Study On Direct-write 3D Printing Technology Of SiC Ceramics

Silicon carbide possesses excellent properties and is widely applied in the fields of petrochemical,aerospace,microelectronics,steel,automotive,etc.At present,there are a number of forming methods to obtain SiC including dry pressing molding,slip casting technology,gel casting process and tape casting method,etc.However,these methods are limited by the size and shape of the products,and cannot be free from the restriction of the mold.In order to solve the problems above-mentioned,a new method of direct ink writing was used to prepare SiC ceramics,which possesses the advantages of high molding accuracy,no need for molds,and little restriction of size and shape.Rheometer,direct-write 3D printer,SEM,XRD,universal testing machine and hardness tester were used to explore the preparation of direct-write 3D printing SiC slurry,direct-write 3D process parameters and sintering and properties direct-write 3D printing SiC body.The main results were as follows:The SiC slurry of direct ink writing has been studied.The results showed that 1.0 wt%PEI(M.W.70000)content was found to be optimum amount to prepare a well dispersed suspension with high stability.With the increase of SiC solid content,the viscosity,yield stress and storage modulus were observed to be increased.All the slurries exhibited shear-thinning behaviors with increasing the shear rate.When the solid contents were 45,50 and 55 vol%,whose yield stresses and storage moduli were equal or greater than 70 Pa and 0.45×106 pa,respectively,the slurry can be extruded smoothly from the nozzle and has good shape retention ability.The process parameters of direct-write 3D printing were studied.The experimental results indicated that the optimum block was achieved when the extrusion pressure,printing speed,layer thickness and filling ratio were 0.4 MPa,15 mm/s9 60-70%of the nozzle diameter and 80%,respectively.The printing error of length,width and height for SiC green body were-0.4 mm,-0.4 mm,and-0.2 mm,respectively.When SiC with 55 vol%,the green body of bulk and porous grid were prepared under the optimum printing process parameters,which forming precision were 600±20 μm and 650±20 μm,respectively.The effect of sintering process on mechanical properties of SiC for direct-write 3D printing was studied.The experimental results indicated that the mechanical properties of SiC ceramics increased initially and then decreased with the increase of sintering temperature.An increase in mechanical properties was observed for SiC ceramics with increasing solid loading of SiC.When the green body with solid content of 55 vol%was sintered at 2000℃,the properties of SiC ceramic were the best,and its relative density,Vickers hardness,flexural strength and fracture toughness were 96.56%,33.58 GPa,182 MPa and 4.12 MPa·m1/2,respectively.When SiC with 55 vol%was sintered at 2000℃,the porous grid SiC ceramics of 10 PPI were prepared,and the compressive strength of which reached 42.5 MPa.