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  1. Article ; Online: On the Mechanical Properties of Popgraphene-Based Nanotubes: a Reactive Molecular Dynamics Study.

    Brandão, W H S / Aguiar, A L / Ribeiro, L A / Galvão, D S / De Sousa, J M

    Chemphyschem : a European journal of chemical physics and physical chemistry

    2021  Volume 22, Issue 7, Page(s) 701–707

    Abstract: Carbon-based tubular materials have sparked a great interest in future electronics and optoelectronics device applications. In this work, we computationally studied the mechanical properties of nanotubes generated from popgraphene (PopNTs). Popgraphene ... ...

    Abstract Carbon-based tubular materials have sparked a great interest in future electronics and optoelectronics device applications. In this work, we computationally studied the mechanical properties of nanotubes generated from popgraphene (PopNTs). Popgraphene is a 2D carbon allotrope composed of 5-8-5 rings. We carried out fully atomistic reactive (ReaxFF) molecular dynamics for PopNTs of different chiralities (
    Language English
    Publishing date 2021-03-09
    Publishing country Germany
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2025223-7
    ISSN 1439-7641 ; 1439-4235
    ISSN (online) 1439-7641
    ISSN 1439-4235
    DOI 10.1002/cphc.202000840
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  2. Article: Flat-to-Flat Polymerization of Single-Walled Carbon Nanotubes under High Pressure Mediated by Carbon Chain Encapsulation

    Ferreira, R. S / Aguiar, A. L / Alencar, R. S / San-Miguel, A / Filho, A. G. Souza

    Journal of physical chemistry. 2021 June 07, v. 125, no. 23

    2021  

    Abstract: In this work, we studied single-walled carbon nanotube bundles filled with linear carbon chains under high-pressure conditions. We used density functional theory (DFT) to explore new polymerized high-pressure phases of carbon nanotubes due to cross- ... ...

    Abstract In this work, we studied single-walled carbon nanotube bundles filled with linear carbon chains under high-pressure conditions. We used density functional theory (DFT) to explore new polymerized high-pressure phases of carbon nanotubes due to cross-linking between carbon chains and the internal surface of nanotubes. Carbon nanotubes are known to transform their circular cross section into elliptical and finally peanut-shaped, which characterizes the collapse of the structure. High-pressure cycles (compression–decompression) up to a maximum of 40–50 GPa reveal the production of new polymerized carbon nanotube phases characterized by sp³ bonds in flat regions of collapsed phases. Such new carbon bonds differ from those of conventional edge-to-edge polymerization obtained for highly curved regions of collapsed tubes. We also investigated the details of the geometry, electronic structure, and thermal stability of such new polymerized hybrid structures. We observed that carbon nanotube properties are deeply changed after high-pressure cycles. Furthermore, molecular dynamics calculations at higher temperatures suggest that such type of flat-to-flat polymerization of carbon nanotubes could be more stable than conventional edge-to-edge polymerization.
    Keywords carbon ; carbon nanotubes ; crosslinking ; density functional theory ; encapsulation ; geometry ; molecular dynamics ; polymerization ; thermal stability
    Language English
    Dates of publication 2021-0607
    Size p. 12857-12869.
    Publishing place American Chemical Society
    Document type Article
    Note NAL-AP-2-clean
    ISSN 1932-7455
    DOI 10.1021/acs.jpcc.1c02044
    Database NAL-Catalogue (AGRICOLA)

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  3. Article: Pressure-induced structural transformations on linear carbon chains encapsulated in carbon nanotubes: A potential route for obtaining longer chains and ultra-hard composites

    Neves, W.Q. / Ferreira, R.S. / Kim, Y.A. / Endo, M. / Choi, G.B. / Muramatsu, H. / Aguiar, A.L. / Alencar, R.S. / Souza Filho, A.G.

    Carbon. 2022 Mar. 18,

    2022  

    Abstract: In this paper, we report high-pressure Raman experiments (0 − 28 GPa) in two different systems, i.e., linear carbon chains encapsulated by multi-walled (Cₙ@MWCNTs) and double-walled (Cₙ@DWCNTs) carbon nanotubes. By running high-pressure cycles, it is ... ...

