| 摘要 |
A ceramic object composed principally of alumina is spray-coated with a glass-making composition mixed with an equal volume of a vehicle comprising 1.25% nitrocellulose in amyl acetate, and is thereafter fired to vitrefy the coating. The glass-making composition is ground, e.g. in isopropyl alcohol, to pass through a sieve having at least 325 openings per linear inch, has m.p. above 800 DEG C., and is substantially free from alkali metal ions. Glass-making compositions exemplified are, in percentages by weight, SiO2, 58/45 ; Al2O3 15/10 ; CaO, 10/5 ; MgO, 7/0 ; BaO 6/30 ; B2O3, 4/10 . The alumina body may contain 94% Al2O3 and be in the form of a wafer. The firing temperature may be 1300-1400 DEG C. The resulting surface coating may have softening point above 800 DEG C. and thickness 0.00075-0.0015 inch. The maximum surface roughness in an exemplified treated wafer is less than one microinch, peak to valley. The heated bodies may be used for producing microcircuitry capacitors. |
