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Zhao X.M.,General Research Institute for Nonferrous Metals, China | Xu J.,General Research Institute for Nonferrous Metals, China | Zhu X.X.,General Research Institute for Nonferrous Metals, China | Zhu X.X.,Beijing COMPO Advanced Technology Co. | Zhang S.M.,General Research Institute for Nonferrous Metals, China
Materials Science Forum | Year: 2011

The aspiration pressure variation at the tip of metal delivery tube in the supersonic atomization nozzle during gas-only atomization performance had been investigated in this work. The results reveal that the aspiration pressure is subambient at all operating pressures. A general trend is that with increasing atomization gas pressure, the value of aspiration pressure decreases at P 0 between 0.5 and 1.5MPa, then increases as P0 ranges from 1.5∼3.5MPa, finally decreases again at higher gas pressure (P 0>∼3.5MPa). When P0>2.0MPa, as the included angle α augments, the aspiration pressure ΔP increases. Meanwhile, the change range of aspiration pressure ΔP significantly enlarges when the jet included angle α raises from 16 to 28°. The lager is the apex angle β of metal delivery tube, the greater is the aspiration pressure ΔP. And as the protrusion length of melt delivery tube h increases, the aspiration pressure ΔP decreases gradually. © (2011) Trans Tech Publications. Source


Yin J.,Central South University | Zhang H.-B.,Central South University | Xiong X.,Central South University | Tan C.,Central South University | Lu C.-T.,Beijing COMPO Advanced Technology Co.
Fenmo Yejin Cailiao Kexue yu Gongcheng/Materials Science and Engineering of Powder Metallurgy | Year: 2014

Carbon fiber reinforced carbon and copper (C/C-Cu) composites were prepared by a combination of chemical vapor infiltration (CVI) and melt copper impregnation by pressure. 3 kinds of C/C-Cu composites with different densities of porous carbon/carbon composites (C/C substrates) were prepared and their compressive properties were tested on CSS-44100 electronic tensile testing machine. The effect of C/C substrate density on compressive property of C/C-Cu composites was studied. The results show that C/C-Cu composites have high compressive strengths, which have small differences between parallel and vertical direction. With the increase of the C/C substrate density, the compressive strength of C/C-Cu composites increases and the anisotropy improves. The one with highest density has the highest compressive strength of 323.8 and 326.6 MPa. The composites are shearing along with 45° diagonal line in vertical direction, while destroyed by delaminating split in parallel direction. ©, 2014, Central South University. All right reserved. Source


Zhao X.,General Research Institute for Nonferrous Metals, China | Xu J.,General Research Institute for Nonferrous Metals, China | Zhu X.,Beijing COMPO Advanced Technology Co. | Zhang S.,General Research Institute for Nonferrous Metals, China
Fenmo Yejin Jishu/Powder Metallurgy Technology | Year: 2010

The aspiration pressure variation at the tip of metal delivery tube in the supersonic atomization nozzle during gas-only atomization performance had been investigated in this work. Effects of atomization gas pressure P0, jet included angle α, the apex angle β and the protrusion length h of metal delivery tube on aspiration pressure ΔP were measured. The results reveal that the aspiration pressure is subatmospheric under all operating pressures. A general trend is that with increasing atomization gas pressure, the value of aspiration pressure decreases in the range of 0.5~1.5 MPa, then increases in the range of from 1.5~3.5 MPa, finally decreases again under higher gas pressure (P0>3.5 MPa). The larger the apex angle of metal delivery tube, the greater the aspiration pressure. With the jet included angle α of the nozzle decreasing, the aspiration pressure increases. Only the atomization gas pressure reaches and above 3.23 MPa, as the protrusion length increases, the aspiration pressure decreases. Source


Zhao X.-M.,General Research Institute for Nonferrous Metals, China | Xu J.,General Research Institute for Nonferrous Metals, China | Zhu X.-X.,General Research Institute for Nonferrous Metals, China | Zhu X.-X.,Beijing COMPO Advanced Technology Co. | And 2 more authors.
International Journal of Minerals, Metallurgy and Materials | Year: 2012

17-4PH stainless steel powders were prepared using a supersonic nozzle in a close-coupled gas atomization system. The characteristics of powder particles were carried out by means of a laser particle size analyzer, scanning electron microscopy (SEM), and the X-ray diffraction (XRD) technique. The results show that the mass median particle diameter is about 19.15 μm. Three main types of surface microstructures are observed in the powders: well-developed dendrite, cellular, and cellular dendrite structure. The XRD measurements show that, as the particle size decreases, the amount of fcc phase gradually decreases and that of bcc phase increases. The cooling rate is inversely related to the particle size, i.e., it decreases with an increase in particle size. © University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg 2012. Source


Xu X.-F.,East China Jiaotong University | Xu X.-F.,Central South University | Hong L.-L.,East China Jiaotong University | Xiao P.,Central South University | And 2 more authors.
Fenmo Yejin Cailiao Kexue yu Gongcheng/Materials Science and Engineering of Powder Metallurgy | Year: 2013

Using nickel particles as catalysts, C3H6, H2, N2 as carbon source, carrier gas and diluent gas, respectively, the carbon nano-tube/carbon nano-fiber (CNT/CNF) were self-grown on the surface of carbon fibers (CFs) by the method of catalytic chemical vapor deposition (CCVD) to make surface modification of CF. The structures of CNT/CNF were observed by SEM and TEM. Surface structure of untreated and treated carbon fiber (CF) were observed by Raman spectra. The results show that the surface modification can decrease the amount of disordered carbon and amorphous carbon, improve the surface graphitization of carbon fiber. A new "Fracture-Adsorption-Diffusion-Deposition" mechanism model for CCVD growth of CNT/CNF is suggested based on these analyses. Source

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