冰模板法制备取向氮化硼@聚多巴胺/纳米银导热网络及其硅橡胶复合导热垫片

Preparation of oriented boron nitride@polydopamine/nanosilver network and silicone rubber thermally conductive composite by ice template method

制备具有垂直方向高导热、低压缩应力松弛的柔性导热复合材料,并将其应用于大功率电子元器件的导热垫片,对大幅度提升电子器件垂直散热能力具有重要的意义。本文基于冰模板法设计了自下而上垂直定向排列的导热网络来实现高热导率。首先,利用多巴胺改性的羟基化氮化硼纳米片并负载银纳米颗粒(BNNS@PDA/Ag)作为杂化导热填料,再与纤维素纳米纤维(Cellulose nanofiber,CNF)进行复合,采用半导体制冷台为冷源进行定向冷冻,对冷冻后的样品进行冷冻干燥形成气凝胶,再真空浇筑聚二甲基硅氧烷(Polydimethylsiloxane,PDMS)后制得具有高导热和低应力松弛的BNNS@PDA/Ag-PDMS导热垫片。结果表明,理论松弛时间损失随着银纳米颗粒(Ag NPs)含量的提升先减小后增大,气凝胶质量分数达到19.7wt%时,在20%的形变下,3wt%Ag NPs含量对应的导热垫片的理论松弛时间达到32 204 s,导热垫片的垂直方向热导率达到3.23 W/(m·K)。利用冰模板法可以制备具有高度取向的垂直填料导热网络,在导热垫片领域具有很好的应用前景。

The preparation of thermally conductive pads with high vertical thermal conductivity and low compressive stress relaxation is of great significance for improving the vertical heat dissipation capability of current highpower electronic components. In this paper, based on the ice template method, a bottom-up vertically oriented thermal network is designed to achieve high thermal conductivity. First, we use dopamine-modified hydroxylated boron nitride nanosheets and silver nanoparticles(BNNS@PDA/Ag) as hybrid thermally conductive fillers, cellulose nanofibers(Cellulose nanofiber, CNF) are used to prepare composite, and a semiconductor is applied as refrigeration table for the composite’s directional freezing. The frozen samples are freeze-dried to form an aerogel, and then polydimethylsiloxane(PDMS) is vacuum poured into the aerogel to prepare BNNS@PDA/Ag-PDMS thermal pad with high thermal conductivity and low stress relaxation. The results show that the theoretical relaxation time loss decreases first and then increases with the increase of silver nanoparticles(Ag NPs) content. When the aerogel mass fraction reaches 19.7wt%, the theoretical relaxation time of the thermal pad corresponding to 3wt% Ag NPs content reaches 32 204 at 20% deformation, the vertical thermal conductivity of thermal pad is up to 3.23 W/(m·K).The ice template method can be used to prepare the vertical packing thermal network with high orientation, which has a good application prospect in the field of thermally conductive pads.