Publication Date: 2023
Mechanics of Advanced Materials and Structures (15210596)30(24)pp. 5159-5175
A two-stage molecular dynamics (MD)-finite element (FE) modeling method is developed based on the concepts of representative volume element (RVE) and equivalent solid fibers (ESFs) containing functionalized carbon nanotubes (ESFs-fCNTs). First, the influences of nanotubes’ chirality, different percent of functionalization ((Formula presented.)), various functional atoms, and polymers on the tensile and shear properties of the fCNTs inserted into the polymer matrix (fCNTs/polymer) are discovered using MD simulations. Then, using MD information as input data, the effective Young’s modulus of polymeric unit cell strengthened by ESFs-fCNTs (ESFs-fCNTs/polymer) is explored through FE modeling. The ratio of effective Young’s modulus of the unit cell ((Formula presented.)) to Young’s modulus of the polymeric cube ((Formula presented.)) is reported and all findings ((Formula presented.)) are compared to the ESFs-pure CNTs/polymer results as well. It is found that longitudinal Young’s modulus ((Formula presented.)) of nanofillers/polymer RVEs affects remarkably the (Formula presented.) of the ESFs-nanofillers/polymer nanocomposites. The (Formula presented.) decreases by increasing the (Formula presented.) Generally, the reinforcing impact of zigzag nanotubes compared to armchair ones on the (Formula presented.) of polymer RVEs is more considerable. Additionally, FE-based results illustrate that as the volume fraction of ESFs ((Formula presented.)) increases, the (Formula presented.) is enhanced. At a specific (Formula presented.) the reinforcing effect of the ESFs-armchair and zigzag fCNTs is more in favor of polyethylene nanocomposites than that of the polypropylene systems. © 2022 Taylor & Francis Group, LLC.
Nowadays, in the goods and services market, retaining existing customers is more profitable than attracting new customers. Since latter costs more than the former, having loyal customers is now a major goal for many organizations. Also, with the development of e-businesses, creating this loyalty as e-loyalty is highly important. The aim of this paper is to investigate the influence of each of the Porter's strategy dimensions, including cost leadership, differentiation and focus, on loyalty in the context of e-business. In this regard, a questionnaire was prepared; subsequent to approving the validity of the questionnaire, it was randomly distributed among a random sample of 100 people who were potential and actual users of particular sites in the City of Isfahan. The findings indicate that, although focus strategy is more effective on creating e-loyalty, no significant difference was observed between the two other strategies in having more influence on e-loyalty. © 2016 IEEE.
Dabestani, R.,
Shahin, A.,
Shirouyehzad, H.,
Saljoughian, M. Publication Date: 2017
Total Quality Management and Business Excellence (14783363)28(3-4)pp. 331-350
The current study aims to prioritise service quality dimensions (SQDs) for hotels through a two-step procedure: firstly, by forming congruent groups of customers based on their level of expectations as well as perceptions of service; and secondly, by prioritising SQDs for each group and analysing the results. To reach that aim, the customers of three four-star hotels were targeted and asked to report on the quality of the service they expected to receive prior to its delivery as well as their feelings towards the service after they received it. Then, using data envelopment analysis we discriminated the majority of customers, those who were satisfied more easily (ordinary customers), from the ones who were harder to please (fastidious customers). Finally, we exploited Technique for Order Preference by Similarity to an Ideal Solution and Shannon Entropy to prioritise SQDs for each group. The approach taken in this paper, which first distinguishes two groups of fastidious from ordinary customers based on their expectations and perceptions, is rather noble. Findings revealed that the two groups do not value different dimensions of service quality in a similar way. The results of this study can provide insightful guidance for the hoteliers to customise their service and exploit their resources more efficiently. © 2015 Taylor & Francis.
