369 Works

Influences of solvent types on the formation of graphene in the electrochemical exfoliation method

T. Kurniawan, M.A. Anwar, R. Oktiani, R. Ragadhita, A.B.D. Nandiyanto & M. Aziz
The aim of this study was to evaluate the effect of different solvents in sonication process on the formation of graphene from the electrochemical exfoliation of graphite. In short, graphite rod was exfoliated by electrochemical process with ammonium sulfate as salt-electrolyte. The exfoliated powder then sonicated under two different solvents, which are Dimethylformamide (DMF) and aqueous solution to form graphene. It was found that similar structure of graphene was obtained from both types of solvent....

MECHANISM OF MOLECULE MIGRATION OF CARBON AND SILICON MONOXIDES IN SILICON CARBIDE CRYSTAL

S.A. Kukushkin, A.V. Osipov & E.V. Osipova
The main processes occurring during the migration of molecules of carbon monoxide CO and silicon monoxide SiO gases through a layer of monocrystalline silicon carbide SiC of a cubic polytype have been described by the ab initio methods. This problem arises when a single-crystal SiC layer is grown by the method of coordinated substitution of atoms due to the chemical reaction of a crystalline silicon substrate with the CO gas. The reaction products are epitaxial...

THE INFLUENCE OF GAMMA RAYS RADIATION ON OPTICALLY INDUCED LUMINESCENCE OF COPPER-CONTAINING POTASSIUM-LITHIUM-BORATE GLASS

P.S. Shirshnev, V.A. Spiridonov, D.I. Panov, E.V. Shirshneva-Vaschenko, A.R. Gafarova, R.M. Eremina, A.E. Romanov & V.E. Bougrov
The paper presents the results of potassium-lithium-borate glass containing copper ions investigations. The glass was irradiated by 1.25 MeV gamma rays. The dose of radiation was 360 Gy. The exciting of the irradiated glass at 360 nm led to the long-wavelength photoluminescence band shift from 635 nm to 671 nm in comparison with non-irradiated glass. A new luminescence band at 685 nm also appeared for excitation wavelength 405 nm in the irradiated glass. It has...

THE STRUCTURAL TRANSFORMATION AND MECHANICAL STRENGTH OF Ni, Ti NANOWIRES AND NITINOL ALLOYS AT VARIOUS VACANCY RATES: MOLECULAR DYNAMIC STUDY USING CLERI-ROSATO POTENTIAL

M.M. Aish
A many-body interatomic potential was used for Nickel (Ni) crystal with facecentered cubic (FCC) lattice and Titanium (Ti) with hexagonal close-packed (HCP) lattice and Nitinol alloys within the second-moment approximation. The tight-binding model (the Cleri and Rosato potentials) was employed to carry out three dimensional molecular dynamics simulations upon application of uniaxial tension at nanoscale of studied materials, which contained various vacancy rates. We performed molecular dynamics (MD) simulations to study the yield mechanisms in...

Numerical method of single-crystal turbine blade static strength estimation taking into account plasticity and creep effects

Boris Vasilyev & Alexander Selivanov
To increase the reliability of single-crystal blade durability estimations a phenomenological model of single crystal superalloy plasticity based on the use of an “equivalent” direction and its software implementation has been developed. The relative orientation between principal stresses and single-crystal (SX) axes is considered by this direction. In order to study the effect of crystallographic orientation (CO) on the characteristics of a single-crystal material, a series of tests was carried out at various temperatures under...

Comparative study of adsorption of ozone molecule on pristine and Si doped Single Wall Carbon Nanotube by density functional theory

R.G. Atram & M.R. Sonawane
We report comparative study of ozone adsorption on pristine Single Walled Carbon Nanotube (SWCNT) (8, 0) and Silicon doped Single walled Carbon Nanotube (Si – SWCNT) by density functional theory calculations based on DeMol3 code. Importance is given to the effects of silicon doping in carbon nanotube for comparative study of adsorption of ozone. The results show that silicon doping keeps the semiconducting character of pure carbon nanotubes with reduction in band gap from 0.71...

Effect of bamboo weight faction on mechanical properties in non-asbestos composite of motorcycle brake pad

Y. Sukrawan, A. Hamdani & S.A. Mardani
This study aims to determine the mechanical properties of the use of brake pads based on composite materials from bamboo fiber, and to evaluate the effect of replacement of brake pad material made from asbestos with natural materials to avoid the impacts of asbestosis substances, such as cancer. The method used several stages: weighing, mixing, inserting materials in molding, compacting, and sintering. The stages were carried out in three types of composites: Composite 1 (40%...

Dynamic fracture of ceramic plates due to impact loading. Numerical investigation

V.A. Bratov & N.A. Kazarinov
The paper presents comparative numerical analysis of two ceramic materials subjected to impact loading. ZrO2(Y2O3) and Al2O3 ceramics are studied. The main objective of the work is to study influence of various material parameters on ballistic performance of ceramic materials and on characteristics of the dynamic fragmentation process. The applied numerical scheme is based on finite element method and incubation time fracture criterion. Results on fracture surface area, residual impactor velocity, fragment size distribution are...

