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T A Arias - One of the best experts on this subject based on the ideXlab platform.
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classical density functional theory of inhomogeneous water including explicit molecular structure and nonlinear Dielectric Response
Journal of Physical Chemistry B, 2010Co-Authors: Johannes Lischner, T A AriasAbstract:We present an accurate free-energy functional for liquid water written in terms of a set of effective potential fields in which fictitious noninteracting water molecules move. The functional contains an exact expression of the entropy of noninteracting molecules and thus provides an ideal starting point for the inclusion of complex intermolecular interactions which depend on the orientation of the interacting molecules. We show how an excess free-energy functional can be constructed to reproduce the following properties of water: the Dielectric Response; the experimental site−site correlation functions; the surface tension; the bulk modulus of the liquid and the variation of this modulus with pressure; the density of the liquid and the vapor phase; and liquid−vapor coexistence. As a demonstration, we present results for the application of this theory to the behavior of liquid water in a parallel plate capacitor. In particular, we make predictions for the Dielectric Response of water in the nonlinear regim...
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classical density functional theory of inhomogeneous water including explicit molecular structure and nonlinear Dielectric Response
arXiv: Soft Condensed Matter, 2009Co-Authors: Johannes Lischner, T A AriasAbstract:We present an accurate free-energy functional for liquid water written in terms of a set of effective potential fields in which fictitious noninteracting water molecules move. The functional contains an \emph{exact} expression of the entropy of noninteracting molecules and thus provides an ideal starting point for the inclusion of complex inter-molecular interactions which depend on the \emph{orientation} of the interacting molecules. We show how an excess free-energy functional can be constructed to reproduce the following properties of water: the Dielectric Response; the experimental site-site correlation functions; the surface tension; the bulk modulus of the liquid and the variation of this modulus with pressure; the density of the liquid and the vapor phase; and liquid-vapor coexistence. As a demonstration, we present results for the application of this theory to the behavior of liquid water in a parallel plate capacitor. In particular, we make predictions for the Dielectric Response of water in the nonlinear regime, finding excellent agreement with known data.
Hermann Weingartner - One of the best experts on this subject based on the ideXlab platform.
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the Dielectric Response of room temperature ionic liquids effect of cation variation
Journal of Physical Chemistry B, 2007Co-Authors: Hermann Weingartner, Padmanabhan Sasisanker, Corinne Daguenet, Paul J Dyson, Ingo Krossing, John M Slattery, Thomas SchubertAbstract:In continuation of recent work on the Dielectric Response of imidazolium-based ionic liquids (ILs) (J. Phys. Chem. B, 2006, 110, 12682), we report on the effect of cation variation on the frequency-dependent Dielectric permittivity up to 20 GHz of ionic liquids. The salts are comprised of pyrrolidinium, pyridinium, tetraalkylammonium, and triethylsulfonium cations combined with the bis-((trifluoromethyl)sulfonyl)imide anion. The Dielectric spectra resemble those observed for imidazolium salts with the same anion. In all cases, the major contribution results from a diffusive low-frequency Response on the time scale of several 100 ps, which shows a broadly distributed kinetics similar to that of spatially heterogeneous states in supercooled and glassy systems rather than that observed in fluid systems. There is evidence for a weak secondary process near 10−20 ps. Perhaps the most interesting difference to imidazolium salts is founded in the missing portions of the spectra due to processes beyond the upper c...
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Dielectric Response of imidazolium based room temperature ionic liquids
Journal of Physical Chemistry B, 2006Co-Authors: Corinne Daguenet, Paul J Dyson, Ingo Krossing, John M Slattery, Alla Oleinikova, Chihiro Wakai, Hermann WeingartnerAbstract:We have used microwave Dielectric relaxation spectroscopy to study the picosecond dynamics of five low-viscosity, highly conductive room temperature ionic liquids based on 1-alkyl-3-methylimidazolium cations paired with the bis((trifluoromethyl)sulfonyl)imide anion. Up to 20 GHz the Dielectric Response is bimodal. The longest relaxation component at the time scale of several 100 ps reveals strongly nonexponential dynamics and correlates with the viscosity in a manner consistent with hydrodynamic predictions for the diffusive reorientation of dipolar ions. Methyl substitution at the C2 position destroys this correlation. The time constants of the weak second process at the 20 ps time scale are practically the same for each salt. This intermediate process seems to correlate with similar modes in optical Kerr effect spectra, but its physical origin is unclear. The missing high-frequency portion of the spectra indicates relaxation beyond the upper cutoff frequency of 20 GHz, presumably due to subpicosecond tr...