Publication Date: 2024
Iranian Polymer Journal (10261265)33(12)pp. 1677-1688
This study aims to examine how moisture absorption affects the impact behavior of a recently developed sandwich structure designed for use as a water-resistant system in the marine industry. For this purpose, two types of balsa-cored sandwich systems were manufactured, one with conventional glass fiber-epoxy (GE) skins and the other with novel fiber metal laminates (FML) skins. Subsequently, the specimens were exposed to environmental aging through distilled water immersion for 100 days before impact testing. Low-velocity impact behavior was studied using Charpy tests, while high-velocity impact tests were conducted with a light gas gun. The experimental results showed that FML sandwich systems exhibited significantly better impact characteristics compared to GE systems. Before aging, the Charpy impact strength and high-velocity impact absorbed energy of FML systems were 187% and 49% higher than those of GE ones. Another main finding was the impact properties of the FML systems showed a lower decline due to moisture aging compared to the GE systems, for both low- and high-velocity impacts. The reduction of Charpy impact strength and high-velocity impact absorbed energy due to moisture aging in GE systems with sealed edges was about 15%, and 3%, respectively, and for sealed edges FML systems was less than 12% and 1%, respectively. The results also indicated that the high-velocity impact properties of both sandwich systems studied were not significantly affected by moisture aging. In general, the findings suggest that FML skins significantly enhance both the impact resistance and environmental durability in marine balsa-cored sandwich structures. Graphical abstract: (Figure presented.) © Iran Polymer and Petrochemical Institute 2024.
Publication Date: 2021
Mechanics of Advanced Materials and Structures (15210596)28(24)pp. 2531-2550
Reinforced by nanowires (NWs), carbon nanotubes (CNTs) and NW encapsulated CNT (NW@CNT), tensile behavior of various types of Cu-Zr based metallic glass (MG) nanocomposites are studied using molecular dynamics (MD) simulations. It is observed that pure two-toms alloy MG and the one reinforced with bigger CNT demonstrates higher tensile properties than other types of MGs. Further, it is observed that the ultimate strength of reinforced MGs with individual CNTs is slightly higher than that of NW@CNT reinforced analogous. In this case, it is noticed that reinforced three-atoms Cu-Zr MG nanocomposites including Ti atoms demonstrate the highest ultimate strength and strain. © 2020 Taylor & Francis Group, LLC.
Publication Date: 2025
International Journal for Numerical Methods in Engineering (00295981)126(22)
This article presents a comparative study of the computational characteristics of Finite Element Analysis (FEA) and Isogeometric Analysis (IGA) in studying large elastic deformations and large-amplitude vibrations of shell-type structures. A geometrically nonlinear seven-parameter shell model is employed in a Lagrangian description in which the shell deformation is represented in mid-surface. Using a curvilinear coordinate system suitable for various geometries, the kinematic and kinetic of the problem are established, and Hamilton's principle is applied to derive the governing equations. The strain–displacement relationships and consequently, the remaining variational formulations are expressed in a matrix-vector form, allowing for direct implementation in both FEA and IGA. This efficient formulation enables a fair and consistent comparison between the two methods. Several numerical examples are examined, including the well-known static benchmark problems and their corresponding forced vibration analyses. The primary contribution of this article is the demonstration of the computational efficiency of isogeometric analysis in challenging case studies of geometrically nonlinear shells. Additional novel contributions include deriving a unified formulation for seven-parameter FEA and IGA shell models as well as analyzing the large-amplitude free and forced vibrations of shells. © 2025 John Wiley & Sons Ltd.
Publication Date: 2020
Composites Part A: Applied Science and Manufacturing (1359-835X)130
This article investigates electrical conductivity and piezoresistivity of carbon nanotube (CNT)-polymer nanocomposites using an efficient analytical model. The effects of chopped carbon fibers on the electrical conductivity and percolation behavior of multiscale polymer-based nanocomposites containing CNTs are examined at various maximum angular orientations and different polymer matrix barrier heights. The multiscale nanocomposite (MSNC) electrical conductivity and percolation onset are found to be dependent on the carbon fiber and CNT geometry and dispersion. The tunneling effect is discussed as an important mechanism to explain the low percolation threshold and nonlinear electric behavior of MSNC. A comparison between nanocomposites filled with CNTs and MSNC reinforced with CNTs and chopped carbon fibers demonstrates different percolation behaviors. Moreover, the influences of CNT position and orientation changes on the piezoresistivity of polymer nanocomposites are studied. Resistance change ratio as a function of applied strain demonstrates a non-linear behavior due to tunneling resistance change between CNTs. © 2019 Elsevier Ltd
Publication Date: 2021
Mechanics of Advanced Materials and Structures (15210596)28(4)pp. 331-342
A new mixed micromechanics method for a comprehensive analysis of the coefficient of thermal expansion (CTE) of carbon nanotube (CNT)/polymer nanocomposites with fully random microstructures is established. Comparisons between the model results and experiment clearly prove that for a more realistic prediction, considering random orientation and random distribution of CNTs, interphase region created due to the non-bonded van der Waals interactions between the CNT and polymer, non-straight shape and transversely isotropic behavior of CNT is essential in the modeling. The effects of interphase characteristics, geometrical properties and type of random distribution of CNTs on the nanocomposite CTEs are examined. © 2019 Taylor & Francis Group, LLC.
