Kinetics of the New Phase Nucleus Growth on a Magnet near the Curie Point

1990 ◽  
Vol 117 (1) ◽  
pp. 61-65
Author(s):  
Yu. Devyatko ◽  
V. N. Tronin ◽  
V. I. Troyan
1990 ◽  
pp. 61-66
Author(s):  
Yu. Devyatko ◽  
V. N. Tronin ◽  
V. I. Troyan

2012 ◽  
Vol 26 (28) ◽  
pp. 1250183 ◽  
Author(s):  
VLADIMIR NAZAROV ◽  
RISHAT SHAFEEV

Theoretically, with the aid of a soliton model, the evolution of a new-phase nucleus near the first-order spin-reorientation phase transition in magnets has been investigated in an external magnetic field. The influence of an external field and one-dimensional defects of magnetic anisotropy on the dynamics of such nucleus has been demonstrated. The conditions for the localization of the new-phase nucleus in the region of the magnetic anisotropy defect and for its escape from the defect have been determined. The values of the critical fields which bring about the sample magnetization reversal have been identified and estimated.


2019 ◽  
Vol 1 (1) ◽  
pp. 1
Author(s):  
Yu.V. Yudin ◽  
M.V. Maisuradze ◽  
A.A. Kuklina ◽  
P.D. Lebedev

An algorithm was developed for the simulation of a phase transition in solid state whichmakes it possible to obtain the kinetic curves of transformation under different initialconditions (the number and arrangement of new phase nuclei, the distance betweenthe nearest nuclei). The simulation results were analyzed using the Kolmogorov-Johnson-Mehl-Avrami equation and the corresponding coefficients were determined.The correlation between the simulation results and the experimental kinetics of theaustenite isothermal transformation in alloyed steels was shown.


Author(s):  
Ekaterina S. Guseva ◽  
Svetlana S. Popova

The effect of the magnitude of cathodic polarization and the temperature of a solution of lanthanum salicylate on the kinetics of the formation of elecrode LаyMn1-yO2 has been described. It has been established that two phases are formed on the electrode: the phase of the solid solution of the introduced lanthanum in MnO2 at potentials negative -2.5V turns into a new phase LаyMn1-yO2; last on the curve Eб/т-Ек the potential delay characteristic of the process of forming a new phase with an independent crystal lattice corresponds. Thus, to obtain a time-stable phase of the introduction of lanthanum into the structure of the electrode LаyMn1-yO2 the potential range from –2.9 V to –2.5 V can be recommended. The influence of the solution temperature on the kinetic characteristics of the process is ambiguous and is associated with a change in the degree of disorder in the structure of the forming phase at the boundary MnO2 electrode/solution (La3+), which hampers diffusion of ions La3+ into the electrode and leads to a decrease in ion concentration La3+, involved in the act of electrochemical introduction and, accordingly, to a decrease in the value of i (0). At temperatures above 10 °С the structure is stabilized and the characteristics (k, i (0)) increase. The composition of the formed phases is determined LixMnO2, LayMn1-yO2, LixLayMn1-yO2, current-free chronopotentiometry method calculated on the basis of equilibrium potentials Ep of these phases with pulsed galvanostatic polarization mode. Stability formed in the structure of MnO2 electrode chemical compounds of lanthanum was established. The activating effect of fullerene additives С60 composed of modified lanthanum LаyMn1-yO2 electrodes due to the high redox activity and the unusual structure of the molecules С60. Data on the effect of modified MnO2 electrodes on their potentials in an open circuit and during polarization in the working solution are in good agreement in terms of increasing the capacity of lithium with the results of cycling LiхMnO2, LiхLayMn1-yO2, LiхLayMn1-yO2-σ(C60)n in galvanostatic mode. The results of galvanostatic cycling showed that the discharge capacity of the electrodes increases in the series: LixMnO2 > LixLayMn1-yO2 > LiхLayMn1-yO2-σ(C60)n. With the help of cyclic chronovamperometry a good reversibility for LiхLayMn1-yO2-σ(C60)n electrode was established.


2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
V. V. Nietz

The fundamentals of precessing ball solitons (PBS), arising as a result of the energy fluctuations during spin-flop phase transition induced by a magnetic field in antiferromagnets with uniaxial anisotropy, are presented. The PBS conditions exist within a wide range of amplitudes and energies, including negative energies relative to an initial condition. For each value of the magnetic field, there exists a precession frequency for which a curve of PBS energy passes through a zero value (in bifurcation point), and hence, in the vicinity of this point the PBS originate with the highest probability. The characteristics of PBS, including the time dependences of configuration, energy, and precession frequency, are considered. As a result of dissipation, the PBS transform into the macroscopic domains of a new phase.


Author(s):  
Evgeniy S. Slivchenko ◽  
Vadim N. Isaev ◽  
Alexander P. Samarskiy ◽  
Valerian N. Blinichev

Theoretical and experimental evaluations of crystallization systems solutions stability to overcooling were summarized. The general regulariries of the kinetics of the crystallization process are discussed from the standpoint of the classical theory of the formation and growth of new-phase particles. During the analysis of the process of periodic homogeneous crystallization kinetic diagram, three characteristic periods were revealed: the period of resistance to supercooling, the period of crystal growth, and the period of recrystallization. The nature of the processes determining the duration of the characteristic periods has been established. The applicability of the mathematical apparatus of the new phase formation classical theory for calculating the basic and particular functionals of the crystallization system is substantiated. Relations are given that make it possible to calculate the main and particular functionals of the crystallization system stability for supercooling. The analysis of crystallization system category influence on the magnitude of limit supercooling and periodic homogenous crystallization induction period extreme was made. Parameters of the resistance to supercooling of supersaturated aqueous solutions of inorganic and organic substances certain classes under periodic homogeneous crystallization are presented. Conclusions are drawn regarding the position of the main and particular functionals extrema of the crystallization system. The correctness of the conclusions is confirmed by an analysis of the experimental data on the crystallization kinetics of a number of inorganic and organic substances from aqueous and aqueous-organic solvents. On the example of periodic homogeneous crystallization process of the vitamin B1 thiamin bromide from the water-ethanol solution, a complete series of the crystallization system main and particular functionals extremum positions the are constructed. The regularities of the influence of the organic component concentration in a binary solvent on the stability functionals of the crystallization system are noted.Forcitation:Slivchenko E.S., Samarskiy A.P., Isaev V.N., Blinichev V.N. Stability of supercooling solutions of crystallization systems in classical theory of new phase formation. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 5. P. 88-93.


2008 ◽  
Vol 62 (3) ◽  
pp. 114-118
Author(s):  
Ljiljana Matovic ◽  
Snezana Milovanovic ◽  
Milica Drvendzija ◽  
Jasmina Grbovic-Novakovic

To study the influence of 3d transition metal addition on desorption kinetics of MgH2 ball milling of MgH2-Co blends was performed under Ar. Microstructural and morphological characterization, performed by XRD and SEM, show a huge correlation with thermal stability and hydrogen desorption properties investigated by DSC. A complex desorption behavior is correlated with the dispersion of the metal additive particles on hydride matrix. The activation energy for H2 desorption from MgH2-Co composite was calculated from both non-isothermal and isothermal methods to be 130 kJ/mol which means that mutually diffusion and nucleation and growth of new phase control the dehydration process.


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