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Yang H.,National University of Defense Technology | Zhou X.,National University of Defense Technology | Yu J.,National University of Defense Technology | Wang H.,National University of Defense Technology | Huang Z.,Chongyi Zhangyuan Tungsten Co.
Ceramics International | Year: 2015

SiC/SiC composites were fabricated by the PIP process via microwave and conventional heating from 800. °C to 1200. °C. The flexural properties and microstructures of the as-fabricated SiC/SiC composites were investigated. The results indicated that the flexural strength and toughness have the same changing tendency for both conventional and microwave sintering. However, at the same PIP sintering temperature, the flexural properties of the microwave sintered SiC/SiC are higher than that of the conventional sintered ones. The higher residual strength of SiC fibers properties and more cracks in the composite matrix resulting from higher heating rates of the microwave sintering brought about the better flexural properties. © 2015 Elsevier Ltd and Techna Group S.r.l. Source


Yang H.,National University of Defense Technology | Zhou X.,National University of Defense Technology | Yu J.,National University of Defense Technology | Wang H.,National University of Defense Technology | Huang Z.,Chongyi Zhangyuan Tungsten Co.
Ceramics International | Year: 2015

In order to investigate the effect of microwave sintering time on the mechanical properties of SiC/SiC composites, four groups of SiC/SiC composites were fabricated via polymer impregnation and pyrolysis (PIP) process using microwave heating with different sintering time- 0.5. h, 1.0. h, 1.5. h and 2.0. h (at 1100. °C) at each PIP cycle. The flexural properties, the interfacial debonding strength between SiC fiber and matrix of the fabricated SiC/SiC composites and the SiC fiber filament strength after heat treatment were investigated. The results indicated that after heat treatment the residual strength of SiC fibers as reinforcement decreased and the interfacial debonding strength increased with the increase of the microwave sintering time at each PIP cycle, which together resulted in the changing tendency that the flexural strength and toughness of the as-fabricated SiC/SiC composites increased firstly and then decreased. © 2015 Elsevier Ltd and Techna Group S.r.l. Source


Wan L.,Jiangxi University of Science and Technology | Yang S.,Xinda Gold and Silver Development Center | Zhao L.,Chongyi Zhangyuan Tungsten Co. | Li H.,Jiangxi University of Science and Technology
Advanced Materials Research | Year: 2012

In the paper, the four core technologies "low cost and efficient decomposition," "APT property control", "fuzzy exchange and super desorption," "liquid, gas efficient closed-circuit" in Zhangyuan Tungsten Co.,Ltd in the past 20 years are elaborated in all aspects,and the research of wolframite and scheelite closed-circuit smelting process and zero emission technology are also introduced. © (2012) Trans Tech Publications, Switzerland. Source


Yang H.,National University of Defense Technology | Zhou X.,National University of Defense Technology | Yu J.,National University of Defense Technology | Wang H.,National University of Defense Technology | Huang Z.,Chongyi Zhangyuan Tungsten Co.
Journal of Alloys and Compounds | Year: 2016

SiC/SiC composites were fabricated by polymer impregnation and pyrolysis (PIP) process via microwave and conventional heating at 800 °C, 900 °C, 1000 °C and 1100 °C. The effects of sintering heating types and sintering temperatures on the densification process and pore distributions of the fabricated SiC/SiC composites were studied. The densification processes were discussed in the form of the weight gain rates at each PIP cycle. The pore location distributions were observed by scanning electron microscopy (SEM) and computed tomography (CT) technique. The porosity and pore size distributions were quantified by the mercury intrusion test. The results indicate that lower heating rates and higher sintering temperatures are benefit to the densification of the SiC/SiC composites. But the more micro-cracks generated from higher heating rates of microwave sintering (∼40 °C/min) make the flexural strength and toughness of the SiC/SiC composites higher than that of the conventional sintered ones. © 2015 Elsevier B.V. All rights reserved. Source


Li P.,China University of Geosciences | Li P.,Chinese Academy of Geological Sciences | Liu S.B.,Chinese Academy of Geological Sciences | Shi G.H.,China University of Geosciences | Zhang S.D.,Chongyi Zhangyuan Tungsten Co.
Yanshi Xuebao/Acta Petrologica Sinica | Year: 2015

There are more than one handred metal deposits (chromium, nickle, iron, gold etc. ) distributed in three greenstone belts (Maevatanana, Andriamena and Beforona) from Central Madagascar. In this investigation, we reported major and trace element compositions, LA-MC-ICP-MS zircon U-Pb ages and Lu-Hf isotopic compositions of granites in the greenstone belt from the southwestern Maevatanana, Central-North Madagascar. The granites, mainly composed of biotite and adamellite, belong to aluminous to slight peraluminous K-rich calc-alkaline series and are characterized by high LILE contents (e. g. Rb, Ba, K) , low HFSE contents (e.g. Nb, Ta, Ti) , with ∑ REE = 92.02 × 10-6 and A/CNK = 1.01. The ages of the granite range between 739 ∼ 767Ma. All εHf(t) values are negative, suggesting that their magma sources were from continental basement. Two-stage Hf modle ages of the overgrown and inherited zircons are similar, suggesting that forming age of protolith of the granite was the same as the biotite-amphibole-plagioclase gneiss, and the granite formed by partial melting of the basement. Geochemical features of the granite show similarity to type-I granite, resembling characterstics of the adakite. lt is suggested that the granite was associated with arc magmatism of continental convergence margin between the Tanzanian craton and Dharwar craton, lndia, during Meso-Neoproterozoic (824 ∼ 720Ma) when Rodinia supercontinent broke up with close of the Mozambique Ocean. Source

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