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Vertically aligned carbon nanotubes

Ning Yang, Meng Li, Jörg Patscheider, Seul Ki Youn, Hyung Gyu Park
A precise control of the dimension of carbon nanotubes (CNTs) in their vertical array could enable many promising applications in various fields. Here, we demonstrate the growth of vertically aligned, single-walled CNTs (VA-SWCNTs) with diameters in the sub-1.5-nm range (0.98 ± 0.24 nm), by engineering a catalyst support layer of alumina via thermal annealing followed by ion beam treatment. We find out that the ion beam bombardment on the alumina allows the growth of ultra-narrow nanotubes, whereas the thermal annealing promotes the vertical alignment at the expense of enlarged diameters; in an optimal combination, these two effects can cooperate to produce the ultra-narrow VA-SWCNTs...
April 21, 2017: Scientific Reports
Lin Jing, Majid Kabiri Samani, Bo Liu, Hongling Li, Roland Yingjie Tay, Siu Hon Tsang, Olivier Cometto, Andreas Nylander, Johan Liu, Edwin Hang Tong Teo, Alfred Iing Yoong Tok
We demonstrate the thermal conductivity enhancement of the vertically aligned carbon nanotube (CNT) arrays (from ~15.5 to 29.5 W/mK, ~90% increase) by encapsulating outer boron nitride nanotube (BNNT, 0.97 nm-thick with ~3-4 walls). The heat transfer enhancement mechanism of the coaxial C@BNNT was further revealed by molecular dynamics simulations. Owing to their highly coherent lattice structures, the outer BNNT serves as additional heat conducting path without impairing the thermal conductance of inner CNT...
April 21, 2017: ACS Applied Materials & Interfaces
Eric R Meshot, Darwin W Zwissler, Ngoc Bui, Tevye R Kuykendall, Cheng Wang, Alexander Hexemer, Kuang Jen J Wu, Francesco Fornasiero
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 four 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)...
April 17, 2017: ACS Nano
Wenbo Shi, Jinjing Li, Erik S Polsen, C Ryan Oliver, Yikun Zhao, Eric R Meshot, Michael Barclay, D Howard Fairbrother, A John Hart, Desiree L Plata
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...
April 20, 2017: Nanoscale
Sherif Okeil, Jan Krausmann, Inga Dönges, Sandra Pfleger, Jörg Engstler, Jörg J Schneider
ZnS nanoparticles have been synthesized on vertically aligned carbon nanotubes by gas-phase conversion of ZnO nanoparticles which have been tethered on vertically aligned carbon nanotubes using atomic layer deposition (ALD). The resulting ZnO@CNT nanocomposite has been converted to ZnS@CNT by reacting it with hydrogen sulfide using thioacetamide as a precursor. The composition of the resulting nanocomposite could be tuned from a mixed ternary ZnS/ZnO@CNT nanocomposite to a pure ZnS@CNT nanocomposite. At the same time, the amount of wurtzite and sphalerite phases varies in the ZnS@CNT nanocomposite...
April 19, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Ramathasan Thevamaran, Deepika Saini, Mehmet Karakaya, Jingyi Zhu, Ramakrishna Podila, Apparao M Rao, Chiara Daraio
We describe the super compressible and highly recoverable response of bucky sponges as they are struck by a heavy flat-punch striker. The bucky sponges studied here are structurally stable, self-assembled mixtures of multiwalled carbon nanotubes (MWCNTs) and carbon fibers (CFs). We engineered the microstructure of the sponges by controlling their porosity using different CF contents. Their mechanical properties and energy dissipation characteristics during impact loading are presented as a function of their composition...
May 5, 2017: Nanotechnology
Guan Wu, Pengfeng Tan, Dongxing Wang, Zhe Li, Lu Peng, Ying Hu, Caifeng Wang, Wei Zhu, Su Chen, Wei Chen
Supercapacitors, which store electrical energy through reversible ion on the surface of conductive electrodes have gained enormous attention for variously portable energy storage devices. Since the capacitive performance is mainly determined by the structural and electrochemical properties of electrodes, the electrodes become more crucial to higher performance. However, due to the disordered microstructure and low electrochemical activity of electrode for ion tortuous migration and accumulation, the supercapacitors present relatively low capacitance and energy density...
