Elias Mahmoudinezhad Zirdehi - Profile on Academia.edu (original) (raw)
Papers by Elias Mahmoudinezhad Zirdehi
International Journal of Polymer Science, May 28, 2018
In this contribution, diffusion of water, acetone, and ethanol into a polymer matrix has been stu... more In this contribution, diffusion of water, acetone, and ethanol into a polymer matrix has been studied experimentally and numerically by finite element approaches. Moreover, the present study reports an assessment of different thermomechanical conditions of the shape-memory (SM) performance, for example, stress-or strain-holding times in stress-or strain-controlled thermomechanical cycles and the effect of maximum strain. According to the results presented here, the uptake of acetone in Estane is much higher than ethanol and follows classical Fickian diffusion. Further, a series of thermomechanical measurements conducted on dry and physically (hydrolytically) aged polyether urethanes revealed that incorporation of water seems to have an appreciable impact on the shape recovery ratios which can be attributed to the additional physical crosslinks. However, no obvious difference in shape fixation of dry and physically (hydrolytically) aged samples could be recognized. Furthermore, by decreasing the strain-holding time, shape recovery improves significantly. Moreover, the shape fixity is found to be independent of holding time. The shape recovery ratio decreased dramatically with an increase in the stress-holding time.
Journal of Physics: Condensed Matter, Apr 13, 2020
Adding plasticizers is a well-known procedure to reduce the glass transition temperature in polym... more Adding plasticizers is a well-known procedure to reduce the glass transition temperature in polymers. It has been recently shown that this effect shows a non-monotonic dependence on the size of additive molecules [The Journal of Chemical Physics 150 (2019) 024903]. In this work, we demonstrate that, as the size of the additive molecules is changed at fixed concentration, multiple extrema emerge in the dependence of the system's relaxation time on the size ratio. The effect occurs on all relevant length scales including single monomer dynamics, decay of Rouse modes and relaxation of the chain's end-to-end vector. A qualitatively similar trend is found within mode-coupling theoretical results for a binary hard-sphere (HS) mixture. An interpretation of the effect in terms of local packing efficiency and coupling between the dynamics of minority and majority species is provided.
Journal of Chemical Physics, Jan 11, 2019
Effect of small additive molecules on the structural relaxation of polymer melts is investigated ... more Effect of small additive molecules on the structural relaxation of polymer melts is investigated via molecular dynamics simulations. At a constant external pressure and a fixed number concentration of added molecules, the variation of particle diameter leads to a non-monotonic change of the relaxation dynamics of the polymer melt. For non-entangled chains, this effect is rationalized in terms of an enhanced added-particle-dynamics which competes with a weaker coupling strength upon decreasing the particle size. Interestingly, cooling simulations reveal a non-monotonic effect on the glass transition temperature also for entangled chains, where the effect of additives on polymer dynamics is more intricate. This observation underlines the importance of monomer-scale packing effects on the glass transition in polymers. In view of this fact, size-adaptive thermosensitive core-shell colloids would be a promising candidates route to explore this phenomenon experimentally.
Effect of Surfactant Selectivity on Shape and Inner Morphology of Triblock Terpolymer Microparticles
Macromolecular Rapid Communications, May 5, 2023
The confined assembly of block copolymers (BCPs) has become a useful tool to prepare microparticl... more The confined assembly of block copolymers (BCPs) has become a useful tool to prepare microparticles with controlled anisotropy and inner structure. While a solid understanding of the behavior of AB diblock copolymers exists, knowledge on the parameters affecting ABC triblock terpolymer assembly is much more limited. In this work, the effect of block‐selective surfactants, sodium‐4‐vinylbenzenesulfonate (VBS) and sodium dodecylsulfate (SDS), is analyzed in the evaporation‐induced confined assembly (EICA) of a polystyrene‐block‐polybutadiene‐block‐poly(methyl methacrylate) triblock terpolymer (SBM). Despite using the same terpolymer and emulsification process, SDS results in ellipsoidal microparticles with axially stacked lamellae, while VBS results in spherical microparticles with concentric lamellae or 3D spiral morphology. This change in morphology upon switching the surfactant is further substantiated by molecular simulations and enhances the understanding of terpolymer microphase separation in confinement.
