A facile synthesis of mesoporous crystalline tin oxide films involving a base-triggered formation of sol-gel building blocks

We have developed a new facile procedure for manufacturing crystalline thin films of SnO2 with a uniform mesoporous architecture and full crystallinity of the walls. The procedure is based on the evaporation-induced self-assembly (EISA) of prehydrolyzed tin oxide precursor directed by a commercially available Pluronic polymer. The formation of the tin oxide precursor, which can be self-assembled into a mesoporous structure, is achieved by an addition of ammonium hydroxide to a tin tetrachloride solution. The relative concentration of ammonium hydroxide as well as the duration and temperature of the hydrolysis reaction influence significantly the properties of hydrolyzed tin oxide species and the mesostructure assembled from them. The films coated from these precursor solutions and calcined at 300 °C to 400 °C exhibit a well-developed worm-like porosity with a wall to wall distance of ca. 18 nm, a surface area of up to 50 cm2 cm(-2) (corresponding to 55±5 m2 g(-1)), and high crystallinity.     

Effects of marble powder as a partial replacement of cement on some engineering properties of self-compacting concrete

Self-compacting concretes (SCC) are highly fluid concretes that can flow and be placed in formwork under their own weight without the requirement of internal or external energy. This fluidity is obtained with the use of high paste volume and superplasticizer. The paste of SCC is made principally of cement, which is the most expensive component of concrete. As a result, the production cost of SCC is higher than conventional concrete. However, to make the manufacture of SCC more practical and economical, the binder is often a binary, ternary even quaternary compound: Portland cement mixed with mineral additions. The primary aim of this work is to study the effect of incorporating the marble powder as a supplementary cementations material on the rheological and mechanical properties of SCC. The fresh properties were measured using the slump flow, J-Ring, V-funnel, and modified slump flow. The properties of hardened SCC such as strengths and ultrasonic pulse velocity (UPV) were determined at age of 3, 28, and 90 days. The results have shown that using of marble powder in SCC enhances their fresh properties. At hardened state, the incorporation of marble powder decreases the mechanical strengths and UPV. It can be noted that it is possible to produce an economical SCC when the cement is partially substituted by the marble powder.     

Semiempirical kinetic modelling of water desalination by electrodialysis processes

Water desalination was performed by electrodialysis (ED) in batch recirculation mode by means of cationic and anionic membranes containing sulfonate and ammonium groups, respectively. Variations in sodium chloride (NaCl) concentration in dilute compartment versus time during ED experiments were recorded at different voltages, flow rates, and feed concentrations. ED experiments were modelled by means of a semiempirical kinetic model. A good agreement is found between experimental data and the model.