Publication Date: 2018
International Journal of Business Excellence (17560055)16(3)pp. 362-383
The purpose of this study is to create a model of succession management planning. The sample, consisting of 16 managers, was formed using snowball sampling. The data were analysed, using Strauss and Corbin’s (1998) three-stage coding process. Results indicate that the modern succession structure acts as a central theme in the design of the integrated model of succession planning. The causal conditions, at three levels of individual, organisational and managerial structures, mediated by the modern succession structure, have impact upon the succession management accomplishing strategies. These strategies are: policy making, candidate evaluation, candidate development, and the effectiveness assessment. Of course, confounding conditions at three micro, organisational and macro levels, as well as the contextual conditions in three areas of the organisational outlook, contexts realising organisational outlooks, and organisational policies, influence these strategies. The outcomes of these strategies and the influencing processes eventually find expressions at (individual), (unit) and (organisational) levels. Copyright © 2018 Inderscience Enterprises Ltd.
Hassanzadeh-aghdam, M.K.,
Mahmoodi m.j., M.J.,
Ansari, R. Publication Date: 2018
Journal of Alloys and Compounds (09258388)739pp. 164-177
A reliable and optimal design of metal matrix nanocomposites (MMNCs) reinforced by nanoscale particles critically requires establishing the accurate material-characterizing relations of such new systems. So, this paper presents an inclusive model to predict the elastic modulus, thermal expansion coefficient, yield strength and ultimate tensile strength of MMNCs containing nanoparticles. Size factor and the agglomerated state for the nanoparticles into the metal matrix, generation of dislocations by thermal mismatch and Orowan strengthening mechanism are considered in the analysis. The influence of volume fraction and diameter of nanoparticles, material properties of matrix and temperature difference on the MMNCs effective thermoelastic and strength properties are studied in detail. Generally, the predicted values match well with experimental data. The results prove that for accurate estimations of the elastic modulus and thermal expansion properties of the MMNCs reinforced with uniformly dispersed nanoparticles, the size factor must be considered. The more realistic characterizations of the yield strength and ultimate tensile strength of the MMNCs containing uniformly distributed nanoparticles could only be achieved with considering both thermal mismatch and Orowan strengthening mechanism. Additionally, when the nanoparticles are not well dispersed into the metal matrix, speculating the nanoparticles agglomerated state to acquire a more realistic prediction is critically essential. The MMNCs thermomechanical characteristics can be significantly improved by (i) increasing volume fraction, (iii) decreasing the nanoparticle diameter and (iii) uniform dispersion into the metal matrix. © 2017 Elsevier B.V.
Publication Date: 2024
Applied Physics A: Materials Science and Processing (14320630)130(4)
In this study, we investigate the mechanical properties of armchair phosphorene nanotubes using a combination of density functional theory (DFT) and the finite element method (FEM). Utilizing DFT, we determine the Young’s modulus, flexural rigidity, and Poisson's ratio of armchair phosphorene nanotubes. Subsequently, employing the finite element method based on the analogy of molecular mechanics and structural mechanics, we extract elemental properties for the finite element model. Our analysis reveals that the Young’s modulus of phosphorene nanotubes is intricately linked to the nanotube radius, demonstrating a dependency that converges as the radius increases. Furthermore, an increase in the aspect ratio of phosphorene nanotubes corresponds to an elevation in their Young’s modulus, with a notable exception for small aspect ratios where the impact on elastic properties is minimal. This research significantly advances our understanding of the mechanical behavior of armchair phosphorene nanotubes, offering insights crucial for unlocking their potential in diverse scientific and technological applications. The observed relationships between Young's modulus and nanotube parameters provide valuable considerations for the design and application of nanomaterials, making our findings relevant and influential in both scientific research and industrial endeavors. © The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature 2024.
