of the heterostructure will reach to that of bulk TiO2. It was validated that Rule of Mixture can be used to approximately estimate the Modulus of TiO2/graphene heterostructures. Fracture study of the heterostructures indicate that TiO2/graphene heterostructures exhibit brittle failure mode and at high stress level, graphene indeed serves as structural support in the heterostructures and undertakes significant amount of stress when failure initiates. The results significantly contribute to the rational design of ultrathin film based heterostructures from a mechanics perspective. The methodology developed can potentially be used to study mechanical behaviors of other heterofilms.
12:30 PM - NM6.10.05
Hybrid Elastomer Nanocomposites with Improved Tensile Strength and Modulus
Rostyslav Dolog 1 , Darryl Ventura 1 , Valery Khabashesku 1 , Qusai Darugar 1
1 , Baker Hughes, Houston, Texas, United States
Show AbstractA novel method to produce hybrid HNBR (Hydrogenated Nitrile Butadiene Rubber) nanocomposites was developed to create a technology platform with potential applications in various industries, specifically targeting demanding, high-stress conditions.
The new approach focuses on solving key issues in the formulation of elastomer nanocomposites: the quality of nanoparticle dispersion within a polymer matrix and the availability of a load-transfer mechanism at the interface between blend components. The new method addresses both challenges via the chemical modification of nanotubes to decrease CNT (Carbon Nanotubes) aggregation and provide chemical crosslinks between CNT and the polymer matrix. Several reaction schemes of incorporating nanoparticles into the polymer matrix and crosslinking agents were considered. Mechanical properties and the chemical resistance of nanocomposites were assessed using standard techniques for the characterization of elastomers for oilfield applications.
The approach enhanced the mechanical properties of hybrid HNBR elastomers beyond the abilities of nonfunctionalized CNTs. Conventional CNTs can provide reinforcement to the polymer matrix at high temperatures and improve the modulus of the rubber compound, while simultaneously negatively affecting elongation at break. The new method mitigated the negative impact of reinforcement on elastomer compound elongation, providing a way to improve tensile strength and modulus of rubber, without significantly decreasing its elongation at break. The experimental results indicate that it is possible to further enhance the tensile strength and modulus of the rubber by combining CNTs and carbon black in one system, because of the synergistic effect of two fillers with different particle size.
The study provides an understanding of the effect of nanofillers on the mechanical, thermal, and chemical properties of elastomer composites. The presented novel approach enables the formulation of new high-performance compounds for the oil industry and beyond.
12:45 PM - NM6.10.06
Coaxial Carbon@Boron Nitride Nanotube Arrays with Enhanced Thermal Stability and Mechanical Response
Lin Jing 1 2 , Roland Yingjie Tay 3 , Hongling Li 3 , Siu Hon Tsang 4 , Edwin Hang Tong Teo 1 3 , Alfred Tok 1 2
1 School of Materials Science and Engineering, Nanyang Technological University, Singapore Singapore, 2 Institute for Sports Research, Nanyang Technological University, Singapore Singapore, 3 School of Electrical and Electronic and Engineering, Nanyang Technological University, Singapore Singapore, 4 Temasek Lab@NTU, Nanyang Technological University, Singapore Singapore
Show AbstractVertically aligned carbon nanotube (CNT) arrays have been widely applied in energy dissipation systems due to their excellent compressive mechanical properties. However, the specific synthesis process affects significantly on the characteristics of the CNT arrays such as tube areal density, dimensions and morphologies, which may lead to their variety in mechanical behaviours. Herein, a post-growth thermal chemical vapour deposition process is used to introduce outer coaxial boron nitride nanotube (BNNT) with a wall thickness of up to 1.37 nm (5 walls) onto the CNTs to build the carbon@boron nitride nanotube (C@BNNT) structure. As a result, the as-synthesized CNT arrays with low compressive resilience are transformed into compressible C@BNNT arrays, which perform a nearly complete shape recovery at an applied strain of 50% (76% recovery maintained after 10 cycles) with dramatic fourfold increment in the compressive strength, as well as a significantly high and constant energy loss coefficient (~60% at a 50% strain even after 100 cycles), attributing to the synergistic effect of the CNT and outer BNNT walls. Furthermore, the C@BNNT arrays exhibit better structural and mechanical stabilities in high temperature atmospheres as compared to the as-synthesized CNT arrays due to the protection of outer BNNT with remarkable thermal stability. This work presented here not only shows the potential of the C@BNNT arrays for compressive thermal/mechanical contacts applications in harsh environments, but also provides a new approach to amelioration of the thermal/mechanical performance of the CNT arrays by incorporating additional conformal layers.
