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Severe deformation of Hadfield steel occurs via different deformation mechanisms (slip or twinning) depending on the crystallographic orientation and direction of the applied load. The development of these mechanisms under dry sliding friction was investigated by comparing the calculated values of slip stresses for and single crystals. Shear stress calculations with allowance for the friction force showed that twinning is not the predominant deformation mechanism for the considered orientations. TEM studies of the dislocation structure, repolished and etched surface revealed agreement between the experimental and numerical data. According to EBSD analysis, reorientation on the worn surface and in the subsurface region changes depending on the combination of principal stresses in different areas of the worn surface. These results confirmed that conditions for the deformation mechanisms (slip and twinning) are determined by the local conditions in the sample mesovolume. The wear curves demonstrate two stages of even and uneven wear. The uneven wear mechanism is substantiated by the analysis of the structure in the subsurface region, wear debris, and the worn surface. An empirical scheme of the wear and damage accumulation mechanisms is proposed.

This paper presents the results of a study on the preparation and characterization of a Cr-DND/MoN detonation chromium-nanodiamond coating deposited on cemented tungsten carbide (WC–3 wt.% Co) mill blades using Arc-PVD and electrodeposition methods. The physical and mechanical characteristics of the coatings were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), XRD analysis, Raman spectroscopy, micro-identification, and scratch test (evaluation of the coating adhesion). It was shown that the Cr-DND/MoN coating consists of successive layers of Cr-DND (top), Cu (middle) and MoN (bottom) with separate phases of γ-Mo2N, α-Mo, α-Cu, Cr-DND and nanodiamonds. The Cr-DND composite electrochemical coating (CEC) was deposited from the conventional chromium plating electrolyte with the addition of nanodiamonds. The copper interlayer was deposited by the Arc-PVD method on the surface of the MoN coating to improve the adhesion strength of the Cr-DND CEC. The coating showed an optimum microhardness of about 14 ± 1 GPa and good adhesion with a critical load Lc of about 93 N. In addition to the expected experimental results, the coating has high wear resistance, confirmed by scratch tests.

A model of the large cracks formation in brittle solids is formulated taking into account different space-time scales of crack accumulation during deformation. Within the framework of the phase field method, a system of two coupled nonlinear parabolic equations is obtained that describe the deformation of a loaded medium during crack initiation on two spatial and temporal scales. The conditions are found under which the uniform distribution of cracks becomes unstable. The development of instability is accompanied by the formation of large cracks.

From general physical considerations and observations of ball lightning in natural conditions, the intensity of electromagnetic radiation from ball lightning is estimated according to the order of the value. Electromagnetic radiation can be the cause of accelerated movement of charged particles of the substance of a fireball (the movement on curvilinear trajectories).

The diffraction patterns of surface relief diffraction structures that consisted of two crossed identical superimposed gratings formed in As2S3 thin films by electron beam recording with subsequent chemical etching were studied. The angle between gratings with a grating period of 2 µm was varied between 2° and 90°. Additional diffraction gratings formed by a set of lines intersection nodes were considered for simulation of diffraction patterns. Diffraction structure composed of four identical crossed gratings was considered as combination of pairs of crossed gratings to calculate the diffraction pattern from it. A good agreement between experimental diffraction patterns and modeling ones was confirmed by the used method of calculation.

Abstract We report on the investigations of the magnetic properties and ferromagnetic resonance in the heterostructure consisting of an epitaxial yttrium iron garnet (Y_3Fe_5O_12) film and a nanometer rare-earth intermetallic superlattice comprised of the (TbCo_2/FeCo)_ n exchange-coupled layers. The (TbCo_2/FeCo)_ n superlattice exhibits the giant magnetostriction and the controlled magnetic anisotropy induced by a magnetic field or elastic stresses. The magnetic interaction of the films in the (TbCo_2/FeCo)_ n /Y_3Fe_5O_12 heterostructure has been experimentally established and the spin current flowing through their interface has been detected.

Anodic polishing of medium carbon steel (0.45 wt.% C) and austenitic stainless steel 12X18H10T in aqueous electrolytes based on ammonium chloride or ammonium sulfate is studied under conditions of natural or force convection. Surface roughness, weight loss of the samples, and the current as a result of polishing are measured. A possibility of the plasma electrolytic polishing using a setup for anodic thermal chemical treatment of compounds with their longitudinal flowing by electrolyte is shown. Polishing regimes are determined to decrease the initial surface roughness of the steels from Ra = 1.0 μm to 0.19–0.22 μm for5 minutes at a rate of the sample weight loss being 0.5–0.7 mg/s. The minimal surface roughness is obtained using a 3% solution of ammonium chloride at a flow rate of 0.8 l/min, a voltage of 300 V, and an electrolyte temperature of 80°C.

The effect of AlOOH endo-template on the porous structure, electrical conductivity and electrochemical properties of lactose-derived carbon materials was investigated. It was found that a carbon material with specific surface of 1707 m2/g and total pore volume of 1.546 cm3/g could be obtained when the mass ratio of C:AlOOH is 1:1. Electrochemical capacitors, formed on the base of the synthesized samples, have a large range of the specific capacity (66–170 F/g) at a discharge current of 10 mA. The developed mesoporous structure of the carbon materials synthesized via the template method allows charge/discharge electrochemical capacitors at currents up to 200 mA, providing specific capacity of 121 F/g.

