Preparation And Performance Study Of Alumina Based Through-pore And Permeable Ceramics

As one of the clamping methods for silicon and glass wafers used in the electronic industry,ceramic chucks have obvious advantages over other metal chucks,the plastic chucks.This clamping method is particularly suitable for large and thin workpieces such as silicon wafers.Ceramic chuck is used to "adsorb" workpiece to clamp silicon wafer by vacuum negative pressure,so permeability is very important to ceramic chuck.Therefore,conducting research on through-pore permeable ceramics is of great significance and will greatly expand its application in the semiconductor industry.On the basis of previous studies,the preparation of porous ceramics using corundum and α-Al2O3 powder as raw materials,and on the basis of traditional dry pressing method,compared and studied the new gel casting molding method to prepare porous ceramics,and carried out the research on the microstructure,material properties and pore-forming mechanism of porous porous ceramics.The main work and results are as follow s:(1)Using the dry pressing method,using the "particle packing to form pores" design principle,the effect of sintering additive content and sintering temperature on the microstructure and properties of through-pore and permeable ceramics were studied.The results show that the ceramic microstructure tends to be densified gradually,the porosity decreases continuously,the strength increases continuously,and the permeability increases first and then decreases,no matter increasing the content of MnO2-TiO2 or increasing the sintering temperature.When the assistant MnO2-TiO2 is 8 wt.%,the basic MgCO3 is 1 wt.%,and the kaolin is 6 wt.%,the sintering temperature is 1400℃,and the permeability of porous ceramics is 16.15 L·min-1·cm-2 at 100 kPa pressure.(2)Using the dry pressing method,using the "particle packing to form pores" design principle,the effect of aggregate content and aggregate particle size on the microscopic morphology and properties of through-pore ceramics and its pore-forming mechanism were studied.The research shows that whether the aggregate content or aggregate particle size increases,the internal pores of the material increase,the porosity and permeability increase,and the strength decreases.At the same time,it is found that the surface roughness increases with the increase of aggregate particle size.When the aggregate particle size is 600 mesh and 1000 mesh,the surface roughness is less than 5 μm and the aggregate content is 90 wt.%,the best permeability is obtained.But generally speaking,although the strength of the material obtained by only using the method of particle packing to form pores is high,the controllable range of air permeability is small.The pore formation mechanism of particle stacking method can be summarized as follows:during the process of particle stacking,some pores are first formed between the aggregates,and then during the subsequent sintering process,the matrix shrinks to form some pores.(3)Studies have proved that the porosity and permeability of materials can be improved by adding pore-forming agent on the basis of particle packing.The effect of pore-forming agent type and content on its micromorphology and properties and its pore-forming mechanism were discussed.With the increase of PS microsphere content,the internal holes continue to increase,porosity and permeability increase,and strength decreases.The results showed that when the aggregate particle size was 600 mesh and the content of polystyrene microspheres(PS microspheres)with an average particle size of 31 μm was 10 wt.%,the porosity of the prepared through pore ceramics reached 36.64%,the average bending strength was 63.93 MPa,and the permeability at 100 kPa was 47.85 L·min-1·cm-2.The average aperture is 35.73 μm,and the surface roughness is less than 5 μm.Generally speaking,adding pore forming agent on the basis of particle packing can increase the controllable range of permeability,but its strength is low and pore size distribution is not uniform.The pore-forming mechanism can be summarized as the formation of partial pores between aggregates in the process of particle accumulation.Secondly,the pore-forming agent decomposed at high temperature,leaving some pores;Finally,during the sintering process,the matrix shrinks to form some pores.(4)Using the gel casting method,using the "particle packing to form pores" design principle.The pore structure and properties of porous ceramics were controlled by adjusting solid content,aggregate particle size and aggregate content.With the increase of solid content,its porosity and permeability decrease and its strength increases.With the decrease of aggregate particle size,its porosity,air permeability and surface roughness decrease,and its strength increases.With the increase of aggregate content,the porosity and permeability increase,and the density and bending strength decrease.The results show that when the aggregate particle size is 600 mesh and the aggregate content is 80 wt.%,the through pore ceramics have uniform morphology,the porosity is 40.05%,the average bending strength is 66.71 MPa,the permeability is 61.00 L·min-1·cm-2 at 100 kPa,and the surface roughness is less than 5 μm.The average aperture is about 19 μm.At the same time,it is confirmed that the material obtained by gel casting method has a wide range of controllable permeability,strength meets the application requirements,uniform pore size distribution,good surface smoothness,excellent comprehensive performance,and basically meets the application conditions of ceramic chuck.The mechanism of pore formation is basically the same as that of particle packing in dry pressing method.However,due to the introduction of gel casting technology,the arrangement between aggregates is looser,which makes the porosity of porous ceramics higher.