Preparation of AlN polycrystalline plate from aluminum plate

AlN was produced by nitriding electrolytically etched aluminum plate. It was found that the plate shape did not change. (100) Oriented aluminum plate (18×50×0.1 mm in size, 99.99% in purity) was suitable for the conservation of plate shape. Electrolytic etching and preheating at 600°C in N2 flow are essential for the complete nitriding. Although nitriding temperature (1100–1400°C) was much higher than the melting point of aluminum, the plate was completely nitrided without the destruction of shape. The surface film of aluminum oxide, which was formed by a trace amount of oxygen in N2 gas, conserved the plate shape during nitriding. The relative density of product was increased to 91% by sintering at 1800°C for 2 h.