March 8, 2017: Scientific Reports
Theerapol Thurakitseree, Christian Kramberger, Pisith Singjai, Shigeo Maruyama
Structure control such as diameter changes along single-walled carbon nanotubes (SWNTs) can be achieved in arrays of vertically aligned (VA-) SWNTs by switching the feedstock during growth. The local nature of the macroscopic transition from one diameter to another is then questioned as one can either envisage seamless transitions or discontinuous individual SWNTs. Here, we demonstrate that encapsulated molecules can serve as markers to doubtlessly identify seamless interconnections in macroscopic samples. A migration of nitrogen molecules inside the continuous SWNTs is observed using bulk scale measurements on double-layered SWNT arrays synthesized from different carbon/nitrogen feedstocks...
March 7, 2017: Nanoscale
Jiadong Sheng, Qi Zhu, Xian Zeng, Zhaohui Yang, Xiaohua Zhang
Ion transport plays an important role in solar-to-electricity conversion, drug delivery, and a variety of biological processes. Carbon nanotube (CNT) is a promising material as an ion transporter in the applications of the mimicking of natural ion channels, desalination, and energy harvesting. Here, we demonstrate a unique, enhanced ion transport through a vertically aligned multiwall CNT membrane after the application of an electric potential across CNT membranes. Interestingly, electrowetting arising from the application of an electric potential is critical for the enhancement of overall ion transport rate through CNT membranes...
March 29, 2017: ACS Applied Materials & Interfaces
Hong Zhu, Fengxia Chang, Zhiwei Zhu
How to align the single-walled carbon nanotubes (SWCNTs) onto the electrode vertically and to control their density and orientation are still a major challenge. Theoretically, properly selected chiral SWCNTs can discriminate enantiomers through their different dielectric response to the adsorption of chiral species, few reports can confirm this theoretic model. Herein, we presented a new strategy to fabricate SWCNTs array-based electrochemical chiral sensor. Carboxylated chiral SWCNTs were vertically attached to the oxidized glass carbon electrode with ethylenediamine as a linker by electrosynthesis...
May 1, 2017: Talanta
Wojciech Szmyt, Carlos Guerra, Ivo Utke
In this work we modelled the diffusive transport of a dilute gas along arrays of randomly distributed, vertically aligned nanocylinders (nanotubes or nanowires) as opposed to gas diffusion in long pores, which is described by the well-known Knudsen theory. Analytical expressions for (i) the gas diffusion coefficient inside such arrays, (ii) the time between collisions of molecules with the nanocylinder walls (mean time of flight), (iii) the surface impingement rate, and (iv) the Knudsen number of such a system were rigidly derived based on a random-walk model of a molecule that undergoes memoryless, diffusive reflections from nanocylinder walls assuming the molecular regime of gas transport...
2017: Beilstein Journal of Nanotechnology
Josefine Hirschfeld, Eser M Akinoglu, Dieter C Wirtz, Achim Hoerauf, Isabelle Bekeredjian-Ding, Søren Jepsen, El-Mustapha Haddouti, Andreas Limmer, Michael Giersig
Bacterial biofilms cause a considerable amount of prosthetic joint infections every year, resulting in morbidity and expensive revision surgery. To address this problem, surface modifications of implant materials such as carbon nanotube (CNT) coatings have been investigated in the past years. CNTs are biologically compatible and can be utilized as drug delivery systems. In this study, multi-walled carbon nanotube (MWCNT) coated TiAl6V4 titanium alloy discs were fabricated and impregnated with Rifampicin, and tested for their ability to prevent biofilm formation over a period of ten days...
January 20, 2017: Nanomedicine: Nanotechnology, Biology, and Medicine
Heena K Mutha, Yuan Lu, Itai Y Stein, H Jeremy Cho, Matthew E Suss, Tahar Laoui, Carl V Thompson, Brian L Wardle, Evelyn N Wang
Vertically aligned one-dimensional nanostructure arrays are promising in many applications such as electrochemical systems, solar cells, and electronics, taking advantage of high surface area per unit volume, nanometer length scale packing, and alignment leading to high conductivity. However, many devices need to optimize arrays for device performance by selecting an appropriate morphology. Developing a simple, non-invasive tool for understanding the role of pore volume distribution and interspacing would aid in the optimization of nanostructure morphologies in electrodes...
