Elemental composition heterogeneity

The transmission electron microscope is now well established as a useful tool for the characterization of supported heterogeneous catalysts(l). Axial bright-field imaging in the conventional transmission electron microscope (CTEM) is routinely used to provide the catalyst chemist with details concerning particle size distributions, 3), particle disposition over the support material(2-6) as well as particle morphology(7). Internal crystal structure(8-10), and elemental compositions(ll) may be inferred by direct structure imaging. 

Fast pyrolysis oil has almost the same elemental composition as the biomass itself hence it can be seen as a kind of liquid wood. It can be transported, can be pressurized and processed more easily than solid biomass. One of the major difficulties in the catalytic conversion of solid biomass is achieving effident con-tad between the heterogeneous catalyst (which is most of the times a solid) and the biomass itself. In this context, bio-oil provides more options for easier catalytic conversion. However, pyrolysis is a very complex and the oil is a difficult to handle chemical mixture. Complete vaporization, for instance, is not possible because part of the components start to decompose and polymerize upon heating... 

Analytical electron microscopy is the most sophisticated tool available for micro-structural analysis today. In this method, we can obtain both the high-resolution structure and elemental composition of a specimen. This is probably the best technique to obtain local elemental composition of small regions of heterogeneous solids. When a high-energy electron beam is incident on a specimen, we get elastically and inelastically... 

The deposition of FDR is a very random process and the elemental composition of discharge particles is very heterogeneous. I have read scientific papers using elemental content and inter-elemental ratios of individual particles to... 

Because of the normal heterogeneity of soil and because of possible unnatural alterations introduced at the time of burial, such as grave goods that have since decomposed, elemental analysis of soils and discernment of spatial trends of specific elements are fraught with difficulties. Nonetheless, we believe that we have documented permanent and diagnostic alterations in the soil composition as the result of elemental interchange with the skeleton. Furthermore, these observations correspond in almost every detail to those made in our study of the relative elemental compositions of excavated human ribs and femurs (8). 

In certain areas of science and engineering, the elemental composition of a surface layer of solid that is a few angstroms to a few tens of angstroms thick is of much greater interest than the bulk elemental composition. Fields where surface composition is extremely important include heterogeneous catalysis, corrosion and adhesion studies, embrittlement properties, and studies of the behavior and functions of biological membranes. 

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