The Research On Design And Preparation And Performance Of High-Reliability Alumina Ceramic Composites

Ceramic materials have become an important part of modern new materials because of their excellent properties such as high strength,high hardness,high temperature resistance and corrosion resistance,among which alumina ceramics have high application potential and value in medicine,chemical industry,machinery,aerospace and other fields because of their excellent oxidation resistance,chemical stability and low cost.However,the ionic covalent bond of ceramic materials hinders all ductile behavior,resulting in its inherent brittleness and defect sensitivity,which seriously affects the service reliability of ceramic parts and restricts its application in more fields.Based on the design concept of high-performance bionic structural ceramics,and on the basis of exploring the influence of interface on the mechanical properties and damage resistance of alumina ceramic composites,this paper further adjusts the phase composition of the interface,the damage resistance and reliability of alumina ceramic composites are greatly improved,and the structural parameters are optimized.The synergistic improvement of mechanical properties,damage tolerance and self-healing ability of alumina ceramic composites was realized,and the toughening mechanism and self-healing mechanism in different service environments were revealed.The main conclusions are as follows:1.Using short Al₂O₃ fibers as the main body,high damage tolerance alumina ceramic composites with different proportion of interfacial phase were constructed by using composite weak interfacial phase,and the effect of interfacial phase content on its mechanical properties and damage resistance was investigated.The material shows typical non-brittle fracture and rising Rcurve behavior,in which the crack growth resistance and the maximum critical crack size of the sample with 15%interfacial phase can reach 10 MPa·m^1/2 and 105.47± 19.11 μm,which are 2.35 and 14.57 times of pure alumina ceramics.The damage tolerance parameter of the material is 0.71 ±0.06 m^1/2,which is 5.85 times of pure alumina ceramics.At the same time,the crack propagation behavior in the fracture process of the material is clarified,the relationship between crack propagation length and propagation resistance is established,and the mechanism of material toughening and damage tolerance is further revealed.2.Based on the structural design of high damage tolerance,changing the composition of composite interface phase,exploring the effect of adding selfhealing components on the fracture behavior of materials,preparing carboncontaining coating on the surface of fiber matrix by PVA pyrolysis and optimizing the sintering process,retaining external toughening mechanisms such as crack deflection,bifurcation,fiber pull-out and bridging,so as to maintain excellent ductile fracture behavior of ceramic composites,and finally determined that the self-healing phase is SiC and the sintering temperature is 1400℃.At this time,the fracture stress of the sample is about 30 MPa,showing typical non-brittle fracture behavior.3.The effect of interfacial phase content on the fracture impedance behavior and damage tolerance of highly reliable alumina ceramic composites was studied,and its effect on self-healing was explored by controlling the heat treatment conditions.When the interfacial phase content is 15%,it shows the best comprehensive properties,showing typical non-brittle fracture and rising R-curve behavior,the crack growth resistance can reach 11.5 MPa·m^1/2,the critical crack maximum size and damage tolerance parameters are 76.7±23.2 μm and 0.28±0.03 m^1/2.The sample was loaded until the crack occurred and the load decreased to 80%of the maximum value.After heat treatment at 800℃ for 60 min in the atmospheric atmosphere,showed the highest fracture strength recovery rate,which could be restored to 70.1%of the original sample.The self-healing effects of different heat treatment conditions were summarized,and the self-healing mechanism of highly reliable alumina ceramic composites was further revealed.