Variations of lattice constants and thermal expansion coefficients of indium at high pressure and high temperature

ABSTRACT

The effects of pressure and temperature on the lattice constants and thermal expansion coefficients of Indium were studied up to 18.6?GPa and 506?K based on in situ X-ray diffraction method with an externally heated diamond anvil cell. The results show that the measured axial ratio (c/a) decreases with increasing temperature and its temperature dependence decreases with increasing pressure. The thermal expansion coefficient of the a-axis decreases with increasing pressure up to 7?GPa and remains almost constant above 7?GPa, whereas that of the c-axis increases monotonously with pressure and changes from negative to positive at around 7?GPa. The observed behavior suggests that temperature reduces the tetragonal distortion on the lattice, and its effect is dominant below 7?GPa; in contrast, pressure enhances lattice distortion, and tends to have a stronger effect above 7?GPa.     

Mechanistic Insights on Reduction of Carboxamides by Diisobutylaluminum Hydride and Sodium Hydride−Iodide Composite

The reaction mechanisms on reduction of tertiary carboxamides by diisobutylaluminum hydride (DIBAL) and sodium hydride (NaH)‐sodium iodide (NaI) composite were elucidated by the computational and experimental approaches. Reduction of N,N‐dimethyl carboxamides with DIBAL provides the corresponding amines, whereas that with the NaH?NaI composite exclusively forms aldehyde even at high reaction temperature. DFT calculations revealed that dimeric structural nature of DIBAL and Lewis acidity on its Al center play crucial role to decompose the tetrahedral anionic carbinol amine intermediate through C?O bond cleavage. On the other hand, in the reduction with the NaH?NaI composite, the resulting tetrahedral anionic carbinol amine intermediate could be kept stable, thus providing aldehydes as a sole product by the aqueous workup     

Microscopic state of the positive muon in 2H-NbSe2

The microscopic state of the positive muon in the transition metal dichalcogenide 2H-NbSe₂ was studied using the muon spin relaxation method (μ⁺SR). We found that the μ⁺SR spectra consist of two components. The ratio of the two components and the dynamics of the muon change at 140 K, at the charge-density-wave transition temperature (32 K), and again at the superconducting transition temperature (7 K). We discuss the relation between conduction electron properties and the muon's behavior. This revised version was published online in August 2006 with corrections to the Cover Date.     

Cationic Axial Ligand Effects on Sulfur-Substituted Subphthalocyanines

Herein, we report the synthesis of sulfur-substituted boron(III) subphthalocyanines (SubPcs) with cationic axial ligands. Subphthalocyanines were synthesized by a condensation reaction using the corresponding phthalonitriles and boron trichloride as a template. An aminoalkyl group was introduced on the central boron atom; this process was followed by N-methylation to introduce a cationic axial ligand. The peripheral sulfur groups shifted the Q band of SubPcs to a longer wavelength. The cationic axial ligands increased the polarity and enhanced the hydrophilicity of SubPcs. The effect of axial ligands on absorption and fluorescence properties is generally small. However, a further red shift was observed by introducing cationic axial ligands into the sulfur-substituted SubPcs. This change is similar to that in sulfur-substituted silicon(IV) phthalocyanines. The unique effect of the cationic axial ligand was extensively investigated by theoretical calculations and electrochemistry. In particular, the precise oxidation potential was determined using ionization potential measurements. Thus, the results of the present study provide a novel strategy for developing functional dyes and pigments based on SubPcs.     

In-situ electrical measurement in ion implanted amorphous silicon films

Doping in amorphous silicon has been studied by P, B and Si implantation in evaporated silicon films made by electron beam evaporations. After double implantation of P and B, a compensation effect has been observed in implanted amorphous silicon layer.     

Synthesis of 3-deazaoxanosines,C-nucleoside isosteres of oxanosine

The synthesis of 3-deazaoxanosines, C-nucleoside isosteres of oxanosine, is described.     

Hybrid mode trasmission in 62-m corrugated waveguide

Experimental measurements by wavepacket reflectometry are carried out to verify the low transmission loss of hybrid mode on HE₁₁ in the corrugated waveguide with 88.9 mm in diameter. The HE₁₁ mode is injected into the 62-m straight circular corrugated waveguide and the beat between the HE₁₁ and HE₂₁ (including degenerated TE₀₁ and TM₀₂) modes is observed. The loss is too small to measure and inferred to be less than 2 db/km. The result shows that the use of HE₁₁ mode for electron cyclotron heating system is suitable.     

Catalytic decomposition of CFCs

Catalytic decomposition of CCI₂F₂ was studied over a number of single and complex metal oxides using a fixed-bed reactor. The ZrO₂–Cr₂O₂ catalyst exhibited the highest activity and CO₂ and CCIF₃ were formed at 350–450°C. Selective decomposition of CCI₂F₂ required the presence of both oxygen and water vapor over the catalyst. Catalytic activity gradually declined with time on stream because of the fluorination of ZrO₂. Treatment of the catalyst with both oxygen and water vapor promoted the removal of fluoride ions in sub-surface layers of the catalyst, which is effective for the recovery of the activity. CCI₂F₂ was decomposed at 300–450°C over AIPO₄. No fluorination of the AIPO₄ catalyst took place after the reaction for 1000 h. CH₂FCF₃, an alternative CFC, was completely decomposed over the mixed catalyst of Ce promoted AIPO₄ and Cr₂O₃ at 400–500°C. Catalytic decomposition is a rational method for destruction of used CFCs.     

A new reforming process based on CH4 decomposition using a hydrogen-permeating membrane reactor

A new reforming process was studied using Ni/SiO₂ with a hydrogen-permeating membrane reactor. Nickel catalyst supported on SiO₂ is highly active for CH₄-H₂O-O₂ reaction in membrane reactor and the reaction close to CH₄ + 0.35O₂ + 1.3H₂O → CO₂ + 3.3H₂ proceeds at 873 K. Since the selectivity to carbon and CO₂ increased and decreased with decreasing contact time respectively, it is considered that the reaction was started by decomposition of CH₄ followed by oxidation of C and water shift reaction. Therefore, the reaction mechanism was different from so-called autothermal reforming (ATR) reaction.     

Poly(thiaheterohelicene): a stiff conjugated helical polymer comprised of fused benzothiophene rings

A novel helical aromatic polymer comprised of fused benzothiophene rings, poly(thiaheterohelicene), was synthesized via an intramolecular ring-closing reaction with a controlled helicity to one-sided bias. The synthetic helicity control involved the induction of the helical conformation and its fixation. The ladder polymer showed both an extended pi-conjugation and planarity and a very stiff helical structure. [structure: see text]