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971.
We used in situ reactive compatibilization to investigate the interfacial reinforcement between polypropylene (PP) and nylon 6 (Ny6). A certain amount of maleic anhydride grafted polypropylene (MAPP) was pre-blended with pure PP to form in situ a copolymer with Ny6. The fracture toughness was measured using an asymmetric double cantilever beam test (ADCB). An analysis of the locus of failure revealed that at constant bonding temperature, the fracture toughness between PP and Ny6 was influenced not only by the bonding temperature but also by the bonding time. The fracture toughness increased with the bonding temperature until 220 °C, and then decreased at higher bonding temperatures, which could be explained by the progressive occurrence of two different failure mechanisms, first adhesive failure at the interface and later cohesive failure between chains. X-ray diffraction measurements on specimens prepared at bonding temperatures of 210, 220, and 230 °C revealed no identifiably different crystalline PP phases. The fracture toughness increased with the annealing time, passed a peak, and then reached a plateau. The dependence of the fracture toughness on the bonding time could also be explained in terms of the two fracture mechanisms. X-ray photoelectron spectroscopy (XPS) results corroborated these explanations. 相似文献
972.
Joongwon Lee Seik Park Haikyung Seo Miyeong Kim Simoon Kim Junhwa Chi Kitae Kim 《Korean Journal of Chemical Engineering》2012,29(5):574-582
The integrated gasification combined cycle (IGCC) system is well known for its high efficiency compared with that of other coal fueled power generating systems. In this study, gasification using different types of burners with different oxygen supply angles in a bench-scale entrained flow gasifier was investigated. The effects of the oxygen gas supply angle of the coal burner and resulting oxygen supply location in the gasifier on the syngas composition and temperature of the gasifier were experimentally examined. These changes had a significant influence on the syngas composition of the final stream, carbon conversion, and efficiencies. According to the experimental results, the models using the Aspen Plus process simulator were positioned to define the effects of the experimental parameters and to find the optimum operating conditions in the bench gasifier facility. 相似文献
973.
Sun Uk Lee Kwonsu Jung Gwon Woo Park Charles Seo Yeon Ki Hong Won Hi Hong Ho Nam Chang 《Korean Journal of Chemical Engineering》2012,29(7):831-850
This review deals with a recent development of biofuels and chemicals from biomass. Some of the grainbased biofuels and chemicals have already been in commercial operation, including fuel ethanol, biodiesel, 1.3-propanediol, polylactic acid (PLA) and polyhydroxy butyric acid/alkanoates (PHB/PHA). The next generation bioproducts will be based on lignocellulosics due to their abundance and to stabilize rising food prices. However, the technologies of handling biomass are yet in their infancy and suffer from low yield, low product titer, and low productivity. This review focuses on bioprocessing technologies for biofuels production: organic raw biomaterials available in Korea; volatile fatty acids platform, multi-stage continuous high cell density culture (MSC-HCDC), enrichment of fermentation broth by forward osmosis; various purification methods of pervaporation of ethanol, solvent extraction on succinic, lactic acids and reactive separation methods. 相似文献
974.
Sung-Hyun Yun Jung-Je Woo Seok-Jun Seo Tae-Hyun Yang Seung-Hyeon Moon 《Korean Journal of Chemical Engineering》2012,29(9):1158-1162
A simple electrochemical approach is presented to quantitatively predict activation energy and mass transfer coefficient from a polarization curve of polymer electrolyte fuel cells to examine the membrane-electrode assembly (MEA) performance. It is assumed that the initial voltage drop at open circuit voltage is due to kinetic activation energy and that the current loss at short circuit current is due to mass transfer resistance. Accordingly, voltage drop in the activation polarization is converted into a change in the Gibbs free energy to determine the activation energy requirement. The mass transfer coefficient for current losses is derived from Fick??s law, based on the mass transfer limitation of oxygen at the oxygen reduction reaction sites. Case studies from the literature show reasonable correlations to the operating conditions, thereby providing a useful tool for prediction of the preliminary values of the activation energy and mass transfer coefficient for an MEA under various conditions. 相似文献
975.
Yanlin Huang Longqing Mi Jie Qin Shala Bi Hyo Jin Seo 《Journal of the American Ceramic Society》2019,102(6):3555-3566
This work reports on the preparation, structure, photochemical, and magnetic properties of six-layered Aurivillius bismuth ferrititanates, that is, Bi7Ti3Fe3O21, Bi7(Ti2Nb)Fe3O21+δ, and Bi7(Ti2Mg)Fe3O21−δ nanoparticles. The samples were prepared through the modified citrate complexation and precursor film process. The XRD Rietveld refinements were conducted to study the phase formations and crystal structure. The morphological and chemical component characteristics were investigated using SEM, TEM, and EDX analyses. Bi7Ti3Fe3O21, Bi7(Ti2Nb)Fe3O21+δ, and Bi7(Ti2Mg)Fe3O21−δ nanoparticles present an indirect allowed transitions with band energies of 2.04, 2.03, and 2.02 eV, respectively. The hybridized (O2p+Fet2g+Bi6s) formed the valence band (VB) and electronic components of (Ti–3d+Fe–eg) formed the conduction band (CB) of this six-layered Aurivillius bismuth ferrititanate. The three samples showed efficient photocatalytic degradation of Rhodamine B (RhB) dyes with the excitation wavelength λ > 420 nm. The optical absorption, photodegradation, and magnetic abilities were improved through microstructural modification on “B” site via partial substitution of Mg2+ and Nb5+ for Ti4+. The photocatalytic results were discussed based on the layer structure and multivalent Fe ions. Fe3+/2+ in the perovskite slabs (Bi5Fe3Ti3O19)2− could act as the catalytic mediators in the photocatalysis process. As a photocatalyst, Aurivillius Bi7(Ti2Mg)Fe3O21−δ nanoparticle is advantageous due to its photocatalytic and magnetically recoverable abilities. 相似文献
976.
Sebastian Steiner In-Tae Seo Pengrong Ren Ming Li David J. Keeble Till Frömling 《Journal of the American Ceramic Society》2019,102(9):5295-5304
Na1/2Bi1/2TiO3 (NBT) based ceramics are amongst the most promising lead-free ferroelectric materials. It was expected that the defect chemistry and the effect of doping of NBT would be similar to that observed for lead based materials, however, acceptor doping does not lead to ferroelectric hardening. Instead, high oxygen ionic conductivity is induced. Nevertheless, for solid solutions with BaTiO3 (BT), which are more relevant with respect to ferroelectric applications, such a drastic change of electrical properties has not been observed so far. To rationalize the difference in defect chemistry between NBT and its solid solution 94(Na1/2Bi1/2TiO3)–0.06 BaTiO3 (NBT–6BT) compositions with different concentrations of Fe-dopant were investigated. The study illustrates that the materials exhibit very similar behavior to NBT, and extraordinarily high oxygen ionic conductivity could also be induced in NBT–6BT. The key difference between NBT–6BT and NBT is the range of the dependence of ionic conductivity with dopant concentration. Previous studies of NBT–6BT have not reached sufficiently high dopant concentrations to observe high conductivity. In consequence, the same defect chemical model can be applied to both NBT and its solid solutions. This will help to rationalize the effect of doping on ferroelectric properties of NBT-ceramics and defect chemistry related degradation and fatigue. 相似文献
977.
