共查询到20条相似文献,搜索用时 15 毫秒
1.
Yan Feng Meng Dong Detian Li Xiaobin Wu Yongjun Cheng Lan Zhao Yongjun Wang 《Mapan》2014,29(4):229-234
A new measurement apparatus for vacuum materials outgassing rate was developed, which is mainly composed of three systems, including ultra-high vacuum system, high vacuum system, switching between two pumping paths (SPP) measurement system. The test principle of the modified SPP method is described in details, and the newly-developed technique has two main advantages over the conventional one. Firstly, the errors due to the use of two gauges with different physical properties are avoided by using only one gauge during data processing. Secondly, the outgassing rate of sample chamber, the test chamber and the outgassing or pumping effect of the gauge head can be eliminated enormously. Based on the SPP method, this paper gives the details of the experiments and the results on specific outgassing rate of the 7075 aluminum alloy sample in different conditions, namely, at different times and at different temperatures generated by infrared light irradiation heating. 相似文献
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V. N. Narozhnyi G. Fuchs A. Handstein A. Gümbel J. Eckert K. Nenkov D. Hinz O. Gutfleisch A. Wälte L. N. Bogacheva I. E. Kostyleva K.-H. Müller L. Schultz 《Journal of Superconductivity and Novel Magnetism》2002,15(6):599-601
We report on the results of a comparative investigation of highly dense bulk MgB2 samples prepared by three methods: (i) hot deformation; (ii) high pressure sintering; and (iii) mechanical alloying of Mg and B powders with subsequent hot compaction. All types of samples were studied by AC susceptibility, DC magnetization, and resistivity measurements in magnetic fields up to μ0 H = 160 kOe. A small but distinct anisotropy of the upper critical field $\psi {\rm H}_{c2}^{\alpha ,b} /H_{c2}^c \sim 1.2$ connected with some texture of MgB2 grains was found for the hot deformed samples. The samples prepared by high pressure sintering as well as by mechanical alloying show improved superconducting properties, including high upper critical fields H c2 (μ0 H c2 (0) ~ 23 T), irreversibility fields H irr which are strongly shifted towards higher values H irr(T) ~ 0.8 H c2(T) and high critical current J c (J c = 105 A/cm2 at 20 K and 1 T). 相似文献
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Solid materials contain impurities from manufacturing/cleaning processes which diffuse (out‐gas) to the exterior during exposure to vacuum, especially at elevated temperature levels. Materials like plastics and resins tend to disintegrate under space conditions. In addition to the above mentioned diffusion process, contaminants adsorbed and absorbed from the environment encountered previously, e.g. during manufacturing, cleaning, integration, test and launch phases, might be desorbed from the surfaces. The released products represent a permanent source of potential contamination. This paper provides an overview of a research program carried out at the Austrian Research Centers Seibersdorf (ARCS), Aerospace Materials Technology Testhouse (AMTT), by means of the AMTT Sublimation Test Facility to acquire in‐depth knowledge of the outgassing kinetics characteristics of a set of non‐metallic materials, selected by Alenia on the basis of their usage on the International Space Station (ISS) and Scientific Satellites. 相似文献
