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Giannetto M, Johnson EP, Watson A, Dimitrov E, Kurth A, Shi W, Fornasiero F, Meshot ER, Plata DL. Modifying the Molecular Structure of Carbon Nanotubes through Gas-Phase Reactants. ACS NANOSCIENCE AU 2023; 3:182-191. [PMID: 37096228 PMCID: PMC10119988 DOI: 10.1021/acsnanoscienceau.2c00052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Revised: 01/14/2023] [Accepted: 01/18/2023] [Indexed: 04/26/2023]
Abstract
Current approaches to carbon nanotube (CNT) synthesis are limited in their ability to control the placement of atoms on the surface of nanotubes. Some of this limitation stems from a lack of understanding of the chemical bond-building mechanisms at play in CNT growth. Here, we provide experimental evidence that supports an alkyne polymerization pathway in which short-chained alkynes directly incorporate into the CNT lattice during growth, partially retaining their side groups and influencing CNT morphology. Using acetylene, methyl acetylene, and vinyl acetylene as feedstock gases, unique morphological differences were observed. Interwall spacing, a highly conserved value in natural graphitic materials, varied to accommodate side groups, increasing systematically from acetylene to methyl acetylene to vinyl acetylene. Furthermore, attenuated total reflectance Fourier-transfer infrared spectroscopy (ATR-FTIR) illustrated the existence of intact methyl groups in the multiwalled CNTs derived from methyl acetylene. Finally, the nanoscale alignment of the CNTs grown in vertically aligned forests differed systematically. Methyl acetylene induced the most tortuous growth while CNTs from acetylene and vinyl-acetylene were more aligned, presumably due to the presence of polymerizable unsaturated bonds in the structure. These results demonstrate that feedstock hydrocarbons can alter the atomic-scale structure of CNTs, which in turn can affect properties on larger scales. This information could be leveraged to create more chemically and structurally complex CNT structures, enable more sustainable chemical pathways by avoiding the need for solvents and postreaction modifications, and potentially unlock experimental routes to a host of higher-order carbonaceous nanomaterials.
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Affiliation(s)
- Michael
J. Giannetto
- Department
of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut06511, United States
| | - Eric P. Johnson
- Department
of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut06511, United States
- Department
of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts02139, United States
| | - Adam Watson
- Department
of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut06511, United States
| | - Edgar Dimitrov
- Department
of Physics, University of California, Berkeley, Berkeley, California94720, United States
| | - Andrew Kurth
- Department
of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut06511, United States
| | - Wenbo Shi
- Department
of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts02139, United States
| | - Francesco Fornasiero
- Physical
and Life Sciences Directorate, Lawrence
Livermore National Laboratory, Livermore, California94550, United States
| | - Eric R. Meshot
- Physical
and Life Sciences Directorate, Lawrence
Livermore National Laboratory, Livermore, California94550, United States
| | - Desiree L. Plata
- Department
of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut06511, United States
- Department
of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts02139, United States
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2
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Morco SR, Jensen BD, Bowden AE. Curvature-induced defects on carbon-infiltrated carbon nanotube forests. RSC Adv 2022; 12:2115-2122. [PMID: 35425237 PMCID: PMC8979125 DOI: 10.1039/d1ra07243a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Accepted: 01/05/2022] [Indexed: 12/21/2022] Open
Abstract