NM6.11: <i>In Situ</i> SEM/TEM Analysis of the Deformation Behavior
Session Chairs
Thursday PM, April 20, 2017
PCC West, 100 Level, Room 106 C
2:30 PM - *NM6.11.01
Nanotwin-Governed Toughening Mechanism in Hierarchically Structured Biological Materials
Sang Ho Oh 1
1 , Sungkyunkwan University, Suwon Korea (the Republic of)
Show Abstract
As an important class of natural biocomposite materials extensively investigated, mollusk shells possess remarkable mechanical strength and toughness as a consequence of their hierarchical structuring of soft organic and hard mineral constituents through biomineralization. Strombus gigas, one of the toughest aragonitic mollusk shells commonly known as the giant pink queen conch, contains a high density of nanoscale {110} growth twins in its third order lamellae, the aragonite building block of the material. Although such nanotwinned aragonite has been known for more than 30 years, its roles and functions in mechanical behaviors and properties of biological materials have been ignored all along, in spite of worldwide interests in biomimetic materials and numerous studies in recent years aimed to investigate the relationship between mechanical properties (e.g., moduli, strength and toughness) and the elegant nano- and hierarchical structures of biological materials. Various toughening mechanisms in biological materials have been proposed so far, including microcracking and crack bridging, flaw tolerance of nanostructure, viscoelastic deformation of organic layers, and frictional sliding of mineral platelets, but the influence of nanoscale twins on toughness of biological materials remains unknown and unexplored. A combination of in situ fracture experiments inside a transmission electron microscope, large scale atomistic simulations and finite element modeling show that the twin boundaries can effectively block crack propagation by inducing phase transformation and delocalization of deformation around the crack-tip. This mechanism leads to an increase in fracture energy of the basic building block by one order of magnitude, and contributes significantly to that of via structural hierarchy. The unique properties and structural features of nanotwinned aragonitic conch shell provide a guide to designing and fabricating hierarchically structured biomimetic materials with high toughness and high modulus.
3:00 PM - NM6.11.02
Characterizing the Mechanical Properties of Individual Phases in Nanostructured Composites
Clemence Bos 1 , Heinz Riesch-Oppermann 1 , Ruth Schwaiger 1
1 IAM, Karlsruhe Inst of Technology, Eggenstein-Leopoldsh Germany
Show AbstractUnderstanding the deformation and failure mechanisms of nanocomposites requires information about the microstructure as well as knowledge of the mechanical properties of the individual phases in the composite. While for homogeneous materials nanoindentation is nowadays routinely and successfully used to determine the mechanical properties, the characterization of composites or heterogeneous materials is still challenging at the nanoscale since it mainly reveals averaged material properties. In order to characterize the properties of the individual phases, though, a different approach involving statistical analysis methods is required.
In this study, we investigated polymeric and metallic nanocomposites using nanoindentation. We analyzed distributions of mechanical properties determined from grid indentations to different depths. The stiffness of the polymer composites changes significantly over a period of three months. In addition, the ageing of the individual phases can clearly be determined. However, several experimental factors and analysis methods, such as indentation depth, distribution function or number of phases, may influence the results. Moreover, while the elastic properties of the individual phases can be determined reliably, the hardness is significantly affected by the presence of interfaces and the related constraints as observed for metallic composites.
