Ion-irradiation study of the exotic'' mineral neptunite: LiNa sub 2 K(Fe,Mg,Mn) sub 2 Ti sub 2 Si sub 8 O sub 24

Conference · Mon Jan 01 00:00:00 EST 1990

OSTI ID:6291118

Eby, R K; Wang, L M; Ewing, R C ^[1]; Arnold, G W ^[2]

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1. New Mexico Univ., Albuquerque, NM (USA). Dept. of Geology
2. Sandia National Labs., Albuquerque, NM (USA)

Single crystals of the rare silicate neptunite were irradiated with 600 keV Ar{sup 2+} and 1.5 MeV Kr{sup +}, and analyzed by transmission electron microscopy (TEM). Amorphization was observed in a surface layer only several hundred angstroms thick following Ar{sup 2+} irradiations up to 5.0 {times} 10{sup 13} Ar/cm{sup 2}, yet the Ar{sup 2+} ions traveled an average of 1/2 {mu}m in depth. Ionization is the dominant energy-loss process in the near surface region, and thus may contribute to the formation of the amorphous surface layer. The microstructure of the amorphous surface layer depends on the ion fluence, but the amorphous layer thickness remained constant. At the highest fluence, a narrow region below the amorphous layer shows a brittle-to-ductile strain transition, due to tensional volume-expansion of the adjacent ductile amorphous layer. Using 1.5 MeV Kr{sup +}, amorphization of the electron transparent region was completed after a fluence of 1.5 {times} 10{sup 15} Kr{sup +}/cm{sup 2}, and no further damage was observed up to 5.1 {times} 10{sup 15} Kr{sup +}/cm{sup 2}. Then, using a low fluence of 2.0 {times} 10{sup 11} Kr{sup +}/cm{sup +}, a single crystal of neptunite became a polycrystalline aggregate (grain size 10 nm) after aging 10 days at room temperature. 6 refs., 6 figs.

• Research Organization: Sandia National Labs., Albuquerque, NM (USA)
• Sponsoring Organization: ANL; CANSERC; DOE/DP; DOE/ER; National Aeronautic and Space Administration (NASA); National Science Foundation (NSF); STOFNM
• DOE Contract Number: AC04-76DP00789; FG04-84ER45099
• OSTI ID: 6291118
• Report Number(s): SAND-90-1794C; CONF-901105-54; ON: DE91005952
• Resource Relation: Conference: Fall meeting of the Materials Research Society, Boston, MA (USA), 24 Nov - 1 Dec 1990
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
SILICATE MINERALS
PHYSICAL RADIATION EFFECTS
AMORPHOUS STATE
ARGON IONS
CRYSTALS
ION BEAMS
IRRADIATION
KRYPTON IONS
BEAMS
CHARGED PARTICLES
IONS
MINERALS
RADIATION EFFECTS
360605* - Materials- Radiation Effects
656003 - Condensed Matter Physics- Interactions between Beams & Condensed Matter- (1987-)