Kyung-Chul Shin Min-Ju Seo Jeong-Hun Ju Deok-Kun Oh 《Journal of the American Oil Chemists' Society》2019,96(6):663-669
Recombinant Escherichia coli expressing T879A variant 6,8-linoleate diol synthase (LDS) from Penicillium oxalicum showed 2.1-fold higher activity than recombinant E. coli expressing wild-type 6,8-LDS for the production of 6,8-dihydroxy fatty acids (DiHFA) from linoleic acid. The optimal conditions for the production of 6,8-DiHFA by recombinant E. coli expressing T879A variant 6,8-LDS were pH 6.5, 35°C, 50 g L−1 cells, 10 g L−1 (35.7 mM) substrate, and 5% (v/v) dimethyl sulfoxide. Under these optimized conditions, 6.6 g L−1 (22.1 mM) 6,8-dihydroxy-9,12(Z,Z)-octadecadienoic acid (DiHODE) and 7.1 g L−1 (22.6 mM) 6,8-dihydroxy-9(Z)-octadecenoic acid (DiHOME) were produced from linoleic acid and oleic acid in 40 min, respectively. The volumetric productivities of 6,8-DiHODE and 6,8-DiHOME under these conditions were 9.9 and 10.7 mg L−1 h−1, respectively. The volumetric productivities of 6,8-DiHODE and 6,8-DiHOME were the highest values among those of all reported regiospecific DiHODE and DiHOME, respectively. To the best of our knowledge, this is the first quantitative biotechnological production of 6,8-DiHFA. 相似文献
978.
New six main-chain polyesters containing bent-core mesogens with various central units (Ar = 1,2- or 1,3-phenylene and 1,6-, 1,7-, 2,3- or 2,7-naphthylene) were synthesized. All of the polymers were soluble in a mixture of phenol/p-chlorophenol/TCE (25/40/35 w/w/w). The inherent viscosities were in the range of 0.18–0.38 dL/g. Despite the existence of bent-core mesogens eliciting a remarkable diminution of molecular packing, polymer with Ar = 2,7-naphthylene formed a smectic phase, and polymers with both Ar = 1,2-phenylene and 2,3-naphthylene formed nematic phases. Moreover, most of the polymers were distinctly semi-crystalline. Herein, we report our findings regarding the first detection of cybotactic groups from the nematic phases of main-chain polyesters with bent-core mesogens. 相似文献
979.
Seung‐Deok Seo Duk‐Hee Lee Hyun‐Woo Shim Sungjun Lee Dong‐Wan Kim 《Journal of the American Ceramic Society》2014,97(5):1413-1420
We demonstrate a facile synthesis of monodisperse magnetite (Fe3O4) nanoparticles (NPs) via a simple wet chemical route at 180°C using oleylamine (C18H37N), which serves as a solvent, ligand, and surfactant. The particles have a narrow size distribution centered at about 10 nm. To provide better electron conductivity and structural stability, the as‐synthesized particles are given a carbon nanocoating by pyrolysis of the residual surfactant on their surface. This pyrolysis forms a uniform thin nanocoating on each particle, and a core/shell Fe3O4/carbon NP network was thus obtained. The core/shell Fe3O4/carbon electrode shows better reversible capacity, cycle life, and rate capability than a bare Fe3O4 NP electrode because of its efficient electron transport and stress relaxation provided by the thin carbon layer. 相似文献
980.
Jiyoung Seo Sunil Kim Yurian Kim Fauzia lqbal Hyungsun Kim 《Journal of the American Ceramic Society》2014,97(9):2789-2793
Light‐emitting‐diode (LED) encapsulants, such as epoxy and silicone resin, have a lower refractive index than YAG:Ce phosphor, and this is usually one of the major causes of LED inefficiency. To improve LED performance, a glass encapsulant is considered. In this study, the SiO2–B2O3–ZnO glass system containing La2O3 and WO3 was investigated as an encapsulant to minimize total internal reflection and to increase the light extraction efficiency of LED packages. The characterization of glass encapsulants was performed using a differential scanning calorimeter, a pycnometer, a prism coupler, X‐ray photoelectron spectroscopy, and integrating spheres. The refractive index increased linearly with increasing molar volume of glass because La2O3 and WO3 act as modifiers in the glass, creating more nonbridging oxygen. The refractive index of glass increases with the content of La2O3 and WO3, which is attributed to the increase in polarizability of oxide ions in the glass. When the refractive index between glass and phosphor matched, light extraction efficiency was maximized because total internal reflection decreased. 相似文献