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91.
Dae‐Hyeon Kim Mi‐Ri Joung In‐Tae Seo Joon Hur Jong‐Hyun Kim Bo‐Yun Kim Hwack‐Joo Lee Sahn Nahm 《Journal of the American Ceramic Society》2014,97(12):3897-3903
Dielectric and piezoelectric properties of CuO‐added KNbO3 (KN) ceramics were investigated. The CuO reacted with the Nb2O5, formed a CuO–Nb2O5‐related liquid phase during the sintering, and assisted the densification of the KN ceramics at low temperatures. Moreover, some of the Cu2+ ions replaced the Nb5+ ions in the matrix and behaved as a hardener. The dielectric and piezoelectric properties of the KN ceramics were considerably influenced by the relative density. The 1.0 mol% CuO‐added KN ceramic sintered at 960°C for 1.0 h, which showed a maximum relative density, exhibited a high phase angle of 86.9°, Pr of 14.8 μC/cm2, and Ec of 1.8 kV/mm. This specimen also exhibited good dielectric and piezoelectric properties: εT33/εo of 364, d33 of 122 pC/N, kp of 0.29, and Qm of 611. 相似文献
92.
A Mo/TiN composite powder has been synthesized by a sol–gel method to improve the electrical performance and microstructural stability of the alkali metal thermal to electric converter electrode. The core (TiN)–shell (Mo) structure of the composite powder is confirmed by energy-dispersive X-ray spectroscopy and scanning electron microscopy. The composite powder is primarily composed of submicron (400–800 nm) particles that are coated on a core (>3–5 μm) particle. The Mo/TiN composite electrode exhibits high electrical conductivities of 1000 Scm−1 at 300 °C and 260 Scm−1 at 700 °C in an Ar atmosphere. The electrode exhibits excellent tolerance against grain growth during thermal cycling tests (R.T.↔800 °C), where the average growth rate of Mo grains in the Mo/TiN composite electrodes is controlled less than 0.5%/time (0.62→0.65 μm), while the growth rate in Mo electrodes is 306.7%/time (0.24→3.92 μm). It can be concluded that the Mo/TiN composite powder will suppress the degradation of the electrode and enhance the performance and durability of the unit cell at elevated temperatures. 相似文献
93.
Simple preparation of ordered mesoporous carbons assisted by an organosilicate as a linking material
Wooyoung Kim Nam Dong Kim Mi Yeong Kang Ji Bong Joo In Kyu Song Jung Rag Yoon Jongheop Yi 《Carbon》2010,48(15):4566-4569
Ordered mesoporous carbon materials (OMCs) were prepared from a silica–carbon composite assisted by 3-mercaptopropyltrimethoxysilane (MPTMS) in an aqueous phase. The obtained OMCs have a high surface area, large pore volume and uniform pore structure. MPTMS plays an important role in linking the polymer part with silica part to form a mesoporous structure. Importantly, the amount of MPTMS used is an important determinant in the development of a uniform mesoporosity. The method described herein has some important advantages over existing methods, such as simplified synthesis steps for the preparation of OMCs, the fact that the aqueous phase can be used and that the resulting materials have a high surface area of more than 1700 m2/g. 相似文献
94.
The effects of particle size of starting materials and amount of a BaTiO3 additive on the shrinkage behavior and elemental diffusion in Ni-based internal electrodes have been investigated in order to control the shrinkage of the internal electrode in multilayer ceramic capacitors (MLCCs). Two kinds of Ni and BaTiO3 powders were used with different particle sizes. Volume shrinkage over the range of 700–1300 °C at 150 °C intervals and linear shrinkage during sintering were measured for starting materials and composites in a reducing atmosphere. The interfaces of Ni/BaTiO3 composites with 90:10 and 70:30 volume ratios, respectively, were investigated using TEM. Composites with bimodal Ni powder show less shrinkage than those with monomodal Ni powder, showing less shrinkage in monolith Ni of bimodal particle size. The shrinkage behavior is changed during sintering with increasing amounts of BaTiO3 additives in both Ni-based composites. The particle size of the BaTiO3 additive affects the shrinkage behavior of composites, without the additional amount affecting the final shrinkage. A reaction layer of about 300 nm wide is observed at the interface between the Ni and BaTiO3 powders in composites, in which elemental Ni diffuses into the BaTiO3 without counterdiffusion. 相似文献
95.
Dae Hyun Kim Jung Shik Kang Yun Joo Lee Nam Kuk Park Young Chul Kim Suk In Hong Dong Ju Moon 《Catalysis Today》2008,136(3-4):228
Steam reforming of n-hexadecane, a main constituent of diesel, over noble metal-modified Ni-based hydrotalcite catalyst was carried out in a temperature range of 700–950 °C, at an atmospheric pressure with space velocity of 10,000–100,000 h−1 and feed molar ratio of H2O/C = 3.0. The catalysts were prepared by a co-precipitation and dipping methods. The noble metal-modified Ni-based hydrotalcite catalyst displayed higher resistance for the sintering of active metal than the Ni-based hydrotalcite catalyst prepared by the conventional method. It was found that the Rh-modified Ni-based catalysts showed high resistance to the formation of carbon compared to Ni-based catalysts. The results suggest that Rh-modified Ni-based catalyst can be applied for the steam reforming (SR) reaction of diesel. 相似文献
96.