A morphological study of the micro-scale defects induced by growing a carbon-infiltrated carbon nanotube (CICNT) forest on concave substrates was conducted. Two CICNT heights (roughly 60 μm and 400 μm) and 4 curvatures (1–4 mm ID) were studied in order to test the geometric limitations. Defects were categorized and quantified by scanning electron microscopy (SEM) of the tops and cross-sections. These deformities were categorized as increased roughness on the top surface, a corrugated (also called wavy or rippled) forest, a curved forest, an inside crevice where the forest separates, and increased forest density on the top surface. Roughness increased nearly 3-fold with the taller forest heights no matter the substrate curvature. Due to the geometric limitations of CICNT height and substrate curvature, all other microscale defects were significantly more present on samples with a small radius of curvature and a tall CICNT forest (p < 0.05). These buckling and warping types of defects were attributed to the increase in circumferential compression as the forest grows as well as the van der Waals interactions between the nanotubes. Because the fabrication process for CICNT involves growing a CNT forest and then infiltrating it with pyrolytic carbon, this work may be applicable to other CNT forests on concave substrates within these forest heights and substrate curvatures. A morphological study of the micro-scale defects induced by growing a carbon-infiltrated carbon nanotube (CICNT) forest on concave substrates was conducted.![]()
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Affiliation(s)
- Stephanie R Morco
- Brigham Young University, Department of Mechanical Engineering 350 Engineering Building Provo UT 84602 USA
| | - Brian D Jensen
- Brigham Young University, Department of Mechanical Engineering 350 Engineering Building Provo UT 84602 USA
| | - Anton E Bowden
- Brigham Young University, Department of Mechanical Engineering 350 Engineering Building Provo UT 84602 USA
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3
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Quantitative Evidence for the Dependence of Highly Crystalline Single Wall Carbon Nanotube Synthesis on the Growth Method. NANOMATERIALS 2021; 11:nano11123461. [PMID: 34947810 PMCID: PMC8706310 DOI: 10.3390/nano11123461] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 12/09/2021] [Accepted: 12/16/2021] [Indexed: 11/17/2022]
Abstract
We present a study quantitatively demonstrating that the method of synthesis (gas phase, fixed bed, non-fixed bed) represents a determining factor in the level of crystallinity in growing single wall carbon nanotubes (SWCNTs). Using far infrared spectroscopy, the "effective length" (associated with the level of crystallinity) was estimated for CNTs grown using various synthetic methods (lab-produced and supplemented by commercially purchased SWCNTs) as a metric for crystallinity (i.e., defect density). Analysis of the observed "effective lengths" showed that the SWCNTs fell into two general groups: long and short (high and low crystallinity) synthesized by gas-phase methods and all other supported catalyst methods, respectively. Importantly, the "long" group exhibited effective lengths in the range of 700-2200 nm, which was greater than double that of the typical values representing the "short" group (110-490 nm). These results highlight the significant difference in crystallinity. We interpret that the difference in the crystallinity stemmed from stress concentration at the nanotube-catalyst interface during the growth process, which originated from various sources of mismatch in growth rates (e.g., vertically aligned array) as well as impact stress from contact with other substrates during fluidization or rotation. These results are consistent with well-accepted belief, but now are demonstrated quantitatively.
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4
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Hines R, Hajilounezhad T, Love-Baker C, Koerner G, Maschmann MR. Growth and Mechanics of Heterogeneous, 3D Carbon Nanotube Forest Microstructures Formed by Sequential Selective-Area Synthesis. ACS APPLIED MATERIALS & INTERFACES 2020; 12:17893-17900. [PMID: 32208632 DOI: 10.1021/acsami.0c03082] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Three-dimensional carbon nanotube (CNT) forest microstructures are synthesized using sequenced, site-specific synthesis techniques. Thin-film layers of Al2O3 and Al2O3/Fe are patterned to support film-catalyst and floating-catalyst chemical vapor deposition (CVD) in specific areas. Al2O3 regions support only floating-catalyst CVD, whereas regions of layered Al2O3/Fe support both film- and floating-catalyst CNT growth. Sequenced application of the two CVD methods produced heterogeneous 3D CNT forest microstructures, including regions of only film-catalyst CNTs, only floating-catalyst CNTs, and vertically stacked layers of each. The compressive mechanical behavior of the heterogeneous CNT forests was evaluated, with the stacked layers exhibiting two distinct buckling plateaus. Finite element simulation of the stacked layers demonstrated that the relatively soft film-catalyst CNT forests were nearly fully buckled prior to large-scale deformation of the bottom floating-catalyst CNT forests.
