碳包钴纳米颗粒/聚二甲基硅氧烷复合热界面材料的制备和性能

为了制备具有良好的热导率、热稳定性、导电性和柔顺性的纳米颗粒填充硅树脂复合材料,首先以乙基封端聚二甲基硅氧烷(PDMS)为基体材料,以碳包钴纳米颗粒(C@Co)为填料,采用研磨共混法制备了C@Co/PDMS复合热界面材料。然后,运用TEM、XRD、Raman和SEM分别对C@Co的微观结构、物相、石墨化程度和分散性进行了研究。最后,研究了C@Co含量对复合热界面材料的热导率、热稳定性、导电性和柔顺性的影响。结果表明:该复合热界面材料的热导率随着C@Co含量的增加而增大,当C@Co的含量为24wt%时,复合材料的热导率达到最大值1.64 W/(m·K),比纯PDMS的提高了10.7倍;TG分析表明,添加24wt%的C@Co后,复合材料的起始分解温度和最终分解温度比纯PDMS的分别提高了约70℃和80℃,说明C@Co能提高复合材料的热稳定性;随着C@Co含量的增加,复合热界面材料的电导率非线性增大,拟合试差计算的逾渗阀值为10wt%,即C@Co含量小于10wt%时复合材料的绝缘性良好,而填充24wt%的C@Co时复合材料的电导率为9.38×10-3 S·m-1;复合材料的硬度适中,处于17.6~26.8HA范围内,表明该复合材料的柔顺性较好。因此,24wt%C@Co/PDMS复合材料不仅能满足热界面材料电性能的基本要求,且具有良好的热导率、热稳定性和柔顺性。

Preparation and properties of carbon coated cobalt nanoparticles/polydimethylsiloxane composite thermal interface materials

In order to prepare the nanoparticles filling silicone composites with favorable thermal conductivity, thermal stability, electrical conductivity and flexibility, vinyl terminated polydimethylsiloxane (PDMS) was used as matrix material and carbon coated cobalt nanoparticles (C@Co) was used as filler, C@Co/PDMS composite thermal interface materials were prepared by ground co-blend method firstly. Then, TEM, XRD, Raman, and SEM were employed to investigate the microstructure, phase, degree of graphitization and dispersibility of C@Co. Finally, the effects of C@Co content on thermal conductivity, thermal stability, electrical conductivity and flexibility of composite thermal interface materials were investigated. The results show that the thermal conductivity of the composite thermal interface materials increases with the C@Co content increasing, when the C@Co content is 24wt%, the thermal conductivity of the composite reaches the maximum 1.64 W/(m·K), which is 10.7 times higher than that of neat PDMS. TG analysis indicates that after the addition of 24wt% C@Co, the initial decomposition temperature and final decomposition temperature of composites increase about 70 ℃ and 80 ℃ comparing to that of the neat PDMS respectively, accounting for C@Co can enhance the thermal stability of the composites. With the C@Co content increasing, the electrical conductivity of the composite thermal interface materials increases nonlinearly, and the percolation threshold value of fitting trial and error calculation is 10wt%, which means that when the C@Co content is less than 10wt%, the insulativity of composite is favorable; but when filled with 24wt% C@Co, the electrical conductivity of composite is 9.38×10^-3 S·m^-1. The hardness of composites is moderate, which is in the range of 17.6-26.8 HA and indicates that the flexibility of the composite is preferable. Therefore, 24wt% C@Co/PDMS composite can not only meet the basic requirements of the electrical properties of thermal interface materials, but also have favorable thermal conductivity, thermal stability and flexibility.