气压一步烧结和两步烧结对氮化硅陶瓷结构和性能的影响

Effect of Single-step and Two-step Gas-pressure Sintering on Structure and Properties of Silicon Nitride Ceramics

以Yb_(2)O_(3)和Al_(2)O_(3)为烧结助剂,研究气压一步烧结和两步烧结工艺对Si_(3)N_(4)陶瓷结构件微观形貌、力学性能的影响。结果表明:一步烧结长时间保温可以减少样品内部孔隙,但是会导致β-Si_(3)N_(4)晶粒异常长大,恶化部分力学性能。采用两步烧结制备的Si_(3)N_(4)陶瓷相对密度达98.25%,内外结构均一,没有晶粒异常长大现象;其维氏硬度(HV)为1478、室温抗弯强度为832 MPa、高温(900℃)抗弯强度为646 MPa、断裂韧性为7.3 MPa·m^(1/2),具有优良的综合力学性能。两步烧结是一种有效制备高致密、良好综合力学性能Si_(3)N_(4)陶瓷结构件的方法。

Yb_(2)O_(3) and Al_(2)O_(3) are used as sintering aids to study the effects of single-step and two-step sintering process on microstructure and mechanical properties of SiN4 ceramics.Single-step sintering for a long time can be used to reduce internal pores of the sample,but abnormal growth ofβ-SigN4 grains is present,thus deteriorating mechanical properties to a certain degree.Relative density of the SigN4 ceramics prepared by using two-step sintering could reach 98.25%,while the internal and external structures are uniform and no abnormal grain growth is observed.The sample has hardness of 1478 Hv,room temperature flexural strength of 832 MPa,high temperature(900°C)flexural strength of 646 MPa and fracture toughness of 7.3 MPam,while italso has excellent comprehensive mechanical properties.Therefore,he two-step sintering is an ffctive method to prepare Si,N4 ceramics with high density and high comprehensive mechanical properties.