Materials for bipolar plates for proton-conducting membrane fuel cells

The review is devoted to the present state of research and development in the field of construction materials for bipolar plates for hydrogen-air fuel cells with polymeric proton-conducting membranes. Principal requirements for such materials are considered and criteria for their selection are formulated.     

Magnetoelastic Volume Shear Waves in a Periodically Layered Medium

An approach is developed for studying the propagation of magnetoelasic waves in layered structures. The structures have the properties of ferrite with interfaces differently covered with a metal coating. The problem is reduced to an infinite equation system within the framework of the linearized theory of magnetoelasticity. Conditions of volume-wave propagation are derived from the condition of existence of a nontrivial solution to this system. Some results are presented in the form of plots     

Vortices on the Surface of Normal He I Generated by the Rayleigh–Bénard Thermogravitational Convection in the Bulk of a Liquid

JETP Letters - It has been experimentally found that the appearance of the Rayleigh–Bénard thermogravitational convection in the bulk of a normal helium He-I layer heated from above in...     

Investigation of texture characteristics of the technosorb carbon material in the oxidation process

Texture characteristics of the oxidized Technosorb carbon material were investigated. The BET surface area, specific surface area of mesopores, mesopore diameter distribution, and total pore volume were determined using an ASAP 2400 adsorption instrument and a Sorbtometer-M analyzer. Changes in the texture characteristics upon oxidation were monitored.     

A high-intensity bremsstrahlung source for investigating radiation stability of optical samples for excimer laser windows

A bremsstrahlung X-ray source (hv ≤ 600 keV) was developed on the basis of CW electron LINAC. It provides an absorbed dose rate of ∼30 Gy/s within an area of ∼2.5 cm². The radiation stability of quartz glasses and crystals for excimer lasers windows was investigated.     

Beyond vinyl: electronic structure of unsaturated propen-1-yl, propen-2-yl, 1-buten-2-yl, and trans-2-buten-2-yl hydrocarbon radicals

Vertical excitation energies and oscillator strengths for several valence and Rydberg electronic states of vinyl, propen-1-yl, propen-2-yl, 1-buten-2-yl, and trans-2-buten-2-yl radicals are calculated using the equation-of-motion coupled cluster methods with single and double substitutions (EOM-CCSD). The ground and the lowest excited state (n <-- pi) equilibrium geometries are calculated using the CCSD(T) and EOM-SF-CCSD methods, respectively, and adiabatic excitation energies for the n <-- pi state are reported. Systematic changes in the geometries, excitation energies, and Rydberg state quantum defects within this group of radicals are discussed.     

Photodissociation dynamics of the NO dimer. I. Theoretical overview of the ultraviolet singlet excited states

Molecular orbital theory and calculations are used to describe the ultraviolet singlet excited states of NO dimer. Qualitatively, we derive and catalog the dimer states by correlating them with monomer states, and provide illustrative complete active space self-consistent field calculations. Quantitatively, we provide computational estimates of vertical transition energies and absorption intensities with multireference configuration interaction and equations-of-motion coupled-cluster methods, and examine an important avoided crossing between a Rydberg and a valence state along the intermonomer and intramonomer stretching coordinates. The calculations are challenging, due to the high density of electronic states of various types (valence and Rydberg, excimer and charge transfer) in the 6-8 eV region, and the multiconfigurational nature of the ground state. We have identified a bright charge-transfer (charge-resonance) state as responsible for the broadband seen in UV absorption experiments. We also use our results to facilitate the interpretation of UV photodissociation experiments, including the time-resolved 6 eV photodissociation experiments to be presented in the next two papers of this series.     

Pressure effect and crystal structure reinvestigations on the spin crossover system: [Fe(bt)2(NCS)2] (bt = 2,2'-bithiazoline) polymorphs A and B

The crystal structure of [Fe(bt)2(NCS)2] (A) was determined by X-ray diffraction at 293 and at 150 K in order to analyze the structural changes associated with the spin transition. The space group is P1 with Z = 2 at both temperatures. Lattice constants are as follows: a = 8.5240(4), b = 11.0730(6), c = 12.5300(8) at 293 K and a = 8.1490(4), b = 11.4390(5), c = 12.1270(6) at 150 K. The iron(II) atom lies at the center of a distorted [FeN6] defined by two bt ligands arranged in a cis conformation. The two remaining coordination positions are occupied by two isothiocyanate anions. The average bond lengths of 2.159(4) A (293 K) and 1.951(2) A (150 K) clearly indicate the change in spin configuration. The trigonal distortion parameter phi has a value of 9.6 degrees and 5.5 degrees at 293 and 150 K, respectively. For A, DeltaV = DeltaV(SCO) = 28 A(3) per formula unit and is accompanied by a hysteresis of 10 K. chi(M)T vs T curves at atmospheric pressure for A show an abrupt spin transition with Tc downward arrow = 176 K and Tc upward arrow = 187 K. The thermodynamic parameters associated with the spin transition are DeltaH = 8.4 +/- 0.4 kJ mol(-1) and DeltaS = 46.5 +/- 3 J K mol(-1). The thermal dependence of the magnetic susceptibility at different pressures, 0.1-0.91 GPa, points out an unusual behavior, which can only be understood in terms of a crystallographic phase transition or a change in the bulk modulus of the complex. Polymorph B crystallizes in the C2/c space group with an average Fe-N bond length of 2.168(2) A and phi = 14.7 degrees at 293 K. B remains in the HS configuration even at pressures of 1.06 GPa.