Formgedächtnispolymere gelten als intelligente Materialien dank ihrer Fähigkeit, sich von temporä... more Formgedächtnispolymere gelten als intelligente Materialien dank ihrer Fähigkeit, sich von temporär programmierten Formen in ihre ursprüngliche Form zurückzubilden, nachdem sie einem äußeren Reiz ausgesetzt wurden. In vielen Anwendungen, einschließlich der biomedizinischen, kann die Funktionalität durch das Eindringen von kleinen Molekülen aus der biologischen Umgebung beeinflusst werden. Im Gegenteil, die Adsorption von Additiven kann genutzt werden, um die Wiederherstellungsinitiierung zugunsten der Anpassung solcher Materialien für bestimmte Anwendungen zu tunen. In dieser Dissertation wird dieses Thema mit einem Schwerpunkt auf dem Größeneffekt von Penetriermitteln untersucht, indem großskalige Molekulardynamiksimulationen von generischen Modellen verwendet werden. Wir haben untersucht, wie die Größe von Additiven als neuartiger Parameter zur Auslösung des Erholungsprozesses in polymerbasierten Formgedächtnismaterialien verwendet werden kann.
Materials, 2021
In the present work, we study the role of programming strain (50% and 100%), end loads (0, 0.5, 1... more In the present work, we study the role of programming strain (50% and 100%), end loads (0, 0.5, 1.0, and 1.5 MPa), and chemical environments (acetone, ethanol, and water) on the exploitable stroke of linear shape memory polymer (SMP) actuators made from ESTANE ETE 75DT3 (SMP-E). Dynamic mechanical thermal analysis (DMTA) shows how the uptake of solvents results in a decrease in the glass temperature of the molecular switch component of SMP-E. A novel in situ technique allows studying chemically triggered shape recovery as a function of time. It is found that the velocity of actuation decreases in the order acetone > ethanol > water, while the exploitable strokes show the inverse tendency and increases in the order water > ethanol > acetone. The results are interpreted on the basis of the underlying chemical (how solvents affect thermophysical properties) and micromechanical processes (the phenomenological spring dashpot model of Lethersich type rationalizes the behavior)...
Materials, 2021
Small additive molecules often enhance structural relaxation in polymers. We explore this effect ... more Small additive molecules often enhance structural relaxation in polymers. We explore this effect in a thermoplastic shape memory polymer via molecular dynamics simulations. The additive-to-monomer size ratio is shown to play a key role here. While the effect of additive-concentration on the rate of shape recovery is found to be monotonic in the investigated range, a non-monotonic dependence on the size-ratio emerges at temperatures close to the glass transition. This work thus identifies the additives’ size to be a qualitatively novel parameter for controlling the recovery process in polymer-based shape memory materials.
International Journal of Polymer Science, 2018
In this contribution, diffusion of water, acetone, and ethanol into a polymer matrix has been stu... more In this contribution, diffusion of water, acetone, and ethanol into a polymer matrix has been studied experimentally and numerically by finite element approaches. Moreover, the present study reports an assessment of different thermomechanical conditions of the shape-memory (SM) performance, for example, stress- or strain-holding times in stress- or strain-controlled thermomechanical cycles and the effect of maximum strain. According to the results presented here, the uptake of acetone in Estane is much higher than ethanol and follows classical Fickian diffusion. Further, a series of thermomechanical measurements conducted on dry and physically (hydrolytically) aged polyether urethanes revealed that incorporation of water seems to have an appreciable impact on the shape recovery ratios which can be attributed to the additional physical crosslinks. However, no obvious difference in shape fixation of dry and physically (hydrolytically) aged samples could be recognized. Furthermore, by ...