    Abstract In this paper, we report high-pressure Raman experiments (0 − 28 GPa) in two different systems, i.e., linear carbon chains encapsulated by multi-walled (Cₙ@MWCNTs) and double-walled (Cₙ@DWCNTs) carbon nanotubes. By running high-pressure cycles, it is observed basically two changes in the Raman spectra of chains that are the softening and disappearance of Cₙ modes. We attributed the irreversible redshift of the Cₙ band to the coalescence between adjacent chains. On the other hand, the disappearance of the Cₙ band at the onset of the CNT collapse pressure is assigned to the tube-chain cross-linking. This effect appears to be independent of the Cₙ length and the number of walls of the tubes, depending only on the innermost CNT diameter. We show that the pressure to coalesce longer chains is higher than 10 GPa. Density functional theory and molecular dynamics calculations were performed in order to support the interpretation of experimental data. The calculations show an irreversible pressure-induced softening of frequency of the confined linear carbon chain. Furthermore, molecular dynamics calculations showed that coalescence between the shorter chains occurs in a region of lower pressure than that of the longer chains, thus supporting the experimental observations. Our findings shed new light on the understanding of the Cₙ@CNT system stability and pave the way for using high-pressure to obtain ultra-long chains (at lower pressures) and ultra-hard composites (at higher pressures).
    Keywords carbon ; carbon nanotubes ; crosslinking ; density functional theory ; molecular dynamics
    Language English
    Dates of publication 2022-0318
    Publishing place Elsevier Ltd
    Document type Article
    Note Pre-press version
    ISSN 0008-6223
    DOI 10.1016/j.carbon.2022.03.045
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  4. Book ; Online: First-Principles and Reactive Molecular Dynamics Study of the Elastic Properties of Pentahexoctite-based Nanotubes

    Brandão, W. H. S. / De Sousa, J. M. / Aguiar, A. L. / Galvão, D. S. / Junior, L. A. Ribeiro / Fonseca, Alexandre F.

    2023  

    Abstract: Pentahexoctite (PH) is a pure sp$^2$ hybridized planar carbon allotrope whose structure consists of a symmetric combination of pentagons, hexagons, and octagons. The proposed PH structure was shown to be an intrinsically metallic material exhibiting good ...

    Abstract Pentahexoctite (PH) is a pure sp$^2$ hybridized planar carbon allotrope whose structure consists of a symmetric combination of pentagons, hexagons, and octagons. The proposed PH structure was shown to be an intrinsically metallic material exhibiting good mechanical and thermal stability. PH nanotubes (PHNTs) have also been proposed, and their properties were obtained from first principles calculations. Here, we carried out fully-atomistic simulations, combining reactive (ReaxFF) molecular dynamics (MD) and density functional theory (DFT) methods, to study the PHNTs elastic properties and fracture patterns. We have investigated the mechanical properties behavior as a function of the tube diameter and temperature regimes. Our results showed that the PHNTs, when subjected to large tensile strains, undergo abrupt structural transitions exhibiting brittle fracture patterns without a plastic regime.

    Comment: 10 figures, 2 tables
    Keywords Condensed Matter - Materials Science ; Condensed Matter - Mesoscale and Nanoscale Physics
    Subject code 541
    Publishing date 2023-03-07
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  5. Book ; Online: A Computational Study On the Mechanical Properties of Pentahexoctite Single-layer

    Brandão, W. H. S. / Aguiar, A. L. / Júnior, L. A. Ribeiro / Galvão, D. S. / De Sousa, J. M.

    Combining DFT and Classical Molecular Dynamics Simulations

    2022  

    Abstract: Studies aimed at designing new allotropic forms of carbon have received much attention. Recently, a new 2D graphene-like allotrope named Pentahexoctite was theoretically proposed. Pentahexoctite has a metallic signature, and its structure consists of ... ...