3:15 PM - NM6.11.03
In Situ Compression Testing of High-Strength Low-Weight Micro- and Nanolattices Using 3D Nano-Scale X-Ray Imaging
Almut Schroer 2 , Hrishikesh Bale 1 , Jens Bauer 2 , Ruth Schwaiger 2
2 Karlsruhe Institute of Technology, Institute for Applied Materials, Eggenstein-Leopoldshafen Germany, 1 , Carl Zeiss X-ray Microscopy, Pleasanton, California, United States
Show AbstractThe combination of high-strength and low-weight is achieved by fabricating micro- and nanolattices with specific 3D architecture. Lattices are typically manufactured using 3D direct laser writing as polymer microstructures with strut diameters in the range of 1 µm. Different strategies can be pursued to improve the strength of the as-patterned polymer microstructures: specific annealing treatments at 200°C in vacuum, coating with a 10 nm thick alumina coating deposited by atomic layer deposition, and a pyrolysis procedure in vacuum. While push-to-pull tensile tests showed that the annealing treatment at 200°C and the alumina coating result in a strength increase up to a factor of 10, the strength increase of tetrahedral truss structures reached only a factor of 2.5. The reduced nominal failure stresses are related to the peak stresses that are present at the truss nodes. Due to the pyrolysis procedure, the polymer microlattices shrink by up to 80% of their original size and are transformed into glassy carbon structures. Here, enhanced mechanical properties of the truss structures are achieved by both improved material properties and the mechanical size effect. In-situ imaging experiments done in the scanning electron microscope (SEM) showed near brittle fracture of the nanolattice structure during compressive testing. However SEM images fail to reveal the internal failure events within the lattice. We hereby present results obtained by utilizing 3D nano-scale x-ray tomography on a laboratory X-ray microscope, combined with the use of an in-situ nano-mechanical load stage to carry out non-destructive imaging as the nano-lattice structure is loaded in compression. Using a 3D resolution of up to 50 nm to resolve the detailed structure of individual trusses, we study the behavior of the nano-lattice truss structure under load. The tomography images provide key insights in understanding the fracture behavior and enable a full 3D evaluation of structural defects that contribute to the lowered failure stress than the predicted values.
3:30 PM - NM6.11.04
Competition of Surface Topography and Material Inhomogeneity—A Numerical Linear-Elastic Indentation Model
Veruska Malave 1 , Jason Killgore 1 , Edward Garboczi 1 , John Berger 2
1 , National Institute of Standards and Technology, Boulder, Colorado, United States, 2 , Colorado School of Mines, Golden, Colorado, United States
Show AbstractAtomic force microscopy (AFM) indentations in nanocomposites can encounter a number of challenges that includes interpreting mechanical properties when both non-flat surface topography and material heterogeneity are present. Generally, the surface of indented specimens is prepared to be optically flat and smooth; however, this is rarely the case. Furthermore, an unknown compositional interface can give rise to misinterpreting a mixed-phase elastic response as a single-phase. Any changes in surface topography near the material interface is intrinsically coupled with material phase changes, contributing to the extracted mechanical properties of the composite material.
This work reports the non-Hertzian mechanical response of an axisymmetric linear elastic model that consists of a rigid spherical indenter and a perfectly elastic and isotropic material that is to be indented. The deforming body contains one laterally and compositionally graded material interface as well as a convex or concave surface curvature. Using the finite element (FE) method and Hertzian formulae, an empirical relation is developed to improve the extraction of the indentation modulus by taking into account both of the competing effects of surface topography and material inhomogeneity. Both the contact radius and the location of the compositionally-graded interface considerably affect the calculation of the elastic modulus, which can result in significant inaccuracies when extracting the elastic modulus in non-uniform materials with pronounced non-flat surfaces. The length scale of the contact radius and the distance to the material interface are in competition, and play an important role in the indentation mechanics.
3:45 PM - NM6.11.05
Investigation into the Deformation Twins in Pure Ti via In Situ and Ex Situ Microstructure Observation
Jianghua Shen 1 , Biao Chen 1 , Xiaoxin Ye 1 , Hisashi Imai 1 , Junko Umeda 1 , Katsuyoshi Kondoh 1
1 , Osaka University, Ibaraki Japan
Show AbstractThe aim of this study is to investigate deformation twinning in pure Ti under tension. The main focuses include the effect of grain size, texture and the concentration of oxygen on twin formation, as well as its role on the mechanical behavior of pure Ti. To this end, Ti samples of various conditions have been fabricated via powder metallurgy, and then tested under quasi-static tensile loading. The microstructures of the samples were tracked through in-situ and ex-situ observation by using electron backscattered diffraction (EBSD) affiliated to a scanning electron microscopy (SEM). It has been found that the grain size and oxygen content have a significant impact on the twin formation, while the texture has a great influence on the type of deformation twins produced in the sample. The activation of deformation twins has been related to the mechanical behavior of the Ti samples.