scholarly journals DC conductivity of polyethylene and crosslinked polyethylene measured with a dynamic temperature program

2017 ◽  
Author(s):  
Hossein Ghorbani ◽  
Carl-Olof Olsson ◽  
Marc Jeroense
Keyword(s):  
Electrical Conductivity ◽  
Temperature Dependence ◽  
Thermal Conditions ◽  
Dc Conductivity ◽  
Protective Film ◽  
Dynamic Temperature ◽  
Operation Conditions ◽  
Heating And Cooling ◽  
Arrhenius Temperature Dependence ◽  
Arrhenius Temperature

<p>Electrical conductivity of HVDC cable insulation materials is important for its function. It is very practical to evaluate this parameter by DC conductivity measurements on press molded polymeric plates samples. While in real operation conditions, the insulation undergoes both static and dynamic thermal conditions, most of the published research in this area is still focused only on steady state thermal conditions. In this work, the focus is instead on the behavior of electrical conductivity under dynamic thermal conditions. Press molded XLPE and LDPE plate samples with different preparations are tested under 25 kV/mm DC field with a dynamic temperature profile ranging from room temperature to 90 °C.<br />It was discovered that in many cases, the measured conductivity during dynamic measurements strongly deviates from the expected Arrhenius temperature dependence; instead the conductivity shows a nonmonotonic<br />temperature dependence manifested as conductivity peaks during heating and cooling. The behavior is found to be strongly related to the type of protective film used during press molding of the sample; further degassing leads to a reduction of the nonmonotonic temperature dependence and with long<br />degassing the behavior tends to the expected Arrhenius temperature dependence.</p>

scholarly journals Intrinsic electrical properties of cable bacteria reveal an Arrhenius temperature dependence

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Robin Bonné ◽  
Ji-Ling Hou ◽  
Jeroen Hustings ◽  
Koen Wouters ◽  
Mathijs Meert ◽  
...  
Keyword(s):  
Electron Transport ◽  
Electrical Properties ◽  
Temperature Dependence ◽  
Electrical Characterization ◽  
Electrical Circuit ◽  
Parallel Fibre ◽  
Thermally Activated ◽  
Arrhenius Temperature Dependence ◽  
Equivalent Electrical Circuit Model ◽  
Arrhenius Temperature

AbstractFilamentous cable bacteria exhibit long-range electron transport over centimetre-scale distances, which takes place in a parallel fibre structure with high electrical conductivity. Still, the underlying electron transport mechanism remains undisclosed. Here we determine the intrinsic electrical properties of the conductive fibres in cable bacteria from a material science perspective. Impedance spectroscopy provides an equivalent electrical circuit model, which demonstrates that dry cable bacteria filaments function as resistive biological wires. Temperature-dependent electrical characterization reveals that the conductivity can be described with an Arrhenius-type relation over a broad temperature range (− 195 °C to + 50 °C), demonstrating that charge transport is thermally activated with a low activation energy of 40–50 meV. Furthermore, when cable bacterium filaments are utilized as the channel in a field-effect transistor, they show n-type transport suggesting that electrons are the charge carriers. Electron mobility values are ~ 0.1 cm2/Vs at room temperature and display a similar Arrhenius temperature dependence as conductivity. Overall, our results demonstrate that the intrinsic electrical properties of the conductive fibres in cable bacteria are comparable to synthetic organic semiconductor materials, and so they offer promising perspectives for both fundamental studies of biological electron transport as well as applications in microbial electrochemical technologies and bioelectronics.

scholarly journals Vitrification decoupling from α-relaxation in a metallic glass

2020 ◽  
Vol 6 (17) ◽  
pp. eaay1454
Author(s):  
Xavier Monnier ◽  
Daniele Cangialosi ◽  
Beatrice Ruta ◽  
Ralf Busch ◽  
Isabella Gallino
Keyword(s):  
Metallic Glass ◽  
Temperature Dependence ◽  
Metallic Glasses ◽  
Materials Science ◽  
Scanning Calorimetry ◽  
Fictive Temperature ◽  
Fundamental Properties ◽  
Fast Scanning Calorimetry ◽  
Arrhenius Temperature Dependence ◽  
Arrhenius Temperature

Understanding how glasses form, the so-called vitrification, remains a major challenge in materials science. Here, we study vitrification kinetics, in terms of the limiting fictive temperature, and atomic mobility related to the α-relaxation of an Au-based bulk metallic glass former by fast scanning calorimetry. We show that the time scale of the α-relaxation exhibits super-Arrhenius temperature dependence typical of fragile liquids. In contrast, vitrification kinetics displays milder temperature dependence at moderate undercooling, and thereby, vitrification takes place at temperatures lower than those associated to the α-relaxation. This finding challenges the paradigmatic view based on a one-to-one correlation between vitrification, leading to the glass transition, and the α-relaxation. We provide arguments that at moderate to deep undercooling, other atomic motions, which are not involved in the α-relaxation and that originate from the heterogeneous dynamics in metallic glasses, contribute to vitrification. Implications from the viewpoint of glasses fundamental properties are discussed.

ORIENTATIONAL GLASS TRANSITION AND STRUCTURAL RELAXATION IN SOLID C60

1993 ◽  
Vol 07 (27) ◽  
pp. 1703-1724 ◽  
Author(s):  
CHRISTOPH MEINGAST ◽  
FRANK GUGENBERGER
Keyword(s):  
Glass Transition ◽  
Temperature Dependence ◽  
Structural Relaxation ◽  
Structural Model ◽  
Local Environment ◽  
Small Deviations ◽  
Thermally Induced ◽  
Orientational Glass ◽  
Arrhenius Temperature Dependence ◽  
Arrhenius Temperature

We review recent experiments and models dealing with glass transition and the associated structural relaxation in solid C 60. This glass transition is thought to result from the freezing-in of thermally-induced dynamic orientational disorder in an otherwise orientationally-ordered crystalline structure. The structural relaxation is shown to be approximately exponential and linear (in the relaxation nomenclature), and the relaxation time nearly follows an Arrhenius temperature dependence over some 15 decades. C 60 is thus an example of an extremely ‘strong’ glass former in the ‘strong-fragile’ classification. The relaxation data are consistent with the simple structural model derived from X-ray and neutron diffraction, in which each C 60 molecule can be in two different, but energetically nearly equivalent (Δ≈10 meV ) orientational states, which are separated by an energy barrier of Ea≈250 meV . Small deviations from this simple picture are attributed to a slight temperature dependence of both Δ and Ea due to a changing local environment.

Sign in / Sign up

Export Citation Format

Share Document