December 29, 2016: Nanotechnology
Changjian Zhou, Richard Senegor, Zachary Baron, Yihan Chen, Salahuddin Raju, Anshul A Vyas, Mansun Chan, Yang Chai, Cary Y Yang
Carbon nanotubes (CNTs) and graphene are potential candidates for future interconnect materials. CNTs are promising on-chip via interconnect materials due to their readily formed vertical structures, their current-carrying capacity, which is much larger than existing on-chip interconnect materials such as copper and tungsten, and their demonstrated ability to grow in patterned vias with sub-50 nm widths; meanwhile, graphene is suitable for horizontal interconnects. However, they both present the challenge of having high-resistance contacts with other conductors...
February 3, 2017: Nanotechnology
Takashi Tsuji, Kenji Hata, Don N Futaba, Shunsuke Sakurai
An unexpected 5000% increase in growth efficiency and high (95%) single-wall selectivity synthesis of vertically aligned carbon nanotubes (CNTs) was shown from Fe catalysts supported on a sputtered MgO underlayer from a simple underlayer treatment, i.e., annealing treatment. In this way, millimeter-scale single-wall carbon nanotube "forests" could be synthesized in a 10 min time, which has never been previously reported for MgO catalyst underlayer or any underlayer besides Al2O3. This level of efficiency and characterized SWCNT properties were similar to those grown using Al2O3 underlayers...
December 28, 2016: Journal of the American Chemical Society
Yixuan Zhou, Yiwen E, Xinlong Xu, Weilong Li, Huan Wang, Lipeng Zhu, Jintao Bai, Zhaoyu Ren, Li Wang
Spatial dispersion effect of aligned carbon nanotubes (CNTs) in the terahertz (THz) region has significance for both theoretical and applied consideration due to the unique intrinsically anisotropic physical properties of CNTs. Herein, we report the angular dependent reflection of p-polarized THz wave from vertically aligned multi-walled CNT arrays in both experiment and theory. The spectra indicate that the reflection depends on the film thickness of vertically aligned CNTs, the incident angle, and the frequency...
December 14, 2016: Scientific Reports
Heena K Mutha, Yuan Lu, Itai Stein, H Jeremy Cho, Matthew Suss, Tahar Laoui, Carl Thompson, Brian Wardle, Evelyn Wang
Vertically aligned one-dimensional nanostructure arrays are promising in many applications such as electrochemical systems, solar cells, and electronics, taking advantage of high surface area per unit volume, nanometer length scale packing, and alignment leading to high conductivity. However, many devices need to optimize arrays for device performance by selecting an appropriate morphology. Developing a simple, non-invasive tool for understanding the role of pore volume distribution and interspacing would aid in the optimization of nanostructure morphologies in electrodes...
December 13, 2016: Nanotechnology
Sanghyun Hong, Troy Lundstrom, Ranajay Ghosh, Hamed Abdi, Ji Hao, Sun Kyoung Jeoung, Paul Su, Jonghwan Suhr, Ashkan Vaziri, Nader Jalili, Yung Joon Jung
We have created a multifunctional dry adhesive film with transferred vertically aligned carbon nanotubes (VA-CNTs). This unique VA-CNT film was fabricated by a multistep transfer process, converting the flat and uniform bottom of VA-CNTs grown on atomically flat silicon wafer substrates into the top surface of an adhesive layer. Unlike as-grown VA-CNTs, which have a nonuniform surface, randomly entangled CNT arrays, and a weak interface between the CNTs and substrates, this transferred VA-CNT film shows an extremely high coefficient of static friction (COF) of up to 60 and a shear adhesion force 30 times higher (12 N/cm(2)) than that of the as-grown VA-CNTs under a very small preloading of 0...
December 14, 2016: ACS Applied Materials & Interfaces
Viswanath Balakrishnan, Mostafa Bedewy, Eric R Meshot, Sebastian W Pattinson, Erik S Polsen, Fabrice Laye, Dmitri N Zakharov, Eric A Stach, A John Hart
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...
December 27, 2016: ACS Nano
Hangbo Zhao, Christine Jacob, Howard A Stone, A John Hart
Understanding of the liquid imbibition dynamics in nanoporous materials is important to advances in chemical separations, phase change heat transfer, electrochemical energy storage, and diagnostic assays. We study the liquid imbibition behavior in films of ceramic-coated vertically aligned carbon nanotubes (CNTs). The nanoscale porosity of the films is tuned by conformal ceramic coating via atomic layer deposition (ALD), enabling stable liquid imbibition and precise measurement of the imbibition dynamics without capillary densification of the CNTs...
December 6, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
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