Al2O3/GdAlO3 reaction sintered composites produced from milled powders: Microstructure, neutron-capture cross section, and mechanical properties

The incorporation of high thermal neutron capture elements in ceramic materials is relevant for the design of traceable proppants for obtaining information in petrology, such as the location and height of fractures in unconventional gas and oil wells. Among these, GdAlO3 has attracted interest because of its good thermomechanical properties. In this work, four Al2O3/GdAlO3 reaction sintered composites were prepared using Gd2O3 and Al2O3 powders as raw materials and high-energy ball milling followed by sintering at 1600 degrees C. This combination of ball milling and reaction sintering is considered as a mechanism to produce large bulk ceramics with different Al2O3/GdAlO3 compositions. The composite formulations range from pure alumina to eutectic ceramic. The obtained materials were characterized using X-ray diffraction for identifying the crystalline phases, Archimedes method for the textural properties, scanning electron microscopy for the microstructure, and Vickers indenter and three-point bending tests for the mechanical properties. In addition, the macroscopic capture crosssection sigma for thermal neutrons was estimated considering each composite formulation. It was found that the processing route is very suitable for producing low-porosity Al2O3/GdAlO3 composites, which present similar mechanical properties to those of alumina. Both the material density and sigma increase with increasing the starting amount of Gd2O3, in a way that for the eutectic composite the density is 50% higher than that of pure alumina, and sigma is about 550000 c.u. The effect of the material porosity on sigma was also considered. The obtained results indicate that the proposed processing route is very attractive for producing these ceramic composites for technological applications.