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Highly active photocatalytic TiO2 samples were synthesized by thermohydrolysis of TiCl4 in water at 100 °C. Rutile, binary mixtures of anatase and rutile or anatase and brookite or ternary mixtures of anatase, brookite, and rutile were obtained depending on the TiCl4/H2O ratio. Rietveld refinements were employed to evaluate the crystalline phases and composition of the mixtures. The effect of the aging time on the phase composition was also studied. The band gap values of the samples were obtained by the diffuse reflectance spectra. The position of the flat band potentials of anatase, brookite, and rutile was determined measuring the photovoltage as a function of the suspension pH. From these data, the relative positions of the energy bands of the three semiconductors were estimated. 4-Nitrophenol photodegradation was used to evaluate the photoactivity of the various samples. Some powders were more active than Degussa P25. The most efficient samples consisted of a ternary mixture of anatase, brookite, and rutile. The high photocatalytic activity was explained by the presence of junctions among different polymorphic TiO2 phases that enhance the separation of the photogenerated electron−hole pairs, hindering their recombination.

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Monolithic and transparent gels were prepared by mixing various ethoxide silicon precursors containing Si-CH, and Si-H groups, the composition ensuring the same number of C-H and Si-H bonds. Pyrolysis of these samples was followed under helium flow by connecting thermogravimetry, gas chromatographic and mass spectrometric analysis, to study the conversion of the gels into oxycarbide materials. In addition to the usual direct thermal and mass spectra analysis (TG-MS), a TG-GC-MS arrangement, allowing gas chromatographic separation of the species simultaneously evolving during thermodecomposition followed by mass spectral analysis, was successfully achieved. Experimental results indicate that mass loss occurs in three steps, each characterized by specific reactions. At low temperatures, densification of the siloxane network derives from further condensation reactions. At intermediate temperatures, a remarkable rearrangement of the siloxane chains occurs, with the release of volatile silanes and several siloxane fragments due to Si-H and Si-0 bond exchanges. At higher temperatures, the development of methane was detected and attributed to Si-C bond cleavage. Pyrolysis of gels containing only Si-CH, or Si-H groups was also studied for comparison.

Copper phthalocyanine (CuPc) thin films have been deposited by a recently developed plasma-based method named glow-discharge-induced sublimation (GDS). The deposition of CuPc films has also been obtained by vacuum evaporation (VE) and the comparison of the two methods shows important structural differences. FT-IR and ion beam analyses (RBS-ERDA) show that the GDS-deposited films mainly consist of integer CuPc molecules, but at increasing deposition time the incorporation of damaged molecules becomes important. X-ray diffraction, FT-IR spectroscopy, and UV−vis analysis are used to study the microstructure of the CuPc films and point out that while the VE films consist of only α crystallites, a more disordered structure with the presence of both α and β polymorphs characterizes the GDS films. The latter films are also much more porous as shown by nitrogen physisorption measurements and SEM. Thermal treatments of the GDS films determine a decrease of the structural disorder at 250 °C and the complete transformation to the β polymorph at 290 °C.

Organic phase change materials (PCMs) represent an effective solution to manage intermittent energy sources as the solar thermal energy. This work aims at encapsulating docosane in organosilica shells and at dispersing the produced capsules in epoxy/carbon laminates to manufacture multifunctional structural composites for thermal energy storage (TES). Microcapsules of different sizes were prepared by hydrolysis-condensation of methyltriethoxysilane (MTES) in an oil-in-water emulsion. X-ray diffraction (XRD) highlighted the difference in the crystalline structure of pristine and microencapsulated docosane, and 13C solid-state nuclear magnetic resonance (NMR) evidenced the influence of microcapsules size on the shifts of the representative docosane signals, as a consequence of confinement effects, i.e., reduced chain mobility and interaction with the inner shell walls. A phase change enthalpy up to 143 J/g was determined via differential scanning calorimetry (DSC) on microcapsules, and tests at low scanning speed emphasized the differences in the crystallization behavior and allowed the calculation of the phase change activation energy of docosane, which increased upon encapsulation. Then, the possibility of embedding the microcapsules in an epoxy resin and in an epoxy/carbon laminate to produce a structural TES composite was investigated. The presence of microcapsules agglomerates and the poor capsule-epoxy adhesion, both evidenced by scanning electron microscopy (SEM), led to a decrease in the mechanical properties, as confirmed by three-point bending tests. Dynamic mechanical analysis (DMA) highlighted that the storage modulus decreased by 15% after docosane melting and that the glass transition temperature of the epoxy resin was not influenced by the PCM. The heat storage/release properties of the obtained laminates were proved through DSC and thermal camera imaging tests.