    Abstract Studies aimed at designing new allotropic forms of carbon have received much attention. Recently, a new 2D graphene-like allotrope named Pentahexoctite was theoretically proposed. Pentahexoctite has a metallic signature, and its structure consists of continuous 5-6-8 rings of carbon atoms with sp2 hybridization. Here, we carried out fully-atomistic computational simulations, combining reactive (ReaxFF) molecular dynamics (MD) and density functional theory (DFT) methods, to study the elastic properties and fracture patterns of Pentahexoctite monolayer. Results revealed a Young's Modulus of 0.74 TPa, smaller than the graphene one (about 1.0 TPa). The Pentahexoctite monolayer, when subjected to a critical strain, goes directly from elastic to completely fractured regimes. This process occurs with no plasticity stages between these two regimes. Importantly, graphene presents a similar fracture process. The elastic properties calculated with both DFT and MD are in good agreement. Keywords: Reactive Molecular Dynamics, DFT, Mechanical Properties, Carbon Allotrope
    Keywords Condensed Matter - Materials Science ; 00-XX ; J.2.0 ; I.6.0
    Subject code 541
    Publishing date 2022-07-20
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  6. Article ; Online: Breeding objectives and selection criteria of a participatory community-based breeding programme of goats and sheep.

    de Aguiar, A L / da Silva, R R / Alves, S M / da Silva, L P / de Morais, O R / Lobo, R N B

    Tropical animal health and production

    2020  Volume 52, Issue 4, Page(s) 1933–1943

    Abstract: The absence of formal markets and the large variability of genetic groups and production systems of goats and sheep in developing countries hinder the implementation of traditional breeding programmes. Community-based breeding programmes (CBBP) for these ...

    Abstract The absence of formal markets and the large variability of genetic groups and production systems of goats and sheep in developing countries hinder the implementation of traditional breeding programmes. Community-based breeding programmes (CBBP) for these species have been shown to be effective in these countries. In these programmes, the definition of the objectives and criteria of selection is done in a participatory way, which takes into account the desires and needs of the local farmers. We aimed to define the objectives and criteria of a CBBP for goats and sheep in the Inhamuns region, Ceará, Brazil, using a participatory rural appraisal (PRA). This methodology, which consist in an approach that aims to incorporate the knowledge and opinions of rural people in the planning and management of development projects and programmes, was performed in seven districts of two towns of the region (Tauá and Parambu). One hundred twenty-two farmer families participated in the survey. The PRA was able to provide important information, and its results showed that breeders of this region keep flocks of goats and sheep for social, economic and cultural benefits. In order of importance, the main objectives for goat farming were personal fulfilment (PERF), food source for family (FSF), income generation (INCG), savings (SAV) and cultural/family traditions (CULT), while for sheep farming were CULT, FSF, SAV, PERF and INCG. Disease resistance (RDI), adaptability (ADP), fertility (FERT), growth rate (GRA), host resistance of worms (HRW), body conformation (BC), temperament (TEM), longevity (LONG), body size (BSIZ), age at first kidding (AFK) and milk yield (MIY) were the main selection criteria that farmers use for goats. The most important selection criteria used for selecting sheep were ADP, RDI, HRW, GRA, FERT, LONG, BC, BS and age at first lambing. According to these objectives and criteria, the CBBP must consider the adaptation of the animals to the climate and management conditions of the region, the resistance to diseases and productive performance.
    MeSH term(s) Adult ; Aged ; Aged, 80 and over ; Animal Husbandry ; Animals ; Brazil ; Breeding/methods ; Community Participation ; Farmers/psychology ; Female ; Goats ; Humans ; Male ; Middle Aged ; Sheep, Domestic ; Young Adult
    Language English
    Publishing date 2020-01-22
    Publishing country United States
    Document type Journal Article
    ZDB-ID 603363-5
    ISSN 1573-7438 ; 0049-4747
    ISSN (online) 1573-7438
    ISSN 0049-4747
    DOI 10.1007/s11250-020-02209-6
    Database MEDical Literature Analysis and Retrieval System OnLINE

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    In stock of ZB MED Cologne/Königswinter

    Zs.B 2159: Show issues Location:
    Je nach Verfügbarkeit (siehe Angabe bei Bestand)
    bis Jg. 2021: Bestellungen von Artikeln über das Online-Bestellformular
    ab Jg. 2022: Lesesaal (EG)

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  7. Book ; Online: On the Mechanical Properties of Popgraphene-based Nanotubes

    Brandão, W. H. S. / Aguiar, A. L. / Ribeiro, L. A. / Galvão, D. S. / De Sousa, J. M.

    a Reactive Molecular Dynamics Study

    2020  

    Abstract: Carbon-based tubular materials have sparked a great interest for future electronics and optoelectronics device applications. In this work, we computationally studied the mechanical properties of nanotubes generated from popgraphene (PopNTs). Popgraphene ... ...

