Cryo-sectioning and chemical-fixing ultramicrotomy techniques for imaging rubber latex particle morphology

Two methods adapted from biological microscopy are described for a new application in imaging the morphology of rubbery latex particles. In the first method, a drop of latex is frozen in liquid nitrogen, sectioned with a diamond knife and vapour-stained with osmium tetroxide, then viewed by transmission electron microscopy. When applied to latexes made by emulsion polymerization of methyl methacrylate in a natural rubber latex seed, inclusions are clearly visible. A chemical fixation method is then described for imaging the morphology of such rubbery latex particles. Glutaraldehyde is added to the latex, followed by osmium tetroxide. The sample is then dehydrated in ethanol, epoxy resin added, and the sample cured, ultramicrotomed, and imaged with transmission electron microscopy. An inclusion morphology is again clearly seen.     

Comparative study of a block copolymer morphology by transmission electron microscopy and scanning force microscopy

Using transmission electron microscopy (TEM) and scanning force microscopy (SFM) together, it was possible to verify important structural features of a nanostructured bulk material such as the kp‐morphology in an ABC triblock copolymer. By applying suitable imaging techniques during the SFM measurements it was possible to determine the morphology without additional manipulation steps in between. In comparison, TEM investigations on this type of material usually require selective staining procedures prior to the measurement. Also electron beam damage is often encountered during TEM measurements especially if components such as poly(methacrylates) are present. In contrast, SFM measurements can be assumed not to significantly change the phase dimensions of the components.     

土壤及沉积物样品预处理的新技术-微波萃取法

微波萃取是试样预处理的一种新技术,这是对传统萃取方法的突破,是符合环境可持续发展的绿色技术,本文对其原理、特点、仪器及操作条件,特别是近十年来在土壤及沉积物样品预处理中的应用及进展进行评述。     

Comparing electron tomography and HRTEM slicing methods as tools to measure the thickness of nanoparticles

Nanoparticles’ morphology is a key parameter in the understanding of their thermodynamical, optical, magnetic and catalytic properties. In general, nanoparticles, observed in transmission electron microscopy (TEM), are viewed in projection so that the determination of their thickness (along the projection direction) with respect to their projected lateral size is highly questionable. To date, the widely used methods to measure nanoparticles thickness in a transmission electron microscope are to use cross-section images or focal series in high-resolution transmission electron microscopy imaging (HRTEM “slicing”). In this paper, we compare the focal series method with the electron tomography method to show that both techniques yield similar particle thickness in a range of size from 1 to 5 nm, but the electron tomography method provides better statistics since more particles can be analyzed at one time. For this purpose, we have compared, on the same samples, the nanoparticles thickness measurements obtained from focal series with the ones determined from cross-section profiles of tomograms (tomogram slicing) perpendicular to the plane of the substrate supporting the nanoparticles. The methodology is finally applied to the comparison of CoPt nanoparticles annealed ex situ at two different temperatures to illustrate the accuracy of the techniques in detecting small particle thickness changes.     

Models and observations of fcc/bcc interfaces

Whereas models of the structure and periodicity of CSL or near CSL high angle grain boundaries are relatively well developed and have been to some extent verified by experiment, the nature of more general (e.g. fcc/bcc) interfaces is very imperfectly understood. One of the major differences between homo- and heterophase boundaries is the occurrence, in the latter case, of reproducible orientation relationships due to the crystallographic requirements of phase transformation (e.g. a glissile interface for martensitic growth, low energy interfaces for classical nucleation). A review is given of the relationships commonly observed to obtain between fcc and bcc crystals (as well as ordered phases based upon these structures). Within a given relationship, it is possible to use models of the available interfaces to predict their dislocation content; the success of the various approaches is considered. It is shown that the dislocation arrays identified on fcc/bcc boundaries are consistent with the occurrence of a primary structural relaxation, but that the latter does not appear to be complete. Possible reasons for this are discussed, together with the extent to which secondary structural models may be applicable. Attempts to rationalize the observed orientation relationships and morphologies are discussed, and it is pointed out that these all rely on searches for situations of minimum primary misfit, but that the way in which the latter is quantified determines the results of the analyses. Nevertheless, the implication is that the primary misfit does appear to determine the actual behaviour, though no structural or mechanistic conclusions can safely be drawn from this observation.     

