Sintering Behavior and Fracture Morphology of NiFe2O4/Nano-TiN Ceramics Synthesized under Argon Atmosphere

NiFe 2 O 4 /nano-TiN ceramics were synthesized by a two-step cold-pressing sintering process. Sintering behavior, fracture morphology, mechanical performance and high-temperature conductivity were investigated. The results indicated that besides NiO and NiFe 2 O 4 , new Ni 3 TiO 5 and metallic phases (iron and nickel) formed in the sintered samples. TiN accelerated the grain growth along with considerable quantity of micro-pores in the sintered samples. Compared to the un-doped samples, the temperature for the onset of sintering of the NiO-Fe 2 O 3 -2.0 wt.% TiN system decreased from 1093 to 985  °C. TiN addition changed the sintering mechanism of the NiO-Fe 2 O 3 from grain boundary diffusion to volume diffusion. TiN additions reduce the apparent sintering activation energy and porosities and improve the density, bending strength, and pyroconductivity. Three-dimensional fracture morphology of the composite ceramics synthesized under argon atmosphere, exhibits self-similarity characteristics and the fractal dimension for NiFe 2 O 4 -1.0 wt.% TiN ceramics is 2.0813.