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首页> 外文期刊>Crystal growth & design >Direct Observation of Microparticle Porosity Changes in Solid-State Vaterite to Calcite Transformation by Coherent X-ray Diffraction Imaging
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Direct Observation of Microparticle Porosity Changes in Solid-State Vaterite to Calcite Transformation by Coherent X-ray Diffraction Imaging

机译：通过相干X射线衍射成像直接观察固态Vaterite中固态Vaterite的微粒孔隙率变化

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摘要

The simplest route to synthesize porous calcium carbonate in large quantity is to mix concentrated aqueous solutions containing Ca2+ and CO32- ions. The formed vaterite microspheres have a porous structure, but are not thermodynamically stable. Heating above 350 degrees C induces a solid-state transformation of vaterite into the most stable phase, calcite, while maintaining an unusual spheroidal morphology. Here, by using three-dimensional coherent X-ray diffraction imaging, the morphological evolution associated with the thermally induced phase transition is studied. We observe that despite an overall similar pore volume, the pore geometry differs markedly before and after annealing. Before annealing, the microspheres display elongated and nanometer sized pores, while after annealing they exhibit large and open pores. During transition, the specific surface area decreases from 7 m(2)/g for vaterite to 3 m(2)/g for calcite. The general trend resulting from 3D observations is that the solid state phase transition is not only governed by the decrease of the Gibbs bulk free energy change (Delta G(bulk) approximate to -3 kJ/mol) but is largely influenced by the surface energy change (Delta G(surf) approximate to -0.1 kJ/mol per m(2)/g lost). The porous calcite microspheres produced by this facile two-step process may have potential use as low-density filler in paint, paper, pharmaceutical, and plastic industries.
机译：以大量合成多孔碳酸钙的最简单的途径是混合含Ca 2+和CO 32的浓缩水溶液。形成的Vaterite微球具有多孔结构，但不具有热力学稳定。在350℃以上加热诱导Vaterite的固态转化进入最稳定的相位方解石，同时保持不寻常的球形形态。这里，通过使用三维相干X射线衍射成像，研究了与热诱导相转变相关的形态学进化。我们观察到，尽管整体上具有相似的孔体积，但在退火之前和之后，孔几何形状明显不同。在退火之前，微球显示细长和纳米尺寸的孔，同时退火后它们表现出大而打开的孔隙。在过渡期间，比表面积从7米（2）/ g的转化物降低至3米（2）/ g进行方解石。 3D观察结果导致的一般趋势是固态相转变不仅通过降低Gibbs散装能量变化（Delta G（散装）近似到-3kJ / mol）而且受到表面能的影响更改（Delta G（Surf）近似于-0.1 kj / mol / m（2）/ g损失）。通过该容易的两步工艺产生的多孔辅导微球可能在涂料，纸张，制药和塑料工业中具有低密度填料的潜在用途。

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  • 来源
    《Crystal growth & design》 |2017年第8期|共6页
  • 作者

    Cherkas O.; Beuvier T.; Breiby Dag W.; Chushkin Y.; Zontone F.; Gibaud A.;

  • 作者单位

    LUNAM Fac Sci IMMM UMR CNRS 6283 F-72085 Le Mans 09 France;

    LUNAM Fac Sci IMMM UMR CNRS 6283 F-72085 Le Mans 09 France;

    Norwegian Univ Sci &

    Technol NTNU Dept Phys Hgsk Ringen 5 N-7491 Trondheim Norway;

    ESRF European Synchrotron 71 Ave Martyrs F-38043 Grenoble 09 France;

    ESRF European Synchrotron 71 Ave Martyrs F-38043 Grenoble 09 France;

    LUNAM Fac Sci IMMM UMR CNRS 6283 F-72085 Le Mans 09 France;

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  • 正文语种 eng
  • 中图分类 晶体学;
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