The directionally solidified Al₂O₃/Y₃Al₅O₁₂ eutectics indicates a fundamental feature, where the crystals of corundum and YAG are finely entangled without grain boundary. This characteristic Chinese script microstructure is suggested to be one of the important factors for providing its useful mechanical performance. Eutectic fiber samples were prepared by the mu-PD method where a fiber sample is pulled down through a capillary hole at the bottom of a conical Ir crucible. The mu-PD apparatus was equipped in a tight SiO₂ glass tube and the atmosphere was controlled by the flowing of Ar gas. The ordinary chemical composition for a corundum/YAG eutectic fiber sample is 81mol% Al₂O₃/19mol%Y₂O₃. The present study also investigate a variety of eutectic samples by exchanging 3 or 5mol% of Al₂O₃ in the parent eutectic fiber sample by the corresponding amount of Fe₂O₃, Cr₂O₃ or Sc₂O₃. The microstructure was studied by the scanning electron microscope(SEM). The crystallographic orientation relationship between corundum and YAG phases was studied by using Precession and Laue photographs. Electron backscattered pattern (EBSP) method was also applied. The non-substituted sample showed the Chinese script microstructure and the present X-ray diffraction study clearly revealed the crystallographic orientation relationship; (1) (001)corundum // (112)YAG perpendicular to the solidified direction and (2) (210)corundum//(432)YAG parallel to the solidified direction. The change in the crystallographic orientation of the corundum phase was also demonstrated in a non-substituted fiber sample prepared by using a corundum (001) seed crystal. The analysis of a series of Precession photographs indicates that the crystallographic orientation of the corundum phase in the eutectic fiber is almost identical to that of the seed crystal at the initial stage of the fiber growth. Nevertheless, the c-axis of the corundum phase lay down perpendicular to the solidified direction, finally. On the other hand, the substitution for Al₂O₃ appears fundamentally to enhance the formation of colony area in the typical Chinese Script microstructure. The Cr₂O₃ is distributed in corundum and garnet structures. On the other hand, Sc2O3 prefers the garnet structure. The reduced FeO component produces another phase of hercynite FeAl₂O₄. The fundamental crystallographic orientation relationship of (001)corundum //(112)YAG, appears to be maintained within an individual colony texture.

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Exsolution lamellar texture of labradorite plagioclase feldspar with blue to brown-yellow iridescence can be observed directly at atmospheric condition by using laser microscopy. Shock metamorphosed texture of quartz cannot be observed as periodic and clear texture with laser microscopy.This is mainly because exsolution texture is comparatively homogeneous and smaller size with large compositional differences.

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Crystallization kinetics of amourphous silica derived from diatom frustules are discussed based on results of super-critical hydrothermal experiments.

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ABSTRACT Topologial whiskers of metals, sulphides, selenides and nitrates showing helical or coil form have recently been synthesized by CVD methods, and attracted renewed interests as potential materials for one dimensional conductors. There have been no report in the mineral kingdom on such whiskers. This presentation reports the first observation in the mineral kingdom of 1) coiled rutile whiskers in transparent quartz, 2) amphibole whiskers showing coil, helical, curl, ribbon and rope forms formed on hedenbergite single crystals in a skarn druse, and 3) frost column of quartz formed simultaneously as 2) on hedenbergite. Rutilated quartz have been used commonly in jewelry fields and the rutile inclusions in quartz usually show needle forms, but hitherto not seriously investigated in terms of whiskers. In a polished transparent quartz sample from Myanmar, rutile whiskers showing coil form are observed together with straight or slightly twisted whiskers. Since no droplet-like particles are present at the tips of whiskers, it is considered that they are not formed by ordinary VLS mechanism, but probably formed through roughening transition of the tip surface owing to de-oxygen process due to impurity adsorption of trivalent cations. On the other hand, whiskers showing forms of coil, helical, curl, ribbon and rope selectively grown from brownish part of short prismatic hedenbergite single crystals in a druse of skarn were identified to be amphibole by micro-area XRF and micro-area XRD methods, and a seam resembling frost column as quartz. Although these whiskers show unusual topological forms, they are crystalline and not amorphous. By means of laser microscopy, it was confirmed that there are always droplet or film like substance having different compositions at the tips of amphibole whiskers, indicating that the whiskers were formed by VLS mechanism. Ribbon and curl whiskers grow from a film, and change their forms to coil, helical and rope at their tips. All these whiskers are bundles of unit whiskers with thickness less than 0.7micron, and at respective tips of unit whiskers droplet like substances are present. Topological forms are results of growth in a bundle, but individual unit whiskers show Eshelby twist. Quartz frost columns observed on the same hedenbergite single crystals together with amphibole whiskers show exactly the same features in texture, mode of occurrence and growth mechanism as ice frost columns. Both amphibole whiskers and quartz frost column were formed by a reaction between hedenbergite and vapor phase containing water and sulfur which intruded into the skarn after completion of growth of hedenbergite, followed by inclusion into later formed calcite crystals.

