The phenomenon of relay race molecular transfer of the amount of motion and its relationship with the diffusion phenomenon

The very fact of molecular transfer of the amount of motion, including in an ideal gas in an equilibrium state, has long been well known. However, this fact is still not realized as a physical phenomenon of transfer, equivalent to such transfer phenomena as diffusion, thermal conductivity and viscosity. The key concept used in this paper when describing the phenomenon of relay race molecular transfer of the amount of motion is the concept - “molecular relay race type of motion”. A molecular relay race model of an ideal gas in an equilibrium state is proposed, as well as a molecular relay race model of a mixture of two ideal gases at constant temperature and pressure. It is shown that the value of the velocity modulus of diffusion flows is one of the physical characteristics of the mixture as a whole. It is also shown that the total density of the substance carried by the diffusion flows is many orders of magnitude less than the total density of the inhomogeneous multicomponent mixture.

Three-dimensional exact solutions of the diffusion equation

При помощи метода быстрых разложений решается задача диффузии в параллелепипеде с граничными условиями 1-го рода и внутренним источником вещества, зависящим от координат точек параллелепипеда. Получено в общем виде решение, содержащее свободные параметры, с помощью которых можно получить множество новых точных решений с различными свойствами. Показан пример построения точного решения для случая внутреннего источника переменного только по оси OZ . Приведен анализ особенностей диффузионных потоков в параллелепипеде с указанным внутреннем источником. Получено, что концентрация вещества в центре параллелепипеда равна сумме среднеарифметического значения концентраций вещества в его вершинах и амплитуды внутреннего источника умноженного на величину The authors solve the problem of diffusion in a parallelepiped-shaped body with boundary conditions of the 1st kind and an internal source of substance, depending on the parallelepiped points coordinates with the fast expansions method. The proposed exact solution in general form contains free parameters, which can be used to obtain many new exact solutions with different properties. An example of constructing an exact solution with a variable internal source depending on one coordinate z is shown in the work. An analysis of the features of diffusion flows in a parallelepiped with the indicated internal source is given. It was found that the concentration of a substance in the center of a parallelepiped is equal to the sum of the arithmetic mean of the concentration of a substance at its vertices and the amplitude of the internal source multiplied by the value

Theoretical description of the ligand function for ionoselective electrodes reversible to metal anion complexes. 3. Modeling of the electrode response in ligand and foreign ions solutions using the multi-species approach model

A description for the ligand function of the tetrathiocyanatozincate selective electrode, has been proposed, using a multi-species approach model. This model takes into account simultaneous phase-boundary, diffusion-controlled, processes of ion exchange between tetrathiocyanatozincate, thyocyanate and foreign ions unable to form zinc complexes, as well as distribution of the neutral zinc complex between phases, partial decomposition of quaternary ammonium tetrathiocyanatozincate salt and stepwise complex formation processes in water phase. The model is based on solving the system of equations describing several interphase and intraphase equilibria, assuming that diffusion flows of all membrane and solution components at the phase boundary are stationary. It provides the adequate description of tetrathiocyanatozincate selective electrode in solutions of the ligand, foreign ions and mixed solutions of the above, and predicts the effect of zinc chloride concentration in the sample solution upon electrode function slopes, lower detection limits and selectivity coefficients.

Microscopic kinetics of isothermal sintering of Fe-20 % (mаs.) Mo alloy

Purpose of work. To investigate the features of microscopic kinetics of peritectoid transformation in Fe-Mo system alloys in an isothermal mode. Experimental part. Microscopic analysis of samples on light (Jenaphot 2000, K. Zeiss) and scanning electron (REM 106I, Selmi) microscopes, X-ray spectral microanalysis of the component’s concentrations distribution between the phases, X-ray phase analysis (Rigaku Ultima IV diffractometer). Results. Microstructure changes, phase composition and crystal lattices parameters of the phase constituents of the powder alloy during sintering at 920 °C were investigated. Variation in the phase constituents mass fraction during 7 hours of the isothermal exposure is analyzed. The formation of anomalous diffusion porosity at the beginning of the process, the nonmonotonic change in the phase constituents fraction and formation of intermediate phases with an unstable component’s concentration are the main features of the microscopic kinetics. The sintering mechanism is proposed. Scientific novelty. A local peritectoid transformation existence at the Fe/Mo interface was established by analyzing the local diffusion flows of components atoms. This transformation occurs upon isothermal supply of Mo atoms with the formation of a cooperative peritectoid structural constituents according to the α- Fe + Mo → α + μ scheme with residual Mo crystals. Formulation of the problem. This work aims to clarify the phenomenological theory of peritectoid transformation during isothermal α-Fe grains enrichment with molybdenum by studying the features of microscopic kinetics in the Fe-Mo system alloys. Practical value. Peritectoid (α + μ) with branched phase соnstituents of cooperative genesis forms a developed system of local diffusion flows of Mo atoms in α -Fe. This increases the molybdenum peritectoid transformation rate at a relatively low sintering temperature for these alloys and reduces the energy consumption in the technological process.

Two-Stage Seebeck Effect in Charged Colloidal Suspensions

We discuss the peculiarities of the Seebeck effect in stabilized electrolytes containing the colloidal particles. Its unusual feature is the two stage character, with the linear increase of differential thermopower as the function of colloidal particles concentration n⊙ during the first stage (“initial state”) and dramatic drop of it at small n⊙ during the second one (“steady state”). We show that the properties of the initial state are governed by the thermo-diffusion flows of the mobile ions of the stabilizing electrolyte medium itself and how the colloidal particles participate in the formation of the electric field in the bulk of the suspension. In its turn, we attribute the specifics of the steady state thermoelectric effect the massive colloidal particles undergoing slow thermal diffusion and the break down of their electro-neutrality in the vicinity of electrodes.

Euler-Bernoulli cantilever beam bending considering the inner diffusion flows finite propagation speed

Исследуются нестационарные колебания балки Эйлера-Бернулли с учетом массопереноса. Используется модель упругой диффузии для многокомпонентных сред. Для получения решения задачи используются вариационный принцип Даламбера и метод эквивалентный граничных условий. Unsteady vibrations of the Euler-Bernoulli beam are studied taking into account mass transfer. The model of elastic diffusion for multicomponent media is used. To obtain a solution to the problem, the d’Alembert variational principle and the equivalent boundary conditions method are used.

Calculation of Diffusion Flows for the Formation of Phases in Alloys Iron-Carbon-Alloying Element

The method of calculation of diffusion flows under phase transformations in alloys iron - carbon - alloying element using the principles of nonequilibrium thermodynamics are developed. The expressions for calculation of cross-factors, motive forces and flows in the Onzager equations for a two-phase thermodynamic system, and an example of using the developed method are given.