Wyniki wyszukiwania - BazTech

1

Mechanic, Half-Metallic and Thermoelectric Properties of the PdZrTiAl under pressure: A DFT study

Parsamehr S., Boochani A., Sartipi E., Amiri M., Solaymani S., Naderi S., Aminian A.

Archives of Metallurgy and Materials

|

2020

|

Vol. 65, iss. 1

459--470

EN

The half-metallic, mechanical, and transport properties of the quaternary Heusler compound of PdZrTiAl is discussed under hydrostatic pressures in the range of –11.4 GPa to 18.4 GPa in the framework of the density functional theory (DFT) and Boltzmann quasi-classical theory using the generalization gradient approximation (GGA). By applying the stress, the band gap in the minor spin increases so that the lowest band is obtained 0.25 eV at the pressure of –11.4 GPa while the maximum gap is calculated 0.9 eV at the pressure of 18.4 GPa. In all positive and negative pressures, the PdZrTiAl composition exhibits a half-metallic behavior 100% spin polarization at the Fermi level. It is also found that applying stress increases the Seebeck coefficient in both spin directions. In the minority spin, the n-type PdZrTiAl, the power factor (PF) for all the cases is greater in the equilibrium state than the strain and stress conditions whereas in the majority spin, the PF value of the stress state is greater than the other two. The non-dimensional figure of merit (ZT) is significant and is about one in spin down in the room temperature for the all pressure states that it remains on this value by applying pressure. The obtained elastic constants indicate that the PdZrTiAl crystalline structure has a mechanical stability. Based on the Yong (E), Bulk (B) and shear (G) modulus and Poisson (n) ratio, the brittle-ductile behavior of this compound has been investigated under pressure. The results indicate that PdZrTiAl has a ductile nature and it is a stiffness compound in which elastic and mechanical instability increases by applying strain.

2

Elastic Constants by Resonant Ultrasound Spectroscopy – Application to Thermoelectrics and Aluminum Alloys

Klobes Benedikt

Scientific Journal of Gdynia Maritime University

|

2019

|

nr 112

60--68

EN

Resonant ultrasound spectroscopy is a non-destructive technique for determining the elastic constants of a material. In the context of thermoelectric materials, elastic constants can be used to investigate the speed of sound and, thus, the lattice thermal conductivity of a substance. For Mg2Si-Mg2Sn solid solutions, a possible connection between shear modulus and band convergence can be assumed in that way. Moreover, the rather low speed of sound in this system points towards a high contribution of optical phonons to thermal conductivity. Additionally, significant resonance frequency shifts are observed during natural aging of technical Al-Cu-Mg and Al-Mg-Si alloys, which are proposed to assist investigation of the early stages of clustering in the future.

3

Influence of moisture content on elastic constants of Scots pine wood subjected to compression

Güntekin Ergun, Akar Serhat

Drewno : prace naukowe, doniesienia, komunikaty

|

2019

|

vol. 62, nr 204

41--53

EN

Moisture content is the environmental factor that has the greatest influence on the physical and mechanical properties of wood materials. This research aimed to quantify the effect of moisture content on the elastic constants of Scots pine wood grown in Turkey under different humidity regimes. The elastic properties investigated include EL, ER, ET, GLR, GLT, GRT, ʋLR, ʋLT, ʋRL, ʋRT, ʋTL and ʋTR under compression. The compression strength in all principal directions was also studied. Specimens were cut from sapwood of pine logs and sorted into four matched MC groups. Clear wood samples were conditioned at 21°C and 45%, 65%, 85%, 95% RH, and subjected to compression tests. A biaxial extensometer was used to measure active and passive strain during loading. Young’s modulus, shear modulus, Poisson’s ratios and compression strength were calculated and compared for all orthotropic directions. The results indicate that the elastic and strength properties are significantly different in the principal directions. The Young’s modulus, shear modulus and compression strength of the tested samples were strongly affected by moisture content. These properties exhibit a linear decrease with increasing moisture content. Poisson’s ratios are not sensitive to MC changes.

