Analysis of the Influence of Modes of Plasmachemical Synthesis and Precursor Evaporation on Geometric Characteristics of Ceramic Powders Produced

Mathematical model of evolution of a liquid precursor droplet in the process of plasma-chemical transformations for production of micro- and nano-structured ceramic powders on the basis of metal oxides is described. A criterion of production of particles with different morphology is determined. The results of numerical analysis are given

Verification of model of calculation of intra-chamber parameters in hybrid solid-propellant rocket engines

On the basis of obtained analytical estimate of characteristics of hybrid solid-propellant rocket engine verification of earlier developed physical and mathematical model of processes in a hybrid solid-propellant rocket engine for quasi-steady-state flow regime was performed. Comparative analysis of calculated and analytical data indicated satisfactory comparability of simulation results

Analytical estimation of particle shape formation parameters in a plasma-chemical reactor

Analytical estimation of particle shape formation parameters in a plasma-chemical reactor implementing the process of thermochemical decomposition of liquid droplet agents (precursors) in the flow of a hightemperature gaseous heat-transfer medium was obtained. The basic factor which determines the process is the increase of concentration of a dissolved salt precursor component at the surface of a liquid particle due to solvent evaporation. According to the physical concept of the method of integral balance the diffusion process of concentration change is divided into two stages: the first stage is when the size of gradient layer does not reach the center of a spherical droplet and the second stage when the concentration at the center of a liquid droplet begins to change. The solutions for concentration fields were found for each stage using the method of integral balance taking into account the formation of salt precipitate when the concentration at the surface of the droplet reaches certain equilibrium value. The results of estimation of the influence of various reactor operation parameters and characteristics of initial solution (precursor) on the morphology of particles formed - mass fraction and localization of salt precipitate for various levels of evaporation

Analytical estimation of particle shape formation parameters in a plasma-chemical reactor

Analytical estimation of particle shape formation parameters in a plasma-chemical reactor implementing the process of thermochemical decomposition of liquid droplet agents (precursors) in the flow of a hightemperature gaseous heat-transfer medium was obtained. The basic factor which determines the process is the increase of concentration of a dissolved salt precursor component at the surface of a liquid particle due to solvent evaporation. According to the physical concept of the method of integral balance the diffusion process of concentration change is divided into two stages: the first stage is when the size of gradient layer does not reach the center of a spherical droplet and the second stage when the concentration at the center of a liquid droplet begins to change. The solutions for concentration fields were found for each stage using the method of integral balance taking into account the formation of salt precipitate when the concentration at the surface of the droplet reaches certain equilibrium value. The results of estimation of the influence of various reactor operation parameters and characteristics of initial solution (precursor) on the morphology of particles formed - mass fraction and localization of salt precipitate for various levels of evaporation

Energy and propulsion optimization of solid-propellant grain of a hybrid power device

A method of distribution of an additional solid-phase component (oxidizer) providing uniformity of grain burning for the purpose of evaluation and optimization of energy and propulsion parameters of hybrid solid-propellant motor is proposed in the paper

On the possibility to fabricate ceramics using fused deposition modeling

The paper presents a uniquely designed device that enables controlled manufacturing of semi-fabricated products from thermoplastic ceramic suspensions by fused deposition modeling. Sintering of the products yields ceramics with high strength and hardness. We use ceramic aluminum oxide (Al2O3) as an example to prove that additive ceramic structures can be produced without noticeable boundaries between layers of the material

Chemical heterogeneity as a factor of improving the strength of steels manufactured by selective laser melting technology

The aim of this paper was to establish the causes of the heterogeneity of the chemical composition of the metal obtained by the LC technology. The powdered raw material was made from a monolithic alloy, which was fused by the SLM, the initial raw material was a laboratory melting metal of a low-carbon chromium-manganese-nickel composition based on iron. To determine the distribution pattern of alloying chemical elements in the resulting powder, electron-microscopic images of thin sections were combined with X-ray analysis data on the cross-sections of the powder particles. As a result, it was found that transition (Mn, Ni) and heavy (Mo) metals are uniformly distributed over the powder particle cross-sections, and the mass fraction of silicon (Si) is uneven: in the center of the particles, it is several times larger in some cases. The revealed feature in the distribution of silicon is supposedly due to the formation of various forms of SiO4 upon the cooling of the formed particles. The internal structure of the manufactured powder is represented by the martensitic structure of stack morphology. After laser fusion, etched thin sections revealed traces of segregation heterogeneity in the form of a grid with cells of ~ 200 μm

β-Polymorph of phenazepam: a powder study

The title compound [systematic name: 7-bromo-5-(2-chloro­phen­yl)-1H-1,4-benzodiazepin-2(3H)-one] (β-polymorph), C15H10BrClN2O, has been obtained via cryomodification of the known α-polymorph of phenazepam [Karapetyan et al. (1979 ▶). Bioorg. Khim. 5, 1684–1690]. In both polymorphs, the mol­ecules, which differ only in the dihedral angles between the aromatic rings [75.4 (2)° and 86.2 (3)° in the α- and β-polymorphs, respectively], are linked into centrosymmetric dimers via N—H⋯O hydrogen bonds. In the crystal structure of the β-polymorph, weak inter­molecular C—H⋯O hydrogen bonds further link these dimers into layers parallel to bc plane

Nonsteady condensation and evaporation waves

We study motion of a phase transition front at a constant temperature between stable and metastable states in fluids with the universal Van der Waals equation of state (which is valid sufficiently close to the fluid's critical point). We focus on a case of relatively large metastability and low viscosity, when it can be shown analytically that no steadily moving phase-transition front exists. Numerically simulating a system of the one-dimensional Navier-Stokes and continuity equations, we find that, in this case, the nonsteady phase-transition front emits acoustic shocks in forward and backward directions. Through this mechanism, the front drops its velocity and eventually comes to a halt. The acoustic shock wave may shuttle, bouncing elastically from the system's edge and strongly inelastically from the phase transition front. Nonsteady rarefaction shock waves appear in the shuttle process, despite the fact that the model does not admit steady rarefaction waves propagating between stationary states. If the viscosity is below a certain threshold, an instability sets in, driving the system into a turbulent state. This work was supported by the Japan Society for Promotion of Science.Comment: revtex text file and four eps files with figures. Physical Review Letters, in pres

The Intellectual and Educational Resources as an Institutional Factor of Innovative Economy Formation

Quality of an innovation and its efficiency depend in a decisive way on quality and degree of novelty of the knowledge that is been its basis. New knowledge, such as the discovery of electricity, the managed nuclear reaction, the creation of electronic computers, the mean transition of mankind to the qualitatively new step in development. The new knowledge is equivalent to new economy of knowledge to power, material and labor costs, directly allowing replacing them with knowledge how it is possible to gain the same or bigger effect at the same or smaller costs of energy, materials and live human labor. In the economy of knowledge, the corporate and national wealth depends on accumulation and use of the knowledge making the main cost of intellectual capital. Despite a set of determinations and classifications of intellectual capital, most of the authors adheres to that point of view, that the intellectual capital includes human capital and the structural capital. DOI: 10.5901/mjss.2015.v6n3s6p28