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51.
Younggon Son Kalman B Migler 《Polymer》2002,43(10):3001-3006
This paper describes an improvement of the technique to measure interfacial tension in immiscible polymer blends. Our method is based on the droplet retraction method, in which one relates the kinetics of relaxation of a deformed droplet to the interfacial tension between the matrix and droplet. Previously, the problem with this technique has been the difficulty in preparing axisymmetric ellipsoidal droplets. In our work, we demonstrate that perfect axisymmetric ellipsoidal droplets are produced at a later stage of relaxation of short imbedded fibers. With this technique, we utilize the strengths of both the deformed droplet method and the imbedded fiber retraction method while overcoming their shortcomings. The interfacial tension value thus obtained was compared to that by conventional methods. Additionally, the effect of confinement by external walls on the interfacial tension measurement was studied. Confinement affects interfacial tension measurement when the gap between the walls is less than two times the equilibrium drop size. 相似文献
52.
Vinit D. Makwana L. Javier Garces Jia Liu Jun Cai Young-Chan Son Steven L. Suib 《Catalysis Today》2003,85(2-4):225-233
Manganese oxides having a tunnel structure (OMS-2) have been utilized as selective catalysts for alcohol oxidation. In this study manganese oxide catalysts were synthesized in different media and modified by exchanging the tunnel cation by H+, using acid treatment or exchanging with NH4+ followed by thermolysis. Various alcohol oxidations were performed using these catalysts to ascertain the influence of synthesis method on their activity. A correlation is made between lattice oxygen instability and activity of the catalysts, which indicates involvement of the lattice oxygen in the mechanism. The exchange of the tunnel cation with the smaller H+ ions leads to weakening of the Mn–O bond, as verified by temperature programmed desorption (TPD) results. Only the chemisorbed oxygen on the surface (O−) and the lattice oxygen in the layers close to the surface is involved in the oxygen transfer during the reaction. 相似文献
53.
Sang Hern Kim Won Keun Son Yong Joo Kim Eu‐Gene Kang Dong‐Won Kim Chang Woo Park Whan‐Gi Kim Hyung‐Joong Kim 《应用聚合物科学杂志》2003,88(3):595-601
A polystyrene (PS)/poly(butyl acrylate) (PBA) composite emulsion was produced by seeded emulsion polymerization of butyl acrylate (BA) with PS seed particles which were prepared by emulsifier‐free polymerization of styrene with potassium persulfate (KPS) under a nitrogen atmosphere at 70°C for 24 h with stirring at 60 rpm and swelled with the BA monomer in an ethanol/water medium. The structure of the PS/PBA composite particles was confirmed by the presence of the characteristic absorption band attributed to PS and PBA from FTIR spectra. The particles for pure PS and PS/PBA with a low content of the BA monomer were almost spherical and regular. As the BA monomer content was increased, the particle size of the PS/PBA composite particles became larger, and more golf ball‐like particles were produced. The surface morphology of the PS/PBA composite particles was investigated by AFM and SEM. The Tg's attributed to PS and PBA in the PS/PBA composite particles were found at 110 and ?49°C, respectively. The thermal degradation of the pure PS and PS/PBA composite particles occurred in one and two steps, respectively. With an increasing amount of PBA, the initial thermal decomposition temperature increased. On the contrary the residual weight at 450°C decreased with an increasing amount of PBA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 595–601, 2003 相似文献
54.
The effects of solution properties and polyelectrolyte on the electrospinning of poly(ethylene oxide) (PEO) solutions were investigated. Ultrafine PEO fibers without beads were electrospun from 3, 4, 7 and 7 wt% PEO solutions in chloroform, ethanol, (dimethylformamide) DMF and water, respectively. At these concentrations, the values of [η]C were ∼10 for all solutions. The average diameters of PEO fibers were ranged from 0.36 to 1.96 μm. The higher the dielectric constant of solvent was, the thinner PEO fiber was. The average diameters of electrospun PEO fibers from PEO/water solutions were decreased and their distributions were narrowed by adding 0.1 wt% poly(allylamine hydrochloride) (PAH) and poly(acrylic acid sodium salt) (PAA) due to the increased charge density in solutions. The addition of PAH and PAA lowered the minimum concentration for electrospinning of a PEO/water solution to 6 wt%. 相似文献
55.
