科研之友
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摘要
In this article, we have demonstrated top-down solid-phase transformation from calcium oxalate dehydrate (COD) tetragonal prisms into highly macroscaled mesoporous calcium carbonate tetragonal prisms. Also, being a promising C2O42- source, L-ascorbic acid (AA) was first applied to obtain high-quality COD tetragonal prisms. The high crystal quality of COD is critical for the successful fabrication of porous CaCO3 microcrystals with predetermined morphology and well-controlled internal structure. Calcined at different heating rates, porous CaCO3 with different pore sizes was obtained. This novel, simple thermal transformation strategy is convenient for preparing nanoporous materials at a large scale, and it is also useful to further extend to convert salt carbonate into such porous nanostructures. The as-obtained porous CaCO3 tetragonal prisms are nontoxic, cheap and environmentally friendly, and the application of such porous CaCO3 with different pore sizes as support matrices successfully mitigates the common problems for phase-change materials (PCMs) of inorganic salts, such as phase separation phenomena and super-cooling effect. Our experiments clearly reveal that the confinement effect of the porous structure plays a more dominant role in mitigation of the phase separation while the mesoporous CaCO3 microcrystals with the smaller mesopore sizes used PCMs as supporters. However, heterogeneous nucleation will be responsible for the mitigation of the phase separation in the macroporous CaCO3 support matrix, while in this case, size confinement effect is negligible. Thereby, the designed porous nanostructures can bring significant improvements to the heat-storage performance in future "smart house'' wall materials.
- 出版日期2010
- 单位中国科学技术大学
