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 Найдено в других БД:Нанотехнологии (2)Труды Института высокотемпературной электрохимии УрО РАН (1)Расплавы (6)
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Поисковый запрос: (<.>K=WC<.>)
Общее количество найденных документов : 51
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1.
Инвентарный номер: нет.
   
   G 96


    Gusev, A. I.
    Mechanical Milling Process Modeling and Making WC Nanocrystalline Powder / A. I. Gusev, A. S. Kurlov // Inorganic Materials. - 2009. - Vol. 45, № 1. - P. 35-42 : il. - Bibliogr. : p. 42 (19 ref.)
ББК 54
Рубрики: ХИМИЧЕСКИЕ НАУКИ
Кл.слова (ненормированные):
КАРБИД ВОЛЬФРАМА -- ПОРОШКИ НАНОКРИСТАЛЛИЧЕСКИЕ
Аннотация: A model of mechanical milling of powders is proposed. It is demonstrated that, during milling, the energy is partially spent in generating microstresses, which hinders the milling process. The model is compared with experiment for tungsten carbide (WC) powder. The average particle size and the value of the microstrains in the as-milled powder are determined from the broadening of x-ray diffraction reflections. Particle size is also evaluated by scanning electron microscopy and sedimentation analysis. It is shown that, with all other things being equal, upon grinding in a planetary-type mill, the resulting particle size is less, the greater the angular velocity of the mill rotation, the longer the milling time, the lighter the weight of the powder milled, and the smaller the initial powder particle size

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2.
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   G 96


    Gusev, A. I.
    Production of nanocrystalline powders by high-energy ball milling: model and experiment [Текст] / A. I. Gusev, A. S. Kurlov // Nanotechnology. - 2008. - Vol. 19, № 26. - С. 265302/1-265302/8. - Библиогр. : с. 265302/8 (8 назв.)
ББК 54
Рубрики: ХИМИЧЕСКИЕ НАУКИ
Кл.слова (ненормированные):
НАНОКРИСТАЛЛИЧЕСКИЕ ПОРОШКИ -- КАРБИД ВОЛЬФРАМА
Аннотация: A model of high-energy ball milling of powders has been proposed. It is demonstrated that part of the energy is consumed for initiation of microstrains ε during milling and, hence, the process of the powder grinding is decelerated. An analytical expression has been deduced describing the size of nanocrystalline powder particles as a function of the milling time. The model and the experiment have been compared, using a powder of tungsten carbide (WC). The average size of the particles and the value of the microstrains in the ball-milled powder were determined by an x-ray method from broadening of diffraction reflections. The size of the particles was also evaluated using scanning electron microscopy and the sedimentation method

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3.
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   H 99


    Ivanovskii, A. L.
    Effect of metal and carbon vacancies on the electronic structure of hexagonal WC and cubic TaC [Text] = Effect of metal and carbon vacancies on the electronic structure of hexagonal WC and cubic TaC / A. L. Ivanovskii, N. I. Medvedeva // Mendeleev Communications. - 2001. - N 1. - P10-12. - Bibliogr.: p. 12 (12 ref.) . - ISSN 0959-9436
ББК 54
Рубрики: ХИМИЧЕСКИЕ НАУКИ
Кл.слова (ненормированные):
МЕТАЛЛИЧЕСКИЕ ВАКАНСИИ -- ВАКАНСИИ МЕТАЛЛИЧЕСКИЕ -- ВАКАНСИИ КАРБОНА -- ЭЛЕКТРОННАЯ СТРУКТУРА -- СТРУКТУРА ЭЛЕКТРОННАЯ -- МЕТОД ЛМТО -- ЛМТО МЕТОД -- КАРБИДЫ МЕТАЛЛОВ -- WC -- W -- C -- ВОЛЬФРАМ -- УГЛЕРОД -- TaC -- Ta -- ТАНТАЛ -- НЕСТЕХИОМЕТРИЯ
Аннотация: The electronic states and energy characteristics of carbon and metal vacancies in hexagonal beta-WC and cubic TaC were examined by the full-potential LMTO method

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4.
Инвентарный номер: нет.
   
   K 93


    Kurlov, A. S.
    Determination of the particle sizes, microstrains, and degree of inhomogeneity in nanostructured materials from X-ray diffraction data [Текст] / A. S. Kurlov, A. I. Gusev // Glass Physics and Chemistry. - 2007. - Vol. 33, № 3. - С. 276-282. - Библиогр. : с. 282 (15 назв.)
ББК 54
Рубрики: ХИМИЧЕСКИЕ НАУКИ
Кл.слова (ненормированные):
НАНОСТРУКТУРНЫЕ МАТЕРИАЛЫ -- РЕНТГЕНОВСКАЯ ДИФРАКЦИЯ -- КАРБИД ВОЛЬФРАМА
Аннотация: The mean particle size, the microstrains, and the degree of inhomogeneity in compacted and dispersed nanostructured materials are determined from the broadening of diffraction reflections. A method is described for separating the contributions from the small size of particles, the microstrains, and the inhomogeneity of materials to the broadening. The application of the proposed method is illustrated using a nanocrystalline powder of tungsten carbide WC.

