Three-dimensional (3D) carbon/carbon(C/C) composites with high thermal conductivity were prepared from a preform prepared by orthogonallyweaving continuous mesophase pitch-based fibers in the x and y directions andcommercial PAN-based carbon fibers in the z-direction, which were densified by three cycles of chemical vapor infiltration(CVI) and graphitization to a density of 1.58 g/cm³ (3CVI), followed by four cycles of liquid pressure impregnation (LPI), carbonization and graphitization to give a density of 1.84 g/cm³ (3CVI+4LPI). The effects of the microstructure and the relative contributionsof the fibers and matrix carbon to the thermal conductivity and mechanical properties of the C/C composites were investigated. Results indicate that the CVI pyrolytic carbon (PyC) is highly crystalline and oriented along the fiber axis. Thethermal conductivities of the 3CVI and 3CVI+4LPI C/C composites in the x-y plane are respectively 115.9and 234.7W/m·K, while those in the z-direction are only 18.6 and 41.5 W/m·K. The thermal diffusivity and thermal conductivity mainly depend on the fiber type, the volume fractions of the fibers and the type of pyrolytic carbon. The thermal conductivity of the composites is improved by increasing the volume fraction of pitch-based carbon fibers and using matrix carbon that is easily graphitized. The mechanical properties of the two C/C composites are greatly improved compared with those of 1D-C/C and 2D-C/C composites.

由预成型件制备高导热率的三维（3D）碳/碳（C / C）复合材料，该预成型件是通过在x和y方向上正交编织连续中间相沥青基纤维和在z方向上商用PAN基碳纤维制成的，分别通过三个化学气相渗透（CVI）和石墨化至密度为1.58 g / cm ³（3CVI）的循环进行致密，然后通过四个周期的液体压力浸渍（LPI），碳化和石墨化以达到1.84的密度克/厘米³（3CVI + 4LPI）。研究了微观结构以及纤维和基体碳对C / C复合材料的导热性和机械性能的影响。结果表明，CVI热解碳（PyC）高度结晶并沿纤维轴定向。xy中3CVI和3CVI + 4LPI C / C复合材料的热导率平面分别为115.9 W / m·K和115.9 W / m·K，而z方向的平面仅为18.6 W / m·K。热扩散率和热导率主要取决于纤维类型，纤维的体积分数和热解碳的类型。通过增加沥青基碳纤维的体积分数并使用易于石墨化的基质碳，可以提高复合材料的导热性。与1D-C / C和2D-C / C复合材料相比，两种C / C复合材料的机械性能得到了极大的改善。