DALLE MATERIE PRIME DEL SISTEMA TERRA ALLE APPLICAZIONI TECNOLOGICHE: STUDI CRISTALLOCHIMICI E STRUTTURALI

The aim is to achieve a synergy combining conventional and non-conventional experimental and theoretical methods to tackle the question of stability or/and

reactivity of phengites/phlogopites and kaolinites, at such conditions as simulate natural and industrial environments, as a function of the minerals' compositions and

their deviations from ideality in terms of structure defects.

The expertises to develop such programme are attained gathering personnel of the University of Milan (HP/HT-experiments, theoretical modelling, large scale facility

measurements), of Palermo (computation and reaction kinetics modeling) and of Camerino (tomography and XAS).

All this is meant to allow one to near the inferences based on the traditional ideal models to the actual behaviour of phyllosilicates at non ambient conditions.

The activities are brought about with the support of the research units (RU) of Bari (characterization), Modena (sampling), Turin (low temperature X-ray diffraction);

among the collaborations with foreign partners we mention here the Institute of Mineralogy - University of Innsbruck (Austria). More in detail:

1) novel high pressure (HP) X-ray single crystal/powder diffraction measurements on phengites(mainly)/phlogopites from different metamorphic environments.

Correlations between (i) composition, (ii) elastic behaviour, (iii) structure evolution in response to the applied pressure, and (iv) ''memory effects'' of the environment

of crystallization;

2) development of a Monte Carlo based technique of simulation of diffraction processes in phyllosilicates to model different disorder-configurations and interpret

experimental data in the light of deviations from ideality;

3) low temperature neutron/X-ray single crystal diffraction to reconstruct the deviations from ideality by the approach at point 2;

4) modeling of the excess-effects of solid solutions on properties in phengites, by quantum-mechanic calculations. Study of the effects of how stochastic stacking

affects the relaxation mechanisms of micas under pressure, by using semi-classic potentials;

5) high temperature reactivity and reaction kinetics of kaolinites having different degree-of-disorder and mixed with Na-feldspar, as a function of temperature and

feldspar content, by in-situ and ex-situ experiments. Measurements by contrast tomography, XAS and total scattering to get insight into the nature of the resulting

glass phase;

6) effects of SiO2/SiO2.Al2O3 based glasses on the reactivity of kaolinite with different degree-of-disorder, at high temperature and simulating an industrial-like

compositional environment. Kinetic modelling. Characterization of the glass phase by tomography, XAS and total scattering;

7) role of kaolinite and its deviations from ideality in affecting the development of cristobalite from quartz-caolinite rich blends, at high temperature conditions.

Effects due to the particle size distributions.

Technical collaborations in support of: (i) ELETTRA-synchrotron for the development of the HP-beamline (already in progress) to set-up measurements conditions

which allow one to collect high-precision data to better fix elastic parameters; (ii) RU-UNIME to develop HP experiments by the high-pressure facility of the

RU-UNIMI; (iii) RU-UNIMO to model by quantum-mechanical simulations adsorption processes; (iv) RU-UNIBA to perform neutron diffraction and high pressure

X-ray diffraction experiments.

MACRO TARGETS: earth system control; waste recycling; energy saving; new materials.