4

Structural, Mechanical and Thermodynamic Properties Under Pressure Effect of Rubidium Telluride: First Principle Calculations

Bidai K., Ameri M., Ameri I., Bensaid D, Slamani A., Zaoui A., Al-Douri Y.

Archives of Metallurgy and Materials

|

2017

|

Vol. 62, iss. 2A

865--871

EN

First-principles density functional theory calculations have been performed to investigate the structural, elastic and thermodynamic properties of rubidium telluride in cubic anti-fluorite (anti-CaF2-type) structure. The calculated ground-state properties of Rb2Te compound such as equilibrium lattice parameter and bulk moduli are investigated by generalized gradient approximation (GGA-PBE) that are based on the optimization of total energy. The elastic constants, Young’s and shear modulus, Poisson ratio, have also been calculated. Our results are in reasonable agreement with the available theoretical and experimental data. The pressure dependence of elastic constant and thermodynamic quantities under high pressure are also calculated and discussed.

5

First principles investigations of HgX (X=S, Se and Te)

Düz I., Erdem I., Ozdemir Kart S., Kuzucu V.

Archives of Materials Science and Engineering

|

2016

|

Vol. 79, nr 1

5--11

EN

Purpose: The aim of this study is to determine the structural, and mechanical properties of Hg chalcogenide materials (HgX; X=S, Se, Te) in the zinc-blende structure which are presented as promising candidates for modern optoelectronic and spintronic applications. The dependence of elastic constants of pressure for three materials are evaluated. Moreover, isotropic mechanical properties such as bulk modulus, shear modulus, Young’s modulus and Poisson’s ratio are obtained. Design/methodology/approach: First principles calculations based on Density Functional Theory are performed by employing Projector Augmented Waves potentials. The electronic exchange and correlation function is treated by using Generalized Gradient Approximation parametrized by Perdew, Burke and Ernzerhof (PBE96). Findings: Calculated results of structural and mechanical properties are in good agreement with those of experimental and other theoretical studies. This three materials in zinc-blende structure are mechanically stable. İsotropic mechanical properties are also obtained. Resistance against both linear strain and shear strain and ductility decrease as we go into the sequence of HgS−>HgSe−>HgTe. The wave velocities and Debye temperatures calculated for this materials. Debye temperatures are founded for HgS, HgSe and HgTe as 306.21 K, 264.30 K and 240.19 K, respectively Research limitations/implications: Calculation speeds of the computers and data storage are some limitations. Also, the lack of experimental data hinder for the comparison of our results. Practical implications: Obtaining high pressure elastic constants by calculations is preferable since it is very difficult or even impossible to measure them by experimentally. Originality/value: There are only restricted number of investigation of elastic constants of mercury chalcogenides both theoretically and experimentally.

6

FP-LAPW investigation of mechanical and thermodynamic properties of Na2X (X = S and Se) under pressure and temperature effects

Bidai K., Ameri M., Bensaid D, Moulay N. E., Al-Douri Y., Ameri I.

Materials Science Poland

|

2015

|

Vol. 33, No. 3

649--659

EN

Structural, elastic and thermodynamic properties of sodium chalcogenides (Na2X, X = S, Se) have been calculated using FP-APW+lo method. The ground state lattice parameter, bulk moduli have been obtained. The Zener anisotropy factor, Poisson’s ratio, shear modulus, Young’s modulus, have also been calculated. The calculated structural and elastic constants are in good agreement with the available data. We also determined the thermodynamic properties, such as heat capacities Cv and Cp, thermal expansion α, entropy S, and Debye temperature ΘD, at various pressures and temperatures for Na2X compounds. The elastic constants under high pressure and temperature are also calculated and elaborated.

