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Refractory nanometals have been the subject of interest for the past two decades in order to manufacture compact materials with dramatically improved mechanical properties for aerospace, military, chemical and metallurgical applications. The interest in nanomaterials has led to the development of many synthetic methods for their fabrication. In this review the challenges, synthesis methods and the characteristics of refractory metal nanopowders of IV–VI sub-group of the periodic table are discussed. Special attention is paid to salt-assisted combustion reaction (SACR) as a promising technique for the large-scale production of refractory metal nanopowders.The current paper will: (1) focus on the synthesis methods, morphology and physical–chemical characteristics of metal nanopowders; (2) present the specific feature of the salt-assisted combustion reaction, combustion parameters and macro-kinetic aspects of chemical reactions in the powder bed; and (3) demonstrate the perceptiveness of the fabrication route for the mass production of nanosized powders.  相似文献   

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  On April 21–25, 2008, the Bauman Moscow State Technical University hosted the 10th All-Russia Conference on “Problems and State of Measurements,” which was dedicated to the 140th anniversary of the Faculty of Machine Industry Technologies. It was attended by representatives of colleges: Lomonosov Moscow State University, Zhukovskii VVIA, MAI and Stankin Moscow State Technical Universities, Goryachkin MGAU, Ural (Ekaterinburg), Orel, Perm, Tula, and Penza State Universities, the Russian Academy for the State Service under the Russian Federation President, the Maimond Classical Academy, the Novomoskowsk Institute of the Mendeleev Russian Chemical Engineering University, Kharkov Electronics National University; and also research institutes in the RAS system: the Keldysh Institute of Applied Mechanics, the Lebedev Physics Institute of the Academy of Sciences, the Trapeznikov Institute of Control Problems, the Institute of Psychology, IMASh and the Blagonravov Nizhnii Novgorod branch of IMASh, and IPMASh (St. Petersburg); the Malaya Therapy Institute (Ukraine) and sectoral institutes: the Astrofizika Scientific and Production Association, Snegirev NITI, VNIIMS, NIIizmereniya, Moscow Institute of Expert Evaluation and Testing, LITMAShDETAL’, and the Omskenergoremont OAO PRP. In this number of the journal and the next one, we present a selection of articles from the conference. We also publish a survey article by the chairman of the organizing committee of the conference, Professor M. I. Kiselev. Translated from Izmeritel’naya Tekhnika, No. 10, pp. 3–5, October, 2008.  相似文献   

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量子点敏化太阳能电池发展至今,其效率已经突破了5%,但是与染料敏化电池12%的效率相比还是存在着较大的距离,从电荷复合、量子点的光捕获、光阳极的结构、电解质和对电极5个方面分析了量子点敏化电池效率低下的原因,以及针对以上5个方面目前量子点敏化电池的研究所采取的改进措施。  相似文献   

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Guidelines for calculations of the heat exchange are worked out on the basis of analytical-computational and experimental investigations of the temperature pattern in porous metal shells and gas flows in their vicinity.  相似文献   

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《Nanostructured Materials》1998,10(8):1379-1392
A microwave plasma processing technique was used to synthesize iron nanopowders. The average particle size of these powders was ~10 nm and the surface area was measured to be 42m2/g. Powder production rates as high as 50 gm/hour were achieved. Magnetic property measurements on iron nanopowders yielded coercivities as high as 60 kA/m at 4 K, which decreased to ~0 A/m (a superparamagnetic transition) at room temperature. In this paper, the microwave plasma processing technique has been compared with other nanopowder synthesis techniques. Since the successful application of nanomaterials depends highly on the processing technology, results from consolidation studies on iron nanopowders are also presented. Iron nanopowders were consolidated to study performance parameters such as density, grain growth and other morphological changes. The nanopowder was consolidated using Plasma Pressure Consolidation (P2C) technique to 95% density, at a temperature and pressure of 850 °C and 63 MPa respectively. Microwave plasma synthesis is capable of producing metallic and ceramic nanopowders, which will sustain interest in research areas including magnetic storage, nano-fabrication of electronic materials and nanoglass, besides the field of catalysis.  相似文献   

