热处理温度对非晶晶化法制备ZrO2-Mullite纳米复相陶瓷结构与力学性能的影响

采用非晶原位晶化法从Si-Al-Zr-O(SAZ)系非晶中制备ZrO2-mullite纳米复相陶瓷.用XRD、IR和SEM技术对前驱体非晶以及晶化后试样进行表征,并着重研究热处理温度对ZrO2-mullite纳米复相陶瓷结构与力学性能的影响.结果表明,前驱体SAZ非晶经960℃热处理开始析出t-ZrO2晶体,1000℃时莫来石晶相形成.试样经低温950～1000℃和高温1100～1250℃梯度热处理后,t-ZrO2、mullite成为主晶相,同时生成c-SiO2.其中低温阶段的核化温度对陶瓷试样的显微结构和断裂韧性产生重大影响.当核化温度由950升至1000℃时,纳米颗粒明显增大,断裂韧性急剧下降;而高温阶段的晶化温度对力学性能影响相对较小.随着晶化温度的升高,试样的断裂韧性和抗弯强度均先略有增加随后下降.试样经950℃核化、1150℃晶化后取得最佳力学性能:断裂韧性5.13 MPa·m1/2和抗弯强度521 MPa.

Effects of Heat-Treatment Temperature on Structure and Mechanical Properties of ZrO2-Mullite Nano-Composite Ceramics Fabricated by in-situ Crystallization

ZrO2-mullite nano-composite ceramics were prepared by in-situ crystallization of Si-Al-Zr-O (SAZ) amorphous bulk. The amorphous bulk and as-prepared ceramics were characterized by XRD, IR and SEM. The influence of heat-treatment temperature on the structure and mechanical properties of ZrO2-mullite nano-composite ceramics was investigated. The results show that the t-ZrO2 began to form after 960 oC heat treatment of SAZ bulk and mullite was crystallized at 1000 oC in the amorphous bulks. The main phases were identified as t-ZrO2 and mullite, and at the same time cristobalite formed by a two-step gradient heat treatment at 950-1000 oC and 1100-1250 oC. The first-step nucleation temperature has a great effect on the microstructure and fracture toughness, and with the increase of the temperature from 950 oC to 1000 oC, the nano-particle size increases but the fracture toughness decreases sharply. However, the influence of the second-step crystallization temperature on the mechanical properties is not obvious. The fracture toughness and flexural strength increase gradually, and then decreases as the crystallization temperature increasing. The nano-composite ceramics exhibit the best mechanical properties, including the flexural strength up to 521 MPa and the fracture toughness up to 5.13 MPa·m1/2 after 950 oC nucleation and then 1150 oC crystallization