Methods for MgSiN<Subscript>2</Subscript> synthesis

Direct synthesis of MgSiN₂ from simple substances was performed in a flow-through system. The sequence of transformations that occur on heating mixed magnesium and silicon powders in flow of nitrogen was determined by X-ray phase analysis.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 8, 2004, pp. 1241–1244.Original Russian Text Copyright © 2004 by Grekov, Chernovets.     

Synthesis of α-eucryptite by the sol-gel method

New method is reported for synthesis of α-eucryptite LiAlSiO₄ whose framwork structure has voids that enable its doping with lanthanides. The optical parameters of this orthosilicate and results of introduction of europium ions into its composition to create a phosphor were studied.     

A film coating on a rough surface of an elastic body

A solution of the plane problem of the theory of elasticity for a film–substrate composite is solved by a perturbation method for a substrate with a rough surface. An algorithm for calculating any approximation, which ultimately leads to the solution of the same Fredholm equation of the second kind, is given. Formulae for calculating the right-hand side of this equation, which depends on all the preceding approximations, are derived. An exact solution of the integral equation in the form of Fourier series, whose coefficients are expressed in quadratures, is given in the case of a substrate with a periodically curved surface. The stresses on the flat surface of the film and on the interfacial surface are found in a first approximation as functions of the form of bending of the surface, the mean thickness of the film and the ratio of Young's moduli of the film and the substrate. It is shown, in particular, that the greatest stress concentration on the film surface occures on a protrusion of the softer substrate. ©2013     

High-order compact schemes for second-order ordinary differential equations with singular coefficients

Homogeneous three-point finite-difference schemes of arbitrary order of accuracy for a second-order Dirichlet problem with generalized coefficients and generalized right-hand side are constructed and validated. Bibliography: 8 titles. Translated fromObchyslyuval’na ta Prykladna Matematyka, No. 77, 1993, pp. 55–60.     

Quantum-chemical investigation of thermal transformations of tris(hydroxymethyl)phosphine

In keeping with the calculations of thermodynamic characteristics of possible transformations of tris(hydroxymethyl)phosphine in the framework of DFT-approach using hybrid exchange-correlation functional B3LYP with the basis 6–311++G** the probability of transformation of tris(hydroxymethyl)phosphine at the temperature below 350 K into methylbis(hydroxymethyl)phosphine oxide is higher than the conversion into methyl(hydroxymethyl)phosphine oxide, and at the temperature over 350 K the trend is opposite. The probability of the formation of a heterocyclic dimer at the temperature over 300 K is somewhat lower and of bis(hydroxymethyl)phosphine in the temperature range 250–550 K is significantly lower.     

Synthesis and study of polyurethanes and polyurea urethanes based on the diamino derivatives of bis-1,3,4-oxadiazole

Polyurethanes were synthesized by condensation of diamino derivates of bis-1,3,4-oxadiazole with chloroformates, and polyurea urethanes were synthesized from diamino derivaties of bis-1,3,4-oxadiazole, diisocyanates, and ethylene glycol in a solution of dimethylformamide. Certain properties of these compounds were studied.     

Difference schemes for fourth-order one-dimensional equations with nonlinear boundary condition

A difference scheme is constructed for a boundary-value problem for a one-dimensional biharmonic equation with nonlinear boundary condition. Under the hypothesis that the exact solution of the problem belongs to the Sobolev space W ₂ ^k(),k [2, 4], in the lattice norm L ₂ (), an estimate is obtained of the precision of the difference scheme to O(h^k–1,5).Translated fromVychislitel'naya i Prikladnaya Matematika, No. 69, pp. 43–50, 1989.     

Application of the Nanofiltration Method in Systems for Recycling of Washing Water in Photographic Development of Motion-Picture Films

The possibility of using the nanofiltration method for purification of washing water in photographic development of professional motion-picture films is analyzed. Characteristics of domestic membranes, OPMN-K of nanofiltration type and OFAM-KN of low-pressure reverse-osmosis type, obtained in desalting of silver-containing washing water, are presented.     

Mechanism of noncatalytic synthesis of tris(hydroxymethyl)phosphine. Nonempirical quantum-chemical approach

The gas-phase reaction of the synthesis of tris(hydroxymethyl)phosphine from phosphine and formaldehyde was studied using a calculation scheme based on the density functional theory with hybrid exchange-correlation functional B3LYP in the 6–311++G** basis. The reaction was shown to proceed with the participation of unstable intermediates containing three-membered ring. The transformation into final products includes opening of the three-membered ring and intramolecular proton transfer. The results can be useful at selecting catalysts and for explaining the mechanism of the catalytic reaction of tris(hydroxymethyl)phosphine synthesis.     

Equilibrium cracks in composites reinforced with unidirectional fibres

A discrete-continuum approach, proposed by Novozhilov for analysing the equilibrium states of a brittle of crack in an isotropic body, is applied to a penny-shaped crack situated in a fibre-reinforced composite perpendicular to the fibres. The structural non-uniformity of the material is taken into account by the presence of unbroken fibres in the narrow part of the crack, adjoining the edge, and the different effect of the strength properties of the fibre and matrix on the limit state of the crack. Using this model, the range of dimensions of equilibrium cracks is established and an estimate is given of the critical size of the bridged part of the crack, corresponding to the onset of catastrophic fracture. It is shown that this dimension has the same value for a penny-shaped crack and for a crack under plane strain, does not depend on the form of the load and, under the condition of its smallness, is a brittle fracture characteristic of a fibre-reinforced material. The possibility of using this fracture model for two types of ceramics is analysed on the basis of experimental data.