Search results for " Dielectric"

Nanocarbon broadband analysis, temperature dependent dielectric properties and percolation thresholds

2013

The results of a broadband dielectric investigation of multi-walled CNT (MWCNT)/epoxy resin composites in wide temperature range from room temperature to 450 K are reported. Far below the percolation threshold (0.25 wt% MWCNT) the dielectric properties of the composite are mostly determined by alpha relaxation in pure polymer matrix. Close to the percolation threshold the composite shows the negative temperature coefficient (NTC) effect in the temperature region, where the pure polymer matrix becomes conductive. The activation energy increases with the MWCNT concentration far below the percolation threshold and decreases close to it (1.5 wt% MWCNT). The dielectric analysis of the MWCNT/epox…

In situ stress, strain and dielectric measurements to understand electrostriction in anodic oxides

2014

Characteristics of partial discharges in an experimental setup reproducing HVDC cable insulation operating conditions

2021

The occurrence of Partial Discharge (PD) inside a cavity subjected to HVDC voltage can be considered as one of the most likely sources of insulation ageing and failure. In practical applications, the recognition of PD under HVDC is more difficult than under AC stress because of the lower repetition rates and the impossibility to obtain a PD pattern synchronized with the waveform of the applied voltage. In this paper, the relationship between conduction phenomena in dielectrics and the occurrence of PD is investigated by means of a novel experimental setup. A couple of dielectric cells connected in series is subjected to various HVDC stress levels. The applied voltage is divided between the …

Modification of the Selectivity Properties of Tubular Ceramic Membranes after Alkaline Treatment

2017

International audience; This work focuses on the selectivity modification of ceramic membranes after a mild alkaline treatment. Filtration of pure saltwater solutions was carried out with commercial titania membranes before and after the treatment. After treatment, the rejection of NaF significantly decreased, while the rejection of NaCl and NaBr increased. Additionally, NaI and Na 2 SO 4 remained close to zero. Pore size and electrical charge being almost unchanged, only significant modifications in the dielectric effects can explain this modification of selectivity. Therefore, the surface chemistry and the interaction (nature and magnitude) with the solvent and with the species present in…

Assessing Field and Laboratory Calibration Protocols for the Diviner 2000 Probe in a Range of Soils with Different Textures

2016

Frequency domain reflectometry (FDR) downhole sensors have been increasingly used for soil moisture field monitoring because they allow measurement, even continuously, along a soil profile. Moreover, they can also be installed with minimal soil disturbance around the access tube. The objectives of the paper were to assess the field and laboratory calibration protocols for a FDR capacitance probe (Diviner 2000) for a range of soils characterized by different particle size distributions and shrink/swell potential and to propose a practical and effective protocol on the basis of undisturbed soil samples, accounting for soil shrinkage/swelling processes characterizing swelling clay soils. The e…

Modelling of Pulsed Electro Acoustic Method for Space Charge Detection on Single and Multilayer Dielectrics

Self-assembly in surfactant-based mixtures driven by acid–base reactions: bis(2-ethylhexyl) phosphoric acid–n-octylamine systems

2013

Structural and dynamic features of bis(2-ethylhexyl) phosphoric acid (HDEHP)-n-octylamine (NOA) mixtures as a function of the NOA mole fraction (X-NOA) have been investigated by SAXS, WAXS, IR, dielectric spectroscopy and polarized optical microscopy. In the 0 <= X-NOA < 0.5 range, mixtures are transparent liquids, while the abrupt formation of a waxy solid characterized by an hexagonal bidimensional structure occurs at X-NOA = 0.5. Such a composition-induced phase transition results from the synergetic effect of the progressive increase in number density of ordered HDEHP-NOA nanodomains with X-NOA. Mainly driven by an HDEHP to NOA proton transfer, the increase of structural order with X-NO…

Molecular association in water-isomeric pentanol mixtures at 25�C

1982

The results of static dielectric constant and viscosity measurements on solutions of water (concentration range 0 to 0.3 mole fraction) in 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, and 2-methyl-2-butanol together with previous results for solutions of water in n-pentanol are discussed in terms of the information that they provide on the nature and the extent of molecular association in these solutions. We conclude that in most systems this association leads to the formation of tetrahedral complexes such as H2O(ROH)4. Evidences of the correlation of water-alcohol interactions with molecular parameters (position of OH group, steric hindrance of alkyl chain) of alcohols a…

Vortex motion in Nb/PdNi/Nb trilayers: new aspects in the flux flow state

2011

We study the dynamics of vortex lines in Supercondutor/Ferromagnet/Superconductor (SFS) heterostructures at microwave frequencies. We have employed swept-frequency, Corbino-disk and resonant, dielectric-resonator techniques to obtain the field and temperature dependence of the vortex-state parameters. We concentrate here on the genuine flux-flow resistivity $\rho_{ff}$, that we access at subcritical currents using a sufficiently high driving frequency. We find that $\rho_{ff}$ does not follow the well-known Bardeen-Stephen model. Instead, it is well described by a full time-dependent Ginzburg-Landau expression at very thin F layer thickness, but changes to a previously unreported field-depe…

Low-Temperature Atomic Layer Deposition of High-k SbOx for Thin Film Transistors

2022

SbOx thin films are deposited by atomic layer deposition (ALD) using SbCl5 and Sb(NMe2)3 as antimony reactants and H2O and H2O2 as oxidizers at low temperatures. SbCl5 can react with both oxidizers, while no deposition is found to occur using Sb(NMe2)3 and H2O. For the first time, the reaction mechanism and dielectric properties of ALD-SbOx thin films are systematically studied, which exhibit a high breakdown field of ≈4 MV cm−1 and high areal capacitance ranging from 150 to 200 nF cm−2, corresponding to a dielectric constant ranging from 10 to 13. The ZnO semiconductor layer is integrated into a SbOx dielectric layer, and thin film transistors (TFTs) are successfully fabricated. A TFT with…