http://scholar.google.com/citations?hl=en&user=95SvbM8AAAAJ
41.
Fonseca, Alexandre F.; Galvao, Douglas S.
Self-Driven Graphene Tearing and Peeling: A Fully Atomistic Molecular Dynamics Investigation Online
2018, (preprint arXiv:1801.05354).
@online{Fonseca2018b,
title = {Self-Driven Graphene Tearing and Peeling: A Fully Atomistic Molecular Dynamics Investigation},
author = {Alexandre F. Fonseca and Douglas S. Galvao
},
url = {https://arxiv.org/abs/1801.05354},
year = {2018},
date = {2018-01-17},
abstract = {In spite of years of intense research, graphene continues to produce surprising results. Recently, it was experimentally observed that under certain conditions graphene can self-drive its tearing and peeling from substrates. This process can generate long, micrometer sized, folded nanoribbons without the action of any external forces. Also, during this cracking-like propagation process, the width of the graphene folded ribbon continuously decreases and the process only stops when the width reaches about few hundreds nanometers in size. It is believed that interplay between the strain energy of folded regions, breaking of carbon-carbon covalent bonds, and adhesion of graphene-graphene and graphene-substrate are the most fundamental features of this process, although the detailed mechanisms at atomic scale remain unclear. In order to gain further insights on these processes we carried out fully atomistic reactive molecular dynamics simulations using the AIREBO potential as available in the LAMMPS computational package. Although the reported tearing/peeling experimental observations were only to micrometer sized structures, our results showed that they could also occur at nanometer scale. Our preliminary results suggest that the graphene tearing/peeling process originates from thermal energy fluctuations that results in broken bonds, followed by strain release that creates a local elastic wave that can either reinforce the process, similar to a whip cracking propagation, or undermine it by producing carbon dangling bonds that evolve to the formation of bonds between the two layers of graphene. As the process continues in time and the folded graphene decreases in width, the carbon-carbon bonds at the ribbon edge and interlayer bonds get less stressed, thermal fluctuations become unable to break them and the process stops.},
note = {preprint arXiv:1801.05354},
keywords = {},
pubstate = {published},
tppubtype = {online}
}
In spite of years of intense research, graphene continues to produce surprising results. Recently, it was experimentally observed that under certain conditions graphene can self-drive its tearing and peeling from substrates. This process can generate long, micrometer sized, folded nanoribbons without the action of any external forces. Also, during this cracking-like propagation process, the width of the graphene folded ribbon continuously decreases and the process only stops when the width reaches about few hundreds nanometers in size. It is believed that interplay between the strain energy of folded regions, breaking of carbon-carbon covalent bonds, and adhesion of graphene-graphene and graphene-substrate are the most fundamental features of this process, although the detailed mechanisms at atomic scale remain unclear. In order to gain further insights on these processes we carried out fully atomistic reactive molecular dynamics simulations using the AIREBO potential as available in the LAMMPS computational package. Although the reported tearing/peeling experimental observations were only to micrometer sized structures, our results showed that they could also occur at nanometer scale. Our preliminary results suggest that the graphene tearing/peeling process originates from thermal energy fluctuations that results in broken bonds, followed by strain release that creates a local elastic wave that can either reinforce the process, similar to a whip cracking propagation, or undermine it by producing carbon dangling bonds that evolve to the formation of bonds between the two layers of graphene. As the process continues in time and the folded graphene decreases in width, the carbon-carbon bonds at the ribbon edge and interlayer bonds get less stressed, thermal fluctuations become unable to break them and the process stops.
42.
de Sousa, J. M.; Aguiar, A. L.; Girao, E. C.; Fonseca, Alexandre F.; Filho, A. G. Souza; Galvao, Douglas S.
Mechanical Properties of Phagraphene Membranes: A Fully Atomistic Molecular Dynamics Investigation Journal Article
Em: MRS Advances, vol. 3, não 1-2, pp. 67-72, 2018.
@article{deSousa2018c,
title = {Mechanical Properties of Phagraphene Membranes: A Fully Atomistic Molecular Dynamics Investigation},
author = {J. M. de Sousa and A. L. Aguiar and E. C. Girao and Alexandre F. Fonseca and A. G. Souza Filho and Douglas S. Galvao},
url = {https://www.cambridge.org/core/journals/mrs-advances/article/mechanical-properties-of-phagraphene-membranes-a-fully-atomistic-molecular-dynamics-investigation/3ADC3F3B0052AB6632E8681404948E7B},
doi = {DOI: 10.1557/adv.2018. 54},
year = {2018},
date = {2018-01-15},
journal = {MRS Advances},
volume = {3},
number = {1-2},
pages = {67-72},
abstract = {Recently, a new 2D carbon allotrope structure, named phagraphene (PG), was proposed. PG has a densely array of penta-hexa-hepta-graphene carbon rings. PG was shown to present low and anisotropic thermal conductivity and it is believed that this anisotropy should be also reflected in its mechanical properties. Although PG mechanical properties have been investigated, a detailed and comprehensive study is still lacking. In the present work we have carried out fully atomistic reactive molecular dynamics simulations using the ReaxFF force field, to investigate the mechanical properties and fracture patterns of PG membranes. The Young's modulus values of the PG membranes were estimated from the stress-strain curves. Our results show that these curves present three distinct regimes: one regime where ripples dominate the structure and mechanical properties of the PG membranes; an elastic regime where the membranes exhibit fully planar configurations; and finally am inelastic regime where permanent deformations happened to the PG membrane up to the mechanical failure or fracture.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Recently, a new 2D carbon allotrope structure, named phagraphene (PG), was proposed. PG has a densely array of penta-hexa-hepta-graphene carbon rings. PG was shown to present low and anisotropic thermal conductivity and it is believed that this anisotropy should be also reflected in its mechanical properties. Although PG mechanical properties have been investigated, a detailed and comprehensive study is still lacking. In the present work we have carried out fully atomistic reactive molecular dynamics simulations using the ReaxFF force field, to investigate the mechanical properties and fracture patterns of PG membranes. The Young's modulus values of the PG membranes were estimated from the stress-strain curves. Our results show that these curves present three distinct regimes: one regime where ripples dominate the structure and mechanical properties of the PG membranes; an elastic regime where the membranes exhibit fully planar configurations; and finally am inelastic regime where permanent deformations happened to the PG membrane up to the mechanical failure or fracture.
43.
de Sousa, J. M.; Aguiar, A. L.; Girao, E. C.; Fonseca, Alexandre F.; Filho, A. G. Sousa; Galvao, Douglas S.
Mechanical Properties of Pentagraphene-based Nanotubes: A Molecular Dynamics Study Online
2018, (preprint arXiv:1801.04269).
