SANITARY-WARE: FROM THE INDUSTRIAL MACRO CHARACTERIZATION TO THE ATOMIC SCALE ANALYSIS

Sanitary-ware products are one of the most diffused ceramic materials which can be found as bathroom furniture in every building. They are formed by two distinct parts: the ceramic body and the covering material (glaze), fired together at about 1200°C in order to develop the phase reactions which finally fix the mineralogical composition, the microstructure and consequently, the technical and aestethical properties of the material. In the present thesis, a wide exploration of these materials will be presented: it starts from a wide characterization of industrial interest (Part I) and goes deeper and deeper to the atomic scale analysis (Part III), passing through the study of the parameters which can affect the accuracy in glaze quantitative phase analysis (Part II). 1. Part I is aimed at the evaluation of the influence of compositional and procedural parameters on the evolution of ceramic body and glaze. So, different grids of samples were prepared within typical industrial ranges to highlight differences, if present, by means of some conventional industrial measurements (i.e. Water Absorption, Dilatometry, Hot Stage Microscope) and other more detailed techniques (X-ray Powder Diffraction, Scanning Electron Microscope and also Synchrotron X-ray Tomography). In Chapter 1, the effects of firing time and temperature, and of particle size have been observed on the glass phase formation and on the some technological properties like the porosity and the thermal expansion, which may affect, in turn, the quality of the product. On the other hand, in Chapter 2, glaze, which is a quite different from the ceramic body, was studied by varying its composition in order to look at its behavior during and after the firing process because adhesion on the ceramic support is required. Moreover, some effective tools have been defined to characterize glaze microstructure, especially by means of Synchrotron X-ray Tomography. 2. Part II looks at the methodological parameters which may affect the quantification of the main crystalline phase within glaze (i.e. zircon), in case of large amorphous content, with X-ray Powder Diffraction technique. The presence of abundant glass phase comes from the typical composition of sanitary-glaze and may be problematic if an accurate quantitative phase analysis is looked for. Different internal standard, corrections, data treatment and sample preparation procedures were used in order to find the protocol that provides the most accurate results on artificial samples of known composition. Furthermore, some Scanning Electron Microscope images and Laser Scattering measurements were carried out as complementary data to clarify some aspects inaccessible to X-ray Powder Diffraction. 3. Part III moves the attention to the atomic scale of the sanitary-ware, in particular to the amorphous part of sanitary-glaze, which strongly model some technological properties of the material (i.e. glass transition temperature). To access the structure of the amorphous material, total scattering is one of the most accurate techniques; thus, three significatively different glasses were prepared and collected by coupling neutron and X-ray total scattering. Data modeling was performed to get the structural model and consequently to extract some interesting information like the distances between atom pairs, their coordination number and bond angles, and also the type of oxygen sharing.