COMPARISON OF THE NANOSECOND PULSE AND DIRECT CURRENT CHARGING TO DEVELOP THE STRONGLY CHARGED ELECTRET

摘要

Recently, micro power generation using electrets has attracted much attention due to its large power output at a low frequency range. Since the theoretical power output is proportional to the square of the surface charge density of the electret, the development of a high-performance electret is required. Conventionally, electrets have been mainly manufactured by corona discharge generated using a direct current (DC) source. However, dielectric breakdown usually occurs when high voltage is applied to a material due to the increased surface charge density of the electret. Here, we focus on the nanosecond pulse (70 ns pulse width) that has ability to apply higher voltages to materials than when DC is used. A series of measurements of surface potential and thermally stimulated discharge current (TSDC) spectra is made for various polytetrafluoroethylene (PTFE) electrets, which were manufactured by DC and nanosecond pulses. It is found that the surface charge density and thermal resistibility of electric charges are improved by using nanosecond pulses. A surface charge density using a nanosecond pulse of 0.59 mC/m2 is larger than that of using DC by 59%. In addition, the thermal stability of the electret manufactured by nanosecond pulses is superior to that of by DC. Moreover, discharge energy of nanosecond pulse generator is greater than that of DC power source. Therefore, we conclude that nanosecond pulse will be more useful for manufacturing electrets than DC.