Specimen preparation method microscopy

Miller, M.K., Russell, K.F., Thompson, K., Alvis, R., Larson, D.J. (2007) Review of atom probe FIB-based specimen preparation methods. Microscopy and Microanalysis, 13,428-436. 

The specimen preparation methods used for microscopy of polymers involves the use of many toxic chemicals as well as the use of instruments which can be radiation hazards. It is well beyond the scope of this text to provide the information required for the proper and safe handling of such chemicals and instruments and the researcher is... 

The increased use of optical and electron microscopy applied to polymer research has been the result of widespread acceptance of the techniques and extended property requirements of the polymer materials. It is known that the structures present in a polymer reflect the process variables, and further that they greatly influence the physical and mechanical properties. Thus, the properties of polymer materials are influenced by their chemical composition, process history and the resulting morphology. Morphological study involves two aspects prior to the study itself selection of instrumental techniques and development of specimen preparation methods. Structural observations must be correlated with the properties of the material in order to develop an understanding of the material. 

What then are the key specimen preparation methods for studying polymer materials by microscopy techniques This topic could be organized in one of two ways, that is by each specific microscopy technique or by each preparation method. The approach that has been chosen is to describe each specimen preparation type for all microscopies in order to minimize overlap and also to make it simpler to use for reference. Those preparation methods chosen for discussion are the typical ones found to be of major utility in the industrial laboratory. They cover the full range of study of the industrial scientist, that is everything from rapid failure analysis to process optimization studies and fundamental research. The fundamental studies must often be fitted into a limited time framework that requires good choices of methods and techniques on a wide range of materials. 

Reviews of specimen preparation methods for fiber microscopy and instrumental techniques applied to fibers were published during the early 1970s [14-16]. This section contains applications of microscopy to the understanding of fiber microstructures used in the industrial laboratory for modification of fiber formation processes to... 

Applications showing the range of microscopy techniques and specimen preparation methods used on commercial impact polymers will be described. Changes in polymer morphology are expected upon addition of an elastomer for instance, such addition is expected to cause a decrease in the spherulite size as the elastomer domains can act as nucleating sites [274]. This has been observed for many polymers including... 

Once the objective of the experiment is known and the specimens selected for study, the next major step is the selection of the microscopy techniques and the specimen preparation methods required to image the polymer structures of interest (Table 7.2). If lamellar crystals must be... 

The major objective of this text is to provide information on the basic microscopy techniques and specimen preparation methods applicable to polymers. This book will attempt to provide enough detail so that the methods described can be applied, and will also reference appropriate publications for the investigator interested in more detail. Some discussion will consider polymer structure and properties, but only as this is needed to put the microscopy into context. 

Just as important as the proper use of the microscope is the specimen preparation. When using transmitted-light microscopy, it is necessary to prepare thin samples, about 5-50 pm thick. This is also true even for transparent polymers because of the small depth of field of an optical microscope. If information is required about an inner part of the material, the only course of action is to cut a thin section with a microtome. Melt-pressed films can be prepared by melting the polymer and squeezing it between two glass slides to make it thin. Many of the generally known specimen preparation methods are applicable to polymers. A recent overview of all methods as a useful tool for polymers is given in [Ij. 

Different specimen types yield a range of results upon ion or plasma etching. Multiphase polymers generally etch differentially, enhancing the contrast. Melt crystallized polymers can be etched to reveal the spherulites. Surface protuberances and particulate fillers can and do form cones or ridges when etched. Oriented semicrystalline polymers, on the other hand, appear to be the most controversial with respect to the resulting surface textures. Clearly, in such cases the specimen should be prepared by other methods for comparison, and control experiments are essential. There are problems in the industrial laboratory that can be solved, in part, by microscopy of surfaces prepared by etching techniques however, these are far fewer than those addressed by other specimen preparation methods. 

Microscopy techniques can be used to evaluate the size and distribution of particles added to polymer fibers, such as metals that modify the physical, mechanical, or electrical properties. In general, ultrathin sections are examined in either STEM or TEM modes to reveal the particles within the polymer. Energy (EDS) and wavelength dispersive x-ray spectroscopy (WDS) methods are used to map for various elements in order to establish the relation between the particle morphology and chemical composition. A specimen preparation method for x-ray analysis in the SEM is to use a trimmed block face, which remains after cutting thin sections, or to study a thick section. An example of such a study is described below. 

Once the objective of the experiment is known and the specimens selected for study, the next major step is the selection of the microscopy techniques and the specimen preparation methods required to image the polymer structures of interest (Table 6.2). If lamellar crystals must be evaluated, for instance, there is no point in considering most optical techniques as they will only provide an overview of these structures. Comparisons are made in this section regarding the various techniques, in both the text and tables, as an aid in this selection process. Observations of... 

A major consideration in the selection of preparation methods for microscopy study is the nature of the potential artifacts formed, although time, cost and the capital equipment required are also important factors. In a busy laboratory time considerations are very important, especially if time consuming methods also have potential artifacts. The accessory equipment available must also be considered, although for this discussion it will be assumed that the laboratory has the equipment required for most general preparations. A complete discussion of specimen preparation methods can be found in Chapter 4. Typical preparations for microscopy will be outlined here with emphasis on the nature of potential artifacts. 

The most important issues in the solution of structural problems are image interpretation and development of structure-property relations. Imaging techniques and preparative methods must be chosen that provide images of the needed structures by the most efficient experiments. Several major principles have been emphasized for imaging of structures. First, the problem solving protocol (Table 6.1) should be considered prior to developing an experimental plan. As part of this protocol the important properties of the material to be studied should be determined and the overall objective of the study developed. The size of the polymer structures required should be determined (Tables 6.2 and 6.3) as an aid to the selection of the appropriate microscopy techniques. Specimen preparation methods should be selected after considering the nature of the specimen itself, the types of structures to be determined and the potential artifacts. If a specimen can be examined directly, that is preferred over a less direct specimen preparation method, especially... 

Reviews of specimen preparation methods for fiber microscopy and instrumental tech-... 

It is well known that the particle shape, size, and distribution of a latex or emulsion control the properties and end-use applications. Many types of latex are manufactured with a controlled and sometimes monodisperse distribution of particle sizes. These polymer liquids are wet and sticky, making specimen preparation for microscopy very difficult. Because particle size and shape are so important to properties, the preparation must focus on not changing the particles as found in the fluid state. Preparation includes simple methods (see Section 4.1) such as dropping a solution onto a specimen holder, staining/fixation (see Section 4.4), microtomy (see Section 4.3), and special cryo methods (see Section 4.9). All microscopy techniques can be used for these studies. This section is meant to provide a brief survey of the types of microscopy applications that have been found useful in the evaluation of emulsions, latexes, and their use as coatings and adhesives. 

Define the microscopy technique(s) and best specimen preparation methods for imaging and microanalysis... 

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