Sample Preparation for SEM

The SEM (Scanning. Electron Microscopy) studies /40/ have been performed with a JEOL SM 84 OA microscope, using undoped samples. Sample preparation is illustrated by fig. 14. 

7 nm Au or approx. 15 nm C was then sputtered or evaporated, respectively, on the bulk film and the strip, or both methods were combined when necessary for highest resolution micrographs. 

Close to the surface, it appears that the fibrils have almost random directions and are smeared out and molten together, thus yielding a compact and dense surface layer with a rather homogeneous appearance (fig. 15). 

The trough in fig. 15 shows a layer of fibrilis within the bulk of the sample, which is apparently much more oriented than layers close to the surface, suggesting that alignment by elongation is much effective in interior layers of the film than on the surface, a result which is also supported by a comparison of anisotropic conductivity measurements and polarized optical reflectance experiments /23/ on Naarmann polyacetylene. 

From investigations performed using a stretching stage, we deduce three basic regimes during the process of elongation /23,40/. 

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Sample Preparation for SEM. Samples for the scanning electron microscopy (SEM Model Joel JXA-8600) were prepared by first immersing the membrane into a liquid nitrogen. This made the membrane brittle. The membrane was broken into small pieces and some of the pieces were mounted on the metal cylinder that forms part of the stage inside the microscope. The membrane was mounted such that its cross-section (or the broken face) was perpendicular to the electron beam. This way we were able to study the pore structure of the membrane directly. Our focus was to study the edge that was in contact with the bottom wall of the bottle. All membranes were coated with carbon to make them conductive prior to any microscopy work. 

Sample preparation for SEM analysis is trivial relative to TEM, with the sample simply deposited onto the top of an adhesive fastened to an aluminum stub/holder. Most often, conductive carbon tape is used to sequester the sample for FESEM,... 

The basic procedure of biological sample preparation for SEM involves in specimen fixation, dehydration, drying, and coating (see Ref 27 for a comprehensive review of procedures). The purpose of fixation is to immobilize the cellular components, such... 

Pathan AK, Bond J, Gaskin RE. Sample preparation for SEM of plant surfaces. Mater Today 1999 12 32 3. 

Figure 117. SEM micrographs of a cell cross-section for the cell 4 with composite LSNF-KjDC cathode after testing (a) and data of the EDX analysis in different spots near the cathode electrolyte interface (b) CC - current collector, C - cathode, E - electrolyte. Note that the current collector was peeled off during the sample preparation for SEM smdy.

This technique can be applied to samples prepared for study by scanning electron microscopy (SEM). When subject to impact by electrons, atoms emit characteristic X-ray line spectra, which are almost completely independent of the physical or chemical state of the specimen (Reed, 1973). To analyse samples, they are prepared as required for SEM, that is they are mounted on an appropriate holder, sputter coated to provide an electrically conductive surface, generally using gold, and then examined under high vacuum. The electron beam is focussed to impinge upon a selected spot on the surface of the specimen and the resulting X-ray spectrum is analysed. 

Sample preparation for more specialized work can require more intensive procedures and accessories [49]. Stages have been made for the SEM to accommodate a variety of experiments [50]. Heating, cooling, and mechanical manipulation would be useful for most pharmaceutical materials, but other... 

The morphology of mesoporous structures can be investigated by TEM, as shown in Fig. 7.2 b and d. However, sample preparation for TEM is time-consuming. Fortunately the mesoporous regime can also be studied by today s most advanced SEMs. For SEM inspection no sample preparation is required, and even sputtering of the sample is dispensable, as shown by the SEM micrographs displayed in this and the next section. 

Even though TEM and SEM played major roles in the study of IPN morphological features, there are various shortcomings, such as staining artifacts, difficulties in sample preparation for very rubbery materials, and the two-dimensional viewing limit for the former. Recently, various scattering techniques have been applied to measure the phase dimensions of IPN s via statistical treatment. The principles of neutron scattering theory as applied to the phase separated materials have been described in a number of papers and review articles [33-36]. 

The morphology of the BT powders was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A small amount of the BT powders were pressed on a carbon tape, which attached to the brass sample stub for SEM. To prepare TEM samples, a tiny amount of the BT particles was dispersed in isopropanol by grinding in an agate mortar before placing it on a copper grid. 

Specimen Preparation for SEM. In pharmaceutical technology, most of the samples that are examined by an SEM are powders. After the sampling procedure,... 

Sample preparation for EM depends on the nature of the food and the type of scanning or transmission technique used. For SEM, dry foods are prepared in the same way as powders. Solid foods based on proteins (cheese, meat) are fixed in glutaraldehyde solutions (1-3%, buffered near the pH value of the food),... 

Particle analysis of environmental samples by secondary ion mass spectrometry (SIMS, see Sect. 63.5.6.3) or scanning electron microscopy in combination with X-ray spectrometry (SEM-XRS, see Sect. 63.5.6.4). The SEM-XRS instrument and its sample-preparation area are located in the clean laboratory, but the SIMS instrument is not. Sample preparation for SIMS can be carried out in the CL, but a small dedicated clean-room at US Class-lOO/ISO-Class 5 cleanliness level is colocated with the instrument to avoid potential cross contamination when transporting the prepared sample planchets to the instrument. The SEM-XRS method is also supported in the CL by an array of optical microscopes equipped with micromanipulation systems for picking up particles of interest prior to further treatment such as chemical analysis and isotopic measurement by TIMS or ICP-MS. 

Sample preparation for purposes of examination in the SEM is very simple. In order to avoid disruptive charges, electrically nonconductive ceramic materials must be coated with a film of gold, carbon, or platinum about 20 nm thick by a sputtering process. Etched and unetched sections, fracture surfaces, glazes, firing skins, powder compacts, and prefired and finished sintered products can then be examined directly in the scanning electron microscope. 

Although not a true surface technique, SEM-EDS often provides useful information in regard to surface corrosion mechanism. The ubiquitous nature, low cost, and ease of use of this technique cause it to be used as a tool in many failure analyses involving corrosion. Because its analysis depth is much larger (approximately a micrometer) than the true surface techniques, it is not necesseiry to analyze samples that are high-vacuum compatible. This results in the necessity of almost no sample preparation for many different kinds of samples. 

The SEM was used to demonstrate and confirm these theoretical projections [306,309]. In the early study [306], molten drops of PE and PMMA were allowed to spread and solidify on a paper substrate prior to standard preparation for SEM. Later, poly(phenyl ether) (PPE) vacuum pump oil (Santovac 5-Monsanto Chemicals), which is not volatile, was used for dynamic studies. The PPE was fed through a hole in the sample stub, from outside the specimen chamber, and the wetting experiment was video tape recorded [309]. Mori et al. [310] used freshly cleaved mica surfaces as steps 60 nm in height inhibit wetting. Surface roughness has a major effect on the local contact angle between the liquid and the substrate of interest. 

SEM requires little sample preparation for metallic and inorganic materials as the information required concerns only the surface structure and the material composition of the layer proximate to the surface. Small samples of up to several millimetres and sometimes even larger can be investigated directly in the SEM if the sample material has a sufficiently high electric conductivity to prevent charging produced by electron bombardment. However,... 

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