Effect of different parameters on porosity and compressive strength of coal tar pitch derived carbon foam

Carbon foams were prepared from coal tar pitch modified by treatment with concentrated nitric acid followed by foaming and carbonization. Effect of particle size of the precursor, heating rate during foaming and foaming time on the porosity and compressive strength was investigated. Precursor particle size was varied from 75 to 500 mu m. Heating rate during foaming was varied from 3 degrees C/min to 5 degrees C/min. Three foaming times of 1 h, 3 h and 5 h were also studied. Experiments show that fine particle was suitable for foaming as it yields higher strength compared to coarse particle. Three hour of foaming time was sufficient for foaming. Heating rate of 3 degrees C/min resulted in higher bulk density and compressive strength than that of 5 degrees C/min. Carbon foam of 0.56 g/cc bulk density along with 35.45 MPa compressive strength and 71% porosity is obtained by using 75-mu m particle and 3 degrees C/min heating rate with 3 h of soaking time. True density of the foams was obtained by helium pycnometry. Compressive strength and morphology was tested in universal strength testing machine and scanning electron microscope respectively.