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V. N. Narozhnyi G. Fuchs A. Handstein A. Gümbel J. Eckert K. Nenkov D. Hinz O. Gutfleisch A. Wälte L. N. Bogacheva I. E. Kostyleva K.-H. Müller L. Schultz 《Journal of Superconductivity》2002,15(6):599-601
We report on the results of a comparative investigation of highly dense bulk MgB2 samples prepared by three methods: (i) hot deformation; (ii) high pressure sintering; and (iii) mechanical alloying of Mg and B powders with subsequent hot compaction. All types of samples were studied by AC susceptibility, DC magnetization, and resistivity measurements in magnetic fields up to 0
H = 160 kOe. A small but distinct anisotropy of the upper critical field
connected with some texture of MgB2 grains was found for the hot deformed samples. The samples prepared by high pressure sintering as well as by mechanical alloying show improved superconducting properties, including high upper critical fields H
c2 (0
H
c2 (0) 23 T), irreversibility fields H
irr which are strongly shifted towards higher values H
irr(T) 0.8 H
c2(T) and high critical current J
c (J
c = 105 A/cm2 at 20 K and 1 T). 相似文献
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不同保鲜方式对葡萄保鲜效果影响的对比研究 总被引:1,自引:0,他引:1
目的研究气调包装和微孔膜包装对葡萄贮藏期间品质的影响,为延长葡萄货架期提供依据。方法以新鲜葡萄为实验材料,分别采用O2(5%)+CO2(5%)+N2(90%)(气调1)和O2(10%)+CO2(10%)+N2(80%)(气调2)等2种气体比例(均用体积分数表示)的气调包装,以及PE参尼龙多层共挤材质的微孔保鲜膜(微孔膜)对新鲜葡萄进行包装,在温度为4℃的条件下进行贮藏,每隔48h对葡萄的硬度、pH值、可溶性固形物、可滴定酸、抗坏血酸、色度和质量损失率等变化进行测定,并进行感官评价。结果在贮藏0~12 d,从整体保鲜效果来看,微孔膜气调2气调2裸放组。结论葡萄在采后贮运期间,当葡萄的货架期≤12d时,使用3种包装均有利于延缓其衰老进程,PE参尼龙共挤微孔膜保鲜膜的保鲜效果最好。 相似文献
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为探究环氧玻璃钢材料在不同温度下的放气特性,以扩散放气模型为基础,建立了环氧玻璃钢材料放气速率随抽空时间变化关系的数学表达式,并结合实验数据拟合获得了其经验模型。同时,采用静态升压法对不同温度下环氧玻璃钢材料放气速率随抽空时间的变化关系进行了研究。结果表明,温度一定时,环氧玻璃钢材料的放气速率随着抽真空时间逐渐减小;温度升高,环氧玻璃钢材料放气速率增大,且放气速率随着抽真空时间呈现出指数衰减规律。此外,采用四极杆质谱仪分析了不同温度下环氧玻璃钢材料的放气成分,放气成分以H2O为主,并含有微量的H2、CO、N2及O2等。温度升高,玻璃钢材料放气各组分的占比无明显变化,表明温度对玻璃钢材料放气组分的占比几乎没有影响。 相似文献
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A. Abdullah A. S. Saleemi M. Anis-ur-Rehman 《Journal of Superconductivity and Novel Magnetism》2014,27(1):273-276
Cerium oxide (CeO2) nanoparticles were synthesized by using sol–gel methods and the Composite Mediated Hydrothermal Method (CMHM). Sol–gel synthesis was done for 0.6 M molarity of the precursor solution of cerium nitrate hexa hydrated [Ce(NO3)3?6H2O] and the hydrothermal synthesis was done at 180 °C for 45 min. X-Ray diffraction (XRD) was used to measure the structural properties of the prepared ceria. Scherrer’s formula was used to calculate the crystallite sizes of average and most intense peak. Temperature dependent (200 °C to 700 °C) dc conductivity was measured and found to be increasing with the increase in measuring temperature. The frequency dependent (20 Hz to 3 MHz) ac conductivity and dielectric properties were measured at different temperatures. The comparison of electric and dielectric properties was studied. Both synthesis techniques were further analyzed by the Raman spectrum at 514 nm excitation laser line for the different bands of cerium oxide and oxygen vacancies. 相似文献
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不同方法测试粒度分布的比较研究 总被引:6,自引:6,他引:6
介绍了不同原理仪器粒度测试结果间存在差异的原因以及对测试结果准确性应如何评价。用筛分法和激光法对氧化铝样品进行测试对比,初步分析结果间的差异。结果表明,筛分法和激光法测试粒度分布在质量(体积)累积分布达到50%时,测试结果相差最小,不同的粒度组成、颗粒的形状都会造成两种方法测试结果的差异。 相似文献
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在文物保护研究领域,保护材料的“可逆性”是经常争议的问题之一:什么样的材料是可逆性材料?能否定量地表达可逆性?可逆性材料渗入砖、石、陶等多孔性材质中还可取出来吗?可逆性材料老化以后的可逆率会如何变化等等。为了探索这一类基础理论问题,本实验室提出运用“可逆率”来定量地表征材料应用过程的可逆性,可逆率可以通过清除实验来测量。通过测定B72、氟橡胶、纯丙乳液、环氧树脂在釉面瓷片、光面大理石、山西砂岩、凝灰岩和四川沙岩表面的取出率,计算出了它们的可逆率。实验表明许多保护材料都有一定的可逆性,其可逆率的大小与被保护基底材料的孔隙率(吸水率)呈反比,也与清除剂的种类和清除工艺有关,同时保护材料的紫外光老化过程也会明显影响保护材料的可逆率。文物保护材料可逆率的测量将会是研究其功能和机理的重要方法。 相似文献
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在重庆主城区进行的材料腐蚀暴露试验表明:(1)碳钢、铜、铜合金和大理石等材料,其完全暴露的腐蚀速度约为遮蔽暴露腐蚀速度的2倍;(2)铜、铜合金的腐蚀速度与SO2浓度非常相关,与NO2浓度显著相关,碳钢的腐蚀速度与SO2、NO2和TSP浓度没有明显的相关性;(3)碳钢的腐蚀速度约为青铜的20倍,纯铜的25倍,古铜的28倍,大理石的19倍. 相似文献
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SiO2不同的掺杂方式对聚氨酯树脂材料性能的影响 总被引:8,自引:0,他引:8
采用溶胶凝胶法制备纳米SiO2颗粒,然后在聚氨酯弹性体/SiO2复合材料的不同制备方法方面进行了尝试,并针对SiO2不同的掺杂方式对聚氨酯树脂材料性能的影响进行了研究,为聚氨酯弹性体性能的优化提供了一条最佳的思路和方法.利用红外分光光度计(IR)、万能电子试验机、动态力学分析仪(DMA)、量热示差扫描仪(DSC)、紫外/可见/近红外分光光度计(UV/VIS/VIR)分别表征了纳米复合树脂材料的结构、力学性能、热稳定性、展色性和干爽性. 相似文献
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N. I. Sorokin P. P. Fedorov O. K. Nikol''skaya O. A. Nikeeva E. G. Rakov E. I. Ardashnikova 《Inorganic Materials》2001,37(11):1178-1182
Data are presented on the electrical conductivity of fluorine ion conducting PbSnF4solid electrolytes prepared by different methods—aqueous (precipitation from solution and hydrothermal synthesis) and nonaqueous (melt solidification). 相似文献
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Jan‐Marten Seitz Kelly Collier Eric Wulf Dirk Bormann Nina Angrisani Andrea Meyer‐Lindenberg Friedrich‐Wilhelm Bach 《Advanced Engineering Materials》2011,13(12):1146-1151
The research on the development and characterization of potential magnesium biomaterials is a steadily expanding. Commonly, implants present a high risk of infection for their recipients. For this reason, a pre‐operative sterilizing process is required. Due to the temperatures and media which are used while sterilizing, effects may occur which cause a change in the mechanical strength of certain magnesium alloys. Four commonly used sterilization methods (autoclave sterilization, dry heat sterilization, gamma sterilization and ethylene oxide sterilization) were investigated to gain information about their influences on the quasi‐static mechanical behavior of LAE442 (Mg 90 m.%, Li 4 m.%, Al 4 m.%, RE 2 m.%), MgCa0.8 (Mg 99.2 m.%, Ca 0.8 m.%) magnesium alloys as well as pure magnesium. The mechanical properties exhibited by the sterilized and non‐sterilized alloys refer to susceptibilities of the mechanical strengths to the investigated sterilization methods. Such susceptibilities appear to be dependent on the combination of alloy and method of sterilization. However, the maximum changes in mechanical strength appear in the range of ±10%. Within this study, ETO sterilization caused the least changes in the mechanical strength of the alloys and appears to be the best performer. 相似文献
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多类型食品包装材料的迁移研究 总被引:21,自引:9,他引:12
食品应具备的首要品质就是食用安全性,可目前与食品接触的包装材料中添加剂的迁移成为了一个关于健康问题的隐患.国外学者研究了各种类型的食品接触包装材料中化学物向食品(模拟物)的迁移,对研究进展进行了概述,简介了迁移的有关基础知识:迁移极限的规定、食品模拟物的选择、(加速)迁移试验要求、迁移机理、迁移预测模型.介绍了国外研究者在各迁移研究领域所进行的研究现状及结论,包括常规使用条件下塑料、再生塑料、纸和纸板、金属罐,非常规使用条件如微波加热、γ辐射、高压处理下包装材料中化学物成分的迁移. 相似文献