Won Seok Lyoo Hyun Seok Lee Byung Chul Ji Sung Soo Han Kang Koo Sam Soo Kim Joon Ho Kim Joon‐Seok Lee Tae Won Son Won Sik Yoon 《应用聚合物科学杂志》2001,81(14):3471-3480
Melt‐spun poly(trimethylene terephthalate) (PTT) fibers were zone‐drawn and the structures and properties of the fibers were investigated in consideration of the spinning and zone‐drawing conditions. The draw ratio increased up to 4 with increasing drawing temperature to 180°C, at a maximum drawing stress of 220 MPa. Higher take‐up velocity gave lower drawability of the fiber. The PTT fiber taken up at 4000 rpm was hardly drawn, in spite of using maximum drawing stress, because a high degree of orientation had been achieved in the spinning procedure. However, an additional enhancement of birefringence was observed, indicating a further orientation of PTT molecules by zone drawing. The exotherm peak at 60°C disappeared and was shifted to a lower temperature with an increase in the take‐up velocity, which means that the orientation and crystallinity of the fiber increased. The d‐spacing of (002) plane increased with increasing take‐up velocity and draw ratio, whereas those of (010) and (001) planes decreased. In all cases, the crystal size increased with take‐up velocity and draw ratio. The cold‐drawn PTT fiber revealed a kink band structure, which disappeared as the drawing temperature was raised. The physical properties of zone‐drawn PTT fibers were improved as the draw ratio and take‐up velocity increased. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3471–3480, 2001 相似文献
56.
Strength improvement and purification of Yb2Si2O7‐SiC nanocomposites by surface oxidation treatment 下载免费PDF全文
Son T. Nguyen Tadachika Nakayama Hisayuki Suematsu Tsuneo Suzuki Lingfeng He Hong‐Baek Cho Koichi Niihara 《Journal of the American Ceramic Society》2017,100(7):3122-3131
A two‐step processing was developed to prepare Yb2Si2O7‐SiC nanocomposites. Yb2Si2O7‐Yb2SiO5‐SiC composites were first fabricated by a solid‐state reaction/hot‐pressing method. The composites were then annealed at 1250°C in air for 2 hours to activate the oxidation of SiC, which effectively transformed the Yb2SiO5 into Yb2Si2O7. The surface cracks purposely induced can be fully healed during the oxidation treatment. The treated composites have improved flexural strength compared to their pristine composites. The mechanism for crack healing and silicate transformation have been proposed and discussed in detail. 相似文献
57.
Comparative study of Al2O3, HfO2, and HfAlOx for improved self‐compliance bipolar resistive switching 下载免费PDF全文
Andrey S. Sokolov Seok Ki Son Donghwan Lim Hoon Hee Han Yu‐Rim Jeon Jae Ho Lee Changhwan Choi 《Journal of the American Ceramic Society》2017,100(12):5638-5648
The comparison of resistive switching (RS) storage in the same device architecture is explored for atomic layer deposition (ALD) Al2O3, HfO2 and HfAlOx‐based resistive random access memory (ReRAM) devices. Among them, the deeper high‐ and low‐ resistance states, more uniform VSET‐VRES, persistent ROFF/RON (>102) ratio and endurance up to 105 cycles during both DC and AC measurements were observed for HfAlOx‐based device. This improved behavior is attributed to the intermixing of amorphous Al2O3/HfO2 oxide layers to form amorphous thermally stable HfAlOx thin films by consecutive‐cycled ALD. In addition, the higher oxygen content at Ti/HfAlOx thin films interface was found within the energy dispersive spectroscopy analysis (EDS). We believe this higher oxygen content at the interface could lead to its sufficient storage and supply, leading to the stable filament reduction‐oxidation operation. Further given insight to the RS mechanism, SET/RESET power necessities and scavenging effect shed a light to the enhancement of HfAlOx‐based ReRAM device as well. 相似文献
58.