@online{deSousa2018d,
title = {Mechanical Properties of Pentagraphene-based Nanotubes: A Molecular Dynamics Study},
author = {J. M. de Sousa and A. L. Aguiar and E. C. Girao and Alexandre F. Fonseca and A. G. Sousa Filho and Douglas S. Galvao},
url = {https://arxiv.org/abs/1801.04269},
year = {2018},
date = {2018-01-15},
abstract = {The study of the mechanical properties of nanostructured systems has gained importance in
theoretical and experimental research in recent years. Carbon nanotubes (CNTs) are one of
the strongest nanomaterials found in nature, with Young's Modulus (YM) in the order 1.25
TPa. One interesting question is about the possibility of generating new nanostructures with
1D symmetry and with similar and/or superior CNT properties. In this work, we present a
study on the dynamical, structural, mechanical properties, fracture patterns and YM values
for one class of these structures, the so-called pentagraphene nanotubes (PGNTs). These
tubes are formed rolling up pentagraphene membranes (which are quasi-bidimensional
structures formed by densely compacted pentagons of carbon atoms in sp3 and sp2 hybridized
states) in the same form that CNTs are formed from rolling up graphene membranes. We
carried out fully atomistic molecular dynamics simulations using the ReaxFF force field. We
have considered zigzag-like and armchair-like PGNTs of different diameters. Our results
show that PGNTs present YM ~ 800 GPa with distinct elastic behavior in relation to CNTs,
mainly associated with mechanical failure, chirality dependent fracture patterns and extensive
structural reconstructions},
note = {preprint arXiv:1801.04269},
keywords = {},
pubstate = {published},
tppubtype = {online}
}
The study of the mechanical properties of nanostructured systems has gained importance in
theoretical and experimental research in recent years. Carbon nanotubes (CNTs) are one of
the strongest nanomaterials found in nature, with Young's Modulus (YM) in the order 1.25
TPa. One interesting question is about the possibility of generating new nanostructures with
1D symmetry and with similar and/or superior CNT properties. In this work, we present a
study on the dynamical, structural, mechanical properties, fracture patterns and YM values
for one class of these structures, the so-called pentagraphene nanotubes (PGNTs). These
tubes are formed rolling up pentagraphene membranes (which are quasi-bidimensional
structures formed by densely compacted pentagons of carbon atoms in sp3 and sp2 hybridized
states) in the same form that CNTs are formed from rolling up graphene membranes. We
carried out fully atomistic molecular dynamics simulations using the ReaxFF force field. We
have considered zigzag-like and armchair-like PGNTs of different diameters. Our results
show that PGNTs present YM ~ 800 GPa with distinct elastic behavior in relation to CNTs,
mainly associated with mechanical failure, chirality dependent fracture patterns and extensive
structural reconstructions
theoretical and experimental research in recent years. Carbon nanotubes (CNTs) are one of
the strongest nanomaterials found in nature, with Young's Modulus (YM) in the order 1.25
TPa. One interesting question is about the possibility of generating new nanostructures with
1D symmetry and with similar and/or superior CNT properties. In this work, we present a
study on the dynamical, structural, mechanical properties, fracture patterns and YM values
for one class of these structures, the so-called pentagraphene nanotubes (PGNTs). These
tubes are formed rolling up pentagraphene membranes (which are quasi-bidimensional
structures formed by densely compacted pentagons of carbon atoms in sp3 and sp2 hybridized
states) in the same form that CNTs are formed from rolling up graphene membranes. We
carried out fully atomistic molecular dynamics simulations using the ReaxFF force field. We
have considered zigzag-like and armchair-like PGNTs of different diameters. Our results
show that PGNTs present YM ~ 800 GPa with distinct elastic behavior in relation to CNTs,
mainly associated with mechanical failure, chirality dependent fracture patterns and extensive
structural reconstructions
44.
Oliveira, Eliezer Fernando; Santos, Ricardo Paupitz; da Silva Autreto, Pedro Alves; Stanislav Moshkalev,; Galvao, Douglas Soares
Improving Graphene-metal Contacts: Thermal Induced Polishing Online
2018, (preprint ArXiv:1801.04785).
@online{Oliveira2018d,
title = {Improving Graphene-metal Contacts: Thermal Induced Polishing},
author = {Eliezer Fernando Oliveira and Ricardo Paupitz Santos and Pedro Alves da Silva Autreto and Stanislav Moshkalev, and Douglas Soares Galvao},
url = {https://arxiv.org/abs/1801.04785},
year = {2018},
date = {2018-01-15},
abstract = {Graphene is a very promising material for nanoelectronics applications due to its unique and remarkable electronic and thermal properties. However, when deposited on metallic electrodes the overall thermal conductivity is significantly decreased. This phenomenon has been attributed to the mismatch between the interfaces and contact thermal resistance. Experimentally, one way to improve the graphene/metal contact is thorough high-temperature annealing, but the detailed mechanisms behind these processes remain unclear. In order to address these questions, we carried out fully atomistic reactive molecular dynamics simulations using the ReaxFF force field to investigate the interactions between multi-layer graphene and metallic electrodes (nickel) under (thermal) annealing. Our results show that the annealing induces an upward-downward movement of the graphene layers, causing a pile- driver-like effect over the metallic surface. This graphene induced movements cause a planarization (thermal polishing-like effect) of the metallic surface, which results in the increase of the effective graphene/metal contact area. This can also explain the experimentally observed improvements of the thermal and electric conductivities.},
note = {preprint ArXiv:1801.04785},
keywords = {},
pubstate = {published},
tppubtype = {online}
}
Graphene is a very promising material for nanoelectronics applications due to its unique and remarkable electronic and thermal properties. However, when deposited on metallic electrodes the overall thermal conductivity is significantly decreased. This phenomenon has been attributed to the mismatch between the interfaces and contact thermal resistance. Experimentally, one way to improve the graphene/metal contact is thorough high-temperature annealing, but the detailed mechanisms behind these processes remain unclear. In order to address these questions, we carried out fully atomistic reactive molecular dynamics simulations using the ReaxFF force field to investigate the interactions between multi-layer graphene and metallic electrodes (nickel) under (thermal) annealing. Our results show that the annealing induces an upward-downward movement of the graphene layers, causing a pile- driver-like effect over the metallic surface. This graphene induced movements cause a planarization (thermal polishing-like effect) of the metallic surface, which results in the increase of the effective graphene/metal contact area. This can also explain the experimentally observed improvements of the thermal and electric conductivities.
45.
de Sousa, Jose M.; Aguiar, Acrisio L.; Girao, Eduardo C.; Fonseca, Alexandre F.; Antonio G. Sousa Filho,; Galvao, Douglas S.
Mechanical Properties of Phagraphene Membranes: A Fully Atomistic Molecular Dynamics Investigation Online
2018, (preprint arXiv:1801.04292).
@online{deSousa2018e,
title = {Mechanical Properties of Phagraphene Membranes: A Fully Atomistic Molecular Dynamics Investigation},
author = {Jose M. de Sousa and Acrisio L. Aguiar and Eduardo C. Girao and Alexandre F. Fonseca and Antonio G. Sousa Filho, and Douglas S. Galvao
},
url = {https://arxiv.org/abs/1801.04292},
year = {2018},
date = {2018-01-12},
abstract = {Recently, a new 2D carbon allotrope structure, named phagraphene (PG), was proposed. PG has a densely array of penta-hexa-hepta-graphene carbon rings. PG was shown to present low and anisotropic thermal conductivity and it is believed that this anisotropy should be also reflected in its mechanical properties. Although PG mechanical properties have been investigated, a detailed and comprehensive study is still lacking. In the present work we have carried out fully atomistic reactive molecular dynamics simulations using the ReaxFF force field, to investigate the mechanical properties and fracture patterns of PG membranes. The Young's modulus values of the PG membranes were estimated from the stress-strain curves. Our results show that these curves present three distinct regimes: one regime where ripples dominate the structure and mechanical properties of the PG membranes; an elastic regime where the membranes exhibit fully planar configurations; and finally a plastic regime where permanent deformations happened to the PG membrane up to the mechanical failure or fracture.},
note = {preprint arXiv:1801.04292},
keywords = {},
pubstate = {published},
tppubtype = {online}
}
Recently, a new 2D carbon allotrope structure, named phagraphene (PG), was proposed. PG has a densely array of penta-hexa-hepta-graphene carbon rings. PG was shown to present low and anisotropic thermal conductivity and it is believed that this anisotropy should be also reflected in its mechanical properties. Although PG mechanical properties have been investigated, a detailed and comprehensive study is still lacking. In the present work we have carried out fully atomistic reactive molecular dynamics simulations using the ReaxFF force field, to investigate the mechanical properties and fracture patterns of PG membranes. The Young's modulus values of the PG membranes were estimated from the stress-strain curves. Our results show that these curves present three distinct regimes: one regime where ripples dominate the structure and mechanical properties of the PG membranes; an elastic regime where the membranes exhibit fully planar configurations; and finally a plastic regime where permanent deformations happened to the PG membrane up to the mechanical failure or fracture.
