Accession Number:

AD0461864

Title:

INVESTIGATION OF BORIDE COMPOUNDS FOR VERY HIGH TEMPERATURE APPLICATIONS, Part II

Descriptive Note:

Rept. for Oct 1963-Nov 1964

Corporate Author:

MANLABS INC CAMBRIDGE MA

Report Date:

1965-02-01

Pagination or Media Count:

202.0

Abstract:

The prediction that metal rich diboride compounds would exhibit superior oxidation resistance was verified. Studies were made of high pressure hot pressed Hf and Zr diborides, the most oxidation resistant diborides, at B metal ratios between 1.7 and 2.1. Measurements between 1200 and 2200 K at partial pressures of 7 to 40 torr oxygen and flowrates of 100 to 200 cu cmmin were performed. The parabolic rate constants for HfB2 oxidation were about 10 times smaller than the corresponding ZrB2 rate constants. Si additions improved oxidation resistance below 1600 K. Measurements of vapor deposited ZrB sub 1.85 and Boride Z were performed. The best pure diboride is HfB sub 1.7. Sintering studies on ZrB2 indicated that densification proceeds by grain boundary diffusion and that ZrB sub 1.89 can be sintered to 96 theoretical density at 2100-2200 C without discontinuous grain growth. Additions of Zr to ZrB sub 1.7 permitted densification at 1800 C. Measurements were made of the thermal conductivity and emissivity of TiB2, ZrB2, HfB2, and TaB2.

Subject Categories:

  • Inorganic Chemistry
  • Ceramics, Refractories and Glass
  • Thermodynamics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE