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121.
P. Pissis A. A. Konsta S. Ratkovič S. Todorovič J. Laudat 《Journal of Thermal Analysis and Calorimetry》1996,47(5):1463-1483
Broad-band ac dielectric relaxation spectroscopy (DRS) and various techniques of thermally stimulated currents (TSC) have been used to investigate molecular mobility in cereal and legume seeds, over wide ranges of water content and temperature. We focused our interest on the detailed study of the interactions between water and seed constituents. The results are quantitatively discussed, using various concepts dictated by the experimental techniques employed and in relation to the protein and carbohydrate contents of the seeds. In addition, the glass transition in the seeds, freezing and melting of water, and the protonic conduction process have been studied in some detail.Financial support through the Greek Ministry of Industry, Energy and Technology (Secretariat of Research and Technology), the Czech Ministry of Education, Youth and Sport (Dept. of International Scientific and Technological Cooperation), and the Empirikos Foundation is gratefully acknowledged. 相似文献
122.
Ionic mobility data for multicomponent electrolyte systems at low concentrations are scarce due to experimental difficulties and are actually restricted to aqueous solutions of alkali chlorides. Some new results are presented which have been obtained by using a radiotracer method valid even if one of the ionic species is present at very low concentrations (tracer ion). The following electrolyte systems (two electrolytes with a common ion in a solvent) have been investigated at a 0.5N total ionic strength: NaNO3–AgNO3, KNO3–AgNO3, LiNO3–AgNO3 either in pure water or in water-rich (acetonitrile or dimethylsulfoxide) mixed solvents. Since ionic conductivity data processing by an extended law generalized to mixtures, such as that proposed by Quint and Viallard, has proved to be delicate to handle, our experimental results have been compared with the qualitative predictions of the classical Onsager-Fuoss limiting law. The main conclusion of this work is to give clear experimental evidence of the inability of any continuum theory to predict the ionic mobilities when solvent structural effect have to be taken into account. Consequently, the ionic behavior, particularly that of the Ag+ ion, has been interpreted in terms of preferential solvation and solvent microscopic structure. The trace mobility measurements reflect the maximum structural effect on the ionic transport properties. 相似文献
123.
This work deals with uncertainty analysis of the thermal conductivity measurement using the transient hot wire method. The characterization is made from a sample of low-density, polyethylene BRALEN SA 200-22. The utilized experimental data are obtained from the test measurements performed on the air at room temperature. The sources of measurement errors are analyzed and the uncertainty of the measured value of the thermal conductivity is evaluated. The analysis shows that in the present case the uncertainty of the thermal conductivity measurement is about ±3.3% for 68% confidence level.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
124.
The heat transfer mechanisms in inorganic hollow micro-spheres filled polymer composites are analyzed in the present paper. This heat transfer includes mainly three mechanisms: (1) thermal conduction between solid and gas; (2) thermal radiation between the hollow micro-sphere surfaces; and (3) natural thermal convection of the gas in the micro-hollow spheres. A theoretical model of heat transfer in polymer/inorganic hollow micro-sphere composites is established based on the law of minimal thermal resistance and the equal law of the specific equivalent thermal conductivity, and a corresponding equation of effective thermal conductivity is derived. The effective thermal conductivity (keff) of hollow glass bead-filled polypropylene composites is estimated by using this equation, and is compared with the numerical simulations by means of a finite element method. The results show that the variation of the theoretical estimations of keff are similar to the numerical simulations at lower filler volume fraction (φf20%). Moreover, keff decreases linearly with increasing φf, and reduces somewhat with increase of filler size. 相似文献
125.
126.
The thermal conductivities of several nanofluids (dispersions of alumina nanoparticles in ethylene glycol) were measured at temperatures ranging from 298 to 411 K using a liquid metal transient hot wire apparatus. Our measurements span the widest range of temperatures that have been investigated to date for any nanofluid. A maximum in the thermal conductivity versus temperature behavior was observed at all mass fractions of nanoparticles, closely following the behavior of the base fluid (ethylene glycol). Our results confirm that additional temperature contributions inherent in Brownian motion models are not necessary to describe the temperature dependence of the thermal conductivity of nanofluids. Our results also show that the effect of mass or volume fraction of nanoparticles on the thermal conductivity of nanofluids can be correlated using the Hamilton and Crosser or Yu and Choi models with one adjustable parameter (the shape factor in the Hamilton and Crosser model, or the ordered liquid layer thickness in the Yu and Choi model). 相似文献
127.
