Abstract
The process of carbothermal reduction of Al2O3 in a nitrogen flow at temperatures of 1450 and 1600?C has been studied. It was established that the powder synthesized at 1450?C is a mixture of Al2O3 and AlN particles and that the powders synthesized at 1600?C are mixtures of AlN, AlON, and Al2O3. Amorphous and crystalline AlON films form on the surface of Al2O3 and AlN particles. Both synthesized powders contain unreacted residual carbon. In the stage of high-pressure sintering of specimens at a temperature of 1750?C under a pressure of 7 GPa for 110 s, AlON decomposes into AlN and Al2O3. Residual graphite transforms into a crystalline graphite phase, which decreases the strength and increases the fracture toughness. The highest hardness of 19.5 GPa was achieved in the ceramics obtained from the powder synthesized at 1600?C for 4 h, and the largest fracture toughness of ~7.2 MPa?m1/2 was achieved in the ceramics obtained from the powder synthesized at 1450?C for 4h.
Highlights
Considerable attention has been given to the synthesis of composite nanopowders based on Al2O3, AlN, and AlON due to unique properties of composite ceramics of the Al2O3–AlN––AlON system
According to the X-ray diffraction (XRD) data, the powder synthesized at 1450 oC for 4 h, contains two crystalline phases AlN and Al2O3 (Fig 1 a)
In the powder synthesized at 1600 oC for 3 h (Fig. 1 b), the main phases are AlN and AlON, and in the powder synthesized at 1600 oC for 4 h (Fig .1 c), the AlON phase dominates, and the intensity of peaks of AlN is somewhat lower
Summary
Considerable attention has been given to the synthesis of composite nanopowders based on Al2O3, AlN, and AlON due to unique properties of composite ceramics of the Al2O3–AlN––AlON system. Each of these materials is extensively used as monophase structural materials. Aluminum oxide is one of the main ceramic packaging materials used for microelectronics. This ceramic has good electrical and mechanical properties [1]. Aluminum nitride ceramics has a sufficiently high thermal conductivity [4,5,6]. The spinel aluminum oxynitride (γ-AlON) ceramic is a stable
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