Investigation of the structure and assembly of inorganic macromolecules formed on the terrestrial surface

在地球表面有许多有趣的天然物质，它们是在水丰富和氧化的条件下形成的，温度适中。这些材料通常是非常细的颗粒，没有三维周期性，不像普通的晶体矿物。从这些特性来看，它们可称为“无机大分子”。然而，由于其颗粒尺寸非常小且结构非周期性，其原子结构和织构尚未得到很好的了解。伊莫长石、蒙脱石和某些层状硅酸盐具有严重的堆积无序性。这项工作的目的是开发新的方法和/或技术来研究这些材料，并阐明它们在地球上的结构和形成条件。首先，我们试图从电子衍射图的强度分布来确定天然纳米管伊莫戈柳石的原子结构。然而，没有一个合理的模型可以完全解释电子衍射。这项调查必须作为未来的研究继续进行。与此同时，AIST的Suzuki在实验室中寻找有效合成伊莫戈柳石的条件方面取得了进展。蒙脱石是一种非常细粒的层状硅酸盐，通常被认为是“纳米片”。它的基本结构是2:1层，中间有两个四面体薄片和一个八面体薄片，但细节尚不清楚。特别讨论了八面体比例在2:1层中的分布。我们研究了用高分辨率电子显微镜（HRTEM）测定阳离子分布的可能性。然而，在图像记录过程中发现，强电子束使2:1层脱氢，这种脱氢导致阳离子迁移。我们需要找到一个办法来解决这个问题。另一方面，我们在一种云母，celadonite的热脱羟基相中发现了一种新的2:1层结构。通过HRTEM和粉末x射线衍射图的模拟，我们在阐明各种层状硅酸盐的堆积无序性质方面取得了很大的进展。所研究的层状硅酸盐包括高岭土族矿物、叶蜡石、滑石、数石等。特别是直接观察高岭土群矿物的堆积无序性，是半个多世纪前开始的这一课题史上划时代的工作。此外，还开发并展示了几种利用菊池图案表征细晶材料结构（堆叠顺序、晶体取向、形貌等）的新技术和新思路。少

There are a number of interesting natural materials on the terrestrial surface, formed in water-abundant and oxidizing conditions at moderate temperatures. These materials are generally very fine-grained and do not have three-dimensional periodicity, unlike common crystalline minerals. From these characteristics, they may be called "inorganic macro-molecules". However, their atomic structures and textures are not well understood, owing to the very small particle size and non-periodic structure. Imogolite, smectite and some phyllosilicates with heavy stacking disorder are typical examples. The purpose of this work was to develop new methodologies and/or techniques to investigate these materials, and elucidate their structures and forming conditions on the earth.At first, we tried to determine the atomic structure of imogolite, a natural nano-tube, from the intensity distribution in electron diffraction patterns. However, a plausible model that completely explains the electron diffractio … More n patterns was not obtained. This investigation must be continued as a future research. Meanwhile, Suzuki in AIST has made a progress in finding conditions to synthesize imogolite efficiently in a laboratory.Smectite is a very fine-grained phyllosilicate, often regarded as "nanosheet". Its basic structure is a 2:1 layer with two tetrahedral sheets and one octahedral sheet between them, but the detail is not clear yet. Especially distribution of octahedral rations in the 2:1 layer is under discussion. We investigated possibility to determine the cation distribution by using high-resolution electron microscopy (HRTEM). However, it was found that intense electron beam during image recording dehydroxylates the 2:1 layer and this dehydroxylation induces cation migration. We need to find an idea to overcome this problem in future. On the other hand, we have found a novel 2:1 layer structure in the thermally dehydroxylated phase of a kind of mica, celadonite.We have made a plenty of progress to elucidate the nature of stacking disorder in various phyllosilicates in this study, by using HRTEM and simulation of powder X-ray diffraction patterns. The investigated phyllosilicates include kaolin group minerals, pyrophyllite, talc, sudoite, etc. Especially direct observation of the stacking disorder in kaolin group minerals was an epoch-making work in the history of this topic started more than a half century ago.Besides, several new techniques and ideas to characterize the structure (stacking sequence, crystal orientation, morphology, etc.) of fine-grained materials using Kikuchi patterns were developed and demonstrated. Less