Microstructure and properties of aluminum nitride ceramics prepared by aqueous gelcasting method with nontoxic curdlan as gelling agent.

Aluminum nitride ceramics were prepared by aqueous gelcasting method and pressureless sintering technique in N 2 atmosphere using Y 2 O 3 as sintering additives with nontoxic curdlan as gel system. The solidification mechanism of curdlan was studied. The effects of curdlan content and solid content on the microstructure, relative density and flexural strength of green bodies were investigated. The influences of Y 2 O 3 content and sintering soaking time on the microstructure and properties of sintered bodies were also studied. The results show that, as the temperature increases to 80 °C, the ceramic powders solidify through three-dimensional gel networks of curdlan during gelling process. The green bodies can be successfully fabricated through aqueous gelcasting method with modified powder as original materials. Suitable curdlan content and solid content contribute to fabricating green body with uniform microstructures and high flexural strength. The relative density and flexural strength of sintered bodies enhance as the Y 2 O 3 content and soaking time increase. The flexural strength and thermal conductivity are about 107.5∼172.3 MPa and 75.2∼112.5 W/(m·K), respectively. The sintered body with 4 wt% Y 2 O 3 soaking for 3 h exhibits the highest thermal conductivity because of appropriate relative density, uniform microstructure and reasonable intergranular phase distribution. The mechanical property and thermal conductivity of sintered bodies can be improved by optimizing the gelcasting process parameter, Y 2 O 3 content, and soaking time. The nontoxic gelling system will have wide application for aqueous gelcasting ceramic with complex shape. Aluminum nitride (AlN) ceramics were prepared by aqueous gelcasting and pressureless sintering technique using Y 2 O 3 as sintering additives with curdlan as gel system. 1.5 wt% curdlan and 50 vol% solid content are conductive to fabricating AlN green body with uniform microstructures. The relative density, grain size and microstructures relate to the properties of AlN ceramics. [Display omitted] • AlN ceramics can be prepared by aqueous gelcasting and pressureless sintering method with curdlan as gel system. • 50 vol% solid content and 1.5 wt% curdlan content are benefit to prepare AlN green body. • Y 2 O 3 sintering additive not only realizes liquid sintering but also effectively promotes properties of AlN ceramic. [ABSTRACT FROM AUTHOR]