Observation of carbon by electron microtechniques(<Special issue>The global carbon cycle)

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  • Tazaki Kazue
    Department of Earth Sciences, Faculty of Science, Kanazawa University

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  • 電子線手法を用いた炭素の観察(<特集>地球における炭素の循環)
  • 電子線手法を用いた炭素の観察〔英文〕
  • デンシセン シュホウ オ モチイタ タンソ ノ カンサツ エイブン

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Abstract

Very fine carbon particulates formed by both inorganic and biological processes in the Earth have the most sensitive response to global change. Various electron microtechniques are usufu1 to reveal the micromorphology, texture, growing processes, crystalinity, chemical bond and the distribution of carbon materials. In this article useful methods for evaluation of carbon in various carbon materials are introduced. Amorphous organic carbon naturally and artificially transforms into high crystalline graphite. SEM and TEM observations reveal that precursor carbon materials are composed of spherules, tubular, fiakes, thin films ,fla tsheets, and ribbon texture. Bacteri aand nannobacteria may play a prorninent catalyzing role in the precipitatio onf carbon materia]s. Hexagonal onion-like texture is the most stable form ofcarbon durin ggraphitizatio n,EPMA and Auger can be used for carbon elernentary rnapping. Auger-spectrometer depth profiling and carbon content rnap applied to Sybille Monzosyenite having high electrical conductivity revealed a high concentration of carbon on grain boundaries of the minerals. Chemical bonding of carbon and hydrogen can be analyzed by FT-IR method. FT-IR spectra showing different intensity of OH and C-C absorbed bands are related with the degree of crystalinity of graphite in rocks. The result suggests that graphite occurred by dehydration and reduction of organic materials, ESCA is usufu1 method to know various carbon binding. High resolution of C_ls spectra of micro ESCA can discriminate various carbon chemical binding, such as COO, C-O, C-C, and graphite. ESCA spectra of glauconite in deep sea sediments showed various ratios of COO, C-O, C-C and graphite, suggesting organic origin of glauconite. The result also suggests that there are no clear boundary between organic and inorganic carbon. RILAC method can be used for evaluation of atmospheric contamination of carbon from structural carbon. RILAC spectra of soot showed characteristic recoiled carbon, oxygen and hydrogen ions with standards of purity for metalic plate and Si0_2.

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