Seok Joo Park Ho Kyung Choi Young Ok Park Jae Ek Son 《Aerosol science and technology》2013,47(9):685-693
A shroud tube was used to decrease the amount of particles toward the bag filters from whole particles entering a filter vessel. The effects of the shroud tube on the flow field and particle behavior inside the vessel were studied. The air mixed with dust particles enters the vessel through a tangential inlet duct. Some of the particles are deposited on the inside wall of the vessel and the surface of the shroud tube. The other ones are collected on the filter surface or passed through it. The particles deposited on the wall surfaces fall into a hopper by gravity, and those collected on filters are removed by back pulse-jet flow. Computational simulation was performed to know the prereduction rate of particles by deposition on the wall surfaces for the different shroud tubes. The experiment was accomplished with some shroud tubes suggested by the results of computational simulation, and the experimental results were compared qualitatively with the computational results. The shroud tube blocked the direct transport of particles toward the bag filters and reduced the particle loading onto the filters. The particle loading was reduced when the upper region of the vessel was not blocked by the shroud tube more than when the vessel was blocked wholly with the filters from the upper end wall. However, the re-entrainment of the particles removed from the filters by the back pulse cleaning increased when the upper region of the vessel was not blocked by the shroud tube more than when the vessel was blocked wholly with the filters from the upper end wall. 相似文献
59.
Van Son Nguyen Laurent Badie Emmanuel Lamouroux Brice Vincent Fabrice Domingues Dos Santos Maëlen Aufray Yves Fort Didier Rouxel 《应用聚合物科学杂志》2013,129(1):391-396
Piezoelectric films were prepared by incorporation of lithium niobate (LiNbO3) nanoparticles into copolymer of vinylidene difluoride and trifluoroethylene. Nanoparticles of LiNbO3 with ferroelectric phase were successfully synthesized and dispersed homogenously by ultrasonication in the copolymer matrix without any surfactant or surface functionalization. The nanocomposites were fully characterized by electronic microscopy, X‐ray diffraction, differential scanning calorimetry, dynamical mechanical analysis, and piezometer. Surprisingly, the copolymer matrix crystallinity and morphology were not affected by the incorporation of nanoparticles. Therefore the nanocomposites remained good mechanicals properties and high ferroelectricity coupled to nonlinear optical activity thanks to the noncentro symmetric space group of lithium niobate. This could be a novel approach to develop new multifunctional materials. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
60.
Young‐Min Cho Hyung‐Jae Lee Yun Heo Shin‐Hye Park Si‐Yoong Seo Jae‐Hong Han Tae‐Il Son 《应用聚合物科学杂志》2013,129(4):2161-2170
Carboxymethyl starch was modified by the incorporation of an azidophenyl group to prepare photoreactive starch, and characterized by Fourier transform infrared reflectance (FT‐IR), proton nuclear magnetic resonance (1H‐NMR), and ultraviolet (UV) spectroscopy. Photo‐irradiation immobilized the Az‐starch on a polystyrene plate and it was stably retained on the surface. The protein containing immobilized Az‐starch was also immobilized on a stripe micropatterned plate. UV irradiation time and Az‐starch concentration were used to alter the physical properties of Az‐starch and consequently control the rate of epidermal growth factor (EGF) release. The Az‐starch that released growth factor was not cytotoxic to 3T3‐L1 fibroblast cells, and the immobilized EGF maintained its activity and induced cellular proliferation in vitro. These results suggest that Az‐starch could be useful as a clinical synthetic material for medical applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献