Raster Electron Microscopy Research Articles

Oxidative conversion of n-heptane over molecular sieves

n-Heptane was partially oxidized at 523 K to 2-, 3- and 4-heptanones and heterocyclic compounds in the presence of SAPO-5, SAPO-11, BEA and MCM-41 under air flow at different molar ratios of n-heptane/oxygen. The catalysts were characterized by X-ray diffraction (XRD), raster electron microscopy and energy dispersion analysis of X-ray (EDAX). The presence of acid and basic sites was proven by interaction with alcohols — cyclohexanol and benzyl alcohol. 2-Methyl-5-ethyl-furan and 2,6-dimethyl-pyran were the main heterocyclic products. The oxidation of n-heptane to the corresponding hydroperoxides is suggested. The cleavage of the hydroperoxides is activated on the acid active sites of the molecular sieves used as catalysts. 1-Hepten-4-ol, 4-methyl-1,4-hexadiene and 2,4-dimethyl-1,3-pentadiene were also obtained as products.

Peculiar effect of chloride ions on the anodic dissolution of iron in solutions of various acidity

Anodic behavior of iron in chloride solutions is studied in the pH range from 0 to 6 and at the concentration of chloride ions from 0.2 to 3 mol/l. Electrochemical measurements were supplemented with the raster electron microscopy studies, of electrode surfaces. The observed independence of the limiting dissolution current of pH is explained by a hypothesis that water does not participate in the anodic process at sufficiently large anodic overpotentials. Depending on the concentration of chloride ions, the continuity of the logi a-pH dependence is first interrupted and the, restored; the reaction order in hydroxide ions changes from a positive value to zero. This is probably caused by the “dynamic passivation” of iron with the adsorbed oxygen atoms and their competitive replacement by chloride ions.

DETERMINATION OF THE WAX LAYER ULTRASTRUCTURE OF JONAGOLD WITH CONFOCAL AND RASTER ELECTRON MICROSCOPY

Until now, techniques for measuring wax layer thickness and analysing wax layer ultrastructure were always destructive and could alter the original structure of the wax. In this research confocal microscopy and raster electron microscopy were evaluated and compared to conventional scanning electron microscopy. Both new techniques have the advantage that minimal sample preparation is needed compared to conventional SEM. From the images obtained by means of confocal microscopy, no semicrystalline, flaked structure as described in literature could be observed. In contrary, a porous structure with little irregular channels was observed. At the outer surface, cracks could be observed which corresponded to the boundary edges of the epidermal cells beneath the cuticula. This was confirmed by REM. On several confocal microscopy images small droplets were observed at the surface of the wax layer. The exact origine, formation and composition of these droplets was not yet revealed. They were very unstable for they disappeared more or less when more severe techniques as SEM or REM were applied. The thickness of the wax layer could also be determined from the images, and was found to be typically between 10 to 60 mu m.

Copolymers of poly-{acrylamide-co-[3- (acryloylamino)propyltrimethylammoniumchloride]} as carriers for platinum species and their use as catalysts in heterogeneous gas phase reactions

In the following, the binding of PtCl62− to quarternary ammonium groups of the copolymers followed by reduction of platinum to a zerovalent state is described. At temperatures between 60 and 180°C the supported catalysts were effective in isomerization and hydrogenation of hexene(1). The dependence of catalytic activity and selectivity on copolymer composition and the average molecular weight (Mw) of the polymer have been analyzed. Copolymers of the composition 90% acrylamide/10% quarternary compound and average molecular weights of about one million were found to be the most active ones. Thermal and chemical stability of the catalysts were studied by differential thermal analyses, thermal gravimetric analyses, and elemental analyses. Morphology and structure were analyzed by raster electron microscopy, x-ray photon spectroscopy, far infrared spectroscopy, and Fourier transform infrared spectroscopy. Several particle properties of the new catalysts, such as pore volume and surface area, were also investigated. © 1996 John Wiley & Sons, Inc.

Investigation of the different discharge mechanisms in pseudospark discharges

The intention of this paper is to give an overview of recent experiments explaining the development and transition of the discharge phases in a pseudospark. The reported experiments include single gap pseudospark discharges in ultra-high-vacuum systems with hydrogen as working gas, as well as multigap pseudospark discharges in argon. Temporally and spatially resolved framing photography, spectrometry, raster electron microscopy and time resolved electrical measurements are presented. The experiments comprise a current range of some hundreds of amps to 60 kA. The results are used to specify the four characteristic phases of the pseudospark: Townsend-, hollow cathode-, high current- and metal vapor arc phase. >

Calibration of REM with elimination of systematic linear-gauge error

A method of calibrating a raster electron microscope with the aid of linear gauges in the form of rectangular slit-like grooves that eliminates the unaccounted for systematic error of the usual linear gauges is examined. It is demonstrated that in the dimensions of slit-like structures in silicon created at the IOF RAN, systematic error (greater than 2 nm) is absent.

