The Study About The Processes Of Ceramic Gelcasting Based On 3D Printing

Ceramic materials have a series of advantages,such as high hardness,high temperature resistance,oxidation resistance and so on.They have broad application prospects in aviation,electronics,medicine and other fields.But they are characterized by high hardness and brittleness,which bring great difficulties to their forming and processing,and the traditional forming method is difficult to manufacture complex shape ceramic parts.3D printing technology can directly form three-dimensional solid parts of complex shape by additive processing,which makes up for the shortcomings of traditional processing methods.However,when 3D printing is used to form ceramics,there are problems such as poor performance and low molding accuracy,making it difficult to manufacture high-performance and high-precision ceramic parts.The ceramic gelcasting process based on 3D printing achieves the net forming of ceramic parts with complex shape and high performance,the traditional gelcasting was combined with the 3D printing technology.First,the Stereo Lithography Apparatus was used to form a polymer part mold with complex shape and high accuracy,and then the ceramic part was shaped by gelcasting.In the process of subsequent pyrolysis,the polymer master mold was burnt out,and the ceramic dense body was obtained by high temperature sintering.SiC and ZrO₂ ceramic powders were selected as the research objects,the rheological test,thermogravimetric analysis,Fourier transform infrared spectroscopy,bending strength,fracture toughness and scanning electron microscope and X ray diffraction were used to study the densification mechanism,the mechanical properties and microscopic morphology of ceramic specimens.After the ceramic performance was optimized,dimensional change of parts at each process stage was controlled in reverse.（1）Preparation of SiC ceramicsSiC slurry with high solid phase concentration was prepared by adding tetramethylammonium hydroxide as a dispersant.The water soluble polymer polyvinyl alcohol was infiltrated to improve surface exfoliation of the ceramic body.Based on the TG thermogravimetric curve of the SiC body and the master mold material,the appropriate process for the integrated of debinding and mold burning was determined.Boron carbide and organic carbon source sucrose were used as sintering aids.According to the maximum density and the highest toughness of the sintered body,the content of boron carbide and sucrose was determined.The relative density and fracture toughness of the final sintered body reached 98.13%and 4.54Mpa·m^1/2,respectively,and SiC complex part（with inner holes）and impeller were formed.（2）Preparation of ZrO₂ ceramicsThe gel reaction time was controlled by the use of ammonium persulfate as an initiator and tetramethylethylenediamine as a catalyst.Using the density and bending strength as the part performance index,the type of powder,solid content of slurry,and sintering temperature were optimized by orthogonal test.The final ZrO2 all ceramic tooth had a density of 98.6%,a flexural strength of 1170 MPa,a fracture toughness of 22.9 Mpa·m¹/2/2 and a Vickers hardness of 1383 HV,the grain was fine and closely arranged.（3）Control of size shrinkage in the process of integrated drying of wet blank and master mold and sinteringIn order to obtain the ceramic body with complete shape,the effect of different drying methods on the defect of the body was explored.In order to obtain high accuracy ceramic parts,the size of each process was controlled in reverse.Taking ZrO₂ as an example,the relative error of dimensional accuracy was controlled within2%under the optimum process parameters.In this paper,two kinds of SiC and ZrO₂ ceramic parts have been formed by the gelcasting method based on 3D printing,which greatly improves the processability of non-oxide and oxide ceramics,also provides references for forming complex shapes ceramic parts for other ceramic materials,broadening the application of 3D printing technology in ceramic materials.