- Phase Transformation by the Oxidation of Air-passivated W and Mo Nanopowders Produced by an Electrical Explosion of Wires
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Young-Soon Kwon, Ji-Soon Kim, Alexander A. Gromov, Moon-Hee Hong
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J Korean Powder Metall Inst. 2004;11(2):130-136.
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DOI: https://doi.org/10.4150/KPMI.2004.11.2.130
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- The passivation and oxidation process of tungsten and molybdenum narlopowders, produced by electrical explosion of wires was studied by means of FE-SEM, XPS. XRD, TEM, DIA-TGA and sire distribution analysis. In addition, the phase transformation of W and Mo nanopowders under oxidation in air was investigated. A chemical process is suggested for the oxidation of W and Mo nano-particles after a comprehensive testing of passivated and oxidized powders.
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Citations
Citations to this article as recorded by  - Preparation of Mo nanopowders through hydrogen reduction of a combustion synthesized foam-like MoO2 precursor
Siyong Gu, Mingli Qin, Houan Zhang, Jidong Ma, Xuanhui Qu
International Journal of Refractory Metals and Hard Materials.2018; 76: 90. CrossRef
- A Study on the Reduction Mechanism of Tungsten and Copper Oxide Composite Powders
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Seong Lee, Moon-Hee Hong, Eun-Pyo Kim, Sung-Ho Lee, Joon-Woong Noh
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J Korean Powder Metall Inst. 2003;10(6):422-429.
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DOI: https://doi.org/10.4150/KPMI.2003.10.6.422
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- The reduction mechanism of the composite powders mixed with WO_3 and CuO has been studied by using thermogravimetry (TG), X-ray diffraction, and microstructure analyses. The composite powders were made by simple Turbula mixing, spray drying, and ball-milling in a stainless steel jar with the ball to powder ratio of 32 to 1 at 80 rpm for 1 h without process controlling agents. It is observed that all the oxide composite powders are converted to W-coated Cu composite powder after reducing treatment under hydrogen atmosphere. For the formation mechanism of W-coated Cu composite powder, the sequential reduction steps are proposed as follows: CuO contained in the ball-milled composite powder is initially reduced to Cu at the temperature range from 200°C to 300°C. Then, WO_3 powder is reduced to W O_2 via W O_2.9 and W O_2.72 at higher temperature region. Finally, the gaseous phase of WO_3(OH)_2 formed by reaction of WO_2 with water vapour migrates to previously reduced Cu and deposits on it as W reduced by hydrogen. The proposed mechanism has been proved through the model experiment which was performed by using Cu plate and WO_3 powder.
- A Study on the Microstryctural Evoulution of the Reagion Aheas of Craters Created by Copper and W-Cu Shaped Charge Jets
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Seong Lee, Moon-Hee Hong, Woon-Hyung Baek
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J Korean Powder Metall Inst. 1999;6(1):69-74.
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- The microstructure of the reagion of carters, created by Cu and W-Cu shaped charge jets, in a 1020 mild steel target has been intestiaged. The region ahead of the crater created by the Cu shaped charge jet, reveals dramatic grain refinement implying the occurrence of a dynamic recrystallization, while that of W-Cu one dose a martensitic transformation indicative of heating up to an austenitic region followed by rapid cooling.The impacting pressure calculated when the W-Cu shaped charge jet encounters the target is higher than that of the Cu one. The micro-hardness of the region ahead of the crater created by the W-Cu shaped charge jet is also higher than that of the Cu one. The microstructure of W-Cu slug remained in the inside of the craters depicts the occurrence of the remarkable elongation of W particles during the liner collaphse. From these results, the microstructural variation of the region ahead of the crater with Cu and W-Cu shaped charge jets is discussed in trems of the pressure dependency of the transformation region of ferrite and austenite phases.
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