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991.
Observation of room temperature negative differential resistance in solution synthesized ZnO nanorod
We report the observation of negative differential resistance (NDR) in solution synthesized ZnO nanorod. The ZnO nanorod was fabricated as a two terminal planar device using lithographically patterned Au electrodes. The measured current–voltage response of the device has shown a negative differential resistance behavior. The peak-to-valley current ratio of the NDR is found to be greater than 4. The mechanism of this observed NDR effect has been explained based on charge trapping and de-trapping at the nanoscale contacts. It is the first observation of negative differential resistance effect in solution synthesized ZnO nanorod. 相似文献
992.
Sandra Mller Stefan Barwe Justus Masa Daniela Wintrich Sabine Seisel Helmut Baltruschat Wolfgang Schuhmann 《Angewandte Chemie (International ed. in English)》2020,59(4):1585-1589
Carbon corrosion at high anodic potentials is a major source of instability, especially in acidic electrolytes and impairs the long‐term functionality of electrodes. In‐depth investigation of carbon corrosion in alkaline environment by means of differential electrochemical mass spectrometry (DEMS) is prevented by the conversion of CO2 into CO32?. We report the adaptation of a DEMS system for online CO2 detection as the product of carbon corrosion in alkaline electrolytes. A new cell design allows for in situ acidification of the electrolyte to release initially dissolved CO32? as CO2 in front of the DEMS membrane and its subsequent detection by mass spectrometry. DEMS studies of a carbon‐supported nickel boride (NixB/C) catalyst and Vulcan XC 72 at high anodic potentials suggest protection of carbon in the presence of highly active oxygen evolution electrocatalysts. Most importantly, carbon corrosion is decreased in alkaline solution. 相似文献
993.
Aziz Ahmadi-khaneghah Alireza Pourali 《International Journal of Polymer Analysis and Characterization》2020,25(6):444-456
Abstract In this work, three epoxy resins including diglycidyl ethers of N,N′-bis(2-hydroxyethyl)pyromellitimide (DIDGE), bisphenol-A (BADGE), and polyethylene glycol (PEDGE) were isothermally cured by an amine curing agent possessing N,N′-disubstituted pyromellitimide units (denoted by DIDAM). DIDGE resin was synthesized from the reaction of N,N′-bis(2-hydroxyethyl)pyromellitimide with an excess of epichlorohydrin. Also, DIDAM curing agent was prepared from the reaction of pyromellitic dianhydride with an excess of ethylene diamine. Completion of the isothermal curing processes was approved by both Fourier transform-infrared spectroscopy and non-isothermal differential scanning calorimetry (DSC). The DSC traces showed only the phase transitions related to the thermal degradation of the resulting thermosets. According to the thermogravimetric analyses, the DIDGE/DIDAM thermoset showed higher thermal stability at temperatures above 425?°C than the other two thermosets. While BADGE/DIDAM and PEDGE/DIDAM thermosets showed about 70% weight loss in the thermal range of 400–850?°C, DIDGE/DIDAM thermoset was encountered with only about 40% weight loss. The glass transition temperatures (Tg ) of the resulting thermosets were determined using tan δ vs temperature plots obtained from dynamic mechanical thermal analysis. The Tg values of BADGE/DIDAM, DIDGE/DIDAM, and PEDGE/DIDAM thermosets were found to be 211?°C, 189?°C, and 81?°C, respectively. 相似文献
994.
Kirill T. Kalinin Dr. Nikita G. Sedush Petr V. Dmitryakov Prof. Sergei N. Chvalun 《ChemistryOpen》2020,9(10):1027-1032
The kinetic of D,L-lactide polymerization in presence of biocompatible zirconium acetylacetonate initiator was studied by differential scanning calorimetry in isothermal mode at various temperatures and initiator concentrations. The enthalpy of D,L-lactide polymerization measured directly in DSC cell was found to be ΔH=−17.8±1.4 kJ mol−1. Kinetic curves of D,L-lactide polymerization and propagation rate constants were determined for polymerization with zirconium acetylacetonate at concentrations of 250–1000 ppm and temperature of 160–220 °C. Using model or reversible polymerization the following kinetic and thermodynamic parameters were calculated: activation energy Ea=44.51±5.35 kJ mol−1, preexponential constant lnA=15.47±1.38, entropy of polymerization ΔS=−25.14 J mol−1 K−1. The effect of reaction conditions on the molecular weight of poly(D,L-lactide) was shown. 相似文献
995.
Two main issues are essential nowadays for practitioners in the field of polymeric materials: how a polymer will behave under dynamic loading conditions and for how long a polymer is reliable. In this sense, the time-temperature superposition principle was applied to the main viscoelastic properties (E′, E″ and tan δ) of a series of polyurethane coatings (PU-DEG-TMP) tested for mechatronic devices. Polyurethanes are derived from an ester glycol (poly(ethylene adipate) glycol), an aromatic diisocyanate (4,4′-dibenzyldiisocyanate) and di/trifunctional chain extenders - diethylene glycol (DEG) and trimethylol propane (TMP). Despite polyurethane intrinsic rheologic complexity, the moduli/loss factor curves superimpose well over several decades of reduced frequency at the glass transition temperature (Tg), 0 °C and 15 °C, the last temperature being considered the midpoint of the practical testing range. Three criteria were for checking the applicability of the time-temperature superposition: the Cole-Cole plot, the similarity between the aT calculated from both moduli (E′, E″) and the visual appearance of the final master curve. The presence of both hydrogen bonding and chemical joint points, along with some dangling chains put in a broader context the discussion of the microstructural features resulted from the application of the William-Landell-Ferry (WLF) equation. 相似文献
996.
