Synthesis and crystal structure of a Pr5Ni19 superlattice alloy and its hydrogen absorption-desorption property

The intermetallic compound Pr(5)Ni(19), which is not shown in the Pr-Ni binary phase diagram, was synthesized, and the crystal structure was investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Two superlattice reflections with the Sm(5)Co(19)-type structure (002 and 004) and the Pr(5)Co(19)-type structure (003 and 006) were observed in the 2θ region between 2° and 15° in the XRD pattern using Cu Kα radiation. Rietveld refinement provided the goodness-of-fit parameter S = 6.7 for the Pr(5)Co(19)-type (3R) structure model and S = 1.7 for the Sm(5)Co(19)-type (2H) structure model, indicating that the synthesized compound has a Sm(5)Co(19) structure. The refined lattice parameters were a = 0.50010(9) nm and c = 3.2420(4) nm. The high-resolution TEM image also clearly revealed that the crystal structure of Pr(5)Ni(19) is of the Sm(5)Co(19) type, which agrees with the results from Rietveld refinement of the XRD data. The P-C isotherm of Pr(5)Ni(19) in the first absorption was clearly different from that in the first desorption. A single plateau in absorption and three plateaus in desorption were observed. The maximum hydrogen storage capacity of the first cycle reached 1.1 H/M, and that of the second cycle was 0.8 H/M. The 0.3 H/M of hydrogen remained in the metal lattice after the first desorption process.     

Rhodium-catalysed intramolecular trans-bis-silylation of alkynes to synthesise 3-silyl-1-benzosiloles

Intramolecular addition of a Si-Si bond across a C-C triple bond occurs in a trans fashion in the presence of rhodium(I) catalysts. The trans-bis-silylation reaction of (2-alkynylphenyl)disilanes affords 3-silyl-1-benzosiloles.     

Simultaneous measurement of velocity and pressure in a plane jet

A new technique was developed for the simultaneous measurement of velocity and pressure in turbulent flows. To accomplish this objective, a new probe (hereafter called the combined probe) that consists of an X-type hot-wire probe and a newly devised pressure probe was developed. The pressure probe was miniaturized by the MEMS fabrication process and by using a 0.1-in. microphone as a pressure sensor for improving the spatial resolution. This pressure probe was placed between two hot-wire sensors of which the X-type hot-wire probe was composed. The pressure probe was given a hemispherical tip, like that of a pitot tube, because an earlier pressure probe with a conical tip suffered from a reduction in spatial resolution. The spatial arrangement of the pressure probe and the hot-wire probe for the combined probe was carefully determined, because there was a risk that the measurement accuracy of one probe will be influenced by disturbances caused by the other probe when the two probes were placed very close to each other. Therefore, the combined probe was arranged to engender no noticeable interference between the velocity data and the pressure data measured by their respective probes. As one application of this combined probe, simultaneous measurements of pressure and two components of instantaneous velocity were performed in a plane jet. The turbulent energy budget and the cross-correlation coefficient of velocity and pressure in the intermittent region of the plane jet were estimated. The results show that the mean streamwise velocity, velocity fluctuation, and pressure fluctuation profiles were consistent with those measured individually using the X-type hot-wire probe or pressure probe. Moreover, it was shown that the integral value of the diffusion term (which should theoretically be equal to zero) in the turbulent energy transport equation was closer to zero than previous reports (Bradbury in J Fluid Mech 23(Part 1):31–64, 1965). In addition, the time variation of the cross-correlation coefficient in the intermittent region supports the vortex structure model predicted in previous studies (Browne et?al. in J Fluid Mech 149:355–373, 1984; Tanaka et?al. JSME Int J Ser B 49(4):899–905, 2006; Sakai et?al. J Fluid Sci Technol 2(3):611–622, 2007).     

