Magali Brisbois

Hybrid lamellar silica: Combined template extraction and hydrophilic silanation

The surface modification of lamellar silica prepared by liquid crystal templating has been investigated. Two hydrophilic surface modifier agents, 2-glycidoxypropyltrimethoxysilane and 2-[methoxy(polyethyleneoxy)propyl)]trimethoxysilane, have been tested. Characterizations of the modified silica include thermal analysis, (13)C and (29)Si solid state NMR, transmission electron microscopy (TEM) and X-ray diffraction (XRD). The different characterizations confirmed the preservation of the lamellar morphology and the successful surface modification with both silanes along with the template elimination. The results also indicate that the structure and length of the silanes influence the final lamellar organization as well as the grafting yields and mechanisms.

Li4Ti5O12 powders by spray-drying: influence of the solution concentration and particle size on the electrochemical properties

The lithium battery electrode compound Li4Ti5O12 was synthesized by calcination of precursor powders obtained through spray-drying of solutions prepared with titanium isopropoxide and lithium nitrate. X-ray diffraction and thermal analysis coupled to mass spectrometry show that single phase crystalline Li4Ti5O12 particles can be obtained after calcination at 800 °C for 2 hours. Decreasing the solution concentration leads to smaller particle sizes but also to an unexpected decrease of the electrochemical capacity, probably related to the presence of residual Li2TiO3. On the contrary, the capacity of the Li4Ti5O12 powder prepared with the high concentration solution can be increased from 150 mAh/g to 165 mAh/g (C/4 rate) by grinding. These results highlight the fact that smaller particles do not systematically display better performances for Li+ intercalation/desintercalation and confirm the need for a comprehensive approach including parameters such as crystallinity, phase purity or agglomeration.

Nuclear probes for battery materials investigations: Mössbauer spectroscopy, nuclear scattering, and neutron scattering

Selected examples of application of Mössbauer spectroscopy, nuclear resonance scattering of synchrotron radiation, and neutron scattering to battery and related materials research are presented. The charms of Mössbauer spectroscopy as a technique for screening materials, for detailed structure investigations, and for in situ measurements are illustrated. New developments of nuclear resonance scattering for isotopes with 30-90 keV resonant energy are presented. Structural, diffusive and dynamic studies utilizing neutron scattering are exemplified.