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排序方式: 共有355条查询结果,搜索用时 15 毫秒
1.
The relatively low capacitance of negative electrodes, as compared to the capacitance of advanced positive electrodes, poses a serious problem, since this limits the development of asymmetric supercapacitor (SC) devices with a large voltage window and enhanced power-energy characteristics. We fabricate negative SC electrodes with a high capacitance that match the capacitance of advanced positive electrodes at similar active mass loadings, as high as 37?mg?cm?2. Cyclic voltammetry, impedance spectroscopy, galvanostatic charge-discharge data and the power-energy characteristics of the asymmetric SC device exhibit good electrochemical performance for a voltage window of 1.6?V. Our approach involves the development and application of particle extraction through liquid-liquid interface (PELLI) methods, new extraction mechanisms and efficient extractors to synthesize α-FeOOH and β-FeOOH electrode materials. The use of PELLI allows agglomerate-free processing of powders, which facilitates their efficient mixing with multiwalled carbon nanotubes (MWCNT) and allows improved electrolyte access to the particle surface. Experiments to determine the properties of FeOOH-MWCNT composites provided insight into the influence of the electrode material and the structure of extractor molecules on the composite properties. The highest capacitance of 5.86?F?cm?2 for negative electrodes and low impedance were achieved using α-FeOOH-MWCNT composites and a 16-phosphonohexadecanoic acid (PHDA) extractor. This extractor allows adsorption on particles, not only at the liquid-liquid interface, but also in the bulk aqueous phase and can potentially be used as a capping agent for particle synthesis and as an extractor in the PELLI method. 相似文献
2.
DC Reynolds CE Leak KK Bajaj CE Stutz RL Jones KR Evans PW Yu WM Theis 《Canadian Metallurgical Quarterly》1989,40(9):6210-6217
3.
We present an automatic algorithm to segment all the local and global asymmetric units of a three-dimensional density map of icosahedral viruses. This approach is readily applicable to the structural analysis of a broad range of virus structures that are reconstructed using cryo-electron microscopy (cryo-EM) technique. Our algorithm includes three major steps operating on the three dimensional density map: the detection of critical points of the volumetric density function, the detection of global and local symmetry axes, and, finally, the boundary segmentation of all the asymmetric units. We demonstrate the efficacy of our algorithm and report our results on several experimental volumetric datasets, consisting of both reconstructed cryo-EM molecular density maps taken from the European Bioinformatics Institute archive, as well our own synthetically generated (blurred) maps calculated from X-ray resolution molecular structural data taken from the Protein Data Bank. 相似文献
4.
5.
Daljit S. Khurana Kulwant S. Randhawa Krishan L. Bajaj 《Journal of the science of food and agriculture》1985,36(10):959-962
Post harvest application of Isopropyl-N (3-chlorophenyl) carbamate considerably reduced the degradation of starch when potato tubers were stored in an evaporative cooling chamber. The starch degraded at a faster rate when tubers were kept under refrigerated and room storage conditions. 相似文献
6.
John M. Jewell James Jaganathan Ishwar D. Aggarwal 《Journal of the American Ceramic Society》1991,74(4):788-796
The effect of controlled heterogeneous nucleation by platinum on the crystallization of a ZrF4 -BaF2 -LaF3 -AlF3 -NaF (ZBLAN) glass was studied. Various levels of platinum were incorporated into this glass by a combination of PtCl2 -doping and melting-atmosphere variation. The effect of doping levels and melting conditions on the incorporation of platinum and the subsequent nucleation of crystals was studied by optical microscopy, scanning electron microscopy, differential scanning calorimetry (DSC), and X-ray diffraction. Increased platinum in the glass resulted in an increased number of nucleation sites for the growth of β-ZrF4 -BaF2 crystals. Analysis of isothermal and ramp-rate DSC measurements indicated that the crystallization of this glass changed from surface controlled to bulk controlled with an increased number of nuclei. This was confirmed by optical microscopy. In addition, Avrami analysis of the isothermal crystallization data gave an accurate approximation of the number of nuclei in the glass. 相似文献
7.