Active control of friction by ultrasonic vibration is a well-known effect with numerous technical applications ranging from press forming to micromechanical actuators. Reduction of friction is observed with vibration applied in any of the three possible directions (normal to the contact plane, in the direction of motion and in-plane transverse). In this work, we consider the multi-mode active control of sliding friction, where phase-shifted oscillations in two or more directions act at the same time. Our analysis is based on a macroscopic contact-mechanical model that was recently shown to be well-suited for describing dynamic frictional processes. For simplicity, we limit our analysis to a constant, load-independent normal and tangential stiffness and two superimposed phase-shifted harmonic oscillations, one of them being normal to the plane and the other in the direction of motion. As in previous works utilizing the present model, we assume a constant local coefficient of friction, with reduction of the observed force of friction arising entirely from the macroscopic dynamics of the system. Our numerical simulations show that the resulting law of friction is determined by just three dimensionless parameters. Depending on the values of these parameters, three qualitatively different types of behavior are observed: (a) symmetric velocity-dependence of the coefficient of friction (same for positive and negative velocities), (b) asymmetric dependence with respect to the sign of the velocity, but with zero force at zero velocity, and (c) asymmetric dependence with nonzero force at zero velocity. The latter two cases can be interpreted as a "dynamic ratchet" (b) and an actuator (c).

AbstractThe interaction between Sb atoms and micropores of a getter layer in silicon is studied. The getter layer was obtained via implantation of Sb^+ ions into silicon and subsequent heat treatment processes. The antimony atoms located in the vicinity of micropores are captured by micropores during gettering annealing and lose its electrical activity. The activation energy of capture process to the pores for antimony is lower than that of antimony diffusion in silicon deformation fields around microvoids on the diffusion process.

AbstractDiscrete breathers (DBs) have been described among pure metals with face-centered cubic (FCC) and body-centered cubic (BCC) lattice, but for hexagonal close-packed (HCP) metals, their properties are little studied. In this paper, the properties of standing and moving DBs in beryllium HCP metal are analyzed by the molecular dynamics method using the many-body interatomic potential. It is shown that the DB is localized in a close-packed atomic row in the basal plane, while oscillations with a large amplitude along the close-packed row are made by two or three atoms, moving in antiphase with the nearest neighbors. Dependences of the DB frequency on the amplitude, as well as the velocity of the DB on its amplitude and on parameter δ, which determines the phase difference of the oscillations of neighboring atoms, are obtained. The maximum velocity of the DB movement in beryllium reaches 4.35 km/s, which is 33.7% of the velocity of longitudinal sound waves. The obtained results supplement our concepts about the mechanisms of localization and energy transport in HCP metals.

The presence of χ-Al2O3 resulting from thermal decomposition gibbsite as part of alumina catalysts is unfavorable because of its acid characteristics. One of the available techniques of χ-Al2O3 removal is crystallization under hydrothermal conditions into boehmite, which is a main precursor of active γ-Al2O3. The influence of products of the hydrothermal treatment of χ-Al2O3 obtaining in result of thermal decomposition gibbsite under T = 150–200 °C, P = 0.5–1.5 MPa and pH = 4.0–9.2 were studied. The hydrothermal treatment products in these conditions are gibbsite and boehmite phases which are formed coincidently by parallel ways. In the alkaline medium at pH = 8.0–9.2 three-dimensional parallelepiped boehmite crystals with the edge length > 200 nm are formed, at pH = 4.0 two-dimensional rhombic-shaped plates with thickness 20–100 nm and with the edge length ~ 80–500 nm are formed. Crystallization of coarse boehmite particles promotes the formation of large and closed mesoporous.

The general invariant integral based on the energy conservation law is introduced into physical mesomechanics, with taking into account the cosmic, gravitational, mass, elastic, thermal and electromagnetic energy of matter. The physical mesomechanics thus becomes a mega-mechanics embracing most of the scales of nature. Some basic laws following from the general invariant integral are indicated, including Coulomb’s law of electricity generalized for moving electric charges, Newton’s law of gravitation generalized for coupled gravitational/cosmic field, the Archimedes’ law of buoyancy generalized for bodies partially submerged in water, and others. Using the invariant integral the temperature track behind moving cracks and dislocations is found out, and the coupling of elastic and thermal energies is set up in fracturing and plastic flow, namely for opening mode cracks and edge dislocations. For porous materials saturated with a fluid or gas, the notion of binary continuum is used to introduce the corresponding invariant integrals. As applied to the horizontal drilling and hydrofracturing of boreholes in the Earth’ crust, the field of pressure and flow rate as well as the fluid output from both a horizontal borehole and a disk-shape fracture issuing the borehole, are derived in the fluid extraction regime. A theory of fracking in shale gas/oil reservoirs is suggested for three basic regimes of the drill mud permeation into the multiply fractured rock region, with calculating the shape and volume of this region in terms of the geometry parameters and pressures of rock, drill mud and shale gas. The method of functional equations in the theory of a complex variable and the boundary layer method are also used to solve these problems.

This paper presents a numerical study on the frictional contact between two crossed fibers subject to both normal and tangential oscillation. The results from simulation using the method of dimensionality reduction show that the frictional energy dissipation increases firstly with coefficient of friction, and then almost symmetrically decreases to a constant. The fiber aspect ratio has an important effect on the energy dissipation and this effect becomes more significant for larger coefficient of friction. The simulation results for very large coefficient of friction show a good agreement with the analytical solution for the case of infinite coefficient of friction.