We present a new size-modified Poisson–Boltzmann ion channel (SMPBIC) model and use it to calculate the electrostatic potential, ionic concentrations, and electrostatic solvation free energy for a voltage-dependent anion channel (VDAC) on a biological membrane in a solution mixture of multiple ionic species. In particular, the new SMPBIC model adopts a membrane surface charge density and a natural Neumann boundary condition to reflect the charge effect of the membrane on the electrostatics of VDAC. To avoid the singularity difficulties caused by the atomic charges of VDAC, the new SMPBIC model is split into three submodels such that the solution of one of the submodels is obtained analytically and contains all the singularity points of the SMPBIC model. The other two submodels are then solved numerically much more efficiently than the original SMPBIC model. As an application of this SMPBIC submodel partitioning scheme, we derive a new formula for computing the electrostatic solvation free energy. Numerical results for a human VDAC isoform 1 (hVDAC1) in three different salt solutions, each with up to five different ionic species, confirm the significant effects of membrane surface charges on both the electrostatics and ionic concentrations. The results also show that the new SMPBIC model can describe well the anion selectivity property of hVDAC1, and that the new electrostatic solvation free energy formula can significantly improve the accuracy of the currently used formula. © 2019 Wiley Periodicals, Inc. 相似文献
997.
This paper introduces the geometric assumptions and neglects of the pore size distribution calculated by BJH method, the arithmetic approximation for simplified calculation, the derivation process of each parameter, the calculation steps and key points of the pore size distribution. This paper also introduces the application scope of BJH method at the current instrument level, and how to further integrate the data. In order to get the required analysis and test report, references are provided for the subsequent adjustment of test parameters and improvement of test methods. Some problems often encountered in reading experimental reports are also discussed. 相似文献
998.
Yiyi Ou Dr. Weijie Zhou Dr. Zece Zhu Dr. Fengkai Ma Dr. Rongfu Zhou Fang Su Dr. Lirong Zheng Prof. Li Ma Prof. Hongbin Liang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(52):24018-24024
Optical multiplexing based on luminescent materials with tunable color/lifetime has potential applications in information storage and security. However, the available tunable luminescent materials reported so far still suffer from several drawbacks of low efficiency or poor stability, thus restraining their further applications. Herein, we demonstrate a strategy to develop efficient and stable lanthanide coordination polymers (LCPs) with tunable luminescence as a new option for optical multiplexing. Their multicolor emission from green to red and naked-eye-sensitive green emission with tunable lifetime (from ca. 300 to ca. 600 μs) can be controlled by host differential sensitization and energy transfer between lanthanide ions. The quantum efficiencies of developed samples range from around 20 % to 46 % and the luminescence intensity/lifetime appear quite stable in polar solvents up to ten weeks. Furthermore, with the aid of inkjet printing and concepts of luminescence lifetime imaging and time-gated imaging, we illustrate their promising applications of information storage and security in spatial and temporal domains. 相似文献
999.
This paper considers the one-dimensional dissipative cubic nonlinear Schrödinger equation with zero Dirichlet boundary conditions on a bounded domain. The equation is discretized in time by a linear implicit three-level central difference scheme, which has analogous discrete conservation laws of charge and energy. The convergence with two orders and the stability of the scheme are analysed using a priori estimates. Numerical tests show that the three-level scheme is more efficient. 相似文献
1000.
Ion-acoustic waves in plasma of warm ions and isothermal electrons using time-fractional KdV equation 下载免费PDF全文
Sayed A. El-Wakil Essam M. Abulwaf Emad K. El-Shewy Abeer A. Mahmoud 《中国物理 B》2011,20(4):40508-040508
The ion-acoustic solitary wave in collisionless unmagnetized plasma consisting of warm ions-fluid and isothermal electrons is studied using the time fractional KdV equation. The reductive perturbation method has been employed to derive the Korteweg-de Vries equation for small but finite amplitude ion-acoustic wave in warm plasma. The Lagrangian of the time fractional KdV equation is used in a similar form to the Lagrangian of the regular KdV equation with fractional derivative for the time differentiation. The variation of the functional of this Lagrangian leads to the Euler-Lagrange equation that gives the time fractional KdV equation. The variational-iteration method is used to solve the derived time fractional KdV equation. The calculations of the solution are carried out for different values of the time fractional order. These calculations show that the time fractional can be used to modulate the electrostatic potential wave instead of adding a higher order dissipation term to the KdV equation. The results of the present investigation may be applicable to some plasma environments,such as the ionosphere plasma. 相似文献