Mechanochemical effect for some Al2O3 powders by attrition milling

Abstract

As part of work to elucidate the mechanochemical effect for various ceramic powders, the mechanochemical effect for some A120 3 powders has been examined by a vibration ball mill under dry and wet conditions [1-4]. Mechanochemical factors such as crystallite size, lattice strain and effective temperature factor of the specimens changed significantly with milling time. The values of mechanochemical parameters after prolonged grinding were found to vary not only with grinding condition but also with specimens [3-5]. In this paper, the same powders as reported earlier [3, 4] were ground by an attrition mill and the variation of mechanochemical factors with milling time was examined and compared with the results obtained by vibration ball milling. The three kinds of A1203 powders as used previously [3, 4] were used as the starting materials. Their characteristics were as follows: (1) specimen (0.6/xm) low soda A1203 with an average particle size 0.6/xm (LS21, Nippon Light Metal Co. Ltd); (2) specimen (3.9/xm) low soda A1203 with an average particle size 3.9/xm (LS21, Nippon Light Metal Co. Ltd); (3) specimen (22/xm) electrofused A120 3 with an average particle size 22/xm (WA600, Showa Denko Co. Ltd). Crystalline phase detected in specimen (0.6/xm) and specimen (3.9/xm) was only ol-A120 3 whereas /3-A1203 and ol-A1203 were detected in specimen (22/xm) by X-ray diffraction (XRD). Milling was performed using an attrition mill (Attritor S; Mitsui Miike Kakohki Co. Ltd). A hard plastic pot was used, with inner volume 650 ml. Agitator arms and grinding balls used were made of alumina ceramics. The charge for grinding experiments was 700 g of Al;O3 balls 2 mm in diameter, 120 g of ethanol and 30 g of specimen. The rotation speed of the agitator arm was set to 300 r.p.m. After a set milling time, i.e. 0.5-48 h, all specimens were collected and used for the various experiments. Particle size distribution was measured by a Microtrack instrument (Nikkiso Co. Ltd) dispersing the specimen ultrasonically in an aqueous solution adjusted to pH 2 by HC1. XRD measurements were made by a powder X-ray diffractometer (Geigerflex, Rigaku Co. Ltd) with graphite monochromated CuK~ radiation. X-ray intensities were measured by step scanning and fixed time methods. The step interval was 0.004 ° and the fixed time was 4 s. The