Preparation Of Porous Ceramics Using Silicon Kerf Waste As Raw Material

The increase in global warming and exhaustion of energy resources valued the development of renewable energy,especially silicon-based solar photovoltaic power sources.During manufacturing of silicon wafers,crystalline silicon is obtained by multi-wire saw.However,unfortunately,over 40% of valuable silicon is discarded as slurry loss in the process of wire sawing.The cutting waste consists mainly of high-purity silicon,silicon carbide abrasives,shredded metal fragments,and polyethylene glycol(PEG)solutions.If this waste is recycled and reutilized,it will not only reduce solid waste pollution problem but also greatly lower the cost of silicon wafers.In this paper,porous silica/mullite ceramics were successfully prepared by foam-gelcasting method using silicon kerf waste as raw material.The present work provides new sights into the advanced utilization of silicon kerf waste for preparation of porous ceramics,which should not only save cost for separation of SiC and Si,but also reduce solid waste pollution problems.In this experiment,the phase composition and relative content of the cutting waste were determined by XRD,XRF and chemical analysis.Secondly,the effects of dispersant dosage,pH and solid content on the viscosity of the slurry were studied,and the amount of catalyst and initiator was explored.The effect of gel curing behavior was investigated.Finally,the effects of different sintering temperature,solid content and blowing agent dosage on the morphology,properties,phase and pore size of the prepared porous ceramics were studied.The phase composition and microstructure of the samples were characterized by XRD and SEM,and the porosity,bulk density,compressive strength and thermal conductivity of the samples were analyzed and determined.The specific research results and innovations of this paper are as follows:The phase composition of the waste is mainly silicon and silicon carbide,and its content: Si is 50.25%,and SiC is 35.37%.The effect of solid content on viscosity is significant.When the concentration of dispersant is 0.5Wt%,pH is 8,the viscosity of ceramic slurry is the lowest.Therefore,by reasonable regulation of these three parameters,ceramics that meet the requirements of gel injection molding can be prepared.When the amount of catalyst and initiator is 0.4 ml/100 g and 0.8Wt%,the slurry can be rapidly solidified within 5~10min,and the green body is easy to demould and has high strength;Using the difference in surface tension between water and ethanol,the liquid phase drying technique can effectively avoid the warpage deformation and cracking of the green body.When the solid content is 50Wt%,the sintering temperature is 1300°C,and the blowing agent dosage is 0.5Wt%,the prepared porous ceramic has a porosity of 86.7%,a compressive strength of 3.19 Mpa,and a thermal conductivity as low as 0.178W/(m)?K);indicating that the material can be used in the field of thermal insulation.Microstructures of the as-prepared porous ceramics were found complex,depicting large-sized spherical pores,circular window pores,and small-sized pores present on internal walls.