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Spherical, rod and fibroid hydroxyapatite [HAp, Ca10(PO4)6(OH)2] nanoparticles were prepared and dispersed in aqueous media. Temperature and solution pH were the key factors to synthesis of different morphology and crystallinity. Processing conditions were selected from ternary diagram of pH, temperature and Ca:P ratio. High hydroxyl ion concentration (12.25  pH  10.5) and low temperature (298 K) favored isotropic non-confined spherical particles, intermediate concentration (9.5  pH  7.75) and low temperature (303 K) initiated the anisotropic growth of rod shaped particles but low concentration (7  pH  5.25) and high temperature (353 K) accelerated one-dimensional fibroid morphology. The dispersed HAp–citrate complex exhibited a constant zeta potential and size distribution for six months.  相似文献   

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孙维民  张毅  石明浩  刘正  董星龙 《功能材料》2008,39(6):1017-1020
在50%CH4 20%H2 30%Ar,总压为2×104Pa的混合气氛下,用直流电弧等离子体蒸发纯Fe制备了Fe-C纳米粉体.用XRD、TEM、HRTEM、XPS、VSM、化学分析和氧含量分析等测试手段对粉体进行了分析.结果表明,在50%CH4 20%H2 30%Ar的混合气氛下制备的粉体形貌接近类球形,平均粒度50nm,粒子具有核壳结构,核为Fe-C,壳为4nm左右的碳膜.在温度低于300℃时,在50%CH4 20%H2 30%Ar气氛下制备的纳米粉体抗氧化性比在50%H2 50%Ar气氛下制备的强,饱和磁化强度为151.8Am2/kg,比在纯CH4气氛下制备的106.3Am2/kg大.  相似文献   

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Information on how to construct and improve the State Special Standard of the units of pulsed electric and magnetic field strengths are presented. The need and possibility of extending the time range of the standard in order to ensure uniformity of measurements of the parameters of very short pulses of electromagnetic fields having a pulse length of down to 10-10 sec are considered.Translated from Izmeritelnaya Tekhnika, No. 10, pp. 33–35, October, 2004.  相似文献   

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重点研究共沉淀法制备CoMnNiO系NTC纳米粉体时前驱体反应物浓度对粉体及材料性能的影响,获得了NTC热敏材料制备的优化条件.采用DTA/TG、TEM等方法,对粉体性能进行了研究,测量了不同反应物浓度对粉料烧结致密度及材料B值和阻值的影响.研究发现随着反应物浓度的增加,粉体颗粒尺寸减小,但胶粒聚合程度增加,网状结构变密实.当浓度控制在0.9~1.2mol/L时,粉体粒度分散、均匀性较好,平均颗粒尺寸为20nm左右,反应物浓度太高或太低,都不利于粉料的烧结.综合分析DTA/TG、TEM得出,将煅烧温度控制在(700±20)℃为宜.浓度对材料的B值和阻值的大小影响很小,但对它们的一致性仍有较大影响.浓度为0.9~1.2mol/L时,粉体的烧结性能较好,材料的B值和阻值的一致性较好.  相似文献   

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A composite energy criterion of failure of a force system in relation to test temperature and level of normal and frictional stresses is proposed and a method has been developed for separation from the full mechanical and thermal energy of their effective portions expended on formation and accumulation of damages. The concept has been introduced of the parameters of interaction of different constituents of the effective energy and a method is given for evaluation of them. Particular criteria of thermal force failure have been obtained and understandings of the limits of (mechanical) destruction and of temperature destruction have been introduced. On the basis of experimental results satisfactory correspondence to the test data of the thermal force criterion in the 4 K to T melt range has been established for nickel and aluminum and an analysis has also been made of the change in mechanisms of damage of these materials in connection with varying of the level of stresses and test temperature.Translated from Problemy Prochnosti, No. 1, pp. 11–23, January, 1993.  相似文献   

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