WEB Microstructure – Mechanical property relationship in pristine and aged forsterite as a new support material for SOFCsWednesday (01.01.2020) 00:45 - 01:00 Part of:
Costs and lifetime are two of the key issues that still hinder a broad market penetration of solid oxide fuel cells (SOFC). Thus, one approach in R&D is to enable less expensive materials - such as forsterite due to its easy manufacturability, chemical stability, linear thermal expansion coefficient and low costs[4,5]. A recent study on the selection of cathode materials for forsterite-supported SOFC focuses on the reactivity of different cathode materials with forsterite and electrocatalytic performance of the cell . However, the effect of high temperatures on the characteristics of forsterite (microstructure, phase composition, mechanical properties) has not yet been investigated in detail. Therefore, in this study, the behavior of forsterite under SOFC operating conditions was examined with particular attention to the effect of temperature and humidity on the microstructure and the mechanical properties.
As a result, stationary thermal aging leads no significant change in the hardness, while autoclave aging results in a slight decrease compared to the pristine state. At the same time, we observed a slight increase in fracture toughness and characteristic strength. In contrast, cyclic thermal aging causes a significant drop in the mechanical strength. XRD, SEM, STEM, and EDX analysis show the presence of secondary phases that exist either as a single grain through the matrix or in an agglomerate form. Apart from that, abnormal grain growth (AGG) was observed at the fracture origin and identified as one of the main reasons for the comparably poor mechanical properties. In the presentation, correlations of the results will be deduced, and the effect of different aging conditions will be evaluated. Besides, the impact of the secondary phases on the mechanical properties and the formation of the AGG will be discussed critically.
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