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Now showing 1 - 10 of 48

The effect of MWCNTs/GNs hybrid addition on the tribological and rheological properties of lubricating engine oil
(1970-01-01)
Kamel, Bahaa M.
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El-Kashif, Emad
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Hoziefa, W.
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Shiba, Mohamed S.
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Elshalakany, Abou Bakr
Oils and grease have beneficial effects on moving parts such as connecting rod, gears, shafts, and engine to reduce wear and friction. The properties of lubricants such as tribological and rheological properties are an important role in oils and grease characterization. Nano additives on lubricant oils play an important role in anti-wear; reduce the coefficient of friction and enhance the rheological properties. The Tribological and rheological behavior of base oil 15W50 which have different concentrations of multi-wall Carbon Nanotubes (MWCNTs) (0.5, 1, 1.5, and 2 wt%), and constant amount of graphene nanosheets (GNSs) (0.5 wt%) were investigated. This research is the first one in studying the effect of hybrid nano additives of (MWCNTs) and (GNs) on the tribological and rheological properties of lubricant oils. Tribological characterization was carried out on four ball testing model under different loads (200, 400, 600, and 800 N). The kinematic viscosity, flash point, pour point, and thermal conductivity of nanofluid added 15W50 lubricant are estimated and compared with base oil. The results showed that nano additives improve the wear scar and coefficient of friction by 78% and 48%, respectively. The flash point, thermal conductivity, kinematic viscosity, and pour point, were improved by 15%, 77%, 76.8%, and 20%, respectively compared with the base oil. The hybrid addition of CNTs/GNs nanoparticles enhanced the properties of 15W50 engine oil.
Conductive films based on sandwich structures of carbon nanotubes/silver nanowires for stretchable interconnects
(2019-06-07)
Jheng, Li-Cheng
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Hsiao, Chi-Hui
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Ko, Wen-Ching
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Hsu, Steve Lien-Chung
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Huang, Yu-Lun
A variety of conductive films made of a hybrid of two conductive nanomaterials have been used as stretchable electrodes or interconnectors, desirable for stretchable electronic devices. Their intrinsic stretchability of electrical conductivity allows for accommodating mechanical strain to a certain extent under various deformations. However, few efforts have been made to enhance the interactions between two conductive components in a hybrid system. Herein, we reported new conductive films with tri-layer sandwich structures based on carbon nanotubes (CNTs) and Ag nanowires (NWs), encapsulated in silicone rubber, exhibited high stretchability along with insignificant piezoresistivity. They are suitable to be stretchable interconnectors. A successive vacuum filtration method was used to stack the conductive components layer by layer. The effects of the stacking sequence and the interactions between layers on the stretchability and stability of the electrical properties under mechanical deformations were studied. In the case of a tri-layer conductive film comprising two CNT outer layers and one AgNW central layer in the presence of enhanced interfacial interactions, it showed exceptionally durability in withstanding repetitive deformations.
Process and properties of the carbon nanotube assisted LiCoO2 thin-film battery electrode by pulsed laser deposition
(2009-11-01)
Lo, An-Ya
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Sun, Chuan-Shu
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Tseng, Wen-Shou
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Kuo, Cheng-Tzu
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材料科學與工程學系
In this study, a pulsed laser deposition process was developed to deposit a carbon nanotube (CNT) assisted LiCoO2 electrode to improve its power density. The electrodes were deposited on Pt-coated Si substrates with Ar and O-2 as sputtering gases and LiCoO2+C as the target. The results indicate that the working pressure is the most important parameter to control the composition of the electrode. Therefore, electrodes with a three-layer structure (i.e., LiCoO2-rich/CNT-rich/LiCoO2-rich) were fabricated by a three-step deposition process by varying the pressures from 13 to 1.3x10(4) Pa and then 13 Pa again, and it was found that the charge/discharge capacity became approximately 1.5 times greater than that in the corresponding electrode without a CNT-rich layer. The results also indicate that a higher substrate temperature is favorable for improving the crystallinity of the electrode to approach LiCoO2 crystals.
