TAILIEUCHUNG - ADVANCES IN CERAMICS SYNTHESIS AND CHARACTERIZATION, PROCESSING AND SPECIFIC APPLICATIONS_2

The current book contains twenty-two chapters and is divided into three sections. Section I consists of nine chapters which discuss synthesis through innovative as well as modified conventional techniques of certain advanced ceramics (. target materials, high strength porous ceramics, optical and thermo-luminescent ceramics, ceramic powders and fibers) and their characterization using a combination of well known and advanced techniques. | Part 2 Topics in Processing of Advanced Ceramic Materials 10 Last Advances in Aqueous Processing of Aluminium Nitride AlN - A Review . Olhero1 . Alves1 and . Ferreira2 department of Mechanical Engineering and Industrial Management FEUP University of Porto Porto department of Ceramics and Glass Engineering CICECO University of Aveiro Aveiro Portugal 1. Introduction Aluminium nitride AlN is a ceramic material that has been intensively studied in the last years due to its good thermal conductivity 319 W mK theoretical value low dielectric losses small dielectric consumption 4x 104 a thermal expansion coefficient matching that of silicon together with other physical properties that make AlN to be the most interesting substrate material for highly integrated microelectronic units Greil et al. 1994 Iwase et al. 1994 Knudsen 1995 Prohaska and Miller 1990 Sheppard 1990 . The most recent breakthroughs were achieved in the processing science field of the AlN namely on i replacing of the traditionally used organic solvents by water and ii decreasing the sintering temperatures AlN powder compacts through appropriately selecting the sintering additives and process optimization. Aqueous colloidal processing has been pursued by many authors along the most recent years as an alternative to alcoholic or other flammable and costly dispersion media. The advantages of aqueous processing are the healthier and more environmentally friend production at lower and more competitive costs which enables to increase and diversify the applications for the nitride-based ceramics. However nitride powders are susceptible to hydrolysis what is particularly true in the case of aluminium nitride AlN Bellosi et al. 1993 Osborne Norton 1998 Reetz et al. 1992 . In fact when AlN powder is hydrolysed by water undesirable aluminium hydroxydes are formed on the surface of particles with a concomitant increase of the oxygen content and the production and release of ammonia. Accordingly an .

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