scholarly journals SURFACE LAYER THICKNESS AND ANISOTROPY OF THE SURFACE ENERGY OF CUBIC RUTHENIUM CRYSTALS

Author(s):  
Виктор Михайлович Юров ◽  
Владимир Иванович Гончаренко ◽  
Владимир Станиславович Олешко ◽  
Сергей Алексеевич Гученко

В работе рассмотрены вопросы анизотропии поверхностного слоя и анизотропии поверхностной энергии кубических кристаллов рутения. В основе этого рассмотрения лежит эмпирическая модель атомарно-гладких кристаллов, толщина поверхностного слоя которых зависит от одного фундаментального параметра -атомного объема элемента. Расчеты кристаллов рутения показали, что толщина поверхностного слоя кристаллов рутения во всех направлениях не превышает d (I) < 10 нм и они представляют собой наноструктуру. Кристаллы рутенийалюминий, рутенийгафний, рутенийтитан, рутенийцирконий имеют ơ > 3 Дж/м в направлении (100) . Нами рассмотрена задача о диффузии газа в нанометровой пластине рутения. В отличие от классической задачи в полученном уравнении появляется логарифмический член. Это приводит к расходимости в начале координат. Поэтому граничные условия нужно задавать не при x = 0, а при x = d (0) - длине де Бройлевской волны электронов. Только в этом случае имеют смысл классические уравнения диффузии. Существенно также, что, согласно полученному уравнению, диффузии нанопластины зависит как от материала пластины через коэффициент диффузии массивного образца, так и от размерного фактора. В классическом случае такой зависимости нет. Для описания фазовых переходов в наноструктурах предложены различные модели, среди которых можно отметить метод среднего поля Ландау, в котором используется параметр порядка. Мы воспользуемся теорией Ландау, заменяя температуру T на координату h . The paper deals with the anisotropy of the surface layer and the anisotropy of the free surface energy of cubic ruthenium crystals. This consideration is based on an empirical model of atomically smooth crystals, the thickness of the surface layer of which depends on single fundamental parameter - the atomic volume of an element. Calculations of ruthenium crystals showed that the thickness of the surface layer of ruthenium crystals in all directions does not exceed d(I)< 10 nm and they represent a nanostructure. Crystals of ruthenium aluminum, ruthenium hafnium, ruthenium titanium, ruthenium zirconium have ơ > 3 J/m in the (100) direction. We have considered the problem of gas diffusion in a nanometer ruthenium plate. In contrast to the classical problem, a logarithmic term appears in the resulting equation. This leads to divergence at the origin. Therefore, the boundary conditions must be specified not at x = 0, but at x = d (0) - the de Broglie wavelength of electrons. Only in this case the classical diffusion equations are meaningful. It is also important that, according to the obtained equation, the diffusion of the nanoplate depends both on the material of the plate through the diffusion coefficient of the bulk sample and on the size factor. In the classical case, there is no such dependence. Various models have been proposed to describe phase transitions in nanostructures, among which we can mention the Landau mean field method, in which the order parameter is used. We will use Landau's theory, replacing the temperature T with the coordinate h.

2021 ◽  
Vol 18 (1) ◽  
pp. 9-15
Author(s):  
V.M. Yurov ◽  

In the work of Shebzukhova and Arefieva, by the method of electronic-statistical calculation of the anisotropy of the surface energy of metals, a method for estimating the work function of electrons from a metal was determined. The surface energy and electron work function of four main faces of cadmium and zinc crystals and five faces of mercury are estimated. In the work of Bokarev, the anisotropy of the surface energy of single crystals was calculated from the model of coordination melting of crystals. Based on experimental studies and theoretical calculations, it is shown that the model of coordination melting of crystals unambiguously links the physicochemical properties of the surface of single crystals with their crystal structure. In our proposed empirical model, not only the anisotropy is calculated, but also the thickness of the surface layer of the metal. It is shown that the thickness of the surface layer is determined by one fundamental parameter - the molar (atomic) volume, which periodically changes in accordance with the table of D.I. Mendeleev. It is shown in the work that the work function of electrons changes proportionally with a change in the surface energy of the metal. This means that the device we have developed can be used to measure the state of the metal surface and its anisotropy.


2020 ◽  
Vol 17 (2) ◽  
pp. 25-30
Author(s):  
V.M. Yurov ◽  

The paper considers the method of ion-plasma nitriding of polished rods of hydraulic cylinders. With ion nitriding, the surface hardening of parts is most pronounced. This is due to the fact that the surface layer of the part does not exceed 20 nm, that is, it is a nanostructure. In this nanostructure, nitrogen diffusion processes are significantly different from bulk ones. The size effects in the nanostructure lead to the fact that the “classical” Fick equations do not work in the layer, and the diffusion of nitrogen in this layer depends logarithmically on the properties of the steel. It was theoretically found that diffusion in a nanoplate depends both on the material of the plate through the diffusion coefficient of the bulk sample D0 and on the size factor α. In the classical case, there is no such dependence.


1964 ◽  
Vol 54 (1) ◽  
pp. 417-423
Author(s):  
H. Deresiewicz

abstract The classical solution of Stoneley and Tillotson is generalized by considering the outer one of the pair of layers to be porous. Although the dispersion relation turns out, for practical purposes, to be identical with the one governing the classical case, the motion in the present instance is shown to be dissipative and the expression is exhibited for the specific energy loss.


