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RISS 인기검색어
- 검색키워드
- 저자 : Phan Hong Khoi (검색결과 9 건)
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New Technique for the Synthesis of Carbon Nanotubes
Phan Ngoc Minh,Phan Hong Khoi,Nguyen Van Chuc,Phan Ngoc Hong,Ngo Thi Thanh Tam 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5
Carbon nanotubes (CNTs) are considered as a promising material for various applications. However, due to their limited availability and high purchasing costs, at the present time, only a few of these applications have been realized. The realization of CNT-based devices and CNT-based materials depends on success in material synthesis and on the possibility of controlling the nanotube's chirality, diameter and purity. This paper describes new simple techniques for (i) synthesis of vertically-aligned carbon nanotubes (VA-CNTs), (ii) mass and low-cost production of multiwall carbon nanotubes (MWCNTs) and (iii) growth of individual CNTs on tungsten tips.
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Fabrication of Carbon Nanotubes on Tungsten Tips
Phan Ngoc Hong,Phan Ngoc Minh,Vo Viet Cuong,Bui Hung Thang,Phan Hong Khoi 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
In this paper, we present the results of fabrication of carbon nanotubes on sharp W tips for advanced electron emiters and scanning probe microscopy. A calculation to optimize the elec- trochemical etching conditions for geting ultra-sharp W tips was caried out. W tips of 50 nm in diameter were formed by electrochemical etching of a 0.3-mm W wire in a 5 % KOH solution. Fe catalytic nanoparticles were deposited at the apex of the W tip by electroplating in a FeCl3 solution. By using hot-lament chemical vapor deposition in C2H2/H2 gases, we have sucesfuly grown individual CNTs of 4 m in length and 20 nm in diameter on a W tip.
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Synthesis of Carbon Nanotubes on Steel Foils
Nguyen Van Chuc,Nguyen Duc Dung,Phan Ngoc Hong,Le Dinh Quang,Phan Hong Khoi,Phan Ngoc Minh 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
Carbon nanotubes (CNTs) were synthesized by using a thermal chemical vapor deposition (CVD) at 800 ℃ in a mixture of C₂H₂, H₂ and N₂ gases with steel foils as both catalysts and substrates. More than 2 grams of CNTs were grown on approximately 7 grams of steel foil with a 0.5 cm² surface area after 30 minutes of growth. The effects of CVD parameters, such as the growth temperature and the deposition time, on the size and the morphology of the CNTs were studied using scanning electron microscopy (SEM). We found that the optimized temperature and growth time for having high quality CNTs were 800 ℃ and 30 minutes, respectively. The purity of the CNTs was evaluated by using thermogravimetric analysis (TGA) and the result showed that the carbon content was approximately 93 wt.%. The graphite crystallinity of the CNTs was analyzed by using Raman spectroscopy. The steel foil was found to maintain its catalytic behavior after several growths. The technique holds great promise for use in mass production (approximately 120 grams CNTs per day) with signicantly reduced cost. Carbon nanotubes (CNTs) were synthesized by using a thermal chemical vapor deposition (CVD) at 800 ℃ in a mixture of C₂H₂, H₂ and N₂ gases with steel foils as both catalysts and substrates. More than 2 grams of CNTs were grown on approximately 7 grams of steel foil with a 0.5 cm² surface area after 30 minutes of growth. The effects of CVD parameters, such as the growth temperature and the deposition time, on the size and the morphology of the CNTs were studied using scanning electron microscopy (SEM). We found that the optimized temperature and growth time for having high quality CNTs were 800 ℃ and 30 minutes, respectively. The purity of the CNTs was evaluated by using thermogravimetric analysis (TGA) and the result showed that the carbon content was approximately 93 wt.%. The graphite crystallinity of the CNTs was analyzed by using Raman spectroscopy. The steel foil was found to maintain its catalytic behavior after several growths. The technique holds great promise for use in mass production (approximately 120 grams CNTs per day) with signicantly reduced cost.
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Analyzing the Purity of Carbon Nanotubes by Using Different Methods
Ngo Thi Thanh Tam,Nguyen Xuan Nghia,Nguyen The Quynh,Phan Hong Khoi,Phan Ngoc Minh 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
The purity of carbon nanotubes (CNTs) was evaluated by using a variety of methods: X-ray diraction, Raman spectroscopy, thermogravimetric analysis and energy dispersive X-ray uores- cence spectroscopy. X-ray diffraction, Raman spectroscopy and thermogravimetric analysis were used for a qualitative evaluation of impurities and energy dispersive X-ray uorescence spectroscopy was utilized for a quantitative determination. All experimental results evaluating the purity ob- tained from these techniques are consistent with each other for CNT samples with different degrees of purity. The purity of the CNT samples was found to be greatly increased when they were annealed in air or in vacuum. The contributions of Si-related, crystalline carbon, non-crystalline carbon and Fe and Ni components are discussed. The purity of carbon nanotubes (CNTs) was evaluated by using a variety of methods: X-ray diraction, Raman spectroscopy, thermogravimetric analysis and energy dispersive X-ray uores- cence spectroscopy. X-ray diffraction, Raman spectroscopy and thermogravimetric analysis were used for a qualitative evaluation of impurities and energy dispersive X-ray uorescence spectroscopy was utilized for a quantitative determination. All experimental results evaluating the purity ob- tained from these techniques are consistent with each other for CNT samples with different degrees of purity. The purity of the CNT samples was found to be greatly increased when they were annealed in air or in vacuum. The contributions of Si-related, crystalline carbon, non-crystalline carbon and Fe and Ni components are discussed.