46.
de Sousa, Jose M.; Aguiar, Acrisio L.; Girao, Eduardo C.; Fonseca, Alexandre F.; Antonio G. Souza Filho,; Galvao, Douglas S.
Mechanical Properties of Pentagraphene-based Nanotubes: A Molecular Dynamics Study Online
2018, (preprint arXiv:1801.04269).
@online{deSousa2018f,
title = {Mechanical Properties of Pentagraphene-based Nanotubes: A Molecular Dynamics Study},
author = {Jose M. de Sousa and Acrisio L. Aguiar and Eduardo C. Girao and Alexandre F. Fonseca and Antonio G. Souza Filho, and Douglas S. Galvao},
url = {https://arxiv.org/abs/1801.04269},
year = {2018},
date = {2018-01-12},
abstract = {The study of the mechanical properties of nanostructured systems has gained importance in theoretical and experimental research in recent years. Carbon nanotubes (CNTs) are one of the strongest nanomaterials found in nature, with Young's Modulus (YM) in the order 1.25 TPa. One interesting question is about the possibility of generating new nanostructures with 1D symmetry and with similar and/or superior CNT properties. In this work, we present a study on the dynamical, structural, mechanical properties, fracture patterns and YM values for one class of these structures, the so-called pentagraphene nanotubes (PGNTs). These tubes are formed rolling up pentagraphene membranes (which are quasi-bidimensional structures formed by densely compacted pentagons of carbon atoms in sp3 and sp2 hybridized states) in the same form that CNTs are formed from rolling up graphene membranes. We carried out fully atomistic molecular dynamics simulations using the ReaxFF force field. We have considered zigzag-like and armchair-like PGNTs of different diameters. Our results show that PGNTs present YM ~ 800 GPa with distinct elastic behavior in relation to CNTs, mainly associated with mechanical failure, chirality dependent fracture patterns and extensive structural reconstructions.},
note = {preprint arXiv:1801.04269},
keywords = {},
pubstate = {published},
tppubtype = {online}
}
The study of the mechanical properties of nanostructured systems has gained importance in theoretical and experimental research in recent years. Carbon nanotubes (CNTs) are one of the strongest nanomaterials found in nature, with Young's Modulus (YM) in the order 1.25 TPa. One interesting question is about the possibility of generating new nanostructures with 1D symmetry and with similar and/or superior CNT properties. In this work, we present a study on the dynamical, structural, mechanical properties, fracture patterns and YM values for one class of these structures, the so-called pentagraphene nanotubes (PGNTs). These tubes are formed rolling up pentagraphene membranes (which are quasi-bidimensional structures formed by densely compacted pentagons of carbon atoms in sp3 and sp2 hybridized states) in the same form that CNTs are formed from rolling up graphene membranes. We carried out fully atomistic molecular dynamics simulations using the ReaxFF force field. We have considered zigzag-like and armchair-like PGNTs of different diameters. Our results show that PGNTs present YM ~ 800 GPa with distinct elastic behavior in relation to CNTs, mainly associated with mechanical failure, chirality dependent fracture patterns and extensive structural reconstructions.
47.
Azevedo, David L.; Bizao, Rafael A.; Galvao, Douglas S.
Molecular Dynamics Simulations of Ballistic Penetration of Pentagraphene Sheets Journal Article
Em: MRS Advances, vol. 3, não 8-9, pp. 431-435, 2018.
@article{Azevedo2018,
title = {Molecular Dynamics Simulations of Ballistic Penetration of Pentagraphene Sheets},
author = {David L. Azevedo and Rafael A. Bizao and Douglas S. Galvao},
url = {https://www.cambridge.org/core/journals/mrs-advances/article/molecular-dynamics-simulations-of-ballistic-penetration-of-pentagraphene-sheets/8759C0815840EDE83896EF4A17278228},
doi = {https://doi.org/10.1557/adv.2018.61},
year = {2018},
date = {2018-01-06},
journal = {MRS Advances},
volume = {3},
number = {8-9},
pages = {431-435},
abstract = {The search for new materials with low density and superior mechanical properties is a very intense and stimulating investigation area. These new materials could provide potential application for ballistic protection. Recent experiments and simulations revealed graphene possesses exceptional energy absorption properties. In this work, we analysed through fully atomistic molecular dynamics simulations the ballistic performance of a carbon-based material recently proposed named penta-graphene. Our results show that the fracture pattern is more spherical (no petals formation like observed for graphene). The estimated penetration energy for single-layer penta-graphene structures obtained here was d_1penta∼37.7 MJ/kg, and is comparable with recently results obtained for graphene: d_(1graphene)∼29.0 MJ/kg and d_(1graphene)∼40.8 MJ/kg under similar conditions. These preliminary results are suggestive that penta-graphene could be an excellent material for ballistic applications.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The search for new materials with low density and superior mechanical properties is a very intense and stimulating investigation area. These new materials could provide potential application for ballistic protection. Recent experiments and simulations revealed graphene possesses exceptional energy absorption properties. In this work, we analysed through fully atomistic molecular dynamics simulations the ballistic performance of a carbon-based material recently proposed named penta-graphene. Our results show that the fracture pattern is more spherical (no petals formation like observed for graphene). The estimated penetration energy for single-layer penta-graphene structures obtained here was d_1penta∼37.7 MJ/kg, and is comparable with recently results obtained for graphene: d_(1graphene)∼29.0 MJ/kg and d_(1graphene)∼40.8 MJ/kg under similar conditions. These preliminary results are suggestive that penta-graphene could be an excellent material for ballistic applications.
48.
M, Ajayan Pulickel; Woellner, Cristiano F; Owuor, Peter S; Trigueiro, Joao P C; Machado, Leonardo D; Silva, Wellington M; Kosolwattana, Suppanat; Jaques, Ygor M; Silva, Carlos J R; Pedrotti, Jairo; Tiwary, Chandra S; Chipara, Alin C; Galvao, Douglas; Chopra, Nitin; Odeh, Ihab N; Silva, Glaura G.
Hybrid 2D Nanostructures for Mechanical Reinforcement and Thermal Conductivity Enhancement in Polymer Composite Journal Article
Em: Composites Science and Technology, vol. 159, não 5, pp. 103-110, 2018.
