Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Silicone in Microwave
Name: Mike M.
Status: other
Age: 20s
Location: N/A 
Country: N/A
Date: 10/15/2004


Question:
Without going into too much detail, a silicone-based liquid was placed in a microwave and started sparking like aluminum. Why?


Replies:
A couple of possibilites-

1) Your silicone fluid is a good dielectric liquid with a fairly high dielectric constant and a low breakdown field. you got microwave standing waves in the large volume of it, which eventually cause dielectric breakdowns (sparks).

2) Water is lucky. When it heats and turns to vapor, the breakdown voltage is not low. If it does breakdown and form a plasma, water plus the oxygen in air make a plasma the tries to extinguish itself soon. It does not become a very conductive plasma when it evaporates and ionizes. Even so, a grape almost cut in half can make a brief electric arc, as the bridge of skin between the two halves gets too much power. Silicone is not so lucky. When it evaporates, it is a carbon-containing gas. So if its steam ignites, it will consume all the oxygen near it, and the plasma will self-sustain longer. This idea may translate into easier formation of sparks. One might get a pretty big eruption from this kind of thing, in low-boiling liquids. And a fire, if it is flammable.

All assuming your silicone liquid was clear. If it was gray, it may have had metal powder in it. If it was white or orange, it had inorganic oxides which also might make it more susceptible to microwaves.

Jim Swenson



Click here to return to the Engineering Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs

NEWTON AND ASK A SCIENTIST
Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory