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


Personal Author(s) : Kaufman, Larry ; Clougherty, Edward V


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/461864.pdf


Report Date : Feb 1965


Pagination or Media Count : 202


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 cm/min 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.


Descriptors :   *REFRACTORY MATERIALS , *BORIDES , *BORON ALLOYS , ZIRCONIUM COMPOUNDS , HAFNIUM COMPOUNDS , PREPARATION , THERMODYNAMICS , HIGH TEMPERATURE , LOW PRESSURE , PHASE STUDIES , CRYSTALS , MATHEMATICAL PREDICTION , OXIDATION , SILICON , THERMOCHEMISTRY , THERMAL CONDUCTIVITY , ADDITIVES , ELECTRICAL RESISTANCE , ANTIOXIDANTS , POWDER METALS , EMISSIVITY , SINTERING , TITANIUM COMPOUNDS , EUTECTICS , HAFNIUM ALLOYS , TANTALUM COMPOUNDS


Subject Categories : Inorganic Chemistry
      Ceramics, Refractories and Glass
      Thermodynamics


Distribution Statement : APPROVED FOR PUBLIC RELEASE