In the present work, the effect of mineral aggregates (pumice stone and expanded clay aggregates) and chemical admixtures (superplasticizers and shrinkage reducing additives) as an alternative internal curing technique was investigated, to improve the properties of high-performance concrete. In the fresh and hardened state, concretes with partial replacements of Portland cement (CPC30R and OPC40C) by pulverized fly ash in combination with the addition of mineral aggregates and chemical admixtures were studied. The physical, mechanical, and durability properties in terms of slump, density, porosity, compressive strength, and permeability to chloride ions were respectively determined. The microstructural analysis was carried out by scanning electronic microscopy. The results highlight the effect of the addition of expanded clay aggregate on the internal curing of the concrete, which allowed developing the maximum compressive strength at 28 days (61 MPa). Meanwhile, the replacement of fine aggregate by 20% of pumice stone allowed developing the maximum compressive strength (52 MPa) in an OPC-based concrete at 180 days. The effectiveness of internal curing to develop higher strength is attributed to control in the porosity and a high water release at a later age. Finally, the lowest permeability value at 90 days (945 C) was found by the substitutions of fine aggregate by 20% of pumice stone saturated with shrinkage reducing admixture into pores and OPC40C by 15% of pulverized fly ash. It might be due to impeded diffusion of chloride ions into cement paste in the vicinity of pulverized fly ash, where the pozzolanic reaction has occurred. The proposed internal curing technology can be considered a real alternative to achieve the expected performance of a high-performance concrete since a concrete with a compressive strength range from 45 to 67 MPa, density range from 2130 to 2310 kg/m3, and exceptional durability (< 2000 C) was effectively developed.

Silver antimony selenide (AgSbSe2) thin films were prepared by heating sequentially deposited antimony sulphide (Sb2S3), silver selenide (Ag2Se) and Ag thin films in close contact with a selenium thin film. Sb2S3 thin film was prepared from chemical bath containing SbCl3 and Na2S2O3, Ag2Se from the bath containing AgNO3 and Na2SeSO3 and Se thin films from an acidified solution of Na2SeSO3, at room temperature on cleaned glass substrates. Ag thin film was deposited by vacuum thermal evaporation. The annealing temperature was varied from 300-390°C in vacuum (∼10−3 Torr) for 1 h. X-ray diffraction analysis showed the films formed at 350 °C was polycrystalline AgSb(S,Se)2 or AgSbSe2 depending on selenium thin film thickness. Morphology of these films was analyzed using Atomic Force Microscopy and Scanning Electron Microscopy. The elemental analysis was done using Energy Dispersive X-ray technique. Optical characterization of the thin films was done by optical transmittance spectra. The electrical characterizations were done using Hall effect and photocurrent measurements. A photovoltaic structure: Glass/ITO/CdS/AgSbSe2/Ag was formed, in which CdS was deposited by chemical bath deposition. J-V characteristics of this PV structure showed Voc=370 mV and Jsc=0.5 mA/cm2 under illumination using a tungsten halogen lamp.

En este trabajo se reportan los resultados preliminares sobre la formación de películas delgadas de AgSb(S,Se )2 • Las películas delgadas de Sb,S, y Ag,Se fueron depositadas secuencialmente sobre substratos de vidrio a temperatura ambiente (25º C) de baños químicos que contenían soluciones de (SbCl, y Na,S2O,) y (AgNO, y Na,SeSO,), respectivamente. Se obtuvieron multicapas de: Vidrio/ Sb,S/ Ag,Se, las cuales fueron sometidas a calentamiento en aire a 300 ºC por½ h (muestra 'A'). También, multicapas de: Vidrio/ Sb,S/Ag,Se fueron calentadas a las mismas condiciones en presencia de vapor de selenio, producido desde una película delgada de Selenio puesta en contacto con la multicapa (Vidrio/ Sb,S3/Ag 2Se+Se/ZnS-Vidrio (Muestra 'B'). Las películas delgadas de Selenio fueron crecidas sobre un sustrato de vidrio recubierto de ZnS desde una solución que contenía Na,SeSO,. Los análisis de difracción de X-ray de la superficie de esas muestras mostraron la formación de la fase monoclínicadeAgSbSe,S,., ( en el caso de la muestra 'A') y fase monoclínicaAgSb(S,Se), ( en el caso de la muestra 'B'). En ambos casos, se encontró la fase ortorrómbica de Sb,S, sin reaccionar. El análisis de electrones Auger de esas muestras detectaron la presencia de los elementos Ag, Sb, S, y Se en las películas formadas después del calentamiento.

The morphological characteristics of ZnO nanostructures were systematically studied from dense rods to flower-like shapes. The ZnO flower-like samples were prepared by direct decomposition of a Zn(OH) 4 2precursor and by the sequential nucleation and growth method consisted of a multistep synthesis of complex nanostructured films. Condition-dependent experiments systematically were compared as to reveal the formation and detailed growth process of ZnO nanosized crystallites and aggregates. X-ray diffraction, transmission and scanning electron microscopy indicated that the precursor, solution basicity, reaction temperature and pressure as well as reaction time, were responsible for the variations of the morphologies. ZnO flower-like and large nanorods of exceptional uniformity, orientation alignment, and optical properties have been produced in this work. Several synthesis steps are needed to produce oriented nanostructures that are more complex than simple nanorod architectures. These structures have potential applications in building functional electronics devices and optoelectronic properties.