Research On The Preparation And Properties Of Al₂O₃ Poly-hollow Microsphere Ceramics Via Selective Laser Sintering

At present,Al₂O₃ porous ceramics prepared by traditional methods have poor controllability of pores,poor mechanical properties and limitation in directly preparing porous ceramics with complex structures,which restrict the application of Al₂O₃ porous ceramics.In this paper,Al₂O₃ poly-hollow microsphere ceramics?Al₂O₃ PHM ceramics?were directly prepared by selective laser sintering?SLS?using Al₂O₃ poly-hollow microspheres?Al₂O₃ PHMs?as main raw materials,which combined the unique advantages of SLS with the controllability of pores of PHMs.This new method is expected to prepare Al₂O₃ porous ceramics with complex structure,controllable and high porosity.In order to improve the mechanical properties of Al₂O₃ PHM ceramics,sintering aids were introduced.The effects of material composition,SLS parameters and sintering temperature on the phase composition,microstructure,shrinkage,porosity,pore size distribution and mechanical properties of Al₂O₃ PHM ceramics were investigated.The main results are summarized as follows:?1?The SLS parameters were optimized by orthogonal experiment:P=6 W,?=1800mm/s,H=0.15 mm.When the sintering temperature increases,Al₂O₃ PHM ceramics only contain Al₂O₃ phase and are gradually densified.With the increase of sintering temperature,the shrinkage and compressive strength of Al₂O₃ PHM ceramics increase,but the porosity decreases gradually.The sintering temperature has little effect on the pore size distribution of Al₂O₃ PHM ceramics.At 1650°C,the diameter and height shrinkage,porosity,compressive strength and pore size distribution of Al₂O₃ PHM ceramics were 14.03%and 13.10%,72.41%,0.72 MPa and 21.4?m respectively.?2?In order to improve the mechanical properties of Al₂O₃ PHM ceramics,CaSiO₃ sintering aid was coated on the surface of Al₂O₃ PHMs by chemical coprecipitation.When the content of the sintering agent increases,CaAl₂Si₂O₈ phase appears in Al₂O₃PHM ceramics,and distinct sintered necks appear between Al₂O₃ PHMs.With the increase of the coating content of the sintering agent,the shrinkage of Al₂O₃ PHM ceramics increases,the porosity decreases and the compressive strength increases greatly.The content of the sintering aid has little effect on the average pore size distribution of ceramics,but the peak of the pore size distribution slightly decreases with the increase of the sintering aid.When CaCl₂ solution was added in an amount of 40 mL/100 g Al₂O₃,the diameter and height shrinkage,porosity,compressive strength and pore size distribution of Al₂O₃ PHM ceramics were 21.83%and 19.74%,68.16%,8.39 MPa and45.45?m respectively.?3?In order to adopt a simpler method to improve the properties of Al₂O₃ PHM ceramics,SiO₂ PHMs were added in Al₂O₃ PHMs by mechanical mixing.When the addition amount of SiO₂ PHMs increases,cristobalite phase appears and gradually increases,but the peak intensity of corundum phase and mullite phase gradually decreases,and there is obvious fusion bonding between the PHMs.With the increase of the content of SiO₂ PHMs,the shrinkage and compressive strength of Al₂O₃ PHM ceramics first increase and then decrease,but the porosity decreases first and then increases,which all reach the threshold value when the content of SiO₂ PHMs is 30 wt%.The average pore diameter of Al₂O₃ PHM ceramics gradually decreases as the content of SiO₂ PHMs increases.When the addition amount of SiO₂ PHMs was 30 wt%,the diameter and height shrinkage,porosity,compressive strength and pore size distribution of Al₂O₃ PHM ceramics were 14.17% and 13.87%,64.97%,3.95 MPa and 38.25?m respectively.In this paper,Al₂O₃ PHM ceramics with improved properties were prepared by SLS technology.It is a simple but effective method to directly prepare Al₂O₃ PHM ceramics with complex structure and high porosity,which has certain theoretical and practical value.