В работе описан метод синтеза пероксокарбоната натрия при комнатной температуре путем электроосаждения карбоната на проводящие алмазные тонкопленочные электроды. Целью было изучение роли таких параметров, как концентрация электролита, интенсивность тока, добавление Na2SiO3 в качестве стабилизирующего компонента, а также повышение температуры при образовании пероксокарбоната натрия в электрохимической ячейке водорода, состоящей из двух отделений, разделяемых катионобменной мембраной. Образование окислителя подтверждено циклической вольтамперометрией и восстановлением in situ при электролизе водного раствора. Оптимальные условия эксперимента: плотность тока 34,3 мАсм-2, концентрация электролита 1M, при добавлении 4 g/L метасиликата натрия в оба отделения электрохимической ячейки., This work describes a method for synthesizing sodium peroxocarbonate by electoxidation of carbonate on conductive-diamond thin film electrodes in a sodium carbonate solution at room temperature. The effect of several parameters including: electrolyte concentration, current intensity, addition of Na2SiO3 as a stabilizing agent, and increments in temperature for sodium peroxocarbonate formation has been studied in an electrochemical H cell of two compartments separated by a cationexchange membrane. The oxidant formation has been confirmed by cyclic voltammetry and in situ reduction during water electrolysis. The optimal experimental conditions are: the current density of 34.3 mAcm-2, an electrolyte concentration of 1M, and the addition of 4 g/L of sodium metasilicate in the two compartments of the electrochemical cell. Keywords: peroxocarbonate, peroxosalts, diamond electrodes

В настоящей работе исследовано влияние ƴ‐излучения на процесс окисления Ni-P химически осажденного покрытия на нержавеющей стали марки 304 методом сканирующей электронной микроскопии (SEM) и рентгеновского анализа (EDX). Установлено, что после ƴ-излучения поверхность Ni-P слоя былa полностью покрыта трещинами, и на поверхности Ni-P слоя обнаружено высокое содержание кислорода и фосфора из-за образования оксида Р2О5., The given work deals with the effect of gamma-irradiation on the oxidation process of the Ni-P chemical deposition on the surface of the stainless steel marked 304. The methods used are scanning electron microscopy and X-ray analysis. As a result, it has been found out that after gamma-irradiation the surface of the Ni-P layer is completely covered with cracks, and on the surface of this layer a high content of oxygen and phosphor has been detected because of formation of the P2O5 oxide.

This work presents a model and simulation results for the friction detachment of a finite sized interface, following previous results on the phenomenon by Ben-David and Fineberg, namely “experiments demonstrating that the ratio of shear to normal force needed to move contacting bodies can, instead, vary systematically with controllable changes in the external loading configuration”. In particular, we extend a previous one-dimensional simulation model by Bar-Sinai with colleagues to a quasi 2D model to allow for a tilting of one of the contacting blocks. While Bar-Sinai with colleagues postulate that the presence of “slow fronts” of detachment (an order of magnitude lower than the usual Rayleigh fronts as in crack propagation) is due to a strengthening term in the friction law, which is not always measured in unlubricated contacts, we find slow fronts also with a purely weakening law.

В монокристаллических пленках и нитях висмута происходит переход полуметалл-полупроводник (ПМПП) благодаря эффекту размерного квантования (ЭРК), который модифицирует фононный спектр, что может представлять практический интерес. Эффект в большей степени может проявляться в наноструктурах на основе сплавов Bi1-xSbx в полуметаллической фазе (x < 0,04), где имеет место минимальное перекрытие L и Т зон. В данной статье представлены экспериментальные результаты исследований электронного транспорта, термоэлектрических свойств, осцилляций Шубникова де Гааза (ШдГ) пленок Bi-Sb (0 < x < 0,04) выращенных термическим напылением в вакууме и нанонитей в стеклянной оболочке, изготовленных усовершенствованным методом Улитовского-Тейлора. Результаты рентгеноструктурного анализа показали, что у монокристаллических пленок тригональная ось ориентирована перпендикулярно плоскости подложки, а одиночные нити Bi-2ат.%Sb с диаметрами 100–1000 нм представляют собой монокристаллы с ориентацией (1011) вдоль оси нити. Исследования ШдГ осцилляций нитей Bi-2ат.%Sb с диаметрами d > 600 нм показали, что перекрытие L и Т зон в 2 раза меньше, чем в чистом Bi. Температурные зависимости сопротивления R(T) тонких полуметаллических пленок Bi-3ат.%Sb и нитей Bi-2ат.%Sb показывают полупроводниковую зависимость с уменьшением диаметра. Переход (ПМПП), индуцированный размерным квантованием наблюдался при диаметрах почти в 5 раз больших, чем в аналогичных образцах чистого висмута. Этот экспериментальных факт позволяет с одной стороны продвинуться в область более высоких температур (для наблюдения КРЭ), а с другой стороны разделить эффекты, связанные с размерным квантованием и поверхностными состояниями. В полуметаллических пленках Bi1-xSbx обнаружено сжимающее действие подложки из слюды, и растягивающее подложки из полиимида в направлении перпендикулярном плоскости пленки, что может служить дополнительным фактором управления переходом (ПМПП). Также обсуждается вопрос термоэлектрических свойств нитей для оптимизации и использования их в термоэлектричестве., In this paper we present the experimental results of an investigation of the electrical transport, thermoelectrical properties, the Shubnikov de Haas oscillations of Bi1-xSbx films (0 < x < 0.04) grown by the vacuum thermal evaporation and nanowires prepared by a modified Ulitovsky – Teilor technique. The results of the X-ray diffraction indicate that the trigonal axes were perpendicular to the film plane and the single Bi-2at%Sb nanowires with the diameter 100–1000 nm were represented by single crystals in a glass capillary with (1011) orientation along the wire axis. The investigations of the Shubnikov de Haas oscillations on Bi-2at%Sb wires with d > 600 nm show that overlapping of L and T bands was twice smaller than that in pure Bi. The temperature dependences of thin semimetalic Bi-3at%Sb films and Bi-2at%Sb wires show a semiconducting behavior. The semimetalsemiconductor transition induced by the quantum confinement effect is observed in semimetal Bi1-xSbx films and nanowires at the diameters up to five times greater than those in the pure Bi. That experimental fact, on the one hand, will allow observing the display quantum confinement effect at higher temperatures on nanowires of the same diameters, and, on the other hand, will allows separating effects connected with the surface state and the quantum size effects. In addition, the thermoelectric properties and thermoelectric efficiency of bismuth-antimony wires are considered and a possibility to use them in thermoelectric converters of energy is discussed.

