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Ceramic Materials
Published in Fred D. Barlow, Aicha Elshabini, Ceramic Interconnect Technology Handbook, 2018
The breakdown voltage is a function of numerous variables, including the concentration of mobile ionic impurities, grain boundaries, and the degree of stoichiometry. In most applications, the breakdown voltage is sufficiently high not to be an issue. However, there are two instances in which it must be considered: At elevated temperatures created by localized power dissipation or high ambient temperature, the breakdown voltage may drop by orders of magnitude. Combined with a high potential gradient, this condition may be susceptible to breakdown.The surface of most ceramics is highly “wettable,” in that moisture tends to spread rapidly. Under conditions of high humidity, coupled with surface contamination, the effective breakdown voltage is much lower than the intrinsic value.
Capacitors and capacitance
Published in John Bird, Electrical and Electronic Principles and Technology, 2017
Fig. 8.4 shows two parallel conducting plates separated from each other by air. They are connected to opposite terminals of a battery of voltage V volts. There is therefore an electric field in the space between the plates. If the plates are close together, the electric lines of force will be straight and parallel and equally spaced, except near the edge where fringing will occur (see Fig. 8.2). Over the area in which there is negligible fringing, Electricfield strength,E=Vdvolts/metre where d is the distance between the plates. Electric field strength is also called potential gradient.
Atmospheric Plasmas for Carbon Nanotubes (CNTs)
Published in R. Mohan Sankaran, Plasma Processing of Nanomaterials, 2017
Jae Beom Park, Se Jin Kyung, Geun Young Yeom
A corona discharge is defined as a luminous glow localized in space around a sharp tip in a highly nonuniform electric field. Corona discharges are electrical discharges formed by ionization of a fluid surrounding a conductor, which occurs when the potential gradient at the sharp tip exceeds a certain value but is not sufficient to cause complete electrical breakdown or arcing [58–60]. The Siemens research team [61] was the first to propose the use of a corona discharge to generate ozone for disinfecting water. This was the first report that applied plasmas for inactivation of microorganisms. Later, Menashi [62] used a pulsed RF-driven corona discharge to form a plasma at atmospheric pressures. This plasma could be described as a Townsend or negative glow discharge depending upon the field and potential distribution. By applying a high voltage to the sharp electrode, small localized discharges of very short duration can be observed in the gas gap of about 1 to 10 mm. A schematic diagram of a corona discharge system is shown in Figure 7.4. The system consists of a line of pins fastened to a power electrode. If a nonelectronegative gas such as He or Ar is used as the supply gas instead of air, the discharge is enhanced and can be operated at a relatively low voltage. The pin array is biased by a DC, AC, or pulsed power supply. The plasma usually extends about 0.5 mm from the metal tips. In the drift region outside this volume, charged species diffuse toward the planar electrode and are collected. Corona discharges in air are commonly used for ozone production [63] or for the activation of polymer surfaces before printing, pasting, or coating [64,65].
Modeling the effect of immersion fluids on the radiofrequency heating performance of cornflour
Published in Journal of Microwave Power and Electromagnetic Energy, 2022
Qianyi Chen, Damla Dag, Fanbin Kong, Ran Yang, Jiajia Chen
The distortion of electric potential distribution influenced the electric field and the temperature distribution within the cornflour samples. According to Eq. 2, the electric field is proportional to the electric potential gradient. Therefore, the electric field directions (arrow plot) pointed from top to the bottom electrodes following the directions of electric potential decrease (contour plot) and did not change much during the heating process, as shown in Figure 7. Note that the size of the arrows was uniformly used and did not indicate the magnitude of the electric field strength. Moreover, the electric field directions showed considerable differences among scenarios of various immersion fluids. For the scenarios of air and soybean oil, the electric field was distorted from the fluid domain to the edges of the cornflour samples; while for the scenario of deionized water, the electric field was distorted from the central area of the water domain (above cornflour sample) to the edges of the water domain (side of cornflour sample). The different distortions of electric potential resulted in different electric potential gradients within cornflour samples.
Experimental investigations of electrochemical micromachining of nickel aluminum bronze alloy
Published in Materials and Manufacturing Processes, 2020
Sarangapani Palani, Poovazhagan Lakshmanan, Rajkumar Kaliyamurthy
The ECMM setup shown in Fig. 2 consists of a stepper motor (12 V/0.6 A) for controlling the movement of the tool, electrolytic chamber, tool holder, and work holding fixture. The dimension of the worktable is 260 × 110 × 100 mm. During machining, the sample specimens were positioned on the platform and tightly fastened, and the electrode with a 0.4 mm diameter was fed downward into the electrolytic chamber. A work holder was submerged in the electrolyte during the micromachining process. The following parameters were used as inputs: applied electric voltage (V), feed rate of the micro-tool (MFR), duty cycle (DC), and concentration of electrolyte (EC). The potential gradient among the electrode and specimen is measured in volts. The electrolyte is mixed with water according to the chosen concentration levels.