Study On Gelcasting Process Of SiC Whisker Toughened Alumina Ceramics

Al₂O₃ ceramics have excellent properties such as high melting point,high hardness,acid and alkali corrosion resistance,and excellent electrical insulation.They were widely used in the fields of energy,aerospace,machinery,automobiles and chemicals.Due to the characteristics of alumina ceramic materials,it was difficult to perform secondary processing after sintering.Therefore,this experiment used a gel injection molding process,which could meet the molding requirements of the green body without secondary processing.In order to achieve the purpose of strengthening and toughening ceramics,SiC_w（silicon carbide whiskers）was used as the second additive phase,and SiC_w/Al₂O₃ composite ceramics were prepared under argon protective gas pressureless sintering conditions.The main research contents and conclusions of this paper were as follows:（1）The relationship between the surface modification of alumina powder and the content of SiC_w and the rheological properties of the slurry was stu..died,and the viscosity value of the alumina slurry was analyzed.Studies had shown that when the SiC_w content was as high as 10%,the viscosity of the Al₂O₃-based ceramic composite slurry was 67 Pa·s,and the composite slurry had good rheological properties.（2）The relationship between p H and the stability of the dispersant and alumina slurry was studied,and the Zeta potential of the alumina slurry was measured.Studies had shown that when the p H of the slurry was 9 and the dispersant content was 1wt%,the absolute value of the Zeta potential reached the maximum,and the slurry was in the most stable state at this time.（3）The relationship between the content of SiC_w and the properties of alumina ceramics was studied,and the porosity,flexural strength,fracture toughness and other properties of alumina ceramics were analyzed.Studies had shown that when the SiC_w content was 10%,the flexural strength and fracture toughness of SiC_w/Al₂O₃ ceramics reached the maximum at the same time,which were 48MPa and 3.01MPa·m^1/2,respectively.（4）This paper studies the strengthening and toughening mechanism of SiC_w,and analyzed it in detail by means of microscopic morphology and other detection methods.Studies had shown that the toughening phase SiC_w consumed crack growth energy through whisker pullout,crack deflection,and crack bridging,which acted as a toughening alumina ceramic and improved the mechanical properties of ceramic materials.（5）The relationship between the sintering system and the properties of alumina ceramic was studied,and the porosity,flexural strength,fracture toughness and other properties of alumina ceramics were analyzed.Studies had shown that when the sintering temperature was1550℃and the holding time was 3h,the flexural strength and fracture toughness of SiC_w/Al₂O₃ceramics reached the maximum at the same time,which were 82MPa and 5.11MPa·m^1/2,respectively.