abstract
Due to fast hydrolysis of AlN when in contact with water, AlN based ceramics are processed in organic solvents, which are volatile, expensive, harmful to the health and environment. The present work intends to protect AlN powder against hydrolysis in order to enable aqueous processing of AlN based ceramics. A commercial AlN powder was treated in an ethanol solution of H(3)PO(4) and Al(H(2)PO(4))(3) kept at 80 degrees C for 24 h to protect it from hydrolysis. The dispersing behaviour of the treated AlN powder in water and the ability to consolidate defect free parts of AlN and beta-Si(4)Al(2)O(2)N(6) ceramics from aqueous suspensions by slip casting and gelcasting techniques were studied. The consolidated parts were then sintered in a graphite furnace and the sintered bodies exhibited properties [bulk density (BD), apparent porosity (AP), crystalline phase composition and microstructural features] similar to those reported in literature for the same materials processed from organic media.
keywords
ALUMINUM NITRIDE POWDER; THERMAL-CONDUCTIVITY; AIN CERAMICS; HYDROLYSIS; DISPERSION; ADDITIVES; Y2O3
subject category
Materials Science
authors
Ganesh, I; Olhero, SM; Ferreira, JMF
our authors
José Maria da Fonte Ferreira
Retired Professor
Susana Maria Henriques Olhero
Assistant Professoracknowledgements
I. Ganesh thanks SERC-DST (Government of India) for the awarded BOYSCA5ST fellowship (SR/BY/E-04/06). S. M. Olhero wishes to thank to Foundation for Science and Technology (FCT) of Portugal for the financial support under the grant SFRH/BPD/27013/2006.