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Kim J.H.,Sungkyunkwan University | Eum M.,Electro-Mat | Kim T.H.,Electro-Mat | Lee J.Y.,Sungkyunkwan University
Dyes and Pigments | Year: 2017

A novel pyrrolocarbazole moiety was developed as a new donor moiety of thermally activated delayed fluorescent emitters. The new pyrrolocarbazole donor moiety possessed stronger donor strength than carbazole and better stability than acridine, which enhanced the quantum efficiency and lifetime of the thermally activated delayed fluorescent emitters. The pyrrolocarbazole donor, diphenyltriazine acceptor, and a phenyl linker merged emitter performed as a highly efficient delayed fluorescent emitter by providing high quantum efficiency of 17.7%. © 2016 Elsevier Ltd


Chen Y.-T.,National Central University | Lee S.-L.,National Central University | Bor H.-Y.,Electro-Mat | Lin J.-C.,National Central University
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2013

This research investigates the effects of natural aging and cold working prior to artificial aging on microstructures and mechanical properties of Al-4.6Cu-0.5Mg-0.5Ag alloy. Mechanical properties relative to microstructure variations were elucidated by the observations of the optical microscope (OM), differential scanning calorimeter (DSC), electrical conductivity meter (pct IACS), and transmission electron microscopy (TEM). The results showed that natural aging treatment has little noticeable benefit on the quantity of precipitation strengthening phases and mechanical properties, but it increases the precipitation strengthening rate at the initial stage of artificial aging. Cold working brings more lattice defects which suppress Al-Cu (GP zone) and Mg-Ag clustering, and therefore the precipitation of Ω phase decreases. Furthermore, more dislocations are formed, leading to precipitate the more heterogeneous nucleation of θ′ phase. The above-mentioned precipitation phenomena and strain hardening effect are more obvious with higher degrees of cold working. © 2013 The Minerals, Metals & Materials Society and ASM International.


Kim Y.K.,Korea Aerospace University | Park I.S.,Electro-Mat | Choi J.,Korea Aerospace University
Microelectronics Reliability | Year: 2010

The objective of this study is to analyze a warpage development mechanism by simulating a strip type packaging for plastic ball grid array. Molding compound and substrate materials were thermo-mechanically tested to obtain the mechanical properties by several test methods. Samples were fabricated using the same materials, and warpage developments were measured at room temperature after molding compound cure. Based on the tested materials property, the warpage developments were simulated by numerical calculations during cooldown process. The results were compared with the measurement data of the samples, and the warpage mechanism was investigated based on the elastic and viscoelastic simulation results. It was found that the relaxation behaviors of the molding compound and the substrate materials had significant effect on the warpage development. It was also found that the warpage development was dependent on the packaging geometry. The development mechanism was analyzed through the simulation calculations by combining different material properties modeling and geometries, and the results showed comprehensive consideration of the materials and the packaging design are essential to control the warpage. © 2010 Elsevier Ltd. All rights reserved.


Lee J.W.,Electro-Mat | Kim J.,Electro-Mat
Journal of Nanoscience and Nanotechnology | Year: 2012

Recently published experimental results indicate that current extreme ultra-violet lithography (EUVL) patterning process seems to be very hard to meet the device manufacturing specification goals, such as resolution, line-width roughness, and sensitivity (RLS) simultaneously. To overcome trade-off limitations between RLS performances of resist, we have approached the problem in several ways. Regarding materials, to make a uniform resist film we applied living radical polymerization and purification to obtain evenly interacting polymer chains. To obtain perfectly miscible resist components, such as polymer, photo acid generator (PAG) and quencher, we have optimized their structures to have similar polarity range. Acid diffusivity factors are also controlled by the resist components properties, including polymer T g and photo-acid polarity. In EUVL process, we applied surfactant rinse process to reduce line-width roughness and pattern collapse. In this paper, we discuss the performance of our EUV according to our material development concepts, that is, resist film homogeneity and acid diffusion control in order to meet the device manufacturing specification goals, such as resolution, line-width roughness (LWR), and sensitivity. © 2012 American Scientific Publishers.


Kuo W.-K.,Electro-Mat | Kuo G.-F.,Electro-Mat | Lin S.-Y.,Electro-Mat | Yu H.H.,Electro-Mat
Bioinspiration & biomimetics | Year: 2015

Polystyrene (PS) microspheres are synthesized by dispersion polymerization, and a close-packed two-dimensional (2D) array of the PS microspheres is formed by the self-assembly method through dip drawing under magnetic stirring. This array is then used to fabricate a 2D polydimethylsiloxane concave mold by soft lithography. The mold is employed to produce convex polymethylmethacrylate-based compound eye-replicating films of different hemispherical heights by thermopressing. The optical properties of the ommatidia on these biomimetic compound eye-replicating films are investigated, and the films are used with a charge-coupled device camera to construct a biomimetic visual system. The visual distance and field of view of this system are measured. The film with the greatest hemispherical height results in the biomimetic visual system with the highest visual distance and the widest field of view. In addition, it is found that the quality of the optical images is not dependent on the hemispherical height of the biomimetic films. The ability of the biomimetic visual system to detect moving object in real time is also studied.


Rao K.S.,Electro-Mat | Anand S.,Electro-Mat | Venkateswarlu P.,Andhra University
Clean - Soil, Air, Water | Year: 2011

The present investigation evaluates the adsorption effectiveness of Cd(II) ions on Ficus religiosa leaf powder (FRL). The experimental parameters chosen included time, pH, particle size, temperature, adsorbate, anion, and Pb(II) concentrations. The time data followed pseudo-second-order kinetics. Cd(II) adsorption increased from 1.38 to 75.17% with the increase in pH from 2 to 4 and further increase in pH to 5.5 resulted in its marginal increase to 77.52%. Based on regression coefficient values, the isothermic data fitted the various models in the order Langmuir>Redlich-Peterson>Temkin>Freundlich model. The maximum loading capacity of FRL was estimated to be 27.14mgg -1. The presence of Cl -, ${\rm SO}-{{\rm 4}}̂{2{-} } $, or Pb 2+ exhibited adverse effect on Cd(II) uptake. The thermodynamic parameters of enthalpy (ΔH 0) and entropy (ΔS 0) were estimated to be 8.31kJmol -1 and 38.22Jmol -1K -1, respectively. SEM-EPMA of the loaded FRL showed Cd(II) distribution at specific sites. The XRD patterns of Cd(II) loaded FRL sample showed disappearance of some peaks corresponding to β-Ca(PO 3) 2; shifting of peaks and decrease in %RI corresponding to γ-CaSO 4 phase. Positive shift of IR bands for the Cd(II) loaded sample was observed. FTIR spectra of Ficus religiosa leaf powder before and after cadmium absorption show shifts of various bands to higher wave numbers (3 to 43cm -1). © 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim.


Moghimi N.,University of Waterloo | Abdellah M.,University of Waterloo | Thomas J.P.,University of Waterloo | Mohapatra M.,Electro-Mat | Leung K.T.,University of Waterloo
Journal of the American Chemical Society | Year: 2013

Concave nanostructures are rare because of their thermodynamically unfavorable shapes. We prepared bimetallic FeNi concave nanocubes with high Miller index planes through controlled triggering of the different growth kinetics of Fe and Ni. Taking advantage of the higher activity of the high-index planes, we then fabricated monodispersed concave nanocages via a material-independent electroleaching process. With the high-index facets exposed, these concave nanocubes and nanocages are 10- and 100-fold more active, respectively, toward electrodetection of 4-aminophenol than cuboctahedrons, providing a label-free sensing approach for monitoring toxins in water and pharmaceutical wastes. © 2013 American Chemical Society.


Thiruvasagam P.,SASTRA University | Vijayan M.,Electro-Mat
High Performance Polymers | Year: 2012

Two new diacid monomers 4,4′-bis[5-(trimellitimido)napthyloxy] diphenyl sulfone and 4,4′-bis[5-(trimellitimido)napthyloxy]benzophenone were synthesized and characterized by spectroscopic analysis. A series of poly(amide-imide)s (PAIs) were prepared from these diacids and aromatic diamines through phosphorylation reaction. The structures of the PAIs were characterized by infrared and 1H-NMR. The PAIs were characterized by X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, electrical properties, solution viscosity and solubility test. The flexible linkages and pendant groups in the PAIs chain will disturb chain-chain packing and their effects on solubility, thermal stability and electrical properties were investigated. PAIs showed excellent thermal stability and good solubility. The dielectric constants of the PAIs were in the range 4.15-4.77. The PAIs have electrical insulation character and the film can be used in insulation of electrical items operating at elevated temperatures. © The Author(s) 2012.


Kalem S.,TUBITAK - Marmara Research Center | Arthursson O.,Chalmers University of Technology | Romandic I.,Electro-Mat
Thin Solid Films | Year: 2010

The surface of a single crystal Germanium wafer was transformed to fluoride and oxide crystals upon exposure to a vapor of HF and HNO3 chemical mixture. Ellipsometry, X-ray, SEM and photoluminescence were used to investigate the physical properties of the resultant surface structure. The analysis indicates that the transformation results in a polycrystalline hexagonal ammonium fluogermanates and a hexagonal α-Germanium oxide clusters with a preferential crystal growth orientation in <101> direction. The fluogermanates grow particularly around the germanium oxide clusters as evidenced by electron dispersive spectroscopy profiling. Local vibrational mode analysis confirm the presence of N-H and Ge-F vibrational modes of NH4+ and GeF6- ions. The vibrational modes at around 840 cm- 1 is significative of GeOx stretching bands originating from the partial coverage surface oxide formed together with the fluogermanates and clusters on the Germanium. Electronic band structure as probed by ellipsometry is typical of Ge and any discrepancy was associated with disorder induced band tailing effects originating possibly from the effect of oxide clustering. © 2009 Elsevier B.V. All rights reserved.


Grant
Agency: National Science Foundation | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 149.05K | Year: 2011

This Small Business Innovation Research Phase I project proposes to develop and commercialize new types of silicon nanowire anodes which may be used to safely store large amounts of lithium for many types of lithium batteries. The key innovation involves unique functionalization and integration methods that enable nanowire anodes to be cycled reversibly for thousands of cycles without mechanical failure, agglomeration, or deleterious side reactions. Silicon nanowires will be fabricated via electroless etching, and chemically or electrochemically functionalized to improve their performance and capacity retention in a lithium-ion battery. The objective of this work is to develop novel silicon composite anodes that may undergo over 200 deep cycles with capacities of at least 1000 mA.hg-1. The broader impact/commercial potential of this project is to develop high capacity anode rechargeable lithium batteries with capacities of over 1000 mA.hg-1, which represents approximate doubling of cell capacity without a significant change in manufacturing or cost. There is a critical need for high energy density rechargeable batteries for next generation hybrid vehicles and fully electric vehicles. In a recent report, the U.S. Department of Energy pointed out that the primary obstacles to the widespread introduction of lithium-based batteries for electric vehicles are the relatively low specific energy and the relatively high cost per kWh. The proposed integration and surface engineering methods will address these problems allowing the safe storage of lithium in silicon anodes for current and future generations of lithium batteries.

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