Abstract
Carbon materials have become increasingly diverse, finding applications in high-temperature and high-radiation environments. Glassy carbon, an allotrope known for its exceptional chemical inertness and desirable mechanical properties. However, understanding neutron irradiation effects in glassy carbon has proven challenging, primarily because of its unique nanopore structure. This study presents a highly detailed microstructural characterization investigation of neutron-induced changes in glassy carbon, revealing how changes in nanopore structure and crystallinity impact the irradiation-induced shrinkage. Aberration-corrected scanning transmission electron microscopy (STEM) reveals pore closure that leads to material densification in the irradiated samples. Dimensional analysis combined with comparison to historical data suggest significant length shrinkage to occur. Neutron and in situ electron irradiation experiments suggest that glassy carbon transforms into so-called carbon onions, supporting the concept of shrinkage saturation. Investigating irradiation temperature effects using STEM, electron energy loss spectroscopy, x-ray diffraction, and Raman spectroscopy revealed partial amorphization at 210 °C–230 °C and preserved order in glassy carbon at 860 °C, coinciding with pore closure. Thermal property measurements were also conducted to assess the effects of densification and other changes in the atomic structure of glassy carbon. The results of this study have broad implications in the deployment of glassy carbon to nuclear environments, based around the observed changes in the thermal properties, and demonstrates the operational window for the onset of densification.
| Original language | English |
|---|---|
| Article number | 120441 |
| Journal | Acta Materialia |
| Volume | 281 |
| DOIs | |
| State | Published - Dec 1 2024 |
Funding
A portion of this work was supported by the US Department of Energy (DOE) Office of Nuclear Energy under DOE Idaho Operations Office Contract DE-AC07- 051D14517 as part of a Nuclear Science User Facilities experiment, \u201CMicrostructural characterization of neutron irradiated C\u2013C composites\u201D (23-1908). A portion of this research used the resources of the Low Activation Materials Development and Analysis Laboratory, a DOE Office of Science research facility operated by the Oak Ridge National Laboratory (ORNL). Neutron irradiation was supported by the DOE Office of Fusion Energy Sciences under contract DE-AC05-00OR22725 and by IMR Tohoku University under contract NFE-13-04416 with UT-Battelle, LLC. The post-irradiation examination was also partially supported by the DOE Office of Fusion Energy Sciences, Fusion Materials Program. A portion of this research used resources at the High Flux Isotope Reactor, a DOE Office of Science User Facility operated by ORNL. STEM and EELS research was supported by ORNL's Center for Nanophase Materials Sciences, which is a DOE Office of Science user facility. The authors acknowledge ORNL's Materials and Chemistry Group in the Nuclear Nonproliferation Division for use of the Raman spectrometer. The authors also acknowledge Shawn S. Reeves for her assistance with sample preparation and Stephanie M. Curlin for the thermal property measurements. The authors would like to thank Hughie Spinoza for his valuable comments and discussion.
| Funders | Funder number |
|---|---|
| ORNL's Center for Nanophase Materials Sciences | |
| Oak Ridge National Laboratory | |
| U.S. Department of Energy | |
| Office of Science | |
| Office of Nuclear Energy | 23-1908, DE-AC07- 051D14517 |
| Fusion Energy Sciences | DE-AC05-00OR22725 |
| IMR Tohoku University | NFE-13-04416 |
Keywords
- Glassy carbon
- Irradiation effects
- Microstructural characterization
- Nuclear materials