Synthesis of ReB2-Al2O3 composite powders and chemical resistance of the products to moisture

Abstract

Synthesis of composite material from the ReO2 + Al2O3 + Al + B2O3 mixture was carried out. Mixtures were annealed at 1150 °C for 1 h or in two-steps process at 1050 °C and 1150 °C for 4 h, in argon. Different B2O3/ReO2 molar ratios were adopted: 1.0; 1.3; 1.5; 1.8; 2.0; 2.3, 2.5; 2.8; 3.0. The TG/DTA analysis was performed for the synthesis of mixtures of different molar ratios. Produced materials were tested by XRD phase composition studies. In every mixtures, products consisted mainly of ReB2, Al2O3, Re7B3 and aluminum borides. The research was aimed at reducing the share of the Re7B3 phase. Increase of the B2O3/ReO2 molar ratio in the syntheses results in the formation of boromullite phases such as Al5BO9, Al18B4O33, Al4B2O9. XRD and XPS investigations were carried out after prolonged exposure to humidity. Materials produced at a molar ratio B2O3/ReO2 = 1 are characterized by greater resistance to water from moisture compared to other tested mixtures.