Papers by Keyword: Nanocomposite Powder

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Authors: Ovidiu Dumitrescu, Yves Jorand, Gilbert Fantozzi
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Authors: Yong Zhong Jin, Fa Ming Ye, Xian Guang Zeng, Rui Song Yang
Abstract: Cr3C2-WC-Ni nanocomposite powders with ~50-100 nm were synthesized from precursors by vacuum-aided carbothermal reduction at only 750 °C for 2 h. The phase composition and microstructure of the synthesized products were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The present study shows that Cr3C2-WC-Ni nanocomposite powders contain two kinds of solid-solution phases, namely Ni and (Cr, W)3C2 solid solution, respectively. WC and W2C phases do not appear inreaction products due to the dissolution of tungsten atoms into Ni and Cr3C2 unit cells. Especially, there is a change of the crystalline structure for (Cr, W)3C2 phase from 750 °C to 800 °C.
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Authors: Traian Florin Marinca, Bogdan V. Neamţu, Florin Popa, Ionel Chicinaş, Olivier Isnard
Abstract: Composite powder of Fe/Fe2O3 type was synthesized by mechanical milling using commercially Fe and Fe2O3 powders in mass ratio of 35/65. The milling process leads to the powder homogenization, powder activation and formation of some Fe/Fe2O3 composite particles. The Fe/Fe2O3 composite powder obtained by mechanical milling and the un-milled Fe/Fe2O3 mixture were subjected to the reactive sintering procedure in argon atmosphere at 1100 °C for 6 hours. The sintering procedure promotes the reaction of the Fe with the Fe2O3 and the result is a sintered composite compact of Fe/Fe3O4/FeO type. The microstructure of the Fe/Fe3O4/FeO sintered composite compacts presents iron clusters in an oxide matrix. A more homogeneous iron clusters size and distribution in oxide matrix is observed in the case of the sintered compact obtained from mechano-activated powder. The X-ray diffraction (XRD), laser particles size analysis (LPSA), optical (OM) and scanning electron (SEM) microscopies techniques were used for the investigations.
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Authors: Kiyoshi Itatani, Ryuji Tsukamoto, Hiroshi Uchida, Mamoru Aizawa, Anne C.A. Delsing, H.T. Hintzen, Isao Okada
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Authors: Dae Gun Kim, Gil Su Kim, Jin Chun Kim, Sung Tag Oh, Young Do Kim
Abstract: The sintered microstructure homogeneity of W-15wt%Cu nanocomposite powders prepared from W-CuO mixture was investigated. The increment of heating rate considerably affected the homogeneity of sintered microstructure. In case of the higher heating rate, the microstructure was more homogeneous than that of the lower heating rate by reason of Cu- exudation during heating-up process.
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Authors: A. Jabbarnia, Saeed Heshmati-Manesh
Abstract: Mechanical alloying technique was used to produce an intermetallic based composite powder. Mechanical activation of aluminum and nickel oxide powder mixture using a high energy ball mill resulted in a self-propagating high temperature synthesis through which nickel oxide was reduced by metallic aluminum and produced nickel aluminide and alumina composite powder. Effect of milling time on crystallite sizes of the product phases was investigated. The synthesized product was characterized by scanning electron microscope and X-ray diffraction. It was shown that increased milling time resulted in crystallite size reduction and peak broadening in XRD patterns. Calculation of the mean crystallite sizes of the product phases indicated that they are in nano scale. The results were further confirmed by transmission electron microscopy.
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Authors: Claudiu Nicolicescu, Mariana Ciobanu, Lucia Leonat
Abstract: The paper presents the experimental work regarding the elaboration of some nanocomposite powders with higher SiC content. For the research, three types of mixtures were prepared: 90SiC-10Al, 70SiC-30Al and 60SiC-40Al using mechanical alloying (MA) technique. The MA was carried out in a vario planetary ball mill Pulverisette 4 for 5 hours using different conditions: - the shock mode (the main disk speed 400 rpm and the planets speed -800 rpm); - the friction mode (the main disk speed 400 rpm and the planets speed 800 rpm). The resulting mixtures was investigated by scanning electron microscopie (SEM), X-ray diffraction pattern (RDX), energy dispersive X-ray analysis (EDAX) and particle size distribution. After 5 hours of MA it is observed that the mixture obtained in the friction mode conditions have a homogenous structure and the particle size distribution is better than the particle size distribution of the mixture obtained in the shock mode conditions.
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Authors: Xiao Liang Shi, Gang Qin Shao, Xing Long Duan
Abstract: WC-10Co nanocomposite powders prepared by spray pyrogenation-continuous reduction and carburization technology were consolidated by vacuum sintering plus hot isostatic pressing (HIP). Influences of ball-milled time on properties and microstructure of ultrafine WC-10Co cemented carbide were investigated. The results show that ultrafine WC-10Co cemented carbides can reach 99.79% relative density, and transverse rupture strength is more than 3750MPa, Rockwell A hardness is more than 92.6, the average grain size is less than 440 nm, when ball-milled time is 48 hours, ultrafine WC-10Co cemented carbide with excellent properties and fine microstructure is obtained. The optimum ball-milling time is 48 hours.
159
Authors: Xiao Liang Shi, Gang Qin Shao, Xing Long Duan
Abstract: WC-10Co nanocomposite powders prepared by spray pyrogenation-continuous reduction and carburization technology were consolidated by vacuum sintering plus hot isostatic pressing (HIP). Influences of ball-milled time on properties and microstructure of ultrafine WC-10Co cemented carbide were investigated. The results show that ultrafine WC-10Co cemented carbides can reach 99.79% relative density, and transverse rupture strength is more than 3750MPa, Rockwell A hardness is more than 92.6, the average grain size is less than 440 nm, when ball-milled time is 48 hours, ultrafine WC-10Co cemented carbide with excellent properties and fine microstructure is obtained. The optimum ball-milling time is 48 hours.
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