Ruijin Liao - One of the best experts on this subject based on the ideXlab platform.
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grey relational analysis for insulation condition assessment of power transformers based upon conventional Dielectric Response measurement
Energies, 2017Co-Authors: Hanbo Zheng, Yiyi Zhang, Ruijin LiaoAbstract:Conventional Dielectric Response measurement techniques, for instance, recovery voltage measurement (RVM), frequency domain spectroscopy (FDS) and polarization–depolarization current (PDC) are effective nondestructive insulation monitoring techniques for oil-impregnated power transformers. Previous studies have focused mainly on some single type of Dielectric measurement method. However, the condition of oil paper insulation in transformer is affected by many factors, so it is difficult to predict the insulation status by means of a single method. In this paper, the insulation condition assessment is performed by grey relational analysis (GRA) technique after carefully investigating different Dielectric Response measurement data. The insulation condition sensitive parameters of samples with unknown insulation status are extracted from different Dielectric Response measurement data and then these are used to contrast with the standard insulation state vector models established in controlled laboratory conditions by using GRA technique for predicting insulation condition. The performance of the proposed approach is tested using both the laboratory samples and a power transformer to demonstrate that it can provide reliable and effective insulation diagnosis.
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moisture effect on the Dielectric Response and space charge behaviour of mineral oil impregnated paper insulation
Journal of Physics: Conference Series, 2011Co-Authors: G Chen, Jian Hao, Ruijin LiaoAbstract:Dielectric Response and space charge behaviour of oil-paper insulation sample with different moisture contents were investigated using the frequency Dielectric spectroscopy (FDS) and the pulsed electroacoustic (PEA) technique, respectively. The influence of moisture on the Dielectric Response and space charge behaviour of oil impregnated paper insulation was analysed. Results show that the moisture has great effect on the FDS and space charge behaviour of oil impregnated paper insulation. In the frequency range of 10-2~106Hz, the conductivity and the capacitance of oil impregnated paper increases with its moisture content. The space charge distribution of oil-paper sample with lower and higher moisture contents is very different from each other. The higher the moisture concentration of the oil impregnated paper, the easier the negative charge penetration into the insulation paper. There is a significant amount of positive charge accumulated at the paper-paper interface near to the cathode for oilpaper sample with lower moisture content. However, the positive charge appears in the middle layer paper for oil-paper sample with higher moisture content. Due to the high conductivity, the charge trapped in the oil-paper sample with higher moisture content disappears much faster than that in the oil-paper sample with lower moisture content after removing the voltage.
Xiang Ming Chen - One of the best experts on this subject based on the ideXlab platform.
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enhancement of giant Dielectric Response in cacu3ti4o12 ceramics by zn substitution
Journal of the American Ceramic Society, 2010Co-Authors: Xiang Ming ChenAbstract:Zn-substituted CaCu3Ti4O12 ceramics were synthesized by solid-state sintering. Their microstructures and Dielectric properties were investigated. Ca(Cu1−xZnx)3Ti4O12 single-phase structures were obtained up to x=0.1, and the Cu+/Cu2+ and Ti3+/Ti4+ mixed-valent structure was enhanced with increasing Zn substitution. The giant Dielectric Response was significantly enhanced by Zn substitution. The Dielectric constant increased with increasing x, and a giant Dielectric constant plateau as high as ∼9 × 104 was achieved for x=0.1 at 10 kHz, while that for x=0 was ∼3 × 104. The enhanced giant Dielectric Response was profoundly concerned with the modified mixed-valent structure.
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temperature stable giant Dielectric Response in orthorhombic samarium strontium nickelate ceramics
Journal of Applied Physics, 2009Co-Authors: Xiao Qiang Liu, Xiang Ming Chen, Hai Yan ZhuAbstract:The crystalline structure and Dielectric properties of Sm1.5Sr0.5NiO4 ceramics are presented. The present ceramics is refined as orthorhombic Bmab phase and the orthorhombic strain may change the statue of charge ordering. The temperature-stable giant Dielectric constant (∼100 000) with low Dielectric loss of ∼0.1 is observed at frequency up to 5 MHz over a broad range of temperature (150–500 K) and frequency (100 kHz–5 MHz). The grain interior should be the dominative factor which contributes the giant Dielectric Response in the present ceramics after the equivalent circuit fitting, and the thermal activated small polaronic hopping related to the charge ordering is that factor. Compared to other giant Dielectric materials, the present materials have a great potential in the practical application, especially for the high frequency application.
