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Training at Stockholm University (2008 02 07 - 02 27) Martynas Lelis.

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Presentation on theme: "Training at Stockholm University (2008 02 07 - 02 27) Martynas Lelis."— Presentation transcript:

1 Training at Stockholm University ( ) Martynas Lelis

2 Contents  Reminders about last results  Objectives and tasks of the current visit  Measurements at SU Equipment Results  Discussions

3 Reminders about last results  In latter years in LEI there were experiments of formation of Mg 2 Ni alloys and their hydrogenation to Mg 2 NiH 4  There are three phases of Mg 2 NiH 4 – LT1, LT2 (with microtwining) and HT  At ~235° C LT transforms to HT

4 Reminders about last results  XRD – shows pseudo cubic structure related to structure of HT phase  DSC – no phase change on first run  TEM – cubic with impurities  BG – band gap of about 2.2 eV

5 Objectives and tasks  Objective To acquire new skills and better understanding in analyzing and characterization of hydrogen storage materials

6 Objectives and tasks  Tasks To learn the working principles of FT-IR spectrometer and to measure our Mg 2 NiH 4 samples prepared on CaF 2 To prepare fresh powder samples of LT1 and LT2 Mg 2 NiH 4 and to measure band gap in reflectance mode

7 Objectives and tasks  Tasks To adjust custom made glass tube hydrogenation cell for our thin film samples and to make qualitative estimation of hydrogenation kinetics as well as chromatic properties

8 Measurements at SU - equipment  An FTIR (Fourier Transform InfraRed) is a method of obtaining infrared spectra by first collecting an interferogram of a sample signal using an interferometer, then performing a Fourier Transform on the interferogram to obtain the spectrum.

9 Measurements at SU - equipment  The FTIR is based on a Michelson Interferometer, that consists of, at least a beam splitter and two mirrors. This instrument produces interference between two beams of light waves propagated through two separate optical path lengths.

10 Measurements at SU - equipment

11  Scheme of the hydrogenation tube

12 Results

13 Measurements at SU – results Metallic Mg 2 Ni film was put in a transparent quartz tube under 500 kPa H 2 pressure and heated it up. Just after 2 min the film changed its colour to dark brown loosing its reflectivity (as the temperature reached 353 K). After 4-5 min (temperature 433 K) the film had become orange and transparent indicating formation of the hydride. Upon further heating (to 573 K) it remained transparent but got a deeper reddish colour. Upon cooling down to room temperature the orange colour returned.

14 Measurements at SU – results (FT-IR)

15 Measurements at SU - results Ni-H

16 Measurements at SU - results Air elements Ni-H

17 Measurements at SU - results Ni-H Air elements C-H

18 Measurements at SU - results Ni-H Air elements C-HO-H

19 Measurements at SU – results (BG)

20

21 Discussions

22 Discussions - XRD

23 Thin film: a=6.440 Å Scratched powders: a= Å Powder material: Å

24 Discussions - TEM D. Noréus, L. Kihlborg, J. Less-Comm. Met. 123 (1986) 233

25 Discussions - TEM

26 Discussions – DSC - powder

27 Discussions – DSC – thin film

28 Discussions – FT-IR

29 Discussion – Band gap

30

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32 Your suggestion and comments


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