Preparation Of Mesophase Pitches And Carbon Foams

Science and technology is the basic impetus of civilization. New materials determine the new technologies. In the movement, new materials with good properties appear constantly. As a new kind of carbon materials with high thermal conductivity, mesophase pitch based carbon foams have special structures, excellent properties and have broad foreground in aviation, spaceflight and many high-technology fields. The research and application of the material has been a focus of attention since it came out.The excellent properties of the mesophase pitch based carbon foams are because of their perfect cell structure. Frothing process and properties of precursors decide the pore size distribution and the hole-opening states. Mesophase pitches were prepared by using the traditional pyrocondensation method. Then the obtained mesophase pitches were used as precursors to prepare carbon foams by self-volatilization way. After coking, carbonizing and graphitizing carbon foams were gained. On the base of researching the preparation processes of mesophase pitches and carbon foams, the text researched the effect of different coking conditions (coking 4h and 10h respectively), precursors with different mesophase content (mesophase content 30% and 100% respective) and precursors with different properties (mesophase content 100%, softening point 295℃and 335℃respective) to the structure and properties of the carbon foams. SEM, XRD and optical microscopy were used to characterize the microstructure and structure parameter of the obtained carbon foams.The research shows that the structure and properties of the carbon foams can be controlled by foaming pressure, temperature, coking time and the properties of the mesophase pitch precursors. The carbon foams with long time coking have better molecular orientation and higher graphite degree (86%); the carbon foams can be prepared by precursors whose mesophse content is not 100% also but the foaming conditions are not easily controlled and the effect of the foaming is not perfect. Mesophase pitch prepared by our lab can get carbon foams with well-proportioned pores easily in a broad temperature range (430~500℃). Carbon foams prepared from the lower softening point mesophase pitch has better foaming properties: larger pore size (350~950μm), thinner hole-wall, higher porosity (83%~90%), better uniformity of pore size and molecular orientation, higher degree of graphitization.