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*V2 , Q=V*C

Series Capacitance

When connected in series n number of capacitors have an equivalent capacitance of: 1/C1 +1/C2 + 1/C3 = 1/Cequiv

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

• f 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

R2 = 0.966

2000 4000 6000 8000 10000 12000 14000 5 10 15 20 Doping Level (% by weight) Capacitance (microfarads)

Final Results

.1057 cm. ^2 -100 Hz

R2 = 0.7686

1000 2000 3000 4000 5000 6000 7000 8000 9000 5 10 15 20 Doping Level (% by weight) Capacitance (microfarads)

Final Results

1.43 cm. ^2 -100 Hz

R2 = 0.9588

1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 5 10 15 20 Doping Level (% by weight) Capacitance (microfarads)

Initial Results

Zn 3,5

R2 = 0.1519

5000 10000 15000 20000 25000 0.5 1 1.5 2 Area (cm. ^2) Capacitance (microfarads)

Initial Results

Zn 3,5 10V Bias

R 2 = 0.2504

5000 10000 15000 20000 25000 0.5 1 1.5 2 Area (cm.^2) Capacitance (microfarads)

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