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interfacial-energy
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Study of the mechanism of methyl iodide decomposition on Cu(110) surface: A UBI-QEP-based approach
, Article Langmuir ; Volume 17, Issue 3 , 2001 , Pages 583-587 ; 07437463 (ISSN) ; Gobal, F ; Sharif University of Technology
2001
Abstract
The decomposition of methyl iodide on Cu(110) surface gives rise to the production of methane, ethane, and ethene over a wide range of its surface coverage. In this work a reaction mechanism based on the adsorption and subsequent surface dissociation(s) of methyl iodide followed by the recombination and desorption of the surface entities are proposed on the basis of the energetic criteria provided by the unity bond index-quadratic exponential potential method. To further amplify the arguments using the calculated activation energies of the surface reactions, desorptions, etc., the Arrhenius factor is obtained by simulation of the temperature-programmed desorption patterns fitted to the...
Role of interfacial fracture energy and laminate architecture on impact performance of aluminum laminates
, Article Composites Part A: Applied Science and Manufacturing ; Volume 39, Issue 11 , 2008 , Pages 1685-1693 ; 1359835X (ISSN) ; Bagheri, R ; Mahmudi, R ; Sharif University of Technology
2008
Abstract
The impact behavior of aluminum/epoxy laminates was studied by changing the number of layers and the interface strength. It should be noted that although the overall thickness did not changed, the individual layers decreased in thickness when the number of layers increased. The results indicate that the impact resistance of the laminate increases with the number of layers, while the interface strength has a less pronounced influence (50%) on the impact resistance of the laminate. It is also deducted that if the ratio of layer thickness to plastic zone size is smaller than or equal to 1, the impact behavior of the laminates is sensitive to the interface strength. © 2008 Elsevier Ltd. All...
Surface energy effects on the yield strength of nanoporous materials containing nanoscale cylindrical voids
, Article Mechanics of Materials ; Volume 42, Issue 9 , September , 2010 , Pages 852-862 ; 01676636 (ISSN) ; Avazmohammadi, R ; Naghdabadi, R ; Sharif University of Technology
2010
Abstract
Surfaces and interfaces behave differently from their bulk counterparts especially when the dimensions approach small scales. The recent studies have shown that the surface/interface free energy (surface stress) plays an important role in the effective mechanical properties of solids with nanosized inhomogeneities. In this work, within a micromechanical framework, the effect of surface stress is taken into account to obtain a macroscopic yield function for nanoporous materials containing cylindrical nanovoids. Gurtin-Murdoch model of surface elasticity is incorporated in the generalized self-consistent method to obtain a closed-form expression for the transverse shear modulus of transversely...
Surface elasticity revisited in the context of second strain gradient theory
, Article Mechanics of Materials ; Volume 93 , 2016 , Pages 220-237 ; 01676636 (ISSN) ; Shodja, H. M ; Sharif University of Technology
Elsevier
Abstract
Surface/interface stresses, when notable, are closely associated with a surface/interface layer in which the interatomic bond lengths and charge density distribution differ remarkably from those of the bulk. The presence of such topographical defects as edges and corners amplifies the noted phenomena by large amounts. If the principal features of interest are such studies as the physics and mechanics of evolving microscopic-/nanoscopic-interfaces and the behavior of nano-sized structures which have a very large surface-to-volume ratio, traditional continuum theories cease to hold. It is for the treatment of such problems that augmented continuum approaches like second strain gradient and...
On thermoelastic fields of a multi-phase inhomogeneity system with perfectly/imperfectly bonded interfaces
, Article International Journal of Solids and Structures ; Volume 45, Issue 22-23 , 2008 , Pages 5831-5843 ; 00207683 (ISSN) ; Mohammadi Shodja, H ; Sharif University of Technology
2008
Abstract
The stress fields of cylindrical and spherical multi-phase inhomogeneity systems with perfect or imperfect interfaces under uniform thermal and far-field mechanical loading conditions are investigated by use of the Boussinesq displacement potentials. The radius of the core inhomogeneity and the thickness of its surrounding coatings are arbitrary. The discontinuities in the tangential and normal components of the displacement at the imperfect interfaces are assumed to be proportional to the associated tractions. In this work, for the problems where the phases of the inhomogeneity system are homogeneous, the exact closed-form thermo-elastic solutions are presented. These solutions along with a...