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Orthoenstatite (OEn) was studied using molecular dynamics (MD) simulations. The MD simulation was carried out on the basis of an interatomic potential model which is taken to be the sum of Coulomb, van der Waals attraction, short range repulsion, and Morse potential terms. The potential parameters were determined empirically. Starting from OEn, the MD simulations were carried out from 300 to 1800 K.

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Most of the solid materials in our solar system are believed to have originated in small grains that condensed during the outflow from a star. Grains are produced by a change from gas phase to solid phase. One of the most advanced methods of forming solid grains from gas phase in the laboratory is the evaporation method in inert gas or reactive gas. Since stars consist of plasma and plasmas exist in interstellar space, it is thought that dust evolves as it passes through the space plasma. Therefore, we tried passing carbonaceous grains into a plasma field. We found that the carbonaceous grains markedly evolved from the structure of original soot. The selective growths of fullerene grains, carbon tubes and carbon onions were found by the use of helium gas methane gases.
Fullerenes were recently detected in the Allende meteorite. The origin of the fullerenes in the Allende meteorite is an intriguing question. The observation of fullerenes together with polycyclic aromatic hydrocarbons (PAHs) suggests that PAHs may have been involved in fullerene synthesis, perhaps with circumstellar envelopes or other formation sites, since such environments generally contain a high abundance of atomic and/or molecular hydrogen.
The electron microscope images and the corresponding electron diffraction patterns of the carbon particles that were produced without passage through plasma and by passage through the plasma region in helium gas atmosphere. When carbon grains were produced without passage through the plasma, spherical carbon grains about 50 nm in size were predominantly produced. The ED pattern showed halo rings, and indicating that the carbon grains were amorphous. The C₆₀ molecules generally comprised about 10 % of the soot produced in helium gas. If the growth conditions, such as gas pressure, source size and source temperature were selected, C₆₀ soot grains with the FCC structure would be seen in the collected soot in smoke. In contrast, when carbon grains were produced by being passed into the plasma region, C₆₀ crystals about 300 nm in size were produced. The growth of the C₆₀ crystal was easily identified by EM imaging. The C₆₀ crystal grown by passage through the plasma region was a plate crystal with a (111) surface plane of the FCC structure. Therefore, the coalescence growth of small crystalline fullerenes was accelerated by passage through the plasma region. Since crystals grow markedly 10 times larger crystal than the size of well-controlled condition in helium gas pressure, the amorphous carbon soot may also coagulate as the C₆₀ crystal with passage through in plasma.