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5.
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   K 93


    Kurlov, A. S.
    Effect of sintering temperature on the phase composition and microhardness of WC-8 wt % Co cemented carbide [Text] / A. S. Kurlov, A. A. Rempel // Inorganic Materials. - 2007. - Vol. 43, № 6. - P602-607 : il. - Библиогр. : с. 607 (15 назв.)
ББК 54
Рубрики: ХИМИЧЕСКИЕ НАУКИ
Кл.слова (ненормированные):
КАРБИД КОБАЛЬТА -- КАРБИД ВОЛЬФРАМА -- ПОРОШКИ -- СПЕКАНИЕ
Аннотация: The effect of sintering temperature (800–1600°C) on the phase composition, density, and microhardness of WC–8 wt % Co cemented carbide has been studied using x-ray diffraction, scanning electron microscopy, optical microscopy, and density measurements. The results indicate that, during sintering of the starting powder mixture, containing not only WC and Co but also the lower carbide W2C and free carbon, W2C reacts with cobalt metal to form Co3W. At sintering temperatures from 900 to 1200°C, the reaction intermediate is the ternary carbide phase Co6W6C. During sintering at 1300°C, this phase reacts with carbon to form Co3W3C. Sintering at 1000°C and higher temperatures is accompanied by the formation of a cubic solid solution of tungsten carbide in cobalt, β-Co(WC) . The density and microhardness of the sintered samples have been measured as functions of sintering temperature, and the optimal sintering temperature has been determined

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6.
Инвентарный номер: нет.
   
   K 93


    Kurlov, A. S.
    Effect of WC Nanoparticle Size on the Sintering Temperature, Density, and Microhardness of WC–8 wt % Co Alloys / A. S. Kurlov, A. A. Rempel // Inorganic Materials. - 2009. - Vol. 45, № 4. - P. 380-385 : il. - Bibliogr. : p. 385 (10 ref.)
ББК 54
Рубрики: ХИМИЧЕСКИЕ НАУКИ
Кл.слова (ненормированные):
НАНОЧАСТИЦЫ -- КАРБИД ВОЛЬФРАМА -- МИКРОТВЕРДОСТЬ -- КОБАЛЬТ -- СПЛАВЫ
Аннотация: Using X-ray diffraction, scanning electron microscopy, and density measurements, we have studied the effect of WC particle size (20 to 150 nm) on the optimal sintering temperature of the WC–8 wt % Co alloy and the effect of sintering temperature (800–1600°C) on its phase composition, density, and microhardness. The results indicate that, during sintering of the starting powder mixture, the first to form is the ternary carbide phase Co6W6C. At sintering temperatures of 1100°C and above, this phase reacts with carbon to form Co3W3C. Sintering above 1000°C leads to the formation of a cubic solid solution of tungsten carbide in cobalt, β-Co(WC), along with the ternary carbide phases. The density and microhardness of the alloy have been measured as functions of sintering temperature. The use of WC nanopowder has been shown to reduce the optimal sintering temperature of the WC–Co alloy by about 100°C

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7.
Инвентарный номер: нет.
   
   K 93


    Kurlov, A. S.
    Magnetic susceptibility and thermal stability of particle size of nanocrystalline tungsten carbide WC [Текст] / A. S. Kurlov, S. Z. Nazarova, A. I. Gusev // Physics of the Solid State. - 2007. - Vol. 49, № 9. - С. 1780-1786. - Библиогр. : с. 1786 (13 назв.)
ББК 54
Рубрики: ХИМИЧЕСКИЕ НАУКИ
Кл.слова (ненормированные):
МАГНИТНАЯ ВОСПРИИМЧИВОСТЬ -- ТЕРМИЧЕСКАЯ УСТОЙЧИВОСТЬ -- КАРБИД ВОЛЬФРАМА -- НАНОКРИСТАЛЛИЧЕСКИЕ КАРБИДЫ
Аннотация: The magnetic susceptibility χ of coarse-grained and nanocrystalline tungsten carbides was studied in the temperature range 300–1250 K. The temperature dependence of the susceptibility χ(T) of coarse-grained carbide WC is typical of weak Pauli paramagnets and has no specific features. The χ(T) dependence of nanocrystalline carbide (n-WC) in the range 550–920 K exhibits features associated with annealing of microstrains, which leads to a decrease in the contribution of orbital paramagnetism to the magnetic susceptibility of n-WC and initiates precipitation of minor impurities of iron and cobalt as superparamagnetic particles. A nanocrystalline n-WC powder retains a stable particle size of ~55 nm after long annealing at temperatures of 300 to 1200 K, whereas microstrains relax at 550–920 K

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8.
Инвентарный номер: нет.
   
