Reserch On Preparation And Properties Of Core-shell Composite Abrasives

In the grinding and polishing process,diamond,alumina and other high hardness abrasives directly impact the machined surface,and cause“hard”impact on the machined surface,resulting in large scratches,cracks,pits and other micro-defects.Due to its unique core/shell structure,especially the abrasives with higher hardness coated with a softer material?such as CeO₂,SiO₂,polymer,etc.?,core/shell structured composite abrasives can make the polishing process of scratches,cracks,pits and other defects reduced,which has incomparable advantages over single abrasives.In this paper,nanodiamond/carbon and nano-alumina/carbon composite abrasives with core/shell structure were prepared by using nanodiamond and nano-alumina as cores respectively.Then,their dispersion stability,particle size distribution,settling behavior and polishing properties were tested.Nanodiamond/carbon composite abrasives with core/shell structure were synthesized by surface precipitation method,hydrothermal method and subsequent high temperature carbonization.When the amount of nanodiamond added was increased from20 mg to 60 mg,the size of composite abrasives was reduced from 234.4 nm to 160.8 nm,the shell thickness was reduced from 59.5 nm to 30.9 nm,and the weight gain was reduced from 185 wt%to 108 wt%.Zeta potential test results showed that the dispersion stability of the composite abrasives was significantly improved compared with the original nanodiamond in the pH value of 8 to 12.At the pH value of 10,the maximum Zeta potential reached-61.3 mV.The polishing test showed that the composite abrasives play a certain role in reducing the scratches and pits on the polished surface of single crystal silicon carbide.Core/shell nano-alumina/carbon composite abrasives were prepared by electrostatic self-assembly,hydrothermal method and subsequent carbonization at high temperature.When the amount of nano-alumina was increased from 20 mg to 40 mg,the particle size of the composite abrasives was reduced from 729.2 nm to 540.2 nm,the thickness of the shell layer was reduced from 211.3 nm to 114.7 nm,and the weight gain was reduced from 308 wt%to 102 wt%.Zeta potential test results showed that the dispersion stability of the composite abrasives was greatly improved in the pH range of 8 to 12.The Zeta potential reached-45.6 mV at the maximum at the pH of 10.Laser particle size analysis showed that the particle size distribution of core/shell structured nano-alumina/carbon composite abrasives was narrower than that of the original nano-alumina.The polishing test showed that the composite abrasives reduce the scratches on the polished surface of single crystal silicon.