Characterization of biological stains on external concrete walls and influence of concrete as underlying material

International audienceInvestigations were carried out on concrete walls stained by biological growth. Pieces of this material were removed down and observed using optical microscopy, low-vacuum scanning electron microscopy (LVSEM) and normal SEM. The results show that biological stains are due to two different kinds of microscopic algae, Chlorophyceae and Cyanophyceae, whose presence depends on the amount of moisture on the concrete wall. Accelerated laboratory tests of biological growth on mortar samples that were performed show that algal developments increase with the porosity of the underlying material. Thus, it seems that the use of dense, high-performance mortars can slow down or even inhibit microorganism growth

Siège d'Ostende : [estampe]

Référence bibliographique : Hennin, 704

Bataille de Wynendael : [estampe]

Référence bibliographique : Hennin, 719

Bronsted acids catalyzed synthesis of Pyrans via a formal [3+3] cycloaddition

International audienc

Single- and Few-Walled Carbon Nanotubes Grown at Temperatures as Low as 450 °C: Electrical and Field Emission Characterization

Single-wall (SW-) and few-walled (FW-) carbon nanotubes (CNTs) were synthesized on aluminum/cobalt coated silicon at temperatures as low as 450 °C by plasma enhanced chemical vapor deposition technique (PECVD). The SWCNTs and FWCNTs grow vertically oriented and well separated from each other. The cold field emission studies of as-grown SWCNTs and FWCNTs showed low turn-on field emission threshold voltages, strongly dependent of the nanotubes morphology. Current-voltage curves of individual CNTs, measured by conductive atomic force microscopy (CAFM), showed an electrical resistance of about 90 KO, that is attributed mainly to the resistance of the contact between the CNTs and the conductive CAFM tip (Au and Pt).JRC.I.4-Nanotechnology and Molecular Imagin