Hydrogen storage in magnesium based thin films

Download
index.pdf
2010
Akyıldız, Hasan
Show full item record
210
views
98
downloads
A study was carried out for the production of Mg-based thin films which can absorb and desorb hydrogen near ambient conditions, with fast kinetics. For this purpose, two deposition units were constructed; one high vacuum (HV) and the other ultra high vacuum (UHV) deposition system. The HV system was based on a pyrex bell jar and had two independent evaporation sources. The unit was used to deposit films of Mg, Mg capped with Pd and Au-Pd as well as Mg-Cu both in co-deposited and multilayered form within a thickness range of 0.4 to 1.5 μm. The films were crystalline with columnar grains having some degree of preferred orientation. In terms of hydrogen storage properties, Mg/Pd system yielded the most favorable results. These films could desorb hydrogen at temperatures not greater than 473 K. The study on crystalline thin films has further shown that there is a narrow temperature window for useful hydrogenation of thin films, the upper limit of which is determined by the intermetallic formation. The UHV deposition system had four independent evaporation sources and incorporated substrate cooling by circulating cooled nitrogen gas through the substrate holder. Thin films of Mg-Cu were produced in this unit via co-evaporation technique to provide concentrations of 5, 10 and 15 at. % Cu. The films were 250-300 nm thick, capped with a thin layer of Pd, i.e. 5-25 nm. The deposition was yielded nanocrystalline or amorphous Mg-Cu thin films depending on the substrate temperature. At 298 K, the films were crystalline, the structure being refined with the increase in Cu content. At 223 K, the films were amorphous, except for Mg:Cu=95:5. The hydrogen sorption of the films was followed by resistance measurements, with the samples heated isochronally, initially under hydrogen and then under vacuum. The resistance data have shown that hydrogen sorption behaviour of thin films was improved by size refinement, and further by amorphization. Among the films deposited, amorphous Mg:Cu=85:15 alloy could absorb hydrogen at room temperature and could desorb it at 223 K (50 ºC), with fast kinetics.
Hydrogen, Hydrogen
http://etd.lib.metu.edu.tr/upload/12612652/index.pdf
https://hdl.handle.net/11511/19994
Graduate School of Natural and Applied Sciences, Thesis

Suggestions

Hydrogen absorption in magnesium based crystalline thin films
Akyildiz, Hasan; Ozenbas, Macit; Öztürk, Tayfur (2006-08-01)
A study is carried out for hydrogenation of Mg based thin films produced via thermal evaporation. Films produced were pure Mg, Mg capped with Au-Pd, Mg-Cu co-deposited and Mg-Cu multilayered. The films under the experimental conditions employed were crystalline with columnar grains with some degree of preferred orientation. In multi-component systems, the films in the as-deposited state were made of individual elements, but upon hydrogenation at temperatures greater than 473K, the elements react with each o...
Direct synthesis of hydrogen storage alloys from their oxides
Tan, Serdar; Öztürk, Tayfur; Aydınol, Mehmet Kadri; Department of Metallurgical and Materials Engineering (2011)
The aim of this study is the synthesis of hydrogen storage compounds by electrodeoxidation technique which offers an inexpensive and rapid route to synthesize compounds from oxide mixtures. Within the scope of this study, two hydrogen storage compounds, FeTi and Mg2Ni, are aimed to be produced by this technique. In the first part, effect of sintering conditions on synthesis of FeTi was studied. For this purpose, oxide pellets made out of Fe2O3-TiO2 powders were sintered at temperatures between 900 °C – 1300...
Hydrogen production by different strains of Rhodobacter sphaeroides
Gündüz, Ufuk; Yucel, M; Turker, L; Eroglu, L (2000-06-15)
Utilisation of solar energy by photosynthetic microorganisms for H-2 production attracts much interest due to unlimited supply of energy. It is important to identify the most effective strain in terms of hydrogen production for the feasibility of the process. Four different strains of Rhodobacter sp. were grown in a water-jacketed cylindrical glass-column photobioreactor under anaerobic conditions. Growth characteristics and hydrogen production rates were determined. Comparison between strains of Rhodobacte...
Phototrophic hydrogen production by agar-immobilized Rhodobacter capsulatus
Elkahlout, Kamal E. M.; Yücel, Ayşe Meral; Eroğlu, İnci; Department of Biotechnology (2011)
photosynthetic bacteria is attractive field as production is fueled by solar energy. Hydrogen production potential of two photosynthetic bacteria R.capsulatus (DSM1710 wild type and R.capsulatus YO3 Hup- uptake hydrogenase deleted mutant strain) were examined in agar immobilized systems. In the present work agar and glutamate concentrations were optimized for immobilization of bacteria while feeding bacteria with 40/2-4 mM acetate/ glutamate. Immobilized bacteria produced hydrogen for 420-1428 hours coverin...
Hydrogen sorption in crystalline and amorphous Mg-Cu thin films
Akyildiz, Hasan; Öztürk, Tayfur (2010-03-04)
A study was carried out to examine the hydrogenation behavior of 300 nm, Pd-capped, Mg-Cu thin films with Cu contents of 5, 10 and 15 at.%. The films were produced via thermal evaporation of Mg and Cu co-deposited onto glass substrates at two different temperatures: 298 and 223 K. The samples produced at 298 K were all crystalline, the structure being refined with increase in the Cu content. The films deposited at 223 K developed structures that were either refined, i.e. Mg(95)Cu(5); or amorphous, i.e. Mg(9...
Citation Formats
H. Akyıldız, “Hydrogen storage in magnesium based thin films,” Ph.D. - Doctoral Program, Middle East Technical University, 2010.
METU IIS - Integrated Information Service open@metu.edu.tr