done some reading, got me thinking. done some researching got me doubting... but my question is. is there a capacitor that doesn't degrade and doesn't lose capacitance over time? from all of my research it seems like this is the end conclusion but i think most of those answers were coming from the mindset of modern capacitors being used for modern technology... i'm wondering capacitors like a layden jar or some sort... do they degrade and lose capacitance over time due to 'age' principle? glass can store or hold stored energy as well last i remember and glass takes a long time to be biodegradable or no corrosion/oxidization... i'm very fascinated by electrostatic properties..
1
-
1\$\begingroup\$ Mica is ideal but expensive to find even N. Tesla needed 99.99% pure mica. So they use teflon tape for dry transformers with epoxy and synthetic purified silicon for substrates in ICs. Our body is full of pure dielectrics which can get into biology and DNA. It also has conductive dielectrics (plasma) that transport neurons which gets into Microbiology, medicine etc. So capacitors are everywhere if you look hard enough. The vacuum in outer space is perhaps the best insulator but even that leakage leads to supernova. \$\endgroup\$– Tony Stewart EE75Dec 6, 2017 at 2:26
Add a comment
|
3 Answers
\$\begingroup\$
\$\endgroup\$
Everything degrades over time, the only question is how quickly. Electrolytic caps tend to degrade faster than ceramics and film caps. One mechanism is evaporation of the wet dielectrics, which causes loss of capacitance. Parallel plate air dielectric caps like in the old tuners will last a long time. Everything is dependent on environmental conditions and how the caps are used in the application. High ripple current, high temperature and high voltage stress can lead to shorter life.
\$\begingroup\$
\$\endgroup\$
If you are looking for long term stability consider mica.
\$\begingroup\$
\$\endgroup\$
Properties of Physics
All insulators are dielectrics and all dielectrics are capacitors when placed between conductors. All batteries have much higher Farads than ultracaps, but also comes at a price of much faster aging.
Murphy's Law
Any contamination or impurities from solids, liquids or gas that can interfere with these insulation properties , will, no matter how many parts per billion they are.
If the contaminants can move under a high electric field, they can be accelerated at great speeds to collide into an electrode and will detonate those particles and cause ionization. This can lead to breakdown or corona.
A Leyden Jar named, after the Dutch city used water in glass with a rod and foil electrode. The water has a dielectric constant ~ 80 compared to air.
Thanks to Wiki.
If you want to get up to speed, read the archived works by Coulomb and Faraday.
For interesting topics
1980 effects of irradiation creating plasma in dielectric by Air Force Weapons Lab
Fast forward and discover how they crosslink polymerization is used by many industries in dielectrics like PVC wire insulation and automotive tires to improve strength by detonation of impurities using up to ~1GV in SF6. It also makes tires pretty good insulators.
To understand the limits of hi voltage in insulator, one needs to understand the precursors called Partial Discharge (PD) which occurs before transformers blow up. So they have lots of research, standard tests, PhD thesis topics and a instruments on how to detect and localize these events, from UHF antennae, optical to X-Ray detectors, due to the rise times of the negative resistance ionization of dielectrics. The repetitive nature of PD inside a dielectric is like corona in air but not visible since it is contained but can lead to internal corona which can be a severe voltage breakdown condition depending on the stored energy in the dielectric or it can be benign slow degradation.