Correlation between surface roughness and hydrophobicity of GLAD RF sputtered PTFE/W/Glass nanorod thin films
, Article Vacuum ; Vol. 101, issue , March , 2014 , p. 279-282 ; Ebrahimi, M ; Moshfegh, A. Z ; Sharif University of Technology
Abstract
In this research, we have used glancing angle deposition (GLAD) RF sputtering technique with various angular speeds ranging from 5 to 30 RPM to fabricate polytetrafluoroethylene (PTFE, Teflon) coated Tungsten on glass substrate for producing hydrophobic surface. According to scanning electron microscopy (SEM) observations, Tungsten nanorods were formed on the substrate with average diameter and length of about ∼50 nm and 300 nm, respectively. Hydrophobic property of W/Glass and PTFE/W/Glass systems was investigated by water contact angle measurements and we have found that the contact angle varied with the substrate angular speed. Maximum contact angle of 121 was measured for the...
A combined first principles and analytical determination of the modulus of cohesion, surface energy, and the additional constants in the second strain gradient elasticity
, Article International Journal of Solids and Structures ; Volume 50, Issue 24 , 2013 , Pages 3967-3974 ; 00207683 (ISSN) ; Shodja, H. M ; Sharif University of Technology
2013
Abstract
Mindlin's (1965) second strain gradient theory due to its competency in capturing the effects of edges, corners, and surfaces is of particular interest. Formulation in this framework, in addition to the usual Lamé constants, requires the knowledge of sixteen additional materials constants. To date, there are no successful experimental techniques for measuring these material parameters which reflect the discrete nature of matter. The present work gives an accurate remedy for the atomistic calculations of these parameters by utilizing the first principles density functional theory (DFT) for the calculations of the atomic force constants combined with an analytical formulation. It will be shown...
Effects of surface residual stress and surface elasticity on the overall yield surfaces of nanoporous materials with cylindrical nanovoids
, Article Mechanics of Materials ; Volume 51 , 2012 , Pages 74-87 ; 01676636 (ISSN) ; Naghdabadi, R ; Asghari, M ; Sharif University of Technology
Elsevier
2012
Abstract
Mechanical properties of a material near the surfaces and interfaces are different from those of the same material far from the surfaces/interfaces. The effect of this difference on the effective mechanical properties of heterogeneous materials becomes significant when the size of inhomogeneities is at the scale of nanometers. In this article, within a micromechanical framework, the effects of surface residual stress and surface elasticity are taken into account to obtain a macroscopic size-dependent yield function for nanoporous materials containing aligned cylindrical nanovoids. Based on the modified Hill's condition, the strains are decomposed into two parts, a part due to the external...
A combined first principles and analytical treatment for determination of the surface elastic constants: Application to Si(001) ideal and reconstructed surfaces
, Article Philosophical Magazine Letters ; Volume 92, Issue 1 , Sep , 2012 , Pages 7-19 ; 09500839 (ISSN) ; Shodja, H. M ; Sharif University of Technology
2012
Abstract
Behavior of nanostructures, which are characterized by a large surface-to-volume ratio, is greatly influenced by their surface parameters, such as surface elastic moduli tensor. Accurate determination of the surface elastic constants by first principles is of particular interest. To this end, through consideration of the fundamental thermodynamic arguments for free solid surfaces, an analytical formulation for the change in specific Helmholtz surface free energy is developed. Relating this formulation to the corresponding energy calculated via first principles leads to the determination of the surface elastic moduli tensor. The surface mechanical properties, namely surface energy, surface...
Effect of chemical treatment of Teflon powder on the properties of polyamide 66/Teflon composites prepared by melt mixing
, Article Macromolecular Research ; Volume 19, Issue 6 , June , 2011 , Pages 613-621 ; 15985032 (ISSN) ; Gholamalipour, S ; Sharif University of Technology
2011
Abstract
The surface defluorination of Teflon in powdery form was performed using a chemical treatment. The reaction parameters including the reaction time, sodium, naphthalene concentrations were optimized using a Taguchi method to obtain maximum functionality on the particles surface. The surface functionality of the treated particles was analyzed by FTIR, energy dispersive X-ray analysis (EDX) and surface energy. Both treated (g-PTFE) and untreated (PTFE) Teflon were added to polyamide 66 (PA66) at various loadings up to 6 wt%. Mechanical, differential scanning calorimetry (DSC) and tribological analyses for different PA66/Teflon composites were carried out. The chemical treatment enhanced the...