@article{M2018,
title = {Hybrid 2D Nanostructures for Mechanical Reinforcement and Thermal Conductivity Enhancement in Polymer Composite},
author = {Ajayan Pulickel M and Cristiano F Woellner and Peter S Owuor and Joao P C Trigueiro and Leonardo D Machado and Wellington M Silva and Suppanat Kosolwattana and Ygor M Jaques and Carlos J R Silva and Jairo Pedrotti and Chandra S Tiwary and Alin C Chipara and Douglas Galvao and Nitin Chopra and Ihab N Odeh and Glaura G. Silva
},
doi = {https://doi.org/10.1016/j.compscitech.2018.01.032},
year = {2018},
date = {2018-01-01},
journal = {Composites Science and Technology},
volume = {159},
number = {5},
pages = {103-110},
abstract = {Hexagonal boron nitride (h-BN), graphene oxide (GO) and hybrid (GO/h-BN) nanosheets were employed as fillers in order to enhance the physical properties of the polymer matrix. Composites based in epoxy and these two-dimensional (2D) nanofillers were produced with different wt% and their microstructure, mechanical and thermal properties were investigated. Increases up to 140% in tensile strength, 177% in ultimate strain and 32% in elastic modulus were observed for the hybrid GO/h-BN composite with 0.5 wt% content. The hybrid nanofiller also contributed to the increase up to 142% on thermal conductivity with respect to the pure epoxy for GO/h-BN composite with 2.0 wt% content. Molecular dynamic simulation was used to predict the behavior of possible stacking arrangements between h-BN and GO nanosheets tensioned by normal and shear forces. The results showed that the hybrid GO/h-BN combination can prevent the re-stacking process of exfoliated layers, demonstrating the synergism between these nanostructures with the final effect of better dispersion in the composite material. The excellent thermal and mechanical performance of these hybrid composites en- gineered by the combination of different types of the 2D inorganic nanoparticles make them multifunctional candidates for advanced materials applications.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Hexagonal boron nitride (h-BN), graphene oxide (GO) and hybrid (GO/h-BN) nanosheets were employed as fillers in order to enhance the physical properties of the polymer matrix. Composites based in epoxy and these two-dimensional (2D) nanofillers were produced with different wt% and their microstructure, mechanical and thermal properties were investigated. Increases up to 140% in tensile strength, 177% in ultimate strain and 32% in elastic modulus were observed for the hybrid GO/h-BN composite with 0.5 wt% content. The hybrid nanofiller also contributed to the increase up to 142% on thermal conductivity with respect to the pure epoxy for GO/h-BN composite with 2.0 wt% content. Molecular dynamic simulation was used to predict the behavior of possible stacking arrangements between h-BN and GO nanosheets tensioned by normal and shear forces. The results showed that the hybrid GO/h-BN combination can prevent the re-stacking process of exfoliated layers, demonstrating the synergism between these nanostructures with the final effect of better dispersion in the composite material. The excellent thermal and mechanical performance of these hybrid composites en- gineered by the combination of different types of the 2D inorganic nanoparticles make them multifunctional candidates for advanced materials applications.
49.
Oliveira, Eliezer Fernando; da Silva Autreto, Pedro Alves; Galvao, Douglas Soares
Silver Hardening via Hypersonic Impacts Journal Article
Em: MRS Advances, vol. 3, não 8-9, pp. 489-494, 2018.
@article{Oliveira2018b,
title = {Silver Hardening via Hypersonic Impacts},
author = {Eliezer Fernando Oliveira and Pedro Alves da Silva Autreto and Douglas Soares Galvao},
url = {https://www.cambridge.org/core/journals/mrs-advances/article/silver-hardening-via-hypersonic-impacts/6A35FAB117B4FD244BBD11A64CD25160},
doi = {DOI: 10.1557/adv.2018. 173},
year = {2018},
date = {2018-01-01},
journal = {MRS Advances},
volume = {3},
number = {8-9},
pages = {489-494},
abstract = {The search for new ultra strong materials has been a very active research area. With relation to metals, a successful way to improve their strength is by the creation of a gradient of nanograins (GNG) inside the material. Recently, R. Thevamaran et al. [Science v354, 312- 316 (2016)] propose a single step method based on high velocity impact of silver nanocubes to produce high-quality GNG. This method consists of producing high impact collisions of silver cubes at hypersonic velocity (~400 m/s) against a rigid wall. Although they observed an improvement in the mechanical properties of the silver after the impact, the GNG creation and the strengthening mechanism at nanoscale remain unclear. In order to gain further insights about these mechanisms, we carried out fully atomistic molecular dynamics simulations (MD) to investigate the atomic conformations/rearrangements during and after high impact collisions of silver nanocubes at ultrasonic velocity. Our results indicate the co- existence of polycrystalline arrangements after the impact formed by core HCP domains surrounded by FCC ones, which could also contribute to explain the structural hardening.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The search for new ultra strong materials has been a very active research area. With relation to metals, a successful way to improve their strength is by the creation of a gradient of nanograins (GNG) inside the material. Recently, R. Thevamaran et al. [Science v354, 312- 316 (2016)] propose a single step method based on high velocity impact of silver nanocubes to produce high-quality GNG. This method consists of producing high impact collisions of silver cubes at hypersonic velocity (~400 m/s) against a rigid wall. Although they observed an improvement in the mechanical properties of the silver after the impact, the GNG creation and the strengthening mechanism at nanoscale remain unclear. In order to gain further insights about these mechanisms, we carried out fully atomistic molecular dynamics simulations (MD) to investigate the atomic conformations/rearrangements during and after high impact collisions of silver nanocubes at ultrasonic velocity. Our results indicate the co- existence of polycrystalline arrangements after the impact formed by core HCP domains surrounded by FCC ones, which could also contribute to explain the structural hardening.
50.
Oliveira, Eliezer Fernando; Paupitz, Ricardo; da Silva Autreto, Pedro Alves; Moshkalev, Stanislav; Galvao, Douglas Soares
Improving Graphene-metal Contacts: Thermal Induced Polishing Journal Article
Em: MRS Advances, vol. 3, não 1-2, pp. 73-78, 2018.
@article{Oliveira2018c,
title = {Improving Graphene-metal Contacts: Thermal Induced Polishing },
author = {Eliezer Fernando Oliveira and Ricardo Paupitz and Pedro Alves da Silva Autreto and Stanislav Moshkalev and Douglas Soares Galvao},
url = {https://www.cambridge.org/core/journals/mrs-advances/article/improving-graphenemetal-contacts-thermal-induced-polishing/AC01C4996B90B0EE5E03220604071D12},
doi = {https://doi.org/10.1557/adv.2018.66},
year = {2018},
date = {2018-01-01},
journal = {MRS Advances},
volume = {3},
number = {1-2},
pages = {73-78},
abstract = {Graphene is a very promising material for nanoelectronics applications due to its unique and remarkable electronic and thermal properties. However, when deposited on metallic electrodes the overall thermal conductivity is significantly decreased. This phenomenon has been attributed to the mismatch between the interfaces and contact thermal resistance. Experimentally, one way to improve the graphene/metal contact is thorough high-temperature annealing, but the detailed mechanisms behind these processes remain unclear. In order to address these questions, we carried out fully atomistic reactive molecular dynamics simulations using the ReaxFF force field to investigate the interactions between multi-layer graphene and metallic electrodes (nickel) under (thermal) annealing. Our results show that the annealing induces an upward-downward movement of the graphene layers, causing a pile-driver-like effect over the metallic surface. This graphene induced movements cause a planarization (thermal polishing-like effect) of the metallic surface, which results in the increase of the effective graphene/metal contact area. This can also explain the experimentally observed improvements of the thermal and electric conductivities.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Graphene is a very promising material for nanoelectronics applications due to its unique and remarkable electronic and thermal properties. However, when deposited on metallic electrodes the overall thermal conductivity is significantly decreased. This phenomenon has been attributed to the mismatch between the interfaces and contact thermal resistance. Experimentally, one way to improve the graphene/metal contact is thorough high-temperature annealing, but the detailed mechanisms behind these processes remain unclear. In order to address these questions, we carried out fully atomistic reactive molecular dynamics simulations using the ReaxFF force field to investigate the interactions between multi-layer graphene and metallic electrodes (nickel) under (thermal) annealing. Our results show that the annealing induces an upward-downward movement of the graphene layers, causing a pile-driver-like effect over the metallic surface. This graphene induced movements cause a planarization (thermal polishing-like effect) of the metallic surface, which results in the increase of the effective graphene/metal contact area. This can also explain the experimentally observed improvements of the thermal and electric conductivities.
51.
Leonardo D Machado Cristiano F Woellner, Pedro AS Autreto; Galvao, Douglas S
Structural Transformations of Carbon and Boron Nitride Nanoscrolls at High Impact Collisions Online
2017, (preprint ArXiv:1711.00378).