2021 ◽  
Vol 23 (2) ◽  
pp. 59-62
Author(s):  
Yurov V.M. ◽  
◽  
Goncharenko V.I. ◽  
Oleshko V.S. ◽  
◽  
...  

In this work, we show how to calculate the surface energy anisotropy and the thickness of the surface layer of some magnetic nanostructures. As an example, the minerals of magnetite, ulvespineli, ilmenite andpseudobrukite, which have different crystal structures, are considered.


2019 ◽  
Author(s):  
V. M. Yurov ◽  
E. N. Eremin ◽  
S. A. Guchenko ◽  
V. Ch. Laurinas
Keyword(s):  

Forests ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 982 ◽  
Author(s):  
Demiao Chu ◽  
Jun Mu ◽  
Stavros Avramidis ◽  
Sohrab Rahimi ◽  
Shengquan Liu ◽  
...  

In continuation of our former study on a novel combined treatment of nitrogen–phosphorus fire retardant and thermomechanical densification on wood, this study focuses on the dynamic wettability and the bonding strength. The contact angle was measured using the sessile drop method and the surface energy was calculated according to the van Oss method. Water surface penetrating and spreading is analyzed by both the Shi and Gardner model and the droplet volume changing model. The results reveal that the combined treatment increased the surface energy, especially the acid–base component. The contact angle declined and the water droplet spread more easily on the surface. Meanwhile, the rate of relative droplet volume decreased by 32.6% because the surface layer was densified and stabilized by the combined process. Additionally, the surface possesses the lowest roughness and highest abrasion resistance on the tangential section. Thus, the bonding strength of the combined treated poplar decreased by 29.7% compared to that of untreated poplar; however, it is still 53.3% higher than that of 220 °C heat-treated wood.


2018 ◽  
Vol 52 (5) ◽  
pp. 2065-2082 ◽  
Author(s):  
Erik Burman ◽  
Jonathan Ish-Horowicz ◽  
Lauri Oksanen

We consider a finite element discretization for the reconstruction of the final state of the heat equation, when the initial data is unknown, but additional data is given in a sub domain in the space time. For the discretization in space we consider standard continuous affine finite element approximation, and the time derivative is discretized using a backward differentiation. We regularize the discrete system by adding a penalty on the H2-semi-norm of the initial data, scaled with the mesh-parameter. The analysis of the method uses techniques developed in E. Burman and L. Oksanen [Numer. Math. 139 (2018) 505–528], combining discrete stability of the numerical method with sharp Carleman estimates for the physical problem, to derive optimal error estimates for the approximate solution. For the natural space time energy norm, away from t = 0, the convergence is the same as for the classical problem with known initial data, but contrary to the classical case, we do not obtain faster convergence for the L2-norm at the final time.


Soil Research ◽  
1964 ◽  
Vol 2 (2) ◽  
pp. 133 ◽  
Author(s):  
DS McIntyre ◽  
JR Philip

A transient method for field measurement of gas diffusion into soil is presented. The theory of the method and the results of preliminary tests are given. Diffusion takes place from a reservoir mounted on a tube driven into the soil. The theoretical analysis is used in the design of the experimental method, the relative importance of the various parameters involved in apparatus design and in measurement being evaluated. The apparatus is described and sample calculations of parameters given. When porosity is uniform with depth, diffusion coefficients obtained in the field agree well with results of diffusion measurements of other workers made under better controlled (laboratory) conditions.


2019 ◽  
Vol 61 (12) ◽  
pp. 2432
Author(s):  
В.А. Постников ◽  
А.А. Кулишов ◽  
А.А. Островская ◽  
А.С. Степко ◽  
П.В. Лебедев-Степанов

An analysis of the change in the Gibbs free energy ∆G upon the formation of a flat nucleus of a p-terphenyl crystal at the liquid – air interface is presented, taking into account the anisotropy of the surface energy of the faces. The surface energy values of the p-terphenyl crystal faces were calculated by the atomic force field method OPLS, based on structural data. Experimental information on crystal growth from solutions and their surface properties was used to analyze the model.


2021 ◽  
Vol 103 (3) ◽  
pp. 101-114
Author(s):  
V.M. Yurov ◽  
◽  
A.T. Berdibekov ◽  
N.A. Belgibekov ◽  
K.M. Makhanov ◽  
...  

In our proposed empirical model, the anisotropy of the surface energy and the thickness of the surface layer of the high-entropy FeCrNiTiZrAl alloy are calculated. The thickness of the surface layer of this alloy is about 2 nm, which is an order of magnitude greater than the thickness of the surface layer of complex crystals, but is of the same order of magnitude as that of metallic glasses. The hardness and other properties of the high-entropy alloy are the same as for metallic glasses, but are 2-3 times higher than the hardness of stainless steels. The surface energy of the high-entropy FeCrNiTiZrAl alloy is about 2 J/m2, which corresponds to the surface energy of magnesium oxide and other crystals with a high melting point. However, unlike these crystals, the friction coefficients of a high-entropy alloy (~ 0.06) are much lower than that of ordinary steels (~ 0.8). We have theoretically shown that the friction coefficient is proportionally dependent on the surface energy and inversely proportional to the Gibbs energy, which significantly decreases for a high-entropy alloy, leading to low friction. The high hardness and low coefficient of friction of the high-entropy alloy facilitates the deposition of coatings from them on structural metal products, which contributes to their widespread use.


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