Accession Number : AD0693545

Title :   OXIDE PLATELET FORMATION IN BULK TANTALUM.

Descriptive Note : Technical rept.,

Corporate Author : VIRGINIA UNIV CHARLOTTESVILLE RESEARCH LABS FOR THE ENGINEERING SCIENCES

Personal Author(s) : Kampe,Dennis J. ; Lawless,Kenneth R.

Report Date : SEP 1969

Pagination or Media Count : 55

Abstract : High purity 5 mil tantalum specimens was oxidized over the temperature range 500 to 700C in the pressure range 0.0005 to 0.05 torr oxygen. The oxidation was followed directly by joining an optical microscope and a vacuum heating stage. It was seen to proceed by the formation and growth of microscopic platelets which appeared as arrays of fine needles in the specimen surface. Samples were electropolished in a 90% H2SO4, 10% (by volume) solution at 10 volts potential. Foils were examined in both a Siemens 100 kV and RCA 500 kV electron microscope. A Cambridge Steroscan scanning electron microscope (SEM) was used to study the surface topography of the oxidized samples. Transmission electron microscopy (TEM) and selected area diffraction (SAD) showed a cubic TaO(z) has formed on the (111) tantalum plane with the orientation relationship: (110) TaO(z) coplanar with the (111) Ta. A two-fold superlattice was seen to exist on the (001) Ta grains studied. SEM established that the plattelets extended through the sample while TEM and optical methods independently indicate the platelets grew along certain well defined and unique crystallographis directions. (Author)

Descriptors :   (*TANTALUM, OXIDATION), (*CRYSTAL STRUCTURE, *TANTALUM COMPOUNDS), SURFACE PROPERTIES, X RAY DIFFRACTION, ELECTRON MICROSCOPY, CRYSTAL GROWTH, SYMMETRY(CRYSTALLOGRAPHY)

Subject Categories : Metallurgy and Metallography
      Crystallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE