Is Rust a Real Must? From Design to Applications of Multifunctional Fe2O3-based Nanomaterials

G. Carraro
Abstract & Cover

The present PhD thesis is devoted to the design and fabrication of multi-functional Fe2O3-based nanomaterials by means of vapor phase techniques, such as chemical vapor deposition, both thermal (CVD) and plasma enhanced (PECVD), atomic layer deposition (ALD) and sputtering, either as such or combined into original preparation strategies. The performed research activities have covered the entire material production chain, encompassing the preparation of the molecular precursor, the material development and chemico-physical characterization, up to the ultimate functional validation for energy and environmental applications. In particular, the attention has been initially devoted to the synthesis and charac terization of a novel Fe(II) precursor [Fe(hfa)2TMEDA (hfa = 1,1,1,5,5,5-hexafluoro 2,4-pentanedionate; TMEDA = N,N,N’,N’- tetramethylethylenediamine)], possessing im proved properties for use in CVD processes with respect to the iron compounds proposed so far. The utilization of this compound in thermal CVD experiments yielded not only the most stable and widely used α-Fe2O3 phase, but also the rare and scarcely inves tigated β- and  -Fe2O3 polymorphs, that could be selectively obtained as pure phases with controlled nano-organization. In addition, Fe(hfa)2TMEDA was used in PECVD experiments as molecular source for both Fe and F thanks to the unique reactivity of non-equilibrium cold plasmas, resulting in the obtainment of F-doped α- and β-Fe2O3 nanosystems. Following the efforts devoted to the preparation of single-phase nanoma terials with improved functional performances, the fabrication of metal/oxide (M/Fe2O3, with M = Pt, Ag, Au) and oxide/oxide (CuO/Fe2O3, Fe3−xTixO4/Fe2O3) nanocomposites has finally been accomplished through the combination of CVD with sputtering or ALD. The study of the interplay between processing conditions, system features and func tional activities was proved to be a successful tool of the whole PhD research activity. To this regard, a thorough characterization of the material composition, morphology and spatial organization, micro- and nano-structure and optical properties, was carried out by the use of forefront and complementary analytical techniques. In addition, the func tional performances of selected nanosystems were investigated in view of their possible use in a variety of technological end-uses [magnetism, Li-ion batteries, gas sensing of flammable/toxic analytes, and photo-activated applications (photo-induced hydrophilic ity, photocatalytic pollutant decomposition, photocatalytic and photoelectrochemical H2 production)]. The results obtained in this PhD work demonstrate that the preparation of iron(III) oxide systems, either as such or in combination with others guest phases, with selected phase composition (α- or β- or  -Fe2O3) and nano-organization, represents a valuable an swer to meet open challenges in various high-tech applications. In particular, the adopted approaches involving vapour phase-related routes offer the possibility of future up-scaling and commercialization of the studied materials, one of the key issues for their technological exploitation in advanced devices.

Source of Information
Claudia Wiemer / Riikka
Università di Padova
(Padova, Italy)
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