The influence of temperature on the electrical resistivity of the cellular polypropylene and the effect of activation energy
In this paper, we determine the surface and volume electrical resistivity of the 50 μm thick cellular polypropylen (VHD50), for the temperature range 393–453 K. For this we use a contemporary methodology, which consist of a voltage measurement across the sample, with a known current flowing through it. This methodology includes a three-electrode system, which allows us to estimate the resistivity of the samples, based on their corresponding total resistances. The electric fields applied for a time interval of 1 min are of the order of 200 kVm−1. The order of magnitude of surface and volume electrical resistivity is 1013 Ω and 1011 Ωm, respectively. For both types of the resistivity, the temperature dependence is an increasing or decreasing exponential function, depending on the type of the activation energy, (its average value for the temperature range mentioned above is 41,20 kJmol−1), totally confirmed by the corresponding theoretical interpretation, conditioned by the ionic conduction.The methodology and equipment used, as well as the satisfying accordance with the results, found out directly or indirectly with the consulted literature, confirm the high accuracy of experimental measurements.
Effect of Annealing on the Mechanical and Electrical Behavior of Polyurethane/Multi-Walled Carbon Nanotube Nanocomposites
The objective of this research is to investigate the effect of the annealing process on the mechanical and electrical properties of thermoplastic polyurethane/multi-walled carbon nanotube (TPU/MWCNT) nanocomposites. The TPU/MWCNT nanocomposites were prepared by melt-mixing the TPU with 1, 3, and 5 wt.% MWCNT. The TPU/MWCNT injection-molded specimens were annealed at 110°C at different annealing time intervals. The mechanical properties of TPU/MWCNT nanocomposites (Young modulus, tensile strength at yield, stress at break and strain at break) were measured before and after the annealing at constant crosshead speed of 100 mm/min. Furthermore, the DC conductivity of the TPU/MWCNT injection molding specimens was measured before and after annealing, and the percolation thresholds were determined based on following the percolation theory.
Electron transport mechanisms in thin insulating films
Tests have been performed on a number of Ta-Ta2O5-Au diodes of various thicknesses over a range of temperatures to determine the mechanism of current flow. The mechanism proposed for the current flow is field ionization of trap-type states at low temperatures and thermal ionization of these states at high temperatures and thermal ionization of these states at high temperature. High-temperature voltage-current data and low-temperature comparisons between forward and reverse characteristics agree well with the bulk-limited hypothesis and are in striking disagreement with barrier mechanisms. A discontinuity in the oxide properties is noted at a thickness of approximately 500 A. High-temperature measurements at applied voltages less than the difference in the metal work functions yield an Ohmic characteristic with an activation energy of approximately 0.1 eV, consistent with an impurity conduction process but not with a barrier process.