Temperature dependence of Kr precipitation in Ni

Conference · Sun Nov 01 04:00:00 EST 1987

OSTI ID:5574172

Birtcher, R C; Liu, A S

The precipitation of Kr injected into Ni at temperatures between 25 and 560/sup 0/C has been studied with transmission electron microscopy. The Kr precipitates in cavities which increase in size with Kr fluence. Electron diffraction and dark-field imaging demonstrate that small Kr precipitates are solid, fcc crystals aligned with each other and the Ni lattice. The Kr is held in the solid state by the pressure generated by the cavity walls, and this pressure decreases with increasing cavity size. The mismatch between the Kr and Ni lattices is as large as 55%. The average Kr lattice parameter, determined from electron diffraction at room temperature, increases with increasing Kr fluence from 0.515 nm to an asymptotic value of about 0.545 nm for implantations at temperatures of 300 C or less. This increase towards an asymptotic limit is due to expansion of the Kr lattices as precipitates grow, until the decrease in cavity pressures allows melting of solid Kr in large cavities. Diffuse electron scattering was observed from liquid Kr in large precipitates for fluences greater than 5 . 10/sup 20/Kr/sup +/m/sup -2/. Implantations at temperatures of 400 C or higher result in a bi-modal size distribution containing small solid precipitates and an additional population of larger, faceted precipitates, a larger average Kr lattice parameter for a given Kr fluence, and a higher asymptotic lattice parameter of 0.550 nm. Solid Kr seems to inhibit motion of small precipitates, and Kr melting is a precursor to faceting and growth by coalescence. 10 refs., 3 figs.

• Research Organization: Argonne National Lab., IL (USA)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 5574172
• Report Number(s): CONF-871124-74; ON: DE88005953
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360106* -- Metals & Alloys-- Radiation Effects
CHARGED PARTICLES
CRYSTALS
ELECTRON MICROSCOPY
ELEMENTS
ENERGY RANGE
FILMS
FLUIDS
GASES
ION IMPLANTATION
IONS
KEV RANGE
KEV RANGE 100-1000
KRYPTON
KRYPTON IONS
LATTICE PARAMETERS
METALS
MICROSCOPY
MONOCRYSTALS
NICKEL
NONMETALS
PRECIPITATION
RARE GASES
SEPARATION PROCESSES
THIN FILMS
TRANSITION ELEMENTS
TRANSMISSION ELECTRON MICROSCOPY