共查询到20条相似文献,搜索用时 109 毫秒
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钼合金作为一种高温结构材料、功能材料,被广泛应用于冶金工业、航空航天、核工业等诸多领域.近年来,随着相关行业的技术升级,钼合金凭借特有的优势,其应用范围也不断扩大.同时,对钼合金的使用性能也提出了更高的要求.尤其是有色金属、医疗器械材料等加工行业已明确提出对钼合金材料中氧含量的技术要求.详细介绍了目前国内外TZM钼合金低氧制备技术的研究现状,分析了TZM钼合金中氧的来源,明确了钼合金制备过程中起氧化作用的主要因素,讨论了烧结过程中氧含量的变化以及料层厚度对氧含量的影响规律,总结出目前国内外TZM钼合金低氧制备的关键技术.在此基础上,对现在国内外TZM钼合金低氧制备技术的研究未涉及且还需完善之处提出补充意见,并展望了低氧TZM钼合金制备技术的发展前景. 相似文献
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研究了不同状态钼的断裂韧性及其韧化机制.借助于拉伸、弯曲方法测定了Mo-La2O3材料的断裂韧性K1C和塑--脆转变温度(DBTT),并用SEM、TEM、AES等方法对镧钼材料的变形、断裂特征和组织结构进行分析.研究结果表明:烧结态Mo-La2O3的K1C值达到24.76MPa.m1/2,是纯钼的2.5倍多,而且高于热锻空冷态TZM钼合金.经1900℃退火的镧钼板,其塑--脆转变温度降低至-60℃,较同样状态的纯钼降低80℃.La2O3对钼具有显著的韧化效果.AES结果表明,添加La2O3并不改变C、N、O等致脆杂质在钼晶界上的分布状态.Mo-La2O3的韧化主要归因于其抗裂纹扩展能力的提高,而这与La2O3改变钼中的位错分布及组态有密切的关系.提出了一种新的韧化机制--硬脆第二相的韧化机制,能很好解释实验结果. 相似文献
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钼丝和钼箔广泛用于白炽灯作冷却芯杆、灯丝支架和箔封.掺杂钼具有很高的高温强度和再结晶温度,高温应用中已大量取代未掺杂的钼材.掺杂铝-钾-硅(AKS)的钼由于细小钾泡对晶界的钉扎作用,再结晶温度可达1 800℃(未掺杂的钼仅为1 200℃),而氧化镧掺杂的钼,再结晶温度更高.为了弄清掺杂剂的作用,美国通用电气环球研究所的L.E.Iovio等人对AKS掺杂钼丝和氧化镧掺杂钼丝中的掺杂颗粒的特性进行了研究,制作了直径为0.18 mm和0.41 mm的AKS掺杂钼丝,并分别用2 000℃,10 min和2 350℃,30 min的工艺制度进行再结晶热处理.还制作了直径为0.51 mm,0.62 mm和0.64 mm的氧化镧掺杂钼丝,分别用1 800℃,30 min和2 350℃,30 min的工艺制度进行再结晶热处理.用透射电镜(TEM)对两类掺杂钼丝的加工态和退火态进行了分析. 相似文献
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以粉末冶金方法生产的25 mm×280 mm×320 mm纯钼及钼镧合金板坯为实验原料,研究了不同的热轧终轧加工率对钼及钼镧合金板显微组织及力学性能的影响.结果表明,将纯钼及钼镧合金板热轧终轧加工率控制在50%以上,轧后纯钼板材的显微组织为细化的纤维流线组织,纵、横向的Rm分别为795,885 MPa,A5分别达到27%,21%,其后续的温轧加工不开裂;而钼镧合金板材不论是显微组织,还是力学性能均好于纯钼.进一步的生产实践证明,将钼及钼镧合金板的热轧终轧加工率控制在50%以上,其强度、塑性和硬度匹配良好,弯曲性能和后序的温轧加工性能明显提高. 相似文献
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对纯钼及不同掺杂量的Si、Al、K掺杂钼的组织和性能进行了研究.利用金相显微镜观察了热分析以后的组织形貌,用透射电镜观察了烧结坯的精细结构.将掺杂钼在不同温度退火后测试其硬度,并对比分析了纯钼和掺杂钼的高温拉伸性能.发现经过加热到1600℃热分析以后,掺杂钼的晶粒比纯钼细小,而且掺杂量愈大,晶粒的长径比愈大;烧结态纯钼中没有第二相粒子存在,而掺杂钼的晶粒和晶界上分布着掺杂颗粒.掺杂样加热到一定的温度时硬度值都显著下降,随着掺杂含量的增加,硬度最小值出现的温度随之升高;掺杂钼条的高温抗拉强度和屈服强度都明显高于纯钼,并且随着实验温度的提高,强度的提高幅度增大. 相似文献
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介绍了一种用Y2O5对TiO2进行施主掺杂来改善TiO2光作用范围的方法,并研究了用该方法制备的光催化剂对甲胺磷的降解情况.钇离子以草酸盐化合物形式按比例掺杂到草酸氧钛酸中,经过结晶析出针状钇掺杂草酸氧钛酸晶体,再经过热分解和焙烧获得钇掺杂TiO2光催化剂粉体.钇掺杂TiO2光催化剂粉体中金红石矿型TiO2和锐钛矿型TiO2都分别控制在45%和55%左右,粒度分布在0.2~0.5μm范围,颗粒接近球形,钇掺杂量为0.2%时光催化效果较佳,日光灯降解6h后,甲胺磷的无机磷回收率达到96.4%. 相似文献
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A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling. 相似文献
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O'Brien RS 《Radiation protection dosimetry》2003,105(1-4):95-100
Australia has several uranium mines and a large number of mineral sand mines, with associated processing facilities. Exposures resulting from these mining and processing operations usually involve intakes of mixtures of radionuclides. This work describes the development of a suite of first order, linear compartment models, based on the ICRP Publication 66 respiratory tract model, and an analytical solution to the decay equations, for assessing the consequences of such intakes. The computer programs based on these models directly compute excretion, organ retention and organ and whole-body doses for intakes of either single radionuclides or any mixture of radionuclides belonging to the same radioactive decay chain. The intake can be via inhalation, ingestion or injection, and can be acute, chronic or of limited duration. The starting concentration and degree of secular (dis)equilibrium can be specified for each radionuclide. No assumptions need to be made about the relative magnitudes of the radioactive half-lives of the different nuclides. 相似文献
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本文根据多年的实践检定经验 ,参照JJF1 0 59- 1 999《测量不确定度评定与表示》以及《测量不确定度表达 1 0讲》 ,对卧式金属罐容量的测量结果不确定度进行了评定。 相似文献
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Liebert A Wabnitz H Grosenick D Möller M Macdonald R Rinneberg H 《Applied optics》2003,42(28):5785-5792
A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue. 相似文献
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V. Ya. Fateev 《Measurement Techniques》2011,54(7):774-780
Different constructions of the sensing elements of radio-frequency level sensors based on sections of long lines are numerically
investigated by means of the Matlab program for the purpose of minimizing the measurement error caused by the nonlinearity
of the output characteristic. It is shown that the nonlinearity is lowest for U-shaped designs. The nonlinearity factor KN
may be regulated by varying the capacitance of a correcting capacitor connected to the input of the sensing element and (or)
the length of one of the sections of the long line. In selecting an optimal capacitance of the correcting capacitor KN ≤ 0.15%
for control media with dielectric permittivity in the range 2.2–30. 相似文献