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921.
Yong K. Park Ho K. Lee Nong M. Hwang Houk C. Kwon Jong C. Park Duk N. Yoon 《Journal of the American Ceramic Society》1988,71(6):297-C
Microstructures of Y-Ba-Cu-O superconductor were observed using a polarized microscope. Orthorhombic and tetragonal phases were easily distinguished by the optical etching with cross-polarized light. In the specimen cooled rapidly in oxygen, it was possible to see the path of oxygen diffusion by observing the variation of the twin concentration. At the boundary between transformed and untransformed materials, evidence for diffusion-driven transformation could be clearly seen. 相似文献
922.
Highly Efficient Overall Water Splitting Through Optimization of Preparation and Operation Conditions of Layered Perovskite Photocatalysts 总被引:1,自引:0,他引:1
Jindo Kim Dong Won Hwang Hyun Gyu Kim Sang Won Bae Jae Sung Lee Wei Li Se Hyuk Oh 《Topics in Catalysis》2005,35(3-4):295-303
The layered perovskite materials were found to give the high photocatalytic activity in water splitting reaction under UV
irradiation, where the electronic structure of perovskite slab constructing the layered structure (the total cation valency)
was the most crucial factor to the high photocatalytic activity. Both the excessive cation valency and the layered structure
were required for active photocatalysts, while the slab thickness of layered perovskites had an insignificant effect on water-splitting
activity. In order to identify key variables that affected photocatalytic activity and to optimize the performance of (110)
layered perovskite, La2Ti2O7 was modified by various methods. The optimum amount of loaded nickel had a great effect and the amount depended on the surface
area of the perovskite phase. When an alkaline-earth element such as Ba, Sr, and Ca was doped on La2Ti2O7, the photocatalytic activity was enhanced markedly. Introduction of an alkaline hydroxide into the reaction system as an
external additive enhanced the activity further showing extremely high quantum yields close to 50%. 相似文献
923.
Jae-Keun Lee Hee-Soo Shin Chan-Jung Park Chang-Geon Lee Jung-Eun Lee Young-Whan Kim 《Korean Journal of Chemical Engineering》2002,19(1):41-45
A laboratory-scale electrodewatering system, incorporating an electric field as an additional driving force to conventional
pressure dewatering, has been developed to decrease the water content of sludges generated in wastewater treatment. Consisting
of a piston-type filter press, a power supply and a data acquisition system, the electrodewatering system’s performance was
evaluated as a function of applied pressure, applied voltage, sludge type and filtration time. Experiments were carried out
using sewage sludges with the electric field up to 120 V/cm and pressure ranging from 98.1 to 392.4 kPa. Electrodewatering
involving a combination of electric field and pressure enhances both the dewatering rate and final dewatered volume. The final
water content of sewage sludges in the electrodewatering system can be reduced to 62 wt%, as compared to 78 wt% achieved with
the pressure filtration alone. The electrodewatering system shows the potential to be an effective method for reducing the
water content in sludges. 相似文献
924.
Towards an Environmentally Acceptable Heterogeneous Catalytic Method of Producing Adipic Acid by the Oxidation of Hydrocarbons in Air 总被引:1,自引:0,他引:1
Raja Robert Lee Sang-Ok Sanchez-Sanchez Manuel Sankar Gopinathan Harris Kenneth D.M. Johnson Brian F.G. Thomas John Meurig 《Topics in Catalysis》2002,20(1-4):85-88
A survey is given of the catalytic methods potentially available for the production of adipic acid by the oxidation of readily available hydrocarbon precursors under environmentally benign conditions. Encouraging results are reported using H2O2 as oxidant and microporous FeAlPO-5 as catalyst at moderate temperatures. 相似文献
925.
Poly(amide imide)–epoxysilane (coupling agent) composites were reacted with silica, a condensation product of tetraethylorthosilicate (TEOS), by a sol–gel process and were then cast into films. After this procedure, the chemical characteristics and mechanical and thermal properties were measured. Fourier transform infrared showed that silica existed in the poly(amide imide) matrix. When a proper amount of silica was added to the poly(amide imide) matrix, the tensile strength, elongation, and toughness increased greatly. A poly(amide imide)/30 wt % epoxysilane composite with 20 wt % TEOS had the best mechanical properties. Thermogravimetric analysis under nitrogen and oxygen atmospheres indicated that the char contents increased with the amount of silica. The glass‐transition temperatures of the poly(amide imide)–silica nanocomposites were observed around 170–180°C with differential scanning calorimetry. This approach may be a new method for the low‐temperature thermal curing of poly(amide imide). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1780–1788, 2004 相似文献
926.
