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1.
W. Wieczorek S. H. Chung J. R. Stevens 《Journal of Polymer Science.Polymer Physics》1996,34(17):2911-2917
The majority of investigations carried out on polymer(SINGLEBOND) salt systems have been on polyether electrolytes at moderate temperatures where such electrolytes exhibit macroscopic uniformity. Relatively little attention has been paid to the subambient temperature region where composite electrolytes based on polyethers exhibit much higher conductivities than their pure polyether electrolyte analogues. For all of the composite systems studied the conduction mechanism changes from one in which the ions are coupled to the polymer segmental relaxations to one in which the ions are decoupled and thermally activated ionic hopping produces higher conductivities than would be expected from ion-segmental coupling and higher than observed for the base polyether(SINGLEBOND) salt system. This change has been observed at temperatures between 10 and 80°C above the respective glass transition temperatures. The relationship between this interaction and these higher conductivities at subambient temperatures is explored and discussed. © 1996 John Wiley & Sons, Inc. 相似文献
2.
I. C. McNeill L. Ackerman S. N. Gupta M. Zulfiqar S. Zulfiqar 《Journal of polymer science. Part A, Polymer chemistry》1977,15(10):2381-2392
In the subambient thermal volatilization analysis (TVA) technique, degradation products initially at ?196°C are allowed to warm up to ambient temperature in a controlled manner under vacuum conditions, and volatilization from the sample tube to a trap at ?196°C is monitored by means of a Pirani gauge. The technique is discussed in relation to earlier TVA work in which volatilization from a heated polymer sample was followed. Design and operation of a subambient TVA system are described, and examples of the application of the technique to the study of the degradation products of seven polymers are considered. 相似文献
3.
Westrum E. F. Justice B. H. Clever H. L. Johnson D. A. 《Journal of Thermal Analysis and Calorimetry》2002,70(2):361-369
Equilibrium adiabatic heat-capacity measurements have been made on zone refined samples of CeB6 and PrB6. Companion measurements made on LaB6, NdB6, and GdB6 have been reported elsewhere. These show cooperative lambda-type anomalies associated with antiferro-magnetic ordering. Except
for lanthanum hexaboride, Schottky internal crystal field levels result in significant contributions to the thermodynamic
functions. The gross thermodynamic properties at 298.15 K heat capacity (Cp/R), entropy increment (ΔT
0,m
S
0/R), and Gibbs energy function are correlated with the nature of the lanthanide. For LaB6, CeB6, PrB6, NdB6, and GdB6 the three properties are, respectively: {11.654, 12.014, 11.997, 11.916, 11.695} Cp/R; {10.001, 11.803, 12.430, 12.558, 13.982}
S0/R, and finally {4.379, 5.912, 6.232, 6.451, 7.905}Φ0
m/R.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
4.
5.
Lou DW Saito Y Zarzycki PK Ogawa M Jinno K 《Analytical and bioanalytical chemistry》2006,385(1):96-104
An improved high-performance liquid chromatographic method for separation of a number of ginsenosides has been developed.
The influence of temperature (from 0 to 25°C) on the retention and separation of the ginsenosides was studied by applying
a binary mobile phase (acetonitrile/water, 82:18 v/v) and a diol column (LiChrospher 100 Diol). The column temperature is
one of the more important parameters for the retention and separation of the components investigated. Selected thermodynamic
parameters, including changes of enthalpy (ΔH°) and entropy (ΔS°), were estimated from linear van’t Hoff plots, and possible retention mechanisms were discussed. Moreover, the best separation
conditions were selected based on optimization criteria including maximum retention time (t
R max), minimum resolution (R
s
min), and relative resolution product (r). Temperature regions close to 14°C offered the highest selectivity and almost equal distribution of the ginsenosides peaks
across the chromatogram. Under such isocratic conditions, excellent separation of chromatographic standards and selected ginseng
samples was achieved in less than 16 min. 相似文献
6.
Recent advances in the micromachining of poly(p‐xylylenes), commercially known as Parylenes, have enabled the development of novel structures and devices for microelectromechanical systems (MEMS). In particular, Parylene C (poly[chloro‐p‐xylylene]) has been explored extensively for biomedical applications of MEMS given its compatibility with micromachining processes, proven biocompatibility, and many advantageous properties including its chemical inertness, optical transparency, flexibility, and mechanical strength. Here we present a review of often used and recently developed micromachining process for Parylene C, as well as a high‐level overview of state‐of‐the‐art Parylene hybrid and free film devices for biomedical MEMS (bioMEMS) applications, including a discussion on its challenges and potential as a MEMS material. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
7.
This paper presents an improvement to the soft lithography fabrication process that uses chemical vapor deposition of poly(chloro-p-xylylene) (parylene C) to protect microfabricated masters and to improve the release of polymer devices following replica molding. Chemical vapor deposition creates nanometre thick conformal coatings of parylene C on silicon wafers having arrays of 30 μm high SU8 pillars with densities ranging from 278 to 10,040 features per mm(2) and aspect ratios (height : width) from 1 : 1 to 6 : 1. A single coating of parylene C was sufficient to permanently promote poly(dimethyl)siloxane (PDMS) mold release and to protect masters for an indefinite number of molding cycles. We also show that the improved release properties of parylene treated masters allow for fabrication with hard polymers, such as poly(urethane), that would otherwise not be compatible with SU8 on silicon masters. Parylene C provides a robust and high performance mold release coating for soft lithography microfabrication that extends the life of microfabricated masters and improves the achievable density and aspect ratio of replicated features. 相似文献
8.
Variable temperature solution 13C NMR of [Mo(CO)3(diglyme)] shows that the chelating diglyme ligand is displaced by the monodentate solvents acetone, methanol and ethanol at low temperature. Free and coordinated solvent are observed at low temperature while at ambient temperature rapid exchange prevents the observation of coordinated solvent. 相似文献
9.
10.
A. K. Parameswaran Wei-wen Su R. N. Schicho C. N. Provan B. Malik R. M. Kelly 《Applied biochemistry and biotechnology》1988,18(1):53-73
Laboratory results from studies of three extremely thermophilic sulfur-dependent archaebacteria (Pyrodictium occultum, Pyrodictium brockii, andPyrococcus furiosus) are used to illustrate both metabolic characteristics and engineering challenges associated with bacteria growing around
100°C. Low biomass yields, production of large amounts of hydrogen sulfide, and, in one instance, metabolic formation of a
growth-inhibiting product are among the many characteristics that complicate the development of bioreactors and protocols
for culturing these microorganisms. Engineering considerations related to the metabolic features of the sulfur-dependent archaebacteria
are also discussed 相似文献
11.
A. G. Bogachev M. V. Korobov V. M. Senyavin A. V. Markin V. A. Davydov A. V. Rakhmanina 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(5):693-696
Experimental and literature data were used to calculate the Gibbs energies of polymerized C60 phases and construct the equilibrium T-p phase diagram of fullerene C60 at temperatures from 0 to 1000 K and pressures from 0 to 8 GPa. The diagram contains stability regions of the orthorhombic, tetragonal, and rhombohedral polymerized C60 phases and primitive cubic (PC) and face-centered cubic (FCC) nonpolymerized C60 phases. The orthorhombic phase (linear polymer) is an equilibrium phase at 298 K and 1 bar and in the adjacent region. The equilibrium line observed experimentally (FCC C60—orthorhombic phase) is well described by the phase diagram. The optimum temperatures and pressures of the synthesis of polymerized phases are determined by kinetic rather than thermodynamic parameters. 相似文献
12.
《Journal of Analytical and Applied Pyrolysis》2007,80(1-2):244-251
A study of the pyrolysis of two hydrocarbons, C2H2 and C2H4, at different temperatures has been carried out in order to compare their behaviour in terms of soot and gas yields and gas composition. Pyrolysis experiments have been performed in the same conditions for both hydrocarbons: an inlet hydrocarbon concentration of 15,000 ppmv and a temperature range of 1000–1200 °C. For C2H2 and C2H4 pyrolysis tests, the results present the same trend when increasing the temperature: an increase in soot yield, a decrease in gas yield and a similar evolution of the outlet gases. Comparatively, it can be observed that acetylene is a more sooting hydrocarbon than ethylene for a given temperature. Additionally, the study of soot reactivity with O2 and NO shows that the soot samples obtained from ethylene show a slightly higher reactivity towards O2 and NO than the soot samples formed from acetylene. 相似文献
13.