@online{Woellner2017,
title = {Structural Transformations of Carbon and Boron Nitride Nanoscrolls at High Impact Collisions},
author = {Cristiano F Woellner, Leonardo D Machado, Pedro AS Autreto, Jose M de Sousa, and Douglas S Galvao},
url = {https://arxiv.org/pdf/1711.00378.pdf},
year = {2017},
date = {2017-11-01},
abstract = {The behavior of nanostructures under high strain-rate conditions has been object of theoretical and experimental investigations in recent years. For instance, it has been shown that carbon and boron nitride nanotubes can be unzipped into nanoribbons at high velocity impacts. However, the response of many nanostructures to high strain-rate conditions is still not completely understood. In this work we have investigated through fully atomistic reactive (ReaxFF) molecular dynamics (MD) simulations the mechanical behavior of carbon (CNS) and boron nitride nanoscrolls (BNS) colliding against solid targets at high velocities,. CNS (BNS) nanoscrolls are graphene (boron nitride) membranes rolled up into papyrus-like
structures. Their open-ended topology leads to unique properties not found in close-ended analogues, such as nanotubes.Our results show that the collision products are mainly determined by impact velocities and by two impact angles, which
define the position of the scroll (i) axis and (ii) open edge relative to the target. Our MD results showed that for appropriate velocities and orientations large-scale deformations and nanoscroll fracture can occur. We also observed unscrolling (scrolls going back to quasi-planar membranes), scroll unzipping into nanoribbons, and significant
reconstruction due to breaking and/or formation of new chemical bonds. For particular edge orientations and velocities, conversion from open to close-ended topology is also possible, due to the fusion of nanoscroll walls.},
note = {preprint ArXiv:1711.00378},
keywords = {},
pubstate = {published},
tppubtype = {online}
}
The behavior of nanostructures under high strain-rate conditions has been object of theoretical and experimental investigations in recent years. For instance, it has been shown that carbon and boron nitride nanotubes can be unzipped into nanoribbons at high velocity impacts. However, the response of many nanostructures to high strain-rate conditions is still not completely understood. In this work we have investigated through fully atomistic reactive (ReaxFF) molecular dynamics (MD) simulations the mechanical behavior of carbon (CNS) and boron nitride nanoscrolls (BNS) colliding against solid targets at high velocities,. CNS (BNS) nanoscrolls are graphene (boron nitride) membranes rolled up into papyrus-like
structures. Their open-ended topology leads to unique properties not found in close-ended analogues, such as nanotubes.Our results show that the collision products are mainly determined by impact velocities and by two impact angles, which
define the position of the scroll (i) axis and (ii) open edge relative to the target. Our MD results showed that for appropriate velocities and orientations large-scale deformations and nanoscroll fracture can occur. We also observed unscrolling (scrolls going back to quasi-planar membranes), scroll unzipping into nanoribbons, and significant
reconstruction due to breaking and/or formation of new chemical bonds. For particular edge orientations and velocities, conversion from open to close-ended topology is also possible, due to the fusion of nanoscroll walls.
structures. Their open-ended topology leads to unique properties not found in close-ended analogues, such as nanotubes.Our results show that the collision products are mainly determined by impact velocities and by two impact angles, which
define the position of the scroll (i) axis and (ii) open edge relative to the target. Our MD results showed that for appropriate velocities and orientations large-scale deformations and nanoscroll fracture can occur. We also observed unscrolling (scrolls going back to quasi-planar membranes), scroll unzipping into nanoribbons, and significant
reconstruction due to breaking and/or formation of new chemical bonds. For particular edge orientations and velocities, conversion from open to close-ended topology is also possible, due to the fusion of nanoscroll walls.
52.
Sajadi, Seyed Mohammad; Owuor, Peter Samora; Schara, Steven; Woellner, Cristiano F.; Rodrigues, Varlei; Vajtai, Robert; Lou, Jun; Galvao, Douglas S.; Tiwary, Chandra Sekhar; Ajayan, Pulickel M.
Multi-scale Geometric Design Principles Applied to 3D Printed Schwartizes Journal Article
Em: Advanced Materials, vol. 2017, pp. 1704820, 2017.
@article{Sajadi2017,
title = {Multi-scale Geometric Design Principles Applied to 3D Printed Schwartizes},
author = {Seyed Mohammad Sajadi and Peter Samora Owuor and Steven Schara and Cristiano F. Woellner and Varlei Rodrigues and Robert Vajtai and Jun Lou and Douglas S. Galvao and Chandra Sekhar Tiwary and Pulickel M. Ajayan},
url = {http://onlinelibrary.wiley.com/doi/10.1002/adma.201704820/full},
doi = {10.1002/adma.201704820},
year = {2017},
date = {2017-09-14},
journal = {Advanced Materials},
volume = {2017},
pages = {1704820},
abstract = {Schwartzites are 3D porous solids with periodic minimal surfaces having negative Gaussian curvatures and can possess unusual mechanical and electronic properties. The mechanical behavior of primitive and gyroid schwartzite structures across different length scales is investigated after these geometries are 3D printed at centimeter length scales based on molec- ular models. Molecular dynamics and nite elements simulations are used
to gain further understanding on responses of these complex solids under compressive loads and kinetic impact experiments. The results show that these structures hold great promise as high load bearing and impact-resistant materials due to a unique layered deformation mechanism that emerges in these architectures during loading. Easily scalable techniques such as 3D printing can be used for exploring mechanical behavior of various predicted complex geometrical shapes to build innovative engineered materials with tunable properties.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Schwartzites are 3D porous solids with periodic minimal surfaces having negative Gaussian curvatures and can possess unusual mechanical and electronic properties. The mechanical behavior of primitive and gyroid schwartzite structures across different length scales is investigated after these geometries are 3D printed at centimeter length scales based on molec- ular models. Molecular dynamics and nite elements simulations are used
to gain further understanding on responses of these complex solids under compressive loads and kinetic impact experiments. The results show that these structures hold great promise as high load bearing and impact-resistant materials due to a unique layered deformation mechanism that emerges in these architectures during loading. Easily scalable techniques such as 3D printing can be used for exploring mechanical behavior of various predicted complex geometrical shapes to build innovative engineered materials with tunable properties.
to gain further understanding on responses of these complex solids under compressive loads and kinetic impact experiments. The results show that these structures hold great promise as high load bearing and impact-resistant materials due to a unique layered deformation mechanism that emerges in these architectures during loading. Easily scalable techniques such as 3D printing can be used for exploring mechanical behavior of various predicted complex geometrical shapes to build innovative engineered materials with tunable properties.
53.
Manimunda, P; Nakanishi, Y; Jaques, YM; Susarla, S; Woellner, CF; Bhowmick, S; Asif, SAS; Galvao, DS; Tiwary, CS; Ajayan, PM
Nanoscale deformation and friction characteristics of atomically thin WSe2 and heterostructure using nanoscratch and Raman spectroscopy Journal Article
Em: 2D Materials, vol. 4, não 4, pp. 045005, 2017.
