Data di Pubblicazione:
2019
Abstract:
Element clustering and structural features of liquid lead-bismuth eutectic (LBE) alloy
have been investigated up to 720 °C by means of high temperature X-ray diffraction (HT-XRD),
X-ray Photoemission Spectroscopy (XPS) and Scanning Photoemission Microscopy (SPEM) at the
Elettra synchrotron in Trieste. The short-range order in liquid metal after melting corresponds
to the cuboctahedral atomic arrangement and progressively evolves towards the icosahedral one
as temperature increases. Such process, that involve a negative expansion of the alloy, is mainly
connected to the reduction of atom distance in Pb-Pb pairs which takes place from 350 °C to 520 °C.
On an atomic scale, it is observed a change of the relative number of Bi-Bi, Pb-Pb, and Pb-Bi pairs.
The Pb-Bi pairs are detected only at a temperature above ~350 °C, and its fraction progressively
increases, giving rise to a more homogeneous distribution of the elements. SPEM results showed
evidence that the process of chemical homogenization on an atomic scale is preceded and accompanied
by homogenization on micro-scale. Clusters rich of Bi and Pb, which are observed after melting,
progressively dissolve as temperature increases: Only a few residuals remain at 350 °C, and no more
clusters are detected a 520 °C.
have been investigated up to 720 °C by means of high temperature X-ray diffraction (HT-XRD),
X-ray Photoemission Spectroscopy (XPS) and Scanning Photoemission Microscopy (SPEM) at the
Elettra synchrotron in Trieste. The short-range order in liquid metal after melting corresponds
to the cuboctahedral atomic arrangement and progressively evolves towards the icosahedral one
as temperature increases. Such process, that involve a negative expansion of the alloy, is mainly
connected to the reduction of atom distance in Pb-Pb pairs which takes place from 350 °C to 520 °C.
On an atomic scale, it is observed a change of the relative number of Bi-Bi, Pb-Pb, and Pb-Bi pairs.
The Pb-Bi pairs are detected only at a temperature above ~350 °C, and its fraction progressively
increases, giving rise to a more homogeneous distribution of the elements. SPEM results showed
evidence that the process of chemical homogenization on an atomic scale is preceded and accompanied
by homogenization on micro-scale. Clusters rich of Bi and Pb, which are observed after melting,
progressively dissolve as temperature increases: Only a few residuals remain at 350 °C, and no more
clusters are detected a 520 °C.
Tipologia CRIS:
01.01 Articolo in rivista
Keywords:
liguid Pb-Bi eutectic alloy; chemical homogeneity; short range order; XPS; SPEM; HT-XRD
Elenco autori:
Kaciulis, Saulius; Mezzi, Alessio
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