Preparation of carbon materials by modeling of impregnating coal-tar pitch into carbon preform

Abstract

Using coal-tar pitch as a matrix precursor to prepare carbon materials is widely used by impregnation/carbonization processing technology. The primary QI, hard particles in liquid pitch at impregnation temperature, generally can deposit on the surface of the carbon preform and partly form a filter cake. The process can cause complex flow behaviors for liquid coal-tar pitch leading to impregnation models of metal or resin unsuitable to it. The flow of liquid coal-tar pitch in the carbon preform remains laminar as estimated by the Reynolds number. The open and closed pores in preform are regarded as vertical and transverse capillaries. Considering the size distributions of QI particles and open pores, two different kinetics models based on Darcy's law are proposed to describe impregnation mechanism of liquid coal-tar pitch into open pores. The kinetics formula for pitch infiltrating in closed pore is obtained also. The total impregnation efficiency model is obtained. The predicted results are in reasonable agreement with experiment data. Several effects of impregnation efficiency, including effective pressure, impregnation temperature, porosity of preform, dimension of pore and QI particles, are analyzed by the model to increase the technical understanding of such process. It is expected to optimize the operation parameters of impregnation.