Temperature effect on nonhydrolytic foaming process
Published online by Cambridge University Press: 31 January 2011
This paper describes the effect of temperature on the formation of nonhydrolytic alumina foams. The foams are generated by heat treatment of crystals of the aluminum chloride isopropyl ether complex [AlCl3(Pri2O)], with the release of isopropyl chloride (PriCl). The chlorine content in the 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 modeled. The foaming time ranged from several minutes at 70 °C to several seconds at 160 °C. It was found that the chlorine-to-aluminum ratio of the foam (Cl/Al) decreased from 1.79 at 70 °C to 1.56 at 160 °C. Thermogravimetric analysis data confirm that the smaller Cl content gives rise to a smaller weight loss during thermal decomposition, consistent with a higher CD in the foams created at higher temperatures. Finally, about 80% of the PriCl produced during complex decomposition and subsequent –Al–O–Al– condensation reactions is lost during foaming.
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