A educação de Victor de Aveyron: do isolamento na floresta ao isolamento em sociedade.

International audienc

Optimization of Drilling Cuttings Reactivity as a Supplementary Cementitious Material in Ternary Cements

This study evaluates the influence of milling on the reactivity of drilling cuttings (DC) utilized as supplementary cementitious material in ternary cements (TC). The drilling cuttings milling study varied the time (2, 5, 10, 15, and 20 min) and rotation speed (200 and 300 rpm), determining the specific milling energy and grindability index. The hydration of TC pastes containing DC with different particle size distributions was evaluated by isothermal calorimetry during the first 72 hours, XRD/Rietveld at 3 and 28 days, compressive strength and absorption. The incorporation of milled DC improved the TC hydration kinetics compared to reference pastes of ordinary Portland cement (REF.PC). After 28 days, the TC pastes with the D50% diameter smaller than 11 µm reached at least 70% of the resistance to the strength of the Portland cement paste. Milled DC contributes to the physical and nucleation effect of the TC pastes studied and can be used as an SCM

Ce0.97Cu0.03O2 Nanocatalysts Synthesized via Microwave-assisted Hydrothermal Method: Characterization and CO-PROX Catalytic Efficiency

In the work presented here, Ce0.97Cu0.03O2 nanoparticles were synthesized by a microwave-assisted hydrothermal method under different synthesis temperatures. The obtained nanoparticles were tested as catalysts in preferential oxidation of CO to obtain CO-free H2 (PROX reaction). The samples were characterized by X-ray diffraction, transmission electron microscopy (TEM), electron paramagnetic resonance spectroscopy (EPR) and temperature-programmed reduction (TPR). X-ray diffraction measurements detected the presence of pure cubic CeO2 for all synthesized samples. TEM images of the Ce0.97Cu0.03O2 nanoparticles revealed that samples synthesized at 80°C are composed mainly of nanospheres with an average size of 20 nm. The formation of some nanorods with an average diameter of 8 nm and 40 nm in length, and the size reduction of the nanoparticles from 20 to approximately 15 nm is observed with increasing synthesis temperature. EPR spectra indicated that copper is found well dispersed in sample synthesized at 160°C, located predominant in surface sites of ceria. For samples synthesized at 80 and 120°C, the species are less dispersed than in the other one, resulting in the formation of Cu2+−Cu2+ dimmers at the surface of ceria. TPR profiles presented two reduction peaks, one below 400°C attributed to the reduction of different copper species and a second peak around 800°C attributed to the reduction of Ce4+→ Ce3+ species located in the volume of the nanoparticles. The peak related to the reduction of copper species shifts to lower temperatures with increasing synthesis temperature, i.e., the sample synthesized at 160°C is more easily reduced than the ones synthesized at 120 and 80°C. The nanoparticles showed active as catalysts for the CO-PROX reaction. The microwave-assisted method revealed efficient for the synthesis of Ce0.97Cu0.03O2 nanoparticles with copper species selective for the CO-PROX reaction, which reaches CO conversions up to 92% for the sample synthesized at 160°C