Fabrication And Performance Analysis Of Alumina Ceramic Accessories

Testing high temperature mechanical properties of structural materials is one of thedifficult problems of the study of inorganic non-metallic materials. In2011, the Ministry ofScience and Technology approved a Special-funded Program on National Key ScientificInstruments and Equipment Development, in order to develop special instruments which canbe sued to measure high temperature mechanical properties of materials. The aim of this workis to provide high temperature ceramic accessories for an ultra-high temperature oxidationtesting system. Therefore, we need to design and fabricate the ceramic accessories. Thethermal shock resistance, the performance of the accessories after cyclic uses and soaking athigh temperatures for long time were tested and analyzed. The results will provide thereference for a good selection of accessories for the ultra-high-temperature oxidation testingsystem as well as the determination of the application conditions, the number of recycling ofthe selected accessories. So that the aim of maintaining stable operation, improving theperformance and extending the life of the instrument can be achieved.In this study, we fabricated alumina ceramic accessories and analyzed their performance.Steps involved in the fabrication of the alumina ceramic accessories include the design ofaccessories and testing samples, the design and preparation of molds, the processing of Al₂O₃ceramic raw materials, the forming and sintering of ceramic green bodies. Dry and isostaticpressing methods were used respectively for forming ceramic green bodies. The Al₂O₃ceramic bodies were sintered under1650and1630oC. Containing98%Al₂O₃ceramic,95porcelain and nano-powder containg Al₂O₃ceramic specimens were prepared. The crystalstructure, fracture morphology, mechanical properties and thermal shock resistance of thesamples were analyzed.The dry pressing samples with containing98%Al₂O₃ceramic and nano-powdercontaing Al₂O₃ceramic have room temperature flexural strength more than310MPa. Thehigh temperature flexural strength of containing98%Al₂O₃ceramic at1000and1350oC is157MPa and117MPa, respetcively. The room temperature flexural strength of the95porcelain specimens is239MPa. The specimens made by isostatic molding have roomtemperature flexural strength of232MPa. The softening temperature under loading of0.2 MPa of this specimen is higher than1700oC and the creep at1550oC is only one-tenthousandth.Within a certain temperature range, the flexural strength of Al₂O₃ceramic specimens wasmeasured after soaking at high-temperatures. The room temperature flexural strength increaseas the sample was soaked at higher temperatures for prolonging time. The alumina ceramicsamples could sustain one or more times of thermal shocks from200oC to room temperaturewith no significant loss of strength. However, when the initial temperature for the thermalshock test was higher than250oC, the residual flexural strength of Al₂O₃ceramic specimen issubstantially reduced. The residual flexural strength does not decrease with increasing thenumber of thermal shocks. Therefore, the prepared Al₂O₃ceramic accessories could be rapidly cooled when the furnace temperature is lower than200oC.