Microtomy for

The majority of synthetic polymers can be thin sectioned by microtomy for transmitted light purposes [2]. For optimum results, sectioning should be carried out at a temperature just below the glass/rubber transition temperature, Tg. 

Ultramicrotomy is basically the same type of method as microtomy for preparing soft specimens for light microscopy. However, ultramicrotomy can be used to section a specimen to the 100 nm scale. It is commonly used to prepare polymeric or biological TEM specimens. 

The wood of Finus pinea was reported (8) as being almost intact . Microtomy for the SEM studies showed that the cell walls often bent over, making it diflScult to obtain a smooth surface. Weakening of the middle lamella was evident by the separation of individual tracheids or rows of tracheids from each other. TEM studies revealed delamination in the middle lamella-Si region, where the fibrils in Si were loosened. 

Plummer [120] provided an excellent review in his reflections on the use of microtomy for materials science specimen preparation, with a table of material classes, references, and comments. The review includes examples of polymer composites, blends, membranes, elastomers, and coatings. Kink bands and shear deformation were shown in polybenzobisoxazole (PBO) fibers microtomed and studied by TEM [121]. Fibers treated to cause compressive deformation were taped to sheet polycarbonate and coated with spray acrylic to fix them to the substrate. Small sections (<5mm) attached to the polycarbonate were cut, trimmed, and microtomed to a thickness of 40-80nm with a new area of a diamond knife and picked up on 400 mesh grids. Ericson and Lindberg [122] showed that when the sample holder of the... 

Evaluation of bulk industrial material is best done by microtomy for OM, TEM, and SPM and by fracture of bulk molded or extruded samples for SEM and FESEM for determining microstructure. A brief literature review with examples of microscopy characterization of copolymers follows, but this review is not intended to reflect the thousands of studies and references on this important topic. Transmission electron microscopy is by far the most widely used characterization tool for the assessment of copolymers, and it has been used for several decades to uncover and provide understanding of copolymer microstructure. 

The goal of our investigations was to characterise the morphology of the sample, and to determine the size and location of the PTFE and silicone oil phases by different methods [46,47], For phase characterization using Raman microscopy, no special sample preparation was necessary. For FTIR imaging, microtomed sections (5 pm in thickness) had to be prepared by cutting the sample with a diamond knife at — 80°C ("cryo-microtomy") to prevent smearing and to obtain flat surfaces. 

Specimens for AEM should be on the order of 20-100nm thick and should accurately represent the features which are to be analyzed. In general, these requirements are often difficult to achieve simultaneously, and various specimen preparation methods must be used to approach the ideal specimen. For catalyst specimens, three main specimen preparation methods can be used depending on the catalyst material, the form of the catalyst, and the information desired. These are grinding and dispersing, microtomy, and ion-beam thinning. 

The first step in microtomy is to embed the powder in one of a variety of media, which can be either an epoxy [21] or pure sulfur [52]. There is a range of epoxies suitable for microtomy of zeolites, but generally the requirements are that it be hard and that it infiltrate or adequately wet the zeolite powder before curing. Both LR white and Epon-type epoxies (if mixed properly) meet the hardness requirement The use of Epon enhances the wetting of siHcious or carbon-containing zeolites, but it contains low levels of chlorine which may cause overlaps in EDS and will make it impossible to analyze for Cl. Typically a small pinch of powder is blended with two drops of epoxy in the tip of an embedding capsule. Mixing can be done with a clean toothpick, combined if needed with a cycle or two of... 

Ultra-high molecular weight polyethylene (UHMWPE) has been used in orthopaedic prosthetic surgery for many years due to its excellent mechanical properties and frictional resistance. A large number of studies on both retrieved prostheses and raw material have, however, been necessary in order to understand and prevent degradation of the prostheses. The shape of the prostheses and the compression moulded blocks from which they are cut is usually not suitable for examination. In a number of studies microtomy has therefore been used in order to produce pieces suitable for further studies [112, 113, 114, 115, 116, 117, 118, 119, 120]. However, very often when microtomy is used, it is without any consideration of the fact that the process... 

The preparation, which is rapid if it concerns dispersing the crushed catalyst on an amorphous carbon film, may take several hours for microtomy. The analysis of a sample in transmission electron microscopy requires several hours of observation if the aim is to ensure that the results are representative. This is particularly important when subsequently seeking to determine particle size distribution histograms. Reliable values of the average size and of the width of the distribution can only be obtained taking into account a number of particles greater than 100. 

Microtomy refers to sectioning materials with a knife. It is a common technique in biological specimen preparation. It is also used to prepare soft materials such as polymers and soft metals. Tool steel, tungsten carbide, glass and diamond are used as knife materials. A similar technique, ultramicrotomy, is widely used for the preparation of biological and polymer specimens in transmission electron microscopy. This topic is discussed in Chapter 3. 

The aforementioned methods of specimen preparation, except microtomy, are regarded as an important part of metallography. These methods are also used for non-metallic materials... 

Sample Dehydration. Dehydration removes water and other liquids that remain in the sample after fixation. The sample is removed from the fixative and placed in a solvent that diffuses into the sample. The solvent must remove all sample fluids that are immiscible into the resin into which the sample is to be embedded so as to minimize the occurrence of gas or liquid pockets that make the sample unsuitable for microtomy and unstable under the electron beam. Typical dehydrating solvents are acetone, ethanol, dimethoxypropane, and water-soluble resins such as glycol methacrylate. 

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