Neural networks and data-driven surrogate models for simulation of steady-state fracture growth

A.V. Kalyuzhnyuk, R.L. Lapin, A.S. Murachev, A.E. Osokina, A.I. Sevostianov & D.V. Tsvetkov
This work is devoted to an assessment of the application of machine learning algorithms in the prediction of a fracture's aspect ratio caused by the hydraulic fracturing. By the aspect ratio in this work is assumed the ratio of the larger half-axis of the fracture to the smaller one. The study shows the prospects of applying data-driven surrogate model methods (deep neural networks learning from data simulated by means of traditional solvers) to particle dynamics...

Supercomputing analysis of fan-shaped waves in the Earth's crust at the depth of seismic activity

V.M. Sadovskii & O.V. Sadovskaya
The high-speed process of tectonic faults formation in zones of seismic activity of the Earth's crust is analyzed in a plane strain state based on the model of elastic blocks interacting through a domino-structure under conditions of strong hydrostatic compression. Numerical simulation of the dynamics of emerging fan-shaped waves is performed by means of the developed computational algorithm and computer program for multiprocessor supercomputers of cluster architecture.

The influence of stress triaxiality on ductility of α titanium alloy in a wide range of strain rates

V.V. Skripnyak, A.A. Kozulyn & V.A. Skripnyak
This work aimed to evaluate the combined effect of stress triaxiality and strain rate on the tensile behavior of the titanium alloy. The results of experimental studies and numerical modelling of the mechanical behavior of alpha titanium alloys were received and summarized. This paper presents the results of the research of mechanical behavior of titanium alloy VT 5-1 (this is an analog of Ti-5Al-2,25Sn) in a wide range of strain rates (from 0.001 to 1000...

Modeling of elastoplastic deformation of structural steel by a trajectory containing three circles touching internally

V.G. Zubchaninov, A.A. Alekseev, V.I. Gultiaev & E.G. Alekseeva
To verify the mathematical model of the theory of processes, numerical calculations of the complex elastoplastic deformation of St3 steel along a flat curvilinear strain trajectory under combined tension-compression with torsion were carried out. The numerical calculations are compared with the experimental data obtained by the authors on the experimental complex SN-EVM on thin-walled tubular specimen. It is shown that the used mathematical model qualitatively and quantitatively satisfactorily describes the main effects of complex plastic...

Femtosecond transient absorption spectroscopy of maghemite nanoparticles loaded with gold nanoparticles

Masahiro Okazaki, Yusuke Ishii & Akihiro Furube
Photocatalytic water splitting is very useful for solar energy conversion. Iron oxides are attracting a lot of interests due to absorption in the visible region. However, iron oxides have poor conductivity. As one of solutions, the photocatalytic performance may be enhanced with loaded gold nanoparticles (Au-NP) by the characteristic optical absorption and the charge trapping nature. In this study, hybrid material of maghemite (γ-Fe2O3) and Au-NP (denoted as Au-Fe2O3) was prepared and the photo-generated carrier...

Mechanical aspects of the behavior of the surface of coated bodies when exposed to corrosive liquid

V.A. Babeshko, O.V. Evdokimova, O.M. Babeshko, V.L. Shestopalov & V.S. Evdokimov
The block element method is used to study the behavior of a coated material under the assumption that the surface is exposed to a corrosive liquid medium that can destroy the coating. It is assumed that the destruction begins with the formation of vertical local cracks in the coating, which then grow and lead to the exposure of the unprotected surface. Assuming the possibility of modeling a liquid layer by shallow water equations, the block...

Simulation of residual distributions stress in welded connection

E.E. Abashkin, A.A. Burenin, S.G. Zhilin, O.N. Komarov & A.V. Tkacheva
The search for technological options for obtaining a solid assembly with small values of deformations determines the need to use a combined thermal effect on the zone of connection of extended elements made of carbon steel. Prediction of residual stress values occurring in the heat-affected zone of an assembly is difficult because of the influence of a significant number of factors: heat removal conditions, volume and material properties, etc. To calculate the residual stresses in...

Pantographic metamaterials: a view towards applications

Francesco dell'Isola, Ivan Giorgio, Luca Placidi, Mario Spagnuolo, Patrice Peyre, Corinne Dupuy, Justin Dirrenberger, Marek Pawlikowski & Leonid Igumnov
The purpose of this article is to show the basic characteristics of the so-called pantographic metamaterial. Here we underline how the microstructure provides some exotic properties and, in principle, implies the second gradient nature of this type of metamaterial. Thanks to the development of additive manufacturing technology (especially in the field of metallurgy) we are now able to produce real samples and carry out experimental measurements to validate the proposed models. In this article we...

