SEMINARIS DE LA FACULTAT DE GEOLOGIA I L'INSTITUT DE CIÈNCIES DE LA TERRA 'JAUME ALMERA'
Rile I. RISTIC (Chemical and Bioengineering Dept, University of Sheffield, Regne Unit)

The aim of these studies is twofold: (1) to establish sound scientific principles that guide a nucleation rate and selection of a desired polymorph in this class of material via application of mechanical energy - ultrasound (US) irradiation and (2) to develop a reliable assessment of the time dependent spherulitic growth kinetics and its coupling with respective time dependent evolution of thermodynamic properties of the crystallising system.

In the first part, we shall consider the crystallisation of typical polymorphic melt-grown materials such as tripalmitin (PPP) and trilaurin (LLL) with and without ultra sound (US) by using in- situ simultaneous synchrotron radiation time-resolved small-angle X-ray scattering (SAXS) and wide angle X-ray scattering (WAXS), SAXS/WAXS. Without US application, both polymorphic forms β' and β crystallised in the melt of either PPP or LLL. With US treatment of the super cooled melt, the following effects were observed: (a) a marked decrease of induction times for PPP and LLL, (b) an increased nucleation rate, and (b) a crystallization of only the β form in both systems. In addition, the crystallisation of LLL, below a certain temperature results to both β' and β crystals regardless the melt was US treated or not. Using the existing knowledge on the dynamic nucleation of collapsing cavities, it was possible to describe, for the first time, the behaviour of the most

Data: 14 de Desembre de 2011
Hora: 12 h
Lloc: Sala d'actes de l'Institut Jaume Almera