2017 Volume 58 Issue 6 Pages 938-944
New heatsink materials having higher thermal conductivities have recently been required due to the recent rapid improvements in performance of the central processing unit, CPU, with increasing heat generation from computer devices. As an alternative material to conventional heatsink materials such as Al and Cu, composites containing carbon fibers have recently been gaining much attentions because of their extremely high thermal conductivity. However, carbon fiber exhibits high thermal conductivity only in its longitudinal direction. Therefore, it is essential to control the orientation of the carbon fibers in the composite materials. In the present study, hot extrusion of a powder–fiber mixture is applied to realization of unidirectional array of carbon fibers in Al matrix, and the effects of volume fraction of the carbon fibers on the thermal conductivity of the carbon fiber oriented Al–based composite have been investigated. It has been demonstrated that the carbon fibers are unidirectionally oriented in the extrusion direction, and the thermal conductivity in this direction increases with the increase in volume fraction of the carbon fibers. For the composites with more than 30 vol% of carbon fibers, the addition of Al–Si alloy powder or the application of the spark plasma sintering, SPS, before the extrusion was found to be effective for improving the sinterability of the powder–fiber mixture.
This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 80 (2016) 640–645.