Northwestern University, 2220 Campus Dr., Evanston, IL, 60208, USA.
Adv Mater. 2017 Jul;29(26). doi: 10.1002/adma.201606730. Epub 2017 Apr 28.
Energy-efficient synthesis of materials locked in compositional and structural states far from equilibrium remains a challenging goal, yet biomineralizing organisms routinely assemble such materials with sophisticated designs and advanced functional properties, often using amorphous precursors. However, incorporation of organics limits the useful temperature range of these materials. Herein, the bioinspired synthesis of a highly supersaturated calcite (Ca Ba CO ) called balcite is reported, at mild conditions and using an amorphous calcium-barium carbonate (ACBC) (Ca Ba CO ·1.2H O) precursor. Balcite not only contains 50 times more barium than the solubility limit in calcite but also displays the rotational disorder on carbonate sites that is typical for high-temperature calcite. It is significantly harder (30%) and less stiff than calcite, and retains these properties after heating to elevated temperatures. Analysis of balcite local order suggests that it may require the formation of the ACBC precursor and could therefore be an example of nonclassical nucleation. These findings demonstrate that amorphous precursor pathways are powerfully enabling and provide unprecedented access to materials far from equilibrium, including high-temperature modifications by room-temperature synthesis.
在远离平衡的组成和结构状态下实现节能型材料合成仍然是一个具有挑战性的目标，但生物矿化生物通常使用无定形前体来组装具有复杂设计和先进功能特性的此类材料。然而，有机物的掺入限制了这些材料的有用温度范围。本文报道了在温和条件下使用无定形的钙-钡碳酸盐（ACBC）（CaBaCO3·1.2H2O）前体制备一种称为文石的高度过饱和方解石（CaBaCO3）。文石不仅含有比方解石溶解度极限多 50 倍的钡，而且还显示出高温方解石的典型碳酸根位置的旋转无序。它比方解石硬 30%，刚性小 30%，并且在加热到高温后仍保留这些特性。对方解石局部有序的分析表明，它可能需要形成 ACBC 前体，因此可能是一种非经典成核的例子。这些发现表明无定形前体途径具有强大的启发性，并为远离平衡的材料提供了前所未有的途径，包括通过室温合成获得高温变体。
