Morphogenesis of distributions of microparticles by dimensions in the coarsening of dispersed systems

For a wide class of dispersed systems, a basis is given for the possibility of a complete theoretical analysis of their evolution, owing to Ostwald coagulation of microparticles. Theoretical solutions are obtained to describe distributions of microparticles by dimensions with positive and negative asymmetry, kinetic dependences, and lifetimes of the microparticles of any given dimension, taking into account various mechanisms of their reactive interaction with the substance of the medium. In an example of change of the morphological indicators of experimental histograms of microparticles of Al₃Mg₂ under isothermal heating of the aluminum-magnesium alloy, their correspondence is shown to the nature of the transformation of the theoretical distribution functions.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 53–58, December, 1990.     

On the technique for structural analysis of solid dispersed systems

Analytical relationships are proposed for performing a system analysis of structural coarsening of microparticles of a dispersed phase. For this purpose, a method is developed for revealing the similarities and differences between characteristics of the experimental histogram and the theoretical distribution of microparticles over sizes. This approach to the identification of distributions makes it possible to establish a correlation between the specific features of the transformation of the experimental distributions (histograms) and intrasystem processes.     

Response function of coarsening systems

We calculate analytically the conditions that establish the number of bound states in finite superlattices as a function of the depth, width and separation of the wells. We consider a lattice of -wells and a set of rectangular wells. For this latter case, we show how for finite systems the energy levels already group together in bands separated by gaps. Received 24 April 1998     

Heterogeneous dynamics of coarsening systems

We show by means of experiments, theory, and simulations that the slow dynamics of coarsening systems displays dynamic heterogeneity similar to that observed in glass-forming systems. We measure dynamic heterogeneity via novel multipoint functions which quantify the emergence of dynamic, as opposed to static, correlations of fluctuations. Experiments are performed on a coarsening foam using time-resolved correlation, a recently introduced light scattering method. Theoretically we study the Ising model, and present exact results in one dimension, and numerical results in two dimensions. For all systems the same dynamic scaling of fluctuations with domain size is observed.     

Analysis of the structural interaction of electrically active heterogeneous finely dispersed systems at the interfaces between the solid and liquid phases

Strong electrical forces have been revealed in electrically active heterogeneous finely dispersed systems at the interfaces between the solid and liquid phases. It has been established that these forces give rise to gradients of the potential of an internal self-electric field that can provide circulation of electric currents in the systems under investigation. It has been found that, in these systems, there arises a double electric layer that represents a new structuring phase, which is characteristic of electrically active systems only. The mechanism of formation of a double electric layer includes electrocontact interaction between the surfaces of two heterogeneous liquid and solid polar dielectrics.     

Analysis and interpretation of data on the evolutionary development of dispersed systems

We discuss questions concerning the application of systems analysis to alloys containing a dispersed phase. The development of such dispersed systems takes on the form of self-development of an ensemble of polydispersed microparticles distributed in the matrix phase, which we can evaluate from data on analysis of the transformation of their size distributions over time. For the example of vanadium steel containing dispersed carbide phase (cementite + VC carbides), we illustrate the procedure for establishing a correlation between the indices of the transformation of the experimental histograms over time for enlargement of the Fe₃C microparticles in the alloy and the internal processes (within the volume) causing such transformations, and also the interpretation of the data obtained and the characteristic features of application of the developed method to a system analysis of the evolution of microparticles of dispersed systems.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 38–43, January, 1995.     

Slow coarsening in a class of driven systems

The coarsening process in a class of driven systems is studied. These systems have previously been shown to exhibit phase separation and slow coarsening in one dimension. We consider generalizations of this class of models to higher dimensions. In particular we study a system of three types of particles that diffuse under local conserving dynamics in two dimensions. Arguments and numerical studies are presented indicating that the coarsening process in any number of dimensions is logarithmically slow in time. A key feature of this behavior is that the interfaces separating the various growing domains are macroscopically smooth (well approximated by a Fermi function). This implies that the coarsening mechanism in one dimension is readily extendible to higher dimensions. Received 3 April 2000     

Effective medium in dispersed systems

A structural analysis of effective medium formed by dispersed systems from the viewpoint of flux modification at large dispersions is presented. The effective medium coefficient is investigated for its parametric dependence and the effective properties are estimated through this dependence. This estimation covers all highly dispersed two-phase systems including the effect of container.     

Optical properties of Cu dispersed in solid Xe

We have studied the optical properties of copper dispersed in a solid noble gas matrix in the neighbourhood of the metal-insulator transition.     

