Training at Stockholm University (2008 02 07 - 02 27) Martynas Lelis
Training at Stockholm University (2008 02 07 - 02 27)
Martynas Lelis
Contents
Reminders about last results
Objectives and tasks of the current visit
Measurements at SU Equipment
Results
Discussions
Reminders about last results
In latter years in LEI there were experiments of formation of Mg2Ni alloys and their hydrogenation to Mg2NiH4
There are three phases of Mg2NiH4 – LT1, LT2 (with microtwining) and HT
At ~235° C LT transforms to HT
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
Objectives and tasks
Objective To acquire new skills and better
understanding in analyzing and characterization of hydrogen storage materials
Objectives and tasks
Tasks To learn the working principles of FT-IR
spectrometer and to measure our Mg2NiH4 samples prepared on CaF2
To prepare fresh powder samples of LT1 and LT2 Mg2NiH4 and to measure band gap in reflectance mode
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
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.
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.
Measurements at SU - equipment
Measurements at SU - equipment
Scheme of the hydrogenation tube
GASThermocouple
Sample
Results
Measurements at SU – results• Metallic Mg2Ni film was put in a transparent quartz tube under 500 kPa H2 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.
Measurements at SU – results (FT-IR)
80012001600200024002800320036004000wavelengh, cm-1
inte
nsi
ty, a
rb. u
nt.
DNQ417VH Clear yellowDnQ417VHspotsDNQ418VHgreenishNQ418VHBlackspots
Measurements at SU - results
80012001600200024002800320036004000wavelengh, cm-1
inte
nsi
ty, a
rb. u
nt.
DNQ417VH Clear yellowDnQ417VHspotsDNQ418VHgreenishNQ418VHBlackspots
Ni-H
Measurements at SU - results
80012001600200024002800320036004000wavelengh, cm-1
inte
nsi
ty, a
rb. u
nt.
DNQ417VH Clear yellowDnQ417VHspotsDNQ418VHgreenishNQ418VHBlackspots
Air elementsNi-H
Measurements at SU - results
80012001600200024002800320036004000wavelengh, cm-1
inte
nsi
ty, a
rb. u
nt.
DNQ417VH Clear yellowDnQ417VHspotsDNQ418VHgreenishNQ418VHBlackspots
Ni-HAir elements
C-H
Measurements at SU - results
80012001600200024002800320036004000wavelengh, cm-1
inte
nsi
ty, a
rb. u
nt.
DNQ417VH Clear yellowDnQ417VHspotsDNQ418VHgreenishNQ418VHBlackspots
Ni-HAir elements
C-HO-H
Measurements at SU – results (BG)
0,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
4,0
4,5
0,00,51,01,52,02,53,0
Energy (eV)
Measurements at SU – results (BG)
-0,2
0,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
1,51,71,92,12,32,52,72,93,1
Energy (eV)
Abso
rban
ce422Cloud422Clear417Clear411Cloud411Wcloud411Clear
Discussions
Discussions - XRD
Discussions - XRD
20 30 40 50 60 70
b)
a)(4
00
)(31
1)
(22
0)
(11
1)
(00
2)
(00
6)
(20
3)
(20
0)
(11
2)
(00
3)
Inte
nsi
ty, a
rb. u
nt.
2, degrees
c - Mg2NiH
4
h - Mg2Ni
h - MgThin film:
• a=6.440 Å
Scratched powders:
• a=6.507998 Å
Powder material:
• 6.5295 Å
Discussions - TEM
D. Noréus, L. Kihlborg, J. Less-Comm. Met. 123 (1986) 233
Discussions - TEM
Discussions – DSC - powder
Discussions – DSC – thin film
500 510 520 530 540
Second heating cycle
First heating cycle
Hea
t fl
ow
, arb
. un
t.
Temperature, K
Discussions – FT-IR
80012001600200024002800320036004000wavelengh, cm-1
inte
nsi
ty, a
rb. u
nt.
DNQ417VH Clear yellowDnQ417VHspotsDNQ418VHgreenishNQ418VHBlackspots
Discussion – Band gap
Discussion – Band gap
-0,2
0,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
1,51,71,92,12,32,52,72,93,1
Energy (eV)
Abso
rban
ce422Cloud422Clear417Clear411Cloud411Wcloud411Clear
0,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
4,0
4,5
0,00,51,01,52,02,53,0
Energy (eV)
Discussion – Band gap
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