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101.
A conductance study concerning the association of Na+, K+, Rb+, and Cs+ with 1,13-dibenzo-24-crown-8 in acetonitrile has been carried out at 35, 30, 25, 20, and 15°C. The observed molar conductivities were found to decrease significantly for mole ratios less than unity. A model involving 11 stoichiometry has been used to analyze the conductivity data. The stability constant, K, and the molar conductivity C for each 11 complex were determined from the conductivity data by using a nonlinear least squares curve fitting procedure. The binding sequence, based on the value of log K at 25°C, is found to be Rb+>Cs+>K+>Na+. Values of Ho and So are reported and their significance is discussed. 相似文献
102.
103.
Xu W. B. Zhou Z. F. He P. S. Pan W.-P. 《Journal of Thermal Analysis and Calorimetry》2004,78(1):113-124
The Flory's gelation theory, non-equilibrium thermodynamic fluctuation theory and Avrami equation have been used to predict
the gel time t
g and the cure behavior of epoxy resin/organo-montmorillonite/diethylenetriamine intercalated nanocomposites at various temperatures
and organo-montmorillonite loadings. The theoretical prediction is in good agreement with the experimental results obtained
by dynamic torsional vibration method, and the results show that the addition of organo-montmorillonite reduces the gelation
time t
gand increases the rate of curing reaction, the value of k, and half-time of cure after gelation point t1/2 decreases with the increasing of cure temperature, and the value of n is ~2 at the lower temperatures (<60°C) and decreases to ~1.5 as the temperature increases, and the addition of organo-montmorillonite
decreases the apparent activation energy of the cure reaction before gelation point, but has no apparent effect on the apparent
activation energy of the cure reaction after gelation point. There is no special curing process required for the formation
of epoxy resin/organo-montmorillonite/diethylenetriamine intercalated nanocomposite.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
104.
In ternary aqueous solutions, hydrophobic solutes such as alcohols tend to aggregate with surfactants to form mixed micelles. These systems can be studied by meas of the functions of transfer of hydrophobic solutes from water to aqueous solutions of surfactant. These thermodynamic functions often go through extrema in the critical micellar concentration (CMC) region of the surfactant. A simple model based on interactions between surfactant and hydrophobic solute monomers, on the distribution of the hydrophobic solute between water and the micelles and on the shift in the CMC induced by the hydrophobic solute, can simulate the magnitude and trends of the transfer functions using parameters which are mostly derived from the binary systems. In order to check the model more quantitatively, volumes and heat capacities of transfer of alcohols from water to aqueous solutions of a nonionic surfactant, octyldimethylamine oxide, were measured. A quantitative agreement was achieved with three adjustable parameters. Good fits are also obtained for the transfers to the ionic surfactants, octylamine hydrobromide and sodium dodecylsulfate. When the equilibrium displacement contribution is small, the distribution constants and the partial molar properties of the alcohols in the micellar phase agree well with the parameters obtained with similar models. 相似文献
105.
At different temperatures, the interactions between imidacloprid (IMI) and bovine serum albumin (BSA) were investigated with a fluorescence quenching spectrum, a synchronous fluorescence spectrum, a three-dimensional fluorescence spectrum and an ultraviolet-visible spectrum. The average values of bonding constants (KLB: 3.424 × 10^4 L,mol^-1), thermodynamic parameters (△H: 5.188 kJ,mol^-1, △G^(○—):-26.36 kJ,mol^-1, △S: 103.9 J,K^-1,mol^-1) and the numbers of bonding sites (n: 1.156) could be obtained through Stern-Volmer, Lineweaver-Burk and ther- modynamic equations. It was shown that the fluorescence of BSA could be quenched for its reactions with IMI to form a certain kind of new compound. The quenching belonged to a static fluorescence quenching, with a non-radiation energy transfer happening within a single molecule. The thermodynamic parameters agree with △H〉 0, △S〉0 and△G^(○-)〈0, suggesting that the binding power between IMI and BSA should be mainly a hydrophobic interaction. 相似文献
106.
Electrochemical impedance spectroscopy is used to characterize thin p-doped polypyrrole (PPy) films in propylene carbonate (PC) solutions and poly(trifluorophenyl)thiophene (PTFPT), in solutions based on sulfolane (SF). It appears that the latter film is much less swelled compared to the former one. One consequence of this difference is that the PTFPT film shows a much higher bulk resistance compared to that for the PPy film. Another important consequence is that the swelling of the PTFPT film is essentially physically non-homogeneous. Two parallel, uncoupled paths, with different chemical diffusion coefficients, model the experimental results adequately. In order to quantify the impedance spectra for both polymer films, we use a model proposed by Rubinstein et al. explaining the difference in the diffusion coefficients of Ru(bpy)3+/2+
3 within a thin Nafion film. The model can also predict the impedance spectra for composite powdery electrodes containing different particle sizes, such as composite cathodes and graphite anodes used in lithium batteries. 相似文献
107.
108.
The crystallization processes of hydrated Mg-borates, boric, magnesium hydroxide and Mg-oxychloride from MgO-B2O3-18%MgCl2-H2O supersaturated solution at 20°C have been studied by kinetic method. The crystallization solid phases were characterized
by X-ray powder diffraction, IR spectra, thermal analysis and chemical analysis. The liquid-solid phase diagram of thermodynamic
nonequilibrium state has been given. In this phase diagram, there exist eight crystallization fields, boric acid(H3BO3), trigomagneborite(MgO · 3B2O3 · 7.5H2O, MgO · 3B2O3 · 7H2O), hungchaoite(MgO · 2B2O3 · 9H2O), inderite(2MgO · 3B2O3 · 15H2O), chloropinnoite(2MgO · 2B2O3 · MgCl2 · 14H2O), magnesium hydroxide(Mg(OH)2) and magnesium oxychloride (5Mg(OH)2 · MgCl2 · 8H2O). 相似文献
109.
Thermochemistry of the solid complex Gd(Et<Subscript>2</Subscript>dtc)<Subscript>3</Subscript>(phen)
Summary A ternary solid complex Gd(Et2dtc)3(phen) has been obtained from reactions of sodium diethyldithiocarbamate (NaEt2dtc), 1,10-phenanthroline (phen) and hydrated gadolinium chloride in absolute ethanol. The title complex was described by chemical and elemental analyses, TG-DTG and IR spectrum. The enthalpy change of liquid-phase reaction of formation of the complex, ΔrHΘm(l), was determined as (-11.628±0.0204) kJ mol-1 at 298.15 K by a RD-496 III heat conduction microcalorimeter. The enthalpy change of the solid-phase reaction of formation of the complex, ΔrHΘm(s), was calculated as (145.306±0.519) kJ mol-1 on the basis of a designed thermochemical cycle. The thermodynamics of reaction of formation of the complex was investigated by changing the temperature of liquid-phase reaction. Fundamental parameters, the apparent reaction rate constant (k), the apparent activation energy (E), the pre-exponential constant (A), the reaction order (n), the activation enthalpy (ΔrHΘ≠), the activation entropy (ΔrSΘ≠), the activation free energy (ΔrGΘ≠) and the enthalpy (ΔrHΘ≠), were obtained by combination of the thermodynamic and kinetic equations for the reaction with the data of thermokinetic experiments. The constant-volume combustion energy of the complex, ΔcU, was determined as (-18673.71±8.15) kJ mol-1 by a RBC-II rotating-bomb calorimeter at 298.15 K. Its standard enthalpy of combustion, ΔcHΘm, and standard enthalpy of formation, ΔfHΘm, were calculated to be (-18692.92±8.15) kJ mol-1 and (-51.28±9.17) kJ mol-1, respectively. 相似文献
110.
Experimental and Theoretical Study of the Effect of Moisture on Methane Adsorption and Desorption by Activated Carbon at 273.5 K 下载免费PDF全文
Adsorption and desorption of methane by activated carbon (AC) at constant temperature and at various pressures were investigated. The effect of moisture was also studied. A volumetric method was used, up to 40 bar, at a temperature of 273.5 K. Results of a dry AC sample were compared with those obtained from a moist sample and two different ACs with different physical and surface properties were used. As expected, the results showed that the existence of moisture, trapped in the AC pores, could lead to a decrease in the amount of methane adsorbed and a decrease in the amount of methane delivered during desorption. To model the experimental results, a large variety of adsorption isotherms were used. The regressed parameters for the adsorption isotherms were obtained using the experimental data generated in the present study. The accuracy of the results obtained from the different adsorption isotherms was favorably compared. 相似文献