The Experts below are selected from a list of 3228 Experts worldwide ranked by ideXlab platform

Guo-hua Zhang - One of the best experts on this subject based on the ideXlab platform.

  • fabrication of ultrafine and high purity tungsten carbide powders via a Carbothermic Reduction carburization process
    Journal of Alloys and Compounds, 2019
    Co-Authors: Kaifei Wang, Guodong Sun, Guo-hua Zhang
    Abstract:

    Abstract In the current study, ultrafine and high-purity tungsten carbide (WC) powders are successfully prepared by a two-step process: Carbothermic Reduction of WO3 followed by carbonization reaction. The effects of the C/WO3 molar ratio, reaction temperature and reaction time on the phase transition and morphology evolution of the products are investigated. During the Carbothermic Reduction process, all the oxygen in yellow tungsten trioxide (WO3) is removed by carbon to generate a mixture of W, W2C and WC at 1100 °C; and then the as-prepared powder is mixed with an appropriate content of carbon black and carbonized at 1200 °C. The carbon content in the finally obtained WC powders is almost equal to the theoretical value. Furthermore, it is found that a high C/WO3 molar ratio at the first stage is beneficial for decreasing the particle size of the WC powders. When the C/WO3 molar ratio is 3.5, the single phase WC with a particle size of about 200 nm can be obtained. Therefore, this Carbothermic Reduction–carburization process may provide a simple, low-cost, and high efficiency route to prepare the WC powders in a large-scale.

  • Fabrication of ultrafine and high-purity tungsten carbide powders via a Carbothermic Reduction–carburization process
    Journal of Alloys and Compounds, 2019
    Co-Authors: Kaifei Wang, Guodong Sun, Guo-hua Zhang
    Abstract:

    Abstract In the current study, ultrafine and high-purity tungsten carbide (WC) powders are successfully prepared by a two-step process: Carbothermic Reduction of WO3 followed by carbonization reaction. The effects of the C/WO3 molar ratio, reaction temperature and reaction time on the phase transition and morphology evolution of the products are investigated. During the Carbothermic Reduction process, all the oxygen in yellow tungsten trioxide (WO3) is removed by carbon to generate a mixture of W, W2C and WC at 1100 °C; and then the as-prepared powder is mixed with an appropriate content of carbon black and carbonized at 1200 °C. The carbon content in the finally obtained WC powders is almost equal to the theoretical value. Furthermore, it is found that a high C/WO3 molar ratio at the first stage is beneficial for decreasing the particle size of the WC powders. When the C/WO3 molar ratio is 3.5, the single phase WC with a particle size of about 200 nm can be obtained. Therefore, this Carbothermic Reduction–carburization process may provide a simple, low-cost, and high efficiency route to prepare the WC powders in a large-scale.

  • Carbothermic Reduction of Panzhihua ilmenite in vacuum
    Vacuum, 2017
    Co-Authors: Guo-hua Zhang, Hai-peng Gou, Kuo-chih Chou
    Abstract:

    Abstract The Carbothermic Reduction of Panzhihua ilmenite with activated carbon in vacuum was investigated by isothermal experiments over the temperature range of 1473–1773 K. The reaction mechanism of the impurity elements in vacuum was investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and thermodynamic calculation. It was found that when the reaction temperature was higher than 1673 K and the reaction time was longer than 4 h, the main phases of the final products obtained at 10 Pa were Fe and TiC, without the presence of MgO and MgAl 2 O 4 which existed when roasting at 1 atm in argon atmosphere. The contents of Mg and Mn in the products decreased with increasing the reaction temperature or lowering the pressure. After the Carbothermic Reduction process, the main impurity elements of Si and Al were dissolved in the iron.

