TEM method

In the present paper non-conventional TEM methods to characterize small metallic particles are presented. The topographic information on the particles shape can be combined with micro-diffraction (using STEM) data to obtain a full characterization of the particle. The case of gold particles evaporated on a NaCl substrate is used as example. The particle shapes observed are discussed. It is shown that many particles have a crystal structure which is different from the bulk (Fee). 

The invention of the electron microscope in the 1930s by Knoll and Ruska cleared the way for scientists to take an even closer look at vesicles and other colloidal structures [5]. Improving the resolution of the optical microscope roughly by the factor that the optical microscope improved that of the unaided eye, the finer structures of colloidal systems became visible. With the electron microscope, single bilayers can be made visible and the distance between lamellae can be determined. Thus, the structure of a given system can be determined to up to 1/10000000 of a millimeter, which is about the distance of six atoms in a molecule. The most impressive results are obtained with the freeze fracture and cryo-TEM methods [6]. 

CS planes using conventional TEM methods (e.g. Merritt and Hyde 1973) and by calculations using lattice potential models (Catlow et al 1978, Cormack et al... 

Another characteristic of the TEM method is that individual particles are examined. Its disadvantage is that the images recorded may not be typical. On the other hand, it is easy to identify new phases in a multiphasic specimen. 

Abstract. Nanopowders of nonstoichiometric tungsten oxides were synthesized by method of electric explosion of conductors (EEC). Their electronic and atomic structures were explored by XPS and TEM methods. It was determined that mean size of nanoparticles is d=10-35 nm, their composition corresponds to protonated nonstoichiometric hydrous tungsten oxide W02.9i (OH)o.o9, there is crystalline hydrate phase on the nanoparticles surface. After anneal a content of OH-groups on the surface of nonstoichiometric samples is higher than on the stoichiometric ones. High sensitivity of the hydrogen sensor based on WO2.9r(OH)0.09 at 293 K can be connected with forming of proton conductivity mechanism. 

Application of either PCM or TEM methods to the determination of asbestos fibers in biological or environmental media (air or water) requires that the fibers be separated from interfering material and collected on appropriate supports. Methods for preparing biological and environmental samples for microscopy are described below. 

For the analysis of asbestos fibers in air, a sample of air is drawn through a filter by a vacuum pump (usually at a flow-rate of around 1-2 L/minute), and the fibers retained on the filters are examined microscopically. The sensitivity of the methods depends on the volume of air drawn through the filter and the microscopic method employed. In the workplace, where PCM is the standard method, the theoretical detection limit for a short-term sample (15 minutes) is around 0.04 PCM f/mL, but may be reduced to 0.001 f/mL using an 8-hour sample (NIOSH 1976). In practice, such low detection limits are not readily achievable, and measured values below 0.1 PCM 17mL should not usually be considered reliable (ASTM 1988). Sensitivity of TEM methods for ambient or indoor air are usually around 0.1-1 ng/m. ... 

The structure of CdSe nanoparticles segregated to the fluid interface as shown by confocal microscopy (Fig. 4a) has been investigated ex situ with scanning force microscopy (SFM) and transmission electron microscopy (TEM) methods. All results point to a monolayer of nanoparticles with liquidlike ordering at the interface (Fig. 4b,c) [46],... 

Obviously, the joint application of XRD and TEM methods is highly recommended it may provide mineralogically well established petrogenetic information on low-grade changes in phyllosilicates. Examples of such comprehensive studies were available in the literature in the late 1980s, with many more appearing more recently (Eberl et al. 1987,... 

Preparation of samples for the observation under TEM is more tedious and exacting than that used for SEM. The specimens have to be hardened and stained with Br, OsO, or RuO, microtomed into ca. 20 slices, mounted on a grid and polymeric film support and measured. Frequently, the SEM and TEM methods are being used in parallel. In all cases microscopy is considered but one method of characterization of polymer blends [Karger-Kocsis and JGss, 1987 Kyotani and Kanetsuna, 1987 Hsu andGeil, 1987]. 

By STM, most limitations of the TEM method may be overcome. This holds, in particular, for the electrochemical STM (EC-STM) technique that allows a real-time in situ study of electrodissolution processes at a lateral resolution at the nanometer scale or better, with the substrate and the tip controlled potentiostatically or gal-vanostatically during imaging (see Chapter 3.1 in Volume 3). Moreover, atomic height steps and topographic changes in the subnanometer range can be resolved [138). On the other hand, chemical information is... 

As with the TEM methods in Subheading 3.1, the time periods for each step are sufficient for most samples of individual cells or cell layers with associated Gram-negative or non-spore-forming Gram-positive bacteria. For bulk samples such as biopsied tissues or bacterial colonies on solid medium, incubation periods should be adjusted to ensure thorough diffusion of reagents into the samples. 

Defects of other types at scales quite different from that of the unit cell can also be important. The surfaee stmeture represents both the crystal face during growth and the first structure presented to adsorbing molecules, so that surface study, for example by AFM and HRTEM, can give important clues to these processes. Furthermore, the structure of mesopores generated by post-synthetic treatment, or the size and dispersion of metal particles in bifunctional catalysts are both examples of non-periodic features important in catalysis, so that recently developed 3D TEM methods to study them have particular significance. 

The textural features of the constitution of nanoporous ACs, synthesized as a result of pyrolysis of cellulose, were studied by the TEM method (Kaneko et al. 1992), with the method being applied to carbons differing in the temperature of their heat treatment in the argon atmosphere over... 

From the tribotests without external cooling we chose samples, which were clearly affected as evidenced by a smooth tribological track surrounded by areas with clear evidence for roughening (Fig.2). To elucidate the process we took samples with the aid of a FIB and analysed the obtained siices with TEM methods. 

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