Paper AC+AS+EN-TuA11
The Microstructure of Cerium Hydride Growth Centres
Tuesday, October 29, 2013, 5:20 pm, Room 102 C
| Session: |
Actinides and Rare Earths: The Nuclear Fuel Cycle and Critical Materials |
| Presenter: |
M. Brierley, AWE, UK |
| Authors: |
M. Brierley, AWE, UK
J. Knowles, AWE, UK
N. Montgomery, AWE, UK
M. Preuss, University of Manchester, UK
A. Sherry, University of Manchester, UK
|
| Correspondent: |
Click to Email |
Considerable work has been undertaken into the hydriding of rare earth metals and actinides [1]; specifically into the reaction rate of various hydrides on the surface of these materials [2]. Cerium is a reactive rare-earth metal and quickly forms a semi-protective oxide layer in air. Upon exposure of an oxide-covered sample to hydrogen, hydride is formed as discrete sites on the surface, often termed ‘Growth Centres’, which then grow radially across the surface [3]. In the present study, the emphasis was to investigate the microstructure of the cerium growth centres with the intention of understanding any hydriding nucleation and growth mechanisms which may occur. The samples were prepared to 1 µm finish before being exposed to ultra-pure hydrogen at pressures between 10 mbar and 300 mbar, for sufficient time to have nucleated a number of hydride Growth Centres. Post-test analysis was performed using Secondary Ionisation Mass Spectrometry (SIMS), Scanning Electron Microscopy (SEM) and Optical Microscopy (OM) to determine the microstructure of the hydride growth centres. SIMS confirmed that the Growth Centres were comprised of cerium hydride, and that the hydrogen exists specifically within the features. The morphology of individual hydride Growth Centres was examined using OM and SEM and the data reported demonstrates that the hydride-metal interface has a discrete boundary between two distinct phases; a region of deformed metal surrounds the Growth Centres; the microstructure within the Growth Centres indicates that the microstructure of the parent metal was retained by the hydride product.
References
[1] M. H. Mintz, J. Bloch, Prog. Solid St. Chem. Vol. 16, (1985) 163-194.
[2] K. H. Gayer, W. G. Bos, J. Phys. Chem. Vol. 68, No. 9, (1964) 2569- 2574.
[3] G. W. McGillivray, J. P. Knowles, I. M. Findlay, M. J. Dawes, J. Nucl. Mater. 385 (2009) 212-215.