Synthesis and structure investigation of the Pb3V(PO4)3 eulytite

Lead vanadium phosphate Pb₃V(PO₄)₃ was synthesized by solid state reaction and characterized by X-ray single crystal and powder diffraction, electron microscopy, and magnetic susceptibility measurements. The crystal structure model of Pb₃V(PO₄)₃ was refined using X-ray single crystal data (a=10.127(1)Å, S.G. Z=4). The compound has an eulytite-like structure and its average structure model may be presented as a three-dimensional network formed by strongly distorted mixed (Pb/V^III) metal-oxygen octahedra connected by edge sharing and forming corrugated chains. The octahedra are additionally linked by tetrahedral phosphate groups via corner sharing. Lead and vanadium atoms randomly occupy two close positions in the octahedra. The electron microscopy study revealed the presence of a rhombohedral superstructure with and indicating ordering in the structure. The same type of superstructure was found by us for two another lead-containing eulytite Pb₃Fe(PO₄)₃ where Fe⁺³ has an ionic radius close to that of V⁺³. Magnetic susceptibility measurements revealed Curie-Weiss behavior for the Pb₃V(PO₄)₃ compound.     

Highly active three-component catalytic systems based on dialkylzirconocenes, triisobutylaluminum, and perfluorophenyl borates for synthesis of low-molecular-weight polyethylene

The catalytic properties of the zirconium complex with “constrained geometry” Me₂SiCp^*NBu¹ZrX₂ (Cp^*=C₅Me₄, X=Cl (1a), Me (1b)) and bridged bis(cyclopentadienyl)zirconocene Me₂SiCp₂ZrX₂ (X=Cl (2a), Me (2b)) during their activation with triisobutylaluminum/perfluorophenyl borates (TIBA/LB(C₆F₅)₄, L=CPh₃ (3), Me₂HNPh (4)) in ethylene polymerization under a monomer pressure of 2–20 atm were studied by comparison. Both dichloride complexes exhibit moderate activity under the action of the combined TIBA/3 activating agent and give linear high-molecular-weight polyethylene (PE). The interaction of the dimethyl complexes with TIBA/3(4) afford active sites in which the growing polymeric chain is intensely transferred to the monomer, due to which low-molecular-weight PE is formed. The dichloride complexes affected by TIBA/4 also afford low-molecular-weight PE. Analysis of the structure of the polymeric products (¹H NMR spectrometry, IR spectroscopy), molecular-weight parameters of the PE samples (gel permeation chromatography (GPC)), and kinetics of polymerization suggested that the active site contains AlBuⁱ ₃ as a heteronuclear bridged cationic complex. The influence of various basic substrates (the products of chain transfer with the terminal vinyl groups, the dimethylaniline fragment of borate4 or other amine specially introduced into the reaction mixture) on the catalytic properties of the Zr−Al site was revealed. The polymerization rate and molecular-weight parameters of PE as functions of the reaction temperature, ethylene pressure, and modifying additives were studied. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1189–1198, July, 2000.     

Cluster structure of the material surface as the cause of the selective enhancement of ultracold-neutron capture associated with subbarrier reflection

Neutron-radiation analysis is used to investigate the subbarrier reflection of ultracold neutrons from the surface of a titanium-stabilized Fe-Ni-Cr stainless steel. A significant selective increase in the probability of neutron capture by nuclei of the medium in comparison to theory is discovered. An explanation is given for the effect, which is associated with the existence of titanium-containing clusters and structural defects that distort the form of the distribution of the effective interaction potential between ultracold neutrons and the material surface. Zh. éksp. Teor. Fiz. 115, 126–140 (January 1999)     

Mesomechanics of interface in surface-hardened and coated materials

Results of comprehensive experimental studies and numerical simulations of the plastic deformation processes involved in coated and surface-hardened materials on the mesoscopic and microscopic scale levels are presented. The effects of the processes evolving at the coating/substrate interface on the development of plastic deformation of the entire composition are shown. The data reported provide the basis for the optimization of surface-hardening and coating deposition regimes and the development of advanced materials with outstanding service properties. Institute of Strength Physics and Materials Science of the SB RAS. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, fizika, No. 3, pp. 6–26, March, 1999.     

A Study of the Structure and Strain Resistance of Low-Alloy 09Mn2Si Steel After Its Helical Rolling Under Static and Dynamic Loading

Russian Physics Journal - The structure and mechanical properties of a 09Mn2Si ductile ferritic-pearlitic steel is studied after helical rolling (HR). It is shown that a fine-grained structure is...     

Development and design of a phase-locked loop in the subterahertz and terahertz ranges for a harmonic of the signal of a centimeter-wave synthesizer

We describe a phase-locked loop of a backward-wave oscillator in the range 667–857 GHz for the 34th–45th harmonic of the reference signal of a centimeter-wave synthesizer. Multiplication of the reference-synthesizer frequency in the phase-locked loop is performed by using a subharmonic mixer based on semiconductor superlattices. The mixer, operated at room temperature, has a nonlinear electron conductance.     

Structural Analysis of Armco Iron Subjected to Equal Channel Angular Extrusion

Electron diffraction microscopy of thin foils is used to study the defect substructure of armco iron subjected to equal channel angular extrusion at room temperature, using the processing route A. The morphology of the defect substructure is shown to be substantially affected by the section plane of the billets. The results obtained suggest that the evolution of the defect substructure of the material subjected to equal channel angular extrusion is clearly revealed only by examining no fewer than three mutually perpendicular section planes.__________Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 70–74, April, 2005.     

Neutronographic investigation of the characteristics of phase transition in the alloy Ni3Mn,alloyed with small additions of aluminum and copper

The temperature dependence is studied of the extent of the long-range order and size of the domain in the alloy Ni₃Mn, alloyed with small additions (a few atoms percent) of aluminum and copper. It is shown that A1 stabilizes the superlattice of Ni₃Mn but Cu destroys it. In alloys of Ni₃(Mn, Al) a monotonic effect is observed of the aluminum concentration in the alloy on the nature of the phase transition.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 16–25, November, 1973.