The three-dimensional distribution of melt in partially molten synthetic samples compositionally corresponding to diopside (90 wt.%)–anorthite (10 wt.%) and doped with PbO, WO3, MoO3, or Cs2O to enhance contrast was studied by X-ray computed tomography (CT) with synchrotron radiation. The heavy elements were strongly concentrated in the melt and contributed to an increase of the X-ray linear attenuation coefficient (LAC) of it. PbO was found to be compatible with silicate melt (>20 wt.% in solution) and incompatible with diopside crystals. Other oxides WO3 (∼10 wt.%), MoO3 (∼5 wt.%) and Cs2O (< 5 wt.%) are also soluble only in the melt. Such doping is useful not only for LAC control in X-ray CT measurements, but also for systematic control of the structure (wetting properties, distribution and connectivity) of partial melt. This technique gives basic information for discussion of the 3D distribution of partial melt having different wetting properties. As PbO was most effective in visualization of the diopside–anorthite partially molten system, CT images of the PbO-bearing sample were used for further 3D investigation of distribution. A distribution of dihedral angles at solid-melt-solid triple junctions ranging from 22 to 55° was observed with the 3D data. This range in angle distribution was probably caused by anisotropy of crystals and the result supports the argument that there is some limitation in a theoretical framework of stereology which estimates the 3D structure based on 2D observations. Investigators have begun to apply X-ray CT to the study of the 3D distribution of partial melts in rocks using synchrotron radiation. Our study on the effect of doping is one approach for developing a technique to investigate 3D melt distribution.

X-ray powder diffraction data for a new calcium zirconium phosphate Ca7Zr(PO4)6 are reported. The sample was prepared by heating mixtures of CaCO3, ZrO2, and NH4H2PO4 in prescribed molar ratios at 1623 K. Powder diffraction data were collected with a laboratory X-ray source (Cu Kα) for refinement of unit-cell parameters and intensity measurement of individual reflections. Crystallographic data were Ca7Zr(PO4)6, cubic, I-43d (No. 220), a=0.98338(1) nm, V=0.95097(3) nm3, Z=2, and Dx=3.29 Mg m−3. This compound is most probably isomorphous with eulytite.

Nucleation and growth processes of carbon nanotubes (CNTs) in iron catalyzed chemical vapor deposition (CVD) have been observed by means of in-situ environmental transmission electron microscopy. Our atomic scale observations demonstrate that solid state iron carbide (Fe3C) nanoparticles act as catalyst for the CVD growth of CNTs. Iron carbide nanoparticles are structurally fluctuated in CVD condition. Growth of CNTs can be simply explained by bulk diffusion of carbon atoms since nanoparticles are carbide.

Carbon nanotubes (CNTs) have been grown on silicon nanowires (SiNWs) by chemical vapor deposition using Co catalyst nanoparticles. Single-walled CNTs have been grown mainly when a thin Co film (0.1 nm thick) was deposited on SiNWs, while both SWNTs and MWNTs have been grown on SiNWs on which Co 0.5 nm thick was deposited. The correlation between the diameter of catalyst nanoparticles and that of CNTs has been investigated by transmission electron microscopy. The average diameter of CNTs is smaller than that of catalyst nanoparticles.

Silicon carbide nanowires were grown via a self-organized process. Some of the nanowires showed complex diameter fluctuations. The fluctuation was studied from the viewpoints of random walk and fractal. Power spectrum analysis of a fluctuation revealed that the fluctuation was not periodic and that the spectrum was colored. The distribution of increments had a fat tail which was not Gaussian but obeyed power law. Thus the diameter fluctuation was interpreted as a Lévy Flight. In addition, the fluctuation also showed multiaffine scaling.

We have successfully fabricated self-organized GaN nanotips by reactive ion etching using chlorine plasma, and have revealed the formation mechanism. Nanotips with a high density and a high aspect ratio have been formed after the etching. We deduce from X-ray photoelectron spectroscopy (XPS) analysis that the nanotip formation is attributed to nanometer-scale masks of SiO2 on GaN. The structures calculated by Monte Carlo simulation of our formation mechanism are very similar to the experimental nanotip structures.

We investigated the effect of Ge and Si in Cl2 plasma on reactive ion etching (RIE) of GaN. The etched surfaces of GaN were smooth, and high etch rates of 0.63 m/min and 0.41 m m/min were obtained using a Ge plate and a Si plate, respectively. A rough surface was formed for the quartz plate without the Ge plate or Si plate. Optical emission spectroscopy revealed optical emissions related to GeClx+ions in Cl2 plasma with the Ge plate, to SiClx+ ions with the Si plate and to Cl+ ions without the Ge or the Si plate. It is considered that the GeClx+ions and SiClx+ ions for RIE of GaN plays an important role in obtaining a smooth etched surface of GaN, and that the high-energy Cl+ ion severely damages the GaN surface.

We have successfully fabricated self-organized GaN nanotips by reactive ion etching using chlorine plasma, and have revealed the formation mechanism. Nanotips with a high density and a high aspect ratio have been formed after the etching. We deduce from X-ray photoelectron spectroscopy (XPS) analysis that the nanotip formation is attributed to nanometer-scale masks of SiO2 on GaN. The structures calculated by Monte Carlo simulation of our formation mechanism are very similar to the experimental nanotip structures.