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801.
Shankara S. Kalanur Jaewoo Heo Il-Han Yoo Hyungtak Seo 《International Journal of Hydrogen Energy》2017,42(26):16901-16908
The ultrathin two-dimensional (2D) nanomaterials display unique properties owing to their ultrahigh specific surface area and strong quantum confinement of electrons in two dimensions. In this work, we fabricated a rapid gasochromic and electrical hydrogen sensing system containing 2D WO3 and Pd nanoparticles. 2D WO3 nano-plates (NP) are synthesized using sol–gel method and Pd nanoparticles are coated on WO3 by green photochemical deposition method. The sensor is fabricated by dispersing the 2D WO3/Pd composite on filter paper. In presence of hydrogen gas, 2D WO3/Pd composite produces visible change in color from brown to dark blue. With the fabricated sensor, as low as 0.1% H2 gas in air at room temperature can be easily detected using electrical sensing scheme whereas for higher concentration from 1 to 100%, eye readable gasochromic scheme can be utilized. The use of 2D WO3 decreased the response time in great deal compared to WO3 nanoparticles indicating the advantage of 2D structure in fabricating rapid response H2 sensors. The proposed method is simple and can be easily employed to large scale fabrication system for commercial applications. 相似文献
802.
Chuer Hyun Moon S.K. Singh Dong Gi Lee Soung Soo Yi Kiwan Jang Jung Hyun Jeong Jong-Seong Bae Dong-Soo Shin 《Ceramics International》2012
Alkaline earth metal gallets have been identified as an important ceramic material. The crystal chemistry of many of these gallets is well explored; however, very rare studies regarding optical properties of rare earth (RE) ions doped in such gallets, particularly in Sr3Ga2O6 host, have been carried out. The present study reports on synthesis and characterization of novel Sr3Ga2O6:Eu3+ phosphors. The phosphors have been synthesized using a conventional solid state reaction method. Crystal structure, morphology and luminescence properties (excitation, emission and CIE coordinate) of these phosphors have been studied as a function of sintering temperature and Eu3+ concentration. X-ray diffraction study reveals that the phosphor sintered at low temperature (900 °C) contains an impurity phase which is removed at higher sintering temperatures and results into cubic crystalline phase of Sr3Ga2O6. Particle size of the phosphor increases with an increase in sintering temperature which results to a red shift in the peak position of excitation band lying in a broad range from 250 to 370 nm. Optimum emission intensity is attained for 0.12 mol% concentration of Eu3+ ions; above this concentration, a quenching in emission intensity is observed. 相似文献
803.
Poly(vinylidene fluoride) (PVDF) membranes have been widely used in microfiltration and ultrafiltration because of their excellent chemical resistance and thermal properties. However, PVDF membranes have exhibited severe membrane fouling because of their hydrophobic properties. In this study, we investigated the antifouling properties of PVDF blended membranes. Antifouling PVDF blended membranes were prepared with a PVDF‐g‐poly(ethylene glycol) methyl ether methacrylate (POEM) graft copolymer. The PVDF‐g‐POEM graft copolymer was synthesized by the atom transfer radical polymerization (ATRP) method. The chemical structure and properties of the synthesized PVDF‐g‐POEM graft copolymer were determined by NMR, Fourier transform infrared spectroscopy, and gel permeation chromatography. To investigate the antifouling properties of the membranes, we prepared microfiltration membranes by using the phase‐inversion method, which uses various PVDF/PVDF‐g‐POEM concentrations in dope solutions. The pure water permeabilities were obtained at various pressures. The PVDF/PVDF‐g‐POEM blended membranes exhibited no irreversible fouling in the dead‐end filtration of foulants, including bovine serum albumin, sodium alginate, and Escherichia coli broth. However, the hydrophobic PVDF membrane exhibited severe fouling in comparison with the PVDF/PVDF‐g‐POEM blended membranes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
804.
