Low-frequency dielectric relaxation of hematite and silica sols

Langmuir ◽  
1993 ◽  
Vol 9 (7) ◽  
pp. 1625-1633 ◽  
Author(s):  
Johan Kijlstra ◽  
Herman P. van Leeuwen ◽  
Johannes Lyklema
Keyword(s):  
Dielectric Relaxation ◽  
Low Frequency ◽  
Silica Sols

Dielectric Relaxation Studies of Silver Nanoparticles dispersed Liquid Crystal

2015 ◽  
Vol 8 (3) ◽  
pp. 2176-2188 ◽  
Author(s):  
Keisham Nanao Singh
Keyword(s):  
Activation Energy ◽  
Silver Nanoparticles ◽  
Liquid Crystal ◽  
Dielectric Relaxation ◽  
Relaxation Process ◽  
Relaxation Times ◽  
Low Frequency ◽  
Bulk Liquid ◽  
Molecular Rearrangement ◽  
Relaxation Studies

This article reports on the Dielectric Relaxation Studies of two Liquid Crystalline compounds - 7O.4 and 7O.6 - doped with dodecanethiol capped Silver Nanoparticles. The liquid crystal molecules are aligned homeotropically using CTAB. The low frequency relaxation process occurring above 1 MHz is fitted to Cole-Cole formula using the software Dielectric Spectra fit. The effect of the Silver Nanoparticles on the molecular dipole dynamics are discussed in terms of the fitted relaxation times, Cole-Cole distribution parameter and activation energy. The study indicate a local molecular rearrangement of the liquid crystal molecules without affecting the order of the bulk liquid crystal molecules but these local molecules surrounding the Silver Nanoparticles do not contribute to the relaxation process in the studied frequency range. The observed effect on activation energy suggests a change in interaction between the nanoparticles/liquid crystal molecules.

Dielectric Relaxation at Ultra Low Frequency

2003 ◽  
Vol 294 (1) ◽  
pp. 3-11
Author(s):  
E. R. Neagu ◽  
J. N. Marat-Mendes ◽  
C. J. Dias
Keyword(s):  
Dielectric Relaxation ◽  
Low Frequency

Low-frequency dielectric relaxation in columnar hexagonal and micellar inverse cubic mesophases

1997 ◽  
Vol 23 (6) ◽  
pp. 891-896 ◽  
Author(s):  
H. KRESSE ◽  
H. SCHMALFUSS ◽  
B. GESTBLOM ◽  
K. BORISCH ◽  
C. TSCHIERSKE
Keyword(s):  
Dielectric Relaxation ◽  
Low Frequency

Anomalously high dielectric strength and low frequency dielectric relaxation of a bent-core liquid crystal with a large kink angle

2017 ◽  
Vol 17 (6) ◽  
pp. 858-863 ◽  
Author(s):  
Anoop Kumar Srivastava ◽  
Jongyoon Kim ◽  
Sunggu Yeo ◽  
Jinyoung Jeong ◽  
E-Joon Choi ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Dielectric Relaxation ◽  
Low Frequency ◽  
Dielectric Strength ◽  
Kink Angle ◽  
High Dielectric

Low frequency dielectric relaxation study in PMMA/PS blends

1987 ◽  
Vol 18 (4) ◽  
pp. 359-373 ◽  
Author(s):  
R. Bada ◽  
M.A.Perez Jubindo ◽  
M.R. De La Fuente ◽  
I. Katime
Keyword(s):  
Dielectric Relaxation ◽  
Low Frequency ◽  
Relaxation Study

Study of the Molecular Mobility of Polysaccharide Solid Thin Layers by Dielectric Relaxation Spectroscopy

1997 ◽  
Vol 500 ◽  
Author(s):  
K. Liedermann ◽  
L. Lapčík ◽  
S. Desmedt
Keyword(s):  
Dielectric Relaxation ◽  
Low Frequency ◽  
Thin Layers ◽  
Side Chain ◽  
Relaxation Processes ◽  
Dielectric Relaxation Spectroscopy ◽  
Frequency Range ◽  
Polar Groups ◽  
Calculated Activation Energy ◽  
Β Relaxation

