Title

A possible experimental evidence of solid-liquid pretransitional phenomena

A possible experimental evidence of solid-liquid pretransitional phenomena

Authorship

PATUELLI, C.; TOGNATO, R.

PATUELLI, C.

I am this author

TOGNATO, R.

I am this author

DOI

10.5151/2594-5327-C00235-3648-3655

Downloads

Abstract

Phase transitions often occur together with the so-called pretransitional phenomena. The origin of these phenomena is the appearance of a competing thermodynamic phase inside a host phase. The phenomena become more important near the thermodynamical transition temperature. A number of experiments displaying an abnormal behaviour during freezing and melting may be found in literature. Molecular dynamics as well Monte Carlo methods have been used for treating the solid-liquid phase transition. These computer simulations have clearly shown the coexistence of two kinds of configurations: crystalline and liquid-like structures. Statistical mechanics shows that pretransitions are strictly correlated with fluctuation probabilities in thermal equilibrium systems; in particular smaller are the volumes interested by the fluctuation higher are the pretransition probabilities. Further in presence of a high number of catalytic positions one may suppose increases of pretransitions probabilities. An infiltrated aluminium matrix composite containing 23% oriented SiC whiskers has been considered in order to satisfy the conditions of small volumes and of a high number of catalytic positions. The experimental results are obtained by X-ray diffraction line broadening Fourier analysis.

Phase transitions often occur together with the so-called pretransitional phenomena. The origin of these phenomena is the appearance of a competing thermodynamic phase inside a host phase. The phenomena become more important near the thermodynamical transition temperature. A number of experiments displaying an abnormal behaviour during freezing and melting may be found in literature. Molecular dynamics as well Monte Carlo methods have been used for treating the solid-liquid phase transition. These computer simulations have clearly shown the coexistence of two kinds of configurations: crystalline and liquid-like structures. Statistical mechanics shows that pretransitions are strictly correlated with fluctuation probabilities in thermal equilibrium systems; in particular smaller are the volumes interested by the fluctuation higher are the pretransition probabilities. Further in presence of a high number of catalytic positions one may suppose increases of pretransitions probabilities. An infiltrated aluminium matrix composite containing 23% oriented SiC whiskers has been considered in order to satisfy the conditions of small volumes and of a high number of catalytic positions. The experimental results are obtained by X-ray diffraction line broadening Fourier analysis.

Keywords

transição de fase, pré-transição, materiais compostos, difração de raios X, análise de Fourier

transição de fase, pré-transição, materiais compostos, difração de raios X, análise de Fourier