Small additive molecules often enhance structural relaxation in polymers. We explore this effect ... more Small additive molecules often enhance structural relaxation in polymers. We explore this effect in a thermoplastic shape memory polymer via molecular dynamics simulations. The additiveto-monomer size ratio is shown to play a key role here. While the effect of additive-concentration on the rate of shape recovery is found to be monotonic in the investigated range, a non-monotonic dependence on the size-ratio emerges at temperatures close to the glass transition. This work thus identifies the additives' size to be a qualitatively novel parameter for controlling the recovery process in polymer-based shape memory materials.
EPL (Europhysics Letters)
PACS 81.05.Kf-Glasses (including metallic glasses) PACS 62.20.-x-Mechanical properties of solids ... more PACS 81.05.Kf-Glasses (including metallic glasses) PACS 62.20.-x-Mechanical properties of solids PACS 62.20.Fe-Deformation and plasticity (including yield, ductility, and superplasticity) Abstract.-We present a quantitative study of strain correlations in quiescent supercooled liquids and glasses. Recent two-dimensional computer simulations and experiments indicate that even supercooled liquids exhibit long-lived, long-range strain correlations. Here we investigate this issue in three dimensions via experiments on hard sphere colloids and molecular dynamics simulations of a glass forming binary Lennard Jones mixture. Both in the glassy state and in the supercooled regime, strain correlations are found to decay with a 1/r 3 power-law behavior, reminiscent of elastic fields around an inclusion. Moreover, theoretical predictions on the time dependence of the correlation amplitude are in line with the results obtained from experiments and simulations. It is argued that the size of the domain, which exhibits a cooperative strain pattern in a supercooled liquid, is determined by the product of the speed of sound with the structural relaxation time. While this length is of the order of nanometers in the normal liquid state, it grows to macroscale when approaching the glass transition.
A comprehensive study on the encapsulation of methane in single-walled carbon nanotubes
This paper aims at exploring the characteristics of a single methane molecule encapsulated in sem... more This paper aims at exploring the characteristics of a single methane molecule encapsulated in semi-infinite 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.
An accurate spring-mass finite element model for vibration analysis of single-walled carbon nanotubes
An accurate spring-mass model, in the context of a three-dimensional finite element formulation, ... more An accurate spring-mass model, in the context of a three-dimensional finite element formulation, is developed for investigating the vibrational characteristics of single-walled carbon nanotubes (SWCNTs). Atoms are replaced by lumped mass elements at their locations and appropriate spring-type elements are defined as interconnections between the atoms in order to simulate the interatomic interactions. The effect of out of plane angle variation energy is incorporated into the model. The obtained results for the fundamental frequency of single-walled carbon nanotubes of various kinds are graphically illustrated. The influences of some commonly-used boundary conditions and changes in the nanotube geometrical parameters on vibration frequencies are examined. The numerical results show good agreement with other published results in the literature. Also, some novel relations are deduced which can be more useful in predicting the fundamental frequency of SWCNTs with great number of atoms.
An accurate spring-mass model for predicting mechanical properties of single-walled carbon nanotubes
An accurate spring-mass model, in the context of a three-dimensional finite element formulation, ... more An accurate spring-mass model, in the context of a three-dimensional finite element formulation, is developed for estimating Young's and shear modulus of single-walled carbon nanotubes (SWCNTs). Lumped mass elements are placed at the atom locations and appropriate spring-type elements are defined as interconnections between the atoms in order to simulate the inter-atomic interactions.
Vibration analysis of circular and square single-layered graphene sheets: An accurate spring mass model
The free vibration characteristics of circular and square single-layered graphene sheets (SLGSs) ... more The free vibration characteristics of circular and square single-layered graphene sheets (SLGSs) are investigated by developing a finite element formulation based on an accurate spring mass model. According to the present atomistic structural model, nodes are defined at the atom locations and suitable three-dimensional spring-type elements are employed to connect these nodes which are representing interatomic interactions.