In this paper, we review the main contributions developed by the authors to solve problems involving contact between bodies with a roughness covering several orders of magnitude. A periodic self-equilibrated formulation is introduced to avoid any border problem. Furthermore, when focusing on the steady-state rolling or sliding contact mechanics between viscoelastic materials, we develop a mathematical formulation, parametrically dependent on the rolling/sliding speed, which employs the same computational techniques introduced for elastic rough contacts. In particular, in both cases, we adopt an ad hoc discretization technique enabling us to reach the full convergence.

Магниевые сплавы являются многообещающим конструкционным металлом и остаются главным конкурентом алюминиевых сплавов в областях, где важны весовые характеристики. Их основной недостаток – высокий уровень подверженности коррозии, поэтому борьба с коррозией магниевых сплавов находится в центре внимания исследователей в области материаловедения во всем мире. Сплав Mg-Zn-RE (ZE41) часто используется в автомобильной промышленности и авиастроении. Целью данной работы было изучение влияния водородного показателя (pH) среды и концентрации ионов сульфата аммония на устойчивость к коррозии сплава ZE41. Применялись такие известные в электрохимии методики, как импедансная электрохимическая спектроскопия и поляризационные измерения. Опыты проводились при постепенном изменении pH и концентрации ионов сульфата аммония. Структура и состав поверхности сплава, подвергшегося коррозии, анализировались с помощью сканирующего электронного микроскопа и рентгеноструктурного анализатора на основе метода энергетической дисперсии, соответственно. Полученные результаты отражают тенденцию к увеличению скорости коррозии при повышении концентрации ионов сульфата аммония и заданном pH, или при уменьшении pH и при заданной концентрации ионов сульфата аммония, Magnesium alloys have emerged as potential structural materials with all capabilities to even replace close contenders; aluminium alloys in weight-critical applications. High susceptibility to corrosion being the only limitation, corrosion of magnesium alloys continues to gather much attention among the material scientists worldwide. ZE41 is one such alloy of magnesium which is increasingly gaining importance as automobile and aerospace material. In the present study the influence of the medium pH and sulfate ion concentrations on the corrosion behavior of magnesium alloy ZE41 has been investigated using electrochemical techniques like the Tafel extrapolation and electrochemical impedance spectroscopy (EIS). The tests have been carried out in a range of conditions, with gradually varying pH and sulfate ion concentration. The morphology and composition of the corroded alloy surface have been determined by the scanning electron microscopy (SEM) and energy dispersion X-ray (EDX) analysis, respectively. The recorded results reflect a trend of a higher corrosion rate associated with a higher sulfate concentration at each pH and with a lower pH at each sulfate concentration

Ингибирующая активность двух природных соединений экстрактов лавзонии и розмарина на коррозию стали 304L в 3,5% растворе NaCl была исследована электрохимическими методами и методом исследования поверхности. Поляризационные измерения показывают, что исследуемые соединения являются ингибиторами смешанного типа и зависят от концентрации экстракта: чем больше концентрация, тем больше ингибирующая активность. Максимальная ингибирующая активность экстрактов лавзонии (92,7%) и розмарина (90,2%) наблюдалась при их концентрации 1 г/л. Поляризационные кривые показывают, что экстракты лавзонии и розмарина являются ингибиторами катодного и анодного типа соответственно. Указанные добавки в солевой среде являются адсорбционными ингибиторами и их адсорбция подчиняется адсорбционным изотермам Лэнгмюра., The inhibitive action of two natural compounds – henna and rosemary extracts, on the corrosion of 304L stainless steel in 3.5% NaCl solution has been investigated through electrochemical techniques and surface analysis. Polarization measurements indicate that the investigated compounds are mixedtype inhibitors, and the higher the inhibitor concentration, the higher the inhibition efficiency. Maximum inhibition efficiencies of 92.7% and 90.2% of henna and rosemary extracts are obtained at 1.0 g/L, respectively. The polarization curves show that henna and rosemary extracts act as a cathodetype and an anodic-type inhibitor, respectively. The results show that these additives in saline media are adsorptive inhibitors and their adsorption obeys the Langmuir adsorption isotherm.

Из мицелиального гриба Aspergillus niger 33-19 CNMN FD 02A, культивируемого в стандартных условиях и после облучения миллиметровыми волнами λ = 7,1, были получены два ферментных препарата со степенью очистки Г10x, отличающихся по уровню амилолитической активности (на 29,9% выше в препарате, подвергнутом облучению), но с идентичной специфической активностью в 138,3 ед/мг и 141,0 ед/мг белка. Очистка α-амилазы методами гель-фильтрации и ионообменной хроматографии привела к увеличению специфической активности в 8,9 раз в контрольном и в 8,2 раза в облученном препаратах, с 25% и 17% выходом, соответственно. SDS-ПААГ белков, выделенных из начальных препаратов, показала появление нового полипептида с молекулярной массой 45 kDa в образце, подвергнутом облучению. Полипептидный спектр очищенной α-амилазы обоих препаратов после ионной хроматографии представляет 2 неизменныe полипептидныe полосы с молекулярной массой 66 и 40,5 kDa, определенных как изоформы α-амилазы., Micromycete Aspergillus niger 33-19 CNMN FD 02A standard cultivated and exposed to λ = 7.1 millimeter waves radiation has been used to obtain two enzyme preparations with the 10x degree of purity, with a 29.9% difference of the α-amylase activity in irradiated preparation but with a similar specific activity of protein of 138.3 U/mg and 141.0 U/mg. The α-amylase purification through gel filtration and ion exchange chromatography has resulted in the increase of 8.9 times of the specific activity for the control and of 8.2 times for the irradiated samples, with the yields of 25% and 17%, respectively. The SDS-PAGE of proteins isolated from initial preparations indicates the expression of new polypeptide of 45 kDa in the irradiated samples. Polypeptide spectrum of α-amylase from both preparations, purified through ion chromatography, shows two unchanged polypeptide bands of 66 and 40.5 kDa, identified as α-amylase isomorphs.

