文档介绍：Pr. J. RS/CEMES and UPS
Centre d’Elaboration de Matériaux
et d’Etudes Structurales (France)
Université Paul Sabatier
Toulouse (France)
Structure, chemical order and ism of
binary 3d/4d nanoparticles :
Experiment and theory
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INTRODUCTION
EXPERIMENTAL RESULTS
MODELLING
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ic particles for recording applications
3d/4d et 3d/5d Alloys
Stability: High ic anisotropy 4d,5d element
Example: CoxRh1-x nanoparticles
Sensitivity: High ic moments per atom 3d elements
High density: Small size nanoparticles
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Cobalt : hcp (T<750K), fcc (T>750K)
Rhodium : fcc
fcc
hcp
Alloy: hcp (x<50,5%), fcc (x>50,5%)
Disordered solid solution
W. Koster, Z. Metallkunde, 43 (1952)
Bulk crystals: Co, Rh and Co1-xRhx
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(fcc)
Octahedron:
1st and 2d neighbours
distances
ABCABC…
(111) stacking
A
B
C
A
Tetrahedron:
1st neighbours distance
Close packed structures :
face centered cubic (fcc) and pact (hcp)
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(fcc)
Close packed structures :
face centered cubic (fcc) and pact (hcp)
In between two essive (111) planes (AB) or (BC) or (CA)
Exist also in the other closed packed hcp structure (ABAB….)
Tetrahedron and octahedron are the building blocks of close-packed structures
1st and 2d neighbours distances are characteristic of close-packed structures
Tetrahedron:
1st neighbours distance
Octahedron:
1st and 2d neighbours
distances
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Close-packed nanoparticles
Based on
tetrahedrons
only
non periodic-based polytetrahedrons
the 2d neighbours
distance is absent
Based on
tetrahedrons
and octahedrons
1st and 2d neighbours
distances are present
periodic or non periodic-based nanoparticles
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INTRODUCTION
EXPERIMENTAL RESULTS
MODELLING
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Chemical techniques in mild conditions (T=300 - 400K)
Co-position by H2 of the anometallic precursors in THF
Size and dispersion stabilized by polymer (PVP), or ligand (HDA)
Pure Co, M, Co3M1 Co1M1, Co1M3 (close packed metals and alloys in cristalline state)
Synthesis
Experiments
Structure
TEM, HREM
Wide angle x-ray sc