Industrial aluminum nitride(AlN) powder was surface modified with organic carboxylic acid and polyethylene glycol (PEG) as surface modifier and the hydrolysis resistance and modifying mechanism of AlN powder before and after modification were studied.The results showed that the hydrolysis reaction to produce NH3 between AlN and H2O led to the rapid increase of pH value of aqueous solution and generation of much Al(OH)3.The surface coating organic carboxylic acid on AlN particles formed a diffusion barrier between water and AlN surface to improve the hydrolysis resistance of AlN. The pH value of AlN powder after modification slightly increased after soaking in water for 48h,but there was no obvious Al(OH)3 generation.The AlN powder after modification kept higher stability in aqueous ball milling at a high cutting stress.
With nano-SiC as matrix,nano-TiN as reinforcement phase,de-ioned water as dispersion medium,TMAH as dispersant and Y3Al5O12(YAG) as additive,nano-SiC based aqueous slurries were prepared,and the effects of solid phase content and dispersant content on rheological properties,dispersibility and stability of the slurries were analyzed.The results showed that shear viscosity and shear stress of aqueous SiC based slurries increased with the increase of solid phase content,and decreased with the increase of TMAH content.The dispersibility and stability of the slurries both increased with the increase of solid phase content and TMAH content.The aqueous SiC based slurry was pseudo-plastic non-Newtonian fluid with shear-thinning property.The nanoparticles in the slurry were 'parceled' or 'fixed' by YAG sol with network structure to form approximate aggregate with the size of 50—100 nm,which resulted in the stability and dispersion of nanoparticles.