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Carbon-Nanotube Growth over Iron Nanoparticles Formed on CaCO3 Support by Using Hydrogen Reduction
Nguyen Duc Dung,Nguyen Van Chuc,Ngo Thi Thanh Tam,Nguyen Hong Quang,Phan Hong Khoi,Phan Ngoc Minh 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
Carbon nanotubes (CNTs) were grown by chemical vapor deposition on a mixture of iron salt and CaCO3. Salt mixtures of Fe(NO₃)₃9H₂O/CaCO₃ and FeCl₃6H₂O/CaCO₃ with various Fe weight contents were used as catalysts for growing the CNTs. A scanning electron microscope study revealed that the CNTs were densely grown on the Fe(NO₃)₃9H₂O/CaCO₃ catalyst containing 5 wt.% Fe. The effect of growth temperature on the segregation of Fe nanoparticles formed by hydrogen reduction is discussed. The result shows that 800 ℃ is the optimal temperature for the formation of Fe nanoparticles over which CNTs grow with the highest yield of 78.61 %. A raman spectroscope and a scanning transmission electron microscope were utilized to characterize the multiwall structure of the CNTs. The 92.16 % purity of the CNTs was determined by using thermal gravimetric analysis. Carbon nanotubes (CNTs) were grown by chemical vapor deposition on a mixture of iron salt and CaCO3. Salt mixtures of Fe(NO₃)₃9H₂O/CaCO₃ and FeCl₃6H₂O/CaCO₃ with various Fe weight contents were used as catalysts for growing the CNTs. A scanning electron microscope study revealed that the CNTs were densely grown on the Fe(NO₃)₃9H₂O/CaCO₃ catalyst containing 5 wt.% Fe. The effect of growth temperature on the segregation of Fe nanoparticles formed by hydrogen reduction is discussed. The result shows that 800 ℃ is the optimal temperature for the formation of Fe nanoparticles over which CNTs grow with the highest yield of 78.61 %. A raman spectroscope and a scanning transmission electron microscope were utilized to characterize the multiwall structure of the CNTs. The 92.16 % purity of the CNTs was determined by using thermal gravimetric analysis.
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Bui Hung Thang,Pham Van Trinh,Le Dinh Quang,Nguyen Thi Huong,Phan Hong Khoi,Phan Ngoc Minh 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.3
Carbon nanotubes (CNTs) are some of the most valuable materials with high thermal conductivity. The thermal conductivity of individual multiwalled carbon nanotubes (MWCNTs) grown byusing chemical vapor deposition is 600 ± 100 Wm−1K−1 compared with the thermal conductivity419 Wm−1K−1 of Ag. Carbon-nanotube-based liquids – a new class of nanomaterials, have shownmany interesting properties and distinctive features offering potential in heat dissipation applicationsfor electronic devices, such as computer microprocessor, high power LED, etc. In this work,a multiwalled carbon-nanotube-based liquid was made of well-dispersed hydroxyl-functional multiwalledcarbon nanotubes (MWCNT-OH) in ethylene glycol (EG)/distilled water (DW) solutionsby using Tween-80 surfactant and an ultrasonication method. The concentration of MWCNT-OHin EG/DW solutions ranged from 0.1 to 1.2 gram/liter. The dispersion of the MWCNT-OH-basedEG/DW solutions was evaluated by using a Zeta-Sizer analyzer. The MWCNT-OH-based EG/DWsolutions were used as coolants in the liquid cooling system for the Intel Core i5 processor. Thethermal dissipation efficiency and the thermal response of the system were evaluated by directlymeasuring the temperature of the micro-processor using the Core Temp software and the temperaturesensors built inside the micro-processor. The results confirmed the advantages of CNTs inthermal dissipation systems for computer processors and other high-power electronic devices.
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Excitation of Resistive States in Superconducting Films by Using Electrical and Light Pulses
Jean-Paul Maneval,Fran cois-Ren e Ladan,J.C. Villegier,Vu Dinh Lam,Phan Hong Khoi 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
The resistance induced by nanosecond pulses of electric currrent or of light has been studied in superconducting Nb and NbN thin lms. Narrow bridges exhibit the features expected from quasi-1D transport, namely, localized phase-slip centers (PSC) and hot spots (HS), depending upon the prescribed conditions of temperature and applied current. PSC and HS are clearly identied from their characteristic delay and their evolution in time. We then analyze the response to combined pulsed illumination and current. Using very thin (4 nm) niobium-nitride lms, it was possible to detect the visible light delivered photon by photon. The resistance induced by nanosecond pulses of electric currrent or of light has been studied in superconducting Nb and NbN thin lms. Narrow bridges exhibit the features expected from quasi-1D transport, namely, localized phase-slip centers (PSC) and hot spots (HS), depending upon the prescribed conditions of temperature and applied current. PSC and HS are clearly identied from their characteristic delay and their evolution in time. We then analyze the response to combined pulsed illumination and current. Using very thin (4 nm) niobium-nitride lms, it was possible to detect the visible light delivered photon by photon.
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