Sintering of nanopowders under high pressure

Stanisław Gierlotka 2Robert Fedyk 2Grzegorz Kalisz 2,3Ewa Grzanka 1,2Anna Swiderska-Sroda 2

1. Warsaw University, Faculty of Physics, Hoża 69, Warszawa 00-681, Poland
2. Polish Academy of Sciences, Institute of High Pressure Physics (UNIPRESS), Sokolowska 29/37, Warszawa 01-142, Poland
3. Warsaw University of Technology, Faculty of Materials Science and Engineering (InMat), Wołoska 141, Warszawa 02-507, Poland

Abstract

Ceramic materials with nanometer crystallite size are expected to play an important role in the technologies of the future. While search for an industrial-scale method of sintering of nanometric powders is still underway, laboratory-scale samples of nanoceramics can be effectively prepared by sintering under pressure. Using torroid-type high pressure equipment we sintered a range of nanometric powders of various chemical nature, such as YAG (yttrium aluminum garnet), GaN, SiC and others. Sintering pressures were in the range 2-8GPa, and sintering temperatures were selected according to the thermodynamic properties of the materials being sintered. I most cases compacts with almost 100% of the theoretical density could be obtained with the crystallite size in the sintered body nearly equal to that of the initial powder. Controlled grain growth could also be achieved. Hardness of the samples was equal, or sometimes even higher than the reference values. Parameters of the sintering process: pressure, temperate and time had a clear effect on the microstructure and physical properties of the compacts with temperature being the most critical factor. The way the starting powders were synthesized and the way the materials were treated before sintering also greatly influenced microstructure and thus the properties of the compacts. All samples sintered under exhibited considerable residual microstrain. Apart from general considerations a number of material-specific factors e.g. phase transitions were found to affect the sintering process. The compacts sintered were used to demonstrate specific properties of bulk nanomaterials not found in conventional ceramics.

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Presentation: oral at E-MRS Fall Meeting 2005, Symposium I, by Stanisław Gierlotka
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-05-08 12:27
Revised:   2009-06-07 00:44
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