Bubble growth in the preparation of mesophase-pitch-based carbon foams
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摘要: 以AR合成中间相沥青为原料，在不同的温度下发泡制得了泡沫炭。采用扫描电镜和光学显微镜等分析手段对中间相沥青基泡沫炭的气泡生长机理进行了初步研究，讨论了温度对泡孔结构的影响。结果表明，当温度从480℃升至540℃时，平均泡孔直径从500μm升到800μm。最初形成的泡沫在熔融沥青中分布不均匀，汇集在沥青的上表面；气泡在Z轴方向的形状是椭球形，在Z轴垂直方向为球形。中间相沥青基泡沫炭气孔的形状和泡沫的体积密度密切相关。形成的泡沫体在Z轴方向存在明显的体积密度梯度。Abstract: A synthetic mesophase pitch from naphthalene was used as a precursor to prepare carbon foams under different temperatures in order to study the bubble growth process and the effect of temperature on the bubble shape during the formation of carbon foams. Scanning electron microscopy and optical microscopy were used to analyze the microstructure of the as-prepared foams. Results show that the bubble size increases from 500µm to 800µm when the temperature increases from 480℃ to 540℃. The initial bubbles are not uniformly dispersed in the molten pitch, but start to grow at the upper section of the pitch. The cross-section bubble shape in the direction of gravitational forcey is elliptical but perpendicular to the direction it is circular. The non-spherical shape of the bubble is closely related to the bulk density of the mesophase-pitch based carbon foams, and there is a bulk density gradient in the Z direction of the as-prepared foam.
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