NSUF 19-1722: In situ observation of helium out-gassing mechanism in percolating 1D/2D nanodispersoids for advanced reactor structural material and fuel cladding
The objective of this project is to reveal the underlying mechanism and quantify the effectiveness of 1D/2D dispersoids (nanotubes/nanowires or graphene sheets, respectively) in metal nanocomposites to improve their radiation resistance from helium gas accumulation. We have achieved the dispersion of 1D carbon nanotubes (CNTs) inside grains which efficiently resists lattice dislocations for both low-temperature glide and high-temperature climb, and resists the diffusion of vacancies and interstitials without sacrificing tensile ductility [1]. From in situ TEM experiments, we found that CNTs were embedded into Al grains through cold welding [2,3]. Ion irradiation of the nanocomposites demonstrated improved irradiation resistance. The CNTs survived helium ion irradiation up to 72 DPA via CNT and defect restructuring. High energy Al self-ion irradiation converts CNTs to Al4C3, but still as slender 1D nanorods which continue to catalyze the recombination of radiation defects. This special finding of the self-healing nature of these 1D dispersoids makes metal-CNT composites ideal candidates for nuclear materials. However, in spite of this significant improvement, the development of advanced nuclear reactors requires materials to tolerate extreme conditions, as high as ~1000DPA at ~1000°C. While the high temperature boosts recombination of vacancies and interstitials which affect material property degradation, the reduction in gas accumulation is not well known at these conditions. Once gases accumulate in the matrix, catastrophic failure will occur as materials swell and become brittle. To achieve this goal, we dispersed percolating 1D nanostructures into metals such as Al, Cu, and Zr further increasing interfacial area and out-gassing) without sacrificing mechanical properties.
To understand the role of the interface in 1D nanodispersions, and the underlying mechanism of out-gassing, we plan to investigate (Cu/Al)-graphene and (Cu/Al)-CNT nanocomposites using a helium ion accelerator. The local structural evolution at the interface will provide critical information on the fate of helium and further outgassing through its percolating network. We propose to use the IVEM-Tandem to observe the evolution of microstructure during ion bombardment. This study will provide insights on the role of 1D/2D percolating dispersoids to improve radiation resistance, enabling better understanding of the irradiation mechanism at the nanoscale and allowing us to design new and advanced nuclear materials.
Timeframe: All samples are ready for analysis. We can take any available time as the instrument becomes free. Experiments are expected to take 8-10 days of IVEM time.
1 So, K. P. et al. Ton-scale metal–carbon nanotube composite: The mechanism of strengthening while retaining tensile ductility. Extreme Mechanics Letters 8, 245-250 (2016). 2 Sun, J. et al. Liquid-like pseudoelasticity of sub-10-nm crystalline silver particles. Nature Materials 13, 1007-1012 (2014). 3 So, K. P. et al. Intragranular Dispersion of Carbon Nanotubes Comprehensively Improves Aluminum Alloys. Advanced Science, 1800115 (2018).
Additional Info
| Field | Value |
|---|---|
| Abstract | The objective of this project is to reveal the underlying mechanism and quantify the effectiveness of 1D/2D dispersoids (nanotubes/nanowires or graphene sheets, respectively) in metal nanocomposites to improve their radiation resistance from helium gas accumulation. We have achieved the dispersion of 1D carbon nanotubes (CNTs) inside grains which efficiently resists lattice dislocations for both low-temperature glide and high-temperature climb, and resists the diffusion of vacancies and interstitials without sacrificing tensile ductility [1]. From in situ TEM experiments, we found that CNTs were embedded into Al grains through cold welding [2,3]. Ion irradiation of the nanocomposites demonstrated improved irradiation resistance. The CNTs survived helium ion irradiation up to 72 DPA via CNT and defect restructuring. High energy Al self-ion irradiation converts CNTs to Al4C3, but still as slender 1D nanorods which continue to catalyze the recombination of radiation defects. This special finding of the self-healing nature of these 1D dispersoids makes metal-CNT composites ideal candidates for nuclear materials. However, in spite of this significant improvement, the development of advanced nuclear reactors requires materials to tolerate extreme conditions, as high as ~1000DPA at ~1000°C. While the high temperature boosts recombination of vacancies and interstitials which affect material property degradation, the reduction in gas accumulation is not well known at these conditions. Once gases accumulate in the matrix, catastrophic failure will occur as materials swell and become brittle. To achieve this goal, we dispersed percolating 1D nanostructures into metals such as Al, Cu, and Zr further increasing interfacial area and out-gassing) without sacrificing mechanical properties. To understand the role of the interface in 1D nanodispersions, and the underlying mechanism of out-gassing, we plan to investigate (Cu/Al)-graphene and (Cu/Al)-CNT nanocomposites using a helium ion accelerator. The local structural evolution at the interface will provide critical information on the fate of helium and further outgassing through its percolating network. We propose to use the IVEM-Tandem to observe the evolution of microstructure during ion bombardment. This study will provide insights on the role of 1D/2D percolating dispersoids to improve radiation resistance, enabling better understanding of the irradiation mechanism at the nanoscale and allowing us to design new and advanced nuclear materials. Timeframe: All samples are ready for analysis. We can take any available time as the instrument becomes free. Experiments are expected to take 8-10 days of IVEM time. 1 So, K. P. et al. Ton-scale metal–carbon nanotube composite: The mechanism of strengthening while retaining tensile ductility. Extreme Mechanics Letters 8, 245-250 (2016). 2 Sun, J. et al. Liquid-like pseudoelasticity of sub-10-nm crystalline silver particles. Nature Materials 13, 1007-1012 (2014). 3 So, K. P. et al. Intragranular Dispersion of Carbon Nanotubes Comprehensively Improves Aluminum Alloys. Advanced Science, 1800115 (2018). |
| Award Announced Date | 2019-05-14T14:01:26.547 |
| Awarded Institution | Center for Advanced Energy Studies |
| Facility | Microscopy and Characterization Suite |
| Facility Tech Lead | Wei-Ying Chen, Yaqiao Wu |
| Irradiation Facility | Intermediate Voltage Electron Microscopy (IVEM)-Tandem Facility |
| PI | Michael Short |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 1722 |