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71.
已建成的兰州重离子加速器的真空室是一个大型整体结构的超高真空容器,直径约10m,高4.5m,重65000kg,内表面积211m~2,容积100m~3,工作真空度为5×10~(-5)Pa。采用有限单元法在计算机上用SAP-5C程序对真空室受力分析进行了计算。真空室结构材料选用瑞典Uddeholm钢厂生产的316 L 超低碳不锈钢。承制此大型容器的是航天工业部风华机器厂。由于结构庞大,首先将真空室分成八大块和几小块在工厂制造,然后运至现场焊制成一整体容器并进行机械加工。所有密封焊缝均用着色渗透液,X-射线探伤和氦质谱探漏仪进行检查和探漏。 相似文献
72.
X. S. Ning K. Suganuma T. Okamoto A. Koreeda Y. Miyamoto 《Journal of Materials Science》1989,24(8):2879-2883
Two kinds of additive-free silicon nitride ceramics were brazed with aluminium; one was with as-ground faying surfaces and
the other was with faying surfaces heat-treated at 1073K for 1.8 ksec in air. The heat-treatment of the silicon nitride ceramics
formed a silicon oxynitride layer on the faying surfaces and increased the brazing strength of the joints. A silica-alumina
non-crystalline layer and a β′-sialon layer were formed successively from the aluminium side at the interface of the joints.
The heat-treatment which made the former layer thicker is a necessary process in making reliable, strong brazed joints. 相似文献
73.
Most algorithms on receiver autonomous integrity monitoring (RAIM) are under the assumption of a single-satellite fault, because there is an extremely small probability that significant simultaneous multiple-satellite faults may occur. However, after the implementation of the Galileo system in a few years, there will be more satellites in view for the user to utilise together with GPS satellites, and a combination of them will bring better performance for RAIM. On the other hand, with the help of wide area augmentation system and the use of dual-frequency operation, pseudo-range errors will be reduced greatly. Thus, tighter alert limits are required for RAIM, and formerly `small' errors should not be neglected. All of those factors make it necessary to consider simultaneous multiple-satellite faults. A detailed theoretical analysis of RAIM under the condition of two-satellite faults for both vertical and horizontal directions is presented. The characteristic/max slopes for every pair of satellites are then deduced in order to calculate the tighter vertical/horizontal protection level for RAIM 相似文献
74.
On structural and high temperature electrochemical properties of ZrO2 thin film coating on Zr metal produced by carbonate melt 总被引:1,自引:0,他引:1
Melt of NaCO3 can favor oxidation of Zr to form ZrO2 thin film on Zr surface, which is used to make Zr/ZrO2 oxidation/reduction electrode of pH sensor for testing elevated temperature aqueous solutions. Using SEM, EPMA, XPS, EXAFS
and HRTEM, we found that ZrO2 film is tightness and solid with 20 μm thickness composed by nanometer-sized monoclinic crystals. Zr/ZrO2 interface is characterized of zoning structure according to topography and chemical composition in five zones: oxygen-rich
ZrO2, ZrO2, oxygen-rich Zr metal, oxygen-bearing Zr and Zr from outmost to center. Melt oxidation process of Zr involved oxidation time,
air and temperature. The air is important effect on structural and electrochemical properties of ZrO2 thin film for making elevate temperature electrochemical sensor. If oxygen air largely presented in carbonate melting process,
ZrO2 thin film is not tightness and not for oxidation/reduction electrode. 相似文献
75.
Daniel X. Gouveia Odair P. Ferreira Antonio G. Souza Filho M. G. da Silva J. A. C. de Paiva Oswaldo L. Alves Josué Mendes Filho 《Journal of Materials Science》2007,42(2):534-538
The thermal decomposition properties of Mg–Fe hydrotalcites were studied through in situ 57Fe Mössbauer spectroscopy and in situ X-ray diffraction. Abrupt changes in the quadrupolar splitting measured in the Mössbauer spectra revealed a phase transition from the starting lamellar structure to a new crystalline arrangement. By analyzing the Mössbauer parameters we show that the material is highly disordered in the 300–400 °C temperature range. This hypothesis is confirmed by the X-ray results whose diffractograms indicated the collapse of the lamellar structure and the formation of a solid solution. 相似文献
76.
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79.
The material properties of maraging steels are greatly affected by the alloy and inclusion content and hence by the production route. This paper describes various past and current production routes at Böhler Edelstahl GmbH and the effect of these routes on the specified element (alloy) and non-specified element (inclusion) contents. Non-metallic inclusions were investigated by EDX analysis. The effects of various alloying and tramp elements on the material properties are presented as a statistical evaluation of previous melts. Nitrogen solubility was calculated with Thermo–Calc for maraging steel Mat.-No. 1.6354 and the precipitation of nitrides is discussed. A proposal is made for the production of melts with improved properties. 相似文献
80.
Polyurethane elastomer composites were developed using milled fiberglass and their mechanical properties were studied. In particular, the organically chemical treatment of the milled fiberglass was investigated in detail. It was demonstrated that both strength and toughness of the resulting elastomer composites were improved considerably with the addition content of fiberglass. Furthermore, it was indicated that the optimal properties can be achieved by the proper addition of milled fiberglass that was chemically treated using coupling agent. 相似文献