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Affiliation(s)
- Ryan Hines
- Department of Mechanical and Aerospace Engineering, University of Missouri, Columbia, Missouri 65211, United States
| | - Taher Hajilounezhad
- Department of Mechanical and Aerospace Engineering, University of Missouri, Columbia, Missouri 65211, United States
| | - Cole Love-Baker
- Department of Chemical Engineering, University of South Carolina, Columbia, South Carolina 29208, United States
| | - Gordon Koerner
- Department of Mechanical and Aerospace Engineering, University of Missouri, Columbia, Missouri 65211, United States
| | - Matthew R Maschmann
- Department of Mechanical and Aerospace Engineering, University of Missouri, Columbia, Missouri 65211, United States
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5
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Brown J, Hajilounezhad T, Dee NT, Kim S, Hart AJ, Maschmann MR. Delamination Mechanics of Carbon Nanotube Micropillars. ACS APPLIED MATERIALS & INTERFACES 2019; 11:35221-35227. [PMID: 31478639 DOI: 10.1021/acsami.9b09979] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The adhesion of carbon nanotube (CNT) forests to their growth substrate is a critical concern for many applications. Here, we measured the delamination force of CNT forest micropillars using in situ scanning electron microscopy (SEM) tensile testing. A flat tip with epoxy adhesive first established contact with the top surface of freestanding CNT pillars and then pulled the pillars in displacement-controlled tension until delamination was observed. An average delamination stress of 6.1 MPa was measured, based on the full pillar cross-sectional area, and detachment was observed to occur between catalyst particles and the growth substrate. Finite element simulations of CNT forest delamination show that force and strain are heterogeneously distributed among CNTs during tensile loading and that CNTs progressively lose adhesion with increased displacement. Based on combined experiments and simulations, an adhesion strength of approximately 350 MPa was estimated between each CNT and the substrate. These findings provide important insight into CNT applications such as thermal interfaces, mechanical sensors, and structural composites while also suggesting a potential upper limit of tensile forces allowed during CNT forest synthesis.
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Affiliation(s)
- Josef Brown
- Department of Mechanical and Aerospace Engineering , University of Missouri , Columbia , Missouri 65201 , United States
| | - Taher Hajilounezhad
- Department of Mechanical and Aerospace Engineering , University of Missouri , Columbia , Missouri 65201 , United States
| | - Nicholas T Dee
- Department of Mechanical Engineering , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Sanha Kim
- Department of Mechanical Engineering , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - A John Hart
- Department of Mechanical Engineering , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Matthew R Maschmann
- Department of Mechanical and Aerospace Engineering , University of Missouri , Columbia , Missouri 65201 , United States
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6
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Lee J, Abdulhafez M, Bedewy M. Data Analytics Enables Significant Improvement of Robustness in Chemical Vapor Deposition of Carbon Nanotubes Based on Vacuum Baking. Ind Eng Chem Res 2019. [DOI: 10.1021/acs.iecr.9b01725] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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7
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Douglas A, Carter R, Li M, Pint CL. Toward Small-Diameter Carbon Nanotubes Synthesized from Captured Carbon Dioxide: Critical Role of Catalyst Coarsening. ACS APPLIED MATERIALS & INTERFACES 2018; 10:19010-19018. [PMID: 29715008 DOI: 10.1021/acsami.8b02834] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Small-diameter carbon nanotubes (CNTs) often require increased sophistication and control in synthesis processes, but exhibit improved physical properties and greater economic value over their larger-diameter counterparts. Here, we study mechanisms controlling the electrochemical synthesis of CNTs from the capture and conversion of ambient CO2 in molten salts and leverage this understanding to achieve the smallest-diameter CNTs ever reported in the literature from sustainable electrochemical synthesis routes, including some few-walled CNTs. Here, Fe catalyst layers are deposited at different thicknesses onto stainless steel to produce cathodes, and atomic layer deposition of Al2O3 is performed on Ni to produce a corrosion-resistant anode. Our findings indicate a correlation between the CNT diameter and Fe metal layer thickness following electrochemical catalyst reduction at the cathode-molten salt interface. Further, catalyst coarsening during long duration synthesis experiments leads to a 2× increase in average diameters from 3 to 60 min durations, with CNTs produced after 3 min exhibiting a tight diameter distribution centered near ∼10 nm. Energy consumption analysis for the conversion of CO2 into CNTs demonstrates energy input costs much lower than the value of CNTs-a concept that strictly requires and motivates small-diameter CNTs-and is more favorable compared to other costly CO2 conversion techniques that produce lower-value materials and products.
