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Carbon Nanotube Reinforced Metal Matrix Nanocomposites via Equal Channel Angular Pressing
Quang Pham,Jeong Young-Gi,Yoon Seung-Chae,Hong Sun-Ig,Hong Soon-Hyung,Kim Hyoung-Seop 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
In this study, bottom-up type powder processing and top-down type SPD (severe plastic deformation) approaches were combined in order to achieve full density of Carbon nanotube (CNT)/metal matrix composites with superior mechanical properties by improved particle bonding and least grain growth, which were considered as a bottle neck of the bottom-up method using the conventional powder metallurgy of compaction and sintering. ECAP (equal channel angular pressing), the most promising method in SPD, was used for the CNT/Cu powder consolidation. The powder ECAP processing with 1, 2, 4 and 8 route C passes was conducted at room temperature.
Carbon Nanotube Reinforced Metal Matrix Nanocomposites via Equal Channel Angular Pressing
Pham, Quang,Jeong, Young Gi,Yoon, Seung Chae,Hong, Sun Ig,Hong, Soon Hyung,Kim, Hyoung Seop Trans Tech Publications, Ltd. 2007 Materials science forum Vol.534 No.-
<P>Carbon nanotubes (CNTs) have been the subject of intensive study for applications in the fields of nanotechnologies in recent years due to their superior mechanical, electric, optical and electronic properties. Because of their exceptionally small diameters (≈ several nm) as well as their high Young’s modulus (≈ 1 TPa), tensile strength (≈ 200 GPa) and high elongation (10-30%) in addition to a high chemical stability, CNTs are attractive reinforcement materials for light weight and high strength metal matrix composites. In this study, bottom-up type powder processing and top-down type SPD (severe plastic deformation) approaches were combined in order to achieve full density of CNT/metal matrix composites with superior mechanical properties by improved particle bonding and least grain growth, which were considered as a bottle neck of the bottom-up method using the conventional powder metallurgy of compaction and sintering. ECAP (equal channel angular pressing), the most promising method in SPD, was used for the CNT/Cu powder consolidation. The powder ECAP processing with 1, 2, 4 and 8 route C passes was conducted at room temperature. It was found by mechanical testing of the consolidated CNT/Cu that high mechanical strength could be achieved effectively as a result of the Cu matrix strengthening and improved particle bonding during ECAP. The ECAP processing of powders is a viable method to achieve fully density CNT-Cu nanocomposites.</P>
Synthesis and Quality of Cr-doped AlN Thin Films Grown by RF Sputtering
Pham Hong Quang,Tran Quang Hung,Ngo Xuan Dai,Tran Hoai Thanh,Kim CheolGi 한국자기학회 2007 Journal of Magnetics Vol.12 No.4
The AlCrN films were grown by RF reactive sputtering method under the selected conditions. The Cr concentration was varied by the number of Cr pieces placed on the Al target. The sample quality has been studied by XRD, Auger spectroscopy, optical absorption and electrical resistant measurements. The XRD and Auger results show that the samples consist of a major phase with the Al1-xCrxN formula, which has a hexagonal structure, and a few percents at. of oxygen, which may form Al₂O₃. There exist the Cr clusters in the samples with high concentration of Cr. The optical absorption measurement provides the information about the band gap that relates strongly to the quality of samples. The quality of samples is also clearly reflected in electrical measurement, i.e., the temperature dependence of resistance exhibits a semiconductor characteristic only for the samples that have no Cr cluster. In these cases, the values of ionization energies Ea can be derived from R(T) plots by using the function R(T) = Ro exp (Ea/kBT).
Pham Hong Quang,유성초,Do Hong Minh,Huynh Thanh Nhan,Nguyen Huy Sinh 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.45 No.3
Substitution of Mn by Fe, Co, and Ni ions suppresses double exchange (DE), leading to a reduction in ferromagnetic interaction, or equivalently to lower values of Curie temperature, TC. The intensity of the electron paramagnetic resonance (EPR) line decreases exponentially with temperature, and the temperature dependence of EPR linewidth undergoes a minimum near TC. The activation energy values, Ea, derived from the temperature dependence of EPR line intensity, are equal to 0.074 eV, 0.093 eV and 0.086 eV for TM = Fe, Co, and Ni, respectively. In the case of cobalt substitution, an anomaly in the thermal evolution of the EPR linewidth has been observed. We attribute the cause of this anomaly to a Jahn-Teller transition or an electronic phase separation.
