RUI: in situ investigations of clay mineral swelling using atomic force microscopy

粘土矿物？具有片状结构的硅酸盐矿物是土壤和沉积物的主要成分。这些矿物的独特性质之一是它们通过在层之间掺入不同量的水和可交换阳离子而膨胀的能力。 粘土矿物的膨胀在环境中营养物和污染物的运输、废物遏制技术和钻孔稳定性中起着重要作用。 迄今为止，在实验室中研究膨胀的常用技术只能测量许多粘土层的层间距的平均变化，因此它们所能提供的信息有限。 本研究将利用原子力显微镜（AFM）研究粘土在水环境中的原位膨胀。 AFM用于产生材料表面的三维图像，与传统的光学显微镜不同，它可以？看到没？比人类头发丝的宽度小一百万倍。随着周围溶液的化学组成发生变化，可以监测粘土层（准晶体）的单独隔离堆叠内的溶胀变化。由于原子力显微镜可以精确测量不同准晶之间以及给定准晶内部的层间距，因此可以研究天然矿物的内在非均匀性。 此外，在一段时间内的一系列的AFM图像的采集将提供一个详细的图片的动态过程中涉及的阳离子交换的层间区域和方法，直接测量溶胀率的变化。 这些研究将为控制膨胀的化学和物理性质以及影响各种化学物质与粘土矿物相互作用的参数提供新的见解。巴克内尔大学化学系的学生研究人员。这些学生将共同撰写所产生的出版物，并将密切参与所有阶段的手稿准备和在国家会议上介绍结果。获得AFM的实践经验将是该项目学生的重要教育机会。随着纳米技术和纳米科学越来越成为化学研究的中心，学生接触这些学科至关重要。原子力显微镜能够在接近原子尺度的尺度上成像和操纵物质，是这场革命的核心。

Clay minerals ? silicate minerals with sheet-like structures - are major components of soils and sediments. One of the unique properties of these minerals is their ability to swell by incorporating varying amounts of water and exchangeable cations between the layers. The swelling of clay minerals plays a major role in the transport of nutrients and pollutants in the environment, waste containment technologies, and borehole stability. To date, commonly used techniques for studying swelling in the laboratory have only been able to measure the average change in layer separation of many clay layers and consequently are limited in the information they can provide. The study proposed here will use atomic force microscopy (AFM) to investigate clay swelling in situ in an aqueous environment. AFM is used to produce three dimensional images of the surface of a material, and unlike a conventional optical microscope, it can ?see? features up to a million times smaller than the width of a human hair. Changes in swelling within individual isolated stacks of clay layers (quasi-crystals) that accompany modifications to the chemical composition of the surrounding solution can be monitored as they occur. Because the interlayer spacing both between different quasi-crystals and within a given quasi-crystal can be precisely measured with AFM, the inherent heterogeneities of natural minerals can be investigated. Additionally, the acquisition of a series of AFM images over a period of time will provide a detailed picture of the dynamic processes involved in the exchange of cations within the interlayer region and a method to directly measure the rates of swelling change. These studies will offer new insight into the chemical and physical properties that control swelling and the parameters that affect the interactions of various chemical species with clay minerals.The work proposed here will be conducted solely in collaboration with undergraduate and M.S. student researchers of the Chemistry Department at Bucknell University. These students will be co-authors on the resulting publications and will be intimately involved in all stages of manuscript preparation and presentation of results at national conferences. Gaining hands-on experience with AFM will be a significant educational opportunity for the students on the project. As nanotechnology and nanoscience become increasingly central to chemical research, it is critical that students are exposed to these subjects. AFM, with its abilities to image and manipulate matter at dimensions approaching the atomic scale, is at the core of this revolution.