Integrated optical proton exchanged TM-pass polarizers in LiNbO/sub 3/: modelling and experimental performance

Integrated optical TM-pass polarizers operating at wavelengths around /spl lambda/=1.5 /spl mu/m have been realized by introducing proton exchanged regions adjacent to a Ti-indiffused waveguide on X-cut, Y-propagating lithium niobate. Structural investigations of the proton exchanged regions have been carried out by raster electron microscope and optical methods, in order to characterize the index profile created by the proton exchange. Several polarizers with different geometries of the proton exchanged regions have been analysed numerically by employing the beam propagation method (BPM) and the finite element method (FEM). The device performance is shown to depend strongly on the geometrical shape of the outer boundaries of the proton exchanged regions and on their distance to the channel waveguide. Experimental results are given for several samples with different gaps between the optical waveguide and the proton exchanged regions as well as for different annealing times. For a proper device design a TE-extinction of -26 dB and a TM-excess loss of only 1.2 dB have been obtained experimentally. >

Influence of ? radiation on the structure-sensitive properties of CuTi amorphous alloy

The influence of small doses of γ radiation on the structure-sensitive properties of CuTi amorphous metallic alloy (AMA) is investigated. The AMA exhibit brittle behavior. It is found that, in samples exposed to γ radiation, the nonlinear behavior of the load-elongation curve is more pronounced and begins sooner. A small change in the fracture morphology in these samples is observed by raster electron microscopy. The additional broadening of the first amorphous maximum and its shift on the x-ray diffraction patterns correlates with increase in the γ dose. The modification of the structural-relaxation processes on heating the initial and irradiated samples is traced by the acoustic-emission method. The activation energy of these processes is determined.

High-precision method of measuring linear dimensions in a raster electron microscope

A new method of precision measurement of dimensions in a raster electron microscope based on the concept of “invariant points” is proposed. Testing of the method has shown that it is suitable for measurement of objects with micron, submicron, and nanometric dimensions. The error of the method, evaluated from the results of measurements of special test gages, did not exceed a few nanometers.

CdS films obtained by graphoepitaxy and investigation of some of their properties

Solid monocrystalline CdS films have been obtained by the method of hot walls on oxidized silicon substrates by graphoepitaxy. Morphological investigations of the initial stages of growth have been carried out with the help of a raster electron microscope. The structure of the grown film is studied by means of X-ray diffractometry, and its composition by Auger spectrometry and cathodoluminescence spectra.

Raster-Electron-Microscopic Investigations in Large-Bore Catheters for Extracorporeal Detoxification

Large bore catheters (n = 42, 31 patients) which remained in position for a period of between 2 to 73 days (mean = 26.8 days/patients) were investigated with raster electron-microscopy (scanning electron micrographic: SEM) and for bacterial colonisation. Microbiological findings indicated colonisation of the intravascular large bore catheters in 8 out of 42 catheters (19%). SEM morphological investigation showed bacterial colonisation in only 3 catheters (7%). The 3 different catheter materials had small deposits of fibrin and protein on the inner and outer surfaces after 2 days. This second layer covered the entire surface after 3 days and increased to a thickness of 3-60 microns in the following days. In this matrix erythrocytes, thrombocytes and granulocytes could also been seen.

Quantitative estimate of the resolving power of a raster electron microscope

Quantitative estimate of the resolving power of a raster electron microscope

Beitrag zur Diskussion um die Morphologie von polyacetylen

AbstractWe analysed by raster electron microscopy Luttinger‐polyacetylene as a powder and as a film, both in pristine and (SbF6−‐electrochemically) doped form. The samples had been intensively washed with MeOH/HCl. One sample had, according to the results of transmission electron microscopy, fiber morphology. All samples show globules as primary structure arranged in clusters (in powder), mono‐layers, or chains (in film) (which previously led to “fibril theory”). The primary spherical particles have diameters from 0,02–0,05 μm. The “fibril” sample has very small spherical primary particles, which may develop using low catalyst amounts. Our results support that the conductivity characteristics is governed by phenomena antiparallel to the chain direction (change‐transfer‐complexes).