Surface modification of alumina nanoparticles and its application in tape casting of micro-nano green tape

Nanoparticles are widely used for the fabrication of advanced ceramics. Unfortunately, nanoparticles tend to agglomerate when added to ceramic slurries for tape casting. In this study, the surface modification process of alumina nanoparticles was studied. Coupling agents were introduced to modify the surface of alumina nano-particles to prevent their agglomeration in ceramic slurry during tape casting. The effects of variation in the modifier dosage, modification temperature, and modification time on the activation index and oil absorption value of modified alumina nanoparticles were investigated. The influence of the modification process on microstructure and properties of the micro-nano green tapes was also investigated. Experimental results showed that the best modification effect was achieved via modification of the alumina nanoparticles with 2.5 wt% of titanate coupling agent at 60 degrees C for 20 min. The activation index increased from 2% for the raw alumina nanoparticles to 94.9% for the modified alumina nanoparticles, while the oil absorption value decreased from 75.2 mL/100 g to 55.8 mL/100 g. The sedimentation rate of the slurry decreased from 26% to 4% after modi-fication of the nanoparticles, and the volume of nanoparticles increased appreciably from 35 vol% to 45 vol%. The surfaces of the green tapes prepared using slurries with modified alumina nanoparticles were smooth without visible defects.