Abstract: Ceramic fibers formed by the pyrolysis of organosilicon preceramic polymers are provided with increased resistivity by treating the fibers in air at temperatures of less than 1,000.degree. C. to oxidize the free carbon content of the fibers.

Abstract: A shunt device and a method are described for protecting electrical equipment when a fuse blows. The shunt device establishes a by-pass across the fuse for permitting a limited amount of current to begin to flow at a lower voltage than the fuse blowing voltage and before the fuse blows, thereby serving as a transitory relief valve for a portion of the current while minimizing or even substantially eliminating the inductive spike when the fuse blows. The shunt device is made of at least one pyrolyzed polyacrylonitrile (PPP) fiber having a selected switching voltage so that the PPP fiber switches to a low resistance state while the fuse is blowing. When the fuse and PPP characteristics are properly matched, the rate of change of the current with time is lowered, thus selectively decreasing the size of the voltage transients which occur after the fuse blows.

Abstract: An electrical device is made by partially pyrolyzing polymer material by heating the material to between 500.degree. C. and 800.degree. C. Electrodes are applied to the material at two different locations to define an electrically active element therebetween. The device exhibits negative resistance in a portion of its voltage current domain and function as bi-directional electrical switches.This application is a continuation of application Ser. No. 859,709, filed May 5, 1986, now abandoned, which is a divisional application of application ser. No. 487,401, filed Apr. 21, 1983, now U.S. Pat. No. 4,642,644.

Abstract: An electrical device is made by partially pyrolyzing polymer material by heating the material to between 500.degree. C. and 800.degree. C. Electrodes are applied to the material at two different locations to define an electrically active element therebetween. Devices made according to the teachings of the disclosure exhibit negative resistance in a portion of their voltage current domain and function as bi-directional electrical switches.

Abstract: Temperature detectors are disclosed which employ, as their active elements, pieces of partially pyrolyzed polymer material which switch to a more highly conductive state under appropriate imposed electrical bias conditions when the ambient temperature increases above the switching temperature of the detector.