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61.
Ultra-thin polypyrrole nanosheets (UPNSs) are fabricated by organic crystal surface-induced polymerization (OCSP) of pyrrole in an aqueous suspension containing hydrated crystals of sodium decylsulfonate (C10SO3Na) below the Krafft temperature using FeCl3 as an oxidant. The hydrated C10SO3Na crystals are used as templates through electrostatic binding of the cationic polypyrrole (PPy) chains oxidized by Fe(III) ions on the anionic C10SO3Na crystal surface. The resulting UPNSs have a single layer thickness of ∼21 nm, widths between 2 and 6 μm, and lengths greater than 10 μm. The UPNSs are composed of a single continuous PPy domain. Moreover, the UPNSs exhibit higher conductivity (30.6 Scm−1) and longer conjugation lengths than the PPy nanoparticles (2.4 Scm−1) prepared using emulsion polymerization. We systematically investigate the UPNSs as gas sensors for detecting and quantifying toxic gases such as HCl and NH3. The UPNSs exhibit much higher gas sensitivity and faster response times compared with the PPy nanoparticles. 相似文献
62.
Ui-Su Im Jiyoung Kim Seon Ho Lee Byung-Rok Lee Dong-Hyun Peck Doo-Hwan Jung 《JOM Journal of the Minerals, Metals and Materials Society》2017,69(12):2460-2466
In the present study, surface texture features and chemical properties of two types of cokes, made from coal tar by either 1-stage heat treatment or 2-stage heat treatment, were researched. The relationship between surface texture characteristics and the chemical properties was identified through molecular weight distribution, insolubility of coal tar, weight loss with temperature increase, coking yield, and polarized light microscope analysis. Rapidly cleared anisotropy texture in cokes was observed in accordance with the coking temperature rise. Quinoline insolubility and toluene insolubility of coal tar increased with a corresponding increases in coking temperature. In particular, the cokes produced by the 2-stage heat treatment (2S-C) showed surface structure of needle cokes at a temperature approximately 50°C lower than the 1-stage heat treatment (1S-C). Additionally, the coking yield of 2S-C increased by approximately 14% in comparison with 1S-C. 相似文献
63.
Charge Transport: Nonfullerene Electron Transporting Material Based on Naphthalene Diimide Small Molecule for Highly Stable Perovskite Solar Cells with Efficiency Exceeding 20% (Adv. Funct. Mater. 20/2018) 下载免费PDF全文
64.
Young Suk Kim Sung Soo Kim Sang Chul Kwon Yong Moo Cheong Kyung Soo Im 《Metallurgical and Materials Transactions A》2002,33(3):919-925
The objectives of this study are to systematically investigate the delayed hydride cracking (DHC) velocity and the threshold-stress
intensity factor, K
IH
, of a Zr-2.5Nb pressure tube as a function of orientation and elucidate the cause of this anistropic DHC behavior. The DHC
velocity as a function of orientation was determined using flattened cantilever beam specimens with 60 ppm H while the threshold-stress
intensity factor K
IH
, was evaluated as a function of orientation on the curved compact-tension (CT) and cantilever-beam (CB) specimens charged
with hydrogen to 200 ppm H. To infer a difference in a stress gradient ahead of the crack tip as a function of orientation,
tensile tests were conducted at temperatures ranging from room temperature (RT) to 560 °C using small tensile specimens of
2-mm-gage length taken from three directions of the tube. A textural change was investigated by comparing the inverse pole
figures before and after DHC while the {10
7} pole figures were constructed to find out the growth pattern of the DHC crack as a function of orientation. Faster DHC
velocity and lower K
IH
were obtained over temperatures of 170 °C to 270 °C, when the DHC crack grew in the longitudinal direction of the Zr-2.5Nb
pressure tube. The strain hardening after yielding and the extent of the textural change accompanied by DHC were higher in
the longitudinal direction of the tube, suggesting a higher stress gradient ahead of the crack tip. Thus, the anisotropic
DHC behavior of a Zr-2.5Nb pressure tube is discussed based on the stress gradient ahead of the crack tip governed by strain-hardening
rate after yielding and a change in texture accompanied by DHC, and the distribution of the {10
7} hydride habit planes.
This article is based on a presentation made in the symposium entitled “Defect Properties and Mechanical Behavior of HCP Metals
and Alloys” at the TMS Annual Meeting, February 11–15, 2001, in New Orleans, Louisiana, under the auspices of the following
ASM committees: Materials Science Critical Technology Sector, Structural Materials Division, Electronic, Magnetic & Photonic
Materials Division, Chemistry & Physics of Materials Committee, Joint Nuclear Materials Committee, and Titanium Committee. 相似文献
65.
Dae Sung Yoon Yoon-Kyoung Cho Kwang W. Oh Sunhee Kim Young Ah Kim Jung Im Han Geunbae Lim 《Microsystem Technologies》2006,12(3):238-246
We have fabricated a microfluidic gel valve device that used reversible sol–gel transition of methyl cellulose (MC). A microheater
and a microtemperature sensor were implemented in each microchannel in the gel valve device. Before evaluating the performance
of the gel valve device, various properties of the MC solution were investigated using viscometer, spectrophotometer, and
NMR. Gelation temperature was increased as the MC concentration was increased. Clear gel, an intermediate state between clear
sol and turbid gel, was found at the temperature range from 30–40°C to 50–60°C. Temperature at each microchannel of the device
was measured and the effect of the temperature difference on the valve operation was elucidated. In order to have normal operation
of the gel valve, it was important to keep the temperature of the heated microchannel around 60°C while keeping the temperature
of the flowing microchannel below 35°C. The temperature difference between two microchannels was about 23 K when fan forced
cooling (FFC) method was used. For normal performance of the gel valve device, a temporary pause of fluid flow for at least
5 s was required to complete the local gelation in the microchannel. Stable gel valve performance was obtained at the flow
rates larger than 5 μl/min. The gel valve device showed no leakage up to 2.07×104 Pa. 相似文献
66.
