共查询到20条相似文献,搜索用时 0 毫秒
1.
Alun H. Price 《Chemical physics letters》1975,30(2):320-322
A method is described which is capable of measuring the dielectric properties of liquids as a continuous function of frequency over the range 10 MHz to 18 GHz; an evaluation is made of its performance over the frequency range up to 4.2 GHz. The method described has substantial advantages in ease of operation and evaluation of results over the conventional “spot” frequency and time-domain spectrometer techniques. 相似文献
2.
The dielectric loss-factor of some non-polar liquids (e.g., n-heptane, n-nonane and n-decane) was determined at microwave frequencies from 26 to 140 GHz and at temperatures of 20 and 60°C. For all n-alkanes, relaxation maxima have been observed within this frequency region. The principal relaxation times increase with increasing length of the molecular chain (n-heptane 2.4 psec, n-nonane 2.7 psec and n-decane 3.2 psec at 20°C) and decrease with increasing temperature. The influence of polar contaminations of the alkanes on the measured loss was separately tested. 相似文献
3.
Binary dual-frequency nematic liquid crystals synthesised at the Military University of Technology were measured by dielectric means. All the investigated materials exhibit low crossover frequency. They were composed of only two molecules with longitudinal and transverse dipole moments. The main difference is the molecular weight of the molecules. Results of relaxation parameters of detected mode and crossover frequency are shown. The influence of structure on ion conductivity is discussed. The broad phase transition from an isotropic phase to a nematic one was observed. 相似文献
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Dalip Singh Nagesh Thakur D. R. Sharma 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2012,86(13):1936-1939
The dielectric constant (???) and dielectric loss (???) for dilute solutions of the binary mixture of different molar concentrations of sulfolane and DMF in benzene solution has been measured at 9.885 GHz and different temperatures (25, 30, 35, 40°C) by using standard microwave techniques. Following the single frequency concentration variational method, the dielectric relaxation time (??) and dipole moment (??) have been calculated. It is found that dielectric relaxation process can be treated as the rate process, just like the viscous flow. The presence of solute-solute molecular associations in benzene solution has been proposed. Energy parameters (??H ?, ??F ?, ??S ?) for dielectric relaxation process of binary mixture at 50% mole fraction in benzene at 25, 30, 35, and 40°C have been calculated and compared with the corresponding energy parameters (??H ??, ??F ??, ??S ??) for the viscous flow. 相似文献
6.
Wang Yanfei Liu Xiaoyu Zhao Xiaoyu Chen Zhao Yang Libin Zhu Liang 《Journal of Thermal Analysis and Calorimetry》2019,138(2):1251-1257
Journal of Thermal Analysis and Calorimetry - Solid–liquid-phase equilibrium is an important part of chemical thermodynamics, and its basic theoretical research plays a vital role in the... 相似文献
7.
The dielectric permittivities of binary mixtures of N-methylbenzenesul-fonamide (N-MBS) with benzyl alcohol, 1,2-dichloroethane, 1,4-dioxane and hexamethylphosphortriamide were measured as a function of mole fraction over the whole composition range at 30 and 50°C. The excess dielectric permittivities and the excess molar polarizations were also calculated. The excess dielectric permittivities E and excess molar polarizations PE were found to be negative for N-methylbenzene-sulfonamide mixtures with benzyl alcohol and 1,4-dioxane, E values were positive and PE values negative for mixtures with 1,2-dichloroethane, and E and PE values were clearly positive for mixtures with hexamethylphosphortriamide. The results are discussed in terms of the strength of the dipolar and hydrogen-bonding interactions between the molecules in various binary mixtures. 相似文献
8.
Dielectric permittivities of 2-pyrrolidinone - acetone, -dimethyl sulfoxide,-2-propanol, -dichloromethane and -water systems were measured as a function of mole fraction over the whole composition range at 30 and 50°C. The excess dielectric permittivities are predominantly negative for all the mixtures and the excess molar polarizations are negative except for 2-pyrrolidinone - water and 2-pyrrolidinone - dimethyl sulfoxide mixtures. The large negative excess quantities are indicative of the strong specific interactions between the like and unlike components of the solution mixtures. 相似文献
9.
通过精密自动绝热热量计测定了2-碘-3-硝基甲苯(C~7H~6INO~2)在79~373K温区的摩尔热容。实验结果表明,这个化合物在331~340K温度区间有一个固-液熔化相变,其熔化温度、摩尔熔化焓、摩尔熔化熵以及该样品的化学纯度分别为:(339.311±0.13)J·mol^-^1·K^-^1和99.73%。用热容多项式议程进行数值积分获得了该物质在298.15~370K温区每隔5K的热力学函数值。用DSC分析对它的固-液相变过程作了进一步的研究。 相似文献
10.
Mirska D Schirmer K Funari SS Langner A Dobner B Brezesinski G 《Colloids and surfaces. B, Biointerfaces》2005,40(1):51-59
The phase and miscibility behavior of a triple-chain phosphatidylcholine (TPHPC) and a single-chain surfactant (CTAB) were investigated in aqueous dispersions and in monolayers at the air/water interface. CTAB can be incorporated in the TPHPC monolayer because of its complementary molecule shape and reduces the tilt angle of TPHPC. The type of phases and the phase sequence (L2 - LS) are the same in the pure TPHPC monolayer and in the TPHPC/CTAB (80:20 mol:mol) mixture. No indication of any ordering of adsorbed DNA was observed. In the aqueous dispersions, TPHPC exhibits an inverted hexagonal phase above the chain melting. The addition of 30 mol% CTAB leads to the appearance of a lamellar Lalpha phase. The binding of DNA to the mixture is obvious but this is accompanied by a separation of the two lipids what is supported by monolayer experiments. The system has no long-term stability. The main reason seems to be not only the stronger interaction of DNA with CTAB, but also especially the unexpected weak interaction between CTAB and TPHPC. The transfection efficiency is lower compared with lipofectamine. The main disadvantage of this system is the cytotoxicity of CTAB, which could not be lowered by incorporation of CTAB in the TPHPC bilayer. 相似文献
11.
《Journal of the Less Common Metals》1985,105(1):63-68
The dielectric constant and dielectric loss tangent of mixed Mn-Mg ferrites of various compositions were measured at room temperature in the frequency range 103–105 Hz using a capacitance bridge. A qualitative explanation is given for the composition and frequency dependence of the dielectric constant. The dielectric constant for these mixed ferrites is approximately inversely proportional to the square root of the resistivity. 相似文献
12.
Grigera TS 《The Journal of chemical physics》2006,124(6):64502
We report a detailed study of the stationary points (zero-force points) of the potential energy surface (PES) of a model structural glassformer. We compare stationary points found with two different algorithms (eigenvector following and square gradient minimization), and show that the mapping between instantaneous configuration and stationary points defined by those algorithms is as different as to strongly influence the instability index K versus temperature plot, which relevance in analyzing the liquid dynamics is thus questioned. On the other hand, the plot of K versus energy is much less sensitive to the algorithm employed, showing that the energy is the good variable to discuss geometric properties of the PES. We find new evidence of a geometric transition between a minima-dominated phase and a saddle-point-dominated one. We analyze the distances between instantaneous configurations and stationary points, and find that above the glass transition, the system is closer to saddle points than to minima. 相似文献
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《Physics and Chemistry of Liquids》2012,50(2):230-241
The experimental density (ρ) and ultrasonic velocity (U) for ternary mixture containing dimethylacetamide (DMAC), acetone and diethyl ether at frequencies 2, 4, 6 and 8 MHz have been measured at temperature 308 K. These data are used to compute adiabatic compressibility (Ks), intermolecular free length (Lf), acoustic Impedance (Z), molar volume (Vm), molar sound velocity (R), molar compressibility (B), available volume (Va), Lennard-Jones potential repulsive term exponent (n), relative association (RA), interaction parameter (χ) and some excess thermo acoustic parameters for whole range of concentration of DMAC and are interpreted to elucidate molecular interaction occurring in the liquid mixture. 相似文献
15.
