3.3. Influence of gel system on temperature difference
Temperature differences between the center and surface of alumina spheres prepared by PIBM and epoxy-amine at a heating rate of 0.5 °C/min were separately displayed in Fig. 2(b). The variation of the temperature difference in Al–EA sphere was more complicated than that in Al–PIBM sphere with the same solids loading (50 vol%). For the Al–EA sphere, the temperature difference was 12 °C when the furnace temperature rose to 150 °C, which was lower than that (23 °C) in Al–PIBM sphere. We attributed this SR 2211 to the denser microstructure of Al–EA sphere because of more organic additions. Therefore, synapsis seemed that organics in Al–EA sphere contributed to heat transfer.
With the furnace temperature over 200 °C, three peaks occurred in the temperature difference curve of Al–EA sphere (Fig. 2b), two of which were at 290 °C and 350 °C, respectively. The most prominent one was at 520 °C, where the center temperature was much higher than that of the surface. After that, the temperature difference rapidly reversed to a stable value. For example, the surface temperature was 15 °C higher than the center temperature with furnace temperature.