@article{Manimunda2017,
title = {Nanoscale deformation and friction characteristics of atomically thin WSe2 and heterostructure using nanoscratch and Raman spectroscopy},
author = {Manimunda, P and Nakanishi, Y and Jaques, YM and Susarla, S and Woellner, CF and Bhowmick, S and Asif, SAS and Galvao, DS and Tiwary, CS and Ajayan, PM},
url = {http://iopscience.iop.org/article/10.1088/2053-1583/aa8475/meta},
doi = {10.1088/2053-1583/aa8475},
year = {2017},
date = {2017-08-23},
journal = {2D Materials},
volume = {4},
number = {4},
pages = {045005},
abstract = {2D transition metals di-selenides are attracting a lot of attention due to their interesting optical, chemical and electronics properties. Here, the deformation characteristics of monolayer, multi- layer WSe2 and its heterostructure with MoSe2 were investigated using a new technique that combines nanoscratch and Raman spectroscopy. The 2D monolayer WSe2 showed anisotropy in deformation. Effect of number of WSe2 layers on friction characteristics were explored in detail. Experimental observations were further supported by MD simulations. Raman spectra recorded from the scratched regions showed strain induced degeneracy splitting. Further nano-scale scratch tests were extended to MoSe2–WSe2 lateral heterostructures. Effect of deformation on lateral hetero junctions were further analysed using PL and Raman spectroscopy. This new technique is completely general and can be applied to study other 2D materials.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
2D transition metals di-selenides are attracting a lot of attention due to their interesting optical, chemical and electronics properties. Here, the deformation characteristics of monolayer, multi- layer WSe2 and its heterostructure with MoSe2 were investigated using a new technique that combines nanoscratch and Raman spectroscopy. The 2D monolayer WSe2 showed anisotropy in deformation. Effect of number of WSe2 layers on friction characteristics were explored in detail. Experimental observations were further supported by MD simulations. Raman spectra recorded from the scratched regions showed strain induced degeneracy splitting. Further nano-scale scratch tests were extended to MoSe2–WSe2 lateral heterostructures. Effect of deformation on lateral hetero junctions were further analysed using PL and Raman spectroscopy. This new technique is completely general and can be applied to study other 2D materials.
54.
Owuor, Peter Samora; Park, Ok-Kyung; Woellner, Cristiano F; Jalilov, Almaz S; Susarla, Sandhya; Joyner, Jarin; Ozden, Sehmus; Duy, LuongXuan; Villegas Salvatierra, Rodrigo; Vajtai, Robert; Tour, James M; Lou, Jun; Galvao, Douglas S; Tiwary, Chandra S; Ajayan, P M
Lightweight Hexagonal Boron Nitride Foam for CO2 Absorption Journal Article
Em: ACS Nano, vol. 11, não 8, pp. 8944–8952, 2017.
@article{Owuor2017b,
title = {Lightweight Hexagonal Boron Nitride Foam for CO2 Absorption},
author = {Owuor, Peter Samora and Park, Ok-Kyung and Woellner, Cristiano F and Jalilov, Almaz S and Susarla, Sandhya and Joyner, Jarin and Ozden, Sehmus and Duy, LuongXuan and Villegas Salvatierra, Rodrigo and Vajtai, Robert and Tour, James M and Lou, Jun and Galvao, Douglas S and Tiwary, Chandra S and Ajayan, P M},
url = {http://pubs.acs.org/doi/abs/10.1021/acsnano.7b03291},
doi = {10.1021/acsnano.7b03291},
year = {2017},
date = {2017-08-03},
journal = {ACS Nano},
volume = {11},
number = {8},
pages = {8944–8952},
abstract = {Weak van der Waals forces between inert hexagonal boron nitride (h-BN) nanosheets make it easy for them to slide over each other, resulting in an unstable structure in macroscopic dimensions. Creating interconnections between these inert nanosheets can remarkably enhance their mechanical properties. However, controlled design of such interconnections remains a fundamental problem for many applications of h-BN foams. In this work, a scalable in situ freeze-drying synthesis of low-density, lightweight 3D macroscopic structures made of h-BN nanosheets chemically connected by poly(vinyl alcohol) (PVA) molecules via chemical cross-link is demonstrated. Unlike pristine h-BN foam which disintegrates upon handling after freeze-drying, h-BN/PVA foams exhibit stable mechanical integrity in addition to high porosity and large surface area. Fully atomistic simulations are used to understand the interactions between h-BN nanosheets and PVA molecules. In addition, the h-BN/PVA foam is investigated as a possible CO2 absorption and as laser irradiation protection material.
},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Weak van der Waals forces between inert hexagonal boron nitride (h-BN) nanosheets make it easy for them to slide over each other, resulting in an unstable structure in macroscopic dimensions. Creating interconnections between these inert nanosheets can remarkably enhance their mechanical properties. However, controlled design of such interconnections remains a fundamental problem for many applications of h-BN foams. In this work, a scalable in situ freeze-drying synthesis of low-density, lightweight 3D macroscopic structures made of h-BN nanosheets chemically connected by poly(vinyl alcohol) (PVA) molecules via chemical cross-link is demonstrated. Unlike pristine h-BN foam which disintegrates upon handling after freeze-drying, h-BN/PVA foams exhibit stable mechanical integrity in addition to high porosity and large surface area. Fully atomistic simulations are used to understand the interactions between h-BN nanosheets and PVA molecules. In addition, the h-BN/PVA foam is investigated as a possible CO2 absorption and as laser irradiation protection material.
55.
Miyazaki, Celina M; Maria, Marco AE; Borges, Daiane Damasceno; Woellner, Cristiano F; Brunetto, Gustavo; Fonseca, Alexandre F; Constantino, Carlos JL; Pereira-da-Silva, Marcelo A; de Siervo, Abner; Galvao, Douglas S; Riul Jr., Antonio
2017, (preprint arXiv:1702.00250).
@online{Miyazaki2017,
title = {Synthesis, characterization and computational simulation of graphene nanoplatelets stabilized in poly (styrene sulfonate) sodium salt},
author = {Miyazaki, Celina M and Maria, Marco AE and Borges, Daiane Damasceno and Woellner, Cristiano F and Brunetto, Gustavo and Fonseca, Alexandre F and Constantino, Carlos JL and Pereira-da-Silva, Marcelo A and de Siervo, Abner and Galvao, Douglas S and Riul Jr., Antonio},
url = {https://arxiv.org/abs/1705.10673},
year = {2017},
date = {2017-05-30},
abstract = {The production of large area interfaces and the use of scalable methods to build-up designed nanostructures generating advanced functional properties are of high interest for many materials science applications. Nevertheless, large area coverage remains a major problem for pristine graphene and here we present a hybrid, composite graphene-like material soluble in water, which can be exploited in many areas, such as energy storage, electrodes fabrication, selective membranes and biosensing. Graphene oxide (GO) was produced by the traditional Hummers method being further reduced in the presence of poly(styrene sulfonate) sodium salt (PSS), thus creating stable reduced graphene oxide (rGO) nanoplateles wrapped by PSS (GPSS). Molecular dynamics simulations were carried out of further clarify the interactions between PSS molecules and rGO nanoplatelets, with calculations supported by FTIR analysis. The intermolecular forces between rGO nanoplatelets and PSS lead to the formation of a hybrid material (GPSS) stabilized by van der Waals forces, allowing the fabrication of high quality layer-by-layer (LbL) films with polyalillamine hydrochloride (PAH). Raman and electrical characterizations corroborated the successful modifications in the electronic structures from GO to GPSS after the chemical treatment, resulting in (PAH/GPSS) LbL films four orders of magnitude more conductive than (PAH/GO).
},
note = {preprint arXiv:1702.00250},
keywords = {},
pubstate = {published},
tppubtype = {online}
}
The production of large area interfaces and the use of scalable methods to build-up designed nanostructures generating advanced functional properties are of high interest for many materials science applications. Nevertheless, large area coverage remains a major problem for pristine graphene and here we present a hybrid, composite graphene-like material soluble in water, which can be exploited in many areas, such as energy storage, electrodes fabrication, selective membranes and biosensing. Graphene oxide (GO) was produced by the traditional Hummers method being further reduced in the presence of poly(styrene sulfonate) sodium salt (PSS), thus creating stable reduced graphene oxide (rGO) nanoplateles wrapped by PSS (GPSS). Molecular dynamics simulations were carried out of further clarify the interactions between PSS molecules and rGO nanoplatelets, with calculations supported by FTIR analysis. The intermolecular forces between rGO nanoplatelets and PSS lead to the formation of a hybrid material (GPSS) stabilized by van der Waals forces, allowing the fabrication of high quality layer-by-layer (LbL) films with polyalillamine hydrochloride (PAH). Raman and electrical characterizations corroborated the successful modifications in the electronic structures from GO to GPSS after the chemical treatment, resulting in (PAH/GPSS) LbL films four orders of magnitude more conductive than (PAH/GO).