Hem Raj Pant Bishweshwar Pant Han Joo Kim Altangerel Amarjargal Chan Hee Park Leonard D. Tijing Eun Kyo Kim Cheol Sang Kim 《Ceramics International》2013,39(5):5083-5091
In this study, Ag–ZnO/reduced graphene oxide (Ag–ZnO/RGO) composite was synthesized by a green and facile one-step hydrothermal process. Aqueous suspension containing Ag and ZnO precursors with graphene oxide (GO) sheets was heated at 140 °C for 2 h. The morphology and structure of as-synthesized particles were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, and Photoluminescence (PL) spectroscopy which revealed the formation of composite of metal, metal oxide and RGO. It was observed that the presence of Ag precursor and GO sheets in the hydrothermal solution could sufficiently decrease the size of ZnO flowers. The hybrid nanostructure, with unique morphology, obtained from this convenient method (low temperature, less time, and less number of reagents) was found to have good photocatalytic and antibacterial activity. The perfect recovery of catalyst after reaction and its unchanged efficiency for cyclic use showed that it will be an economically and environmentally friendly photocatalyst. 相似文献
97.
Hoo Kun Lee Myeong Soo Jeong Joo Wan Park Hyun Soo Park Jong Hyun Cho 《Korean Journal of Chemical Engineering》1990,7(1):13-17
An absorption efficiency of packed column removing nitrogen oxides with water and NaOH solution under atmospheric pressure
was studied. The efficiency and the acidity produced by absorption of NO, were measured in a packed column. The model developed
that was based on the mass-transfer information for packed column and absorption mechanism accompanying the chemical reaction
was compared with experimental results. Predictions using the model presented by the previous paper (part 1) was shown well
to agree with from the experimental results (part II). The efficiency of NOx, absorption is largely dependent on the height of packing material and the partial pressure of NOx in the feed gas. The efficiency of NOx absorption decreases with the increase of the acidity produced by recycling of water as a scrubber liquid. For the recycle
mode with an aqueous NaOH solution as a scrubber liquid, NOx absorption efficiency is shown to be constant until all of the COH- in the scrubber liquid are converted into CH+. 相似文献
98.
Selvaraj?Rengaraj Younghun?Kim Cheol?Kyun?Joo Kyunghee?Choi Jongheop?YiEmail author 《Korean Journal of Chemical Engineering》2004,21(1):187-194
The removal of copper from aqueous solution by ion exchange resins, such as 1200H and IRN97H, is described. Effect of initial
metal ion concentration, agitation time and pH on adsorption capacities of ion exchange resins was investigated in a batch
mode. The adsorption process, which is pH dependent, shows maximum removal of copper in the pH range 2–7 for an initial copper
concentration of 10 mg/L. The experimental data have been analyzed by using the Freundlich, Langmuir, Redlich-Peterson, Temkin
and Dubinin-Radushkevich isotherm models. The batch sorption kinetics have been tested for a first-order, pseudo-first order
and pseudo-second order kinetic reaction models. The rate constants of adsorption for all these kinetic models have been calculated.
Results showed that the intraparticle diffusion and initial sorption into resins of Cu(II) in the ion exchange resins was
the main rate limiting step. The uptake of copper by the ion exchange resins was reversible and thus has good potential for
the removal/recovery of copper from aqueous solutions. We conclude that such ion exchange resins can be used for the efficient
removal of copper from water and wastewater.
This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University. 相似文献
99.
100.
The mechanical and electrical properties were investigated for nanocomposites based on carbon nanotubes (CNTs) and conductive carbon black (CB). Solution room‐temperature‐vulcanized silicone rubber was used as a matrix. Vulcanizates based on CNTs and CB was prepared by solution mixing. With the addition of 2 phr of CNTs to the rubber matrix, the Young's modulus increased by 272% and reached as high as ~706% at 8 phr, whereas the modulus increased only 125% for CB specimens at 10 phr. Similarly, the electrical properties at 5 phr content of CNT were ~0.7 kΩ against ~0.9 kΩ at 20 phr CB. The Kraus plot from equilibrium swelling tests shows that the high properties for CNT specimens are due to high polymer–filler interfacial interactions, the small particle size that improves the distribution of the filler in a highly exfoliated state, and high electrical connective networks among the filler particles. These improvements can especially influence medical products such as feeding tubes, seals and gaskets, catheters, respiratory masks and artificial muscles. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44407. 相似文献