Ansari, R.,
Mahmoudinezhad e., E.,
Alipour a., A.,
Hosseinzadeh m., Publication Date: 2013
Journal of Computational and Theoretical Nanoscience (15461955)10(9)pp. 2209-2215
This paper aims at exploring the characteristics of a single methane molecule encapsulated in semiinfinite single-walled carbon nanotubes. On the basis of Lennard-Jones potential function along with the continuum approximation and applied mathematics, single integrals are presented to formulate the van der Waals interaction energy and suction energy between a single methane molecule and a carbon nanotube. The preferred position and orientation of methane with regard to the nanotube axis has been fully investigated for different nanotube radii. To this end, it is assumed that the whole molecule rotates in all directions inside the nanotube. It is found that for certain radii of nanotubes in which the suction energy imparted to methane is negative, the whole methane molecule is symmetric with respect to the tube axis when it is inside the carbon nanotube. But, when the suction energy has positive values, as the tube radius increases the methane molecule gets closer to the wall of nanotube and finally locates near its wall in the form of a downward tripod. Furthermore, the optimum nanotube radius which gives rise to maximum suction energy has been calculated. The results obtained in this study can be conducted as means of further investigations for methane storage in carbon nanotubes. © 2013 American Scientific Publishers. All rights reserved.
Publication Date: 2019
Engineering Structures (18737323)181pp. 653-669
The main objective of this paper is to analyze the free vibration of arbitrary shaped thick functionally graded carbon nanotube-reinforced composite (FG-CNTRC) plates based on the higher-order shear deformation theory (HSDT) using a variational differential quadrature approach. By means of the generalized differential quadrature (GDQ) numerical operators and Hamilton's principle, the discretized equations of motion are obtained. In order to use the GDQ differential and integral operators appropriately, the coordinate transformation is considered through the conventional finite element approach for transforming the irregular domain of the plate into the regular computational one. Employing a unified numerical approach to analyze different shapes of thick FG-CNTRC plates based on HSDT is the main novel aspect of the present study. To imply the accuracy of the present model, a wide range of comparison studies are presented. The results indicate the efficiency of the developed numerical methodology to study the vibration of arbitrary shaped thick FG-CNTRC plates. Several results are also given to investigate the impacts of geometrical parameters and material properties on the vibrational behavior of FG-CNTRC plates. © 2018 Elsevier Ltd
Publication Date: 2013
Communications in Nonlinear Science and Numerical Simulation (10075704)18(3)pp. 769-784
Amongst possible new nanomechanical devices created based on carbon nanostructures, high-frequency nanoscale oscillators, or the so-called gigahertz oscillators have attracted much attention. In this paper, the oscillatory behavior of spherical fullerenes inside carbon nanotubes is thoroughly investigated. To this end, the continuum approximation together with Lennard-Jones potential is used to evaluate the van der Waals potential energy and interaction force. The equation of motion is directly solved based on the actual force distribution between the two nanostructures, without any simplifying assumption. A semi-analytical expression is obtained for the oscillation frequency into which the effect of initial conditions is incorporated. Thereafter, this newly derived expression is utilized in order to present a comprehensive study on the effects of different system variables such as geometrical parameters and initial conditions on the oscillation frequency. Based upon these studies, some new features of such oscillations have been revealed. © 2012 Elsevier B.V.
