Porous tablets of crystalline calcium carbonate via sintering of amorphous nanoparticles

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2013
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Liu, Xing-Min
Aziz, Baroz
Hedin, Niklas
Zhao, Zhe
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Porous tablets of crystalline calcium carbonate were formed upon sintering of a precursor powder of amorphous calcium carbonate (ACC) under compressive stress (20 MPa) at relatively low temperatures (120–400 °C), induced by pulsed direct currents. Infrared spectroscopy ascertained the amorphous nature of the precursor powders. At temperatures of 120–350 °C and rates of temperature increase of 20–100 °C min−1, the nanoparticles of ACC transformed into crystallites of mainly aragonite, which is generally difficult to achieve using wet-chemicals under kinetic control. The amorphous precursor particles (10 nm) transformed into crystallites (30–50 nm) during sintering. Consistently, the specific surface areas of 140–160 m2 g−1 for the precursor particles were reduced to 10–20 m2 g−1 for the porous tablets. The porous network within the tablets consisted of fused aragonite and vaterite particles in a ratio of 80:20. The fraction of aragonite to vaterite was invariant to the temperature and rate of temperature change used. The particle size increased only to a small amount on an increased rate of temperature change. At temperatures above 400 °C, porous tablets of calcite formed. The later transformation was under thermodynamic control, and led to a minor reduction of the specific surface area. The size of the crystallites remained small and the transformation to calcite appeared to be a solid-state transformation. Porous, template- and binder-free tablets of calcium carbonate could find applications in for example, biology or water treatment.

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ISO 690GEBAUER, Denis, Xing-Min LIU, Baroz AZIZ, Niklas HEDIN, Zhe ZHAO, 2013. Porous tablets of crystalline calcium carbonate via sintering of amorphous nanoparticles. In: CrystEngComm. 2013, 15(6), pp. 1257-1263. ISSN 1466-8033. eISSN 1466-8033. Available under: doi: 10.1039/C2CE26604K
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@article{Gebauer2013Porou-21236,
  year={2013},
  doi={10.1039/C2CE26604K},
  title={Porous tablets of crystalline calcium carbonate via sintering of amorphous nanoparticles},
  number={6},
  volume={15},
  issn={1466-8033},
  journal={CrystEngComm},
  pages={1257--1263},
  author={Gebauer, Denis and Liu, Xing-Min and Aziz, Baroz and Hedin, Niklas and Zhao, Zhe}
}
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