The S-D transition and high-pressure phase stability of transition metals

Abstract

The recent discovery of a solid-solid phase change in shock-compressed Mo and the theoretical interpretation suggest valence d-electron density as a major influence on structural stability. The relationship of this experimental result to the transition metal structures and alloy phase diagrams will be discussed. Specific predictions will be presented for the locations and slopes of transition metal and transition metal alloy phase boundaries.     

Selective preconcentration of trace thorium from aqueous solutions with Th(IV)-imprinted polymers prepared by a surface-grafted technique

A novel ion-imprinted adsorbent for selective solid phase extraction of thorium(IV) based on the surface of silica gel was prepared by a surface-grafted technique with methacrylic acid (MAA) as a functional monomer. After removal of Th(IV) ions with 3?mol?L^?1 HCl solution, the obtained imprinted particles for Th(IV) exhibited specific recognition and relatively rapid kinetic process. The maximum static and total dynamic adsorption capacity of the ion-imprinted polymers (IIPs) for Th(IV) was 33.2 and 17.3?mg?g^?1, respectively. A comparison of the selectivity coefficient of the imprinted polymers with that of non-imprinted polymers showed that the imprinted matrix for Th(IV)/U(VI), Th(IV)/Ce(III), Th(IV)/La(III) and Th(IV)/Zr(IV) was 58.8, 107, 106.4 and 151.7 times greater than non-imprinted matrix, respectively. With a series of samples loading flow rate of 3?mL?min^?1 for preconcentration, an enrichment factor of 14.6 and the detection limit of 0.59?µg?L^?1 were obtained. The relative standard deviation of the method under optimum conditions was 2.1% (n?=?7). The developed method was successfully applied to the determination of trace Th(IV) in real water samples with satisfactory results.     

Determination of Uranium in Natural Waters by Solid Phase Spectrometry

Abstract

A microdetermination method (at the μg1^?1 level) for uranium has been developed, based on Solid-Phase Spectrophotometry (SPS). The uranium reacts with pyridylazo-resorcinol in the presence of fluoride to form a 1:1:1 red ternary complex, which is fixed on an anion-exchange resin. The resin absorbance is measured directly, and allows the determination of uranium in the range of 1–10μg1^?1, with an RSD of 4%. The method has been applied to the determination of U(VI) in natural waters from wells located near the deposits of industrial wastes from a uranium mineral plant in Andujar (Spain).     

Hexagonal columnar mesophases of polycatenar para-phenylene connected bis-oxadiazole-based liquid crystals

In this article polycatenar liquid crystals containing two 1,3,4-oxadiazoles interconnected by a para-substituted benzene ring as the central linking unit and three alkoxy chains at each terminal have been synthesised, and investigated by polarising microscopy, DSC and XRD scattering. Molecules with medium chain length form exclusively hexagonal columnar liquid crystalline phases.     

Phase transitions,optical, dielectric and viscoelastic properties of colloidal suspensions of BaTiO3 nanoparticles and cyanobiphenyl liquid crystals

We report experimental studies on the phase transitions and physical properties of colloidal suspensions of BaTiO₃ nanoparticles and two cyanobiphenyl liquid crystals (4-pentyl-4?-cyanobiphenyl and 4-octyl-4?-cyanobiphenyl). From the differential scanning calorimetric measurements, we show that the nanoparticles have antagonistic effect on the isotropic to nematic and nematic to smectic-A phase transitions. The birefringence, dielectric anisotropy and splay elastic constant remain almost unchanged, whereas the bend elastic constant and rotational viscosity decrease considerably. The experimental results are discussed based on the possible contribution of BaTiO₃ nanoparticles and free surfactant molecules in the suspensions.     

Effects of additives and post‐treatment on the thermoelectric performance of vapor‐phase polymerized PEDOT films

Vapor‐phase polymerization (VPP) is an important method for the fabrication of high‐quality conducting polymers, especially poly(3,4‐ethylenedioxythiophene) (PEDOT). In this work, the effects of additives and post‐treatment solvents on the thermoelectric (TE) performance of VPP‐PEDOT films were systematically investigated. The use of 1‐butyl‐3‐menthylinidazolium tetrafluoroborate ([BMIm][BF₄], an ionic liquid) was shown to significantly enhance the electrical conductivity of VPP‐PEDOT films compared with other additives. The VPP‐PEDOT film post‐treated with mixed ethylene glycol (EG)/[BMIm][BF₄] solvent displayed the high power factor of 45.3 μW m^?1 K^?2 which is 122% higher than that prepared without any additive or post‐treatment solvent, along with enhanced electrical conductivity and Seebeck coefficient. This work highlighted the superior effect of the [BMIm][BF₄] additive and the EG/[BMIm][BF₄] solvent post‐treatment on the TE performance of the VPP‐PEDOT film. These results should help with developing the VPP method to fabricate high‐performance PEDOT films. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55 , 1738–1744     

A convenient One-Pot Synthesis of an Unsymmetrical Propane-1,3-diamine BRL 61010A

The one-pot condensation of N-methylhomoveratrylamine with acrolein followed by in situ reductive amination with 3,4-dimethoxyaniline to give an unsymmetrical propane 1,3-diamine in excellent yield is described.     

Dioxane Dibromide–Mediated Solvent‐Free Synthesis of Vicinal Dibromides

Structurally varied vicinal dibromides have been synthesized in high yield and good purity through highly stereoselective anti‐addition of bromine across the olefinic linkages using dioxane dibromide (DD) under solvent‐free conditions.     

Synthesis of the Novel Chiral Catalysts by Click Chemistry and Their Application

Novel cinchonine ammonium salt derivatives have been prepared by 1,3‐dipolar cycloaddition. Their chiral catalytic efficacy was investigated in the asymmetric alkylation of N‐diphenylmethyleneglycine t‐butyl ester in the water phase. As the special structure of the catalyst, its asymmetric alkylation catalytic behavior both in organic solvents and in water is satisfactory, which is environmentally friendly.     

Electronic Structure of Some Possible Organic Ferromagnets

A semiempirical method has been used to study the electronic structures of some π-bonded purely organic materials that are either known or proposed to have multiplet ground states. These materials are the precursors of organic ferromagnets. Narrow energy bands formed from the radical π-orbitals of these materials are necessary for the π-electrons to be unpaired. Favorable topological arrangements of atoms in these materials are needed to enable the spins of these electrons to align parallel, and hence yield macroscopic ferromagnetic ordering. Following ideas based on these studies, a new model for a possible organic ferromagnet is proposed and studied.