Achieving vertically aligned SiC microwires networks in a uniform cold environment for polymer composites with high through-plane thermal conductivity enhancement

Pre-constructing vertically aligned 3D thermally conductive fillers networks via unidirectional freeze casting method to prepare polymer composites with high through-plane thermal conductivity (TC) has recently attracted much attention. Here we proposed a strategy to fabricate anisotropic silicon carbide microwires (SiCMWs) networks in a uniform cold environment. The key point of our strategy was to design and make the anisotropic molds composed of materials with very different TC. We used a cuboid mold made of alumina sheets as top and bottom and PVC foam plates as side surfaces to fabricate vertically aligned SiCMWs networks in a cryogenic refrigerator. After impregnating of the networks into epoxy matrix , the obtained composites exhibited significant TC enhancement at an ultralow loading. The composite containing only 1.32 vol % of SiCMWs had a TC value of 0.62 W/(m K), which was 3.9 and 2.3 times that of pure epoxy and epoxy composite with random SiCMWs, respectively. Moreover, utilizing our method, the 3D networks with different orientation direction, dimensions or shapes could be also easily prepared only by designing and utilizing different molds.