Low-temperature CVD growth of carbon nanotubes for field emission application
(2007-03-01)
Chen, Kuang-Chung
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Chen, Chia-Fu
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Lee, Jen-Hao
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Wu, Tai-Lin
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Hwang, Chian-Liang
For field emission application, carbon nanotube emitters were synthesized on catalyst-mixed thick-film electrode lower than 500 degrees C by chemical vapor deposition (CVD) method. Mixtures of Ni/tetraethyl silicate (TEOS) and conducting Ag powders were applied to fabricate the electrode by screen-printing processes. These processes are simple, low cost and easy to scale up for large sized panels. The field emission properties performed uniform emission image and high brightness (no less than 500 nits). The turn-on electric field was about 3.85 V/mu m with an emission current destiny of 10 mu A/cm(2), and the achieved current density was 1 mA/cm(2) driven by 5 V/mu m. (c) 2006 Elsevier B.V. All rights reserved.
Time-dependent density functional theory for quantum transport
(2010-09-21)
Zheng, Xiao
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Chen, GuanHua
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Mo, Yan
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Koo, SiuKong
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Tian, Heng
Based on our earlier works [X. Zheng , Phys. Rev. B 75, 195127 (2007); J. S. Jin , J. Chem. Phys. 128, 234703 (2008)], we propose a rigorous and numerically convenient approach to simulate time-dependent quantum transport from first-principles. The proposed approach combines time-dependent density functional theory with quantum dissipation theory, and results in a useful tool for studying transient dynamics of electronic systems. Within the proposed exact theoretical framework, we construct a number of practical schemes for simulating realistic systems such as nanoscopic electronic devices. Computational cost of each scheme is analyzed, with the expected level of accuracy discussed. As a demonstration, a simulation based on the adiabatic wide-band limit approximation scheme is carried out to characterize the transient current response of a carbon nanotube based electronic device under time-dependent external voltages. (c) 2010 American Institute of Physics. [doi:10.1063/1.3475566]
ZnO-Coated Carbon Nanotubes: Inter-Diffusion of Carboxyl Groups and Enhanced Photocurrent Generation
(2015-03-16)
Hung, Chia-I
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Wen, Hua-Chiang
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Lai, Yao-Cheng
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Chang, Shih-Hsin
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Chou, Wu-Ching
ZnO is a defect-governed oxide and emits light at both visible and UV regimes. This work employs atomic layer deposition to produce oxide particles on oxygenated carbon nanotubes, and the composites only show emission profiles at short wavelengths. The quenching of defect-related emissions at long wavelengths is verified, owing to carboxyl diffusion into oxygen vacancies, and doping is supported by ZnCO3 formation in oxide lattice. Fully coated tubes display an increased photocurrent and the quantum efficiency increases by 22% relative to the bare nanotubes.