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Affiliation(s)
- Anna Douglas
- SkyNano LLC , Oak Ridge , Tennessee 37830 , United States
| | | | | | - Cary L Pint
- Vanderbilt Institute of Nanoscale Science and Engineering , Nashville , Tennessee 37235 , United States
- SkyNano LLC , Oak Ridge , Tennessee 37830 , United States
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8
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Jahangiri M. Systematic periodicity in waviness of vertically aligned carbon nanotubes explained by helical buckling. NANOTECHNOLOGY 2017; 28:375706. [PMID: 28699920 DOI: 10.1088/1361-6528/aa7f6a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A hypothesis is proposed in this work to account for the geometry of individual vertically aligned carbon nanotubes (VACNTs) that not only justifies the directionality of their growth, but also explains the origin of the waviness frequently reported for these nanotube forests. Such waviness has fundamental effects on the transport/conduction properties of VACNTs, either through or along them, regarding phenomena such as mass, stress, heat and electricity. Despite the general opinion about randomness of carbon nanotubes (CNTs) tortuosity, we demonstrate here that rules of helical buckling of tubular strings is applicable to VACNTs, based on which a regular 3D helical geometry is proposed for VACNTs, with a 2D sine wave shape side-profile. In this framework, gradual increase of the total free surface energy by growth of CNTs ensues their partial cohesion, driven by van der Waals interactions, to reduce the excess surface energy. On the other hand, their cohesion is accompanied by their deformation and loss of straightness, which in turn, translates to buildup of an elastic strain energy in the system. The balance of the two energies along with the spatial constraints on each CNT at its contact points with neighboring CNTs, is manifested in its helical buckling, that is systematically influenced by nanostructural characteristics of VACNTs, such as their diameter, wall thickness and inter-CNT spacing.
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Affiliation(s)
- Mehdi Jahangiri
- Department of Mechanical Engineering, Shiraz University, Shiraz, Iran
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9
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Meshot ER, Zwissler DW, Bui N, Kuykendall TR, Wang C, Hexemer A, Wu KJJ, Fornasiero F. Quantifying the Hierarchical Order in Self-Aligned Carbon Nanotubes from Atomic to Micrometer Scale. ACS NANO 2017; 11:5405-5416. [PMID: 28414424 DOI: 10.1021/acsnano.6b08042] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Fundamental understanding of structure-property relationships in hierarchically organized nanostructures is crucial for the development of new functionality, yet quantifying structure across multiple length scales is challenging. In this work, we used nondestructive X-ray scattering to quantitatively map the multiscale structure of hierarchically self-organized carbon nanotube (CNT) "forests" across 4 orders of magnitude in length scale, from 2.0 Å to 1.5 μm. Fully resolved structural features include the graphitic honeycomb lattice and interlayer walls (atomic), CNT diameter (nano), as well as the greater CNT ensemble (meso) and large corrugations (micro). Correlating orientational order across hierarchical levels revealed a cascading decrease as we probed finer structural feature sizes with enhanced sensitivity to small-scale disorder. Furthermore, we established qualitative relationships for single-, few-, and multiwall CNT forest characteristics, showing that multiscale orientational order is directly correlated with number density spanning 109-1012 cm-2, yet order is inversely proportional to CNT diameter, number of walls, and atomic defects. Lastly, we captured and quantified ultralow-q meridional scattering features and built a phenomenological model of the large-scale CNT forest morphology, which predicted and confirmed that these features arise due to microscale corrugations along the vertical forest direction. Providing detailed structural information at multiple length scales is important for design and synthesis of CNT materials as well as other hierarchically organized nanostructures.
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Affiliation(s)
- Eric R Meshot
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory , 7000 East Avenue, Livermore, California 94550, United States
| | - Darwin W Zwissler
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory , 7000 East Avenue, Livermore, California 94550, United States
| | - Ngoc Bui
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory , 7000 East Avenue, Livermore, California 94550, United States
| | | | | | | | - Kuang Jen J Wu
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory , 7000 East Avenue, Livermore, California 94550, United States
| | - Francesco Fornasiero
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory , 7000 East Avenue, Livermore, California 94550, United States
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10
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Shi W, Li J, Polsen ES, Oliver CR, Zhao Y, Meshot ER, Barclay M, Fairbrother DH, Hart AJ, Plata DL. Oxygen-promoted catalyst sintering influences number density, alignment, and wall number of vertically aligned carbon nanotubes. NANOSCALE 2017; 9:5222-5233. [PMID: 28397885 DOI: 10.1039/c6nr09802a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A lack of synthetic control and reproducibility during vertically aligned carbon nanotube (CNT) synthesis has stifled many promising applications of organic nanomaterials. Oxygen-containing species are particularly precarious in that they have both beneficial and deleterious effects and are notoriously difficult to control. Here, we demonstrated diatomic oxygen's ability, independent of water, to tune oxide-supported catalyst thin film dewetting and influence nanoscale (diameter and wall number) and macro-scale (alignment and density) properties for as-grown vertically aligned CNTs. In particular, single- or few-walled CNT forests were achieved at very low oxygen loading, with single-to-multi-walled CNT diameters ranging from 4.8 ± 1.3 nm to 6.4 ± 1.1 nm over 0-800 ppm O2, and an expected variation in alignment, where both were related to the annealed catalyst morphology. Morphological differences were not the result of subsurface diffusion, but instead occurred via Ostwald ripening under several hundred ppm O2, and this effect was mitigated by high H2 concentrations and not due to water vapor (as confirmed in O2-free water addition experiments), supporting the importance of O2 specifically. Further characterization of the interface between the Fe catalyst and Al2O3 support revealed that either oxygen-deficit metal oxide or oxygen-adsorption on metals could be functional mechanisms for the observed catalyst nanoparticle evolution. Taken as a whole, our results suggest that the impacts of O2 and H2 on the catalyst evolution have been underappreciated and underleveraged in CNT synthesis, and these could present a route toward facile manipulation of CNT forest morphology through control of the reactive gaseous atmosphere alone.
