大气等离子喷涂FeCoCrNiAl高熵合金涂层的高温摩擦磨损性能

目的 研究环境温度对FeCoCrNiAl高熵合金涂层摩擦磨损性能的影响,探讨将其应用于高温及富氧环境中的可行性。方法 采用大气等离子喷涂制备FeCoCrNiAl高熵合金涂层,考察喷涂功率对涂层微观组织的影响;测试涂层的纳米力学性能,分析其对涂层摩擦磨损性能的影响;基于涂层及对偶磨球磨损表面形貌、元素分布及含量、物相组成,讨论涂层在室温及高温环境中的摩擦磨损特性与机制。结果 涂层中形成了白色、浅灰色、深灰色及黑色4种区域,区域颜色随O元素含量增加而加深,涂层纳米力学性能逐渐增加,进而将对其摩擦磨损性能造成影响。20 kW喷涂功率制备涂层的室温摩擦因数、磨损率及磨痕深度均达最佳值,分别为(0.70±0.02)、(9.22±0.01)×10^-5 mm³/(N·m)及(130±10)μm。室温环境下,磨粒磨损、疲劳磨损及塑性变形为涂层的主要磨损机制。20 kW功率制备涂层的摩擦因数、磨损率、磨痕深度等均随摩擦环境温度的升高先增加而后降低,经600℃摩擦试验后分别低至(0.58±0.01)、(6.14±0.01)×10^-5 mm<...     

冷喷涂制备防腐涂层研究现状

针对海洋环境中各类钢铁构件日益严重的腐蚀现状,鉴于传统热喷涂技术无法解决涂层孔隙率高、热应力大等缺陷,冷喷涂技术制备防腐涂层受到国内外越来越多学者的关注。在分析大量文献的基础上,对冷喷涂制备防腐涂层的研究现状进行了分类和总结。首先,对比传统热喷涂技术特点,指出冷喷涂技术制备金属涂层、复合涂层以及非金属防腐涂层的优势和可行性,同时从电化学腐蚀角度揭示金属涂层和复合涂层的防腐机理,并简述了前人对非金属涂层防腐机理的各种合理分析。其次,从涂层孔隙率、电化学性质(包括自腐蚀电位、腐蚀电流等)以及特定应用环境下的腐蚀试验等防腐性能表征入手,归纳了冷喷涂制备的金属涂层、非金属涂层以及复合涂层等研究成果,并发现冷喷涂制备防腐涂层技术正在逐渐走向成熟,相对于金属和复合涂层,非金属涂层正在从实验室研发阶段向工业应用过渡。最后,分析了冷喷涂制备防腐涂层当前存在的主要问题和应用前景。     

Modelling and analysis of ozone episodes

Air pollution is one of the primary environmental concerns in France due to the public health question. People wish to be informed of the air pollution level in real time or to be warned in advance of a peak of pollution.The goal of this study is to show the feasibility of developing an operational system to forecast the air pollution level. In our case, this level depends on the ozone concentration in the atmosphere.This prediction has been made by using a fuzzy logic based method. One advantage of this kind of model is to be able to extract information on the phenomena.Results obtained with this method are encouraging and some supplementary work needs to be done.     

Superplasticity in fine-grained 20% Al2O3/YTZ composite

The microstructure and superplastic deformation of fine-grained, 20% Al₂O₃-reinforced, yttria-stabilized, tetragonal zirconia (Al₂O₃/YTZ) has been investigated. Hot identation and tensile tests were carried out at temperatures between 1000° and 1650°C. The material exhibited extensive plasticity at temperatures higher than 1200°C, and a maximum tensile elongation of over 625% was recorded. The microstructure of the Al₂O₃/YTZ was thermally unstable, and concurrent grain growth, and in particular dynamic grain growth, was observed at temperatures higher than 1450°C. Although the apparent strain rate sensitivity exponent was determined to be approximately 0.5, the true strain rate sensitivity, after compensation for grain growth, is about 0.67. The activation energy for superplasticity in Al₂O₃/YTZ was determined to be 257 kJ/mol which is much lower than the activation energy for superplastic Y-TZP. Of particular interest were the grain-boundary structures and the chemical compositions of the grain boundaries. Microstructures were studies using transmission electron microscopy, Auger electron spectroscopy, and X-ray photoelectron spectroscopy. No glassy phase was detected at grain boundaries.