Development of non-oxide ceramic matrix composites based on reactive infiltration and in situ growth of AlN bonding phase

• Main Author: KEVORKIJAN, V. M
• Format: Conference Proceeding
• Language: English
• Subjects: Applied sciences; Building materials. Ceramics. Glasses; Ceramic industries; Chemical industry and chemicals; Exact sciences and technology; Structural ceramics; Technical ceramics
• ISSN: 1013-9826; 1662-9795

Novel CMCs were prepared by reactive infiltration of porous (50-70% theoretical density) ceramic preforms and in situ growth of an AlN bonding phase (10-35 vol%) from molten Al alloys. The continuity of the forming phases results in a very favourable balance of both physical and mechanical properties. Moreover, because the composites have a continuous Al phase (5-15 vol%), they exhibit some traditional macroscopic plasticity, despite being approximately 70 vol% ceramic. Preforms with optimal porosity and permeability were prepared by conventional ceramic processes using commercially available AlN, SiC and Si3N4 powders. Different non-oxide species were selected in order to demonstrate the flexibility of the preparation route. Wetting-assisted pressureless infiltration of Al into the preforms was achieved in nominally pure N2 or under an Ar atmosphere at temperatures between 850 C and 1200 C. The AlN bonding phase was prepared by displacement reactions between Al and selected commercially available nitrides (Si3N4, Mg3N2, Zn3N2, 325 Mesh powders) previously deposited on the surface of the porous ceramic body. Composite growth rates between 0.4-0.6 mm/min were observed and correlated with the interfacial reaction enthalpy change. The hardness, Young's modulus, compressive and flexural strength, and toughness of the composites with the same ratio of forming phases were determined. 3 refs.