  • Kinetic study on Carbothermic Reduction of ilmenite with activated carbon
    Transactions of Nonferrous Metals Society of China, 2017
    Co-Authors: Hai-peng Gou, Guo-hua Zhang, Kuo-chih Chou
    Abstract:

    Abstract The Carbothermic Reduction of Panzhihua ilmenite with various additions of activated carbon was investigated by isothermal experiments over the temperature range of 1373 to 1773 K in the argon atmosphere. According to the reaction kinetics recorded by the infrared gas analyzer, it was found that the amount of carbon addition had little influence on the reaction rates at various temperatures except 1473 K. When the reaction temperature was above the eutectic temperature of 1427 K of Fe–C binary system, part of carbon would dissolve into Fe to form a liquid phase, which made the liquid Fe as a diffusion channel of carbon to diffuse to the reaction interface. The Carbothermic Reduction above 1573 K obeyed the shrinking-core model. The mass fraction of TiC could be determined by the standard addition technique.

  • Mechanism and kinetics of the Carbothermic Reduction of titanium-bearing blast furnace slag
    Metallurgical Research & Technology, 2016
    Co-Authors: Yu-lan Zhen, Guo-hua Zhang, Kuo-chih Chou
    Abstract:

    The Carbothermic Reduction experiments were carried out for titanium-bearing blast furnace slag from Panzhihua Iron and Steel Company in argon atmosphere at high temperatures. The effects of Reduction temperature, isothermal treatment time and carbon particle sizes on the formation of TiC were studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). The SEM pictures show that the size of C has little influence on the particle size of TiC. The experimental results show that the shrinking core model is applicable and the Carbothermic Reduction is controlled by the chemical reaction. The apparent activation energy of reaction could be obtained to be 69.16 kJ/mol.

Richard A. Davis - One of the best experts on this subject based on the ideXlab platform.

  • Solar Carbothermic Reduction of Dolomite: Direct Method for Production of Magnesium and Calcium
    Industrial & Engineering Chemistry Research, 2020
    Co-Authors: Hamed Abedini Najafabadi, Nesrin Ozalp, Michael Epstein, Richard A. Davis
    Abstract:

    Solar Carbothermic Reduction offers a promising approach for the clean production of several metals from their oxides with significantly lower CO2 emission compared to common pyrometallurgical proc...

  • Solar Carbothermic Reduction of Dolime as a Promising Option To Produce Magnesium and Calcium
    Industrial & Engineering Chemistry Research, 2019
    Co-Authors: Hamed Abedini Najafabadi, Nesrin Ozalp, Michael Epstein, Richard A. Davis
    Abstract:

    The use of solar energy to produce metals from their oxides via the Carbothermic Reduction process is a cleaner alternative to traditional combustion-based processes with an added value of a significantly reduced CO2 emission footprint. In this study, the potential contribution of solar energy to the pyrometallurgical production of magnesium was analyzed and compared to the common industrial process. The most energy-consuming step is the Carbothermic Reduction of the oxide. The Reduction was thermodynamically examined and experimentally investigated. While previous studies in the field were based mostly on using MgO, this work focused on dolomite (CaCO3·MgCO3) as the feedstock for the Carbothermic Reduction process. A thermogravimeter (TGA) was used to investigate the kinetics of the reaction under different conditions. The thermogravimetric results show that a full Reduction of MgO in dolime (calcined dolomite, MgO·CaO) is achievable around 1600 °C under atmospheric pressure. According to the results, at...

Kaifei Wang - One of the best experts on this subject based on the ideXlab platform.

  • fabrication of ultrafine and high purity tungsten carbide powders via a Carbothermic Reduction carburization process
    Journal of Alloys and Compounds, 2019
    Co-Authors: Kaifei Wang, Guodong Sun, Guo-hua Zhang
    Abstract:

    Abstract In the current study, ultrafine and high-purity tungsten carbide (WC) powders are successfully prepared by a two-step process: Carbothermic Reduction of WO3 followed by carbonization reaction. The effects of the C/WO3 molar ratio, reaction temperature and reaction time on the phase transition and morphology evolution of the products are investigated. During the Carbothermic Reduction process, all the oxygen in yellow tungsten trioxide (WO3) is removed by carbon to generate a mixture of W, W2C and WC at 1100 °C; and then the as-prepared powder is mixed with an appropriate content of carbon black and carbonized at 1200 °C. The carbon content in the finally obtained WC powders is almost equal to the theoretical value. Furthermore, it is found that a high C/WO3 molar ratio at the first stage is beneficial for decreasing the particle size of the WC powders. When the C/WO3 molar ratio is 3.5, the single phase WC with a particle size of about 200 nm can be obtained. Therefore, this Carbothermic Reduction–carburization process may provide a simple, low-cost, and high efficiency route to prepare the WC powders in a large-scale.

