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首页> 外文期刊>Journal of Materials Research >W and two-dimensional WO_3/W nanocrystals produced by controlled self-sustaining reduction of sodium tungstate
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W and two-dimensional WO_3/W nanocrystals produced by controlled self-sustaining reduction of sodium tungstate

机译：钨酸钠的可控自持还原制备W和二维WO_3 / W纳米晶体

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摘要

The influence of calcium fluoride (CaF_2) on combustion characteristics of Na_2WO_4 + 3 Mg system and microstructure of the produced W and WO_3/W crystals is investigated. The results of thermodynamic analysis and experimental investigations show that CaF_2 simultaneously enhances the conversion of Na_2WO_4 toward tungsten and binds sodium through the formation of NaF phase. The examination of the microstructure of quenched combustion products and differential scanning calorimetry analysis indicate that at early stages of combustion, a part of Na_2WO_4 is reduced by Mg to tungsten, whereas another part reacts with CaF_2 forming CaWO_4 and NaF. Subsequent magnesium reduction of CaWO_4 significantly increases the overall temperature of the combustion process. Such modification in reaction mechanism coupled with postcombustion processing (e.g., acid/basic treatment) of the product allows us to produce either pure tungsten nanocrystals or tungsten oxide-tungsten nanostructures consisting of two-dimensional WO_3 nanoflakes assembled on a W core. It is found that CaF_2 does not influence the sizes of tungsten nanocrystals. However, since the addition of CaF_2 leads to the increase of overall reaction temperature, it facilitates the formation of W particles with equilibrium crystal shape by faceting process.
机译：研究了氟化钙（CaF_2）对Na_2WO_4 + 3 Mg体系燃烧特性以及所产生的W和WO_3 / W晶体的微观结构的影响。热力学分析和实验研究的结果表明，CaF_2同时促进Na_2WO_4向钨的转化并通过NaF相的形成与钠结合。对淬火燃烧产物的微观结构的检查和差示扫描量热分析表明，在燃烧的早期，Na_2WO_4的一部分被镁还原成钨，而另一部分与CaF_2反应形成CaWO_4和NaF。随后的CaWO_4镁还原会大大提高燃烧过程的整体温度。反应机理的这种修饰与产物的后燃烧处理（例如酸/碱处理）相结合，使我们能够生产纯钨纳米晶体或由组装在W核上的二维WO_3纳米薄片组成的氧化钨-钨纳米结构。发现CaF_2不影响钨纳米晶体的尺寸。但是，由于CaF_2的添加导致整体反应温度的升高，因此有助于通过刻面工艺形成具有平衡晶体形状的W粒子。

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  • 来源
    《Journal of Materials Research》 |2013年第18期|2611-2621|共11页
  • 作者

    Khachatur V. Manukyan; Albert A. Voskanyan; Sergei Rouvimov; Alexander S. Mukasyan; Suren L. Kharatyan;

  • 作者单位

    Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556;

    Laboratory of Kinetics of SHS Processes, Institute of Chemical Physics NAS of Armenia, Yerevan, 0014, Armenia;

    Notre Dame Integrated Imaging Facility (NDIIF), University of Notre Dame, Notre Dame, IN 46556;

    Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556 and Notre Dame Integrated Imaging Facility (NDIIF), University of Notre Dame, Notre Dame, IN 46556;

    Laboratory of Kinetics of SHS Processes, Institute of Chemical Physics NAS of Armenia, Yerevan, 0014, Armenia and Department of Inorganic Chemistry, Yerevan State University, Yerevan, 0025, Armenia;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);
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