A modified goodman's technique for obtaining rocking-beam type patterns

A new method was developed for convergent beam electron diffraction (CBED) and large angle convergent beam electron diffraction (LACBED) in the JEM-100CXII. This method is obtained in the imaging mode using the defocus objective lens and by re-setting condenser-2. A multi-dark field CBED pattern was achieved in two ways.     

Large-area plan-view sample preparation for gaas-based systems grown by molecular beam epitaxy

We describe a method for plan-view transmission electron microscopy (TEM) sample preparation that takes advantage of extreme etch-rate selectivity in GaAs and AlAs in HF/H₂O solutions. GaAs/In_xGa_1-xAs/GaAs strained-layer films (x = 0.05, 0.10, 0.19, 0.22) were chemically lifted off using this technique and were mounted on Cu TEM grids such that TEM transparent areas of up to 1 × 2 mm of constant thickness (196.4 nm) could be viewed. This simple, large-area plan-view technique uses only chemical methods and significantly extends the usefulness of TEM for the evaluation of crystal quality in GaAs-based epitaxial systems. The method requires the growth of a release layer of AlAs (10 nm thick) prior to the layered structure of interest.     

The role of Poisson's binomial distribution in the analysis of TEM images

Frank's observation that a TEM bright-field image acquired under non-stationary conditions can be modeled by the time integral of the standard TEM image model [J. Frank, Nachweis von objektbewegungen im lichtoptis- chen diffraktogramm von elektronenmikroskopischen auf- nahmen, Optik 30 (2) (1969) 171–180.] is re-derived here using counting statistics based on Poisson's binomial distribution. The approach yields a statistical image model that is suitable for image analysis and simulation.     

ICP-MS测定水系沉积物和土壤中的W、Mo等金属元素

采用不同的微波消解程序和不同混合酸消解水系沉积物和土壤标准参考物,用ICP-MS测定6种金属元素(Li、Be、Mo、W、Tl和U)的含量。依据分析结果,比较了消解程序、混合酸组成和用量对样品的消解效果。结果表明,由1 mL HNO₃＋3 mL HF＋0.5 mL H₂SO₄组成的混合酸对水系沉积物和土壤具有很好的消解能力,各元素的测定值与推荐值相符。     

Application of nanoparticle tracking analysis platform for the measurement of soot-in-oil agglomerates from automotive engines

Nanoparticle Tracking Analysis (NTA) has been applied to characterising soot agglomerates of particles and compared with Transmission Electron Microscoscopy (TEM). Soot nanoparticles were extracted from used oil drawn from the sump of a light duty automotive diesel engine. The samples were prepared for analysis by diluting with heptane. Individual tracking of soot agglomerates allows for size distribution analysis. The size of soot was compared with length measurements of projected two-dimensional TEM images of agglomerates. Both the techniques show that soot-in-oil exists as agglomerates with average size of 120 nm. NTA is able to measure particles in polydisperse solutions and reports the size and volume distribution of soot-in-oil aggregates; it has the advantages of being fast and relatively low cost if compared with TEM.     

纳米材料的透射电镜表征

用金属包埋技术可以从纳米材料中切取纳米尺度的薄膜，用透射电镜或高分辨电镜研究纳米材料的微观形貌和微观结构。     

A variation of transmission electron microscope sample preparation for VLSI analysis

Sample preparation for VLSI analysis is often slow due to long ion milling time and because the location of the thin area of the sample is difficult to control. By modifying the standard techniques used with a VCR Group (and perhaps other) mechanical dimpler, the ion milling time can be reduced to less than 30 min. and the location on the thinned area reasonably controlled. These modifications involve the use of a radiused edge on the dimpling tool, a rubber O-ring on the polishing tool, and not rotating the sample platen during polishing. The modifications to the dimpling and polishing tools allow more control of the geometry of the dimple, while not rotating the sample platen allows a thinner sample to be produced and permits the use of the sample translation micrometers to shift the location of the thinned area during polishing. The quality of samples produced using this modified procedure is equivalent to that obtained with the more standard methods.     

Dislocation mobility and electronic effects in semiconductor compounds

In situ transmission electron microscopy experiments provide a unique way to investigate in real time the dislocation behaviour at a microscopic scale and to decide which elementary process controls the dislocation glide in semiconductors. In this review the experimental results obtained on different semiconductors are presented and discussed. Particular attention is devoted to the radiation-enhanced glide process.