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Vertically aligned carbon nanotubes

Jonathan G Gigax, Philip D Bradford, Lin Shao
We studied the effects ion beam irradiation on carbon nanotube (CNT) yarns. CNT yarn was fabricated by drawing and spinning CNT sheets from a vertically aligned CNT forest. The yarn was irradiated by 2.5 MeV protons in either vacuum or air. Irradiation in air was achieved by directing the proton beam through a 0.025 mm thick Ti window. Irradiation in vacuum occurred at a pressure of <10(-6) torr at room temperature and at an elevated temperature of 600 °C. Tensile testing revealed that CNT yarn irradiated in air increased in tensile strength with increasing proton fluence...
July 27, 2017: Materials
Chih-Chung Su, Ting-Xu Chen, Shuo-Hung Chang
We fabricated a 3D sandwich hybrid material composed of graphene and vertically aligned carbon nanotube forests (VACNTs) using chemical vapor deposition. The graphene was first synthesized on Cu foil. Then it was transferred to a substrate which had a pre-deposited catalyst Fe film and a buffer film of Al₂O₃ for the growth of VACNTs. The VACNTs were grown underneath the graphene and lifted up the graphene. The graphene, with its edges anchored on the Al₂O₃, provided a constrained boundary condition for the VACNTs and hence affected the growth height and mechanical strength of the VACNTs...
February 21, 2017: Materials
Zhe Yin, Huimin Wang, Muqiang Jian, Yanshen Li, Kailun Xia, Mingchao Zhang, Chunya Wang, Qi Wang, Ming Ma, Quan-Shui Zheng, Yingying Zhang
The unique structure of a vertically aligned carbon nanotube (VACNT) array makes it behave most similarly to a blackbody. It is reported that the optical absorptivity of an extremely black VACNT array is about 0.98-0.99 over a large spectral range of 200 nm-200 μm, inspiring us to explore the performance of VACNT arrays in solar energy harvesting. In this work, we report the highly efficient steam generation simply by laminating a layer of VACNT array on the surface of water to harvest solar energy. It is found that under solar illumination the temperature of upper water can significantly increase with obvious water steam generated, indicating the efficient solar energy harvesting and local temperature rise by the thin layer of VACNTs...
August 16, 2017: ACS Applied Materials & Interfaces
Angel Perez Del Pino, Eniko Gyorgy, Islam Alshaikh, Fernando Pantoja-Suárez, José Luis Andújar, Esther Pascual, Roger Amade, Enric Bertran Serra
Carbon nanotubes-transition metal oxide systems are intensively studied due to their excellent properties for electrochemical applications. In this work, an innovative procedure is developed for the synthesis of vertically aligned multi-walled carbon nanotubes (VACNTs) coated with transition metal oxide nanostructures. VACNTs are grown by plasma enhanced chemical vapor deposition and coated with a manganese-based metal organic precursor (MOP) film based on manganese acetate solution. Subsequent UV pulsed laser irradiation induces the effective heating-decomposition of the MOP leading to the crystallization of manganese oxide nanostructures on the VACNT surface...
July 24, 2017: Nanotechnology
Mehdi Jahangiri
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 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...
July 12, 2017: Nanotechnology
Julia Patzsch, Deepu J Babu, Jörg J Schneider
Mesoscopic, nanoporous carbon tubes were synthesized by a combination of the Stoeber process and the use of electrospun macrosized polystyrene fibres as structure directing templates. The obtained carbon tubes have a macroporous nature characterized by a thick wall structure and a high specific surface area of approximately 500 m²/g resulting from their micro- and mesopores. The micropore regime of the carbon tubes is composed of turbostratic graphitic areas observed in the microstructure. The employed templating process was also used for the synthesis of silicon carbide tubes...
2017: Beilstein Journal of Nanotechnology
Linquan Ping, Peng-Xiang Hou, Chang Liu, Jincheng Li, Yang Zhao, Feng Zhang, Chaoqun Ma, Kaiping Tai, Hongtao Cong, Hui-Ming Cheng
A vertically aligned carbon nanotube (VACNT) array is a promising candidate for a high-performance thermal interface material in high-power microprocessors due to its excellent thermal transport property. However, its rough and entangled free tips always cause poor interfacial contact, which results in serious contact resistance dominating the total thermal resistance. Here, we employed a thin carbon cover to restrain the disorderly growth of the free tips of a VACNT array. As a result, all the free tips are seamlessly connected by this thin carbon cover and the top surface of the array is smoothed...
June 5, 2017: Nanoscale
Collins Nganou, Gerhard Lackner, Bezu Teschome, M Jamal Deen, Noam Adir, David Pouhe, Doru C Lupascu, Martin Mkandawire
Clues to designing highly efficient organic solar cells may lie in understanding the architecture of light-harvesting systems and exciton energy transfer (EET) processes in very efficient photosynthetic organisms. Here, we compare the kinetics of excitation energy tunnelling from the intact phycobilisome (PBS) light-harvesting antenna system to the reaction center in photosystem II in intact cells of the cyanobacterium Acaryochloris marina with the charge transfer after conversion of photons into photocurrent in vertically aligned carbon nanotube (va-CNT) organic solar cells with poly(3-hexyl)thiophene (P3HT) as the pigment...
June 7, 2017: ACS Applied Materials & Interfaces
Kang-Hyun Kim, Soon Kyu Hong, Nam-Su Jang, Sung-Hun Ha, Hyung Woo Lee, Jong-Man Kim
Wearable pressure sensors are crucial building blocks for potential applications in real-time health monitoring, artificial electronic skins, and human-to-machine interfaces. Here we present a highly sensitive, simple-architectured wearable resistive pressure sensor based on highly compliant yet robust carbon composite conductors made of a vertically aligned carbon nanotube (VACNT) forest embedded in a polydimethylsiloxane (PDMS) matrix with irregular surface morphology. A roughened surface of the VACNT/PDMS composite conductor is simply formed using a sandblasted silicon master in a low-cost and potentially scalable manner and plays an important role in improving the sensitivity of resistive pressure sensor...
May 15, 2017: ACS Applied Materials & Interfaces
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. Because of their highly coherent lattice structures, the outer BNNT serves as additional heat conducting path without impairing the thermal conductance of inner CNT...
April 24, 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 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)...
June 27, 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
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