Hassanzadeh-aghdam, M.K.,
Ansari, R.,
Mahmoodi m.j., M.J.,
Darvizeh a., A.,
Hajati-modaraei a., Publication Date: 2018
Cement and Concrete Composites (0958-9465)90pp. 108-118
The thermal conductivities of cementitious nanocomposites reinforced by wavy carbon nanotubes (CNTs) are determined by the effective medium (EM) micromechanics-based method. The nanocomposite is composed of sinusoidally wavy CNTs as reinforcement and cement paste as matrix. The interfacial region between the CNTs and cementitious material is considered in the analysis. The effects of volume fraction and waviness parameters of CNTs, interfacial thermal resistance, type of CNTs placement within the matrix including aligned or randomly oriented CNTs, cement paste properties on the thermal conductivity coefficients of the nanocomposite are studied. The estimated values of the model are in very good agreement with available experimental data. Two parameters of CNT waviness and interfacial region contributions should be included in the modeling to predict realistic results for both aligned and randomly oriented CNT-reinforced nanocomposites. The results reveal that thermal conductivities K22 (transverse in-plane thermal conductivity) and K33 (longitudinal in-plane thermal conductivity) of the nanocomposites are remarkably dependent on the CNT waviness. Also, it is found that the CNT waviness moderately affects the thermal conductivity of a cementitious nanocomposite containing randomly oriented CNTs. However, the non-straight shape of CNTs does not influence the value of thermal conductivity K11 (transverse out of plane thermal conductivity). The achieved results can be useful to guide the design of cementitious nanocomposites with optimal thermal conductivity properties. © 2018 Elsevier Ltd
Dastgir, N.,
Ansari, R.,
Hassanzadeh-aghdam, M.K.,
Sahmani, S. Publication Date: 2025
Journal of Vibration Engineering and Technologies (25233920)13(5)
Purpose: The engineering design of vibrational energy harvesters consisting of piezocomposites is generally a challenging task because of various parameters involved at micro- and macro-scales. This paper aims to comprehensively evaluate vibration energy harvesting from a clamped-free bimorph beam with two layers of particulate piezocomposites. Methods: In this study, a multi-phase computational approach is employed to address the vibration energy harvesting using clamp-free piezocomposite bimorph beams. Two types of piezocomposites are examined, featuring LaRC-SI polyamide as the matrix and BaTiO₃ and PZT-7A as piezoelectric fillers. Using the micromechanical finite element method, electromechanical properties of the representative volume element (RVE) of the piezocomposites are predicted. The parametric studies are conducted to predict and compare output voltage and power, considering factors such as the volume fraction, geometry and type of piezoelectric filler, the series or parallel configuration of the circuit. The mode shapes and natural frequencies under structural weight are also analyzed. Results and Conclusion: The results reveal that increasing the volume fraction of piezoelectric fillers enhances electromechanical properties, leading to higher voltage and power output. Bimorph beams are shown to extract more electrical outputs compared to unimorph beams of the same piezocomposite characteristics. Additionally, a parallel circuit connection of the piezocomposite layers in a bimorph beam enhances the electrical outputs compared to a series connection. It is found that the output voltage and power are significantly increased as the piezoelectric filler aspect ratio increases. The frequency related to the peak voltage and power increases as the fillers’ geometry deviates more from spherical shape. © Springer Nature Singapore Pte Ltd. 2025.
Publication Date: 2002
Journal of Global Optimization (09255001)24(1)pp. 79-88
The Network Design Problem has been studied extensively and in many of these models the cost is assumed to be a concave function of the loads on the links. In this paper we investigate under which conditions this is indeed the case for the communication networks. The result is presented as a theorem, the Concavity Theorem, and a list of conditions that can easily be verified. It is also shown how the theorem can be extended to other applications, like in the area of road transportation.
Shirouyehzad, H.,
Lotfi, F.H.,
Shahin, A.,
Aryanezhad, M.,
Dabestani, R. Publication Date: 2012
International Journal of Services and Operations Management (17442370)12(3)pp. 289-308
During the last two decades, the subject of service quality has been widely recognised due to its vital contribution to customer satisfaction improvement. Service quality is also crucial in hospitality industry since hotels can improve their market share and profitability with appropriate quality of services. Respectively, it seems important to measure delivered services quality based on customers' point of view. In this paper, data envelopment analysis has been applied to identify the most critical service quality dimensions, based on the difference between customers' perceptions and expectations. The case study includes three four-star hotels in Isfahan. The findings imply that price, reliability and tangibles are the most important service quality dimensions. Copyright © 2012 Inderscience Enterprises Ltd.
