Ultra-microtome

Fig. 14.14 Transmission electron microscopy images of ultra-microtomed halloysite G nanotubes before, longitudinal and, in the inset, perpendicular cross-section (A), and image afterCaC03 formation (B). Scanning electron microscopy images of halloysite G nanotubes before (C) and after (D) CaC03 formation.

Fig. 3 EPR inclusions in an impact-modified iPP, sectioned with an ultra-microtome, stained with Ru04 and observed in backscattered mode with a FEG-SEM the lighter regions in the particles are ethylene rich, whereas the darker peripheral regions are rich in EPR [24]...

Thin films of silicates have been produced by pressing powders in a diamond anvil cell (Hofmeister 1997), by cutting grain samples to submicron thick slices with an ultra-microtome (Bradley et al 1999), by electron-beam evaporation (Djouadi et al. 2005), and by laser deposition in a vacuum (Brucato et al. 2004). On one hand, powders produced in a laboratory are directly measured in transmittance when they are embedded in a matrix of transparent materials (e.g. KBr or polyethylene). On the other hand, reflectance measurements do not require the use of matrices powders of selected-size grains are directly measured with an appropriate optical accessory. Through measurements in both transmittance and reflectance, it is possible to evaluate the optical constants of a material. These are certainly the physical parameters... 

The interior of bulk samples can be revealed by fracture, freeze fracture, or (cryo-/ultra)microtoming. These techniques are well established in electron microscopy and require substantial training to ensure that the knives used do not introduce scratches and other artefacts. Unlike in SEM or TEM analysis, however, it is very well possible to analyze the trimmed specimen instead of the very thin sections removed (cryofacing). This loosens the constraint of ultrathin sections in many applications. Care has to be taken that the sample to be imaged is not significantly thicker or thinner than the calibration grating used for scanner calibration (see Sect. 2.2.5)... 

Optical and Electron Microscopy. Samples of film for optical and electron microscopy were prepared by microtoming. The samples for optical phase contrast microscopy were approximately 15-20jU thick whereas those for electron microscopy were ultra microtomed with a diamond knife to about 0.05-0. lju, thickness. A Leitz Ortholux microscope was used for the phase contrast microscopy and an RCA-EMU-36 electron microscope at 40,000 X magnification was used for the electron microscopy. 

Rayon (left) has a lobed cross section which is typical for fibers spun industrially by the viscose process. In contrast, Lyocell (middle) displays a round shape similar to the cellulose carbamate example (right). (In all the micrographs, the dark streaks are overlaps of sample material caused by the cutting movement of the ultra microtome knife.) Cross sectional shape and pore structure are strongly dependent on the precipitation conditions. For NMMO fibers [11] it was shown that harsh precipitation with water gave dense, round structures while softer precipitation into alcohols lead to a skin-core stmcture with dense skin and a porous inner region. StiU, cross sections are round in contrast to viscose-ty fibers. 

Morphologies were characterized by thin-section electron microscopy. Samples were first stained with osmium tetroxide (which reacts with residual double bonds) they were then embedded in an epoxy matrix, trimmed to a truncated pyramid shape, and microtomed using a Porter MT-2 ultra-microtome equipped with a diamond knife. Transmission electron micrographs were taken using a Phillips 300 electron microscope. 

A small rectangular block (10x5x3 mm) is excised from the specimen containing the feature of interest and immersed in molten sulfur at 125°C for 24 hours. At the end of this period, the speci-ment is obtained in the form of a hard ebonite-like solid suitable for ultrathin sectioning in the usual manner. In this study, the rubbers were sectioned in the usual manner with a Reichert OMU-2 ultra-microtome and subsequently examined using transmission electron microscopy. 

Figure 3.8 Overview of phase morphology development results for the PA/EP-MA blend system with 20 wt% EP-MA. In the hatched region the samples could not be analyzed using the cryo-ultra-microtome technique [53]...

An (ultra)microtome is a sensitive instrument for thin sectioning and is equipped with a knife made of glass or... 

Scanning electron microscopy (SEM) has been widely used to examine morphological features of polymer/CaCOs nanocomposites due to the simplicity of preparation of fractured surfaces compared to ultra-microtome sectioning required for preparation of TEM samples. While TEM provided unambiguous evidence for nanometer-scale dispersion of CaCOs particles, SEM is not particularly effective in this respect. It is mainly used in examining micron-scale agglomeration. 

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