Effect of composition of precipitated calcium-copper orthophosphates on their character

A group of crystalline and amorphous calcium-copper phosphates was synthesized by the exchange reaction between sodium orthophosphate and calcium and copper(II) nitrates in solutions within a wide range of reagent ratios 0 ≤ Cu×100/(Cu + Ca) ≤ 100. Conclusions on the effect of the Cu×100/(Cu + Ca) ratio on the phase composition of the substances and on the state of chemical bonds therein were made on the basis of the results of X-ray phase analysis and IR Fourier and electronic spectroscopy.     

Thermal limitations in a rapid-fire multirail launcher powered by a pulsed magnetodhydrodynamic generator

The operation of rapid burst firing multirail electromagnetic launchers of solids is numerically simulated using unsteady two-dimensional and three-dimensional models. In the calculations, the launchers are powered by a Sakhalin pulsed magnetohydrodynamic generator. Launchers with three and five pairs of parallel rails connected in a series electrical circuit are considered. Firing sequences of different numbers of solid projectiles of different masses is modeled. It is established that the heating of the rails is one of the main factors limiting the performance of launchers under such conditions. It is shown that the rate of heating of the rails is determined by the nonuniformity of the current density distribution over the rail cross-section due to the unsteady diffusion of the magnetic field into the rails. Calculations taking into account the unsteady current density distribution in the rails of a multirail launcher show that with an appropriate of the mass of the projectiles (up to 800 g), their number in the sequence, and the material of the rails, it is possible to attain launching velocities of 1.8–2.5 km/s with moderate heating of the rails.     

Modeling of 1,2,4,5-tetrazine complexes with organic amines

Tetrazine complexes with organic ligands have been modeled. The composition and structure of the model complexes agree with experimental data. The structure and nature of the complexes affect a number of chemical reactions of 1,2,4,5-tetrazines with organic amines. It is shown that the possibility and route of nucleophilic substitution in the 3 and 6 positions of the tetrazine ring are provided by amine localization in the tetrazine complex and also by the orbital characteristics of the reagents. The route and possibility of cycloaddition reactions for tetrazines are dictated by the ability of the latter to form π-complexes with reagents and by the orbital characteristics of the complexes. The route of the cycloaddition reaction is also affected by the solvent.     

Compact Energy Storage Device for Electromagnetic Launchers of Solids

Numerical study has been performed to investigate the operating characteristics and modes of an energy storage device based on a pulsed magnetohydrodynamic generator and a step-up transformer with a stored energy of 25 and 50 MJ and a secondary winding current of 250 kA at the final stage of operation. The operating parameters of such storage devices with rail launchers operating in the mode of rapid-fire launching of several projectiles were calculated.     

Amorphous calcium barium monophosphate and its dehydration in air at room temperature

The change in the state of chemical bonds during dehydration of amorphous calcium barium monophosphate was studied. The monophosphate was obtained by precipitation from an aqueous phosphate solution under the action of a binary solution containing simultaneously calcium and barium chlorides in the atomic ratio Ba/Ca ～0.2.     

Calcium Phosphates Coprecipitated from Aqueous Solutions of Sodium Monophosphate and Diphosphate

Calcium phosphate compounds obtained by coprecipitation from sodium monophosphate and diphosphate aqueous solutions under the action of calcium chloride are described.     

Precipitated calcium phosphatesilicates and their dehydration in air at room temperature

By exchange reaction in the aqueous solutions between sodium phosphatesilicates and calcium chloride is obtained a group of the crystalline and amorphous substances, which contain up to 80 wt % of water. Dehydration of amorphous calcium phosphatesilicates at room temperature is studied.     

A New Generation Pulsed MHD Generator

Doklady Physics - The results of calculation and theoretical investigation for the creation of a powerful (~600 MW) pulsed MHD generator on the combustion products from solid (powder)...     

The energy dependence of the {111} and {100} tilt grain boundaries on disorientation angle in Ni<Subscript>3</Subscript>Al

Dependence of the energy of {111} and {100} boundaries on tilt angle θ is investigated by the molecular dynamics method using intermetallic Ni₃Al as an example. It is shown that the energy (per single grain dislocation) of grain boundaries in the {111} planes is higher than that of the grains located in the {100} planes. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 33–35, November, 2007.