Crystal Growth and Phase Transformation Kinetics in Nanocrystalline Materials

本研究将探索纳米尺寸的晶体（纳米晶体）如何生长，以及后续反应的速率和机制如何受到颗粒尺寸的影响。纳米晶材料是化学风化和微生物生物矿化作用的产物，在风化的岩石、土壤和沉积物中占了大部分的活性表面积。纳米晶体的稳定性和反应性的改性对材料科学也具有重要意义。最近关于纳米晶材料粗化的实验工作表明，在某些条件下，颗粒通过晶体取向附着生长。这种很大程度上未被认识的机制涉及通过直接消除表面来减少表面能。研究将检验定向附着在自然界中粗化的重要性，并将量化这种机制对反应动力学的影响。实验工作将继续使用方便和重要的TiO2体系，表征研究将主要涉及高分辨率透射电子显微镜和x射线衍射。这项工作的成果将是对纳米晶尺寸领域动力学的新认识。

9814333BanfieldThis research will explore how crystals of nanometer dimensions (nanocrystals) grow, and how rates and mechanisms of subsequent reactions are affected by particle size. Nanocrystalline materials are products of chemical weathering and microbial biomineralization and account for much of the reactive surface area in weathered rocks, soils, and sediments. The modified stability and reactivity of nanocrystals is also of significance to materials science. Recent experimental work on coarsening of nanocrystalline materials has revealed that under a subset of conditions, particles grow by crystallographically oriented attachment. This largely unrecognized mechanism involves reduction in surface energy by direct elimination of surfaces. Research will examine the importance of coarsening by oriented attachment in nature and will quantify the effects of this mechanism on reaction kinetics. Experimental work will continue to use the convenient and important TiO2 system and characterization studies will primarily involve high-resolution transmission electron microscopy and X-ray diffraction. The product of this work will be new understanding of kinetics in the nanocrystalline size domain.