Etude par Sonde Atomique Tomographique de la formation de nano ...

tel-00751814, version 1 - 14 Nov 2012
Chapter 2. Materials, experimental and simulation techniques
o Two types of nanoparticles have been modelled: with lower evaporation field
E A � A � � 0.
7 and with higher evaporation field E A � A � � 1.
4 , where EA and EFe are field of
E
E
Fe
Table 2.8. Field of evaporation of Fe, Cr, Y and Ti [16].
Elements Fe Cr Ti Y
Evaporation field: Ei (V.nm -1 ) 33 29 26 23.5
Relative evaporation field: Ei 1 0.8 0.8 0.7
evaporation of Fe and element A respectively. The values � (0.7 or 1.4) correspond to
A
nanoparticles in ODS or nanoparticles in NDS with atomic density inside nanoparticles close
to the experimentally observed ones (Figure 2.16).
100 (a) (b)
90
Concentration (at,%)
Density
80
70
60
50
40
30
20
10
0
0 0,5 1 1,5 2 2,5 3 3,5 4 4,5 5 5,5 6 6,5 7 7,5 8
3,5
3
2,5
2
1,5
1
0,5
Distance (nm)
Fe(M)
Shell
Core
0
0 0,5 1 1,5 2 2,5 3 3,5 4 4,5 5 5,5 6 6,5 7 7,5 8
Distance (nm)
Figure 2.16. Profiles through simulated nanopartilces with core-shell structure
Rcore=2.0 nm, showing concentration (above) and relative atomic density (below) for (a) low
field with� � 0.
7 and (b) high field with � �1.
4 particles. Profiles build in evaporation
A
A
direction with sampling box 1.0×1.0×1.0 nm 3 .
Concentration (at,%)
Density
100
90
80
70
60
50
40
30
20
10
Fe
0
0 0,5 1 1,5 2 2,5 3 3,5 4 4,5 5 5,5 6 6,5 7 7,5 8 8,5 9 9,5 10
1,4
1,2
1
0,8
0,6
0,4
0,2
Distance (nm)
Fe(M)
Shell
Core
0
0 0,5 1 1,5 2 2,5 3 3,5 4 4,5 5 5,5 6 6,5 7 7,5 8 8,5 9 9,5
Distance (nm)
74