Crystal structure of sodium potassium zinc diphosphate NaKZnP2O7

Single crystals of NaKZnP₂O₇ were grown, and their crystal structure was determined by X-ray diffraction (space group P2₁/n, a = 12.585(5) Å, b = 7.277(5) Å, c = 7.428(5) Å, β = 90.00(5)°, Z = 4, 1916 F(hkl), R ₁ = 0.0461). The structure contains a 3D tetrahedral zinc phosphate framework with a system of intersecting channels running along the b and c axes. The sodium and potassium atoms are coordinated to six and seven oxygen atoms, respectively, and reside inside these channels; the potassium cations, which are larger than the sodium cations, are located at channel intersections.     

Synthesis and characterization of Mn-, La-Mn- and La-Ca-Mn-citrates as precursors for LaMnO<Subscript>3</Subscript> and La<Subscript>1−x</Subscript>Ca<Subscript>x</Subscript>MnO<Subscript>3</Subscript>

Mn-, LaMn- and LaCaMn-citrates were synthesized at 60–120°C in ethylene glycol medium using chlorides or nitrates as metal sources. Their composition, IR spectra and thermal decomposition were studied. Equimolar La/Mn ratio has been established in the complex, prepared from chloride solution with the same initial composition of the metals. In the isolated three-metallic complex the molar ratio of the metals deviates from the composition in the initial solution. The final products of the heating of Mn- and mixed-metal LaMn-citrates at 1000°C are phase-homogeneous Mn₃O₄ (hausmannite) and LaMnO₃ respectively. Parasitic phase(s) are observed in La_xCa_1−xMn_yO₃, produced from LaCaMn-citrate.     

Composite Fibers Based on Chitin

Composite fibers containing chitin and cellulose ethers (methyl, hydroxyethyl, and hydroxypropyl cellulose) and also chitin and polyvinylpyrrolidone were prepared. The effect of the ratio of system components and also the molecular weight of polyvinylpyrrolidone on the deformation-strength characteristics of the composite fibers and their supramolecular organization was studied.     

Electrochemical synthesis of perfluoropolyethers by the Kolbe method

Electrochemical dimerization of hexafluoropropylene oxide dimer and trimer acids on SU-2000 glassy carbon, bulk platinum, and SU-2000 electrodes modified with platinum-group metals in acetonitrile in the presence of water was studied at various concentrations of the starting substance and different degrees of neutralization of the starting acid. Also, the possibility was examined of obtaining some perfluoropolyethers in a single process by cross-condensation of several starting perfluorocarboxylic acids, followed by separation of the products by physicochemical methods.     

Effect of the humidity of honeycomb core on the strength of honeycomb structures bonded with VK-67 adhesive

Results of work on determining the effect of moisture content in a honeycomb core on the strength properties of honeycomb structures bonded with VK-67 adhesive are reported.     

Thermodynamics of water interaction with 5-vinyltetrazole copolymers with different hydrophilic-hydrophobic balances

The thermodynamics of interaction with water and the behavior of 5-vinyltetrazole copolymers with comonomers of different chemical natures and hydrophilicities in aqueous media have been studied. It has been shown that the presence of side perfluoroalkyl and disubstituted tetrazole fragments, which ensure a strong self-association of polymer chains in copolymer macromolecules, favors a greater decrease in water affinity of polymers compared to the effect of hydrophobic alkyl substituents.     

Light-induced anisotropy and gyrotropy in polarization-sensitive media

Photoinduced anisotropy and photoinduced gyrotropy were studied in polarization-sensitive photochromic glass and mordant purely yellow dye introduced into gelatin. These media, memorizing the polarization state of acting actinic light, show great promise primarily for polarization holography. It is the aim of this work to draw researchers’ attention to new findings in the field of light-induced anisotropy and holography so as to stimulate experimental and theoretical study of these phenomena and search for new polarization-sensitive media.     

Spectral processing of oblique ionospheric souniding signals using parametric methods

We, compare the efficiencies of some parametric methods of spectral evaluation in regard to the problem of analysis of ionospheric sounding signals, using model calculations and actual signal realizations. The use of Kulikov’s method for spectral processing is described. The efficiency of this method for determining the mode structure of ionospheric signals is shown. A criterion for choosing the model’s order in this method is proposed. Decesased Kazan State University, Kazan, Russia Translated from Izvestiya Vysshikh Uchebnykh Zavedennii, Radiofizika, Vol. 43, No. 7, pp. 607–616, July, 2000.