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91.
A new synthesis procedure for titanium-containing aluminosilicate zeolites has been obtained using a clear colloidal dispersion (sol) which was prepared with titanium isopropoxide, water, hydrochloric acid and colloidal silica, Ludox. When NaY, KL, offretite, mordenite and ZSM-5 zeolites were crystallized from the sol following conventional hydrothermal crystallization procedures, all the aluminosilicate zeolites showed the same X-ray absorption fine structure at the Ti K edge indicating framework Ti. The zeolites showed remarkable catalytic activity for the partial oxidation of cyclohexene using H2O2 as an oxidant and the photocatalytic decomposition of trichloroethene using water. 相似文献
92.
Nanopore Sensing in Aqueous Two‐Phase System: Simultaneous Enhancement of Signal and Translocation Time via Conformal Coating 下载免费PDF全文
Sang Jun Lee Ji Yoon Kang Wonjoon Choi Rhokyun Kwak 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(3)
Nanofluidic resistive pulse sensing (RPS) has been extensively used to measure the size, concentration, and surface charge of nanoparticles in electrically conducting solutions. Although various methods have been explored for improving detection performances, intrinsic problems including the extremely low particle‐to‐pore volume ratio (<0.01%) and fast nanoparticle translocation (10–1000 µs) still induce difficulties in detection, such as low signal magnitudes and short translocation times. Herein, we present an aqueous two‐phase system (ATPS) in a nanofluidic RPS for amplifying translocation signals and decreasing translocation speeds simultaneously. Two immiscible aqueous liquids build a liquid‐liquid interface inside nanopores. As particles translocate from a high‐affinity liquid phase into a lower‐affinity one, the high‐affinity liquid forms a conformal coating on the particles, which increases the effective particle size and amplifies the current‐blockage signal. The translocation time is also increased, as the ATPS interface impedes the particle translocation. For 20 nm particles, 7.92‐fold and 5.82‐fold enhancements of signal magnitude and translocation time can be achieved. To our knowledge, this is the first attempt to improve nanofluidic RPS by treating an interface of solution reservoirs for manipulating target particles rather than nanopores. This direct particle manipulation allows us to solve the two intrinsic problems all at once. 相似文献
93.
The dependence of the maximum and minimum wet thicknesses on the coating gap is derived for the slot-die coating process, under different slot-die configurations. Analytical expressions for the wet thickness and its derivative with respect to the coating gap are obtained using a simple flow model. The results indicate that, as expected, the minimum wet thickness increases linearly with the coating gap; however, the maximum wet thickness demonstrates a counterintuitive trend of decreasing as the coating gap increases, when a specific slot-die configuration is assumed. Moreover, the results are also validated by numerically solving the complete two-dimensional (2D) Navier–Stokes equation. 相似文献
94.
Kim Soo-Min Kwak Moon K. Chung Taek Soo 《Journal of Mechanical Science and Technology》2021,35(11):4859-4873
Journal of Mechanical Science and Technology - This study is concerned with the hydroelastic vibration of the flexible bottom plate of a cylindrical tank coupled with sloshing. The cylindrical tank... 相似文献
95.
Seong-Ji Ha Jongha Hwang Myung-Jun Kwak Jong-Chul Yoon Ji-Hyun Jang 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(29):2300551
Carbon-based electrocatalysts with both high activity and high stability are desirable for use in Zn–air batteries. However, the carbon corrosion reaction (CCR) is a critical obstacle in rechargeable Zn–air batteries. In this study, a cost-effective carbon-based novel material is reported with a high catalytic effect and good durability for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), prepared via a simple graphitization process. In situ growth of graphene is utilized in a 3D-metal-coordinated hydrogel by introducing a catalytic lattice of transition metal alloys. Due to the direct growth of few-layer graphene on the metal alloy decorated 3d-carbon network, greatly reduced CCR is observed in a repetitive OER test. As a result, an efficient bifunctional electrocatalytic performance is achieved with a low ΔE value of 0.63 V and good electrochemical durability for 83 h at a current density of 10 mA cm−2 in an alkaline media. Moreover, graphene-encapsulated transition metal alloys on the nitrogen-doped carbon supporter exhibit an excellent catalytic effect and good durability in a Zn–air battery system. This study suggests a straightforward way to overcome the CCR of carbon-based materials for an electrochemical catalyst with wide application in energy conversion and energy storage devices. 相似文献
96.
97.
Hyperbranched poly(ether ketone)-b-linear poly(ether ketone)-b-hyperbranched poly(ether ketone) (HLHPEK) triblock copolymers with two different block compositions were prepared as an approach to improve the mechanical brittleness of hyperbranched poly(ether ketone) (HPEK). From the time-temperature superposition of dynamic shear moduli, G′(ω) and G″(ω), of HPEK and two HLHPEKs, it was investigated that the junction points between G′(ω) and G″(ω) shifted to the higher frequencies and the rubbery plateau region spread wider over the reduced frequency axis as the linear blocks were introduced and their compositions were increased. Such changes in viscoelastic response were consequences of increase in the amount of chain entanglements additionally formed by the linear blocks. In order to verify the effect of the linear block incorporation on amelioration of the mechanical brittleness, the degree of brittleness and its improvement were evaluated from the temperature dependence of the shift factors, aTs, experimentally obtained during the superposition of the dynamic moduli and of the average viscoelastic relaxation times, τHNs, determined with empirical Havriliak-Negami distribution function. From the nonlinear curve fittings of the aTs and the τHNs by the Vogel-Tamman-Fulcher equation, the degree of brittleness for HPEK and HLHPEK triblock copolymers were quantified as values of the material parameter D, an indicative of deviation from the linear Arrhenius behavior and a measure of fragility of the given material. The tendency of increasing D values with the linear block compositions confirmed substantial improvement of the mechanical brittleness in the HLHPEK triblock copolymers compared to HPEK. Therefore, the approach to copolymerize HPEK with its chemically analogous linear counterpart was verified to be an effective strategy to impart molecular entanglements and hence ameliorate the mechanical brittleness on the basis of macroscopic rheological evaluation. 相似文献
98.
Shin Ji-Hwan Lee Dong-Han Kwak Moon K. 《Journal of Mechanical Science and Technology》2019,33(12):5761-5768
Journal of Mechanical Science and Technology - This study is concerned with the active vibration control of a cart-pendulum system. The input-shaping control alone is not sufficient to suppress... 相似文献
99.
100.
This paper deals with a time-dependent analysis of reinforced concrete (RC) frame structures considering the construction sequences. Because of the non-mechanical deformations induced by the time-dependent deformations of concrete, concrete structures usually present different behaviors when the construction sequences are changed, despite having the same structural configurations. Therefore, the time-dependent effects of concrete such as creep and shrinkage must be taken into consideration to simulate the actual behavior of RC frame structures. The material nonlinearity including the cracking of concrete is taken into consideration, and geometric nonlinearity due to the P-Δ effect is also taken into account by using the initial stress matrix. In addition, the creep deformation of concrete is described in accordance with a first-order algorithm based on the expansion of a degenerated kernel of the compliance function. Finally, correlation studies with previous numerical results and experimental data are conducted to verify the validity of the proposed model. An analysis of a 10-story RC frame structure is carried out to assess the differences in structural responses according to the construction sequences. 相似文献