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1

Porous Composite for Bipolar Plate in Low Emission Hydrogen Fuel Cells

Wlodarczyk R.

Journal of Ecological Engineering

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2018

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Vol. 19, nr 1

225--232

EN

The paper presents the results of graphite-stainless steel composites for the bipolar plates in low-temperature fuel cells. The sinters were performed by powder metallurgy technology. The influence of technological parameters, especially molding pressure were examined. Following the requirements formulated by the DOE concerning the parameters of the materials, it indicated by the value of the parameters. The density, flowability, particle size of graphite and stainless steel powders have been evaluated. Composites have been tested by microstructure and phase analysis, properties of strength, functional properties: wettability, porosity, roughness. The special attention was paid to the analysis of corrosion resistance obtained sinters and influence of technological parameters on the corrosion. Corrosion tests were carried out under conditions simulating the environment of the fuel cell under anode and cathode conditions. The effect of pH solution during working of the cell on corrosion resistance of composites have been evaluated. Contact resistance depends on roughness of sinters. Low ICR determined high contact area GDL-BP and high electrical conductivity on the contact surface. The ICR in anode conditions after corrosion tests are not change significantly; composite materials can be used for materials for BP in terms of H2.

2

Recykling kompozytów stop AK20-grafit syntetyczny

Mitko M., Tomczyński S.

Kompozyty

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2001

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R. 1, nr 2

188-190

PL

Kompozyty metalowe typu stop Al-cząstki grafitu są szczególnie przydatne do pracy w warunkach tarcia suchego, gdy smarowanie jest utrudnione lub niemożliwe. Cząstki grafitu w kompozycie znacznie zmniejszają zużycie ścierne oraz współczynnik tarcia suchego [1-3]. Wzrost produkcji kompozytów wymaga opracowania technologii powtórnego wykorzystania odpadów produkcyjnych oraz zużytych części i odlewów. Odpady te można ponownie wykorzystać jako złom wsadowy do nowej produkcji lub po oddzieleniu cząstek od osnowy metalowej w celu powtórnego wykorzystania metalu [4-6]. W artykule przedstawiono wstępne wyniki badań nad wykorzystaniem złomu kompozytu o osnowie stopu AK20 z dużą ilością cząstki grafitu poprzez jego powtórny przetop, rozcieńczenie stopem metalowym oraz odzysk stopu osnowy poprzez usuniecie cząstek grafitu drogą rafinacji.

EN

The paper presents the results of investigations concerning the re-using of composite scrap. Examinations covered the remelting of the composite, its diluting with the matrix alloy and recovery of the matrix alloy by removing graphite particles by means of refining process. Investigated material has been AK20-alloy/synthetic-graphite-particles composite produced by squeeze casting (Fig. 1). The composite has been remelted in the temperature of 750°C and, after casting specimens for examinations (Fig. 2), diluted with pure matrix alloy in 1:1 proportion (Fig. 3). Next group of specimens has been cast and the rest of the diluted alloy has been refined with RafGlinEko refining agent, suitable specimens being cast once again (Fig. 4). The structure of examined composites is composed of graphite particles and the B-phase, both arranged within a+B eutectic. In the cases of remelted or diluted composite there have been found spherical inclusions, the so-called secondary agglomerates, which are gas bubbles partially filled with graphite particles and other impurities (Figs 2, 3). The stucture of the composite after refining does not differ from the structure of the AK20 alloy, except for few separate graphite particles one can observe within some areas of the microsection (Fig. 4). Results of mechanical and tribological examinations have been gathered in Table 1. The tensile strength decreases with increasing quantity of graphite particles in the composite, and remelting reduces it by further 20% in relation to the strength of the composite before remelting. As a result of combined remelting and diluting there has been obtained a composite of similar tribological properties as a composite before remelting containing the same particle fraction. The properties of the alloy after final refining do not differ practically from the properties of the matrix, i.e. the AK20 alloy. The performed investigations has proved the usefulness of the employed methods of recycling composite scrap containing graphite particles for production of composite casting with the required particle fraction and for recovery of the matrix alloy.

3

Exfoliation of CrO3-GIC as a route to novel graphite composites

Skowroński J. M., Walkowiak M.

Karbo

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2001

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Nr 11

400-403

EN

Intercalation compound of graphite with chromium trioxide was used as a precursor for obtaining of a novel type of graphite composites. Heating it at temperature of up to 800°C in air resulted in obtaining of composite material of expanded graphite/Cr(2)O(3) type. Whereas further treatment of this composite at the temperature of 1000°C in the stream of hydrogen with argon lead the transformation of Cr(2)O(3) into chromium carbide and origination of a composite of expanded graphite/Cr(3)C(2) type.

PL

Interkalacyjny związek grafitu z trójtlenkiem chromu został użyty jako prekursor w procesie otrzymywania nowego typu kompozytów grafitowych. Ogrzewając go do temperatury 800°C w powietrzu otrzymano materiał kompozytowy typu ekspandowany grafit/Cr(2)O(3), natomiast dalsze ogrzewanie tego kompozytu w temperaturze 1000°C w strumieniu wodoru z argonem spowodowało redukcję Cr(2)O(3) do węglika chromu i powstanie kompozytu typu ekspandowany grafit/Cr(3)C(2).