Search Results (2)

A total of forty samples of medieval and modern glazed pottery from northern Spain were studied. Chemical and microstructural analyses of the glazes were performed by scanning electron microscopy coupled with electron dispersive spectroscopy (SEM-EDX), while the chemical composition of the pottery bodies and slips were determined by X-ray Fluorescence (XRF). The glazes studied come from the Santa Barbara Hill site (Tudela), the Treviño Castle site (Treviño), the Vega workshop (Burgos) and the Torrentejo village (Labastida) and correspond to transparent glazes and opaque white glazes. Transparent glazes were lead glazes with variable PbO content. Opaque white glazes were lead-tin and lead–alkaline–tin glazes. The glaze was mainly applied to a pre-fired body made of local clays, but the glazes of the Santa Barbara Hills pottery (Tudela) were applied to raw bodies. The microstructure of the interfaces indicates a single firing process for the glazed pottery from Tudela and a double firing process in the rest of the sites. Some correlation are identified between the use of specific clays to produce different glaze colours. White opaque glazes are applied to calcium-rich clays. Similarly, calcium-rich clays were used to produce dark green transparent glazes, while clays and slips aluminium–rich were used to produce light green and light honey glazes. Iron was also identified as the main colouring agent, although copper was also used. The white glazes were opacified by the addition of cassiterite and sometimes quartz and feldspar. The glazed pottery was mainly of local origin, but the identification of some non-local pottery at all sites suggests a pottery trade. Full article

This work explores the effects of rigid (0.1, 0.25, and 0.5 wt. %) and semi-flexible (0.5, 1.0, and 2.5 wt. %) all-aromatic polyelectrolyte reinforcements as rheological and morphological modifiers for preparing phosphate geopolymer glass–ceramic composites. Polymer-modified aluminosilicate–phosphate geopolymer resins were prepared by high-shear mixing of a metakaolin powder with 9M phosphoric acid and two all-aromatic, sulfonated polyamides. Polymer loadings between 0.5–2.5 wt. % exhibited gel-like behavior and an increase in the modulus of the geopolymer resin as a function of polymer concentration. The incorporation of a 0.5 wt. % rigid polymer resulted in a three-fold increase in viscosity relative to the control phosphate geopolymer resin. Hardening, dehydration, and crystallization of the geopolymer resins to glass-ceramics was achieved through mold casting, curing at 80 °C for 24 h, and a final heat treatment up to 260 °C. Scanning electron microscopy revealed a decrease in microstructure porosity in the range of 0.78 μm to 0.31 μm for geopolymer plaques containing loadings of 0.5 wt. % rigid polymer. Nano-porosity values of the composites were measured between 10–40 nm using nitrogen adsorption (Brunauer–Emmett–Teller method) and transmission electron microscopy. Nanoindentation studies revealed geopolymer composites with Young’s modulus values of 15–24 GPa and hardness values of 1–2 GPa, suggesting an increase in modulus and hardness with polymer incorporation. Additional structural and chemical analyses were performed via thermal gravimetric analysis, Fourier transform infrared radiation, X-ray diffraction, and energy dispersive spectroscopy. This work provides a fundamental understanding of the processing, microstructure, and mechanical behavior of water-soluble, high-performance polyelectrolyte-reinforced geopolymer composites. Full article