Effect of synthesis methods on the morphology of nanosized tin dioxide particles

The effect of precursors on the microstructure of nanocrystalline tin dioxide is studied by thermal analysis, IR spectroscopy, electron microscopy, and X-ray powder diffraction. The precursor precipitated in an optimal pH range whose dehydration and crystallization occur over a wide temperature range with low degrees of oxolation yields crystalline tin dioxide with grain sizes on the order of 16 nm upon calcination at 800°C for 2 h.     

Photocatalytic Activity of Zinc Oxide Nanoparticles Prepared by Laser Ablation in a Decomposition Reaction of Rhodamine B

Russian Physics Journal - The development of the routes for synthesizing photocatalysts and the methods for investigating their properties is very appealing for applications in ecology and...     

Stability of Cylindrical Shells with Local Imperfections

We propose a nonlinear approach to the stability analysis of imperfect cylindrical shells under axial compression. The approach takes into account the initial deflections (imperfections) of the shell shape from cylindrical. A series of typical initial deflections is analyzed: local and longitudinal bulges (dents) and unilateral annular corrugations. A nonlinear stability problem is solved. The results are represented as plots of the nondimensional stress versus the nondimensional amplitude of initial deflections. It is shown that the capabilities of the nonlinear theory for estimating the critical stresses for thin shells have not been exhausted yet and that it could be used in future to explain some phenomena experimentally observed in shells     

Redox and acid-base properties of 2,6-dichlorophenolindophenol immobilized on a polymethacrylate matrix

The effect of the immobilization of 2,6-dichlorophenolindophenol (DCIP) on a polymethacrylate matrix on its redox and acid-base properties was studied. The ionization constant and formal redox potentials of the immobilized DCIP were determined by solid-phase spectrophotometry. It was shown that the acidity constant and the formal potentials of DCIP decreased upon the immobilization in the polymethacrylate matrix. The results of studying the interaction of ascorbic acid with immobilized DCIP are presented.     

Terahertz spectroscopy of quantum-well narrow-bandgap HgTe/CdTe-based heterostructures

The energy spectra of quantum-well narrow-bandgap Hg_{1 ? y} Cd _y Te/Cd _x Hg_{1 ? x} Te heterostructures have been studied. The dependences of the effective cyclotron mass on the density (in classical magnetic fields) and the transition energy (in quantizing fields) have been obtained from the cyclotron resonance measurements. These dependences confirm the near-linear dispersion law for the electrons with small mass at the band bottom (the minimum cyclotron mass measured is 0.003 m ₀). The interband photoconductivity of the CdHgTe-based structures with the long-wavelength photoresponse edge lower than 6 meV has been demonstrated.     

“From Heteronuclear Complex to Composite Oxide” Approach in the Synthesis of Nanosized Ferrites MIIFeIII 2O4 (M = Mn,Co, Ni) with Spinel Structure and Their Catalytic Properties

A study was carried out on the preparation of ferrites M^IIFe₂O₄ (M^II = Mn, Co, Ni) by the thermal decomposition of the corresponding ₃-oxoacetates [Fe₂M^IIO(CH₃COO)₆(H₂O)₃]·2H₂O. Nanocrystallites of M^IIFe₂O₄ were formed under mild conditions at 300-400 °C in this reaction. An increase in the temperature leads to an increase in particle size. Nickel ferrite showed high catalytic activity in the reduction of nitrogen oxides (NO _x ) by hydrocarbons.     

Crystal structure of sakhaite from the Solongo deposit in connection with the crystallochemical interpretation of the sakhaite-harkerite mineral series

The crystal structure of mineral sakhaite Ca₄₈[Mg_13.2(Fe, Mn)_2.8](CO₃)₁₆{ Al[SiO_3.75(OH)_0.25]₄}(BO₃)₂₈[(H₂O)_3.3(HCl)_3.3] from the Solongo deposit, Zabaykalye, is established (R 0.047) by X-ray diffraction analysis (Bruker Smart CCD diffractometer, 2θ: θ scan, λMoK_α radiation, graphite monochromator): a = 14.679(2) Å, sp. gr. Fd3m, Z = 1, ρ_calcd = 2.99 g/cm³. It is shown that some part of BO₃ triangles in the structure of sakhaite from Solongo is replaced with five-member complexes {Al[SiO₃(O,OH)]₄}, established previously in the harkerite structure. Three schemes of isomorphism, which are characteristic of the sakhaite-harkerite mineral series, are selected and the general formula is proposed: Ca₄₈(Mg,Fe,Mn)₁₆(CO₃)₁₆{Al[SiO₃(O, OH)]₄}_y(B₃)_32?y · n(H₂O,HCl) (Z = 1), y_max = 8, n_max = 16 ? y. The structural relationship of sakhaite-harkerite minerals with borate-sulfates of the tychite family Na₆(Mg,Fe,Mn)₂(BO₃)₄(SO₄) is revealed. The correlation between the number of harkerite fragments forming the mineral structure, the structural symmetry, and the degree of imperfection is ascertained.     

Crystal structure of the Na-, Ca-, Be-cordierite and crystallochemical regularities in the cordierite—sekaninaite series

The crystal structure of the beryllium-rich cordierite [(Na_0.28Ca_0.19)(H₂O)_0.92](Mg_1.86Fe _0.14 ^22? ) · { Al_3.39Be_0.61Si₅O₁₈} was established by X-ray diffraction analysis (IPDS Stoe diffractometer, λMoKα radiation, graphite monochromator, 2θ_max = 65°, R = 0.0186 for 1378 reflections): a = 16.850(3), b = 9.729(2), and c = 9.298(2) Å; V = 1524.3(4) ų, sp. gr. Cccm, Z = 4, and ρ_calcd = 2.655 g/cm³. The numbers of Mg and Fe atoms isomorphously occupying the octahedral positions, Al and Be atoms in tetrahedra, and Na and Ca atoms and H₂O molecules in the framework cavities are refined. The hydrogen atom is localized and its coordinates and thermal displacement parameters are refined. Based on the comparative crystallochemical analysis of cordierites from different locations and origins, the regularities relating the unit-cell parameters b and c and the distortion index to the features of the chemical composition of the minerals under study are shown.     

Effects of the Electron—Electron Interaction in the Magneto-Absorption Spectra of HgTe/CdHgTe Quantum Wells with an Inverted Band Structure

JETP Letters - Magneto-absorption in HgTe/CdHgTe quantum wells with an inverted band structure in magnetic fields up to 30 T has been studied. It has been shown that the positions of...