Ximin Zhang

Thermal Properties of Carbon Nanotube–Copper Composites for Thermal Management Applications

Carbon nanotube–copper (CNT/Cu) composites have been successfully synthesized by means of a novel particles-compositing process followed by spark plasma sintering (SPS) technique. The thermal conductivity of the composites was measured by a laser flash technique and theoretical analyzed using an effective medium approach. The experimental results showed that the thermal conductivity unusually decreased after the incorporation of CNTs. Theoretical analyses revealed that the interfacial thermal resistance between the CNTs and the Cu matrix plays a crucial role in determining the thermal conductivity of bulk composites, and only small interfacial thermal resistance can induce a significant degradation in thermal conductivity for CNT/Cu composites. The influence of sintering condition on the thermal conductivity depended on the combined effects of multiple factors, i.e. porosity, CNTs distribution and CNT kinks or twists. The composites sintered at 600°C for 5 min under 50 MPa showed the maximum thermal conductivity. CNT/Cu composites are considered to be a promising material for thermal management applications.

Microstructure and thermal conductivity of copper matrix composites reinforced with mixtures of diamond and SiC particles

The thermal conductivity of diamond hybrid SiC/Cu, diamond/Cu and SiC/Cu composite were calculated by using the extended differential effective medium (DEM) theoretical model in this paper. The effects of the particle volume fraction, the particle size and the volume ratio of the diamond particles to the total particles on the thermal conductivity of the composite were studied. The DEM theoretical calculation results show that, for the diamond hybrid SiC/Cu composite, when the particle volume fraction is above 46% and the volume ratio of the diamond particles to the SiC particles is above 13:12, the thermal conductivity of the composite can reach 500 W·m−1·K−1. The thermal conductivity of the composite has little change when the particle size is above 200 μm. The experimental results show that Ti can improve the wettability of the SiC and Cu. The thermal conductivity of the diamond hybrid SiCTi/Cu is almost two times better than that of the diamond hybrid SiC/Cu. It is feasible to predict the thermal conductivity of the composite by DEM theoretical model.

Microstructure and thermophysical properties of SiC/Al composites mixed with diamond

Abstract The thermophysical properties of the SiC/Al composites mixed with diamond (SiC-Dia/Al) were studied through theoretical calculation and experiments. The thermal conductivity and the thermal expansion coefficient of the SiC-Dia/Al were calculated by differential effective medium (DEM) theoretical model and extended Turner model, respectively. The microstructure of the SiC-Dia/Al shows that the combination between SiC particles and Al is close, while that between diamond particles and Al is not close. The experimental results of the thermophysical properties of the SiC-Dia/Al are consistent with the calculated ones. The calculation results show that when the volume ratio of the diamond particles to the SiC particles is 3:7, the thermal conductivity and the thermal expansion coefficient can be improved by 39% and 30% compared to SiC/Al composites, respectively. In other words, by adding a small amount of diamond particles, the thermophysical properties of the composites can be improved effectively, while the cost increases little.

Electronic packaging materials prepared by powder injecting molding and pressure infiltration process

Abstract AlSiCp (65 vol.% SiC) electronic packaging materials were manufactured by powder injection molding (PIM) and pressure infiltration process in order to obtain near net-shaped parts. SiCp preformed compacts obtained by pre-sintering process at 1150 K have high strength and good appearance, and the ratio of open porosity to total porosity is nearly 98%. The relative density of composites is bigger than 99%. The thermal conductivity of AlSiCp composites fabricated by this method is 198 W.m −1 .K −1 , and the coefficient of thermal expansion (CTE) is 8.0 x 10 −6 /K (298 K).