    Abstract Carbon-based tubular materials have sparked a great interest for future electronics and optoelectronics device applications. In this work, we computationally studied the mechanical properties of nanotubes generated from popgraphene (PopNTs). Popgraphene is a 2D carbon allotrope composed of $5-8-5$ rings. We carried out fully atomistic reactive (ReaxFF) molecular dynamics for PopNTs of different chiralities ($(n,0)$ and $(0,n)$) and/or diameters and at different temperatures (from 300 up to 1200K). Results showed that the tubes are thermally stable (at least up to 1200K). All tubes presented stress/strain curves with a quasi-linear behavior followed by an abrupt drop of stress values. Interestingly, armchair-like PopNTs ($(0,n)$) can stand a higher strain load before fracturing when contrasted to the zigzag-like ones ($(n,0)$). Moreover, it was obtained that the Young's modulus ($Y_{Mod}$) (750-900 GPa) and ultimate strength ($\sigma_{US}$) (120-150 GPa) values are similar to the ones reported for conventional armchair and zigzag carbon nanotubes. $Y_{Mod}$ values obtained for PopNTs are not significantly temperature dependent. While the $\sigma_{US}$ values for the $(0,n)$ showed a quasi-linear dependence with the temperature, the $(n,0)$ exhibited no clear trends.

    Comment: 19 pages, 7 figures, Submitted to ChemPhysChem
    Keywords Condensed Matter - Materials Science ; Condensed Matter - Mesoscale and Nanoscale Physics
    Subject code 541
    Publishing date 2020-10-07
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  8. Article: Breeding objectives and selection criteria of a participatory community-based breeding programme of goats and sheep

    de Aguiar, A. L / da Silva, R. R / Alves, S. M / da Silva, L. P / de Morais, O. R / Lobo, R. N. B

    Tropical animal health and production. 2020 July, v. 52, no. 4

    2020  

    Abstract: The absence of formal markets and the large variability of genetic groups and production systems of goats and sheep in developing countries hinder the implementation of traditional breeding programmes. Community-based breeding programmes (CBBP) for these ...

    Abstract The absence of formal markets and the large variability of genetic groups and production systems of goats and sheep in developing countries hinder the implementation of traditional breeding programmes. Community-based breeding programmes (CBBP) for these species have been shown to be effective in these countries. In these programmes, the definition of the objectives and criteria of selection is done in a participatory way, which takes into account the desires and needs of the local farmers. We aimed to define the objectives and criteria of a CBBP for goats and sheep in the Inhamuns region, Ceará, Brazil, using a participatory rural appraisal (PRA). This methodology, which consist in an approach that aims to incorporate the knowledge and opinions of rural people in the planning and management of development projects and programmes, was performed in seven districts of two towns of the region (Tauá and Parambu). One hundred twenty-two farmer families participated in the survey. The PRA was able to provide important information, and its results showed that breeders of this region keep flocks of goats and sheep for social, economic and cultural benefits. In order of importance, the main objectives for goat farming were personal fulfilment (PERF), food source for family (FSF), income generation (INCG), savings (SAV) and cultural/family traditions (CULT), while for sheep farming were CULT, FSF, SAV, PERF and INCG. Disease resistance (RDI), adaptability (ADP), fertility (FERT), growth rate (GRA), host resistance of worms (HRW), body conformation (BC), temperament (TEM), longevity (LONG), body size (BSIZ), age at first kidding (AFK) and milk yield (MIY) were the main selection criteria that farmers use for goats. The most important selection criteria used for selecting sheep were ADP, RDI, HRW, GRA, FERT, LONG, BC, BS and age at first lambing. According to these objectives and criteria, the CBBP must consider the adaptation of the animals to the climate and management conditions of the region, the resistance to diseases and productive performance.
    Keywords animal health ; body conformation ; body size ; climate ; disease resistance ; farmers ; goats ; income ; longevity ; milk yield ; rural population ; sheep ; surveys ; temperament ; Brazil
    Language English
    Dates of publication 2020-07
    Size p. 1933-1943.
    Publishing place Springer Netherlands
    Document type Article
    Note NAL-AP-2-clean
    ZDB-ID 603363-5
    ISSN 1573-7438 ; 0049-4747
    ISSN (online) 1573-7438
    ISSN 0049-4747
    DOI 10.1007/s11250-020-02209-6
    Database NAL-Catalogue (AGRICOLA)