Vinh Q. Nguyen Jas S. Sanghera Brian Cole Pablo Pureza Frederic H. Kung Ishwar D. Aggarwal 《Journal of the American Ceramic Society》2002,85(8):2056-2058
Arsenic sulfide glass optical fibers typically possess extrinsic absorption bands in the infrared wavelength region associated with residual hydrogen and oxygen related impurities, despite using purified precursors. We report a purification process based on the addition of tellurium tetrachloride (TeCl4 ) to the glass. During melting, the chlorine from TeCl4 reacts with the hydrogen impurities to produce volatile products (e.g., HCl) that can be removed by subsequent dynamic distillation. The processing conditions have been modified accordingly to produce optical fibers with significantly reduced loss due to hydrogen sulfide impurity content (1.5 dB/m). 相似文献
8.
Abstract. A pth‐order random coefficient integer‐valued autoregressive [RCINAR(p)] model is proposed for count data. Stationarity and ergodicity properties are established. Maximum likelihood, conditional least squares, modified quasi‐likelihood and generalized method of moments are used to estimate the model parameters. Asymptotic properties of the estimators are derived. Simulation results on the comparison of the estimators are reported. The models are applied to two real data sets. 相似文献
9.
J. Bajaj S. J. C. Irvine H. O. Sankur Spyros A. Svoronos 《Journal of Electronic Materials》1993,22(8):899-906
An effective way to in situ monitor the metalorganic chemical vapor deposition (MOCVD) of HgCdTe/CdTe/ZnTe on GaAs or GaAs/Si
substrates is presented. Specular He-Ne laser reflectance was used to in situ monitor the growth rates, layer thickness, and
morphology for each layer in the grown multilayer structure. In situ monitoring has enabled precise measurements of ZnTe nucleation
and CdTe buffer layer thicknesses. Monitoring the constancy of reflectance during the thicker CdTe buffer growth where absorption
in the CdTe reduces reflectance to just the surface component has led to optimum buffer growth ensuring good quality of subsequently
grown HgCdTe. During the interdiffused multilayer process (IMP) HgCdTe growth, because multiple interfaces are present within
the absorption length, a periodic reflectance signal is maintained throughout this growth cycle. A theoretical model was developed
to extract IMP layer thicknesses from in situ recorded experimental data. For structures that required the growth of a larger
band gap HgCdTe cap layer on top of a smaller band gap active layer, in situ monitored reflectance data allowed determination
of alloy composition in the cap layer as well. Continuous monitoring of IMP parameters established the stability of growth
conditions, translating into depth uniformity of the grown material, and allowed diagnosis of growth rate instabilities in
terms of changes in the HgTe and CdTe parts of the IMP cycle. A unique advantage of in situ laser monitoring is the opportunity
to perform “interactive” crystal growth, a development that is a key to real time MOCVD HgCdTe feedback growth control. 相似文献
10.
Li-doped NiO was synthesized by molten salt method. LiNO3-LiOH flux was used as a source for Li doping. NiCl2 was added to the molten Li flux and then processed to make the Li-doped NiO material. Li:Ni ratios were maintained from 5:
1 to 30: 1 during the synthetic procedure and the chemical compositions after characterization were found from Li0.08Ni0.92O to Li0.16Ni0.84O. Li doping did not change the basic cubic structural characteristics of NiO as evidenced by XRD studies; however, the lattice
parameter decreased from 0.41769 nm in pure NiO to 0.41271 nm in Li0.16Ni0.84O. Hydrogen gas sensors were fabricated by using these materials as thick films on alumina substrates. The half surface of
each sensor was coated with the Pt catalyst. The sensor, when exposed to the hydrogen gas blended in air, heated up the catalytic
surface leaving the rest half surface (without catalyst) cold. The thermoelectric voltage thus built up along the hot and
cold surface of the Li-doped NiO made the basis for detecting hydrogen gas. The linearity of the voltage signal vs H2 concentration was checked up to 4% of H2 in air (as higher concentrations above 4.65% are explosive in air) using Li0.10Ni0.90O as the sensor material. The response time T90 and the recovery time RT90 were less than 25 sec. H2 concentration from 0.5% to 4% showed a good linearity against voltage. There was minimum interference of other gases and
hence H2 gas can easily be detected. 相似文献