7

Ab-initio study of structural, elastic, electronic and thermodynamic properties of BaxSr1-xS ternary alloys

Chelli S., Touam S., Hamioud L., Meradji H., Ghemid S., Hassan F. E.

Materials Science Poland

|

2015

|

Vol. 33, No. 4

879--886

EN

The structural, elastic, electronic and thermodynamic properties of BaxSr1-xS ternary alloys have been investigated using the full-potential (linearized) augmented plane wave method. The ground state properties, such as lattice constant, bulk modulus and elastic constants, are in good agreement with numerous experimental and theoretical data. The dependence of the lattice parameters, bulk modulus and band gap on the composition x was analyzed. Deviation of the lattice constant from Vegard's law and the bulk modulus from linear concentration dependence (LCD) was observed. The microscopic origins of the gap bowing were explained by using the approach of Zunger et al. The thermodynamic stability of BaxSr1-xS alloy was investigated by calculating the excess enthalpy of mixing, Delta H-m and the calculated phase diagram showed a broad miscibility gap with a critical temperature.

8

Elastic modules identification by layered composite beams testing

Diveyev B., Konyk S.

Journal of Achievements in Materials and Manufacturing Engineering

|

2015

|

Vol. 72, nr 1

14--22

EN

Purpose: The study aims to predict elastic properties of composite laminated plates from the measured mechanical properties. Design/methodology/approach: Elastic constants of laminates and damping properties have been determined by using an identification procedure based on experiment design, and multi-level theoretical approach. Findings: The present paper is the first attempt at proposing a novel adaptive procedure to derive stiffness parameters from forced sandwich plate’s vibration experiments. Research limitations/implications: In the future the extension of the present approach to sandwich plates with different core materials will be performed in order to test various experimental conditions. Practical implications: Structures composed of laminated materials are among the most important structures used in modern engineering and especially in the aerospace industry. Such lightweight and highly reinforced structures are also being increasingly used in civil, mechanical and transportation engineering applications. Originality/value: The main advantage of the present method is that it does not rely on strong assumptions on the model of the plate. The key feature is that the raw models can be applied at different vibration conditions of the plate by a suitable analytical ore approximation method

9

Determination of the Elastic Constants of Plain Woven Fabrics by a Tensile Test in Various Directions

Penava Ž., Šimić-Penava D, Knezic Ž

Fibres & Textiles in Eastern Europe

|

2014

|

Vol. 22, no. 2 (104)

57--63

EN

In this paper the values of elastic constants of woven fabrics for different angles of extension direction were analysed. Four types of fabric samples of different raw material composition and the same type of weave were tested under tensile forces in seven directions oriented with a 15° increment with respect to the weft direction. The elasticity modulus and Poisson’s ratio of the woven fabrics were determined experimentally in a laboratory. Based on the experimentally obtained values, theoretically calculated elastic constants for arbitrarily chosen fabric directions were calculated. A good agreement between the experimental results and values of the elastic constants calculated was shown, hence the theoretical equations can be used with high accuracy to calculate the elastic constants of fabric in various directions. Therefore the measurements need to be undertaken when the tensile force is acting on the fabric only in the warp, weft and at an angle of 45°.

PL

W pracy przeanalizowano stałe elastyczności tkanin rozciąganych pod różnymi kątami. Badano próbki wykonane z różnych materiałów ale o tym samym splocie. Próbki rozciągano w kierunkach o przesunięciu co 150 licząc od kierunku wątku. Badano moduł elastyczności i współczynnik Poissona. Testy przeprowadzono w warunkach laboratoryjnych. Korzystając z wyników eksperymentów przeprowadzono teoretyczne obliczenia stałych elastyczności dla wybranych kierunków rozciągania. Stwierdzono dobrą zgodność wyników, dzięki czemu można wyciągnąć wniosek, że zastosowane wzory mogą służyć do obliczeń stałych elastyczności z dużą dokładnością. Dlatego pomiary takie powinny być przeprowadzane jeżeli siły rozciągające tkaninę działają tylko w kierunku osnowy, wątku i pod kątem 45 stopni.

10

Nanomechanical Properties of Metallic fcc Nanorods from Molecular Simulations with the Sutton-Chen Force Field

Białoskorski M., Rybicki J.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

|

2012

|

Vol. 16, No 1-2

97-133

EN

Basic elastic constants (Young’s modulus, Poisson’s ratio, shear modulus) were determined for several monocrystalline, metallic (Ni, Cu, Pt, Au) nanorods using molecular dynamics with the Sutton-Chen force field. Stress-strain curves were also calculated and discussed.

11

Measurement of elastic constants of nematic liquid crystals with use of hybrid in-plane-switched cell

Nowinowski-Kruszelnicki E., Kędzierski J., Raszewski Z., Jaroszewicz L., Kojdecki M. A., Piecek W., Perkowski P., Olifierczuk M., Miszczyk E., Ogrosnik K., Morawiak P.

Opto-Electronics Review

|

2012

|

Vol. 20, No. 3

255-259

EN

A new method for quick and pretty accurate measurements of splay, twist and bend elastic constants of nematic liquid crystals is experimentally verified. The main concept relies on exploiting only the electric field and determining magnitudes of nematic elastic constants from threshold fields for Freedericksz transitions in only one hybrid in-plane-switched cell. In such cell the deformations of an investigated liquid crystal are controlled by three separated pairs of electrodes confining measurement domains. In two of them inter-digital electrodes are mounted on one cell cover. Splay, twist and bend elastic constants can be measured by a proper choice of electrodes' configuration together with orienting cover coatings (without applying magnetic fields). In this paper, we describe layout of our cells and results of experimental tests by using different liquid crystals: 5CB and 6CHBT (with positive dielectric anisotropy), Demus' esters (with negative dielectric anisotropy) and new liquid crystals mixtures produced in our university.

12

A method for correction of elastic and piezoelectric constants of crystals using measured surface acoustic wave parameters

Brzozowski E.

Materiały Elektroniczne

|

2011

|

T. 39, nr 2

8-13

EN

Surface acoustic wave (SAW) properties of a crystal depend on the density, elastic, piezoelectric and dielectric constants.On the basis of literature data, calculations of SAW parameters in a neodymium calcium oxoborate [NdCa4O(BO3)3] crystal were carried out to evaluate orientations optimal for the correction of elastic and piezoelectric constants. SAW velocities and electromechanical coupling coefficients were measured using SAW delay lines deposited on differently oriented crystal substrates. Dielectric constants were determined from measured effective permittivities. Both a nonlinear least squares algorithm and a computer program for the correction of elastic and piezoelectric constants from measured SAW velocities and electromechanical coupling coefficients were developed. The correction of NdCa4O(BO3)3 elastic and piezoelectric constants was carried out. It was shown that for the corrected constants the differences between the measured and calculated SAW parameters are marginal.

PL

Własności akustycznych fal powierzchniowych (AFP) w rysztale zależą od gęstości stałych elastycznych, piezoelektrycznych i dielektrycznych. Na podstawie danych z literatury obliczono parametry AFP w krysztale tlenoboranu neodymowo wapniowego [NdCa4O(BO3)3] w celu wyznaczenia orientacji optymalnych do korekcji stałych. Zmierzono prędkości i współczynniki sprzężenia elektromechanicznego AFP z wykorzystaniem linii opóźniających osadzonych na podłożach NdCa4O(BO3)3 o różnych orientacjach. Wyznaczono stałe dielektryczne z pomiaru przenikalności elektrycznych. Opracowano metodę korekcji stałych elastycznych i piezoelektrycznych wykorzystującą nieliniowy algorytm najmniejszych kwadratów i zmierzone parametry AFP. Przeprowadzono korekcję stałych elastycznych i piezoelektrycznych kryształu NdCa4O(BO3)3. Wykazano, że dla stałych skorygowanych różnice między zmierzonymi, a obliczonymi parametrami AFP są bardzo małe.