Yamanaka S Kini NS Kubo A Jida S Kuramoto H 《Journal of the American Chemical Society》2008,130(13):4303-4309
Fullerene C60 monomer crystals were compressed to a face-centered cubic (fcc) phase with a lattice parameter of a = 11.93(5) A and a micro-Vickers hardness of 4500 kg/mm2 using high-pressure and high-temperature conditions of 15 GPa at 500-600 degrees C. The hardness is compatible with that of cubic boron nitride (c-BN), suggesting the formation of a 3D C60 polymer. The single-crystal X-ray structural analysis revealed that each C60 molecule in the polymer was linked to the 12 nearest neighbors by [2+2] cycloaddition between the common pentagon-hexagon (56) edges. However, ab initio geometry optimization and molecular dynamics calculations suggested that the 3D polymer should have a rhombohedral structure with the space group of R containing [3+3] cycloaddition between the pentagons of C60 molecules within the plane perpendicular to the 3-fold axis. The higher apparent symmetry of fcc was observed as an averaged structure of different orientations of the rhombohedral structure. The R structure can be derived by only a slight rotation of each C60 unit in the (111) plane of the fcc structure. The band-structure calculation suggested that the 3D polymer (R) was a semiconductor; the activation energy for the electrical conductivity was experimentally determined to be 0.25 eV at 550 K. 相似文献
14.
The stability constantK
1of the equilibrium NH
3
+H+NH
4
+
was determined by potentiometric titration in synthetic seawaters of 5 to 40 (per mille) salinity and sodium chloride solutions between 0.2 and 0.7M ionic strength at temperatures of 5, 15 and 25°C. Moreover,K
1was determined in sulfate-free seawater of 35 salinity and 25°C. The dependence of logK
1on salinity (or ionic strength) and temperature can be reasonably well described by linear relations. TheK
1obtained for sulfate-free seawater agrees very well with earlier experimental results and theoretical predictions. From the measuredK
1and literature data on the equilibrium NH
3
(atm)NH
3
(aq., NaCl), the atmospheric concentration of ammonia at equilibrium with seawater was estimated. 相似文献
15.
E. B. Brun O. A. Shustova S. I. Kuchanov G. P. Gladyshev 《Journal of polymer science. Part A, Polymer chemistry》1980,18(8):2461-2470
A general detailed model of polymer oxidative degradation in the presence of a stabilizer-oxygen acceptor was considered. The motion of the degradation zone boundary and the sample lifetime were obtained for various conditions of the process. In particular, it is shown that within the given concentration immobile oxygen acceptor has the best stabilizing properties. The theoretical results are compared with the experimental data obtained by using two independent methods: polymer sample cracking and a change in the ESR signal. Good agreement between theory and experiment was obtained. 相似文献
16.
17.
The specific conductances of LiClO4, KSCN, KPF6, and Et4NPF6 in propylene carbonate-dimethoxyethane mixtures are reported for moderate to high concentrations at temperatures between –45°C to 25°C. The data analysis was established on the base of an empirical conductance equation permitting equally well adapted fits for all electrolyte solutions irrespective of temperature, electrolyte compound and solvent composition. The effects on the conductance resulting from ion-ion, ion-solvent interactions and solvent viscosity are rationalized in terms of the thermodynamic and hydrodynamic parameters characterizing the behaviour of electrolytes in dilute solutions. Some basic aspects are discussed for optimizing the conductance of battery electrolytes, especially those of high energy density batteries. 相似文献
18.
N. Mattern W. Pitschke A. Danzig S. Doyle 《Fresenius' Journal of Analytical Chemistry》1994,349(1-3):91-96
Experimental equipment for X-ray diffraction at high temperatures is introduced and the possibility to directly observe the evolution of the atomic (geometric) structure as a function of temperature is discussed. Recent results on crystallization investigations of amorphous iron-based alloys and on the structural development in thin molybdenum sulphide films are given. The kinetics of the process was followed by means of time resolved experiments in both cases. 相似文献
19.
The oxidizing power of hexacyanoferrate(III) in alkaline conditions is wellknown. Unfortunately many if its oxidation reactions are too slow at room temperatures for direct titrimetric procedures. A method has been developed for the determination of millimolar amounts of selenium(IV), arsenic(III), antimony(III), chromium(III), and thallium(I) using thermometric titrimetry at approximately 330 K. The reproducibility and accuracy of the method are approximately 1%. 相似文献