| Considering the contradiction between corrosion resistance and thermal shock resistance of Zirconia ceramics in expanding their application, and the insurfficiency of traditonal theory on evaluating the thermal shock resistance of ceramics, three different Zirconia ceramics--3Y-TZP, 4Y-TZP and Mg-PSZ were used to be the matrix to prepare ZrO2/LaPO4 composites, the possibility of improving the thermal shock resistance of Zirconia ceramics by the elastic energy dissipation resulted from the LaPO4 debonding and crack branching or bridging at the weak interface was investigated. Based on the study on the mechanical properties, microstructures and the growth behavior of microcracks, the thermal shock resistance of ZrO2/LaPO4 composites was investigated systematically. The main conclusions are as follows:The thermal shock resistance of 4Y-TZP was improved with increasing the content of LaPO4. Under the condition of air quenching,ΔTc of 4Y-TZP/LaPO4 was 400oC higher than that of pure 4Y-TZP.In the particle size range from 0.5μm to 1.5μm, the monolithic 4Y-TZP ceramics with fine particle size had a higher thermal shock resistance. But for 4Y-TZP/LaPO4 composites, when the content of LaPO4 was up to 20 vol%, the thermal shcok resistance of the composites with coarser particle size was better.When LaPO4 content was kept 15vol%, the composites containing 13μm or 35μm LaPO4 and sintered at 1470 oC /2h has better thermal shock resistace; Under condition of 1470 oC /3h, LaPO4 particle size was 2.5μm, theΔTc of the composites was 1300 oC under condition of air quenching,.The density and thermal shock resistance of Mg-PSZ/LaPO4 ceramics increased with increasing the LaPO4 content. Under water quench condition, the thermal shock resistance of Mg-PSZ/10wt% LaPO4 composites was 100 oC higher than pure Mg-PSZ. The composites containing 15 wt % LaPO4 behaves as a low strength refractory ceramic and has a good thermal shock damage resistance.Under the same thermal shock condition, the fraction of crack propagation and crack extension was the lowest for 3Y-TZP/LaPO4 containing 15vol%,40μm LaPO4, and the highest for that containing 30vol%,13μm LaPO4.The thermal shock resistance of ZrO2/LaPO4 composites can not be predicted accurately by the value of traditional thermal shock parameters. The partial relief of the elastic strain energy resulted from crack initiation, crack branching at weak interfaces and cleavage fracture of LaPO4 grains was the main reason for the improvement of their thermal shock resistance.
|
PDF Full Text Request