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Detección de transiciones de fase líquido/líquido de primer orden en fundidos de óxido de yttrio y óxido de aluminio
G N Greaves1, M C Wilding, S Fearn
1Centre for Advanced Functional Materials and Devices, Institute of Mathematics and Physics, Aberystwyth University, Aberystwyth SY23 3BZ, UK. gng@aber.ac.uk
Science (New York, N.Y.)
|October 25, 2008
Resumen
Los fundidos de Yttria-Alumina exhiben una transición de fase reversible de primer orden a altas temperaturas, evidenciada por la desmixura de líquidos a nanoescala y los cambios estructurales a escala atómica. Este fenómeno crea un "rotor poliamórfico" en líquidos súper enfriados.
Área de la Ciencia:
- Ciencia de los materiales Ciencia de los materiales.
- La Química Física es la química física.
- Física de la materia condensada Física de la materia condensada
Sus antecedentes:
- Las transiciones de fase en materiales líquidos son cruciales para comprender sus propiedades.
- Estudios previos habían inferido transiciones en fundiciones de yttria-alumina de vidrios apagados.
- Los estudios in situ de las transiciones de fase líquida a alta temperatura en condiciones sin contacto son desafiantes.
Objetivo del estudio:
- Para investigar in situ las transiciones de fase en fundiciones de yttria-alumina a altas temperaturas.
- Para caracterizar los cambios a nanoescala y a escala atómica durante estas transiciones.
- Para cuantificar las propiedades termodinámicas asociadas con las transiciones observadas.
Principales métodos:
- La dispersión combinada de rayos X de ángulo pequeño (SAXS) y la dispersión de rayos X de ángulo ancho (WAXS).
- Se utiliza la levitación aerodinámica para el manejo de muestras sin contacto a altas temperaturas.
- Se observó in situ la evolución estructural y el comportamiento dinámico de los fundidos levitados.
Principales resultados:
- Se identificó una transición de fase de primer orden en las fusiones de yttria-alumina a altas temperaturas.
- SAXS reveló que el líquido a nanoescala no se mezclaba, indicado por un máximo reversible.
- WAXS mostró cambios abruptos en el empaque poliédrico, lo que significa cambios estructurales a escala atómica.
- Se observó un observado a.
- El rotor poliamórfico es un rotor poliamórfico.
- fenómeno impulsado por transiciones repetitivas.
Conclusiones:
- La transición a alta temperatura en las fusiones de yttria-alumina implica tanto la desmixura de líquidos a nanoescala como los reordenamientos estructurales a escala atómica.
- El rotor poliamórfico observado permite estimar los cambios reversibles en el volumen molar y la entropía.
- Este estudio proporciona nuevos conocimientos sobre el complejo comportamiento de los fundidos de óxido en condiciones extremas.
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