Baghfeizi, I.M.,
Rahmanseresht, H.,
Fathi, S. Publication Date: 2018
International Journal of Business Excellence (17560055)15(3)pp. 269-288
This paper aims at presenting a 3 × 3 matrix to determine the structure of a holding company based on the degree of diversification and parenting style. Non-conformity of structure with this framework means that a restructuring is necessary. Three hypotheses have been tested to evaluate the validity of this framework. The first two hypotheses respectively assess the association between the 'degree of diversification' and 'parenting style' with 'structural form' based on chi-square test. But to test the third hypothesis, the holding companies compliance with the framework is divided into two groups and Mann-Witni (U) test shows that there is a significant difference between their performances. Based on Sharp's index, the economic performance of the holdings which are consistent with the framework, over a period of five years, is about 11 times better than non-conformers with the framework. Copyright © 2018 Inderscience Enterprises Ltd.
Publication Date: 2017
Applied Physics A: Materials Science and Processing (14320630)123(4)
In this paper, the vibrational characteristics of zigzag phosphorene nanotubes are investigated by using a three-dimensional finite element model. The beam elements are used to simulate the P–P bonds in the structure of the phosphorene nanotubes. The elastic properties of the beam elements are computed from the similarity of energy terms in the molecular and structural mechanics. Besides, mass elements are located at the place of the atoms. Considering the zigzag phosphorene nanotubes with different diameters, it is shown that the effect of the diameter on the first natural frequencies of the nanotubes can be neglected. However, this effect increases for higher modes. Besides, at the same diameter, the zigzag phosphorene nanotubes with larger aspect ratios (length/diameter) have smaller frequencies. © 2017, Springer-Verlag Berlin Heidelberg.
Publication Date: 2017
Physica E: Low-Dimensional Systems and Nanostructures (13869477)88pp. 272-278
In this paper, the density functional theory calculations are used to obtain the elastic properties of zigzag phosphorene nanotubes. Besides, based on the similarity between phosphorene nanotubes and a space-frame structure, a three-dimensional finite element model is proposed in which the atomic bonds are simulated by beam elements. The results of density functional theory are employed to compute the properties of the beam elements. Finally, using the proposed finite element model, the elastic modulus of the zigzag phosphorene nanotubes is computed. It is shown that phosphorene nanotubes with larger radii have larger Young's modulus. Comparing the results of finite element model with those of density functional theory, it is concluded that the proposed model can predict the elastic modulus of phosphorene nanotubes with a good accuracy. © 2017 Elsevier B.V.
Publication Date: 2019
Bulletin of Materials Science (02504707)42(4)
Fabrication of new types of nanoscale oscillators with enhanced operating frequency has become the focal centre of interest. The aim of this paper is to explore the mechanical oscillatory behaviour of chloride ion tunnelling through carbon nanotubes (CNTs) decorated with identical functional groups at both ends. To this end, our previously proposed analytical expression for total potential energy between an ion and a functionalized CNT is used to derive a new semi-analytical expression for the accurate evaluation of oscillation frequency. With respect to the proposed frequency formula obtained from the conservation of mechanical energy principle, a comprehensive study is conducted to gain an insight into the effects of different parameters such as, sign and magnitude of functional group charge, nanotube length and initial conditions on the operating frequency of chloride ion-electrically charged CNT oscillators. It is revealed that the presence of functional groups, especially ones with the opposite charges to the chloride ion, leads to enhancement of the maximum achievable frequency. It is further observed that optimal frequency is attained when the ion oscillates near the ends of a positively charged nanotube. © 2019, Indian Academy of Sciences.
Polymer nanofibers are being increasingly used for a wide range of applications owing to their high specific surface area. Electrospinning process, as a novel and effective method for producing nanofibers from various materials, has been used to fabricate nanofibrous membrane. Carbon nanotubes (CNTs) have a number of outstanding mechanical, electrical, and thermal properties, which make them attractive as reinforcement in polymer matrix. Incorporation of chapter provides a comprehensive review of current researches and developments in the field of electrospun CNT-polymer composite nanofiber with emphasis on the processing, properties, and application of composite nanofiber as well as the theoretical approaches on predicting mechanical behavior of CNT-polymer composites. The current limitations, research challenges, and future trends in modeling and simulation of electrospun polymer composite nanofibers are also discussed. © 2014 by Apple Academic Press, Inc. All rights reserved.