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    In stock of ZB MED Bonn / Germany

    Z 2667: Show issues

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  9. Article: Raman resonance tuning of quaterthiophene in filled carbon nanotubes at high pressures

    Alencar, R.S / Aguiar, A.L / Ferreira, R.S / Chambard, R / Jousselme, B / Bantignies, J.-L / Weigel, C / Clément, S / Aznar, R / Machon, D / Souza Filho, A.G / San-Miguel, A / Alvarez, L

    Carbon. 2021 Mar., v. 173

    2021  

    Abstract: Filling carbon nanotubes with molecules is a route for the development of electronically modified one-dimensional hybrid structures for which the interplay between the electronic structure of molecules and nanotubes is a key factor. Tuning these energy ... ...

    Abstract Filling carbon nanotubes with molecules is a route for the development of electronically modified one-dimensional hybrid structures for which the interplay between the electronic structure of molecules and nanotubes is a key factor. Tuning these energy levels with external parameters is an interesting strategy for the engineering of new devices and materials. Here we show that the hybrid system composed by quaterthiophene (4T) molecules confined in single-walled carbon nanotubes, presents a piezo-Raman-resonance of the molecule vibrational pattern. This behavior manifests as a rapid pressure induced enhancement of the 4T Raman mode intensities compared to the tubes G-band Raman modes. Density functional theory calculations allow to explain the spectral behaviour through the pressure-enhanced quaterthiophene resonance evolution. By increasing pressure, the tube cross-section deformation leads to a reduction of the intermolecular distance, to the splitting of the molecular levels and then to an increase of resonance channels. Calculations and experiments converge to the 4T piezo-resonance scenario associated with the pressure-induced nanotube radial collapse observed at about 0.8 GPa. Our findings offer possibilities for the development of pressure transducers based on molecule-filled carbon nanotubes.
    Keywords carbon ; carbon nanotubes ; deformation ; density functional theory ; energy ; spectral analysis
    Language English
    Dates of publication 2021-03
    Size p. 163-173.
    Publishing place Elsevier Ltd
    Document type Article
    Note NAL-AP-2-clean
    ISSN 0008-6223
    DOI 10.1016/j.carbon.2020.10.083
    Database NAL-Catalogue (AGRICOLA)

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  10. Book ; Online: On the Elastic Properties of Single-Walled Phagraphene Nanotubes

    Junior, M. L. Pereira / De Sousa, J. M. / Brandão, W. H. S. / Aguiar, A. L. / Bizão, R. A. / Junior, L. A. Ribeiro / Galvão, D. S.

    2020  

    Abstract: Phagraphene (PhaG) is a quasi-planar 2D structure composed of $5-6-7$ ring sequence. We have investigated the structural and mechanical properties of phagraphene nanotubes (PhaNTs) through fully atomistic reactive molecular dynamics (MD) simulations. For ...

    Abstract Phagraphene (PhaG) is a quasi-planar 2D structure composed of $5-6-7$ ring sequence. We have investigated the structural and mechanical properties of phagraphene nanotubes (PhaNTs) through fully atomistic reactive molecular dynamics (MD) simulations. For comparison purposes, the results were also contrasted to similar carbon nanotubes (CNTs). Results showed that PhaNTs and CNTs present similar brittle fracture mechanisms. The Young's modulus values obtained for PhaNTs were smaller than the corresponding ones for CNTs. Both, PhaNTs and CNTs, present equivalent fracture strains ranging between 15\%-20\%. For the ultimate strength values, CNTs present values about 30\% higher than the corresponding ones for PhaNTs.

    Comment: 11 pages and 04 pages
    Keywords Condensed Matter - Materials Science ; 00-XX ; J.2 ; I.6
    Publishing date 2020-07-03
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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