Journal of Vibration and …, 2012
Carbon nanotube oscillators which can generate frequencies in the gigahertz range have attracted ... more Carbon nanotube oscillators which can generate frequencies in the gigahertz range have attracted much attention in recent years. A number of studies on double-walled carbon nanotube (DWCNT) oscillators can be found in the literature, while other mechanisms of these oscillators with a higher number of oscillating nanotubes have not been well studied. This paper aims to investigate the motion properties of triple-walled carbon nanotube (TWCNT) oscillators in which the inner and middle tubes have telescopic motions with respect to the outer tube. To this end, the continuum approximation together with the Lennard-Jones potential function is utilized. In comparison with DWCNT oscillators, the triple-walled ones have shown a variety of motion patterns. In this respect, different types of motion patterns are classified and demonstrated. Moreover, it is observed that these nano-oscillators are so sensitive to their initial conditions. For this reason, a phase division of initial separation distances that generate different motion patterns is also presented.
Preferred Position and Orientation of Anticancer Drug Cisplatin During Encapsulation Into Single-Walled Carbon Nanotubes
… of Nanotechnology in …, 2012
Cisplatin is one of the most widely prescribed chemotherapy drugs to treat different types of can... more Cisplatin is one of the most widely prescribed chemotherapy drugs to treat different types of cancers. However, this anticancer drug has a number of side effects such as kidney and nerve damages, anaphylactic reactions, hearing loss, nausea, and vomiting that strongly restrict its function. In the present study, single-walled carbon nanotubes (SWCNTs) are used as protective drug carriers which can decrease these severe side effects to some extent. Using the hybrid discrete-continuum model in conjunction with Lennard-Jones ...
Journal of Physics and …, 2012
Based on the continuum Lennard-Jones model, the van der Waals interaction of two concentric and e... more Based on the continuum Lennard-Jones model, the van der Waals interaction of two concentric and eccentric carbon nanocones with different or identical sizes are investigated in this paper. Also, on the basis of classical mathematical modeling techniques, a new semi-analytical solution is given to evaluate the van der Waals potential energy and interaction force distributions of two concentric carbon nanocones. Finally, a universal potential energy is presented for the carbon nanocones.
International Journal of Polymer Science, May 28, 2018
In this contribution, diffusion of water, acetone, and ethanol into a polymer matrix has been stu... more In this contribution, diffusion of water, acetone, and ethanol into a polymer matrix has been studied experimentally and numerically by finite element approaches. Moreover, the present study reports an assessment of different thermomechanical conditions of the shape-memory (SM) performance, for example, stress-or strain-holding times in stress-or strain-controlled thermomechanical cycles and the effect of maximum strain. According to the results presented here, the uptake of acetone in Estane is much higher than ethanol and follows classical Fickian diffusion. Further, a series of thermomechanical measurements conducted on dry and physically (hydrolytically) aged polyether urethanes revealed that incorporation of water seems to have an appreciable impact on the shape recovery ratios which can be attributed to the additional physical crosslinks. However, no obvious difference in shape fixation of dry and physically (hydrolytically) aged samples could be recognized. Furthermore, by decreasing the strain-holding time, shape recovery improves significantly. Moreover, the shape fixity is found to be independent of holding time. The shape recovery ratio decreased dramatically with an increase in the stress-holding time.
Journal of Physics: Condensed Matter, Apr 13, 2020
Adding plasticizers is a well-known procedure to reduce the glass transition temperature in polym... more Adding plasticizers is a well-known procedure to reduce the glass transition temperature in polymers. It has been recently shown that this effect shows a non-monotonic dependence on the size of additive molecules [The Journal of Chemical Physics 150 (2019) 024903]. In this work, we demonstrate that, as the size of the additive molecules is changed at fixed concentration, multiple extrema emerge in the dependence of the system's relaxation time on the size ratio. The effect occurs on all relevant length scales including single monomer dynamics, decay of Rouse modes and relaxation of the chain's end-to-end vector. A qualitatively similar trend is found within mode-coupling theoretical results for a binary hard-sphere (HS) mixture. An interpretation of the effect in terms of local packing efficiency and coupling between the dynamics of minority and majority species is provided.