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The 10mum feature of siliceous dust that has been attributed to the stretching mode of the Si-O band has been detected in different objects, such as circumstellar envelopes of evolved stars, planetary nebula, young stellar objects, protoplanetary disks and comets. It is likely that many of grains have undergone some degree of metamorphism since their formation. In a previous paper, the IR spectrum of the film condensed from SiO vapor, which is yellow in color, showed 10mum absorption. After heat treatment in air, IR peak shifted to 9.2mum in spite of exhibiting the diffraction halo. These phenomena can be explained as the result of phase transitions of microcrystallites among polymorphism of SiO₂ structure. In the present study, IR spectra and high resolution transmission electron microscopy(HRTEM) of two grains of SiO with yellow in color and SiO₂ with white in color have been used in order to examine the effect of the heating in vacuum. Experimental studies on the metamorphism of SiO and SiO₂ grains by heating at 10^-6 Pa have been conducted by using a special heating holder attached with a high resolution electron microscope. Si crystallites were predominantly grown at 500 to 700 C in SiO particles. The Si crystallites were disappeared at 800 C and began to evaporate as the SiO phase. In the case of SiO₂ grains, the appearance of Si crystallites seen on a part of SiO₂ grain surface at 900 C accelerated partial evaporation from a surface of SiO₂ particle. These results are analyzed based on electron diffraction patterns and high resolution transmission electron microscopic images.

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The stability and the behavior of hydrous minerals at high pressure and high temperature is of great interest, because the existence of water (actually, hydrogen) in the Earth's mantle could affect physical properties such as mantle rheology and processes such as magma generation and deep seismicity in subduction zones. Our final goal is to discuss this issue from the crystallographic comprehension of hydrogen bonding and compression mechanism of hydrous minerals. Nakamoto et al. (1955) and Novak (1974) reports systematics between hydrogen bonded O...O distance and O-H infrared stretching frequencies. If this systematics can apply to a relationship between pressure variation of O...O distance and O-H infrared stretching frequencies, it is expected that hydrogen bonding strengthens with increasing pressure. We have already reported the compression behavior of some hydrous minerals with weak (brucite and portlandite), intermediate (goethite) and strong hydrogen bondings (kalicinite). In this paper, we will report the compression behavior of nahcolite (NaHCO₃) with strong hydrogen bondings and discuss systematics between pressure variations of hydrogen bonded O...O distances and strength of hydrogen bonding. We used synthetic powder sample of NaHCO₃ and performed angle-dispersive x-ray diffraction experiments at high pressure at BL-18C in the Photon Factory. No observation of significant change in diffraction patterns recorded indicates that there is no structural transition occurs from 0.2 to 9 GPa. Obtained diffraction data were analyzed by the Rietveld structure refinement method under nonlinear constraints for selected interatomic distances and bond angles. We fixed shape of a triangular CO₃^2-. This constrain could be reasonable because it was reported a triangular CO₃^2- ion in several carbonates is almost uncompressed below 10 GPa (Ross and Reeder, 1992, Ross, 1997). The pressure-volume data were fit to a second-order Birch-Murnaghan equation of state. The bulk modulus K=36GPa (K'=4) was obtained. In the crystal structure of NaHCO₃, there are one-dimensional infinite chains of hydrogen bonded bicarbonate ions almost parallel to the [101] direction. The compressibility of the b-axis is the hardest and this indicates that the hydrogen bonded O...O distance should shorten significantly. Indeed, although the hydrogen bonded O...O distance is 2.59 A at 0.2 GPa, the distance shortens to 2.40 A; at 9 GPa. When hydrogen bonded O...O distance becomes about 2.4 A, symmetrization of hydrogen bonding was observed in ice-VI (Hemley et al., 1987, Aoki et al., 1996). The hydrogen bonding in NaHCO₃ at around 9 GPa should be greatly interesting. Since we are now performing IR measurements and neutron diffraction experiments under high pressure, detailed results will come up at the meeting.

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Focused ion beam (FIB) milling is the new means by which mineral sections are thinned to electron transparency for analytical transmission electron microscope (ATEM). We have analyzed the interface between α-Fe and Fe_xO using a combined method of FIB milling and ATEM.

