Accession Number:

AD0647705

Title:

PERFECTION OF SINGLE CRYSTAL ALUMINA GROWN IN R. F. PLASMAS AND BY OTHER TECHNIQUES.

Descriptive Note:

Final rept. Jun 61-Jun 66,

Corporate Author:

RUTGERS - THE STATE UNIV NEW BRUNSWICK N J SCHOOL OF CERAMICS

Personal Author(s):

Report Date:

1966-06-14

Pagination or Media Count:

92.0

Abstract:

Several hybrid capacitive inductive r.f. plasma torches were developed for the growth of single crystal alumina by the Verneuil technique. A 3-tube torch with controlled mixtures of tangential and laminar flows provided good plasma stability and efficiency of powder deposition. Combined with an auxiliary heater and buffer gas flow, good crystal growth was obtained, using a 10KW generator at frequencies in the 15-25 megacycle range, and growth rates of 18-14 inch per hour. The dislocation densities and structures of crystals grown in plasmas of air, argon, nitrogen and oxygen were identical to crystals grown in oxy-hydrogen flames except for 90 degrees crystals. The difference in 90 degrees crystals is caused by the accumulation of a dense polycrystalline layer on the surface of plasma-grown crystals. The densities of prismatic and basal dislocations were about 700,000sq and 2000000sq cm, respectively. Dislocation densities measurements of alumina crystals grown by Czochralski hydrothermal, flux, and vapor deposition were one to two orders of magnitude lower than Verneuil crystals. An investigation of AlN-Al2O3 mixtures is described. A cubic form of alumina is obtained with small additions of AlN are added to Al203 and heated to high temperatures 1600C. The crystalline phases present were found to very markedly with firing temperature, atmosphere, and forming technique. Author

Subject Categories:

  • Crystallography

Distribution Statement:

APPROVED FOR PUBLIC RELEASE