Date

2022-1-25

Author

Köse, Mehmet Mert

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A study was carried out into dense metallic membranes for hydrogen separation. Two palladium-based system were characterized Pd-Mn-Ag and Pd-Co-Ni. Membranes were produced via sputter deposition in combinatorial geometry. For this purpose, sputter targets were arranged in triangular manner, and there were total of 21 substrates just above the targets. Membranes were screened via resistivity measurements under argon and hydrogen carried out up to 450 oC. A reactivity index defined as resistivity under hydrogen over that in argon was used as an index of suitability of the thin film membranes for hydrogen separation. The study has shown that Pd-Co-Ni system, except for small region close to Co corner, the rest of the ternary field had f.c.c. structure. Unfortunately, these membranes showed no reaction with hydrogen under 1bar of hydrogen pressure up to 450 oC and therefore they were considered unsuitable as separation membranes. Pd-Mn-Ag ternary system was more fruitful. Similarly, the system had a wide compositional field with f.c.c. structure. These were on the side of Ag-Pd line and moreover, considerable fractions of these membranes were reacting with hydrogen implying that they may be suitable as separation membrane. Based on their reactivity curve, and palladium content Pd35Mn13Ag52, Pd56Mn13Ag31 and Pd62Mn18Ag20 were selected as candidates for hydrogen separation. Selected compositions were then sputter deposited on de-alloyed brass as support material for permeability measurements. Dealloying was carried out at 460 oC for 4 hours under vacuum (10-6 mbar). This has yielded copper substrate with pores of approximately 1 m in size. Thin film membranes of 5 µm thick were deposited on the nanoporous copper. Unfortunately, the measurements were not possible as the coated assembly were not argon tight. A thicker deposition 7 micron thick with substrate heating to 350oC also failed as these assembly was not structurally stable during testing.

Subject Keywords

Hydrogen Separation, Dense Metallic Membranes, Palladium Alloys, Pd-Mn-Ag, Pd-Co-Ni, Dealloying

URI

https://hdl.handle.net/11511/96078

Collections

Graduate School of Natural and Applied Sciences, Thesis