Investigation of size effects on the physical properties of one-dimensional ising models in nanosystems
, Article Molecular Physics ; Volume 109, Issue 3 , Feb , 2011 , Pages 385-395 ; 00268976 (ISSN) ; Daryaei, E ; Parsafar, G ; Fortunelli, A ; Sharif University of Technology
2011
Abstract
Ising models in nanosystems are studied in the presence of a magnetic field. For a one-dimensional (1-D) array of spins interacting via nearest-neighbour and next-nearest-neighbour interactions we calculate the heat capacity, the surface energy, the finite-size free energy and the bulk free energy per site. The heat capacity versus temperature exhibits a common wide peak for systems of any size. A small peak also appears at lower temperatures for small arrays when the ratio of magnetic field spin interaction energy over the nearest-neighbour spin-spin interaction energy, f, is within 0 < F ≤ 0.10 . The peak becomes smaller for longer array and eventually vanishes for long arrays,...
Wettability properties of PTFE/ZnO nanorods thin film exhibiting UV-resilient superhydrophobicity
, Article Applied Surface Science ; Volume 341 , 2015 , Pages 92-99 ; 01694332 (ISSN) ; Ebrahimi, M ; Nourmohammadi, A ; Moshfegh, A. Z ; Sharif University of Technology
Elsevier
2015
Abstract
In this research, initially anodization process was used to fabricate ZnO nanorods on Zn substrate and then RF sputtering technique was applied to grow a thin layer of polytetrafluoroethylene (PTFE, Teflon) on the coated ZnO nanorods for producing a superhydrophobic surface. According to scanning electron microscopy (SEM) observations, ZnO nanorods were formed with average diameter and length of about ∼180 nm and 14 μm, respectively. Superhydrophilic property of ZnO nanorods and superhydrophobic property of PTFE/ZnO nanorods was investigated by water contact angle (WCA) measurements. It was found that the contact angle varied with the PTFE deposition time. The highest contact angle...
Rheological and mechanical characteristics of low density polyethylene/ethylene-vinyl acetate/organoclay nanocomposites
, Article Polymer Engineering and Science ; Volume 50, Issue 7 , March , 2010 , Pages 1315-1325 ; 00323888 (ISSN) ; Shojaei, A ; Sheikh, N ; Sharif University of Technology
2010
Abstract
Attempts were made to trace the effect of organoclay (OC) on the rheological and mechanical behaviors of the low density polyethylene (LDPE)/ethylene-vinyl acetate (EVA) blends. To do this effectively, in addition to LDPE/EVA/OC system, pure LDPE and LDPE/EVA blends were also examined as model systems. The rheological behavior was determined by the capillary rheometer. Morphological characterization was also carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and theoretical approach based on interfacial energies. Shear viscosity, tensile strength and elastic modulus of LDPE/EVA were found to decrease by increasing the EVA...
Surface free energy of platinum nanoparticles at zero pressure: A molecular dynamic study
, Article Solid State Communications ; Volume 150, Issue 5-6 , February , 2010 , Pages 254-257 ; 00381098 (ISSN) ; Abroshan, H ; Parsafar, G. A ; Sharif University of Technology
2010
Abstract
Metallic nanoparticles are interesting because of their use in catalysis and sensors. The surface energy of the FCC platinum nanoparticles are investigated via molecular dynamics simulation using Quantum Sutton-Chen (QSC) potential. We have calculated the Gibbs free energy for the FCC platinum bulk and also for its nanoparticle. All calculations have been carried out at zero pressure. We have used the thermodynamic integration method to obtain the Gibbs free energy. The total Gibbs free energy is taken as the sum of its central bulk and its surface free energy. We have calculated the free energy of a platinum nanoparticle as a function of temperature
Roll bonding of AA5052 and polypropylene sheets: bonding mechanisms, microstructure and mechanical properties
, Article Journal of Adhesion ; 2016 , Pages 1-25 ; 00218464 (ISSN) ; Akbarzadeh, A ; Sharif University of Technology
Taylor and Francis Inc
2016
Abstract
Structural, microstructural and mechanical properties in roll bonding of AA5052 and polypropylene sheets have been evaluated in this study. The surface roughness of the AA5052 sheets, rolling temperature and the surface energy of polymer were selected as the bonding variables. The findings indicated that an increase in the surface energy of polypropylene by grafting maleic anhydride would result in higher bonding strength due to chemical interaction between the AA5052 and the maleic anhydride grafted polypropylene (PP-g-MAH). In fact, this reaction caused the formation of an interphase layer at the polymer side of the interface and the diffusion of aluminum into the PP-g-MAH layer. It was...
