A self-propagating high-temperature synthesis method for synthesis of AlN powder
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A self-propagating high-temperature synthesis method for synthesis of AlN powder Shyan-Lung Chung,a) Wen-Liang Yu, and Chun-Nan Lin Department of Chemical Engineering, National Cheng Kung University, Tainan, Taiwan, 70101, Republic of China (Received 25 October 1997; accepted 22 November 1998)
A new self-propagating high-temperature synthesis (SHS) process has been developed for synthesis of AlN powder under low nitrogen pressures. Al and NH4 X (X F, Cl, Br, or I) powders were mixed and pressed into a compact, which was placed in a reaction chamber filled with nitrogen. The combustion synthesis reaction was ignited by heating directly the compact, and high product yields (,90%) were obtained under nitrogen pressures of around 0.5 MPa. The product yield was affected by the reactant composition, the nitrogen pressure, and the compact-forming pressure. The powder as synthesized consists mainly of fibers, coarse granules, and agglomerated fine particles, which become mostly smaller than 10 mm after grinding. A reaction process was also proposed that explains the effects of the experimental parameters on the product yield.
I. INTRODUCTION
Aluminum nitride has been acknowledged as a very important ceramic material in industrial applications due to its high thermal conductivity, high electrical resistivity, low thermal expansion coefficient, good thermalshock resistance, and good corrosion resistance.1,2 It has been considered for many applications, such as electronic substrates, packaging materials for integrated circuits, heat sinks, high thermally conductive composite materials, and hardware for containing or processing molten metals and salts.1,3 Although many processes have been developed for manufacturing AlN powder,4,5 development of new processes for producing AlN powder at low cost is still an interesting research topic. Our research objective is to investigate the use of the combustion synthesis (SHS) method for the production of AlN powder. The SHS method, originally developed in the former USSR,6 has been applied to synthesis of various materials including ceramics, intermetallics, and composites. It has many potential advantages such as low processing cost, energy efficiency, and high production rate.7 In our previous study,8 a SHS method was developed for the synthesis of AlN powder by using Al and NaN3 as the reactants. By wrapping up the reactant compact with aluminum foil and an igniting agent (i.e., Ti 1 C), high product yields were obtained at low nitrogen pressures (%0.5 MPa). Although the wrappings were found to be essential to achieve high product yields in the process, their use makes the manufacturing procedure more complicated.
a)
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1928
http://journals.cambridge.org
J. Mater. Res., Vol. 14, No. 5, May 1999
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An attempt was thus made to improve the process so as to eliminate the use of the wrappings. It was found that by using Al and NH4 X (X F,
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