Upload
gannon-barling
View
222
Download
0
Embed Size (px)
Citation preview
Training at Stockholm University (2007 09 12 - 10 02)
Martynas Lelis
Contents
Background Objectives and tasks of the visit Measurements at SU
Equipment Results
Discussions
Background
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
Background
Initial investigation of Mg2NiH4 samples prepared at LEI seems to be pseudo cubic HT phase (even at room temperatures)
Moreover, it exhibits unusual stability
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
Differential scanning colorimeter (DSC) and spectrophotometer
to prepare and to measure samples from LEI
to analyze the results and to make conclusions
Measurements at SU - equipment
Differential scanning calorimetry or DSC is a thermoanalytical technique in which the difference in the amount of heat required to increase the temperature of a sample and reference are measured as a function of temperature.
Measurements at SU - equipment
The basic principle underlying this technique is that, when the sample undergoes a physical transformation such as phase transitions, more (or less) heat will need to flow to it than the reference to maintain both at the same temperature.
Measurements at SU - equipment
Perkin Elmer Pyris 1
It can be used to find Heat Flow, Melting Temperature, Phase Transition Temperature etc.
Typical sample weights are 5-10mg
Measurements at SU - results
500 510 520 530 540
Second heating cycle
First heating cycle
Hea
t fl
ow
, arb
. un
t.
Temperature, K
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
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
Discussion – Band gap
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
Discussion - model
MgO
Thin film
Powder
Mg2Ni zones
Mg zones
Conclusions
1. During the visit to Stockholm university new analytical techniques were successfully learned and employed for sample characterization
2. Measurement of thin film samples has given some proving evidence (not complete) for the existence of pseudo cubic HT phase of Mg2NiH4
Your suggestion and comments