   K 93


    Kurlov, A. S.
    Neutron and x-ray diffraction study and symmetry analysis of phase transformations in lower tungsten carbide W2C [Текст] / A. S. Kurlov, A. I. Gusev // Physical Review B: Condensed Matter and Materials Physics. - 2007. - Vol. 76, № 17. - С. 174115/1-174115/16. - Библиогр. : с. 174115/16 (40 назв.)
ББК 54
Рубрики: ХИМИЧЕСКИЕ НАУКИ
Кл.слова (ненормированные):
НЕЙТРОННАЯ ДИФРАКЦИЯ -- РЕНТГЕНОВСКАЯ ДИФРАКЦИЯ -- КАРБИД ВОЛЬФРАМА
Аннотация: The literature data on the crystal structure of disordered and different ordered phases of the lower tungsten carbide W2C are contradictory. In this context, the symmetry analysis of all possible superstructures of the carbide W2C is performed and the physically possible sequence of phase transformations in W2C carbide is established. Atomic and vacancy ordering in the lower tungsten carbide W2C with the basic hexagonal structure of the L 3 type is studied by the neutron and x-ray diffraction methods. It is found that the trigonal -W2C phase space group P3¯1m is the only ordered phase of the lower tungsten carbide over a wide temperature interval of 2300–1370 K. Trigonal phase -W2C is formed at a temperature of 1900–2300 K most likely by the mechanism of the second-order phase transition. The disorder-order phase transition channel and the structure of the trigonal carbide -W2C are determined. The carbon atom distribution function is calculated for the trigonal -W2C superstructure. The distribution of carbon atoms in the trigonal -W2C phase is described by two long-range order parameters 15 and 17. It is shown that the lower tungsten carbide does not undergo solid-phase decomposition to W and WC over the investigated temperature interval from 2300 to 1370 K. The phase diagram of the W-C system is refined considering data obtained for the -W2C phase

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9.
Инвентарный номер: нет.
   
   K 93


    Kurlov, A. S.
    Particle Size Effects on the Oxidation of Tungsten Carbide Nanopowders / A. S. Kurlov, A. I. Gusev // Russian Journal of Physical Chemistry A. - 2010. - Vol. 84, № 12. - P2095-2101 : il. - Bibliogr. : p. 2101 (17 ref.)
ББК 54
Рубрики: ХИМИЧЕСКИЕ НАУКИ
Кл.слова (ненормированные):
ОКИСЛЕНИЕ -- КАРБИД ВОЛЬФРАМА
Аннотация: The oxidation of tungsten carbide (WC) powders with the average particle size 〈D〉 from 20 to 6000 nm was studied by differential thermal and differential thermogravimetric analyses. WC powders are oxidized, irrespective of their dispersity, to higher oxide WO3. The conclusion was drawn that at smaller particle sizes of WC powder, the oxidation rate increases, and the temperature of the peak of the exo effect decreases. The functional dependences of the temperature of the peak and the activation energy of oxidation on the particle size were determined

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10.
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   K 93


    Kurlov, A. S.
    Tungsten carbides and W-C phase diagram [Text] / A. S. Kurlov, A. I. Gusev // Inorganic Materials. - 2006. - Vol. 42, № 2. - P. 121-127 : il. - Библиогр. : с. 127 (21 назв.)
ББК 54
Рубрики: ХИМИЧЕСКИЕ НАУКИ
Кл.слова (ненормированные):
КАРБИД ВОЛЬФРАМА -- ФАЗОВЫЕ ДИАГРАММЫ -- СТРУКТУРА КРИСТАЛЛИЧЕСКАЯ -- МАГНИТНАЯ ВОСПРИИМЧИВОСТЬ
Аннотация: The crystal structures of the tungsten monocarbide δ-WC and the disordered lower carbide β-W2C are studied. Using magnetic susceptibility measurements, the hexagonal carbide δ -WC is shown to be stable from 300 to 1200 K. The sequence of phase transformations associated with β-W2C ordering is analyzed. The temperature and composition stability limits of the cubic carbide γ-WC1 –x are evaluated, and the first data are presented on the variation of its lattice parameter with composition. An optimized W–C phase diagram is proposed which takes into account detailed structural and phase-equilibrium data for tungsten carbides

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