Kazue Orikasa1,Cheol Park2,Sang-Hyon Chu2,3,Calista Lum4,Tony Thomas1,Arvind Agarwal1
Florida International Universtiy1,NASA Langley Research Center2,National Institute of Aerospace3,University of California Merced4
Kazue Orikasa1,Cheol Park2,Sang-Hyon Chu2,3,Calista Lum4,Tony Thomas1,Arvind Agarwal1
Florida International Universtiy1,NASA Langley Research Center2,National Institute of Aerospace3,University of California Merced4
<br/>Neutron radiation exposure and extreme thermal cycling are some of the main challenges faced during various aerospace missions. There is a critical need for advanced lightweight radiation shielding and thermally conductive materials. Polymer composites are commonly used in aerospace technology due to their low density, hydrogen richness, and ease of processing. However, polymers have limitations such as poor thermal conductivity, poor mechanical properties, and low neutron shielding properties. Two-dimensional (2D) Boron Nitride Nanoplatelets (BNNP) are excellent candidates for polymer matrix fillers due to their superior thermal neutron shielding and thermal properties. The 2D material anisotropic behavior unlocks the potential for composite property tailoring. However, the nanomaterial dispersion within polymer matrices is challenging due to their agglomeration tendency. In this study, a highly dispersed and lightweight BNNP foam (density 0.05 g/cm<sup>3</sup> and porosity 97.5%) was fabricated via Freeze-Drying processing. Freeze-Drying overcomes nanomaterial agglomeration challenges and enables the foam microstructure design through the control of the thermodynamic processing parameters such as mold geometry, mold material, and solid loading. The foam microstructure was designed to be lamellar, enhancing the anisotropic behavior of 2D BNNP. Subsequently, neutron radiation shielding and thermal conductivity tests were performed on the foams with different wall orientations with respect to the probing directions. The neutron radiation test results revealed excellent radiation shielding properties with an orientation-dependent shielding behavior. The neutron shielding effectiveness or mass absorption coefficient of the BNNP foams with walls perpendicular to the radiation source was significantly higher than those with a parallel configuration. Similarly, Flash Diffusivity studies revealed that the thermal conductivity of the foam with walls parallel to the heat source was much greater than those with a perpendicular configuration. The BNNP foam in this study has the potential to benefit advanced tailorable radiation shielding and thermal management for future aerospace missions.