Thin-film Polypropylene Capacitors Ebenge Usip University of - PowerPoint PPT Presentation

Thin-film Polypropylene Capacitors Ebenge Usip University of Southern California Advisor: Dr. Jorge Santiago-Aviles

The Capacitor � Consist of a dielectric material sandwiched between two metal electrodes � Several types of capacitors: -Electrolytic -Ceramic -Electrochemical (supercapacitors) � Properties of a parallel-plate capacitor are governed by: C=  *A/d , E=1/2*C*V 2 , Q=V*C

Series Capacitance When connected in series n number of capacitors have an equivalent capacitance of: 1/C 1 +1/C 2 + 1/C 3 = 1/C equiv

Porphyrins � Natural pigments which consist of four pyrrole subunits linked via four methine bridges � The properties of free base porphyrins can be manipulated by adding metal ions to the center of their structures

Potential Applications � Electric vehicles � Medical instrumentation � Aviation and aerospace vehicles � Military � High voltage industrial processes

The Dielectric Compound � An organic polymer called polypropylene � Relatively cheap to produce � Breakdowns at a high voltage of 640 V/µm � Can operate at high temperatures � Highly Polarizable � Commercially Available

Testing Process � Measurement of the capacitance of polypropylene dielectrics � Thickness was an important variable as it is indirectly proportional to capacitance - C= Є *A/d � A film of doped polypropylene was spin-cast on a gold- plated microscope slide � A thin layer of gold was vapor-deposited onto the film to complete the capacitor

Problems & Solutions � Increasing the capacitance of polypropylene � Polypropylene was doped with various porphyrins to see if such additives increased capacitance � The polypropylene film was initially too thin, making the capacitance too large for the capacitance bridge C=  *A/d � As a result three layers had to be deposited in order to increase thickness

Problems & Solutions � Accurate measurement of the film thickness was also difficult � An ellipsometer was used but it could not evaluate the film’s thickness with enough precision

Final Results .03516 cm. ^2 -100 Hz 14000 12000 Capacitance (microfarads) 10000 8000 6000 R 2 = 0.966 4000 2000 0 0 5 10 15 20 Doping Level (% by weight)

Final Results .1057 cm. ^2 -100 Hz 9000 8000 Capacitance (microfarads) 7000 6000 5000 4000 R 2 = 0.7686 3000 2000 1000 0 0 5 10 15 20 Doping Level (% by weight)

Final Results 1.43 cm. ^2 -100 Hz 10000 9000 8000 Capacitance (microfarads) 7000 6000 5000 4000 R 2 = 0.9588 3000 2000 1000 0 0 5 10 15 20 Doping Level (% by weight)

Initial Results Zn 3,5 25000 20000 (microfarads) Capacitance 15000 R 2 = 0.1519 10000 5000 0 0 0.5 1 1.5 2 Area (cm. ^2)

Initial Results Zn 3,5 10V Bias 25000 20000 (microfarads) Capacitance 15000 R 2 = 0.2504 10000 5000 0 0 0.5 1 1.5 2 Area (cm.^2)

Conclusion � Porphyrins have been found to be an effective additive for increasing the capacitance of polypropylene and with further research could definitely be placed into future applications

Acknowledgements � Sincere thanks to the Electrical and Systems Engineering Department, advisor Dr. Jorge Santiago, and doctoral student Paul Frail of Dr. Michael Therien’s research group in the Chemistry Department