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Affiliation(s)
- Wenbo Shi
- Department of Chemical and Environmental Engineering, Yale University, New Haven, CT, USA.
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11
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Balakrishnan V, Bedewy M, Meshot ER, Pattinson SW, Polsen ES, Laye F, Zakharov DN, Stach EA, Hart AJ. Real-Time Imaging of Self-Organization and Mechanical Competition in Carbon Nanotube Forest Growth. ACS NANO 2016; 10:11496-11504. [PMID: 27959511 DOI: 10.1021/acsnano.6b07251] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The properties of carbon nanotube (CNT) networks and analogous materials comprising filamentary nanostructures are governed by the intrinsic filament properties and their hierarchical organization and interconnection. As a result, direct knowledge of the collective dynamics of CNT synthesis and self-organization is essential to engineering improved CNT materials for applications such as membranes and thermal interfaces. Here, we use real-time environmental transmission electron microscopy (E-TEM) to observe nucleation and self-organization of CNTs into vertically aligned forests. Upon introduction of the carbon source, we observe a large scatter in the onset of nucleation of individual CNTs and the ensuing growth rates. Experiments performed at different temperatures and catalyst particle densities show the critical role of CNT density on the dynamics of self-organization; low-density CNT nucleation results in the CNTs becoming pinned to the substrate and forming random networks, whereas higher density CNT nucleation results in self-organization of the CNTs into bundles that are oriented perpendicular to the substrate. We also find that mechanical coupling between growing CNTs alters their growth trajectory and shape, causing significant deformations, buckling, and defects in the CNT walls. Therefore, it appears that CNT-CNT coupling not only is critical for self-organization but also directly influences CNT quality and likely the resulting properties of the forest. Our findings show that control of the time-distributed kinetics of CNT nucleation and bundle formation are critical to manufacturing well-organized CNT assemblies and that E-TEM can be a powerful tool to investigate the mesoscale dynamics of CNT networks.
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Affiliation(s)
- Viswanath Balakrishnan
- Department of Mechanical Engineering and Laboratory for Manufacturing and Productivity, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
- School of Engineering, Indian Institute of Technology Mandi , Mandi, Himachal Pradesh 175001, India
| | - Mostafa Bedewy
- Department of Mechanical Engineering and Laboratory for Manufacturing and Productivity, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
- Department of Mechanical Engineering, University of Michigan , 2350 Hayward Street, Ann Arbor, Michigan 48109, United States
- Department of Industrial Engineering, University of Pittsburgh , 3700 O'Hara Street, Pittsburgh, Pennsylvania 15261, United States
| | - Eric R Meshot
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory , Livermore, California 94550, United States
| | - Sebastian W Pattinson
- Department of Mechanical Engineering and Laboratory for Manufacturing and Productivity, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Erik S Polsen
- Department of Mechanical Engineering, University of Michigan , 2350 Hayward Street, Ann Arbor, Michigan 48109, United States
| | - Fabrice Laye
- Department of Mechanical Engineering, University of Michigan , 2350 Hayward Street, Ann Arbor, Michigan 48109, United States
| | - Dmitri N Zakharov
- Center for Functional Nanomaterials, Brookhaven National Laboratory , Upton, New York 11973, United States
| | - Eric A Stach
- Center for Functional Nanomaterials, Brookhaven National Laboratory , Upton, New York 11973, United States
| | - A John Hart
- Department of Mechanical Engineering and Laboratory for Manufacturing and Productivity, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
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12
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Husmann S, Zarbin AJG. Design of a Prussian Blue Analogue/Carbon Nanotube Thin-Film Nanocomposite: Tailored Precursor Preparation, Synthesis, Characterization, and Application. Chemistry 2016; 22:6643-53. [DOI: 10.1002/chem.201504444] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Indexed: 11/07/2022]
Affiliation(s)
- Samantha Husmann
- Department of Chemistry; Universidade Federal do Paraná-UFPR, CP 19081, CEP; 81531-980 Curitiba, Paraná Brazil
| | - Aldo J. G. Zarbin
- Department of Chemistry; Universidade Federal do Paraná-UFPR, CP 19081, CEP; 81531-980 Curitiba, Paraná Brazil
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13
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Abstract
Aligned carbon nanotube arrays with stochastic three-dimensional morphologies underscore the importance of nanofiber waviness and present how existing morphology models can be modified to account for this non-ideality.