Structural characterization of bulk (AlXGa1-X)2O3 crystals grown by the Czochralski method

A.V. Kremleva, D.A. Kirilenko, I.G. Smirnova, V.E. Bougrov & A.E. Romanov
Results of structural characterization of (AlxGa1-x)2O3 single crystals grown from the melt with Al content x up to 0.04 are presented. Bulk (AlxGa1-x)2O3 crystals were grown by exploring the Czochralski method [1]. Transmission electron microscopy (TEM) was used to investigate defect structure of the material with various composition, X-ray diffractometry was used to measure Al content x, to inspect crystallography of the growth facets and to characterize the structure quality of the samples. Possible types...

Axial misfit stress relaxation in core-shell nanowires with hexagonal core via nucleation of rectangular prismatic dislocation loops

S.A. Krasnitckii, A.M. Smirnov, K.D. Mynbaev, L.V. Zhigilei & M.Yu. Gutkin
A theoretical model of axial misfit stress relaxation in core-shell nanowires with hexagonal cross section of the core through the nucleation of prismatic dislocation loops is suggested. Different nucleation sites of the loops in core-shell nanowires are considered. The energy change caused by the loop nucleation is calculated. The critical condition for the onset of the loops is given and analyzed in detail. The most favorable sites in nanowires and the optimal loop shape are...

Disclination models of transformation of icosaedric copper particles during their growth during electric crystallization

А.А. Vikarchuk, N.N. Gryzunova & S.S. Manokhin
For the first time, copper particles in the form of truncated micron-sized icosahedrons were experimentally obtained by electrodeposition, their morphology and internal structure were investigated. It is shown that fullerene-like copper microparticles grow from non-crystalline spherical nanoparticles and are transformed during electrocrystallization into perfect icosahedrons, which have a more stable shape and structure. The disclination models for the conversion of nanoparticles into icosahedral microparticles are developed and described.

Analysis of the degree isotropic deformation, strength and structure steel samples after severe deformation by shifting

A.P. Zhilyaev, A.G. Raab, I.S. Kodirov & G.I. Raab
The article presents the results of computer simulation and physical research of severe deformation by free torsion of long-length specimens with a round cross-section of steel 10 at a temperature of 600°C. Based on virtual approaches in the Deform 3D software package, the deformed state of the samples, including the distribution of accumulated strain in the bulk workpiece, was investigated. A physical experiment was carried out, the structure and microhardness in the longitudinal section of...

Czochralski grown (AlxGa1-x)2O3 crystals with variable Al content

P.N. Butenko, D.I. Panov, A.V. Kremleva, D.A. Zakgeim, A.V. Nashchekin, I.G. Smirnova, D.A. Bauman, A.E. Romanov & V.E. Bougrov
We propose a technuque of liquid-phase growth of (AlxGa1-x)2O3 crystals with variable and controlled Al content in them. When using the Czochralski growth process Ga2O3 melt was dosed by sapphire seed. By applying of the special growth zone and the regulating the process parameters, a series of crystal samples with Al content varying from 0.51 to 4.68 % at. was obtained. In addition to the standard setting of the geometry and weight of the crystals...

PROBING OF POLYCRYSTALLINE MAGNESIUM AT ULTRASONIC FREQUENCIES BY MECHANICAL SPECTROSCOPY

V.V. Kaminskii, Y.V. Lyubimova & A.E. Romanov
In the present work, using the method of a composite piezoelectric oscillator at a frequency of 99-102 kHz, polycrystalline magnesium was studied under two types of treatment: deformation and subsequent annealing. The influence of these types of treatments on changes in the dislocation density and such an important structurally sensitive parameter as the dynamic Young's modulus has been established. The values of micro-yield stress are determined. With a longitudinal deformation of 1.7%, at the strain...

Quantum chemical modeling bismuth-based clusters

E.N. Gribanov, O.I. Markov & Yu.V. Khripunov
The article presents the results of calculations of the structure and energy parameters of BiN : Bi8, Bi18 , Bi50 , Bi98 , Bi162 bismuth nanoclusters using quantum chemical methods. An extrapolation estimate of the number of atoms in a cluster with a zero band gap is made. The band gap width of bismuth nanoclusters passivated by Bi HmN hydrogen is calculated . The results of quantum chemical modeling of Bi Sb ( ) N...

INFLUENCE OF AGING ON FATIGUE AND CREEP PROPERTIES OF POLYURETHANE

A.R. Arutyunyan
Polymers and polymer-based materials are intensive implemented in many areas of engineering practice. These applications frequently have a very high performance demand, which makes their long-term characteristics of paramount importance. These materials were subject to degradation due to environmental factors, including light, temperature, stress, and others. Because of aging process, the physical and mechanical properties of these materials are significantly changed. This paper is devoted to the experimental investigations of this problem. The research program...

TEMPERATURE EFFECT ON THE PROCESS OF WEAR OF A FIBROUS COMPOSITE UNDER HIGH LOAD CONDITIONS

A.G. Shpenev
A model of the fibrous composite material friction and wear process is constructed taking into account the heating of the friction surface. The inhomogeneous temperature expansion of the composite components and the resulting fiber/matrix slippage near thefriction surface and the friction surface profile change is considered. The influence of temperature on the distribution of stresses in the fiber and matrix and on the roughness of the friction surface of the composite is determined.

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