METHODS TO DETERMINE CRYSTAL LATTICE PARAMETERS OF OPAL-LIKE STRUCTURES

Journal of Structural Chemistry - Series of high-quality spherical poly(methyl methacrylate) particles with a polydispersity less than 5% are prepared by chain-growth emulsifier-free controlled...     

Thermal Oxidation of a Carbon Condensate Formed in High-Frequency Carbon and Carbon–Nickel Plasma Flow

We have reported on the comparative characteristics of thermal oxidation of a carbon condensate prepared by high-frequency arc evaporation of graphite rods and a rod with a hollow center filled with nickel powder. In the latter case, along with different forms of nanodisperse carbon, nickel particles with nickel core–carbon shell structures are formed. It has been found that the processes of the thermal oxidation of carbon condensates with and without nickel differ significantly. Nickel particles with the carbon shell exhibit catalytic properties with respect to the oxidation of nanosized carbon structures. A noticeable difference between the temperatures of the end of the oxidation process for various carbon nanoparticles and nickel particles with the carbon shell has been established. The study is aimed at investigations of the effect of nickel nanoparticles on the dynamics of carbon condensate oxidation upon heating in the argon–oxygen flow.     

Phase formation upon crystallization of SrO · 2B<Subscript>2</Subscript>O<Subscript>3</Subscript> glasses

The crystallization of SrO · 2B₂O₃ glasses has been studied. Four different crystalline formations were found to form simultaneously and independently on the glass surface: stable α-SrB₄O₇ crystals and metastable crystalline forms (β-SrB₄O₇, Sr₄B₁₄O₂₅, and spherulites (presumably, mixtures of crystalline phases)). The ranges of thermal stability of the newly formed metastable phases have been established using thermal analysis.     

Frequency doubling of ultrashort pulses in a nonlinear photonic strontium tetraborate crystal

The second harmonic generation (SHG) of the femtosecond titanium-sapphire laser radiation was experimentally studied in the mode of nonlinear diffraction in the nonlinear photonic strontium tetraborate crystal. The spectrum of reciprocal lattice vectors of domain structures includes components responsible for the efficient frequency-tunable SHG in the spectral range of 355–510 nm. The maximum SHG efficiency was 1.9%. The SHG spectrum narrowing does not exceed 10–20%. The measured spectral dependence of the nonlinear diffraction angle is in good agreement with calculation.     

Caloric characteristics of PbTiO3 in the temperature range of the ferroelectric phase transition

The heat capacity and thermal expansion of the PbTiO₃ ceramic sample have been measured in the temperature range 80?C970 K. The electrocaloric and barocaloric efficiencies of lead titanate in the ferroelectric phase transition range have been investigated by analyzing the experimental data in terms of the thermodynamic theory of phase transitions, the electrical equation of state P(T, E), the Pippard equation, and the S(T, p) diagram.     

Decoration of Carbon Nanomaterial Powders with Dispersed Platinum Metal Particles

Russian Journal of Applied Chemistry - Carbon nanomaterials (fullerite, detonation nanodiamonds, Taunit, fullerenol, fullerene-containing black) were decorated with platinum group metal...     

Hydrogenation of the nanopowders that form in a carbon-helium plasma stream during the introduction of Ni and Mg

Composite nanoparticles consisting of magnesium, nickel, and carbon atoms are studied both theoretically and experimentally. The calculations performed in terms of the density functional theory show that the jump frequency of hydrogen atoms in nickel-containing magnesium hydride increases substantially near impurity nickel atoms; as a result, the rate of hydrogen absorption by magnesium also increases. Nickel on the magnesium surface is shown to be absorbed via an island growth mechanism. Composite Mg-C, Ni-C, and Mg-Ni-C powders are produced by plasmachemical synthesis in a carbon-helium plasma stream. Hydrogen is introduced into a chamber during synthesis. It is found by X-ray photoelectron spectroscopy and thermogravimetric analysis that, among these three composites, only Mg-Ni-C contains magnesium fixed in the MgH₂ compound. The process of such “ultrarapid” hydrogenation of magnesium, which occurs in the time of formation of composite nanoparticles, can be explained by the catalytic action of nickel, which is enhanced by a high temperature. Scanning electron microscopy micrographs demonstrate the dynamics of the dehydrogenation of Mg-Ni-C composite nanoparticles in heating by an electron beam.     

N,O-ditosylethanolamine as effective reagent for the synthesis of heterocyclic tertiary amine salts

During the synthesis of N-tosylaziridine, two unexpected products were isolated: 1-(2-(p-tolylsulfonamido)ethyl)pyridinium p-tolylsulfonate (3) and N,N,O-tri-(p-tolylsulfonyl)ethanolamine (3a). The structures of 3 and 3a were investigated in solid state by X-ray analysis. A new family of related salts was obtained using an efficient and facile one-pot synthesis consisting in the interaction between various nitrogen heterocycles and N,O-ditosylethanolamine.