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Volume 1, Number 1, March 2012
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One-pot synthesis of gold trisoctahedra with high-index facets
Do Youb Kim, Kyeong Woo Choi, Sang Hyuk Im, O Ok Park, Xiao-Lan Zhong and Zhi-Yuan Li
Abstract;
Full Text (15391K)
Abstract
There have been many efforts on the generating metal nanocrystals enclosed by high-index facets for the use as highly active catalysts. This paper describes a facile synthesis of Au Trisoctahedra with high-index facets. In brief, the Au trisoctahdra were prepared by reduction of HAuCl4 in N,Ndimethylformamide (DMF) containing poly (vinyl pyrrolidone) (PVP) and trace amount of AgNO3. The Ag ions in the reaction solution played a critical role in controlling the trisoctahedral shape of the final product by underpotential deposition (UPD) on the Au surfaces. The as-prepared Au trisoctahedra were single crystal and enclosed by high-index {441}, {773} and {331} facets.
Key Words
gold; trisoctahedra; transformation; underpotential deposition; silver
Address
Do Youb Kim, Kyeong Woo Choi and O Ok Park: Department of Chemical and Biomolecular Engineering (BK21 graduate program), Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea.
O Ok Park: Department of Energy Systems Engineering, Daegu Gyeongbuk Institute of Science and Technology (DGIST), 50-1, Sang-ri, Hyeonpung-myeon, Dalseong-gun, Daegu 711-873, Republic of Korea.
Sang Hyuk Im: KRICT-EPFL Global Research Laboratory, Advanced Materials Division, Korea Research Institute of Chemical Technology (KRICT), 19 Sinseongno, Yuseong-gu, Daejeon 305-600, Republic of Korea.
Xiao-Lan Zhong and Zhi-Yuan Li: Institute of Physics, Chinese Academy of Science, P. O. Box 603, Beijing 100080, People
Abstract
In order to simultaneously enhance the strength and plasticity in nanostructured / ultrafinegrained alloys, a strategy of introducing multiple length scales into microstructure (or called bimodal composite microstructure) has been developed recently. This paper presents a brief overview of the alloy developement and the mechanical behavior of ultrafine-grained Ti-Fe-based alloys with different lengthscale phases, i.e., micrometer-sized primary phases (dendrites or eutectic) embedded in an ultrafinegrained eutectic matrix. These ultrafine-grained titanium bimodal composites could be directly obtained through a simple single-step solidification process. The as-prepared composites exhibit superior mechanical properties, including high strength of 2000-2700 MPa, large plasticity up to 15-20% and high specific strength. Plastic deformation of the ultrafine-grained titanium bimodal composites occurs through a combination of dislocation-based slip in the nano-/ultrafine scale matrix and constraint multiple shear banding around the micrometer-sized primary phase. The microstructural charactersitcs associated to the mechanical behaivor have been detailed discussed.
Key Words
titanium alloy; bimodal composite; multiple length scales; ultrafine-grained; mechanical behavior; microstructure
Address
School of Mechanical and Chemical Engineering, The University of Western Australia, 35 Stirling Highway, Crawley, Perth, WA 6009, Australia
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Dental arch wires with tooth-like color
Sinn-wen Chen, Hsin-jay Wu, Chih-hao Liu, Yuan-chun Chien and Chih-chang Hu
Abstract;
Full Text (3259K)
Abstract
Unique tooth-like (milky white) color
Key Words
orthodontic materials; surface properties; anodization; tooth color
Address
Department of Chemical Engineering, National Tsing Hua University, #101, Sec. 2, Kuang-Fu Road, Hsin-Chu 300, Taiwan
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Characterization of high performance CNT-based TSV for high-frequency RF applications
Sukeshwar Kannan, Bruce Kim, Anurag Gupta, Seok-Ho Noh and Li Li
Abstract;
Full Text (3094K)
Abstract
In this paper, we present modeling and characterization of CNT-based TSVs to be used in high-frequency RF applications. We have developed an integrated model of CNT-based TSVs by incorporating the quantum confinement effects of CNTs with the kinetic inductance phenomenon at high frequencies. Substrate parasitics have been appropriately modeled as a monolithic microwave capacitor with the resonant line technique using a two-polynomial equation. Different parametric variations in the model have been outlined as case studies. Furthermore, electrical performance and signal integrity analysis on different cases have been used to determine the optimized configuration for TSV-based CNTs for high frequency RF applications.