56.
Bizao, Rafael A; Botari, Tiago; Perim, Eric; Pugno, Nicola M; Galvao, Douglas S
Mechanical properties and fracture patterns of graphene (graphitic) nanowiggles Journal Article
Em: Carbon, vol. 119, pp. 431-437, 2017, (See also ArxIv version: https://arxiv.org/abs/1702.01100).
@article{Bizao2017b,
title = {Mechanical properties and fracture patterns of graphene (graphitic) nanowiggles},
author = {Bizao, Rafael A and Botari, Tiago and Perim, Eric and Pugno, Nicola M and Galvao, Douglas S},
url = {http://www.sciencedirect.com/science/article/pii/S0008622317303743},
doi = {10.1016/j.carbon.2017.04.018},
year = {2017},
date = {2017-04-14},
journal = {Carbon},
volume = {119},
pages = {431-437},
abstract = {Graphene nanowiggles (GNW) are graphene-based nanostructures obtained by making alternated regular cuts in pristine graphene nanoribbons. GNW were recently synthesized and it was demonstrated that they exhibit tunable electronic and magnetic properties by just varying their shape. Here, we have investigated the mechanical properties and fracture patterns of a large number of GNW of different shapes and sizes using fully atomistic reactive molecular dynamics simulations. Our results show that the GNW mechanical properties are strongly dependent on its shape and size and, as a general trend narrow sheets have larger ultimate strength and Young's modulus than wide ones. The estimated Young's modulus values were found to be in a range of ≈100−1000 GPa and the ultimate strength in a range of ≈20−110 GPa, depending on GNW shape. Also, super-ductile behavior under strain was observed for some structures.},
note = {See also ArxIv version: https://arxiv.org/abs/1702.01100},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Graphene nanowiggles (GNW) are graphene-based nanostructures obtained by making alternated regular cuts in pristine graphene nanoribbons. GNW were recently synthesized and it was demonstrated that they exhibit tunable electronic and magnetic properties by just varying their shape. Here, we have investigated the mechanical properties and fracture patterns of a large number of GNW of different shapes and sizes using fully atomistic reactive molecular dynamics simulations. Our results show that the GNW mechanical properties are strongly dependent on its shape and size and, as a general trend narrow sheets have larger ultimate strength and Young's modulus than wide ones. The estimated Young's modulus values were found to be in a range of ≈100−1000 GPa and the ultimate strength in a range of ≈20−110 GPa, depending on GNW shape. Also, super-ductile behavior under strain was observed for some structures.
57.
de Sousa, JM; Aguiar, AL; Girao, EC; Fonseca, Alexandre F; AG Filho, Souza; Galvao, Douglas S
Mechanical Properties and Fracture Patterns of Pentagraphene Membranes Online
2017, (preprint arXiv:1703.03789).
@online{deSousa2017,
title = {Mechanical Properties and Fracture Patterns of Pentagraphene Membranes},
author = {de Sousa, JM and Aguiar, AL and Girao, EC and Fonseca, Alexandre F and AG Filho, Souza and Galvao, Douglas S},
url = {https://arxiv.org/abs/1703.03789},
year = {2017},
date = {2017-03-10},
abstract = {Recently, a new two-dimensional carbon allotrope called pentagraphene (PG) was
proposed. PG exhibits mechanical and electronic interesting properties, including typical
band gap values of semiconducting materials. PG has a Cairo-tiling-like 2D lattice
of non coplanar pentagons and its mechanical properties have not been yet fully investigated.
In this work, we combined density functional theory (DFT) calculations and
reactive molecular dynamics (MD) simulations to investigate the mechanical properties
and fracture patterns of PG membranes under tensile strain. We show that PG
membranes can hold up to 20% of strain and that fracture occurs only after substantial
dynamical bond breaking and the formation of 7, 8 and 11 carbon rings and carbon
chains. The stress-strain behavior was observed to follow two regimes, one exhibiting linear elasticity followed by a plastic one, involving carbon atom re-hybridization with
the formation of carbon rings and chains. Our results also show that mechanically
induced structural transitions from PG to graphene is unlikely to occur, in contrast to
what was previously speculated in the literature.},
note = {preprint arXiv:1703.03789},
keywords = {},
pubstate = {published},
tppubtype = {online}
}
Recently, a new two-dimensional carbon allotrope called pentagraphene (PG) was
proposed. PG exhibits mechanical and electronic interesting properties, including typical
band gap values of semiconducting materials. PG has a Cairo-tiling-like 2D lattice
of non coplanar pentagons and its mechanical properties have not been yet fully investigated.
In this work, we combined density functional theory (DFT) calculations and
reactive molecular dynamics (MD) simulations to investigate the mechanical properties
and fracture patterns of PG membranes under tensile strain. We show that PG
membranes can hold up to 20% of strain and that fracture occurs only after substantial
dynamical bond breaking and the formation of 7, 8 and 11 carbon rings and carbon
chains. The stress-strain behavior was observed to follow two regimes, one exhibiting linear elasticity followed by a plastic one, involving carbon atom re-hybridization with
the formation of carbon rings and chains. Our results also show that mechanically
induced structural transitions from PG to graphene is unlikely to occur, in contrast to
what was previously speculated in the literature.
proposed. PG exhibits mechanical and electronic interesting properties, including typical
band gap values of semiconducting materials. PG has a Cairo-tiling-like 2D lattice
of non coplanar pentagons and its mechanical properties have not been yet fully investigated.
In this work, we combined density functional theory (DFT) calculations and
reactive molecular dynamics (MD) simulations to investigate the mechanical properties
and fracture patterns of PG membranes under tensile strain. We show that PG
membranes can hold up to 20% of strain and that fracture occurs only after substantial
dynamical bond breaking and the formation of 7, 8 and 11 carbon rings and carbon
chains. The stress-strain behavior was observed to follow two regimes, one exhibiting linear elasticity followed by a plastic one, involving carbon atom re-hybridization with
the formation of carbon rings and chains. Our results also show that mechanically
induced structural transitions from PG to graphene is unlikely to occur, in contrast to
what was previously speculated in the literature.
58.
Cristiano F Woellner Peter Samora Owuor, Tong Li
High Toughness in Ultralow Density Graphene Oxide Foam Journal Article
Em: Advanced Materials Interfaces, vol. 4, não 10, pp. 1700030, 2017.