Development of an energy‐domain 57Fe‐Mössbauer spectrometer using synchrotron radiation and its application to ultrahigh‐pressure studies with a diamond anvil cell

An energy‐domain ⁵⁷Fe‐Mössbauer spectrometer using synchrotron radiation (SR) with a diamond anvil cell (DAC) has been developed for ultrahigh‐pressure measurements. The main optical system consists of a single‐line pure nuclear Bragg reflection from an oscillating ⁵⁷FeBO₃ single crystal near the Néel temperature and an X‐ray focusing device. The developed spectrometer can filter the Doppler‐shifted single‐line ⁵⁷Fe‐Mössbauer radiation with a narrow bandwidth of neV order from a broadband SR source. The focused incident X‐rays make it easy to measure a small specimen in the DAC. The present paper introduces the design and performance of the SR ⁵⁷Fe‐Mössbauer spectrometer and its demonstrative applications including the newly discovered result of a pressure‐induced magnetic phase transition of polycrystalline ⁵⁷Fe₃BO₆ and an unknown high‐pressure phase of Gd⁵⁷Fe₂ alloy placed in a DAC under high pressures up to 302 GPa. The achievement of Mössbauer spectroscopy in the multimegabar range is of particular interest to researchers studying the nature of the Earth's core.     

Kinetic and theoretical studies of metal ion adsorption in KDP solution

Metal ion adsorption in saturated aqueous potassium dihydrogen phosphate solution was analyzed using kinetic, equilibrium model and computational chemistry approaches. The isotherm constants (K_F and n) in the Freundlich model and the first order Lagergren kinetic model parameter k assist with a general understanding of the fundamental adsorption behavior of trivalent and divalent metal ions. The electrostatic force based on electrostatic potential distribution was found to be an essential feature for metal ion adsorption via a correlation between the ESP values of each metal ion and these experimental parameters.     

Influence of Thomson effect on the resultant local Seebeck coefficient in thermoelectric composite materials

The resultant local Seebeck coefficient α _R (=α _S−α _T) at the interface of a thermoelement has not yet been measured, although it is an important factor governing the thermoelectric efficiency, where α _S is the local Seebeck coefficient and α _T is the one caused by the Thomson effect. It is shown in this paper that α _S, α _T, and α _R of the p- and n-type Cu/Bi–Te/Cu composites are obtained analytically and experimentally on the assumption that the local temperature of the composite on which the temperature difference ΔT is imposed varies linearly with changes in position along the composite. They were indeed estimated as a function of position from the local experimental data of R,ΔI,ΔT, and V generated by applying an additional current of ±I to the composite, where R is the electrical resistance and ΔI is a current generated by the composite. As a result, it was found that the absolute values of α _S at the hot interface of the p- and n-type composites are approximately 1.5 and 1.4 times higher than their lowest values in the middle region of the composite, respectively, while those of α _T are less than 8% of α _S all over the composite and are so small that the relation α _R≈α _S can be held. We thus succeeded in measuring α _R at the interfaces of the composite.     

Synthesis of cinnamyl-sesamol derivatives

A simple synthetic route to cinnamyl-sesamols has been developed starting from sesamol via Claisen rearrangement followed by olefin metathesis reaction.     

Generic phase diagram of Fermion superfluids with population imbalance

It is shown by microscopic calculations for trapped imbalanced Fermi superfluids that the gap function always has sign changes, i.e., the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO)-like state, up to a critical imbalance P(c), beyond which normal state becomes stable, at temperature T=0. A temperature-versus-pressure phase diagram is constructed, where the BCS state without sign change is stable only at T not equal to 0. We reproduce the observed bimodality in the density profile to identify its origin and evaluate P(c) as functions of T and the coupling strength. These dependencies match with the recent experiments.     

Cluster SIMS using metal cluster complex ions

Metal cluster complexes are chemically synthesized organometallic compounds, which have a wide range of chemical compositions with high molecular weight. Using a metal cluster complex ion source, sputtering characteristics of silicon bombarded with normally incident Ir₄(CO)₇⁺ ions were investigated. Experimental results showed that the sputtering yield at 10 keV was 36, which is higher than that with Ar⁺ ions by a factor of 24. In addition, secondary ion mass spectrometry (SIMS) of boron-delta-doped silicon samples and organic films of poly(methyl methacrylate) (PMMA) was performed. Compared with conventional O₂⁺ ion beams, Ir₄(CO)₇⁺ ion beams improved depth resolution by a factor of 2.5 at the same irradiation conditions; the highest depth resolution of 0.9 nm was obtained at 5 keV, 45° with oxygen flooding of 1.3 × 10⁻⁴ Pa. Furthermore, it was confirmed that Ir₄(CO)₇⁺ ion beams significantly enhanced secondary ion intensity in high-mass region.