13

Numerical homogenization of polymer/clay nanocomposites by the boundary element method

Ptaszny J., Fedeliński P.

Archives of Mechanics

|

2011

|

Vol. 63, nr 5-6

517-517

EN

The paper deals with the numerical homogenization of polymer/clay nanocomposites by using the boundary element method (BEM). The reinforcement has the form of stacks of parallel clay sheets modelled by effective isotropic particles. Two-dimensional representative volume elements (RVEs), containing randomly distributed parallel rectangular particles, are modelled and five plane-strain elastic constants of the orthotropic composite are analysed: two Young’s moduli, shear modulus and two Poisson’s ratios. The results are compared to experimental data, finite element method (FEM) results, and analytical models as well. The positive-definiteness and symmetry of the apparent compliance matrix are verified. All the comparisons and tests confirm validity of the applied method.

14

Application possibilities of nanoparticles for modification of parameters of liquid crystal materials

Hotra Z., Mykytyuk Z., Fechan A., Sushynskyy O., Yasynovska O., Kotsun V., Levenets V., Kalita W., Błąd G.

Elektronika : konstrukcje, technologie, zastosowania

|

2010

|

Vol. 51, nr 8

125-128

EN

The influence of different kinds of nanoparticles on the electrical characteristics of induced cholesterics based on 5CB and 1289 nernatic matrix with the addition of chiral dopant has been experimentally investigated. The effects of nanoparticles on the dielectric properties of liquid crystal materials were detected and analyzed.

PL

W pracy zaprezentowano wyniki badań nad wpływem domieszkowania różnego typu nanoczasteczek na charakterystyki cholesteryków na bazie materiałów nematycznych. Przeanalizowano również właściwości dielektryczne materiałów ciekłokrystalicznych po domieszkowaniu.

15

Numerical investigation of influence of ionic space charge and flexoelectric polarization on measurements of elastic constants in nematic liquid crystals

Buczkowska M., Derfel G., Konowalski M.

Opto-Electronics Review

|

2009

|

Vol. 17, No. 2

95-98

EN

Deformations of nematic layers caused by magnetic field allow determination of the elastic constants of liquid crystal. In this paper, we simulated numerically the deformations of planar and homeotropic nematic layers. The flexoelectric properties of the nematic and presence of ions were taken into account. Our aim was to show the influence of flexoelectricity on the results of the real measurement of the elastic constants k33 and k11. In these simulations, we calculated the optical phase difference Δ Φ between the ordinary and extraordinary rays of light passing through the layer placed between crossed polarizers as a function of the magnetic field induction B. One of the elastic constants can be calculated from the magnetic field threshold for deformation. The ratio k33/k11 can be found by means of fitting theoretical ΔΦ(B) dependence to the experimental results. The calculations reveal that the flexoelectric properties influence the deformations induced by the external magnetic field. In the case of highly pure samples, this may lead to false results of measurement of the elastic constants ratio k33/k11

16

Acoustical investigations of uranium chalcogenides

Singh R. K., Pandey K. K., Singh M. P., Singh R. P.

Materials Science Poland

|

2009

|

Vol. 27, No. 4/1

1041--1053

EN

Ultrasonic attenuation due to phonon-phonon interaction and thermoelastic loss was evaluated in uranium chalcogenides viz. UX, X= S, Se, Te in fcc phase in the temperature range 50-600 K for longitudinal and shear waves along the <100>, <110> and <111> directions of propagation. Electrostatic and Born-Mayer repulsive potentials were used to obtain second and third order elastic constants, taking the nearest neighbour distance and hardness parameter as the input data. Second and third order elastic constants (obtained at various temperatures) were used to obtain the Gruneisen parameters and non-linearity or anisotropy parameters, which in turn were used to evaluate the ultrasonic attenuation coefficient over the frequency square due to phonon-phonon interaction, (?/f 2)p-p in the Akhiezer regime. It has been found that at lower temperatures ?/f 2 increases rapidly with temperature, and at higher temperatures the rate of increase becomes small. Contribution to the total attenuation due to thermoelastic loss is negligible in comparison with that of phonon-phonon interaction, i.e. a major part of the energy from the sound wave is removed, due to interaction of acoustic phonons with thermal phonons (lattice vibrations).