The previously proposed conditions for cavity formation from equiaxed inclusions in ductile fracture have been examined. Critical local elastic energy conditions are found to be necessary but not sufficient for cavity formation. The interfacial strength must also be reached on part of the boundary. For inclusions larger than about 100Å the energy condition is always satisfied when the interfacial strength is reached and cavities form by a critical interfacial stress condition. For smaller cavities the stored elastic energy is insufficient to open up interfacial cavities spontaneously. Approximate continuum analyses for extreme idealizations of matrix behavior furnish relatively close limits for the interfacial stress concentration for strain hardening matrices flowing around rigid non-yielding equiaxed inclusions. Such analyses give that in pure shear loading the maximum interfacial stress is very nearly equal to the equivalent flow stress in tension for the given state of plastic strain. Previously proposed models based on a local dissipation of deformation incompatibilities by the punching of dislocation loops lead to rather similar results for interfacial stress concentration when local plastic relaxation is allowed inside the loops. At very small volume fractions of second phase the inclusions do not interact for very substantial amounts of plastic strain. In this regime the interfacial stress is independent of inclusion size. At larger volume fractions of second phase, inclusions begin to interact after moderate amounts of plastic strain, and the interfacial stress concentration becomes dependent on second phase volume fraction. Some of the many reported instances of inclusion size effect in cavity formation can thus be satisfactorily explained by variations of volume fraction of second phase from point to point. 相似文献
67.
Michael G. Kane Lawrence Goodman Arthur H. Firester Paul C. van der Wilt Alexander B. Limanov James S. Im 《Journal of the Society for Information Display》2007,15(7):471-478
Abstract— CMOS TFT circuits were fabricated on plastic using sequential laterally solidified silicon combined with a low‐temperature CMOS process. The unity‐gain frequencies of the best of NMOS TFTs are greater than 250 MHz, and the CMOS ring oscillators operate at 100 MHz. To the best of the authors' knowledge, these are the highest‐frequency circuits ever fabricated directly on plastic. This high‐performance CMOS‐on‐plastic process can be applied to the fabrication of AMLCD integrated drivers and AMOLED pixels on plastic substrates. 相似文献
68.
Binary discriminant functions are often used to identify changed area through time in remote sensing change detection studies. Traditionally, a single change-enhanced image has been used to optimize the binary discriminant function with a few (e.g., 5-10) discrete thresholds using a trial-and-error method. Im et al. [Im, J., Rhee, J., Jensen, J. R., & Hodgson, M. E. (2007). An automated binary change detection model using a calibration approach. Remote Sensing of Environment, 106, 89-105] developed an automated calibration model for optimizing the binary discriminant function by autonomously testing thousands of thresholds. However, the automated model may be time-consuming especially when multiple change-enhanced images are used as inputs together since the model is based on an exhaustive search technique. This paper describes the development of a computationally efficient search technique for identifying optimum threshold(s) in a remote sensing spectral search space. The new algorithm is based on “systematic searching.” Two additional heuristic optimization algorithms (i.e., hill climbing, simulated annealing) were examined for comparison. A case study using QuickBird and IKONOS satellite imagery was performed to evaluate the effectiveness of the proposed algorithm. The proposed systematic search technique reduced the processing time required to identify the optimum binary discriminate function without decreasing accuracy. The other two optimizing search algorithms also reduced the processing time but failed to detect a global maxima for some spectral features. 相似文献
69.
Hong Geun Im 《Journal of Mechanical Science and Technology》2000,14(1):103-112
Numerical simulations of unsteady opposed-flow flames are performed using an adaptive time integration method designed for differential-algebraic systems. The compressibility effect is considered in deriving the system of equations, such that the numerical difficulties associated with a high-index system are alleviated. The numerical method is implemented for systems with detailed chemical mechanisms and transport properties by utilizing the Chemkin software. Two test simulations are performeds hydrogen/air diffusion flames with an oscillatory strain rate and transient ignition of methane against heated air. Both results show that the rapid transient behavior is successfully captured by the numerical method. 相似文献
70.
To evaluate the transcrystalline effects caused by various fibers, which were untreated, or treated with sodium hydroxide and cellulase, isothermal crystallization was performed. It was observed that the untreated and cellulase-treated cellulose fibers (cellulose I) had a nucleating ability to transcrystallize at PP matrix. Especially, cellulose fibers treated with Sodium hydroxide (cellulose II) transcystallized at PP matrix. This result was different from other's. Cellulose fibers also transcrystallized at PP/MAH-PP matrix irrespective of the type of cellulose crystalline structure. In PP/MAH-PP/CELL system, MAH-PP was located around the fiber surface at initial crystallization time, but was gradually expelled from that with the increase of crystallization time, and existed at outer boundaries of transcrstalline region at the final crystallization time. These phenomena were confirmed by IR-IRS spectra. The tensile strength of PP/CELL and PP/MAH-PP/CELL composites decreased with the increase of isothermal crystallization time. Therefore, it is thought that transcrystallinity gives rise to negative effect of tensile strength. 相似文献