Preparation of graphitic carbon foam using size-restriction method under atmospheric pressure

摘要

Mesophase pitch can be manufactured into high-performance carbon fibers with light weight, high temperature stability and high thermal conductivity 1. However, the high thermal conductivity of mesophase pitch-based carbon fibers only occurs in the direction of fiber axis. Recently researchers used this kind of pitch to produce graphitic carbon foams 2,3. Due to the high open cell ratio, extreme low bulk density and high isotropic thermal conductivity, mesophase pitch-based graphitic carbon foams (MPCF) are expected to found extensive applications in thermal management systems 4-8. In previous literature 2-6, MPCF was prepared in sealed vessels under pressures and the cell size of foams was changed by adjusting the pressures. In this letter, a simple size-restriction method using vessel walls as barrier to produce pressures was firstly used to fabricate MPCF under atmospheric pressure and graphitic foams with uniform cells were obtained. A petroleum-derived mesophase pitch with softening point of 305 deg C was used as the precursor. The toluene-insolubles (TI) and quinoline-insolubles (QI) of the pitch are 98.3 wt. percent and 85.7 wt. percent, respectively. The solubility data indicates that there are some light components in the pitch, which will act as foaming reagent to produce bubbles and consequently cells in foaming mesophase pitch in the present experiments. Thermogravimetric analysis shows that the pitch begins to lose its weight obviously at 440 deg C and the maximum rate of weight loss occurs at 515 deg C, therefore, foaming temperature was set as 460 deg C to ensure the foaming but not excessive weight loss of the pitch.