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81.
82.
Jakubus P. Adamski A. Kurzawa M. Sojka Z. 《Journal of Thermal Analysis and Calorimetry》2003,72(1):299-310
The structure and surface properties of ZrO2 strongly depend on its preparation. In the present work the impact of prolonged aging at basic conditions (pH = 9, T = 100°C, t = 48 h), on the phase composition and textural properties, obtained by calcination of the precipitate, was investigated using
several techniques conjointly (DTA/TG, DSC, XRD, porosimetry). The thermal effects accompanying the ZrO2·xH2O gel formation, the coalescence of the particles and crystallization were evaluated and discussed in terms of the structural
differences between the aged and non-aged samples.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
83.
J. A. Poulis E. Robens C. H. Massen G. Reichenauer 《Journal of Thermal Analysis and Calorimetry》2004,76(2):579-582
Jäntti introduced a method to calculate the adsorption equilibrium by measuring the actual adsorbed amount three times after a change to the gas pressure. By this method the experimental time for adsorption measurement can be considerably shortened. The procedure was developed for use in adsorption measurements where the adsorbed masses are directly measured with a balance. In the present paper we will demonstrate that the method is particularly useful in volumetric (manometric) measurements. 相似文献
84.
Crude extracellular invertase fromSclerotium rolfsii, when coupled to glutaraldehyde activated Indion 48-R, retained 70–80% activity of the soluble enzyme. Immobilization resulted
in a decrease in the pH and temperature optima but it increased the temperature stability. Km and Vmax also increased as a result of immobilization. Both soluble and immobilized invertase showed inhibition at high substrate
concentrations. The bound enzyme showed excellent stability to repeated use and retained approx 90% of its initial activity
after 8 cycles of use. 相似文献
85.
T. Hondoh H. Anzai A. Goto S. Mae A. Higashi C. C. Langway Jr. 《Journal of inclusion phenomena and macrocyclic chemistry》1990,8(1-2):17-24
We have carried out X-ray diffraction studies on single crystals of natural air-hydrate in deep ice cores recovered at Dye-3 Greenland. Integrated intensities for 470 diffracting planes were measured by an automated four-circle diffractometer. The space group determined is cubicFd3m and the lattice constant is 17.21(3) Å. These results indicate that the crystallographic structure is the Stackelberg's structure II, in contrast to the previously anticipated structure. This finding agrees with the recent results on the synthetic air-hydrate by Davidsonet al. It was also found by difference Fourier synthesis for guest molecules that electron density in a 16-hedral cage has multiple maxima displaced from the center of the cage while that in the 12-hedron was approximately spherical.Dedicated to Dr D. W. Davidson in honor of his great contributions to the sciences of inclusion phenomena. 相似文献
86.
The exces enthalpies of solution of some primary and secondary alcohols in aqueous sodium dodecylsulfate micellar solutions were measured and the results were explained by considering the distribution of alcohols between aqueous and micellar phases. The distribution constant and the enthalpy of transfer (and the standard free energy and entropy of transfer) were obtained. The thermodynamic parameters for the transfer of secondary alcohols from the aqueous to the sodium dodecylsulfate (NaDS) micellar phase differ slightly from those of the corresponding primary alcohols. For both series of alcohols the additivity rule holds for free energies of transfer whereas enthalpies and entropies display convex curves. The present data are compared to those for the transfer of the same solutes from the aqueous to the dodecyldimethylamine oxide (DDAO) and dodecyltrimethylammonium bromide (DTAB) micellar phases. The role of the hydrophilic interactions between the OH group and the micelles' head groups is formulated. The thermodynamics of the branched methyl group were determined. Furthermore, the thermodynamics of solvation of primary alcohols in water, in NaDS micelles, and in octane have been calculated using reference states based on the assumption that the empty space around alcohols in the initial and final states is the same. It is shown that the solvation of alcohols in NaDS micellar phase is enthalpy driven and that the thermodynamic properties of solvation vs. the length of the alcohol tail is the same for water and NaDS micelles whereas it is different for octane. A possible explanation for this difference is that the alkyl chain of alcohols folds in octane. 相似文献
87.
L. P. Kozeeva M. Yu. Kameneva N. V. Podberezskaya I. G. Vasilieva N. V. Kuratieva D. Yu. Naumov V. A. Nadolinnyi V. E. Fedorov 《Journal of Structural Chemistry》2004,45(2):253-261
Cooling a melt of a Bi–Sr–Ca–Cu–O system (Bi:Sr:Ca:Cu = 4:3:3:4 or 2:2:2:4) from 1000°C-1050°C yielded crystals of a new red-colored nonsuperconducting phase, accompanying the superconducting 2212 and 2201 phases. Based on the EPR spectra, it was concluded that copper is univalent in this compound. The new phase has a composition Bi2.2Sr1.6Ca1.3Cu2Ox. The X-ray diffraction pattern has been indexed, and the unit cell parameters of the phase have been determined: space group P2/m, a = 12.93, b = 4.55, c = 10.94 ; = 102.72°. 相似文献
88.
M. Slemrod 《Journal of statistical physics》1996,83(5-6):1067-1108
A discrete-velocity Boltzmann model is introduced. It is based on two principles: (i) clusters of particles move in 3 with seven fixed momenta; (ii) clusters may gain or lose particles according to the rules of Becker-Döring cluster equations. The model provides a kinetic representation of evaporation and condensation. The model is used to obtain macroscopic fluid equations which are valid into the metastable fluid regime,
, where is any positive number, is the inelastic Knudsen number, and
s
is the saturation density. 相似文献
89.
Shao Hua SHI Li Jian LIU 《中国化学快报》2006,17(3):361-364
Poly(N-isopropylacrylamide) (PNIPAM) hydrogel, which is insoluble but shrinkable or swellable in aqueous media when temperature rises or drops across 33oC1,2, has been extensively studied due to its potential applications in the fields of controlled drug … 相似文献
90.
A. K. Galwey 《Journal of Thermal Analysis and Calorimetry》2005,82(2):423-437
Summary A representational model, proposed to account for the physical changes that accompany the melting of alkali halides, was described
in Part 1 [1]. The liquid is portrayed as undergoing continual dynamic structural reorganization of its constituent ions between
individual small domains, zones of various regular, crystal-type arrays. These alternative arrangements are stabilized by
the enthalpy of melting, which, in liquids, relaxes the restriction for solids that only the single, most stable, crystal
structure can be present. The dynamic character of the melt accounts for its fluid character and the loss of long-range order
[1, 2]. This model is extended here to consider the phase diagrams of binary, common ion, alkali halide mixtures comprehensively
reviewed in [3]. Factors determining whether each of these yields a eutectic, or a solid solution, on cooling are discussed
and several trends in the 70-phase diagrams are identified. Eutectic formation, involving maintenance of the liquid state
below the melting points of the pure components, is ascribed to the participation, in an extended dynamic equilibrium, of
additional domains having the regular structures characteristic of double salts. The known crystalline double binary halides
[3], Li/Cs or Rb/F, Cl, Br or I, melt at temperatures well below those of the simpler pure component salts. It is concluded
that the set/liq model for melting, proposed in [1, 2], accounts for some important properties of the phase diagrams presented
in [3]. 相似文献