• Resources Recycling
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• v.31 no.4
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• pp.19-25
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• 2022

In this study, tungsten carbide (WC) powder was prepared using a novel recycling process for hard metal sludge that does not use ammonium paratungstate. Instead of ammonia, acid was used to remove the sodium and crystallized tungstate, resulting in the formation of tungstic acid (H₂WO₄). The WC powder was successfully synthesized by the carbothermal reduction of tungstic acid through H₂O decomposition, reduction of WO₃ to W, and formation of WC. The carbon content and holding time at the carbothermal reduction temperature were optimized to remove free carbon from the WC powder. As a result, most of the free carbon in the WC powder prepared from sludge was removed, and the content of free carbon in the synthesized WC powder was lower than that in commercial WC powder. Moreover, the crystallite size of WC prepared from H₂WO₄ was much smaller than that of commercial micron-sized WC powder produced from APT. The small crystallite size of WC induces grain growth during the sintering of the WC-Co composite; thus, a WC-Co composite with large WC grains was fabricated using the WC powder prepared from H₂WO₄. The large WC grains affected the mechanical properties of the WC-Co composite. Further, due to the large grain size, the WC-Co composite fabricated from H₂WO₄ exhibited a higher toughness than that of the WC-Co composite prepared from commercial WC powder.

• Resources Recycling
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• v.26 no.6
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• pp.91-96
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• 2017

Tungsten (W) recovery from tungsten carbide (WC) was researched by alkali melt followed by water leaching. The experiments of alkali melt were carried out with the change of the sort of alkali material, heating temperature, and the heating duration. Water leaching of W was performed in the fixed conditions ($25^{\circ}C$, 2 hr., slurry density: 10 g/L). From the mixture of WC and sodium nitrate ($NaNO_3$) in the molar ratio of 1:2, treated at $400^{\circ}C$ for 6 hours, only 63.3% of W might be leached by water leaching. With the increase of sodium hydroxide (NaOH) as a melting additive, the leachability increased. Finally it reached to 97.8 % with the melted mixture of ($WC:NaNO_3:NaOH$) in the ratio of (1:2:2). This imply that NaOH may play a role as a reaction catalyst by lowering Gibb's free energy for alkali melt reaction for WC.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.403-405
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• 2009

RF-스퍼터링법을 사용하여 메탄올 산화반응을 위해 박막형 전극을 제조하였다. 전극은 텅스텐 탄화물(WC)과 텅스텐 산화물($WO_3$), 그리고 백금(Pt) 타겟을 이용하였으며 그 구조적 특성과 전기화학적 특성을 TEM(Transmission electron microscopy와 CV(Cyclic Voltametry)를 통하여 촉매적 활성을 측정해 보았다. 같은 양의 백금과의 활성을 비교하고 활성을 확인하였다.

• Korean Journal of Crystallography
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• v.5 no.1
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• pp.39-50
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• 1994

Diamond thin films were deposited on silicon, molybdebum, titanum and tugsten substrates, and were chlwntnizen using scanning electron microscopy, X-ray diffraction analysis and Raman spectroscopy. From the result of experiment in various deposition periods, it was found that found that were nucleated and grown on interlayed carbide layers, which were formed on refractory metal substrates at the initial stage of.

• Resources Recycling
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• v.19 no.4
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• pp.41-50
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• 2010

A fundamental study was carried out to develop a process for recycling tungsten and cobalt from WC-Co hardmetal sludge generated in the manufacturing process of hardmetal tools. The complete extraction of cobalt and simultaneous formation of tungstic was achieved by treating the sludge using aqua regia. The effect of aqua regia concentration, reaction temperature and time, pulp density on cobalt leaching and tungstic acid formation was investigated. The complete leaching of cobalt was attained at the optimum conditions: 100 vol.% aqua regia concentration, $100^{\circ}C$ temperature, 60 min. reaction time and 400 g/L pulp density. A complete conversion of tungsten carbide of the sludge to tungstic acid was however, obtained at the pulp densities lower than 150 g/L under the above condition. The progress of reaction during the aqua regia treatment of the sludge was monitored through the XRD phase identification of the residue. The metallic impurities in the tungstic acid so produced could be further removed as insoluble residues by dissolving the tungsten values in ammonia solution. The ammonium paratungstate($(NH_4)_{10}{\cdot}H_2W_{12}O_{42}{\cdot}4H_2O$) of 99.85% purity was prepared from the ammonium polytungstate solution by the evaporation crystallization method.

• Particle and aerosol research
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• v.5 no.4
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• pp.153-158
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• 2009

Tungsten carbide powder was fabricated with carbothermal reaction by pulsed electric current flowing in compact of tunsten oxide and carbon. The mixed powder of tunsten oxide and carbon was ball-milled into ultrafine powders. The mixed powder of tungsten oxide and carbon was put into carbon mold and heat-treated at $1050{\sim}1200^{\circ}C$ by pulsed electric current flowing. The formation of tungsten carbide powder could be achieved by heat treatment at $1200^{\circ}C$ for 10 minitues.