Vacuum Methods in Electron Microscopy. By Wilbur C. Bigelow

Microstructural evolution in two in situ reinforced composite systems, one produced by partial reduction and the other by grain growth, has been examined over a range of size scales using light microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Metal-ceramic matrix composites were formed by the partial reduction of Al₂O₃–Cr₂O₃ solid solutions to form Cr metal particles in an Al₂O₃–Cr₂O₃ matrix which had a lower Cr₂O₃ concentration. In a second system, grain growth of Si₃N₄ during liquid phase sintering produced large, whisker-like grains in a fine-grained Si₃N₄ matrix, bonded by an oxynitride phase. The mechanisms controlling microstructural evolution in these two systems were examined.     

Transmission Electron Microscopy of Boundary-Lubricated Bearing Surfaces. Part I: Mineral Oil Lubricant

Transmission electron microscopy (TEM) was performed on the near-surface material (depth <500 nm) of tapered roller bearing inner rings (cones) that were tested at two levels of boundary-lubricated conditions in mineral oil with no additives. Site-specific thinning of cross section cone surface sections for TEM analyses was conducted using the focused ion beam (FIB) milling technique. High-resolution structural and compositional characterization of near-surface material and surface layers was performed on an untested cone as well as cones tested at Λ～1.1 and 0.3. This approach revealed near-surface microstructural distortion and grain size gradients that were attributed to surface finishing operations during manufacture. The characteristics of oxide surface layers and micro-cracks on the tested bearing surfaces were evaluated and found to depend on lubrication conditions.     

Ultrastructure of Tracheal Surface Liquid: Low-Temperature Scanning Electron Microscopy

A layer of liquid lines the airways in the lung. Previous microscopic studies have suggested that it is in two phases, with a mucous gel lying above a periciliary sol. However, shrinkage artifacts due to chemical fixation, dehydration, and drying have prevented reliable estimates of the depth of these layers. To avoid such problems, we have studied the surface liquid of bovine trachea by low-temperature scanning electron microscopy (LTSEM). A polished copper probe cooled to liquid nitrogen temperature was applied to the mucosal surface of sheets of excised tracheal epithelium to effect rapid freezing of surface liquid. Tissue sheets were then mounted in an LTSEM (AMRay 1000A with Biochamber) which maintains samples at -180°C with a Joule-Thompson refrigerator built into the stage. Tissues were fractured at right angles to the epithelial surface, coated with gold, and viewed, all at 10^?5 to 10^?6 torr without transfer through air. The sample was stable under the electron beam at accelerating voltages up to 20 kV. Epithelial features (nuclei, cilia, microvilli, mucous granules) were well preserved. The mucosal surface of the cells was covered with material on the order of 8 μm in depth. The mucous gel and periciliary sol could be seen as distinct layers and could be distinguished by the size and pattern of ice crystal voids generated by radiant-etching of the fractured surface of the sample.     

Correlation Studies of WS 2 Fullerene-Like Nanoparticles Enhanced Tribofilms: A Scanning Electron Microscopy Analysis

The beneficiary effects of tungsten disulphide (WS₂) inorganic fullerene-like nanoparticles (IFLNPs) in the lubrication industry were shown in recent years. However, their successful incorporation into lubricants (oils, greases) is not straightforward. In practice, the lubricant contains several components for different purposes, e.g. reducing the oxidization of the oil (antioxidant), minimizing the wear rate (anti-wear additive), dispersants, etc. These additives can contain chemically active compounds, which under the lubrication process (where locally extreme conditions can develop: high pressure and flash temperatures) can change the chemistry in the contact zone and block the beneficial effects of the inorganic nanoparticles. In this investigation, poly-alpha-olefin (PAO) is being used as base oil in which the WS₂ nanoparticles and different additives are mixed. A ball-on-disc sliding test revealed that certain additives inhibit the nanoparticles to reduce friction (less than 5 % decrease in friction coefficient), while in other cases, the friction reduction was above 50 %. The comparison is being made between PAO + additive and PAO + additive + IFLNPs. Scanning electron microscope and energy dispersive X-ray spectroscopy were used to investigate the elemental composition of the tribofilms formed on the wear marks. Further analysis was made in order to reveal correlations between elemental compositions of the tribofilms and external parameters such as the friction coefficient and wear rate. For instance, a strong correlation between tungsten content of the tribofilm and the friction coefficient was found.     

Advances in Optical and Electron Microscopy. Vol. 3. Edited by R. Barer and V. E. Cosslett

The production of vacuolated mitochondria and myelin figures can be markedly reduced with aldehyde perfusion fixation by perfusing a concentrated aldehyde solution before the conventional perfusate. A method is presented for accomplishing this with no practical time delay. Factors causing myelin figures and damaged mitochondria are discussed. Gum acacia helps prevent ‘washed-out’ cells and processes, and seems to aid myelin preservation. A clear solution is necessary for a good perfusion. Techniques for accomplishing this are presented. A concentrated formaldehyde solution perfused as a small volume immediately prior to the conventional perfusate causes alterations of the endoplasmic reticulum, including the subsurface cisterns, and an increase in numbers of spine apparatuses. Evidence is presented by using tubes of gelatin containing Schiff's reagent that formaldehyde is the fastest penetrating aldehyde but that it only fixes about half the distance it penetrates. Acrolein penetrates more rapidly than glutaraldehyde but fixes only as far as formaldehyde. Glutaraldehyde fixes as far as it penetrates.     

扫描电镜低电压显微的实现

介绍了扫描电镜低电压显微的优点和限制及为实现低电压显微而对扫描电镜的改进。