Domain growth and aging scaling in coarsening disordered systems

We explore the electronic and transport properties out of a biased multilayer hexagonal boron nitride (h-BN) by first-principles calculations. The band gaps of multilayer h-BN decrease almost linearly with increasing perpendicular electric field, irrespective of the layer number N and stacking manner. The critical electric filed (E ₀) required to close the band gap decreases with the increasing N and can be approximated by E ₀ = 3.2 / (N ? 1) (eV). We provide a quantum transport simulation of a dual-gated 4-layer h-BN with graphene electrodes. The transmission gap in this device can be effectively reduced by double gates, and a high on-off ratio of 3000 is obtained with relatively low voltage. This renders biased MLh-BN a promising channel in field effect transistor fabrication.     

Optimalizing principle of pneumatic transfer of dispersed solid materials

The optimalizing physical and mechanical conditions of the pneumatic method of transfer of dispersed solid materials, conforming to the regular piston regime of motion of dispersed solid materials in the transporting pipeline are discussed. The investigation of the flow of the compressible heterogeneous medium in the pipeline, under the piston condition of motion of the mass being transported, is presented in unidimensional statement of the problem. Specific data obtained on the electronic computer indicate the existence of an important expansion of technical possibilities in the high-pressure transport in long range transportation and its efficiency.Translated from Izvestiya VUZ, Fizika, No. 3, pp. 17–22, March, 1973.     

Low-viscosity flow of a solid dispersed medium in the Bridgman effect

The quasi-fluid flow of microdispersed solids at the stage of rapid dynamic high-pressure loading under the conditions of the Bridgman effect is considered in terms of the hydrodynamic approach. Under these conditions, the effective dynamic viscosity of the rapidly flowing solid medium is estimated to be η = 1–3 Pa s, which is typical of only low-viscous fluids. The time of dynamic loading at the stage of rapid compression in the Bridgman effect is estimated as t = (3–6) × 10⁻⁶ s, which agrees well with the available experimental data.     

Kinetic faceting and anomalous coarsening in elastically inhomogeneous multiphase systems

With a view of finding a route toward microstructural stability in alloys, we numerically study the impact of elastic inhomogeneities on the growth of inclusions in multiphase systems. We show that growth can proceed either continuously at rough interfaces, or in a layer-by-layer fashion following an elastically induced kinetic faceting process. In the former case, the chemical potential of the inclusions is a smooth function of size, while in the latter case, elasticity increases the barrier for nucleation of new terraces on the facets, leading to an oscillatory behavior of the chemical potential and hence a strong resistance against coarsening, opening up the possibility to stabilize the structure.     

On the connection between off-equilibrium response and statics in non disordered coarsening systems

The connection between the out of equilibrium linear response function and static properties established by Franz, Mezard, Parisi and Peliti for slowly relaxing systems is analyzed in the context of phase ordering processes. Separating the response in the bulk of domains from interface response, we find that in order for the connection to hold the interface contribution must be asymptotically negligible. How fast this happens depends on the competition between interface curvature and the perturbing external field in driving domain growth. This competition depends on space dimensionality and there exists a critical value d _c = 3 below which the interface response becomes increasingly important eventually invalidating the connection between statics and dynamics as the limit d = 1 is reached. This mechanism is analyzed numerically for the Ising model with d ranging from 1 to 4 and analytically for a continuous spin model with arbitrary dimensionality. Received 10 July 2001     

界面润湿性及固相体积分数对颗粒粗化动力学影响的相场法研究

利用多相场模型模拟了液-固两相体系中固相颗粒的粗化过程, 分析了界面润湿性及固相体积分数对粗化指数、粗化速率及颗粒尺寸分布的影响.结果表明, 不同固相体积分数下粗化指数基本不变, 但粗化速率常数及尺寸分布与固相体积分数及界面润湿性密切相关.在完全润湿条件下, 随着固相体积分数的增加, 粗化速率常数逐渐增大; 而非完全润湿条件下, 随着固相体积分数的增加, 粗化速率常数增大速度变缓, 且当润湿性较低、 固相分数较大时, 粗化速率常数还将随体积分数的增加而下降. 此外, 模拟结果表明各种润湿条件下颗粒的尺寸分布均随着固相分数增加而变宽, 分布峰值降低, 但非完全润湿条件下峰值下降变缓.模拟结果为理解不同实验观测结果之间的分歧提供了依据. 关键词： 粗化 相转变 相场法 润湿性