scholarly journals Low frequency dielectric relaxation processes and ionic conductivity of montmorillonite clay nanoparticles colloidal suspension in poly(vinyl pyrrolidone)−ethylene glycol blends

2008 ◽  
Vol 2 (11) ◽  
pp. 800-809 ◽  
Author(s):  
R. J. Sengwa ◽  
S. Choudhary ◽  
S. Sankhla
Keyword(s):  
Ionic Conductivity ◽  
Ethylene Glycol ◽  
Dielectric Relaxation ◽  
Colloidal Suspension ◽  
Low Frequency ◽  
Montmorillonite Clay ◽  
Vinyl Pyrrolidone ◽  
Relaxation Processes ◽  
Clay Nanoparticles ◽  
Poly Vinyl Pyrrolidone

scholarly journals Silver micro- and nano-particles obtained using different glycols as reducing agents and measurement of their conductivity

2016 ◽  
Vol 22 (2) ◽  
pp. 227-234 ◽  
Author(s):  
Naïma Moudir ◽  
Nadji Moulaï-Mostefa ◽  
Yacine Boukennous
Keyword(s):  
Ethylene Glycol ◽  
Chemical Reduction ◽  
Colloidal Suspension ◽  
Colloidal Dispersions ◽  
Nano Particles ◽  
Vinyl Pyrrolidone ◽  
Boiling Points ◽  
Good Crystallinity ◽  
Poly Vinyl Pyrrolidone ◽  
Structural Characterizations

Synthesis of silver micro- and nano-particles for the preparation of conductive pastes for the metallization of solar cells was realized by chemical reduction in the presence and absence of poly(vinyl-pyrrolidone) (PVP). Silver nitrate was used as a precursor in the presence of three polyols (ethylene glycol, di-ethylene glycol and propylene glycol) tested at experimental temperatures near their boiling points. Six samples were obtained by this protocol. Three silver powders obtained without the use of PVP have a metallic luster appearance; however, the samples produced using an excess of PVP are in the form of stable colloidal dispersions of silver nano-particles. Structural characterizations of samples using a scanning electron microscope and X-ray diffractometer show a good crystallinity and spherical morphology. From DSC and TGA analyses, it was noticed that all the nano-silvers present in the colloidal suspension have the same thermal behavior.

Uniform Silver Nanowires Synthesis by Reducing AgNO3with Ethylene Glycol in the Presence of Seeds and Poly(Vinyl Pyrrolidone)

2002 ◽  
Vol 14 (11) ◽  
pp. 4736-4745 ◽  
Author(s):  
Yugang Sun ◽  
Yadong Yin ◽  
Brian T. Mayers ◽  
Thurston Herricks ◽  
Younan Xia
Keyword(s):  
Ethylene Glycol ◽  
Silver Nanowires ◽  
Vinyl Pyrrolidone ◽  
Poly Vinyl Pyrrolidone

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.

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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