Publication Date: 2022
Materials Chemistry and Physics (02540584)283
Herein, the effects of halogen and metal atomic adsorption on the mechanical and structural characteristics of silicene are studied using density functional theory (DFT) calculations. Cl, Br, Au, Ca, Ga, Li, and Na atoms are selected as the adsorption atoms. Moreover, the phonon dispersion and electron localization function are investigated to show the stability of considered nanostructures and to visualize the bonding properties, respectively. It is shown that the adsorption leads to decreasing the elastic and bulk moduli of some structures, while it increases them in some other structures. It is seen that except for Ca-adsorbed nanosheet, both the elastic and bulk moduli of all other structures decrease after adsorption. Furthermore, the isotropic behavior of all the studied nanosheets is indicated. The plastic behavior is also analyzed. It is revealed that the second critical strain of all nanosheets, except for SiBr and SiCl, decreases under uniaxial loading. However, under biaxial loading conditions, the second critical strain of Au-, Ca-, and Ga-adsorbed structures decreases, while in other structures (SiBr, SiCl, SiLi, and SiNa) the adsorption increases the yield strain. © 2022 Elsevier B.V.
Aghdasi p., P.,
Yousefi, S.,
Ansari, R.,
Bagheri tagani m., Publication Date: 2022
Applied Physics A: Materials Science and Processing (14320630)128(8)
In this paper, the elastic and plastic properties of 2 × 2 and 3 × 3 pristine and transition metal (TM) doped silicene nanosheets are studied using the density functional theory (DFT) calculations. Cr, Co, Cu, Mn, Ti, V, Zn and Ni atoms are selected as doping atoms. It is observed that Young’s and bulk moduli of both 2 × 2 and 3 × 3 pristine structures decrease when they are affected by the doping atoms. The highest reduction in the Young’s and bulk moduli of the 2 × 2 nanosheets occurs for the Ni-doped structure, and the same reduction is observed for the Ni- and Cu-doped structures in the 3 × 3 nanosheets. In addition, it is shown that all of the investigated structures have an isotropic behavior, since their Young’s moduli have negligible difference along armchair and zigzag directions. Finally, the loading is further increased to investigate the plastic behavior of nanostructures. The results show that the yield strains of all doped nanosheets decrease under uniaxial and biaxial loadings. The highest reduction in the yield strain of the 2 × 2 nanosheets under biaxial loading is observed for Cu, Zn- and Co-doped nanosheets, and in 3 × 3 nanosheets, the highest reduction happens for the Cu- and Zn-doped nanosheets under the same condition. For the yield strain of the 2 × 2 doped nanosheets under the uniaxial loading, the Cu-doped structure experiences the highest reduction, and the highest reduction for the Mn-doped nanosheet under the same condition is observed in 3 × 3 nanosheets. The findings revealed that how electronic configuration of transition metal atom and its electronegativity difference with silicon atom can control the structural and mechanical properties of the nanosheet. © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.
Ansari, R.,
Faghihnasiri m., ,
Shahnazari a., A.,
Malakpour s., S.,
Sahmani, S. Publication Date: 2016
Journal of Alloys and Compounds (09258388)687pp. 790-796
Zirconia (ZrO2) as an important ceramic material has widespread potential applications in various fields of nanotechnology such as solid-state electrolytes, electro-optical materials, structural materials and etc. In the present investigation, density functional theory (DFT) calculations using quasi-harmonic approximation (QHA) are carried out to predict the influence of temperature change on the elastic properties of a monolayer ZrO2nanosheet. To this end, the exchange−correlation functional is approximated based on the generalized gradient approximation with the Perdew− Burke−Ernzerhof flavor. Firstly, it is indicated that the temperature change has a small influence on the elastic properties of a monolayer ZrO2nanosheet. Nevertheless, by increasing the value of temperature, it is revealed that in an overall view, the Young's modulus of structure decreases, but the bulk modulus of structure increases. Additionally, it is observed that for a specific temperature range, the value of Young's modulus of ZrO2nanosheet is more sensitive to the temperature change than its bulk modulus. Furthermore, it is revealed that the reduction in the Young's modulus and the increment in the bulk modulus due to temperature change is only about 1 Pa, so the increase in the motion of phonons because of higher temperatures does not lead to a considerable influence on the elastic properties of a monolayer ZrO2nanosheet. © 2016 Elsevier B.V.
