Thick section preparation materials

To facilitate the measurement of the bulk conductivity, the toner powders were compressed into thin cylindrical disks under a hydrostatic pressure of 100,000 psi. Under these pressures the toner flowed readily and formed a uniform pellet in which the toner particle surfaces were in more intimate contact than in a loose powder. Gold electrodes were evaporated onto the flat faces and the current as a function of the applied electric field measured. This measurement method of the conductivity has certain inherent disadvantages, however, this measurement was intended to be used simply to contrast the kinetic conductivity values reported in Section IV, not to extract absolute values of the material parameters. Nonetheless, several samples of various thicknesses were prepared and measured for each type of toner and the results were found to be quite reproducible. 

Figure 3. Electron microscopic techniques used to study micromechanical processes in polymers (a) investigation of fracture surfaces by SEM (b) investigation by TEM of ultrathin sections prepared from deformed and selectively stained bulk material and (c) deformation of samples of different thicknesses (bulk, semithin, and ultrathin)9 using special tensile stages with SEM, HVEM, and TEM. The technique in (c) shows the possibility of conducting in situ deformation tests in the electron microscope.

Thermal conductivity measurements by TMDSC [9] involve two experiments on the same sample material, where only the sample thickness varies. Preparing a sample of uniform and known geometry is essential for accurate thermal conductivity measurements by this method. The sample is again in direct contact with the sample holder, so this method is also reserved for experienced users. Selecting a thin sample, the experimental conditions are chosen so that the heat capacity of the sample can be measured by the methods outlined earlier (Section 5.6). The second experiment is performed on a thick sample in such a way that controlled temperature modulation occurs only in that part of the sample in contact with the sample holder. The remainder of the thick sample functions as a heat sink. 

During the Pooling and ejection parts of the injection moulding cycle, the material in the barrel is continulusly homogenised and prepared for flowing into thick section... 

Generally, microtomy refers to the preparation of thin slices of material by sectioning for observation in an optical microscope by transmitted light. Microtomed sections are cut with steel or glass knives to about 1 to 40/tm thickness. Ultramicrotomy methods involve the preparation of ultrathin sections of material for observation in an electron microscope. Ultramicrotome sections are cut with glass or diamond knives to a thickness ca. 30-100 nm. If imaging is to be done via many techniques, the TEM preparation method can be utilized to prepare thin sections for OM, TEM, and AFM, and the flat block face is used for SEM and/or SPM. 

Sample preparation is often the most time-consuming aspect of transmission electron microscopy. It is relatively straightforward if the sample is a homogeneous metal or alloy and if a thin foil can be produced from any part of it. Problems arise if areas near to the surface or to a boundary between two dissimilar materials are required to be analyzed. Normally a thin section of material 1 mm in diameter is produced mechanically, which is then polished to the minimum practical thickness before being finally thinned to electron transparency. The final stage is carried out using either electrolytic or ion-thinning methods. When... 

Biopsy material for schistosomiasis is better examined in teased preparations than in sections, as the entire thickness can be examined at once, and the viability of eggs can be determined by observation of the movement of the larvae within the eggs. 

Preparation of biological material for electron microscopy still required fixation, dehydration, and ultrathin sections. Araldite and other resins were used in place of paraffin wax for blocking. At first, specially sharpened steel knives were employed to cut the sections, but from 1950 glass or diamond knives were used which could cut slices 100-200 nm thick. By 1952, Palade and others were obtaining sections... 

The plasma membrane of bacterial cells, other than the wall-less mycoplasmas and some archaebacteria, is surrounded by a multilayered wall which may be separated from the membrane by a thin periplasm (or periplasmic space). This can be seen most clearly in suitably prepared thin sections of cells of E. coli or other gram-negative bacteria as a relatively empty space of 11- to 25-nm thickness (Fig. 8-28).579 581 The volume of this space (which may be filled with gelled material) depends upon the osmotic pressure of the medium. In E. coli it contains 20-40% of the total... 

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