  • Fabrication of ultrafine and high-purity tungsten carbide powders via a Carbothermic Reduction–carburization process
    Journal of Alloys and Compounds, 2019
    Co-Authors: Kaifei Wang, Guodong Sun, Guo-hua Zhang
    Abstract:

    Abstract In the current study, ultrafine and high-purity tungsten carbide (WC) powders are successfully prepared by a two-step process: Carbothermic Reduction of WO3 followed by carbonization reaction. The effects of the C/WO3 molar ratio, reaction temperature and reaction time on the phase transition and morphology evolution of the products are investigated. During the Carbothermic Reduction process, all the oxygen in yellow tungsten trioxide (WO3) is removed by carbon to generate a mixture of W, W2C and WC at 1100 °C; and then the as-prepared powder is mixed with an appropriate content of carbon black and carbonized at 1200 °C. The carbon content in the finally obtained WC powders is almost equal to the theoretical value. Furthermore, it is found that a high C/WO3 molar ratio at the first stage is beneficial for decreasing the particle size of the WC powders. When the C/WO3 molar ratio is 3.5, the single phase WC with a particle size of about 200 nm can be obtained. Therefore, this Carbothermic Reduction–carburization process may provide a simple, low-cost, and high efficiency route to prepare the WC powders in a large-scale.

Yongnian Dai - One of the best experts on this subject based on the ideXlab platform.

  • Magnesium Technology 2015 - Environmental Impact of Magnesium Production by Carbothermic Reduction in Vacuum
    Magnesium Technology 2015, 2015
    Co-Authors: Hongxiang Liu, Dachun Liu, Tian Yang, Yang Bin, Yongnian Dai
    Abstract:

    Based on the practice of magnesium production via Carbothermic Reduction in vacuum, the pollutants were calculated for exhaust gas, waste water, waste residue, noise. And a quantitative evaluation of the environmental impact was carried out.

  • Behavior Analysis of CaF 2 in Magnesia Carbothermic Reduction Process in Vacuum
    Metallurgical and Materials Transactions B, 2012
    Co-Authors: Tian Yang, Bin Yang, Yongnian Dai, Sen Geng
    Abstract:

    Magnesium production by Carbothermic Reduction of magnesia with CaF2 in vacuum was investigated experimentally by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and thermodynamic analysis. Thermodynamic calculations indicate that magnesium was generated by a Carbothermic Reduction among MgO-C system, which should be above 1500 K (1227 °C) (50 Pa). According to the Carbothermic Reduction analysis, the CaF2 does not participate in the Carbothermic process. The experimental results demonstrated that the mass loss increased along with increasing CaF2. The percentage was up to 92 pct with 5 pct CaF2.The Reduction degree increased with CaF2 more than it without CaF2 obviously. Considering the Reduction degree and economic benefit, 5 pct CaF2 was the optimal choice. The purity of metal magnesium reached 95.59 wt pct, which has perfect crystallization and lamellar structure. CaF2 did not participate in magnesia Carbothermic Reduction in vacuum; instead, it played a catalytic role during the process.

  • Magnesium Technology 2012 - Mechanism of Carbothermic Reduction of Magnesia and Reversion Reaction
    Magnesium Technology 2012, 2012
    Co-Authors: Tian Yang, Bin Yang, Hongxiang Liu, Cheng-bo Yang, Yongnian Dai
    Abstract:

    In this study, the mechanism of the Carbothermic Reduction process to extract magnesium from magnesia and the reversion reaction in vacuum were investigated. The carbon monoxide (CO) content of the gas, phases of the condensing product, surface morphology of the Reduction slag and phase of the distillation product were measured by means of gas chromatography (GC), XRD, and SEM. The experimental results indicated that Mg was generated by magnesia and carbon at 1623K and 30~100Pa in the Carbothermic Reduction process.The main gas in Carbothermic Reduction process is carbon monoxide, no carbon dioxide occurred at any reaction time, the Reduction reaction is MgO(S)+C(S)=Mg(g)+CO(g) The gas-phase reversion will commence as soon as the saturated gas mixture is cooled. The reversion reactions are favored below 1373K.The distillation product by vacuum distillation process produced high purity metal magnesium product, it can be deduced in reversion reaction which occured at low temperature and 30~100Pa during Carbothermic Reduction. The reversion reaction was calculated, which gave the peak value у less than 9%.

