Bubble growth in the preparation of mesophase-pitch-based carbon foams

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.