Effect of oxidative stabilization on the sintering of mesocarbon microbeads and a study of their carbonization

Graphite artifacts were prepared using mesocarbon microbeads (MCMBs) with two different extents of oxidation, lightly oxidized MCMBs (M-LO) and highly oxidized MCMBs (M-HO). Cold isostatic pressing at 200 MPa was used in the formation process. Physical properties of the obtained artifacts prepared with two raw materials are quite different, the reason can be found in their pyrolysis behavior and sintering behavior. Thermogravimetry–mass spectrometer results show that H2, CH4, CO2 and H2O are the common gaseous products, however, between 400 and 600 °C the M-LO may generate lightweight hydrocarbon component which was confirmed by thermogravimetry–infrared spectroscopy. A remarkable difference between the flexural strength of M-LO and M-HO was explained by the microstructure evolution observed with in situ scanning electron microscopy. For M-LO, cracks are mainly transgranular, giving little chance for interconnection, while in M-HO, cracks are mainly intergranular and may connect to form long cracks. A mechanism of crack formation caused by inhomogeneous shrinkage was proposed.