【作者】 张思宇；

【导师】 蒋明学；

【作者基本信息】 西安建筑科技大学 ， 材料学， 2004， 硕士

【摘要】 镁铝尖晶石是一种性能良好，用途广泛的陶瓷材料。对其烧结性能的研究具有理论和实践意义。 本实验以纳米MgAl₂O₄、纳米Al₂O₃粉和Q—Al₂O₃微粉为原料，在440MPa下半干压成型，压成Φ38×5mm的薄样。在碳管炉中1900℃、1620℃的烧结温度下，真空下无压烧结，以及在氧化气氛下1500℃无压烧结，制备了不同温度和不同气氛下的MgAl₂O₄陶瓷和氧化铝陶瓷，应用SEM、显微硬度仪等分析手段研究了各试样的力学性能、烧结性、物相组成、微观结构和它们的耐腐蚀性。 随着烧结温度的升高，各试样的密度逐渐增大，气孔逐渐减少。粉末较细，烧结驱动力高，在1500℃下就已初步烧结。由MgAl₂O₄试样的密度可得出，烧结过程符合Invensen（ν_s/ν_p=常数）致密化方程。 MgAl₂O₄烧结试样的维氏硬度数据表明，MgAl₂O₄硬度值服从正Hall—Petch关系(H=H₀+Kd^-1/2，其中K>0)。多晶尖晶石和氧化铝表现出很强的抗化学腐蚀能力。各样品在腐蚀24小时前后重量变化很小。MgAl₂O₄样品比Al₂O₃样品的抗强酸、强碱的腐蚀能力强。更多还原

【Abstract】 Passageways of metropolis in entrance and exit (PMEE) act as a channel connecting metropolis s material system with outer regions , which sustain the political, economical and cultural role of metropolis, with the development of city economy and the integration of whole region ,city highway transportation increases rapidly which lead to a new situation that city passageways in entrance and exit (PCEE) face large pressure from outer highway and inner urban street traffic. Many domestic cities have seen the worse traffic situation occurred in areas through city entrance and exit such as time delay of come and go lengthened, traffic congestion and roaring traffic accidents. In a word, transport of entrance and exit have became a bottleneck to development of urban transportation systemThe dissertation analyzes the reason that PCEE traffic situation take a turn for the worse, based on which the content and scope of PCEE transportation programming are outlined. It may be a new idea and spotlight that the above PCEE transportation problem will be analyzed and dissolved from the point of view that PCEE and related external traffic generating or attracting sources are looked as a whole.,Firstly, the dissertation discuss that the development city of has a deep bearing on PCEE, founded on the relationship of PCEE S formation and the shape of city. The suitable layout under some certain conditions of highway and city is recommended in accordance with the impact of highway on bourgeon of city; quoting the theory of spider network construction, the dissertation demonstrated the optimized number of city entrance and exit fit for the formation and scale of city; the obtained conclusions are confirmed by three related samples of eastern city.Secondly, the core of dissertation is put up. the connotation, limit and characteristics of PCEE is discussed. Based on that, it is argued that two kinds of maneuver and model of PCEE traffic volume forecasting, the calculating of PCEE capacity and the referenced criterion and dimension used for carving out PCEE service level are advanced.Accordant to factors affecting the layout of PCEE ,the maneuver for planning linear location of PCEE is formed. Taking into account that unfit transverse sector design can stand for the reason of traffic condition worsted, included parts of PCEE transverse sector are analyzed and suitable layout styles are recommended.Study in a deep going way ,the dissertation put forward traffic flow organizing pattern of PCEE, including mobile station layout considering the coordination with PCEE traffic, and principles and means of PCEE intersection traffic flows steering.Finally, the dissertation applies the above maneuvers into the concrete example of Xi an metropolis. Xi an traffic situations and PMEE transportation system are explored, and aiming at the problems of Xi an PMEE traffic the dissertation raises the mentalities and measures for settlements.更多还原