Rui M. Novais

Waste glass from end-of-life fluorescent lamps as raw material in geopolymers

Nowadays the stunning volume of generated wastes, the exhaustion of raw materials, and the disturbing greenhouse gases emission levels show that a paradigm shift is mandatory. In this context, the possibility of using wastes instead of virgin raw materials can mitigate the environmental problems related to wastes, while reducing the consumption of the Earths natural resources. This innovative work reports the incorporation of unexplored waste glass coming from end-of-life fluorescent lamps into geopolymers. The influence of the waste glass incorporation level, NaOH molarity and curing conditions on the microstructure, physical and mechanical properties of the geopolymers was evaluated. Results demonstrate that curing conditions are the most influential factor on the geopolymer characteristics, while the NaOH molarity is less important. Geopolymers containing 37.5% (wt) waste glass were successfully produced, showing compressive strength of 14MPa (after 28days of curing), suggesting the possibility of their use in non-structural applications. Porous waste-based geopolymers for novel applications were also fabricated.

Synthesis of ceramic pigments from industrial wastes: Red mud and electroplating sludge

The perception of industrial waste has changed, in the last decades, from an economic and environmental problem to a potential raw material. In this work, the synthesis of a stable pigment was prepared by combining two hazardous and unexplored wastes: red mud (RM, rich in Fe) and electroplating sludge (ES, rich in Ni/Cr). The wastes were mixed in different proportions and calcined at 1200 °C. Black and brown pigments were obtained from the mixture of RM/ES in 1:3 and 1:1 wt proportions, respectively. The color was given by the chrome-iron-nickel spinels, based on Ni2+ 3T1g(3F) transitions (≈13,000 cm-1), Cr3+ 4A2g → 4T1g(4F) transitions (≈24,400 cm-1) and Fe3+ (≈15,000-≈22,500 cm-1). The achieved coloring strength and thermal stability on various ceramic glazes render excellent prospects for the industrial application of such waste-based pigments.

Desenvolvimento de geopolímeros de baixa condutividade térmica

Conventional thermal insulation materials, such as glass wool and extruded polystyrene, owned-in significant technical limitations. The geopolymers emerge as an alternative due to their properties. In this sense the objective of this work is to describe the develop geopolymers with low thermal conductivity. Samples of geopolymers were produced from metakaolin (Al2O3.2SiO2) which, due to its high reactivity, made it possible to produce inorganic polymers with interesting physical properties, which can be used for thermal insulation. The samples of aluminosilicate were activated with sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). Samples of light geopolymers were produced with addition of different percentages of a pore former (0.5, 1, 2, 3, 4%). The samples were characterized with respect to: compressive strength, water absorption, thermal conductivity, density and microstructure.

Lightweight Bi-Layered Ceramic Tiles for Novel Applications

The excellent properties of porcelain stoneware tiles make them ideal materials for floor covering. However, their high density limits their use in novel applications, where low weight and low thermal conductivity are required. In this work, the production of lightweight bi-layered ceramics, with suitable mechanical resistance and low thermal conductivity in comparison with commercial tiles, is reported. The weight and thermal conductivity reduction was achieved by means of porogen incorporation. The possibility of using polypropylene (PP) as a pore forming agent was evaluated. PP completely burns out at relatively low temperatures with no emission of hazardous gases, and does not induce defects in the ceramic pieces. Results demonstrate that porosity (pore volume, number and area) can be easily controlled by adjusting the porogen amount (5-15 wt.%). The reduction in weight (7.5%) and thermal conductivity (up to five times) in comparison to commercial stoneware tiles might extend their use to novel applications.