NSUF 16-846: The window of gas-bubble superlattice formation in bcc metals
Gas-bubble superlattice (GBS) have been observed for decades, they can form either by gas ion implantation or by nuclear transmutation. Although many possible GBS formation mechanisms have been proposed previously, a clear understanding is still missing. Gas bubble superlattice typically form adopts the same structure as the matrix crystal structure, while Gan et al. (Journal of Nuclear Materials, 396 (2010): 234-239. ) recently reported that Xenon bubbles form a fcc superlattice in a bcc uranium-molybdenum alloy under neutron irradiation. In general, the gas-bubble diameter is about 2 nm, uniformly distributed in the matrix, however, Johnson et al. (Nature, 347(1990): 265-267.) reported that a “macrolattice” with a bubble diameter of about 60 nm coexisted with the small-bubble lattice in helium-implanted gold. Understanding the fundamental mechanism of GBS formation in irradiated materials is crucial for the development of advanced nuclear materials with desired properties in a controllable way. Here we hypothesize that the driving mechanism behind GBS formation is anisotropy, either in elasticity or via self-interstitial atom diffusion. To test this hypothesis, a few materials of unique isotropic/anisotropic properties will be investigated, using closely correlated ion implantation experiments and simulations. In this proposal, two pure metals, molybdenum (Mo) and tungsten (W), will be implanted with noble gas ions. Tungsten is elastically isotropic, while its self-interstitial atom (SIA) diffusion is anisotropic, molybdenum is elastically anisotropic and its SIA diffusion is also anisotropic.
Additional Info
| Field | Value |
|---|---|
| Abstract | Gas-bubble superlattice (GBS) have been observed for decades, they can form either by gas ion implantation or by nuclear transmutation. Although many possible GBS formation mechanisms have been proposed previously, a clear understanding is still missing. Gas bubble superlattice typically form adopts the same structure as the matrix crystal structure, while Gan et al. (Journal of Nuclear Materials, 396 (2010): 234-239. ) recently reported that Xenon bubbles form a fcc superlattice in a bcc uranium-molybdenum alloy under neutron irradiation. In general, the gas-bubble diameter is about 2 nm, uniformly distributed in the matrix, however, Johnson et al. (Nature, 347(1990): 265-267.) reported that a “macrolattice” with a bubble diameter of about 60 nm coexisted with the small-bubble lattice in helium-implanted gold. Understanding the fundamental mechanism of GBS formation in irradiated materials is crucial for the development of advanced nuclear materials with desired properties in a controllable way. Here we hypothesize that the driving mechanism behind GBS formation is anisotropy, either in elasticity or via self-interstitial atom diffusion. To test this hypothesis, a few materials of unique isotropic/anisotropic properties will be investigated, using closely correlated ion implantation experiments and simulations. In this proposal, two pure metals, molybdenum (Mo) and tungsten (W), will be implanted with noble gas ions. Tungsten is elastically isotropic, while its self-interstitial atom (SIA) diffusion is anisotropic, molybdenum is elastically anisotropic and its SIA diffusion is also anisotropic. |
| Award Announced Date | 2016-12-16T07:48:07.277 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Kevin Field |
| Irradiation Facility | None |
| PI | Cheng Sun |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 846 |