ABSTRACTTemperature dependence of measured dielectric relaxation spectra (DRS) in the frequency range 20 Hz - 1 MHz of hydroxyethylcellulose (HEC) are in the temperature range 100 – 350 K. of Arrhenius character with one relaxation process at 150 – 250 K. This process reflects most probably β-relaxation of the side chain groups. Calculated activation energy of this process was 5730 kJ/mole. Four types of polysaccharides were studied at 293 K temperature: hyaluronic acid (HA), chondroitin sulfate (CHS), HEC and carboxymethylcellulose (CMC), in the low-frequency range 10−5 - 100 Hz. Measured dielectric spectra were interpreted as sum of one A.C. conductivity process and of up to two relaxation processes. The relaxation processes were described by means of the Havriliak-Negami formula and their parameters were related to the molecular structure of the polymers. The low value of a in CHS is related to its strong coupling due to the presence of two polar groups in its monomeric unit, whereas low values of α × β are interpreted as being due to the strong steric hindrances caused by long pendants present in HEC.

scholarly journals Effect of Interfaces on Dielectric Relaxation in La0.35Sr0.6MnO3 -YSZ

2000 ◽  
Vol 53 (5) ◽  
pp. 715
Author(s):  
Xia Zheng-Cai ◽  
Tang Chao-Qun ◽  
Zhou Dong-Xiang ◽  
Yang Jian-Hui
Keyword(s):  
Dielectric Relaxation ◽  
Complex Impedance ◽  
Low Frequency ◽  
Impedance Spectra ◽  
Mass Rate ◽  
Relaxation Properties ◽  
Diffusion Phase ◽  
Mixed Ceramic ◽  
Complex Impedance Spectra ◽  
Dielectric Relaxation Properties

The perovskite structure material La 0.35 Sr 0.6 MnO 3 was sintered in air and the mixed ceramic of a 0.35 Sr 0.6 MnO 3 and 8 mol % Y 2 O 3 +ZrO 2 with a 1:1 mass rate was also sintered in air, both at 1530 K for 12 hour. The AC complex impedance spectra have been measured and the effect of the interface between La 0.35 Sr 0.6 MnO 3 and YSZ on dielectric relaxation properties of La 0.35 Sr 0.6 MnO 3 has been investigated. A schematic of diffusion phase formation and the equivalent circuits are proposed for explaining the results. In the complex impedance spectra, the first and second semicircles correspond to the grain-boundary and interface respectively. The results show that the dielectric relaxation properties and structure of the mixed ceramic are different to that of single phase La 0.35 Sr 0.6 MnO 3 . The interface has an important effect on the electric properties of the mixed ceramic and produces a dielectric relaxation in low frequency.

On the relationship between matric potential and dielectric properties of organic free soils: a sensitivity study

2009 ◽  
Vol 46 (10) ◽  
pp. 1202-1215 ◽  
Author(s):  
Norman Wagner ◽  
Alexander Scheuermann
Keyword(s):  
Dielectric Relaxation ◽  
Low Frequency ◽  
Bound Water ◽  
Frequency Dispersion ◽  
Strong Relationship ◽  
Sensitivity Study ◽  
Relative Dielectric Permittivity ◽  
Relaxation Processes ◽  
Matric Potential ◽  
Relaxation Effects

High-frequency electromagnetic determination of moisture in porous media, (e.g., soil) is based on the strong relationship between volumetric water content and relative dielectric permittivity. In particular, in fine-grained soils the movement of water is influenced by different surface-bonding forces due to interface processes. The interface effects lead to a number of dielectric relaxation processes (free- and bound-water phase, Maxwell–Wagner effect, counterion relaxation effects). These relaxation processes are the reason for the strong frequency dependence of the electromagnetic material properties below 1 GHz. The matric potential is a measure of the bonding forces on water in the soil. Based on a thermodynamic relationship between soil matric potential and dielectric relaxation behaviour of water in different binding states, a broadband dielectric relaxation model was developed that considers low-frequency dispersion up to 1 MHz as well as losses due to direct-current conductivity. The sensitivity of the model on soil suction was systematically analyzed based on a pedotransfer function (PTF) for soil textures ranging from pure sand up to pure clay. The results are compared with known empirical and semiempirical calibration functions, as well as theoretical mixing models.

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