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A method to detect the small diamagnetic anisotropy of nonmagnetic materials has been developed recently. A nonmagnetic material may cause magnetic alignment when it possesses a finite amount of anisotropy however the existence of diamagnetic anisotropy has been ignored for most of the inorganic materials previously. The anisotropy is obtained from the period of field-induced rotational oscillation of the sample. Here the restoring force of a fiber suspending sample, which had been the standard in the anisotropy measurements, was negligible in the method. The anisotropy values of various basic oxides were newly obtained by this method. The origin of the diamagnetic anisotropy was explained by assigning a constant amount of anisotropy to individual bonding orbitals. Accordingly many of the inorganic oxides were expected to cause magnetic alignment, and further improvements on the sensitivity of measurements was required to examine the anisotropy values of other oxides. A system with no fiber was proposed and performed for this purpose, by floating the sample in micro-gravity. It was confirmed that the sensitivity could be improved limitlessly when longer periods of oscillations can be measured for the floated samples at space stations.

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Phylogenetically diverse groups of microorganisms are capable of catalyzing the reduction of highly soluble U(VI) to highly insoluble U(IV), which rapidly precipitates as uraninite (UO₂). Because uraninite is highly insoluble, microbial uranyl reduction is being intensively studied as the basis for a cost-effective in-situ bioremediation strategy. Previous studies have described UO₂ biomineralization products as amorphous or poorly crystalline. The objective of this study is to characterize the nanocrystalline uraninite in detail in order to determine the particle size, crystallinity, and size-related structural characteristics, and to examine the implications of these for reoxidation and transport.In this study, we obtained U-contaminated sediment and water from an inactive U mine and incubated them anaerobically with nutrients to stimulate reductive precipitation of UO2 by indigenous anaerobic bacteria, mainly Gram-positive spore-forming Desulfosporosinus and Clostridium spp. as revealed by RNA-based phylogenetic analysis. Desulfosporosinus sp. was isolated from the sediment and UO₂ was precipitated by this isolate from a simple solution that contains only U and electron donors. We characterized UO₂ formed in both of the experiments by high resolution-TEM (HRTEM) and X-ray absorption fine structure analysis (XAFS).The results from HRTEM showed that both the pure and the mixed cultures of microorganisms precipitated around 1.5 - 3 nm crystalline UO₂ particles. Some particles as small as around 1 nm could be imaged. Rare particles around 10 nm in diameter were also present. Particles adhere to cells and form colloidal aggregates with low fractal dimension. In some cases, coarsening by oriented attachment on {111} is evident. Our preliminary results from XAFS for the incubated U-contaminated sample also indicated an average diameter of UO₂ of 2 nm. In nanoparticles, the U-U distance obtained by XAFS was 0.373 nm, 0.012 nm smaller than found in the bulk structure of UO₂ (0.385 nm). This indicates contraction within the nanoparticles due to tensile surface stress. Microbially formed UO₂ is highly reactive, thus will be oxidized quickly as redox conditions change. Our findings support a growing number of studies that indicate that biominerals formed as the result of enzyme-mediated redox reactions are nanoparticulate. Preliminary results suggest that these particles will be readily transported through sandy aquifers, especially when conditions prevent high degrees of flocculation. Thus, despite its low (but size-dependent) solubility, UO₂ nanoparticle transport may exert a fundamental control on mobility of U in contaminated environments.

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Surface charge and metal adsorption of bacterial cells.