Jin-Young Kim Min Jong Bae Shang Hyeun Park Taewon Jeong Sunjin Song Jeonghee Lee Intaek Han Ji Beom Yoo Donggeun Jung SeGi Yu 《Carbon》2012,50(1):170-174
Inorganic powder electroluminescence (IPEL) devices with the insertion of a carbon nanotube (CNT) layer were investigated to verify the effect of the increased local field produced by CNTs on electroluminescence (EL). To increase the field strength effectively, the CNTs were shortened using the cryogenic crushing method. IPEL devices with the insertion of a short CNT layer exhibited an increase in brightness and efficiency with increasing amount of CNTs. The local field enhancement by CNTs, further enlarged by the triple-junction, could increase the field strength applied to the phosphor, resulting in improved EL performance. In addition, short CNTs in an EL device can lead to field enhancement without an unintentional current flowing into the device. 相似文献
805.
Jeongah Lee Yeonsu Jung Junyoung Song Jun Suk Kim Geon-Woong Lee Hee Jin Jeong Youngjin Jeong 《Carbon》2012,50(10):3889-3896
We have created a field emitter composed of a carbon nanotube (CNT) yarn, which was prepared by direct spinning through chemical vapor deposition and then formed into a carpet structure by tying the yarn to a conductive substrate before cutting it. The structure of the carpet is arranged to induce the tips of the CNT yarn to protrude toward the anode for maximum electron emission. The turn-on field, threshold field, and field enhancement factor of the device are 0.33, 0.48 V/μm, and 19,141, respectively. Extremely low operating electric fields and a high field enhancement factor result from the high density of CNT emitters with high crystallinity, the electrically good contact between the emitters and the substrate, and the effects of the multistage structure. The emission is stable even at a high current density of 2.13 mA/cm2, attributed to the strong adhesion between the emitters and the substrate. The emission performance is found to be customizable by adjusting the structure, for example, the CNT pile density. These results are relevant for practical applications, such as large-area flat-panel displays, large-area low-voltage lamps, and X-ray sources. 相似文献
806.
Sunhwan Hwang Joongwon Lee Ung Gi Hong Ji Chul Jung Dong Jun Koh Hyojun Lim Changdae Byun In Kyu Song 《Journal of Industrial and Engineering Chemistry》2012,18(1):243-248
Mesoporous nickel(30 wt%)-M(10 wt%)-alumina xerogel (30Ni10MAX) catalysts with different second metal (M = Fe, Ni, Co, Ce, and La) were prepared by a single-step sol–gel method for use in the methane production from carbon monoxide and hydrogen. In the methanation reaction, yield for CH4 decreased in the order of 30Ni10FeAX > 30Ni10NiAX > 30Ni10CoAX > 30Ni10CeAX > 30Ni10LaAX. Experimental results revealed that CO dissociation energy of the catalyst and H2 adsorption ability of the catalyst played a key role in determining the catalytic performance of 30Ni10MAX catalyst in the methanation reaction. Optimal CO dissociation energy of the catalyst and large H2 adsorption ability of the catalyst were favorable for methane production. Among the catalysts tested, 30Ni10FeAX catalyst with the most optimal CO dissociation energy and the largest H2 adsorption ability exhibited the best catalytic performance in terms of conversion of CO and yield for CH4 in the methanation reaction. The enhanced catalytic performance of 30Ni10FeAX was also due to a formation of nickel–iron alloy and a facile reduction. 相似文献
807.
Two donor–acceptor-type alternating copolymers consisting of 2,1,3-benzoselenadiazole and carbazole derivatives with thiophene or selenophene π-bridges were synthesized by Suzuki cross-coupling polymerization, and their optical, electrochemical, and photovoltaic properties were compared. The selenophene π-bridged copolymer (PCz-DSeBSe) exhibited a smaller band-gap (1.82 eV) than the thiophene-bridged polymer (PCz-DTBSe; 1.89 eV). PCz-DSeBSe also showed a deeper highest occupied molecular orbital energy level (−5.36 eV) than PCz-DTBSe (−5.20 eV). Moreover, the PCz-DSeBSe thin film showed higher crystallinity and hole mobility than the PCz-DTBSe thin film. Organic photovoltaic devices were fabricated using the polymers as the donors and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as the acceptor. The device using PCz-DSeBSe showed a higher open circuit voltage (Voc), short circuit current density (Jsc), and power conversion efficiency (PCE) than that using PCz-DTBSe. The fabricated indium tin oxide/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/PCz-DSeBSe:PC71BM/LiF/Al device showed the maximum PCE of 2.88% with a Jsc of 7.87 mA/cm2, an Voc of 0.80 V, and a fill factor of 0.50 under AM 1.5G irradiation (100 mW/cm2). 相似文献
808.