G. Hirankumar S. Selvasekarapandian M. S. Bhuvaneswari R. Baskaran M. Vijayakumar 《Journal of Solid State Electrochemistry》2006,10(4):193-197
Thick films of pure polyvinyl alcohol and polyvinyl alcohol doped with silver nitrate with different compositions have been
prepared by solution cast technique. The FT-IR spectrum confirms the complexation process. The conductivity of the pure polyvinyl
alcohol is of the order of 10−7 Sm−1 at 90 °C, and its value increases by two orders of magnitude when doped with 20 wt% of AgNO3. The activation energy, calculated from the Arrhenius plot for all compositions of the poly vinyl alcohol doped with silver
nitrate, is between 0.24 and 0.35 eV. The migration energy for the ion in polymer electrolyte has been calculated from the
modulus spectrum, and is in good agreement with the activation energy calculated from the Arrhenius plot. The modulus spectra
indicate the non-Debye nature of the material. 相似文献
128.
高分子固体电解质研究进展 总被引:6,自引:0,他引:6
高分子固体电解质具有质轻、粘弹性了、易成膜等许多无机电解质和有机溶剂电解质所不可比拟的优点,近年来得到了很大的发展,这种新型材料的应用主要集中开发全固态锂电池和锂离子电池。本文对SPE的电性能,离子传导特性以及提高SPE性能的途径等作了综述,并对其发展前景作了简要探讨。 相似文献
129.
Petra Spitzer Bruno Rossi Yves Gaignet Stéphane Mabic Uwe Sudmeier 《Accreditation and quality assurance》2005,10(3):78-81
There is currently a major issue with the calibration of conductivity meters used for high purity water: the lack of availability of a reference material or reference methods for low conductivity ranges (conductivity below 1 S cm–1 at 25.0 °C, resistivity >1 M cm at 25.0 °C). This paper describes the current status of conductivity measurements in high purity water. A new and improved approach, currently being investigated, should allow us to make the calibration of conductivity meters used for low conductivity ranges traceable to the SI.Milipore, Milli-Q and Elix are registered trademarks of Millipore Corporation. 相似文献
130.
Jens Hartig Andreas Schnepf L. Jos de Jongh David Bono Hansgeorg Schnöckel Prof. Dr. 《无机化学与普通化学杂志》2007,633(1):63-76
Towards the Understanding of the Unexpected Properties of the Metalloid Cluster Compound [Ga84(N(SiMe3)2)20][Li6Br2(THF)20]·2Toluol In several short communications we have recently reported on the electrical and superconducting properties of the crystalline title compound 1 which contains anionic Ga84R20‐moieties. Here we present a collection of these results, complemented and interpreted by using DFT‐calculations on model clusters (Ga84(NH2)20?). These calculations allow a) a first insight into the dynamics of the Ga84‐moieties (e.g. a rotation of the central Ga2‐dumbbell) and thus an explanation of the temperature‐dependent Ga‐NMR‐spectra described recently, and b) estimations on the lattice energy of 1 and its resulting unexpected energetic stabilization compared to metallic gallium. A possible contribution of the cations in the electrical conduction mechanism of 1 can also be made feasible with model calculations. The basis for all the results presented is to be found in the “perfect” arrangement of nanoscopic Ga84‐clusters in the crystal. This theoretically predicted condition for superconductivity in a “chain” of identical metal cluster molecules is a requirement which can hardly be realized by means of physical fabrication methods. Therefore, on the one hand the results presented here make for some disillusionment in the field of nanoscience, but on the other hand, especially in the field of synthetic chemistry, they present rewarding challenges for fundamental work in the future. 相似文献