Speaker
Monika Vilemova
(Materials Engineering)
Description
Pure tungsten is considered as the most suitable plasma facing material for the reactor first wall. However, number of studies points out serious drawbacks related to tungsten mechanical properties that negatively affect lifetime of first wall components. Serious risk for the divertor comes from abnormal events, such as disruptions, vertical displacement events (VDEs) and edge localized modes (ELMs). The transient loading can deposit large energies on the divertor surface (power density ~GW/m–2–2) within a period of few ms. Thus, most serious concerns about tungsten are related to the thermally induced grain growth. The abovementioned disadvantages lead to current efforts to develop tungsten with improved properties.
Among the most studied alternative candidates from the family of tungsten with oxide dispersion is W-Y2O3. Various concentrations starting with values as low as 0,1% up to 5 wt% of Y2O3 and related mechanical properties are studied. Nevertheless, it seems no attention is given to the characterization of the Y2O3 phase in the prepared composites despite the significant density and microstructural difference of the different Y2O3 forms. Thus, the phase transition is accompanied by a volume change which might significantly alter properties of the prepared W-Y2O3 composite. Y2O3 is a polymorph that can occur in three basic forms: cubic, monoclinic and hexagonal. Presented study brings description and identification of the condition for phase transitions and structure changes of Y2O3 in W-Y2O3 composite from the production to the application in the future fusion reactor. The phases were characterized by XRD, HRTEM and Raman spectroscopy. The causes of the phase transition are discussed and the range of the phase stability for the different Y2O3 forms is clarified.
Co-author
Monika Vilemova
(Materials Engineering, Institute of Plasma Physics of the CAS, Prague 8, Czech Republic)