Electrical properties and the role of inhomogeneities at the polyvinyl alcohol/n‐inp schottky barrier interface
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M. Siva Pratap Reddy Hee‐Sung Kang Jung‐Hee Lee V. Rajagopal Reddy Ja‐Soon Jang 《应用聚合物科学杂志》2014,131(2)
In this work, we have investigated the electrical properties of Au/n‐InP contacts with a thin layer of polyvinyl alcohol (PVA) as an interlayer. The current–voltage (I–V) and capacitance–voltage (C–V) measurements are carried out in the temperature range of 175–425 K. The Au/PVA/n‐InP Schottky structure show nonideal behaviors and indicates the presence of a nonuniform distribution of interface states. The temperature dependent interface states densities (NSS), ideality factor and barrier height are obtained. An abnormal decrease in zero‐bias barrier height (BH) and increase in the ideality factor ( ) with decreasing temperature have been explained on the basis of the thermionic emission theory with Gaussian distribution (GD) of the BHs due to the BH inhomogeneities. The experimental I–V characteristics of Au/PVA/n‐InP Schottky diode has revealed the existence of a double GD with mean BH values of ( ) of 1.246 and 0.899 eV and standard deviation ( ) of 0.176 and 0.137 V, respectively. Consequently, the modified conventional activation energy versus plot gives and Richardson constants ( ) and the values are 1.17 and 0.71 eV and 9.9 and 6.9 A/cm2 K2, respectively, without using the temperature coefficient of the BH. The effective Richardson constant value of 9.9 A/cm2 K2 is very close to the theoretical value of 9.4 A/cm2 K2 for n‐InP. The discrepancy between Schottky barrier heights estimated from I–V and C–V measurements is also discussed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39773. 相似文献
809.
Seon Mi Kong Rong Fan Sung Hee Jung Chee Won Chung 《Journal of Industrial and Engineering Chemistry》2013,19(4):1320-1324
Cu(In1?xGax)Se2 (CIGS) thin films were prepared using a single quaternary target by RF magnetron sputtering. The effects of deposition parameters on the structural, compositional and electrical properties of the films were examined in order to develop the deposition process without post-deposition selenization. From X-ray diffraction analysis, as the substrate temperature and Ar pressure increased and RF power decreased, the crystallinity of the films improved. The scanning electron microscopy revealed that the grains became uniform and circular shape with columnar structure with increasing the substrate temperature and Ar pressure, and decreasing the RF power. The carrier concentration of CIGS films deposited at the substrate temperature of 500 °C was 2.1 × 1017 cm?3 and the resistivity was 27 Ω cm. At the substrate temperature above 500 °C, In and Se contents in CIGS films decreased due to the evaporation and it led to the deterioration of crystallinity. It was confirmed that CIGS thin films deposited at optimal condition had similar atomic ratio to the target value even without post-deposition selenization process. 相似文献
810.
Hexagonal boron nitride (hBN) and aluminum oxinitride (AlON) composites were synthesized by combustion reaction of powder mixtures of Al–B2 O3 –AlN systems under a low pressure of nitrogen gas (0.5 MPa). Explosive combustion reaction of Al–B2 O3 systems under the same nitrogen pressure produced alumina, aluminum borate, AlN, and AlON depending on the binary mixing ratio, but no trace of BN phases could be identified. Most of the elemental boron product remained unreacted and amorphous. On the other hand, AlN addition as a diluent in the range of 15–30 wt% was effective in producing hBN phase and forming AlON–BN composites. In the composition range of the ternary mixture of Al, B2 O3 , and AlN, where significant BN formation was identified, the primary role of AlN was to react with B2 O3 to produce BN and α-Al2 O3 . The temperature profile obtained during the combustion reaction by a thermocouple imbedded in the middle of the powder bed revealed that the initial nitridation reaction of aluminum metal provides the heat required for the combustion reaction, creating a state of a "chemical oven." The reaction product, α-Al2 O3 , reacted subsequently with AlN to produce AlON phases to give final AlON–BN composites. The combustion reaction was highly unstable and followed a mixed mode with a regularly reversing spinning mode for aluminum nitridation reaction in the surface region and an oscillatory mode for the BN formation reaction in the subsurface region. 相似文献