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Affiliation(s)
- Itai Y. Stein
- Department of Mechanical Engineering
- Massachusetts Institute of Technology
- Cambridge
- USA
| | - Brian L. Wardle
- Department of Aeronautics and Astronautics
- Massachusetts Institute of Technology
- Cambridge
- USA
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14
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Stein IY, Lewis DJ, Wardle BL. Aligned carbon nanotube array stiffness from stochastic three-dimensional morphology. NANOSCALE 2015; 7:19426-19431. [PMID: 26553970 DOI: 10.1039/c5nr06436h] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The landmark theoretical properties of low dimensional materials have driven more than a decade of research on carbon nanotubes (CNTs) and related nanostructures. While studies on isolated CNTs report behavior that aligns closely with theoretical predictions, studies on cm-scale aligned CNT arrays (>10(10) CNTs) oftentimes report properties that are orders of magnitude below those predicted by theory. Using simulated arrays comprised of up to 10(5) CNTs with realistic stochastic morphologies, we show that the CNT waviness, quantified via the waviness ratio (w), is responsible for more than three orders of magnitude reduction in the effective CNT stiffness. Also, by including information on the volume fraction scaling of the CNT waviness, the simulation shows that the observed non-linear enhancement of the array stiffness as a function of the CNT close packing originates from the shear and torsion deformation mechanisms that are governed by the low shear modulus (∼1 GPa) of the CNTs.
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Affiliation(s)
- Itai Y Stein
- Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, USA
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15
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Bedewy M, Farmer B, Hart AJ. Synergetic chemical coupling controls the uniformity of carbon nanotube microstructure growth. ACS NANO 2014; 8:5799-5812. [PMID: 24794192 DOI: 10.1021/nn500698z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Control of the uniformity of vertically aligned carbon nanotube structures (CNT "forests"), in terms of both geometry and nanoscale morphology (density, diameter, and alignment), is crucial for applications. Many studies report complex and sometimes unexplained spatial variations of the height of macroscopic CNT forests, as well as variations among micropillars grown from lithographically patterned catalyst arrays. We present a model for chemically coupled CNT growth, which describes the origins of synergetic growth effects among CNT micropillars in proximity. Via this model, we propose that growth of CNTs is locally enhanced by active species that are catalytically produced at the substrate-bound nanoparticles. The local concentration of these active species modulates the growth rate of CNTs, in a spatially dependent manner driven by diffusion and local generation/consumption at the catalyst sites. Through experiments and numerical simulations, we study how the uniformity of CNT micropillars can be influenced by their size and spacing within arrays and predict the widely observed abrupt transition between tangled and vertical CNT growth by assigning a threshold concentration of active species. This mathematical framework enables predictive modeling of spatially dependent CNT growth, as well as design of catalyst patterns to achieve engineered uniformity.
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Affiliation(s)
- Mostafa Bedewy
- Mechanosynthesis Group, Department of Mechanical Engineering, University of Michigan , 2350 Hayward Street, Ann Arbor, Michigan 48109, United States
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16
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Stein IY, Lachman N, Devoe ME, Wardle BL. Exohedral physisorption of ambient moisture scales non-monotonically with fiber proximity in aligned carbon nanotube arrays. ACS NANO 2014; 8:4591-4599. [PMID: 24684313 DOI: 10.1021/nn5002408] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Here we present a study on the presence of physisorbed water on the surface of aligned carbon nanotubes (CNTs) in ambient conditions, where the wet CNT array mass can be more than 200% larger than that of dry CNTs, and modeling indicates that a water layer >5 nm thick can be present on the outer CNT surface. The experimentally observed nonlinear and non-monotonic dependence of the mass of adsorbed water on the CNT packing (volume fraction) originates from two competing modes. Physisorbed water cannot be neglected in the design and fabrication of materials and devices using nanowires/nanofibers, especially CNTs, and further experimental and ab initio studies on the influence of defects on the surface energies of CNTs, and nanowires/nanofibers in general, are necessary to understand the underlying physics and chemistry that govern this system.