Jun-Bin Ko Sung Wook Lee Dong Eun Kim Young Un Kim Gang Li Seung Goo Lee Tae-Sun Chang Dojin Kim Yong Lak Joo 《Journal of Porous Materials》2006,13(3):325-330
(1 − x)SiO2-(x)ZrO2 (x = 0.1, 0.2) composite fiber mats were prepared by electrospinning their sol-gel precursors of zirconium acetate and tetraethyl
orthosilicate (TEOS) without using a polymer binder. The electrospun composite fibers were characterized by powder X-ray diffraction
(XRD), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FT-IR) and mercury porosimetry. The composite
fibers having a tetragonal crystalline ZrO2 were obtained by calcining the electrospun composite fibers at high temperatures. The results show that the structure and
crystallization of ZrO2 in the composite fibers can be controlled by sintering temperature, while the porosity and morphology of the fiber mats did
not depend on the sintering temperature. 相似文献
927.
The polymers 3 having pyridine moieties in the main chain were synthesized by the reaction of the organocobalt polymers 1 having cobaltacyclopentadiene moieties in the main chain with various nitriles 2. When brown colored 1 and excess 2 were heated in tetrahydrofuran at 80 °C for 24 h and then at 150 °C for 12 h in a sealed tube, the polymers 3 were obtained by the precipitation with methanol in good yields. From the spectroscopic measurements, the resulting polymers
3 were found to contain 35 – 90% of the pyridine moieties depending on the structures of 1.
Received: 7 July 1997/Revised: 14 August 1997/Accepted: 25 August 1997 相似文献
928.
Soluble polypyrrole (PPy) samples advanced in electrical conductivity σ were chemically synthesized with dodecylbenzenesulfonate (DBS) sodium salt as a dopant, with poly(ethylene glycol) (PEG) as an additive, and with ammonium persulfate as an oxidant. The PPy–DBS–PEG samples were soluble in organic solvents (N‐methylpyrrolinone and m‐cresol). The greater the molar percentage ratio was of DBS, the greater the solubility was of synthesized PPy composites (PPy–DBS–PEG). The maximum electrical conductivity at room temperature for PPy–DBS–PEG was 1.02 S/cm, which was in fact the true conductivity of 100/10 (mol %) PPy/DBS. The chemical composition and doping level of PPy–DBS–PEG were determined by elemental analysis. The results of Fourier transform infrared spectroscopy were used for the structural characterization of PPy–DBS–PEG. The scanning electron microscopy results showed that the electrical conductivity was related to the morphology of PPy–DBS–PEG. According to thermogravimetric analysis, PPy–DBS–PEG was more thermostable than PPy–DBS. Electron spin resonance measurements showed that the polaron and bipolaron acted as charge carriers of PPy–DBS–PEG. According to the temperature dependence of the electrical conductivity, PPy–DBS–PEG was a semiconductor and followed the three‐dimensional variable‐range hopping model. The improved electrical conductivity apparently resulted from the reduction of the crosslinking and structural defects of the PPy chains. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1170–1175, 2005 相似文献
929.
Nanocomposites of iron oxide (Fe3O4) with a sulfonated polyaniline, poly(aniline‐co‐aminonaphthalenesulfonic acid) [SPAN(ANSA)], were synthesized through chemical oxidative copolymerization of aniline and 5‐amino‐2‐naphthalenesulfonic acid/1‐amino‐5‐naphthalenesulfonic acid in the presence of Fe3O4 nanoparticles. The nanocomposites [Fe3O4/SPAN(ANSA)‐NCs] were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X‐ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, elemental analysis, UV–visible spectroscopy, thermogravimetric analysis (TGA), superconductor quantum interference device (SQUID), and electrical conductivity measurements. The TEM images reveal that nanocrystalline Fe3O4 particles were homogeneously incorporated within the polymer matrix with the sizes in the range of 10–15 nm. XRD pattern reveals that pure Fe3O4 particles are having spinel structure, and nanocomposites are more crystalline in comparison to pristine polymers. Differential thermogravimetric (DTG) curves obtained through TGA informs that polymer chains in the composites have better thermal stability than that of the pristine copolymers. FTIR spectra provide information on the structure of the composites. The conductivity of the nanocomposites (~ 0.5 S cm?1) is higher than that of pristine PANI (~ 10?3 S cm?1). The charge transport behavior of the composites is explained through temperature difference of conductivity. The temperature dependence of conductivity fits with the quasi‐1D variable range hopping (quasi‐1D VRH) model. SQUID analysis reveals that the composites show ferromagnetic behavior at room temperature. The maximum saturation magnetization of the composite is 9.7 emu g?1. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 相似文献
930.
The presence of uncertainties in manufacturing systems and supply chains can cause undesirable behavior. Failure to account for these in the design phase can further impair the capability of systems to respond to changes effectively. In this work, we consider a dynamic workforce-inventory control problem wherein inventory planning, production releases, and workforce hiring decisions need to be made. The objective is to develop planning rules to achieve important requirements related to dynamic transient behavior when system parameters are imprecisely known. To this end, we propose a resilience optimization model for the problem and develop a novel local search procedure that combines the strengths of recent developments in robust optimization technology and small signal stability analysis of dynamic systems. A numerical case study of the problem demonstrates significant improvements of the proposed solution in controlling fluctuations and high variability found in the system’s inventory, work-in-process, and workforce levels. Overall, the proposed model is shown to be computationally efficient and effective in hedging against model uncertainties. 相似文献