Time-dependent density functional theory for quantum transport
(2010-09-21)
Zheng, Xiao
;
Chen, GuanHua
;
Mo, Yan
;
Koo, SiuKong
;
Tian, Heng
Based on our earlier works [X. Zheng , Phys. Rev. B 75, 195127 (2007); J. S. Jin , J. Chem. Phys. 128, 234703 (2008)], we propose a rigorous and numerically convenient approach to simulate time-dependent quantum transport from first-principles. The proposed approach combines time-dependent density functional theory with quantum dissipation theory, and results in a useful tool for studying transient dynamics of electronic systems. Within the proposed exact theoretical framework, we construct a number of practical schemes for simulating realistic systems such as nanoscopic electronic devices. Computational cost of each scheme is analyzed, with the expected level of accuracy discussed. As a demonstration, a simulation based on the adiabatic wide-band limit approximation scheme is carried out to characterize the transient current response of a carbon nanotube based electronic device under time-dependent external voltages. (c) 2010 American Institute of Physics. [doi:10.1063/1.3475566]
Comparative studies on field emission properties of carbon-based materials
(2000-04-01)
Chen, KH
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Wu, JJ
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Chen, LC
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Wen, CY
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Kichambare, PD
Comparative studies on field emission properties of various carbon-related materials including diamond, amorphous carbon, SiCN films, SiCN nanorods, and carbon nanotubes are presented. While diamond is well known for its potential use in cold cathodes, the emission current of a hydrogen-treated diamond film is relatively small compared to that of amorphous carbon or diamond-like-carbon film. Meanwhile, carbon nanotubes have demonstrated large emission currents at much lower threshold voltages, showing their potential for applications. However, the emission from carbon nanotubes is subjected to significant decay under long-term operation. The emission current and long-term stability can be improved using a new SiCN compound with nanorod morphology. The effective barrier height and the held enhancement factor derived from the Fowler-Nordheim equation are discussed in this paper. (C) 2000 Elsevier Science S.A. All rights reserved.
Field electron emission from C-based emitters and devices
(2001)
Chen, LC
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Hong, WK
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Tarntair, FG
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Chen, KJ
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Lin, JB
We present the fabrication, characterization and field emission properties of various C-based emitters and devices, which include (1) the diode-type emitters consisting of arrays of carbon-coated Si microtips and carbon nanotubes (CNTs), (2) CNT triodes. and (3) thin-film-transistor (TFT)-controlled CNT field emission devices (FEDs). All the CNTs were deposited by microwave plasma-enhanced chemical vapor deposition. For the first type, each array contains 50 x 50 emitting cells and each individual cell is 3 microns square. Compared to the Si microtips with bias-assisted carburization or diamond cladding, enhancement in field emission by several orders of magnitude of the CNTs arrays was observed. While the diode-type CNT emitters easily achieve the goal of drawing high electron emission current at low macroscopic field, their long-term stability is not satisfactory for practical applications. For the triode-type CNT-FEDs, vertically aligned CNTs with controlled length were directly grown on the Fe-coated Si substrate pre-patterned by photolithography and etching using oxide as the gate insulator, and the emission current from the CNTs was controlled via the gate voltage. For the TFT-controlled CNT-FEDs, CNTs were selectively grown on the drain region of the TFT and the emission current from the CNTs was controlled via the TFT drain current. It should be mentioned that the fabrication procedures are straightforward and can be integrated with current technologies in the well-established semiconductor industry. Both the triode-type CNTs as well as the TFT-controlled CNT-FEDs have demonstrated improved controllability and stability while maintaining high emission current density.
Effects of the catalyst pretreatment on CO2 sensors made by carbon nanotubes
(2008-04-01)
Huang, C. S.
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Huang, B. R.
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Hsiao, C. H.
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Yeh, C. Y.
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Huang, C. C.
A novel CO2 sensor was made by carbon nanotubes (CNTs). The CNTs were synthesized by catalystic thermal chemical vapour deposition at 700 degrees C. Prior to the synthesis, the Fe catalysts were pretreated by H-2 plasma for different times. Two terminal resistance of the as-grown CNTs mat was measured under different CO2 concentrations. It was found that without the catalyst pretreatment, the sensitivity was about 4% when the CNTs mat was exposed to 800 mTorr CO2 concentration. However, with various catalyst pretreatment times of 5, 10, 15 and 20 min, the sensitivity was 3.69%, 6.27%, 9.54%, and 12.1%, respectively. The Raman spectroscopy showed the I-D/I-G decreased from 0.668 to 0.539 as the catalyst pretreatment time increased. The XPS also showed the correlation of surface chemical components with the Raman spectroscopy. The Fe catalyst H-2 plasma pretreatment affected both the graphitization and surface binding sites of CNTs. (C) 2007 Elsevier B.V. All rights reserved.

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