Mathematical model of phase-formation processes in a binary mixture of Ti and Al powders in the regime of a nonadiabatic thermal explosion

Корчагин

Smirnov

et al. 2010

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Specific features of heating of a mechanically activated 3Ni + Al mixture during synthesis in the thermal explosion mode are considered. Based on the authors' criterion of the minimum curvature of the heating rate logarithm as a function of inverse temperature, the activation energies of the synthesis process in the above-mentioned system are determined and the temperature intervals of the Arrhenius dependence and selfdeceleration segments on thermograms are found. A kinetic function structure analysis shows that synthesis follows the laws of homogeneous kinetics with the reaction order close to unity. The calculated activation energies are anomalously low, as compared with conventional self-propagating high-temperature synthesis in this system.

Section: Introductionmentioning

confidence: 99%

Macrokinetics of Solid-Phase Synthesis of an Activated 3Ni + Al Mixture in the Thermal Explosion Mode

Корчагин

Smirnov

et al. 2010

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“…Though advanced methods of computer modeling allow considering much more complicated problems (with allowance for diffusion processes, based on state diagrams of binary systems [3][4][5]), methods that involve kinetic functions are still used in combustion problems. Definition of an effective heat-release function in the heat conduction or thermal balance equation simplifies modeling combustion theory problems.…”

Section: Introductionmentioning

confidence: 99%

Specific Features of Self-Heating in Systems with a Logarithmic Law of Deceleration

2010

A qualitative analysis of structural types of phase trajectories and corresponding thermograms with various values of the Semenov and Todes criteria for systems with intense self-deceleration is performed. A rigorous criterion of degeneration of the thermal explosion is found. Physical mechanisms of various regimes of self-heating processes are analyzed. An approximate functional dependence of the critical value of the Semenov parameter on the self-deceleration parameter is obtained, and the limits of its applicability are determined.

“…One of the basic problems of technological combustion is a correct choice of synthesis regimes for obtaining products with required compositions and properties. For this reason, the interest in self-propagating high-temperature synthesis (SHS) in the thermal explosion regime [2,3] has increased, because the process in this regime can be controlled by changing the ambient conditions [4,5]. From this viewpoint, an important aspect of technological combustion is obtaining a singlephase product of synthesis in the entire volume of the 1 Polzunov Altai State Technical University, Barnaul 656038; vyfilimonov@rambler.ru.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of phase-formation processes during self-propagating high-temperature synthesis in the thermal explosion regime

Кошелев

2008

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Specific features of formation of temperature and concentration fields during selfpropagating high-temperature synthesis in the thermal explosion regime in a cylindrical reactor are studied by methods of mathematical modeling. The calculations are performed with allowance for melting of one (chemically active) component in the approximation with the high-melting component being non-soluble in the melt of the low-melting component. It is shown that the conditions of complete conversion of the original components in the volume of the reacting mixture depend on relations between the Biot criterion of the system, the ambient temperature, and the thermal effect of the reaction. After the thermal explosion, which occurs when the melting front reaches the geometric center of the reactor, a front of complete conversion is formed. This front moves from the cylinder centerline to the periphery with a gradually decreasing velocity. The diagram of the critical values of the Biot criterion at which the components burn down completely in the entire reaction volume is calculated.