Nickel transmission electron microscopy

The adsorption of albumin from aqueous solution onto copper and nickel films and the adsorption of B-lactoglobulin, gum arabic, and alginic acid onto germanium were studied. Thin metallic films (3-4 nm) were deposited onto germanium internal reflection elements by physical vapor deposition. Transmission electron microscopy studies indicated that the deposits were full density. Substrate temperature strongly Influenced the surface structure of the metal deposits. Protein and/or polysaccharide were adsorbed onto the solid substrates from flowing... 

Samples of catalysts B and C were investigated using Transmission Electron Microscopy coupled with Energy Dispersive X-ray Analysis (TEM/EDX). This technique makes it possible to gather elemental data from discreet areas of the catalyst and allows comparison between the nickel areas and the support. The catalyst samples examined had been exposed to the molten carbonate atmosphere for 0, 50,100, 1000 and 2500 hours. 

The in situ precipitation technique and transmission electron microscopy have been used to investigate the effect of DMSO on percutaneous absorption in the mouse barrier [27] and human SC [46]. Sharata and Burnette examined ultrastructural changes in mouse stratum comeum by determining the distribution of sulfide precipitates of topically applied, water-soluble tracers (Hg and Ni ) after application of enhancer [27]. For skin pretreated with DMSO, mercury and nickel precipitates were found within swollen basal stratum comeum cells as well as intercellularly and associated with the cell envelopes, but not below the stratum comeum-stratum granulosum interface. It was concluded that treatment with DMSO, as well as with other dipolar aprotic solvents such as DMF and DMA, alters the passive intercellular diffusion pathway by expanding the size of the basal stratum comeum cells, resulting in an increased free volume for tracer diffusion. 

These assumptions were corroborated by transmission electron microscopy, as can be seen in Figures 5 - 7. The catalyst ex nitrate displays very large nickel oxide particles (Fig. 5) as well as nanoparticles that are confined inside the mesopores of the support (Fig. 6). For the catalyst ex citrate only very small nanoparticles have been observed, which are situated predominantly inside the mesopores of the support material (Fig. 7). 

The results that have been obtained with the catalysts after reduction and passivation are the same as those after calcination, i.e. the textural and structural properties of the support material have completely been retained after the treatments (as determined with nitrogen physisorption. X-ray diflfiaction and transmission electron microscopy). Information concerning the metallic nickel particles has been obtained with X-ray diffraction and transmission electron microscopy. Diflractograms of the catalysts after passivation are shown in Fig. 8. The observed features are exactly the same as for the oxidic systems (Fig. 4) only very broad and low diffractions are visible for the catalyst ex citrate, whereas sharp, intense peaks with a broad onset are observed for the catalyst ex nitrate. Consequently the nickel particles of the catalyst ex citrate have resisted sintering during the reduction treatment, thereby conserving the high dispersion of the catalyst. These results were confirmed by transmission electron microscopy measurements (not shown) only very small nickel nanoparticles situated inside the mesopores were found for the catalyst ex citrate. 

Carbon can exist on the metal surfaces of nickel catalysts in a variety of forms. Hydrocarbon exposure to nickel crystallites at elevated temperature (> 700 K) can rapidly produce a mass of long-growing carbon filaments (1, 2) as identified in numerous experiments analyzed by transmission electron microscopy (TEM). Yet very reactive forms of surface carbon can exist, since carbon atoms chemisorbed on nickel surfaces apparently play a central role in the mechanism of several nickel-catalyzed reactions, such as hydrocarbon synthesis, (3, U, 5) hydrocarbon steam reforming, (6, 7) and hydrogenolysis (8). 

IGC at elevated temperatures is a serious problem in the sulfidation of nickel alloys. Deep penetration can occur rapidly through the thickness of the alloy. This type of IGC can be evaluated by (i) X-ray mapping during examination by a scanning electron microscope equipped with an energy-dispersive X-ray detector and transmission electron microscopy (4). 

The growth mechanism appears to be the same, irrespective of the hydrocarbon. However, the resulting morphology depends not only on the metal and particle size but also on the type of hydrocarbon and the reaction temperature. The importance of step sites on the catalyst surface for the nudeation of carbon was recently confirmed by in situ investigations employing high resolution transmission electron microscopy the results indicate the segregation of carbon when the formation of whiskers takes place at specific sites on the nickel surface. The addition of potassium to the nickel catalyst leads to an increase in the induction period (t ) for CH4 decomposition, which... 

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