Journal of Chemical Physics, Jan 11, 2019
Effect of small additive molecules on the structural relaxation of polymer melts is investigated ... more Effect of small additive molecules on the structural relaxation of polymer melts is investigated via molecular dynamics simulations. At a constant external pressure and a fixed number concentration of added molecules, the variation of particle diameter leads to a non-monotonic change of the relaxation dynamics of the polymer melt. For non-entangled chains, this effect is rationalized in terms of an enhanced added-particle-dynamics which competes with a weaker coupling strength upon decreasing the particle size. Interestingly, cooling simulations reveal a non-monotonic effect on the glass transition temperature also for entangled chains, where the effect of additives on polymer dynamics is more intricate. This observation underlines the importance of monomer-scale packing effects on the glass transition in polymers. In view of this fact, size-adaptive thermosensitive core-shell colloids would be a promising candidates route to explore this phenomenon experimentally.
Effect of Surfactant Selectivity on Shape and Inner Morphology of Triblock Terpolymer Microparticles
Macromolecular Rapid Communications, May 5, 2023
The confined assembly of block copolymers (BCPs) has become a useful tool to prepare microparticl... more The confined assembly of block copolymers (BCPs) has become a useful tool to prepare microparticles with controlled anisotropy and inner structure. While a solid understanding of the behavior of AB diblock copolymers exists, knowledge on the parameters affecting ABC triblock terpolymer assembly is much more limited. In this work, the effect of block‐selective surfactants, sodium‐4‐vinylbenzenesulfonate (VBS) and sodium dodecylsulfate (SDS), is analyzed in the evaporation‐induced confined assembly (EICA) of a polystyrene‐block‐polybutadiene‐block‐poly(methyl methacrylate) triblock terpolymer (SBM). Despite using the same terpolymer and emulsification process, SDS results in ellipsoidal microparticles with axially stacked lamellae, while VBS results in spherical microparticles with concentric lamellae or 3D spiral morphology. This change in morphology upon switching the surfactant is further substantiated by molecular simulations and enhances the understanding of terpolymer microphase separation in confinement.
Formgedächtnispolymere gelten als intelligente Materialien dank ihrer Fähigkeit, sich von temporä... more Formgedächtnispolymere gelten als intelligente Materialien dank ihrer Fähigkeit, sich von temporär programmierten Formen in ihre ursprüngliche Form zurückzubilden, nachdem sie einem äußeren Reiz ausgesetzt wurden. In vielen Anwendungen, einschließlich der biomedizinischen, kann die Funktionalität durch das Eindringen von kleinen Molekülen aus der biologischen Umgebung beeinflusst werden. Im Gegenteil, die Adsorption von Additiven kann genutzt werden, um die Wiederherstellungsinitiierung zugunsten der Anpassung solcher Materialien für bestimmte Anwendungen zu tunen. In dieser Dissertation wird dieses Thema mit einem Schwerpunkt auf dem Größeneffekt von Penetriermitteln untersucht, indem großskalige Molekulardynamiksimulationen von generischen Modellen verwendet werden. Wir haben untersucht, wie die Größe von Additiven als neuartiger Parameter zur Auslösung des Erholungsprozesses in polymerbasierten Formgedächtnismaterialien verwendet werden kann.
Materials, 2021
In the present work, we study the role of programming strain (50% and 100%), end loads (0, 0.5, 1... more In the present work, we study the role of programming strain (50% and 100%), end loads (0, 0.5, 1.0, and 1.5 MPa), and chemical environments (acetone, ethanol, and water) on the exploitable stroke of linear shape memory polymer (SMP) actuators made from ESTANE ETE 75DT3 (SMP-E). Dynamic mechanical thermal analysis (DMTA) shows how the uptake of solvents results in a decrease in the glass temperature of the molecular switch component of SMP-E. A novel in situ technique allows studying chemically triggered shape recovery as a function of time. It is found that the velocity of actuation decreases in the order acetone > ethanol > water, while the exploitable strokes show the inverse tendency and increases in the order water > ethanol > acetone. The results are interpreted on the basis of the underlying chemical (how solvents affect thermophysical properties) and micromechanical processes (the phenomenological spring dashpot model of Lethersich type rationalizes the behavior)...
