Porosity and cell size control in alumina foam preparation by thermo-foaming of powder dispersions in molten sucrose

• Main Authors: Sujith Vijayan, Praveen Wilson, K. Prabhakaran
• Format: Article
• Language: English
• Published: Taylor & Francis Group 2016-09-01
• Series: Journal of Asian Ceramic Societies
• Subjects: Foaming temperature; Alumina; Porosity; Foams; Sucrose; Strength
• Online Access: http://www.sciencedirect.com/science/article/pii/S2187076416300379

The foaming characteristics of alumina powder dispersions in molten sucrose have been studied as a function of alumina powder to sucrose weight ratio (WA/S) and foaming temperature. The increase in foaming temperature significantly decreases the foaming and foam setting time and increases the foam volume due to an increase in the rate of OH condensation as well as a decrease in the viscosity of the dispersion. Nevertheless, the foam collapses beyond a critical foaming temperature, which depends on the WA/S. The sintering shrinkage depends mainly on the WA/S and marginally on the foaming temperature. The porosity (83.4–94.6 vol.%) and cell size (0.55–1.6 mm) increase with an increase in foaming temperature (120–170 °C) and a decrease in WA/S (0.8–1.6). The drastic decrease in compressive strength and modulus beyond a WA/S of 1.2 is due to the pores generated on the cell walls and struts as a result of particle agglomeration. Gibson and Ashby plots show large deviation with respect to the model constants ‘C’ and ‘n’, especially at higher alumina powder to sucrose weight ratios.