  • Silica behavior in the alumina Carbothermic Reduction-chlorination process
    JOM, 2011
    Co-Authors: Fu-long Zhu, Yu Qingchun, Hai-bin Yuan, Bin Yang, Yongnian Dai
    Abstract:

    The behavior of silica was investigated experimentally in an alumina Carbothermic Reduction process and chlorination process in vacuum. The results showed that, first, SiC was produced by SiO2 and C, and then Al4SiC4 was produced by Al4C3, Al4O4C, C, and SiC during the alumina Carbothermic Reduction process at about 1,763 K. C, Al3C4 and Al4O4C decreased and Al4SiC4 increased as content of SiO2 increased. The following chlorination process was blocked, and the recovery rate of aluminum decreased quickly compared with that without silica. It was inferred that silica might be unfavorable for aluminum extracted from alumina by Carbothermic Reductionchlorination process in vacuum at about 1763 K.

  • behavior analysis of silica in aluminum production by alumina Carbothermic Reduction chlorination process in vacuum
    Vacuum, 2011
    Co-Authors: Fu-long Zhu, Hai-bin Yuan, Baomin Yang, Yongnian Dai
    Abstract:

    Abstract In present work, the behavior of silica was investigated experimentally in the alumina Carbothermic Reduction process and chlorination process in the temperature range of 1173 K–1763 K. The phase of slags, surface morphology and composition of condensate were examined by means of XRD, SEM and EDS. The results showed that SiC was produced by SiO 2 and C in the temperature range of 1573 K–1673 K, while alumina transformed into corundum completely, then Al 4 SiC 4 was produced by SiC and intermediates (Al 4 C 3 and Al 4 O 4 C) obtained during Carbothermic Reduction of alumina at about 1763 K. In the chlorination process, the silicon-containing materials in the condensate were not found. Because SiO 2 consumed Al 3 C 4 and Al 4 O 4 C, then the recovery rate of aluminum decreased. It was inferred that silica may be unfavourable for aluminum extracted from alumina by Carbothermic Reduction–chlorination process in vacuum.

Hamed Abedini Najafabadi - One of the best experts on this subject based on the ideXlab platform.

  • Solar Carbothermic Reduction of Dolomite: Direct Method for Production of Magnesium and Calcium
    Industrial & Engineering Chemistry Research, 2020
    Co-Authors: Hamed Abedini Najafabadi, Nesrin Ozalp, Michael Epstein, Richard A. Davis
    Abstract:

    Solar Carbothermic Reduction offers a promising approach for the clean production of several metals from their oxides with significantly lower CO2 emission compared to common pyrometallurgical proc...

  • Solar Carbothermic Reduction of Dolime as a Promising Option To Produce Magnesium and Calcium
    Industrial & Engineering Chemistry Research, 2019
    Co-Authors: Hamed Abedini Najafabadi, Nesrin Ozalp, Michael Epstein, Richard A. Davis
    Abstract:

    The use of solar energy to produce metals from their oxides via the Carbothermic Reduction process is a cleaner alternative to traditional combustion-based processes with an added value of a significantly reduced CO2 emission footprint. In this study, the potential contribution of solar energy to the pyrometallurgical production of magnesium was analyzed and compared to the common industrial process. The most energy-consuming step is the Carbothermic Reduction of the oxide. The Reduction was thermodynamically examined and experimentally investigated. While previous studies in the field were based mostly on using MgO, this work focused on dolomite (CaCO3·MgCO3) as the feedstock for the Carbothermic Reduction process. A thermogravimeter (TGA) was used to investigate the kinetics of the reaction under different conditions. The thermogravimetric results show that a full Reduction of MgO in dolime (calcined dolomite, MgO·CaO) is achievable around 1600 °C under atmospheric pressure. According to the results, at...