孔隙密度对化学气相沉积泡沫金刚石导热性能的影响

Effect of pore density on thermal conductivity of CVD diamond foam

选择不同孔隙密度的泡沫铜为沉积衬底,通过化学气相沉积(chemical vapor deposition,CVD)技术在其表面沉积连续金刚石膜,借助有限元模拟阐释泡沫骨架的孔隙密度对金刚石膜整体传热效果的影响,并通过扫描电镜、拉曼光谱及红外热成像仪等对不同孔隙密度的泡沫金刚石微观形貌、膜层成分以及热扩散性能进行对比与分析。结果表明:高孔隙密度泡沫衬底更有利于热量传递,但其极小的泡沫孔径会限制自由基在孔隙内部流动,CVD沉积的金刚石晶粒尺寸明显减小,仅有2~3μm,晶粒质量也略逊于中、低孔隙密度样品的。在相同加热时间内的红外热成像中,中孔隙密度泡沫金刚石的表面升温速率相比低、高孔隙密度样品的升温速率分别提升43.4%与12.7%。综上所述,兼具良好三维连通特性与优异金刚石质量的中孔隙密度泡沫金刚石表现出更为优异的导热性能,是更理想的导热增强体选择。

Copper foams with different pore densities were chosen as the substrate to deposit the continuous diamond film on the surface by chemical vapor deposition(CVD) technology.The influence of the pore density of the foam skeleton on the overall heat transfer effect of the diamond film was explained by finite element simulation.The scanning electron microscope,the Raman spectrum and the infrared thermal imager were used to compare and analyze the micro morphology,the film composition and the thermal diffusivity of diamond foam with different pore densities.The results show that high pore density foam substrate is more conducive to heat transfer,but its tiny pore size limits the flow of free radicals in the pores,and the size of diamond grains deposited by CVD is significantly reduced,with only 2~3 μm.The grain quality is also slightly inferior to that of medium and low pore density samples.In the infrared thermal imaging with the same heating time,the surface heating rate of the medium pore density diamond foam is higher than that of the high and low void density samples,which increases by 43.4% and 12.7%,respectively.In summary,the diamond foam with excellent three-dimensional connectivity and excellent diamond quality has excellent thermal conductivity,and is a better choice of heat conduction reinforcement.