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he main inorganic component of exoskeleton is calcium carbonate and that of endoskeleton is calcium phosphate. However, the causal relationship between the transition of inorganic component and the evolution process of hard tissue has not been well clarified.Some animals in vertebrata with endoskeleton in its inside show a characteristic feature of producing an egg with hard eggshell as exoskeleton. Especially , the egg-laying birds have a special bone, which is named as medullary bone. Medullary bone, which develops reticularly in the bone marrow cavities of the femur and tibia during reproductive period (after 4 months old), is a tissue unique to female birds.In this study, Ca transition from medullary bone as endoskeleton to eggshell as exoskeleton was investigated by the systematic breeding of hens with giving the food including Ca-substitutes (Sr, Mn, Y, K, Fe, Mg) as tracers. Medullary bone includes Sr, K and Fe where the antiphase variation was observed between Sr, Fe and K. Eggshell includes Sr, K., where Sr and K showed the anti-phase features. Eggyolk includes Fe, K., where Fe and K showed the anti-phase features. Egg white and egg membrane included K. The amount of K in egg white shows the antiphase feature against that in egg membrane. The intermediate layered texture between medullary bone and compact bone through the microscopic observations. The results of the analyses showed that the chemical composition varied continuously from compact bone to medullary bone. The tendency is that Ca, P and K decreased continuously from compact bone to medullary bone and that Sr and Zn increased continuously from compact bone to medullary bone.Eggyolk, egg white, egg membrane and eggshell are formed in the different portion of a uterine tube in the different time. The results of the present experiment, K was found together with Fe in eggyolk, in egg white, in egg membrane and with Sr in eggshell. The features of K against Fe in eggyolk, against Sr in eggshell and those in egg membrane and egg white showed the characteristic periodical changes. It indicates that the whole process from fertilization to egg-laying may be systematically interpreted by using K as a key element.

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Several kinds of chitons were studied by SR-XRD and SR-XRF technique in order to elucidate a mechanism of biogenic magnetite formation and differences of tooth components by spieces. At an early stage of tooth formation, ferric iron component was stored into a tooth, then magnetite formation started abruptly. Two dimensional elemental distribution in a tooth was different for individual species of chitons.

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It is known that the diatom has siliceous cell wall. The cell wall consist of upper and lower tow valves which called frustules. The frustules are a porous quality and characteristic various forms therefore the morphological feature has been emphasized before. The micro scale structure is investigated in detail by the development of the electron microscope. But the structure of nano-scale is hardly researched. In this work, we unveil details about the structure in molecular-atomic level and its change by heating using X-ray diffraction and micro-FTIR measurement. Analyzing nanoscale structure of diatom frustules may offer information about interaction between organic-inorganic. Diatom used for structure analysies of the silica-based compound in frustles were collected from acidic hot spring at Kamuiwakka Falls, Shiretoko Peninsula, Hokkaido, Japan. The hot spring water was strong acid the pH of lies between 1.0 ti 2.0. The diatom sample is heated in electric furnace. Then the sample was analyzed by using scanning electron microscopic and energy-dispersion X-ray spectroscopy (SEM-EDX), fourier transform infared absorbance spectroscopy (FT-IR) and powder X-ray diffraction spectrometer (XRD). X-ray diffraction pattern in unheated diatom sample show characteristic broad in amorphous materials. The X-ray diffraction profile and EDX analysis decide that diatom frustule is amorphous silica similar to silica gel. Additionally, weak peak due to crystalline phase present indicate that crystoballite, quartz and other silicate minerals are obtained diatom silica. FTIR spectrum appears band derives from SiO₄ tetrahedra and indicate that organic matter, Si-OH and molecule water exist in the structure. By heating treatment, they disappeared. Si-O peak sifted to high wavenumber and became sharp. First diffraction sharp peak in XRD shape change high temperature. The fact may suggest that middle range structure of frustule change somehow. It possible that crystallization advanced slightly increasing intensity of peak due to crystalline phase.

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Silica, calcite and anhydrite scale precipitated in HDR geothermal system in Hijiori, Yamagata. Silica tends to precipitate in HDR-3 pipeline higher temperature than HDR-2. In the pipeline in HDR-2, calcite precipitates than silica. Anhydrite scale precipitated at reverse temperature zone in the deep part of the production well because the solubility of anhydrite decreased as higher temperature.

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Arsenic contamination of ground water was examined. Three factors were discussed based on examinations. The three are bacterial role, bicarbonate ions, and mica.

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