C. Battistoni

Interaction of mercury vapour with thin films of gold

Thin films of gold deposited on a silicon substrate were used as electrical sensors of mercury vapour. The samples were exposed to mercury vapour at room temperature, changing the Hg concentration and the exposure time. The chemical composition and morphology of the films exposed to mercury vapour were studied by X-ray photoelectron spectroscopy (XPS), secondary ion mass spectroscopy (SIMS), scanning Auger microscopy (SAM) and secondary electron microscopy (SEM). In the samples exposed for a short time, the mercury was adsorbed by thin surface sublayer of Au film. In the case of long exposures, the transformation of the uniform Au film to a dendritic-like coalesced AuHg amalgam occurred, i.e. the morphology of the film was modified irreversibly. This transformation is caused by insufficient adhesion of gold to the substrate.

Surface characterization of biocompatible hydroxyapatite coatings

The coatings of hydroxyapatite are widely used for orthopaedic and dental prostheses. Nevertheless, their chemical, biological and mechanical properties still can be improved by the development of new preparation technologies. Here we report a surface characterization of hydroxyapatite coatings prepared by different deposition techniques. The layers of hydroxyapatite are grown on commercial titanium substrates by using sol-gel and electrodeposition techniques. The biocompatibility of the samples is tested upon in vitro treatment as a function of the exposure time. Surface chemical composition and morphology of the coatings are studied by means of x-ray photoelectron spectroscopy (XPS), scanning Auger microscopy (SAM) and scanning electron microscopy (SEM). Quantitative XPS analysis and surface chemical and physical images reveal different features (cleanness, homogeneity, roughness) of the coatings and different surface modifications induced by the interaction with osteoblast cells.

XPS study of ceramic three-way catalysts

Three-way catalysts used in automotive exhaust converters were investigated by means of selected-area XPS. The main purpose of this study was to improve the understanding of deactivation processes occurring when the catalyst is operating in gas exhaust. The washcoat of the converter (γ-alumina with ceria and other stabilising additives) was supported on a honeycomb monolith of cordierite. Catalysts (Pd and Rh) were doped in the washcoat surface. The samples of the new converter and the same converter after various treatments were analysed. From the characteristic shape and chemical shift of the XPS peaks, the chemical state of the active elements (Ce, La, Ba, Pd, Rh) and the contaminants (P, Pb, Zn, Ca, etc.) was determined before and after the sample treatments. These results together with the data of quantitative XPS testified that, after the medium operation time of 500 h, the gas converter was deteriorated. The main reasons and the consequences of this degradation are revealed.

Theoretical study of mono- and dithiocarbazic acid derivatives

Abstract The patterns of charge distribution in a series of derivatives of thiocarbazic acid are studied by means of several theoretical LCAO-MO methods: ab initio minimal basis-set, CNDO/2, INDO and EHT. Correlations are made between the electronic structures obtained from the calculations, the nature of the different substituents and some experimental IR, X-ray and XPS results.

Molecular cluster studies of defects in tetrahedral lattices: Dangling bonds reconstruction at the core of a 90° partial dislocation in diamond

Abstract The energetics of bond reconstruction at the core of a 90° partial dislocation in diamond has been studied by means of HFR-MO-LCAO-SCF computations on C5H10 and C10H18 model molecular clusters. The results obtained agree with previous VFF investigations and they confirm that the reconstructed geometry is energetically favoured with respect to the unreconstructed one.

A note about the structure ofπ 2 SiHSiH

SummaryIt has been computed the potential-energy curve ofπ2 SiH, as a function of the silicon hydrogen bond distance, by means ofab initio HFR-MO-LCAD-SCF-CI method. It has been investigated, in particular, the influence of different basis sets on the computed structural and vibrational properties of above-quoted molecule.RiassuntoSi è effettuato il calcolo della curva di energia potenziale dello statoπ2 di SiH in funzione della distanza di legame silicio-idrogeno per mezzo di metodiab initio HFR-MO-LCAD-SCF-CI. In particolare si è studiata l’influenza che hanno diversi insiemi di funzioni di base sul calcolo delle proprietà strutturali e vibrazionali della molecola in questione.

The role of chemistry in the research on advanced materials in Italy (I). The ZIC paradigm

This paper reviews the main achievements of the Targeted Project “Special Materials for Advanced Technology” (TP SMAT [1989–1993]).It describes the analysis of funding provided by TP SMAT and the most important results of TP SMAT with reference to both scientific publications issued (together with the relative impact factor) and technology demonstrators produced. Human skills developed and new facilities are also taken into account.It also analyzes a new way of managing Targeted Project based upon cross-functional process, where timing and mode of development are merged in a single goal: an innovative electrical car (Zero Impact Car—ZIC). In this process the various topics were combined, with typical concurrent engineering tools, in a complete harmonious way in order to produce a demonstrator of new materials, technologies and integrated design (i.e. design of both structures and microstructures-materials). This new managing model is the “so called”: ZIC paradigm.