Теоретическое исследование поверхности монокристаллического кремния c индуцированными SF6 плазмой шероховатостями осуществлено с помощью атомно-силовой микроскопии. Плазма, содержащая неустойчивость сдвига скорости, была использована для изучения связи между параметрами плазмы и соответственно параметрами шероховатой поверхности. Шероховатость поверхности была исследована в зависимости от параметров эксперимента. Результаты, полученные в теоретических расчетах, совпадают с экспериментальными результатами. Количественно выполнен учет влияния таких параметров плазмы, как отношение потока ионов к нейтральному потоку реагента (J+/JF), время экспозиции, постоянное электрическое поле, магнитное поле и неустойчивость в DC электрическом поле. Теоретическое исследование показывает, что шероховатость поверхности кремния увеличивается при увеличении значения J+/JF, времени экспозиции, магнитного поля, неоднородности в постоянном электрическом поле и уменьшается при увеличении величины постоянного электрического поля., A theoretical study of single-crystal silicon surface roughness induced by SF6 plasma has been carried out by means of atomic force microscopy. Plasma which contains the velocity shear instability has been used to study the relation between the plasma parameters and subsequent surface roughness. The surface roughness has been examined in the dependence on experimental parameters. The results obtained by theoretical calculations are identical to the experimental ones. The present paper has quantified the influence of a DC electric field values on plasma parameters such as the ratio of ion flux to the neutral reactant flux (J+/JF), exposure time, DC electric field, magnetic field and inhomogeneity. Theoretical investigation shows that the roughness of silicon surface increases with the increase of the values of J+/JF, exposure time, of magnetic field, of inhomogeneity in a DC electric field and decreases through increasing the value of a DC electric field.

Многослойные нанокомпозитные покрытия из Zn-Ni-SiO2 осаждались гальваностатическим методом на низкоуглеродистую сталь (НС) из ванны с Zn-Ni в присутствии Zn+2Ni+2 ионов и равномерно диспергированных нано-SiO2 частиц. Коррозионные характеристики и свойства многослойных нанокомпозитных (МНК) покрытий оценивались электрохимической поляризацией и методом импедансов. Условия осаждения такие, как состав ванны, циклическая плотность катодных токов (ЦПКТ) и количество слоев были оптимизированы с целью получения максимально коррозионностойких покрытий. Значительное улучшение антикоррозийных свойств многослойных нанокомпозитных покрытий наблюдалось при замене монослойных покрытий на многослойные. Скорость корродирования (СК) МНК покрытий уменьшалась поступательно в соответствии с количеством слоев до оптимального уровня, а затем начинала увеличиваться. Увеличение СК на более высоком уровне наслаивания связано с диффузией слоев из-за короткого времени осаждения и невозможности создания антикоррозийной защиты. Формирование слоев, включения силиконовых частиц в матрице МНК покрытий было подтверждено с помощью SEM и XRD анализов. При оптимальных значениях плотности тока, то есть 3,05–5,0 А/см2 , покрытие из Zn-Ni-SiO2 состоящее из 300 слоев, обозначенных как (Zn-NiSiO2)3.0/5.0/300, в 107 раз превосходит по антикоррозийности монослойное покрытие из Zn-Ni-SiO2, образованное в той же самой ванне и за то же время. Причины увеличенной защиты от коррозии МНК покрытий из Zn-Ni-SiO2 по сравнению с соответствующими монослойными покрытиями из Zn-Ni и (Zn-Ni-SiO2) проанализированы и результаты описаны., Multilayer nanocomposite coatings of Zn-Ni-SiO2 were deposited galvanostatically on mild steel (MS) from Zn-Ni bath, having Zn+2 and Ni+2 ions and uniformly dispersed nano-SiO2 particles. The corrosion characteristics and properties of multilayered nanocomposite (MNC) coatings were evaluated by electrochemical polarization and impedance methods. Such deposition conditions as, bath composition, cyclic cathode current densities (CCCD’s) and number of layers were optimized for peak performance of coatings against corrosion. A significant improvement in the corrosion performance of MNC coatings was observed when a coating was changed from a monolayer to multilayer type. Corrosion rate (CR) of MNC coating decreased progressively with number of layers up to an optimal level, and then started increasing. The increase of CR at a higher degree of layering is attributed to diffusion of layers due to a very short deposition time, failing to give the enhanced corrosion protection. The formation of layers, inclusion of silica particle in MNC coating matrix were confirmed by SEM and XRD study. At optimal , the Zn-Ni-SiO2 coating having 300 layers, represented as (ZnNi-SiO2)3.0/5.0/300 is found to be about 107 times more corrosion resistant than a monolayer Zn-Ni-SiO2 current densities, i.e. at 3.0–5.0 A/cm2 coating, developed from the same bath for the same time. The reasons responsible for the extended corrosion protection of MNC Zn-Ni-SiO2 coatings, compared to corresponding monolayer Zn-Ni and (Zn-Ni-SiO2) coatings were analyzed, and results were discussed.

