Influence of a heterolayered Al2O3–ZrO2/Al2O3 ceramic protective overcoat on the high temperature performance of PdCr thin film strain gauges

The application of PdCr thin film strain gauges on gas turbine engines requires protective overcoats to prevent the oxidation of the PdCr sensitive element. In this work, a heterolayered Al₂O₃–ZrO₂/Al₂O₃ ceramic film, which was fabricated by electron beam evaporation, is utilized as a protective overcoat over the PdCr sensitive thin film. The morphology and microstructure of the prepared films indicate that the composite Al₂O₃–ZrO₂ film is smooth and compact, and the interface between the composite Al₂O₃–ZrO₂ film and Al₂O₃ film is crack-free, which contributes to improving the protective performance of the heterolayered Al₂O₃–ZrO₂/Al₂O₃ ceramic protective overcoat at high temperature. Moreover, the PdCr thin film strain gauge with heterolayered Al₂O₃–ZrO₂/Al₂O₃ ceramic film as protective overcoat displays a minimum drift rate of less than 0.09%/h at 800 °C, and excellent cyclic repeatability such that the eight cyclic curves of the relative grid resistance are almost overlapped from room temperature to 800 °C, indicating the excellent protecting performance of the heterolayered Al₂O₃–ZrO₂/Al₂O₃ ceramic overcoat. It also reveals the smallest temperature coefficient of resistance of 155.3 ppm/°C compared to the monolayer Al₂O₃ overcoat and composite Al₂O₃–ZrO₂ overcoat.     

中国微米纳米-PdCr薄膜电阻应变计研制及其高温应变敏感性能研究

在航空航天以及核电领域中,准确测量高温部件的应变、疲劳等结构参数十分重要,对满足高温应用环境的高温应变计需求非常迫切.在镍基合金基底上研制了PdCr薄膜电阻应变计,依次在基片上沉积NiCrAlY作为过渡层来增强附着性,沉积YSZ/Al2O3作为复合绝缘层满足绝缘性需求,溅射PdCr合金作为应变敏感层,并采用金属掩模对PdCr敏感层进行图形化,最后沉积Al2O3薄膜层作为高温保护层,并对PdCr薄膜应变计的应变敏感系数(GF)以及高温环境下的表观应变、漂移应变等性能进行了表征.结果表明,不同温度下PdCr薄膜应变计的电阻值随应变呈良好的线性关系;在常温下,其应变敏感系数为1.40;在800 ℃时,应变计的表观应变系数127 με/℃.应变计的电阻值随时间线性减小,导致的漂移应变约为1 800 με/hr,应变敏感系数为1.41.同时,对制备的PdCr薄膜应变计进行了可靠性评估和寿命评估.结果表明,其重复性测量误差约为5.71%,工作寿命超过10 h.     

微型薄膜集成氢气敏感器件的研制

采用将类光激发二极管(即N-Si/Thin-SiO2/Thin-Ta/PdCr/Pt结构)、PdCr合金薄膜电阻、Pt加热和感温双电阻温控系统等集成的方式,研制了微型薄膜集成氢气敏感器件,能稳定测量0~2%体积分数的氢气,且具有较快的响应和恢复时间。