Electron microscopy and X-ray microanalysis : key research tools in applied science
Creators: name: Jablonski, Wis
Publisher: name: University Of Tasmania
Year: 2023

description: The diversity of the science of electron microscopy (EM) is difficult to compare with any other instrument-supported science. Not only the multitude of methods but also the variety of electron beam instruments preclude a clear definition of the boundary of electron microscopy fields of application and most likely it will touch and influence other branches of science which are at first glance, unrelated to the subject. This thesis is devoted to developments in electron microscopy and X-ray microanalysis and their utilisation as key research tools in applied science. The work presented here has been performed on various electron beam instruments such as transmission electron microscopes (TEM), scanning electron microscopes (SEM), scanning electron microscopes with X-ray microanalytical attachments and dedicated electron probe microanalysers (EPMA). The respective methods and techniques which have been developed to satisfy the requirements of the general scientific community are also presented. This dissertation demonstrates the need for electron microscopy and outlines the advantages of using new, customer-induced methods within the campus of research institutions and beyond. Bearing in mind the multidisciplinary aspects of electron microscopy, the development and application of methods and techniques as presented in the following chapters cover a vast area of interest. It can be said that practically almost all branches of science may benefit from these in one way or another. Developments presented here are divided into the results obtained within the existing instrument configurations and the results procured after some modifications and extensions of the existing EM instrument capabilities. A new approach to the preparative techniques used to compensate for a lack of more sophisticated and expensive associated equipment spells out possibilities of achieving the same results with a minimum of financial outlay and maximum scientific gain. Some specimen modifications that were achieved by an ion etching method show how to obtain more information from a specimen which may be obscured by undesirable and difficult to remove outer layers of biological or foreign origin. In the field of X-ray microanalysis, suitability of standards is assessed by calculating a mean atomic number of standards in relation to microanalysed material. The same approach is used quantitatively to estimate a backscattered electron coefficient and an atomic number contrast in the phases of mineralogical samples. Experimental problems with trace element analysis and interferences from major elements are discussed and example of such a case is presented. The recipes are given for quantitative analysis of light elements such as oxygen, carbon and carbon-based synthetic materials (polymers). In the course of quantitative analysis of oxygen it is demonstrated that in mineralogy, stoichiometry may no longer be an ironclad guarantee. In some instances new standards, specially for quantitative work on specimens of organic origin are created, their usefulness is assessed and thoroughly examined for homogeneity. Also, it becomes evident that the well described and easily available polymers can be used as reliable standards in the light elements analysis. For the first time low magnification phenomena in EPMA have been investigated and quantified with the full benefit determined for a minimum of specimen damage and electron optics contamination. Some application programs have been written and their merits in the field of microanalysis explained and presented in full in Appendices. It is postulated that peak performance of an electron beam instrument depends on many factors, some of which, e.g. contamination may be practically beyond control of the operator. Further, some means of minimising the problems are provided. It is also shown that a very recent introduction of an environmental SEM (ESEM) is making a substantial impact on the conventional ways of specimen preparation and observation and is providing a new insight into X-ray microanalysis and related phenomena at elevated pressures (low vacuum) in a specimen chamber. The educational and aesthetic aspects of electron microscopy are considered and the ways of efficient dissemination of electron microscopy science are presented with special regard to computer-based and related technologies. Finally, certain procedures for successful assessment of a new electron beam instrument and its purchase, based on the ESEM acquisition process are recommended.