Roll bonding of AA5052 and polypropylene sheets: bonding mechanisms, microstructure and mechanical properties
, Article Journal of Adhesion ; Volume 93, Issue 7 , 2017 , Pages 550-574 ; 00218464 (ISSN) ; Akbarzadeh, A ; Sharif University of Technology
Taylor and Francis Inc
2017
Abstract
Structural, microstructural and mechanical properties in roll bonding of AA5052 and polypropylene sheets have been evaluated in this study. The surface roughness of the AA5052 sheets, rolling temperature and the surface energy of polymer were selected as the bonding variables. The findings indicated that an increase in the surface energy of polypropylene by grafting maleic anhydride would result in higher bonding strength due to chemical interaction between the AA5052 and the maleic anhydride grafted polypropylene (PP-g-MAH). In fact, this reaction caused the formation of an interphase layer at the polymer side of the interface and the diffusion of aluminum into the PP-g-MAH layer. It was...
Characterization of silicon surface elastic constants based on different interatomic potentials
, Article Thin Solid Films ; Volume 626 , 2017 , Pages 104-109 ; 00406090 (ISSN) ; Rezaei, S ; Sharif University of Technology
Abstract
Mechanical properties of materials are an important factor in designing nanoscale systems. Several researches and experiments have shown that the mechanical properties of the nano-scale materials are different from those of bulk. One of the major reasons for this difference is that the ratio of surface to volume increases at the nano-scale, and the effects of free surfaces become very important. In this paper, we have measured the surface elastic constants of silicon crystalline structure using different interatomic potentials. The potentials employed here are EDIP (Environment-Dependent Interatomic Potential), Stillinger-Weber and Tersoff, and also different crystalline orientations are...
Surface characterization of face-centered cubic crystals
, Article Mechanics of Materials ; Volume 129 , 2019 , Pages 15-22 ; 01676636 (ISSN) ; Enzevaee, C ; Sharif University of Technology
Elsevier B.V
2019
Abstract
To date, the examination of surface energy and surface layer relaxation has been the subject of several experimental and simulation works, whereas evaluation of surface residual stresses and surface elastic constants has received very little attention. In addition to the fundamental importance of these properties in the understanding of such phenomena as crystal equilibrium shape, surface roughening and segregation, they are also crucial for use in the theoretical studies based on continuum theory of elastic material surfaces. This work focuses on developing a theoretical approach for the calculations of the surface residual stress and surface elastic constants for (100) planes of fcc...
Surface characterization of face-centered cubic crystals
, Article Mechanics of Materials ; Volume 129 , 2019 , Pages 15-22 ; 01676636 (ISSN) ; Enzevaee, C ; Sharif University of Technology
Elsevier B.V
2019
Abstract
To date, the examination of surface energy and surface layer relaxation has been the subject of several experimental and simulation works, whereas evaluation of surface residual stresses and surface elastic constants has received very little attention. In addition to the fundamental importance of these properties in the understanding of such phenomena as crystal equilibrium shape, surface roughening and segregation, they are also crucial for use in the theoretical studies based on continuum theory of elastic material surfaces. This work focuses on developing a theoretical approach for the calculations of the surface residual stress and surface elastic constants for (100) planes of fcc...
Surface and interface effects on torsion of eccentrically two-phase fcc circular nanorods: Determination of the surface/interface elastic properties via an atomistic approach
, Article Journal of Applied Mechanics, Transactions ASME ; Volume 78, Issue 1 , October , 2011 , Pages 0110111-01101111 ; 00218936 (ISSN) ; Shodja, H. M ; Sharif University of Technology
2011
Abstract
The effect of surface and interface elasticity in the analysis of the Saint-Venant torsion problem of an eccentrically two-phase fcc circular nanorod is considered; description of the behavior of such a small structure via usual classical theories cease to hold. In this work, the problem is formulated in the context of the surface/interface elasticity. For a rigorous solution of the proposed problem, conformal mapping with a Laurent series expansion are employed together. The numerical results well illustrate that the torsional rigidity and stress distribution corresponding to such nanosized structural elements are significantly affected by the size. In order to employ surface and interface...