Mechanical and dielectric properties of Al_2O_3/Ni cermet

Al2O3/Ni cermet were prepared by hot pressing,and the relationship between their microstructure,mechanical and dielectric properties with Ni particle content were investigated.The results show that some Ni particles are slightly elongated in the direction perpendicular to the pressing direction and are arranged in such away to form large but finite interconnected clusters which do not span the entire specimen up to a volume fraction higher than 20vol%.By increasing the amount of metal in the cermet,the relative density and the bending strength decreased gradually.For cermet,maximum fracture toughness values were 6.4MPa·m1/2 which increase 50% of the value for alumina.The complex dielectric constant measurements indicate that the real part and the loss increase greatly with the Ni content in the frequency of 8.2-12.4GHz.The imaginary part of dielectric constant of Al2O3-20vol%Ni is negative in value within specific frequency because a properly formed,well-bonded network of Nickel actually occurs.