Приведены результаты оптимизации параметров синтеза гидротермальным методом в СВЧ поле легированных Ag наночастиц TiO2. Для оптимизации процесса использовались метод Тагучи (матрица L8) (Taguchi L8) и план второго порядка Дрейпера-Лина (Draper-Lin small composite design). Определены технологические факторы процесса синтеза, как то концентрация примеси, продолжительность и температура процесса, подводимая СВЧ мощность, состав и рН раствора, степень заполнения автоклава, влияющие на стабильность размеров легированных Ag наночастиц TiO2. Показано, что оба использованных метода оптимизации приводит к подобным результатам., The efficiency and competitiveness of using nanomaterials can be increased through introducing scientific experimental designs. For obtaining experimental models which can better approximate the real technological systems, a sufficient number of control factors and of necessary experiment units should be taken into account, having in view their economical aspect, too. Considering the importance of Ag-doped TiO2 nanoparticles in such domains as industry, environmental protection, health, etc., it is important for manufacturers to obtain nanoparticles of equal dimensions. The present paper is analyzing the ways of improving dimensional stability of Ag-doped TiO2 nanoparticles produced by the microwave-hydrothermal (M-H) method. In one case, a two-level L8 Taguchi design was used in 8 experiments, with seven control factors. In the other case, the Draper-Lin design of 40 experiments for 7 factors at two levels was utilized. It has been found out that the L8 Taguchi experimental design offers the same results as the Draper-Lin experimental design, but with much fewer experiments.

В работе исследованы температурные зависимости электрической проводимости, концентрации свободных носителей и подвижности в монокристаллических образцах PbTe:Gd с примесями в различной концентрации. Наблюдаемые особенности, обнаруженные в результате измерения коэффициента Зеебека, состоят в существенном увеличении коэффициента термоэлектрической мощности. Измерения магнитной восприимчивости при низких температурах позволяют предположить, что ионы гадолиния могут находиться в различных зарядовых состояниях., Under investigation are temperature dependences of electric conductivity, free carrier concentration and mobility in single-crystalline PbTe:Gd samples with varied impurity content. The features of electron transport in PbTe:Gd may be caused by a variable gadolinium valence. The striking result from the Seebeck coefficient measurements is that the thermoelectric power factor increases dramatically. Measurements of the magnetic susceptibility at low temperatures permit us to suggest that Gd ions may exist in different charge states.

Mode 1, 2 and 3 cannot exist in isolation. One mode provokes the existence of a coupled mode which, in some conditions, can be more dangerous than the generating mode itself. This means that three-dimensional problems are automatically at least dual scale. While for a crack this effect was known to exist for a long period of time, it was largely ignored in theoretical studies of V-shaped notches subjected to in-plane and out-of-plane loading as well as in practical fracture problems associated with such geometries. Only recently, some numerical investigations confirmed that highly localized coupled modes do exist in the close vicinity of the notch tip. The present paper is aimed to briefly review important features of these recently identified singular coupled modes. The most significant results from a comprehensive three-dimensional numerical study are presented here to describe the contribution of these modes into the overall stress state in the close vicinity of the notch tip and discuss the implementation of these new results to the failure and integrity assessment of plate structures with sharp notches.

Исследованы возможности применения сварки трением для соединения разнородных и калиброванных материалов, начиная с преимуществ, предоставляемых такой технологией при компоновке комплектующих для обрабатывающего оборудования и использования в автомобильной промышленности. Проведены эксперименты по сварке трением (при высокой температуре) 42CrMo4 со сталью марки C45, и со сталью X6CrNiTi18–10, обработанной раствором, а так же по соединению меди со сплавами Al. Осуществлен металлографический анализ и выполнены измерения твердости для уточнения особенностей процесса создания соединений, которые трудно получить традиционной электродуговой сваркой., Investigations concerning opportunities to apply the friction welding technique for joining dissimilar and graded materials are considered, starting from the advantages offered by this process in assembling parts for manufacturing equipments parts and automotive industry components. Experiments have been carried out on friction welding of heat treated 42CrMo4 with C45 steel and with the solution treated X6CrNiTi18–10 steel, as well as on joining copper with Al alloys. Metallographic observations and hardness measurements are performed in order to detail the peculiarities of the process of making joints that are difficult to obtain by conventional electric arc welding.

The time dependence of the contact force resulting from the rolling of a sphere on self-affine fractal rough surfaces was investigated using the method of reduction of dimensionality. The main focus was on the part of the spectrum corresponding to the short wavelength corrugation (with a wavelength much smaller than the nominal contact radius). It has been shown that in this domain, the spectral density of the normal force is a power function of frequency. This result can be used for calculation of high frequency acoustic emission of rolling contacts in various technical systems as well as for development of diagnostic systems.

In this work we present a new method to describe movements of stick-slip microdrives. On the microscopic scale we model the contact between actuator and slider as a dynamic tangential contact using the method of reduction of dimensionality. On the macroscopic scale simple one- and three-dimensional equations of motion are derived. An algorithm to solve these equations will be introduced. The results of the simulation will be compared qualitatively and quantitatively to experimental investigations. Even for the simplest assumed model it proves that experimental and numerical values correlate excellently.

In this paper, the Langmuir isotherm, originally derived for the adsorption of asphaltene extracted from shale oil and dissolved in toluene on Kaolin, Smectite, Fluorite and Hematite, was modified to fit the adsorption isotherm. The modified Langmuir isotherm parameters obtained from the four linear equations using the linear method differed. The aim of the proposed modification is based on the fact that direct application of the Langmuir isotherm often leads to poor data fitting. In the present communication, it is shown that the level of data fitting to the Langmuir isotherm can be improved by a simple modification through introducing a concentration dependent factor, X. The present paper discusses four modified Langmuir linearized isotherm models and one non-linear isotherm model: their coefficients are estimated and, for the study of non-linear isotherm model, genetic algorithm is used. A genetic algorithm procedure was utilized to optimize the modified Langmuir constants for a more accurate estimation of the set of model parameters. The obtained results demonstrated that the best fit was obtained using genetic algorithm. Furthermore, it was found out that from the surface minerals mentioned, Hematite mineral follows a multilayer adsorption isotherm.