@article{Owuor2017,
title = {High Toughness in Ultralow Density Graphene Oxide Foam},
author = {Peter Samora Owuor, Cristiano F Woellner, Tong Li, Soumya Vinod, Sehmus Ozden, Suppanat Kosolwattana, Sanjit Bhowmick, Luong Xuan Duy, Rodrigo V Salvatierra, Bingqing Wei, Syed AS Asif, James M Tour, Robert Vajtai, Jun Lou, Douglas S Galvão, Chandra Sekhar Tiwary, Pulickel Ajayan},
url = {http://onlinelibrary.wiley.com/doi/10.1002/admi.201700030/abstract },
doi = {10.1002/admi.201700030},
year = {2017},
date = {2017-03-01},
journal = {Advanced Materials Interfaces},
volume = {4},
number = {10},
pages = {1700030},
abstract = {Here, the scalable synthesis of low-density 3D macroscopic structure of graphene oxide (GO) interconnected with polydimethylsiloxane (PDMS) is reported. A controlled amount of PDMS is infused into the freeze-dried foam to result into a very rigid structure with improved mechanical properties, such as tensile plasticity and toughness. The PDMS wets the graphene oxide sheets and acts like glue between the 2D sheets. Molecular dynamics simulations are used to further elucidate the mechanisms of the interactions of graphene oxide layers with PDMS. The ability of using the interconnecting graphene oxide foam as an effective oil–water separator and stable insulating behavior to elevated temperatures are further demonstrated. The structural rigidity of the sample is also tested using laser impact and compared with GO foam.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Here, the scalable synthesis of low-density 3D macroscopic structure of graphene oxide (GO) interconnected with polydimethylsiloxane (PDMS) is reported. A controlled amount of PDMS is infused into the freeze-dried foam to result into a very rigid structure with improved mechanical properties, such as tensile plasticity and toughness. The PDMS wets the graphene oxide sheets and acts like glue between the 2D sheets. Molecular dynamics simulations are used to further elucidate the mechanisms of the interactions of graphene oxide layers with PDMS. The ability of using the interconnecting graphene oxide foam as an effective oil–water separator and stable insulating behavior to elevated temperatures are further demonstrated. The structural rigidity of the sample is also tested using laser impact and compared with GO foam.
59.
Splugues, Vinicius; da Silva Autreto, Pedro Alves; Galvao, Douglas S
Hydrogenation Dynamics of Biphenylene Carbon (Graphenylene) Membranes Journal Article
Em: MRS Advances, vol. 2017, pp. 1-6, 2017.
@article{Splugues2017,
title = {Hydrogenation Dynamics of Biphenylene Carbon (Graphenylene) Membranes},
author = {Splugues, Vinicius and da Silva Autreto, Pedro Alves and Galvao, Douglas S},
url = {https://www.cambridge.org/core/journals/mrs-advances/article/hydrogenation-dynamics-of-biphenylene-carbon-graphenylene-membranes/139DB900D41560D64F352A31CE219D3A},
doi = {10.1557/adv.2017.239},
year = {2017},
date = {2017-02-28},
journal = {MRS Advances},
volume = {2017},
pages = {1-6},
abstract = {The advent of graphene created a revolution in materials science. Because of this there is a renewed interest in other carbon-based structures. Graphene is the ultimate (just one atom thick) membrane. It has been proposed that graphene can work as impermeable membrane to standard gases, such argon and helium. Graphene-like porous membranes, but presenting larger porosity and potential selectivity would have many technological applications. Biphenylene carbon (BPC), sometimes called graphenylene, is one of these structures. BPC is a porous two-dimensional (planar) allotrope carbon, with its pores resembling typical sieve cavities and/or some kind of zeolites. In this work, we have investigated the hydrogenation dynamics of BPC membranes under different conditions (hydrogenation plasma density, temperature, etc.). We have carried out an extensive study through fully atomistic molecular dynamics (MD) simulations using the reactive force field ReaxFF, as implemented in the well-known Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) code. Our results show that the BPC hydrogenation processes exhibit very complex patterns and the formation of correlated domains (hydrogenated islands) observed in the case of graphene hydrogenation was also observed here. MD results also show that under hydrogenation BPC structure undergoes a change in its topology, the pores undergoing structural transformations and extensive hydrogenation can produce significant structural damages, with the formation of large defective areas and large structural holes, leading to structural collapse.
},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The advent of graphene created a revolution in materials science. Because of this there is a renewed interest in other carbon-based structures. Graphene is the ultimate (just one atom thick) membrane. It has been proposed that graphene can work as impermeable membrane to standard gases, such argon and helium. Graphene-like porous membranes, but presenting larger porosity and potential selectivity would have many technological applications. Biphenylene carbon (BPC), sometimes called graphenylene, is one of these structures. BPC is a porous two-dimensional (planar) allotrope carbon, with its pores resembling typical sieve cavities and/or some kind of zeolites. In this work, we have investigated the hydrogenation dynamics of BPC membranes under different conditions (hydrogenation plasma density, temperature, etc.). We have carried out an extensive study through fully atomistic molecular dynamics (MD) simulations using the reactive force field ReaxFF, as implemented in the well-known Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) code. Our results show that the BPC hydrogenation processes exhibit very complex patterns and the formation of correlated domains (hydrogenated islands) observed in the case of graphene hydrogenation was also observed here. MD results also show that under hydrogenation BPC structure undergoes a change in its topology, the pores undergoing structural transformations and extensive hydrogenation can produce significant structural damages, with the formation of large defective areas and large structural holes, leading to structural collapse.
60.
Bizao, Rafael A; Botari, Tiago; Perim, Eric; Pugno, Nicola M; Galvao, Douglas S
Mechanical Properties and Fracture Patterns of Graphene (Graphitic) Nanowiggles Online
2017, (preprint arXiv:1702.01100).
@online{Bizao2017,
title = {Mechanical Properties and Fracture Patterns of Graphene (Graphitic) Nanowiggles},
author = {Bizao, Rafael A and Botari, Tiago and Perim, Eric and Pugno, Nicola M and Galvao, Douglas S},
url = {https://arxiv.org/pdf/1702.01100.pdf},
year = {2017},
date = {2017-02-03},
abstract = {Graphene nanowiggles (GNW) are graphene-based nanostructures
obtained by making alternated regular cuts in pristine graphene nanoribbons.
GNW were recently synthesized and it was demonstrated that
they exhibit tunable electronic and magnetic properties by just varying
their shape. Here, we have investigated the mechanical properties and
fracture patterns of a large number of GNW of different shapes and
sizes using fully atomistic reactive molecular dynamics simulations.
Our results show that the GNW mechanical properties are strongly
dependent on its shape and size and, as a general trend narrow sheets
have larger ultimate strength and Young’s modulus than wide ones.
The estimated Young’s modulus values were found to be in a range of
≈ 100 − 1000 GPa and the ultimate strength in a range of ≈ 20 − 110
GPa, depending on GNW shape. Also, super-ductile behaviour under
strain was observed for some structures.},
note = {preprint arXiv:1702.01100},
keywords = {},
pubstate = {published},
tppubtype = {online}
}
Graphene nanowiggles (GNW) are graphene-based nanostructures
obtained by making alternated regular cuts in pristine graphene nanoribbons.
GNW were recently synthesized and it was demonstrated that
they exhibit tunable electronic and magnetic properties by just varying
their shape. Here, we have investigated the mechanical properties and
fracture patterns of a large number of GNW of different shapes and
sizes using fully atomistic reactive molecular dynamics simulations.
Our results show that the GNW mechanical properties are strongly
dependent on its shape and size and, as a general trend narrow sheets
have larger ultimate strength and Young’s modulus than wide ones.
The estimated Young’s modulus values were found to be in a range of
≈ 100 − 1000 GPa and the ultimate strength in a range of ≈ 20 − 110
GPa, depending on GNW shape. Also, super-ductile behaviour under
strain was observed for some structures.
obtained by making alternated regular cuts in pristine graphene nanoribbons.
GNW were recently synthesized and it was demonstrated that
they exhibit tunable electronic and magnetic properties by just varying
their shape. Here, we have investigated the mechanical properties and
fracture patterns of a large number of GNW of different shapes and
sizes using fully atomistic reactive molecular dynamics simulations.
Our results show that the GNW mechanical properties are strongly
dependent on its shape and size and, as a general trend narrow sheets
have larger ultimate strength and Young’s modulus than wide ones.
The estimated Young’s modulus values were found to be in a range of
≈ 100 − 1000 GPa and the ultimate strength in a range of ≈ 20 − 110
GPa, depending on GNW shape. Also, super-ductile behaviour under
strain was observed for some structures.
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