Coating properties which increase the vacuum flashover strength of insulators
The surface flashover strengths in vacuum for several common insulators, including Lexan, Lucite, polyethylene, Macor, quartz, alumina, and an alumina-filled epoxy, have been increased using a vacuum spark discharge treatment. Analysis of the treated surfaces using Electron Spectroscopy for Chemical Analysis (ESCA) show them to be coated with a thin hydrocarbon/metal oxide layer. The formation of this high-flashover coating is strongly dependent on the amount of water vapor in the chamber during treatment. Measurements of the secondary electron emission coefficient (SEEC) show that the treated surfaces produced many more secondary electrons at energies of a few keV than do untreated samples. In current theories of electrical breakdown, an avalanche of monoenergetic secondary electrons along the dielectric surface from the cathode to the anode is believed to cause gas desorption and initiate a surface flashover. A new theory is proposed in which the monoenergetic nature of this secondary electron avalanche is destroyed due to electron-gas molecule collisions before the onset of breakdown. This phenomenon, coupled with the larger number of secondaries produced at high energies, could lead to a modified charge distribution on the surface of the treated insulators, which delays the breakdown process.
- Research Organization:
- Texas Tech Univ., Lubbock, TX (USA)
- OSTI ID:
- 7121896
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360603* -- Materials-- Properties
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
400400 -- Electrochemistry
ALUMINATES
ALUMINIUM COMPOUNDS
CALCULATION METHODS
CHALCOGENIDES
CHEMICAL ANALYSIS
CURRENTS
DATA
DATA ANALYSIS
ELECTRIC CURRENTS
ELECTRIC DISCHARGES
ELECTRICAL EQUIPMENT
ELECTRICAL INSULATORS
ELECTRON SPECTROSCOPY
EQUIPMENT
ESTERS
EXPERIMENTAL DATA
FLASHOVER
INFORMATION
LUCITE
MATERIALS
MEASURING INSTRUMENTS
MEASURING METHODS
MINERALS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC POLYMERS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PETROCHEMICALS
PETROLEUM PRODUCTS
PLASTICS
POLYACRYLATES
POLYETHYLENES
POLYMERS
POLYOLEFINS
POLYVINYLS
QUARTZ
SILICON COMPOUNDS
SILICON OXIDES
SPECTROSCOPY
SURFACE PROPERTIES
SYNTHETIC MATERIALS