Starting from the classical theory of contact mechanics it is shown that the relationship between load, penetration and contact radius of any axisymmetric contact can be mapped exactly on a one-dimensional system, thus the reduction method of dimensionality is valid for conforming and non-conforming contacts. Furthermore the reduction method has been successfully extended to adhesive contact problems. The mapping of the classical theory of Johnson, Kendall and Roberts derived for spherical contacts as well as its application to axisymmetric contacts of arbitrary shape is possible; all results are reproduced precisely.

The method of reduction of dimensionality in contact mechanics is based on a mapping of some classes of three-dimensional contact problems onto one-dimensional contacts with elastic foundations. Recently, a rigorous mathematical proof of the method has been provided for contacts of arbitrary bodies of revolution with and without adhesion. The method of reduction of dimensionality has been further verified for randomly rough surfaces. The present paper gives an overview of the physical foundations of the method and of its applications to elastic and viscoelastic contacts with adhesion and friction. Both normal and tangential contact problems are discussed.

The force of friction between a self-affine fractal rough surface and an elastomer with the simplest linear rheology is simulated with the method of reduction of dimensionality. The coefficient of friction increases with normal force approximately according to logarithmic law.

We consider a pair of bodies contacting on an elastic substrate; the distance between the bodies oscillates harmonically at a high frequency. If a horizontal force is applied to the bodies, macroscopic movement starts only after achieving some critical value, which we identify with the static friction force of the oscillating system. The dependence of the static friction force on the oscillation amplitude is simulated numerically using the method of reduction of dimensionality. Results of simulation are compared with experimental data.

This paper draws a line from early attempts of modeling stick-slip microdrives to open questions from today’s research. As a basis, it contains a collection of substantial investigations on piezo-actuated stick-slip microdrives for nanomanipulation purposes. Friction models showing special characteristics and their mathematical representations are reviewed. It is found that the working properties of stick-slip drives strongly depend on friction characteristics of the contact points between the guiding elements, which is known for years. However, numerous publications in the field of friction and remaining problems — which cannot be explained by known friction models — indicate that there is a demand for even more friction-related research. Former attempts to model stick-slip drives are based on the so-called LuGre friction model, which is shortly presented. An empirical model called CEIM is also analyzed. It is an adaption of the elastoplastic model. The latter can cover not only the phenomenon “0-amplitude” (described by the authors in recent publications), but also stick-slip based force generation scenarios. Nevertheless, interesting friction characteristics such as the generation of µN forces with stick-slip drives, which are already proven, cannot be covered by known friction models. It is pointed out which characteristics have to be considered.

The reduction method was applied to solving the elastic contact problem of fractal rough surfaces having different fractal dimensions. These surfaces are of particular interest, as contact spots influence each other on large and small scales, depending on the power spectrum. Results were compared to previous boundary-element method simulations that had been conducted with 3D surfaces, taking into account all interdependencies between contact spots. Excellent agreement in the contact stiffness was found. Even though no interactions are allowed in the reduced model, the same power-law behavior can be observed as in the 3D case, due to the transformation of the power spectrum. Theoretical considerations about the power-law for different fractal dimensions are given.

The present investigation is based on the assumption that the static coefficient of friction can be characterized roughly by the rms value of the surface gradient in the contact region. We numerically investigate the contact between a rigid, randomly rough surface and an elastic half-space and determine the dependence of the rms slope in the contact region on the normal force. For fractal surfaces with a Hurst exponent of H ≈ 1, the rms slope can be approximated very well by a logarithmic function of the normal force. Parameters of the approximation have been determined as functions of the Hurst exponent. The rms value of the slope always increases with the normal force, which indicates that the coefficient of friction should be an increasing function of the normal force.

Analysis and study of parallel flow velocity shear and electrostatic ion cyclotron (EIC) instability performed in plasma containing massive positive ions and electron by using the method of characteristics solution and kinetic theory in the presence of homogeneous direct-current (DC) electric field perpendicular to ambient magnetic field. The calculation of growth rate and real frequency has been done by using the computational technique. The effect of many parameters like shear scale length, homogenous d.c.electric field, magnetic field, electron ion temperature ratio, angle between wave number k⊥ and k|, on growth rate and also the effect of homogenous d.c.electric field, magnetic field on real frequency has been discussed by using the experimental data. Applications to possible laboratory plasmas and industries are also analyzed.

The giant magnetoresistance of electrodeposited NiFe/Cu multilayers from a single bath under potentiostatic control is studied. The observed nonsaturating behavior urged us to investigate the probability of the occurrence of superparamagnetic regions in these multilayers. In this research, for the first time, the presence of super-paramagnetic regions in electrodeposited NiFe/Cu multilayers is shown and proved via high resolution transmission electron microscopy. The reason was found to be the existence of a very large anodic transient at the beginning of the copper deposition pulse, which could be eliminated by choosing a more negative potential.

Electrochemical micromachining can remove electrically conductive materials with the transferring of ions, so that high precision is achievable. A novel method for fabricating high-aspect-ratio microstructures by electrochemical micromachining using vibratile tungsten wire was proposed in this paper. The slight vibration of tungsten wire can improve the machining stability. The relations between the machining accuracy and machining parameters were experimentally studied. Micro groove with the width of 15 μm was machined, and micro sharp-angles structure with aspect ratio of 10 was obtained experimentally.

The choice of proper working conditions is a problem for any processing. But for laser processing this procedure is much more serious. The final results of the processing are usually influenced by over 100 factors. So the best way to choose more cheaply and fast the working conditions is to use the processing simulation. Different tactics of this procedure is discussed and the statistical modeling is accepted. The actual model for laser cladding is developed based on the experimental results of steel cladding with diode laser robotized system. This model can be used to find the optimal working conditions for laser processing in practical use.