Materials, 2021
Small additive molecules often enhance structural relaxation in polymers. We explore this effect ... more Small additive molecules often enhance structural relaxation in polymers. We explore this effect in a thermoplastic shape memory polymer via molecular dynamics simulations. The additive-to-monomer size ratio is shown to play a key role here. While the effect of additive-concentration on the rate of shape recovery is found to be monotonic in the investigated range, a non-monotonic dependence on the size-ratio emerges at temperatures close to the glass transition. This work thus identifies the additives’ size to be a qualitatively novel parameter for controlling the recovery process in polymer-based shape memory materials.
International Journal of Polymer Science, 2018
In this contribution, diffusion of water, acetone, and ethanol into a polymer matrix has been stu... more In this contribution, diffusion of water, acetone, and ethanol into a polymer matrix has been studied experimentally and numerically by finite element approaches. Moreover, the present study reports an assessment of different thermomechanical conditions of the shape-memory (SM) performance, for example, stress- or strain-holding times in stress- or strain-controlled thermomechanical cycles and the effect of maximum strain. According to the results presented here, the uptake of acetone in Estane is much higher than ethanol and follows classical Fickian diffusion. Further, a series of thermomechanical measurements conducted on dry and physically (hydrolytically) aged polyether urethanes revealed that incorporation of water seems to have an appreciable impact on the shape recovery ratios which can be attributed to the additional physical crosslinks. However, no obvious difference in shape fixation of dry and physically (hydrolytically) aged samples could be recognized. Furthermore, by ...
Small additive molecules often enhance structural relaxation in polymers. We explore this effect ... more Small additive molecules often enhance structural relaxation in polymers. We explore this effect in a thermoplastic shape memory polymer via molecular dynamics simulations. The additiveto-monomer size ratio is shown to play a key role here. While the effect of additive-concentration on the rate of shape recovery is found to be monotonic in the investigated range, a non-monotonic dependence on the size-ratio emerges at temperatures close to the glass transition. This work thus identifies the additives' size to be a qualitatively novel parameter for controlling the recovery process in polymer-based shape memory materials.
EPL (Europhysics Letters)
PACS 81.05.Kf-Glasses (including metallic glasses) PACS 62.20.-x-Mechanical properties of solids ... more PACS 81.05.Kf-Glasses (including metallic glasses) PACS 62.20.-x-Mechanical properties of solids PACS 62.20.Fe-Deformation and plasticity (including yield, ductility, and superplasticity) Abstract.-We present a quantitative study of strain correlations in quiescent supercooled liquids and glasses. Recent two-dimensional computer simulations and experiments indicate that even supercooled liquids exhibit long-lived, long-range strain correlations. Here we investigate this issue in three dimensions via experiments on hard sphere colloids and molecular dynamics simulations of a glass forming binary Lennard Jones mixture. Both in the glassy state and in the supercooled regime, strain correlations are found to decay with a 1/r 3 power-law behavior, reminiscent of elastic fields around an inclusion. Moreover, theoretical predictions on the time dependence of the correlation amplitude are in line with the results obtained from experiments and simulations. It is argued that the size of the domain, which exhibits a cooperative strain pattern in a supercooled liquid, is determined by the product of the speed of sound with the structural relaxation time. While this length is of the order of nanometers in the normal liquid state, it grows to macroscale when approaching the glass transition.
A comprehensive study on the encapsulation of methane in single-walled carbon nanotubes
This paper aims at exploring the characteristics of a single methane molecule encapsulated in sem... more This paper aims at exploring the characteristics of a single methane molecule encapsulated in semi-infinite 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.
An accurate spring-mass finite element model for vibration analysis of single-walled carbon nanotubes
An accurate spring-mass model, in the context of a three-dimensional finite element formulation, ... more An accurate spring-mass model, in the context of a three-dimensional finite element formulation, is developed for investigating the vibrational characteristics of single-walled carbon nanotubes (SWCNTs). Atoms are replaced by lumped mass elements at their locations and appropriate spring-type elements are defined as interconnections between the atoms in order to simulate the interatomic interactions. The effect of out of plane angle variation energy is incorporated into the model. The obtained results for the fundamental frequency of single-walled carbon nanotubes of various kinds are graphically illustrated. The influences of some commonly-used boundary conditions and changes in the nanotube geometrical parameters on vibration frequencies are examined. The numerical results show good agreement with other published results in the literature. Also, some novel relations are deduced which can be more useful in predicting the fundamental frequency of SWCNTs with great number of atoms.
An accurate spring-mass model for predicting mechanical properties of single-walled carbon nanotubes
An accurate spring-mass model, in the context of a three-dimensional finite element formulation, ... more An accurate spring-mass model, in the context of a three-dimensional finite element formulation, is developed for estimating Young's and shear modulus of single-walled carbon nanotubes (SWCNTs). Lumped mass elements are placed at the atom locations and appropriate spring-type elements are defined as interconnections between the atoms in order to simulate the inter-atomic interactions.
Vibration analysis of circular and square single-layered graphene sheets: An accurate spring mass model
The free vibration characteristics of circular and square single-layered graphene sheets (SLGSs) ... more The free vibration characteristics of circular and square single-layered graphene sheets (SLGSs) are investigated by developing a finite element formulation based on an accurate spring mass model. According to the present atomistic structural model, nodes are defined at the atom locations and suitable three-dimensional spring-type elements are employed to connect these nodes which are representing interatomic interactions.
Journal of Vibration and …, 2012
Carbon nanotube oscillators which can generate frequencies in the gigahertz range have attracted ... more Carbon nanotube oscillators which can generate frequencies in the gigahertz range have attracted much attention in recent years. A number of studies on double-walled carbon nanotube (DWCNT) oscillators can be found in the literature, while other mechanisms of these oscillators with a higher number of oscillating nanotubes have not been well studied. This paper aims to investigate the motion properties of triple-walled carbon nanotube (TWCNT) oscillators in which the inner and middle tubes have telescopic motions with respect to the outer tube. To this end, the continuum approximation together with the Lennard-Jones potential function is utilized. In comparison with DWCNT oscillators, the triple-walled ones have shown a variety of motion patterns. In this respect, different types of motion patterns are classified and demonstrated. Moreover, it is observed that these nano-oscillators are so sensitive to their initial conditions. For this reason, a phase division of initial separation distances that generate different motion patterns is also presented.
Preferred Position and Orientation of Anticancer Drug Cisplatin During Encapsulation Into Single-Walled Carbon Nanotubes
… of Nanotechnology in …, 2012
Cisplatin is one of the most widely prescribed chemotherapy drugs to treat different types of can... more Cisplatin is one of the most widely prescribed chemotherapy drugs to treat different types of cancers. However, this anticancer drug has a number of side effects such as kidney and nerve damages, anaphylactic reactions, hearing loss, nausea, and vomiting that strongly restrict its function. In the present study, single-walled carbon nanotubes (SWCNTs) are used as protective drug carriers which can decrease these severe side effects to some extent. Using the hybrid discrete-continuum model in conjunction with Lennard-Jones ...
Journal of Physics and …, 2012
Based on the continuum Lennard-Jones model, the van der Waals interaction of two concentric and e... more Based on the continuum Lennard-Jones model, the van der Waals interaction of two concentric and eccentric carbon nanocones with different or identical sizes are investigated in this paper. Also, on the basis of classical mathematical modeling techniques, a new semi-analytical solution is given to evaluate the van der Waals potential energy and interaction force distributions of two concentric carbon nanocones. Finally, a universal potential energy is presented for the carbon nanocones.