17

Structure and Ultrasonic Properties of Vanadium Tellurite Glasses Containing Copper Oxide

Abd El-Aal N. S., Afifi H. A.

Archives of Acoustics

|

2009

|

Vol. 34, No. 4

641-654

EN

The elastic properties of vanadium tellurite glasses, 65TeO2-(35-x) V2O5-xCuO, with different compositions of Copper (x = 7.5 to 17.5 mol% in steps of 2.5 mol%) have been studied at room temperature (300 K). The ultrasonic velocity measurements have been made, using a transducer having resonating frequency of 4 MHz (both longitudinal and shear). The density, molar volume, and ultrasonic velocities show interesting features, which are used to explore the structural changes in the network. Elastic moduli, Poisson ratio, crosslink density, Microhardnes, and Debye temperature of the glasses have been determined using the experimental data. The composition dependence of the elastic properties explores useful information about the physical properties of the vanadium tellurite glasses doped with Copper. Quantitative analysis has been carried out in order to obtain more information about the structure of the glass under the study, based on bond compression model and the Makishima & Mackenzie model. The observed results through ultrasonic nondestructive evaluation, investigate the structural changes and mechanical properties of the glass.

18

Flexoelectric effect modelling

Kapanowski A.

Opto-Electronics Review

|

2008

|

Vol. 16, No. 4

375-378

EN

A statistical theory of dipole flexoelectric (FE) polarization in liquid crystals is used to calculate temperature dependence of order parameters, elastic constants and FE coefficients. Two systems with polar wedge-shaped and banana-shaped molecules are investigated. In both cases, the FE coefficients are proportional to the dipole moment component parallel to the molecule symmetry axis. It results from the symmetries of interactions and of the Mayer function. The origin of the FE effect and microscopic pictures of the distorted phases are discussed.

19

Influence of size polydispersity on the elastic constants of F.C.C. crystals of static soft spheres

Narojczyk J W, Wojciechowski K W

Materials Science Poland

|

2008

|

Vol. 26, No. 4

1001--1007

EN

Elastic constants of three-dimensional systems of soft spheres, interacting through n-inverse power potential and exhibiting aperiodicity (caused by the size polydispersity of the spheres), have been determined at 0 K by computer simulations. It has been shown that Poisson’s ratio, as well as other elastic constants, increase with increasing disorder in the system at a fixed number density of spheres.

20

Pomiary ultradźwiękowe stałych sprężystości. Praktyka i teoria

Wilczyński A. P.

Prace Naukowe Politechniki Warszawskiej. Mechanika

|

2007

|

z. 219

213--228

PL

Przedstawiona praca omawia część zagadnień związanych z pracami projektowymi, wykonawstwem i użytkowaniem stanowiska pomiarowego, podstawami teoretycznymi procesu, technikami obliczeniowymi oraz z szeregiem innych problemów występujących w praktyce. Praca powstała przy wyznaczaniu stałych materiałowych anizotropowych kompozytów polimerowych, jednak zastosowane metody mogą być użyteczne przy badaniu także innych materiałów.

EN

The paper presents some considerations on ultrasonic measurement techniques, giving the foundations of the method, theoretical background, outlines of the numerical treatment and given some practical solutions to some of the problems In experimentation. The has been however prepared while considering an application to measurements of elastic constants of polymeric composites, but the presented approach is general and can be useful for any given material.