Key Words
TSV; CNT; modeling; signal integrity; high-frequency; RF applications
Address
Sukeshwar Kannan, Bruce Kim and Anurag Gupta: University of Alabama, Tuscaloosa, Alabama, 35487-0286 USA.
Seok-Ho Noh: Andong National University, South Korea.
Li Li: Cisco Systems, Inc., USA.
Abstract
A powder metallurgy-based rapid consolidation technique, Plasma Pressure Compaction (P2C
Key Words
intermetallics; grain size; rapid consolidation; titanium aluminide; powder metallurgy
Address
Composites Research Laboratory, Department of Aerospace Engineering, University of Maryland, College Park, MD 20742, USA
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Size control of Co-doped ZnO rods by changing the solvent
Jing Zhao, Xiaoqin Yan, Yang Lei, Yanguang Zhao, Yunhua Huang and Yue Zhang
Abstract;
Full Text (4715K)
Abstract
In this work, the Co-doped ZnO rods were prepared by the hydrothermal method. The size of these rods can be changed from micro-size to nano-size by using different solutions during the preparation. The results of transmission electron microscopy (TEM) and selected area electron diffraction (SAED) showed that the as-prepared nano-sized Co-doped rods have single-crystal structure. The polarized Raman experiments were presented on an individual micro-sized Co-doped ZnO rod in the X(YY) , X(ZY) and X(ZZ) configurations, the results of polarized Raman indicated that these rods are crystallized and their growth direction is parallel to c-axis.
Key Words
ZnO; Co-doping; hydrothermal method; transmission electron microscopy; polarized Raman
Address
Department of Materials Physics and Chemistry, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, 30 Xueyuan Road, Beijing 100083, China
Abstract
The effect of under-bump-metallization (UBM) on electromigration was investigated at temperatures ranging from 135oC to 165oC. The UBM structures were examined: 5-
Key Words
electromigration; solder joints
Address
Department of Materials Science and Engineering, National Chiao Tung University, Hsin-chu 30010, Taiwan, Republic of China
Abstract
Epoxy resin is widely used in high voltage apparatus as insulation. Fillers are often added to epoxy resin to enhance its mechanical, thermal and chemical properties. The addition of fillers can deteriorate electrical performance. With the new development in nanotechnology, it has been widely anticipated that the combination of nanoparticles with traditional resin systems may create nanocomposite materials with enhanced electrical, thermal and mechanical properties. In the present paper we have carried out a comparative study on dielectric properties, space charge and dielectric breakdown behavior of epoxy resin/nanocomposites with nano-fillers of SiO2 and Al2O3. The epoxy resin (LY556), commonly used in power apparatus was used to investigate the dielectric behavior of epoxy resin/nanocomposites with different filler concentrations. The epoxy resin/nanocomposite thin film samples were prepared and tests were carried out to measure their dielectric permittivity and tan delta value in a frequency range of 1 Hz - 1 MHz. The space charge behaviors were also observed by using the pulse electroacoustic (PEA) technique. In addition, traditional epoxy resin/microcomposites were also prepared and tested and the test results were compared with those obtained from epoxy resin/nanocomposites.
Key Words
nanocomposites; epoxy resin; nanofillers; dielectric properties; space charg; dielectric strength
Address
School of Electronics and Computer Science, University of Southampton, Southampton, United Kingdom
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Associate Editors
