Influence Of AC Fields Research Articles

Influence of AC fields and electrical conduction mechanisms on the flash-onset temperature: Electronic (BiFeO3) vs. ionic conductors (8YSZ)

This work aims to clarify the influence of AC (up to 50 kHz) vs DC fields on the flash-onset temperature, emphasizing the role of the electrical conduction mechanism. BiFeO3 (BFO) is used as an example of electronic conductor while 8-mol % Yttria-stabilized zirconia (8YSZ) is used as an example of ionic conductor. For 8YSZ, a frequency dependence of the flash-onset temperature and flash-induced heating is observed. This is consistent with the different contributions found in the total electrical response of 8YSZ as characterized by impedance spectroscopy measurements. Estimations based on the blackbody radiation model suggest that 8YSZ samples attain higher temperatures under AC fields due to a more efficient heating. Moreover, a noticeable decrease in the activation energy for the electrical conduction after the flash is triggered is attributed to electronic conduction. Meanwhile, the lack of frequency response and insensitiveness to the type of electrical field found in the case of BFO can be attributed to its mainly electronic bulk conduction.

The influence of ions and radiation on tunneling of electrons from the surface of liquid helium

In work previously reported by Saville et al. [1] and Saville [2], we found that electrons tunneling from their shallow potential well above the surface of liquid helium behave as an almost ideal 1D hydrogen atom. Computations [3], without approximation or adjustable parameters, using the time dependent Schrodinger equation are in excellent agreement with measured tunneling rates. The same computation method was used to compute the influence of AC fields on the tunneling rates [3] as preparation for planned experiments. In this paper I discuss phenomena which appear to set upper and lower limits on the observable tunneling rates. Lower limits were determined by photo assisted escape due to thermal radiation and by cosmic ray generation of ions in the bulk liquid helium. Upper limits were set by the creation of excitations in the superfluid film on the top of the sample chamber when electrons impacted with energy greater than 21.6 eV. Through its influence on the tunneling rate, we were also able to measure very small changes in the electron potential at the surface due to a sub-monolayer coverage of3He.

Corrosion of mild steel subjected to alternating voltages in seawater

Relatively little information is available on corrosion of materials in marine environment under the influence of AC fields. In this study, corrosion caused by sinusoidal alternating voltage (AV) fields in 1018 carbon steel is investigated by: (i) immersion tests and (ii) characterization of corrosion products. The experimental data show that under the influence of alternating voltage (60 Hz) applied between carbon steel and a platinum mesh counter electrode, the corrosion rate of the carbon steel increases with the applied voltage then decreases as the peak voltage amplitude is increased in the range 100–600 mV. With a further increase in the voltage amplitude beyond 600 mV, the corrosion rate is observed to increase exponentially. It is speculated that the decrease in the corrosion rate is related to a passivation phenomena brought about by an increase in the pH of the diffusion layer. The influence of the pH on the carbon steel corrosion properties is also investigated. The effect of frequency of AV signal on corrosion rate is also determined and discussed.