A positron annihilation spectroscopy analysis method to obtain a quantitative determination of the chemical composition around defects inside nanoparticles is presented here. This methodology is applied to Al–Cu–Mg alloys to study the rapid hardening phenomena associated with solute-vacancy aggregation. Coincidence Doppler Broadening (CDB) and lifetime spectroscopy measurements of reference samples of pure elements with and without defects were analyzed to give quantitative information of the average chemical environment around vacancies, i.e. the atomic fraction of the first neighbors of these defects, in the alloys studied. The accuracy and reproducibility of the methodology is confirmed not only by good fits to the experimental data but, in most cases, by the consistency between the mean lifetime values predicted, using the CDB estimation, and the mean lifetime values independently measured. Discrepancies in the methodology are expected when there is poor CDB contrast between elements, i.e. having similar electronic structure (for example, Al and Mg). The criterion for establishing the statistical accuracy of the separation of elements in these special cases is discussed. The methodology can be applied not only to study homogeneous materials as metallic alloys, but also to study the depth profile in thin films.

Atomic fraction around defects associated with nanoparticles in Al–Cu–Mg alloys

FERRAGUT, RAFAEL OMAR
2012-01-01

Abstract

A positron annihilation spectroscopy analysis method to obtain a quantitative determination of the chemical composition around defects inside nanoparticles is presented here. This methodology is applied to Al–Cu–Mg alloys to study the rapid hardening phenomena associated with solute-vacancy aggregation. Coincidence Doppler Broadening (CDB) and lifetime spectroscopy measurements of reference samples of pure elements with and without defects were analyzed to give quantitative information of the average chemical environment around vacancies, i.e. the atomic fraction of the first neighbors of these defects, in the alloys studied. The accuracy and reproducibility of the methodology is confirmed not only by good fits to the experimental data but, in most cases, by the consistency between the mean lifetime values predicted, using the CDB estimation, and the mean lifetime values independently measured. Discrepancies in the methodology are expected when there is poor CDB contrast between elements, i.e. having similar electronic structure (for example, Al and Mg). The criterion for establishing the statistical accuracy of the separation of elements in these special cases is discussed. The methodology can be applied not only to study homogeneous materials as metallic alloys, but also to study the depth profile in thin films.
2012
File in questo prodotto:
File Dimensione Formato  
Ferragut_PhysicaB_2012.pdf

Accesso riservato

: Post-Print (DRAFT o Author’s Accepted Manuscript-AAM)
Dimensione 567.9 kB
Formato Adobe PDF
567.9 kB Adobe PDF   Visualizza/Apri

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11311/679770
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 9
  • ???jsp.display-item.citation.isi??? 8
social impact