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Experimental studies of coalescence between MgO grains and SiO2 grains in smoke reveal the direct production of crystalline forsterite grains and amorphous Mg-bearing silicate owing to the difference of cooling velocity after the formation of Mg2SiO4 (forsterite) grains. This result suggests the observed crystalline Mg2SiO4 grains and amorphous Mg-bearing silicate in RSG, AGB, post-AGB and PNe were produced by the coalescence growth between MgO and SiO2 grains or Mg and SiO grains., 資料番号: AA0046650067

The origin of the strong interstellar 217.5 nm absorption feature appearing in the interstellar extinction curve is a long-standing problem in astrophysics. In the present study, by a simple method, soot with sharp absorption features around 220 nm was produced from methane gas. Interestingly, it was found that the absorption peak positions of the present soot can be controlled by the production temperature. Analyzed results of soot by high-resolution electron microscope clarified that the origin of the absorption peak at 217.5 nm was a graphitic structure with a diameter of 5 nm order., 資料番号: AA0046650066

Carbon soot produced by the gas evaporation technique by the arc-discharge method has been passed through the plasma field. The particles produced in the arc-discharge method helium gas were composed of amorphous carbon and C(sub 6) crystallites. The particles passed through the plasma field were composed of amorphous carbon and larger 300 nm size (111) plate crystal with FCC structure. The larger C(sub 60) crystal formation in the plasma field has been discussed as a result of selective coalescence among C(sub 60) crystallites and the alteration of carbon soot into C(sub 60) crystal., 資料番号: AA0046650068

In order to clarify the correlation between the structure and peak position in quenched carbonaceous composite (QCC), which shows an absorbance peak similar to the 217.5nm feature seen in the interstellar extinction curve, structural changes induced by heating were studied in situ using high resolution electron microscopy. As-prepared QCC particles composed of onion-like spherules changed into a structure with well ordered (002) fringes following heating in vacuum. In addition, formation of microdiamond of about 1 nm in diameter took place by heating at 100℃. The metamorphism is discussed based on a specific configuration of sp^3 hybridization existing on the surface of QCC particles.

In order to elucidate the relationship between crystallographic structures of amorphous silicon oxide grains and infrared (IR) spectra, ultrafine grains produced by the gas evaporation method have been studied on the basis of IR spectral measurements and electron microscopic (EM) observations. The shifts and disappearance in the IR absorption peaks of specimen heat-treated in air have been found. The spectral changes have been discussed in the relation with the polymorphism of silica.

Alumina produced by oxidation of aluminum in air was studied by infrared spectroscopy and electron microscopy. Infrared spectra of both alumina particles and alumina film oxidized in air showed an absorption peak at 10.8μm, though that of γ-Al_2O_3 particles showed a broad 13μm peak. On the basis of the infrared spectra and electron diffraction pattern, it was concluded that alumina produced by the oxidation of aluminum in air is η-Al_2O_3. The phase transition from η-phase to γ-phase and to α-phase took place at 900℃ and 1100℃, respectively. The relationships between infrared spectra and crystal structure of some alumina phases are discussed.

Absorption spectra of SiC particles embedded in KBr pellet have been measured and discussed on to band center change due to crystal structure and defects in crystal. Absorption peaks appearing between 11.3 and 12.6 micrometer were assigned to alpha, beta, 15 R and 21 R, and stacking fault contained in particles., 資料番号: AA0063352048