Nanoscale tomographic reconstructions from objects with diameters of 100nm or smaller can only be achieved non-destructively with transmission electron tomography. The application of this technique to W tips, which are common probes for scanning tunneling microscopy and nanoindentation, is demonstrated with emphasis on visualizing oxide layers and functionally attached nanoparticles. For the reconstruction of facetted free-standing catalyst nanoparticles, such as CeO2 octahedra, we propose a combination of energy-filtered (EF) and bright field (BF) TEM tomography to achieve high fidelity of the projection relationship via EFTEM, due to its incoherent imaging mode, and high resolution definition of the particle circumference from the edge-enhancement effects of the BF tomogram. Finally, electron tomography applications to CeO2 nanoprecipitates embedded in a multicomponent oxide glass matrix are shown, which comprises the first tomographic 3D reconstruction of a nanoscale dendrite.

The combined effect of strain and temperature on the microstructure and detailed internal structure of dislocation boundaries was systematically studied in compressed pure polycrystalline copper and nickel and compared to the microstructure of compressed polycrystalline aluminum. Below 0.5Tm the microstructure of Cu and Ni consists of dislocation cells, however, only in Cu second generation microbands are formed. In Cu and Ni, the dislocations inside the boundaries rearrange themselves from tangles to ordered arrays of parallel dislocations following interplay between strain (requirement for cross slip) and temperature (dislocation mobility and ease of cross slip). The ordered detailed structure is similar to that observed in Al deformed at room temperature and lower strain levels. The amount of strain and temperature applied to Cu and Ni in order to achieve the same detailed structure formed in Al depends on the stacking fault energy (SFE) of the metal- higher strain and temperature as the SFE is lower.

The annular dark field (ADF) image contrast of a 0.92% tensile strained GaN0.045As0.955 layer on GaAs substrate was studied with a scanning transmission electron microscope (STEM) as a function of ADF detector inner semi-angles ranging from 28 mrad to 90 mrad. The GaN0.045As0.955 layers were brighter than the surrounding GaAs for the values of ADF detector semiangle up to 65 mrad, and the measured contrast decreased with increasing ADF detector inner semi-angle. For a 37 nm thick specimen, the GaN0.045As0.955 intensity is about 13% higher than that of GaAs in the 28 mrad ADF detector inner semi-angle. Multislice simulations show that the displacement around substitutional N atoms plays an important role in the observed ADF-STEM contrast, while the contribution to the contrast due to misfit strain between GaN0.045As0.955 and GaAs is small.

The structure of Au-Pd bimetallic nanoparticles prepared by sonochemical technique was investigated by an analytical transmission electron microscopy. The core (Au)-shell (Pd) structure was clearly confirmed by the intensity profile of annular dark field scanning transmission electron microscopy (ADF-STEM). The line-scan analysis of energy dispersive X-ray spectroscopy (EDS) in STEM mode also revealed the Au core-Pd shell structure. The selected area electron diffraction pattern from the Au-Pd nanoparticles indicated the possibility that the crystal lattice of Pd shell is expanded and coincident with the crystal lattice of Au core.

Silicon carbide (SiC) fibers made by chemical vapor deposition (CVD) are of interest for organic, ceramic, and metal matrix composite materials due their high strength, high elastic modulus, and retention of mechanical properties at elevated processing and operating temperatures. The properties of SCS-6™ silicon carbide fibers, which are made by a commercial process and consist largely of stoichiometric SiC, were compared with an experimental carbon-rich CVD SiC fiber, to which excess carbon was added during the CVD process. The concentration, homogeneity, and distribution of carbon were measured using energy dispersive x-ray spectroscopy (SEM/EDS). The effect of excess carbon on the tensile strength, elastic modulus, and the crystallographic and microstructural properties of CVD silicon carbide fibers was investigated using tensile testing, x-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM).

Nanoparticles are of interest in many applications since their decreased size may give them properties that are very different from bulk material. Often nanoparticle properties such as size (diameter) and size distribution are evaluated using transmission electron microscopy (TEM). These parameters, size and size distribution, can be more easily obtained from digitized TEM images by mapping particle signal to black and background pixel to white in a process known as thresholding then performing an algorithm known as a particle analysis. The goal of this study was to compare the ability of several popular thresholding algorithms to segment TEM images. Performance of the thresholding algorithms was evaluated through qualitative and quantitative measures. Results show that the choice of a thresholding algorithm will strongly affect the results obtained from particle analysis.

Volume change of cereal materials caused by moisture migration is studied by Environmental Scanning Electron Microscopy (ESEM) using videomicroscopy and stereoscopy in combination with image processing. It is shown that the in situ volume change can be monitored by following the change of projection area, assuming isotropic volume change. Also the volume change measured by stereoscopy matches well with the measurement of the projection area change by videomicroscopy (after normalization). It is concluded that volume changes more in a higher relative humidity (RH) region with more active kinetic behavior. The exact volume change in between two relative humidities can be obtained by interpolating the equilibrium volumes. All the sorption/desorption curves can be well described by the ‘parallel exponential kinetics’ model (PEK model), which described two independent, parallel processes.

Although the inelastic mean free path for Si and Ge have been measured previously, reported experimental values for silicon range from 121 nm to 160 nm for 200 keV and a large collection angle. A key factor responsible for this uncertainty is the lack of an accurate measurement of the specimen thickness at the point at which the EELS spectra are obtained. In this research, we have evaluated a systematic methodology for determination of the specimen thickness. In the thickness measurement based on converging beam electron diffraction, CBED, instead of the classic “trial and error” straight-line-fitting method to either the maxima or minima, a non-linear least square fitting of the theoretical diffraction profile to the energy filtered two-beam CBED is used. The low-loss EELS spectrum is also obtained from the same location. The inelastic mean free path was determined using the measured thickness and EELS data. Furthermore, attempt is also made to obtain the dielectric function from the low-loss spectrum. The established method will be extended to other materials and the results will be compared with numerical simulations.