Effect of sulfamic acid as complexing agent on electrodeposition of CIGS absorber thin film
Pham Hong Quang 한양대학교 세라믹연구소 2012 Journal of Ceramic Processing Research Vol.13 No.S1
Cyclic voltamettry (CV) studies of unitary Cu, Ga, In and Se systems, binary Cu-Se system, and quaternary Cu-In-Ga-Se have been carried out in the solutions with different concentration of sulfamic acid to understand the role of this acid as a complexing agent. Cu(InGa)Se2 (CIGS) thin films were deposited on Mo/soda-lime glass substrates by electrodeposition in the same applied potential and the same electrotyle bath but different in concentration of sulfamic acid, from 0 mM to 40 mM. The composition of the films was determined by EDS. The crystalline structure and morphology of the films were characterized by XRD and SEM, respectively. The obtained results indicate that sulfamic acid with an appropriate concentration (about 20-30 mM) can inhibit the underpotential deposition of Cu-Se phases and the H+ reduction into H2 which are considered as the undesired process. On the other hand, sulfamic acid can promote the reduction of Ga3+, consequently can increase the Ga concentration. The desired Cu(In0.70Ga0.30)Se2 stoichiometry was obtained in the films grown from solution which contains 20-30 mM sulfamic acid.
Pham Hong Quang,유성조 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
Magnetic semiconductor Al0:87Mn0:13N thin films were synthesized by DC reactive sputtering at various temperature from 27 to 400℃. The film thickness is topically about 800 nm range. The resistance measured at the temperature range from 120 to 300 K.We present in this report the effect of the substrate temperature and the annealing process on the conductive property of the samples. In all investigated samples, the temperature dependence of the resistivity exhibit a semiconductor behavior, e.g., R exp(Ea=kBT). The values of the activation energy, Ea, obtained from the data ft of the resistance as a function of temperature, decrease with increasing substrate temperature. On the other hand it increase with increasing post-annealing temperature. These behaviors can be attributed to the change in the impurity band dependent on deposition and post-annealing temperature. Magnetic semiconductor Al0:87Mn0:13N thin films were synthesized by DC reactive sputtering at various temperature from 27 to 400℃. The film thickness is topically about 800 nm range. The resistance measured at the temperature range from 120 to 300 K.We present in this report the effect of the substrate temperature and the annealing process on the conductive property of the samples. In all investigated samples, the temperature dependence of the resistivity exhibit a semiconductor behavior, e.g., R exp(Ea=kBT). The values of the activation energy, Ea, obtained from the data ft of the resistance as a function of temperature, decrease with increasing substrate temperature. On the other hand it increase with increasing post-annealing temperature. These behaviors can be attributed to the change in the impurity band dependent on deposition and post-annealing temperature.
Pham, Duc-Quang,Kim, Nam,Kwon, Ki-Chul,Jung, Jae-Hyun,Hong, Keehoon,Lee, Byoungho,Park, Jae-Hyeung Optical Society of America 2010 Optics letters Vol.35 No.18
<P>In spite of their many advantages, limited image depth still remains as an obstacle to three-dimensional displays based on integral imaging. In this Letter, by combining multiple polymer-dispersed liquid-crystal films and a dual-depth configuration, we propose a method to enhance the depth range of the integral imaging display system.</P>
Coupled Analysis of Heat Transfer and Deformation in Equal Channel Angular Pressing of Al and Steel
Quang, Pham,Krishnaiah, A.,Hong, Sun Ig,Kim, Hyoung Seop The Japan Institute of Metals 2009 MATERIALS TRANSACTIONS Vol.50 No.1
<P>In the present paper, the heat transfer and plastic deformation during the equal channel angular pressing of Al alloy and steel were numerically analyzed. The finite element simulations were carried out at various pressing speeds ν=0.18, 1.8, and 18 mm/s, and the temperature and plastic strain distributions were investigated. It is concluded that the pressing speed is the most important processing parameter in rising temperature. Temperature rise in steel is higher than that in Al alloy due to the combined effect of high strength (heat generation effect) and low thermal diffusivity (heat release effect) in steel.</P>
Pham Hai Yen,Phan Van Kiem,Nguyen Xuan Nhiem,Nguyen Huu Tung,Tran Hong Quang,Chau Van Minh,김정우,최은미,김영호 대한약학회 2007 Archives of Pharmacal Research Vol.30 No.10
A new monoterpene glycoside, 6'-O-β-D-glucopyranosylalbiflorin (1), and four known compounds; albiflorin (2), 6'-O-benzoylalbiflorin (3), paeoniflorin (4) and benzoyl paeoniflorin (5), were isolated from the methanolic extract of the roots of Paeonia lactiflora Pall.. Their chemical structures were completely elucidated using a combination of 2D NMR techniques (COSY, HMQC and HMBC) and HRESI-MS analyses. To investigate the bioactivities of these compounds, their effects on the differentiation of osteoblastic MC3T3-E1 cells were tested. Compound 1 (0.01-10 µM) significantly increased the alkaline phosphatase activity and nodules mineralization of MC3T3-E1 cells compared to those of the control (P<0.05). These results suggest that newly isolated compound 1 has a direct stimulatory effect on bone formation in vitro and may contribute to the prevention for osteoporosis.