The donor-acceptor pair in the external periodic electric field is under studying. The molecular system is excited by the short impulse of the polarized light, and the electronic excitation initially localized on the donor and interacts only with full symmetrical vibration of the ligand environments, thus the vibrational subsystem forms the package in the form of the coherent state. Donor and acceptor molecules are assumed as identical type of the molecules. The time dependence of the depolarization of the fluorescence is numerically calculated on the basis of the semi-phenomenological model. Numerical estimates are given for cases of the strong and weak electron-vibrational interaction. Transfer of the excitation in the system is defined by the non-linear properties of the system, especially in the case of strong electron-vibrational interaction. The depolarization of the fluorescence is consequence of the such transport and contains the interference addends which conduct to the quantum beats in the time dependence.

In this study, the adsorption of quinalizarin by natural and mesoporous acid activated palygorskite has been examinated in order to remove coloured textile dyes from non aqueous solutions. The adsorption of quanilizarin from ethanol solution onto acid activated palygorskite was followed by UV-Visible measurement. The adsorption capacity was largely improved when the clay was activated by HCl. The high adsorption extents were observed from 2M8h to 2M 35h acid treated palygorskite samples. Adsorption isotherms of quinalizarin on acid activated palygorskite were determined and correlated with common isotherm equations such as Langmiur and Freundlich models. It was found that i/the adsorption isotherm exhibits two plateaus ii/ no model fit the isotherm data. In order to explain the adsorption behaviour of quinalizarin from ethanol onto palygorskite, the presence of stronger and weaker adsorption sites was suggested and checked by using the modified Langmuir model.

The purpose of this paper is to study the thermal behaviour of Na +-saturated Tunisian kaolinite (ka-Tab) with the evolution of its point of zero charge (PZC). The Fourier Transform Infrared spectroscopy (FTIR), X-Ray Diffraction (XRD), Differential Thermal Analysis (DTA), Cation Exchange Capacity (CEC) and specific surface area (SSA) were used to characterize the kaolinite sample. In the present investigation, the focus was on the surface charge characteristics of kaolinite at different temperature of heating. The results show that the formation of new phases in the kaolinite structure at temperature > 500-600°C, shifts the PZC value towards 8 which approximately PZC value of y-Al2O3.

The physico-chemical characterization of Tunisian bentonitic clays is based on the determination of the mineralogical composition (X-ray diffractions and infrared spectroscopy), chemical analysis, cation exchange capacities and the total surface area. The result given by these techniques show that these samples were smectic clay of beidellitic character. In the other hand, the activation of these clays by hydrochloric acid shows an increase of the specific surface area and favorite the clarification of vegetable oils.

The lack of practical information regarding the kinetics of a thermal process can be compensated by estimating the kinetic parameters of the process. Using the methodology imposed by Baram, as well as to one resulted form the use of the solution to the Fick’s differential equation, through a minimum number of experiences, can be obtained sufficient information to estimate the process’ average speed, its activation energy, the diffusion coefficient, etc., and forecast the saturation effects in conditions different from those used for experiments to obtain preliminary information. This paper presents the experimental results obtained during the nitriding of pure technical iron and respectively of a nitraloy type alloyed steel for improvement, regarding the kinetic of the nitrided layers’ growth and starting from this results, the calculated values of the of the kinetic parameters, respectively the forecasted values of the kinetics in conditions different from those effectively used during experiments.

The aim of this study was to determine optimum conditions of the DL EPR test in order to evaluate the highest values of the degree of sensitization (DOS) of a forged austenitic stainless steel type 316L, evaluated by the ratio Ir/Ia or Qr/Qa in %. The criteria of sensitization to the IGC corresponds to Ir/Ia >1% and Qr/Qa >1%. A model using a full factorial design has been established and the selected factors were the sweep rate (dE/dt), sulphuric acid concentration (H2SO4), ammonium thiocyanate concentration (NH4SCN) and temperature in °C. A first order model is obtained by using 24 full factorial design. An experimental test carried out using a factorial design 24 indicated that all the factors and their interactions have a positive effect on the response Ir/Ia. Furthermore, the highest value detected of Ir/Ia was found to be 65,6 %. On the other hand, a microstructural study based on optical microscope and Scanning Transmission Electron Microscope (STEM), have been carried out for annealed and aged samples (550°C-80 000 h). The profiles of chromium, nickel and molybdenum concentration established by X-ray microanalysis in STEM, confirm a decrease of content of these elements leading to the formation of Cr-depleted zones responsible of the sensitization to the IGC.

The effect of exchange cations (Mn+: Li+, Na+, K+, NH4+, Ca2+, Mg2+, Fe3+, and Al3+) and thermal treatment on the physicochemical properties of smectite was investigated. Before thermal treatment, unheated (25°C) Mn+-smectite showed increased d001 spacing upon glycol solvation; after heating at 300°C or above (400°C), d001 spacing upon glycol solvation of Al-, Fe-, Mg-, Li-smectite decreased and reached 10 A. However, an increase in d001 of Ca2+-, Na+-and NH4+-smectite upon glycol solvation indicated that d001 varied with the nature of exchangeable cation and the temperature of heating. The results generally suggested the following: d001 of homoionic smectite before and after heating at various temperatures depended upon the nature of exchangeable cation. The cation exchangeable capacities (CECs) and the BET surface areas (SBETs) were functions of the type of exchangeable cations, since SBETs drop off in the following order: Na+-smect > Ca2+-smect > Mg2+-smect > NH4+-smect > Li+-smect > K+-smect > Fe3+-smect > Al3+-smect. Finally, we have noted good progress in the exchangeable properties of synthesized clay in comparison with the Na homoionic smectite form, except for K homoionic clay, which have the lowest CECs, SBETs, and consequently, the lowest exchangeable properties.