Study On Processing Method Of Single Crystal Sapphire Based On Polysaccharide Binder Abrasive

Single crystal sapphire,namely single crystal alpha-alumina,has a hardness of up to 9 and is a typical hard brittle and difficult to process material.With the rapid increase of market demand for single crystal sapphire substrates,the environmental impact of surface processing of single crystal sapphire can not be ignored.In order to meet the requirement of green,efficient and precise surface processing of single crystal sapphire,this paper proposes a surface machining method of single crystal sapphire based on soft abrasive tools with polysaccharide binder.Firstly,based on the basic theory of heat transfer,a theoretical model of equivalent specific heat capacity of two-phase composites considering phase change process of phase change materials is established.The error between theoretical value and simulation value of equivalent specific heat capacity of composites with different volume fractions of phase change materials is less than 5%.The theoretical model of equivalent thermal conductivity of two-phase composites is suiTab for Maxwell-Euken I model.When the total heat of the interface between abrasive tool and workpiece is constant,the heat distribution of sapphire workpiece decreases gradually with the increase of volume fraction of phase change material.The formulation design of abrasive tool was completed and the selection of abrasive material was determined.A pregelatinized polysaccharide binder abrasive tool was developed based on the "mixture-gelation-efrigeration-freeze-drying" route.DSC results show that after adding wax powder,the heat absorption peak appears in the temperature range of wax powder transformation,and the specific heat capacity increases,which verifies the correctness of the theoretical analysis.The results of single crystal sapphire surface machining show that the decrease of Rq value of rough workpiece surface contour is positively correlated with the temperature rise per unit load,and the hardness and bending strength of abrasive tools are also positively correlated with the holding force of abrasive particles.Under the same sand junction ratio between abrasive tool and sapphire workpiece,the temperature rise of abrasive tool with phase change material is lower than that of abrasive tool without phase change material in the second half of the processing.It is determined that when sapphire is processed,the best processing effect is achieved when the abrasive bond ratio of the grinding tool is 5:1 and the content of wax powder is 10% of the mass fraction of starch binder.