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giant Dielectric Response in two dimensional charge ordered nickelate ceramics
Journal of Applied Physics, 2008Co-Authors: Xiao Qiang Liu, Xiang Ming Chen, Hai Yan ZhuAbstract:Dielectric relaxations of charge-ordered Ln1.5Sr0.5NiO4 (Ln=La and Nd) ceramics were investigated over a broad temperature range. The giant Dielectric constant (over 70 000) with a low Dielectric loss of ∼0.1 was determined at high frequencies (up to 5 MHz) over a broad temperature range. There are two Dielectric relaxations in the vicinity of charge ordering temperatures. The thermal activated small polaronic hopping between two charge ordering temperatures should contribute to the giant Dielectric Response in the present ceramics. Compared to other giant Dielectric constant materials, the present materials have the notable advantage for high frequency applications.
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microstructure dependent giant Dielectric Response in cacu3ti4o12 ceramics
Solid State Communications, 2006Co-Authors: Xiang Ming Chen, Xiao Qiang Liu, R Z HouAbstract:Abstract CaCu 3 Ti 4 O 12 ceramics were prepared at the sintering temperatures ranged from 1025 to 1125 °C, and the Dielectric characteristics were evaluated together with the microstructures. The giant Dielectric constant with the maximum of 53,120 was obtained in CaCu 3 Ti 4 O 12 ceramics at room temperature and 10 kHz, and strong processing and microstructure dependence of Dielectric characteristics of the present ceramics was determined. The precipitation of the dispersed Cu-rich secondary phases of CuO and/or Cu 2 O and their network structure provided the extrinsic origins of the enhanced giant Dielectric Response, and the present findings would offer the greater potential for enhancing the giant Dielectric constant and controlling the Dielectric loss in CaCu 3 Ti 4 O 12 ceramics by optimizing the microstructures.
Johannes Lischner - One of the best experts on this subject based on the ideXlab platform.
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classical density functional theory of inhomogeneous water including explicit molecular structure and nonlinear Dielectric Response
Journal of Physical Chemistry B, 2010Co-Authors: Johannes Lischner, T A AriasAbstract:We present an accurate free-energy functional for liquid water written in terms of a set of effective potential fields in which fictitious noninteracting water molecules move. The functional contains an exact expression of the entropy of noninteracting molecules and thus provides an ideal starting point for the inclusion of complex intermolecular interactions which depend on the orientation of the interacting molecules. We show how an excess free-energy functional can be constructed to reproduce the following properties of water: the Dielectric Response; the experimental site−site correlation functions; the surface tension; the bulk modulus of the liquid and the variation of this modulus with pressure; the density of the liquid and the vapor phase; and liquid−vapor coexistence. As a demonstration, we present results for the application of this theory to the behavior of liquid water in a parallel plate capacitor. In particular, we make predictions for the Dielectric Response of water in the nonlinear regim...
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classical density functional theory of inhomogeneous water including explicit molecular structure and nonlinear Dielectric Response
arXiv: Soft Condensed Matter, 2009Co-Authors: Johannes Lischner, T A AriasAbstract:We present an accurate free-energy functional for liquid water written in terms of a set of effective potential fields in which fictitious noninteracting water molecules move. The functional contains an \emph{exact} expression of the entropy of noninteracting molecules and thus provides an ideal starting point for the inclusion of complex inter-molecular interactions which depend on the \emph{orientation} of the interacting molecules. We show how an excess free-energy functional can be constructed to reproduce the following properties of water: the Dielectric Response; the experimental site-site correlation functions; the surface tension; the bulk modulus of the liquid and the variation of this modulus with pressure; the density of the liquid and the vapor phase; and liquid-vapor coexistence. As a demonstration, we present results for the application of this theory to the behavior of liquid water in a parallel plate capacitor. In particular, we make predictions for the Dielectric Response of water in the nonlinear regime, finding excellent agreement with known data.