Direct Synthesis of Carbon Nanotubes on Alumina Powder by Rotary CVD for Improved Thermal Management Performance

The increasing demand for high performance electronic devices and the rapid growth of the electric vehicle market have highlighted the importance of efficient thermal management. Effective heat dissipation is critical to ensure the safety, longevity, and reliability of semiconductor devices and batteries. To address these challenges, polymer-based composites with thermally conductive fillers have emerged as a cost-effective solution. In this study, we developed nanocomposites composed of carbon nanotubes (CNTs) grown directly on the surface of alumina (Al₂O₃) particles with the aim of producing high-performance thermal fillers for polymer composites. A rotary chemical vapor deposition (RCVD) system, which incorporates a rotating reactor in conventional horizontal CVD, was used to improve the uniformity and mass production of the CNT/Al₂O₃ nanocomposites. This approach provides efficient dispersion of the CNTs within the polymer matrix, which enhances the reliable thermal performance of the produced composites.<br/>Key process parameters for CNT synthesis, such as reaction temperature, time, and reactor rotation speed, were optimized to maximize CNT yield. Structural characterization of the composites was characterized using scanning electron microscopy and transmission electron microscopy. In addition, Raman spectroscopy was used to evaluate the structural integrity of the CNTs. Thermogravimetric analysis was also used to quantify the CNT growth yield. Additionally, the incorporation of blades on the inner wall of the quartz reactor significantly increased the uniform and enhanced exposure of the Al₂O₃ particles to the hydrocarbon feedstock to improved CNT yield and crystallinity in the nanocomposites compared to the case without blades. The reactor configuration ensures efficient and uniform dispersion of CNTs within the polymer matrix, ultimately improving the thermal performance of the composites.<br/>To confirm the performance of the synthesized CNT/Al₂O₃ nanocomposites as fillers for enhanced thermal conductivity, the CNT/Al₂O₃ powders were dispersed into epoxy resin to fabricate polymer composite sheets. Thermal conductivity was measured using a laser flash analysis, with the results were directly compared to polymer composites made of either pure Al₂O₃ or commercial CNT/Al₂O₃ mixtures. The superior thermal properties obtained from the composites produced by direct growth of CNT confirm the effectiveness of this scalable synthesis for thermal management applications.