In a binary liquid mixture, the component possessing the lowest surface tension preferentially adsorbs at the liquid-vapor surface. In the past this adsorption behavior has been extensively investigated for critical binary liquid mixtures near the mixture's critical temperature T(c). In this fluctuation-dominated regime the adsorption is described by a universal function of the dimensionless depth zxi where xi is the bulk correlation length. Fewer studies have quantitatively examined adsorption for off-critical mixtures because, in this case, one must carefully account for both the bulk and surface crossover from the fluctuation-dominated regime (close to T(c)) to the mean-field dominated regime (far from T(c)). In this paper we compare extensive liquid-vapor ellipsometric adsorption measurements for the mixture aniline+cyclohexane at a variety of critical and noncritical compositions with the crossover theory of Kiselev and co-workers [J. Chem. Phys. 112, 3370 (2000)]. 相似文献
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An accurate microwave method for very sensitive measurements of intermolecular interactions of non-polar gases is described. It is based on the precise determination of the O factor of a resonant cavity using an indirect method and computer analysis of the experimental points. This method has been successfully applied for the measurement of the collision induced absorption of CO2 at the low-frequency spectral wing. 相似文献
18.
The interfacial and aggregation behavior of the nonionic surfactant decanoyl-N-methyl-glucamide (Mega-10) with the cationic surfactant hexadecyltriphenylphosphonium bromide (HTPB) have been studied using
interfacial tension measurements and fluorescence techniques. From interfacial tension measurements, the critical micellar
concentrations (cmc) and various interfacial thermodynamic parameters have been evaluated. The experimental results were analyzed
in the context of the pseudophase separation model, the regular solution theory, and the Maeda’s approach. These approaches
allowed us to determine the interaction parameter and composition in the mixed state. By using the static quenching method,
the mean micellar aggregation numbers of pure and mixed micelles of HTPB+Mega-10 were obtained. It was found that that the
aggregation number decreases with increasing mole fraction of HTPB. This behavior is attributed to the presence of the bulky
head group of HTPB, which creates steric head group incompatibility and/or electrostatic repulsion. The micropolarity of the
micelle was monitored with pyrene fluorescence intensity ratio. It was observed that the increasing participation of HTPB
induces the formation of micelles with a hydrated structure. The polarization of the fluorescent probe Rhodamine B was monitored
in micellar medium and found to increase with the increase of ionic content. This behavior suggests the formation of mixed
micelles with a more ordered or rigid structure. 相似文献
19.
The behavior of mixed nonionic/nonionic surfactant solutions, that is, p-(1,1,3,3-tetramethylbutyl)phenoxy poly(ethylene glycol)s Triton X-100 (TX100) and Triton X-165 (TX165) have been studied by surface tension and density measurements. The obtained results of the surface tension measurements were compared with those calculated from the relations derived by Joos, Miller, and co-workers. From the comparison, it appeared that by using these two approaches the adsorption behavior of TX100 and TX165 mixtures at different mole fractions can be predicted. The negative deviation from the linear relationship between the surface tension and composition of TX100 and TX165 mixtures in the concentration range corresponding to that of the saturated monolayer at the interface, the values of the parameters of molecular interaction, the activity coefficients, as well as the excess Gibbs energy of mixed monolayer formation calculated on the basis of Rosen and Motomura approaches proved that there is synergism in the reduction of the surface tension of aqueous solutions of TX100 and TX165 mixture when saturation of the monolayer is achieved. The negative parameters of intermolecular interaction in the mixed micelle and calculations based on MT theory of Blankschtein indicate that there is also synergism in the micelle formation for TX100 and TX165 mixture. It was also found that the values of the standard Gibbs energy of adsorption and micellization for the mixture of these two surfactants, which confirm the synergetic effect, can be predicted on the basis of the proposed equations, which include the values of the mole fraction of surfactant and excess Gibbs energy TX100 and TX165 in the monolayer and micelle. 相似文献
20.
A. Ghanadzadeh Gilani H. Ghanadzadeh Kh. Bahrpaima A. Ranjkesh 《The Journal of chemical thermodynamics》2010,42(8):967-972
Experimental results of dielectric investigations for solutions of the three butanediols {2,3-butanediol (2,3BD), 1,3-butanediol (1,3BD), and 1,4-butanediol (1,4BD)}, in 1,4-dioxane (1,4DX) are reported for various mole fractions at T = 298.2 K. Values of relative permittivity were measured at 100 kHz. The molecular dipole moments were determined using Guggenheim method. The variations of effective dipole moment and correlation factor, g, with mole fraction in these materials were investigated using Kirkwood–Frohlich equation. Dielectric measurements were also carried out on binary polar mixtures of the butanediols with 2-ethyl-1-hexanol (2EH) for various concentrations at T = 298.2 K. The Kirkwood correlation factor, the Bruggeman factor, and the excess permittivity were determined. 相似文献