Frost induced damages within porous materials - from concrete technology to fuel cells technique
| Autor: | Stanislav Gorelkov, Jens Wartmann, Angelika Heinzel, Susanne Palecki |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
Materials science
Renewable Energy Sustainability and the Environment Delamination Membrane electrode assembly Energy Engineering and Power Technology 02 engineering and technology 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences Durability 0104 chemical sciences Pore water pressure Frost (temperature) Geotechnical engineering Electrical and Electronic Engineering Physical and Theoretical Chemistry Composite material 0210 nano-technology Porous medium Water content Shrinkage |
| Zdroj: | Journal of Power Sources. 372:204-211 |
| ISSN: | 0378-7753 |
| Popis: | Porous media like concrete or layers of membrane electrode assemblies (MEA) within fuel cells are affected by a cyclic frost exposure due to different damage mechanisms which could lead to essential degradation of the material. In general, frost damages can only occur in case of a specific material moisture content. In fuel cells, residual water is generally available after shut down inside the membrane i.e. the gas diffusion layer (GDL). During subsequent freezing, this could cause various damage phenomena such as frost heaves and delamination effects of the membrane electrode assembly, which depends on the location of pore water and on the pore structure itself. Porous materials possess a pore structure that could range over several orders of magnitudes with different properties and freezing behaviour of the pore water. Latter can be divided into macroscopic, structured and pre-structured water, influenced by surface interactions. Therefore below 0 °C different water modifications can coexist in a wide temperature range, so that during frost exposure a high amount of unfrozen and moveable water inside the pore system is still available. This induces transport mechanisms and shrinkage effects. The physical basics are similar for porous media. While the freezing behaviour of concrete has been studied over decades of years, in order to enhance the durability, the know-how about the influence of a frost attack on fuel cell systems is not fully understood to date. On the basis of frost damage models for concrete structures, an approach to describe the impact of cyclic freezing and thawing on membrane electrode assemblies has been developed within this research work. Major aim is beyond a better understanding of the frost induced mechanisms, the standardization of a suitable test procedure for the assessment of different MEA materials under such kind of attack. Within this contribution first results will be introduced. |
| Databáze: | OpenAIRE |
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