Temperature effect on nonhydrolytic foaming process

This paper describes the effect of temperature on the formation of nonhydro lytic alumina foams. The foams are generated by heat treatment of crystals of the aluminum chloride isopropyl ether complex [AlCl3((Pr2O)-O-i)], with the release of isopropyl chloride ((PrCl)-Cl-i). The chlorine content in th e foams was determined by titration, and their weight loss during sintering was measured by thermogravimetric and differential thermal analysis. Based on these measurements, the condensation degree (CD) in the foams was model ed. The foaming time ranged from several minutes at 70 degrees C to several seconds at 160 degrees C. It was found that the chlorine-to-aluminum ratio of the foam (Cl/Al) decreased from 1.79 at 70 degrees C to 1.56 at 160 deg rees C. Thermogravimetric analysis data confirm that the smaller Cl content gives rise to a smaller weight loss during thermal decomposition, consiste nt with a higher CD in the foams created at higher temperatures. Finally, a bout 80% of the (PrCl)-Cl-i produced during complex decomposition and subse quent -Al-O-Al- condensation reactions is lost during foaming.