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Affiliation(s)
- Itai Y Stein
- Department of Mechanical Engineering, ‡Department of Aeronautics and Astronautics, and §Department of Materials Science and Engineering, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
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Oliver CR, Westrick W, Koehler J, Brieland-Shoultz A, Anagnostopoulos-Politis I, Cruz-Gonzalez T, Hart AJ. Robofurnace: a semi-automated laboratory chemical vapor deposition system for high-throughput nanomaterial synthesis and process discovery. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2013; 84:115105. [PMID: 24289435 PMCID: PMC3838427 DOI: 10.1063/1.4826275] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Accepted: 10/06/2013] [Indexed: 05/16/2023]
Abstract
Laboratory research and development on new materials, such as nanostructured thin films, often utilizes manual equipment such as tube furnaces due to its relatively low cost and ease of setup. However, these systems can be prone to inconsistent outcomes due to variations in standard operating procedures and limitations in performance such as heating and cooling rates restrict the parameter space that can be explored. Perhaps more importantly, maximization of research throughput and the successful and efficient translation of materials processing knowledge to production-scale systems, relies on the attainment of consistent outcomes. In response to this need, we present a semi-automated lab-scale chemical vapor deposition (CVD) furnace system, called "Robofurnace." Robofurnace is an automated CVD system built around a standard tube furnace, which automates sample insertion and removal and uses motion of the furnace to achieve rapid heating and cooling. The system has a 10-sample magazine and motorized transfer arm, which isolates the samples from the lab atmosphere and enables highly repeatable placement of the sample within the tube. The system is designed to enable continuous operation of the CVD reactor, with asynchronous loading∕unloading of samples. To demonstrate its performance, Robofurnace is used to develop a rapid CVD recipe for carbon nanotube (CNT) forest growth, achieving a 10-fold improvement in CNT forest mass density compared to a benchmark recipe using a manual tube furnace. In the long run, multiple systems like Robofurnace may be linked to share data among laboratories by methods such as Twitter. Our hope is Robofurnace and like automation will enable machine learning to optimize and discover relationships in complex material synthesis processes.
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Affiliation(s)
- C Ryan Oliver
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA
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Pathak S, Mohan N, Decolvenaere E, Needleman A, Bedewy M, Hart AJ, Greer JR. Local relative density modulates failure and strength in vertically aligned carbon nanotubes. ACS NANO 2013; 7:8593-8604. [PMID: 24001107 DOI: 10.1021/nn402710j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Micromechanical experiments, image analysis, and theoretical modeling revealed that local failure events and compressive stresses of vertically aligned carbon nanotubes (VACNTs) were uniquely linked to relative density gradients. Edge detection analysis of systematically obtained scanning electron micrographs was used to quantify a microstructural figure-of-merit related to relative local density along VACNT heights. Sequential bottom-to-top buckling and hardening in stress-strain response were observed in samples with smaller relative density at the bottom. When density gradient was insubstantial or reversed, bottom regions always buckled last, and a flat stress plateau was obtained. These findings were consistent with predictions of a 2D material model based on a viscoplastic solid with plastic non-normality and a hardening-softening-hardening plastic flow relation. The hardening slope in compression generated by the model was directly related to the stiffness gradient along the sample height, and hence to the local relative density. These results demonstrate that a microstructural figure-of-merit, the effective relative density, can be used to quantify and predict the mechanical response.
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Affiliation(s)
- Siddhartha Pathak
- Materials Science, California Institute of Technology (Caltech) , Pasadena, California, United States
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Park SJ, Schmidt AJ, Bedewy M, Hart AJ. Measurement of carbon nanotube microstructure relative density by optical attenuation and observation of size-dependent variations. Phys Chem Chem Phys 2013; 15:11511-9. [PMID: 23748864 DOI: 10.1039/c3cp51415c] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Sei Jin Park
- Mechanosynthesis Group, Department of Mechanical Engineering, University of Michigan, 2350 Hayward Street, Ann Arbor, Michigan 48109, USA
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