| 摘要 |
A contact element is formed from a powdered mixture of a metal of good electrical conductivity such as silver, copper, nickel, gold, a metallic oxide such as cadmium oxide, and a metallic salt such as silver iodide, silver bromide, silver chloride, cadmium chloride, cadmium sulphate. The metallic salt is mixed with the cadmium oxide which passes a 325 mesh screen, and the mixture densified by pressure at 40,000-100,000 lbs./sq. inch, or by pressure and sintering at 1,600 DEG F. for one hour. The slugs formed are ground so that all the powder passes a 100 mesh screen, but more than half is retained by a 300 mesh screen. This powder is mixed with the powdered metal, which preferably is Merck's precipitated silver powder, cold moulded at approx. 40,000 lbs./sq. inch, and sintered at 1,600 DEG F. for twenty minutes. The preforms are finally moulded at approx. 100,000 lbs./sq. inch. to form contact elements wherein dense particles of cadmium oxide and metallic salt are jointly embedded in a matrix of conducting metal. Suitable proportions are: from 59.9 per cent.-92.9 per cent. metal of good conductivity, from 7 per cent. to 40 per cent. metallic oxide, from 0.1 per cent. to 10 per cent. metallic salt. |
