前驱体对炭泡沫孔结构的影响

分别以煤沥青、石油中间相沥青和AR沥青为前驱体制备炭泡沫材料。采用GPC测定前驱体分子量,SEM观察所制炭泡沫的孔结构,光学显微镜测量所制炭泡沫的孔径及其分布。结果发现,由于煤焦油沥青不含中间相,且QI含量较高,导致在实验条件下不能直接制备出合格的炭泡沫。以石油中间相沥青和AR沥青为原料均能制备出具有分布均匀开孔结构,且微观各向异性的炭泡沫。由AR沥青制备的炭泡沫呈现平均孔径较小(212μm)、孔壁较薄、孔径分布较窄(180μm~300μm)、开孔率较高、以及韧带排列较规整等特点,表明低QI含量、低分子量且分布较窄的前驱体有利于发泡。

Effect of precursor on the pore structure of carbon foams

Carbon foams were prepared from coal tar pitch, petroleum mesophase pitch, and AR pitch. The molecular weights of the precursors were determined by gel permeation chromatography. Foam structure, average pore diameter and pore diameter distribution were investigated by scanning electron and optical microscopy. It was found that coal tar pitch could not be used as-received to prepare useful carbon foams because of their higher quinoline insoluble (QI) fraction. The carbon foams with homogeneous open pores and microscopic domains were obtained from AR pitch and petroleum mesophase pitch. Carbon foams prepared from AR pitch exhibited a smaller average pore diameter (212 μm),thinner cell walls, a narrower pore diameter distribution ( 180 -300 μm), higher open-cell ratio, and better ligaments compared with those from the other pitches. It is concluded that a precursor with low molecular weight, narrow molecular weight distribution, and low QI content is favorable for the preparation of carbon foams.