Influence of Mg doping on structural, optical and photocatalytic performances of ceria nanopowders

Nanosized Mg-doped ceria powders were obtained by self-propagating room temperature reaction without using surfactants or templates. X-ray diffraction analysis and field emission scanning microscopy results showed that the doped samples are solid solutions with fluorite-type structure and spherical morphology. Raman spectra revealed an increase in the amount of oxygen vacancies with the increase of Mg concentration. This increasing results in a narrowing of the bandgap of CeO2. The photocatalytic performances of the Mg-doped ceria solid solutions were evaluated by decomposing an organic dye, crystal violet under UV irradiation. The Mg-doped ceria solid solutions exhibit significantly better photocatalytic activity than the pure CeO2 and commercial TiO2. The higher first rate constant of the Mg-doped samples demonstrated that they are much more efficient than TiO2 and CeO2 under UV light. Mg2+ dopant ions and oxygen vacancies play a significant role in the enhancement of photocatalytic performances of the Mg-doped ceria

Recommendation of RILEM TC 271-ASC: New accelerated test procedure for the assessment of resistance of natural stone and fired-clay brick units against salt crystallization

This recommendation is devoted to testing the resistance of natural stone and fired-clay brick units against salt crystallization. The procedure was developed by the RILEM TC 271-ASC to evaluate the durability of porous building materials against salt crystallization through a laboratory method that allows for accelerated testing without compromising the reliability of the results. The new procedure is designed to replicate salt damage caused by crystallization near the surface of materials as a result of capillary transport and evaporation. A new approach is proposed that considers the presence of two stages in the salt crystallization test. In the first, the accumulation stage, salts gradually accumulate on or near the surface of the material due to evaporation. In the second, the propagation stage, damage initiates and develops due to changes in moisture content and relative humidity that trigger salt dissolution and crystallization cycles. To achieve this, two types of salt were tested, namely sodium chloride and sodium sulphate, with each salt tested separately. A methodology for assessing the salt-induced damage is proposed, which includes visual and photographical observations and measurement of material loss. The procedure has been preliminarily validated in round robin tests

Recommendation of RILEM TC 271-ASC: New accelerated test procedure for the assessment of resistance of natural stone and fired-clay brick units against salt crystallization

This recommendation is devoted to testing the resistance of natural stone and fired-clay brick units against salt crystallization. The procedure was developed by the RILEM TC 271-ASC to evaluate the durability of porous building materials against salt crystallization through a laboratory method that allows for accelerated testing without compromising the reliability of the results. The new procedure is designed to replicate salt damage caused by crystallization near the surface of materials as a result of capillary transport and evaporation. A new approach is proposed that considers the presence of two stages in the salt crystallization test. In the first, the accumulation stage, salts gradually accumulate on or near the surface of the material due to evaporation. In the second, the propagation stage, damage initiates and develops due to changes in moisture content and relative humidity that trigger salt dissolution and crystallization cycles. To achieve this, two types of salt were tested, namely sodium chloride and sodium sulphate, with each salt tested separately. A methodology for assessing the salt-induced damage is proposed, which includes visual and photographical observations and measurement of material loss. The procedure has been preliminarily validated in round robin tests

Structural dependent room-temperature ferromagnetism in yttrium doped HfO2 nanoparticles

Y-doped HfO2 nanopowders, produced by metathesis synthesis, exhibit ferromagnetism at room temperature. The X-ray diffraction and Raman measurements have shown that HfO2 nanopowders undergo phase transformation from monoclinic to tetragonal and cubic phase with increasing of Y content. The X-ray photoelectron spectroscopy and Raman analysis gave evidence that Y-doped HfO2 nanopowders are oxygen deficient. The ferromagnetic properties of Y-doped HfO2 nanocrystals are dependent on crystal structure changes. The structural transformation from monoclinic to tetragonal phase with Y doping is followed by increased ferromagnetic ordering because of the increased concentration of oxygen vacancies (V-O) in different charge states. Higher Y content favors the formation of cubic phase and the ferromagnetism significantly weakens. In cubic hafnia phase, yttrium can form (V-O-Y-Hf) defect complexes in different charge states. The appearance of these complexes can be responsible for the degradation of ferromagnetic ordering. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved

Suppression of inherent ferromagnetism in Pr-doped CeO2 nanocrystals

Ce1-xPrxO2-delta (0 LT = x LT = 0.4) nanocrystals were synthesized by self-propagating method and thoroughly characterized using X-ray diffraction, Raman and X-ray photoelectron spectroscopy and magnetic measurements. Undoped CeO2 nanocrystals exhibited intrinsic ferromagnetism at room temperature. Despite the increased concentration of oxygen vacancies in doped samples, our results showed that ferromagnetic ordering rapidly degrades with Pr doping. The suppression of ferromagnetism can be explained in terms of the different dopant valence state, the different nature of the vacancies formed in Pr-doped samples and their ability/disability to establish the ferromagnetic ordering

WO3/TiO2 composite coatings: Structural, optical and photocatalytic properties

WO3/TiO2 and TiO2 coatings were prepared on titania substrates using facile and cost-effective plasma electrolytic oxidation process. The coatings were characterized by X-ray diffraction, scanning electron microscopy, Raman, UV vis diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy. With increasing duration of PEO process, the monoclinic WO3 phase became dominant and new monoclinic WO2.95 phase appeared. The optical absorption edge in the WO3/TiO2 samples, enriched with WO3/WO2.96 phase, was shifted to the visible region. The photocatalytic efficiency of WO3/TiO2 and pure TiO2 samples was evaluated by performing the photodegradation experiments in an aqueous solution of Rhodamine 6G and Mordant Blue 9 under the visible and UV light. The WO3/TiO2 catalysts are much more efficient than pure TiO2 under visible light and slightly better under UV light. The improvement of photocatalytic activity in the visible region is attributed to better light absorption, higher adsorption affinity and increased charge separation efficiency. (C) 2016 Elsevier Ltd. All rights reserved

Host–guest system of etodolac in native and modified b-cyclodextrins: preparation and physicochemical characterization

Etodolac, being a practically insoluble candidate, exhibits certain toxic effects and a limited bioavailability. Upon chronic use, it causes gastro-intestinal injury and increases the risk of ulcer complications. The approach of this study was to improve the physicochemical properties of the drug utilizing complexation phenomenon with b-, methyl-b- and hydroxypropyl-b-cyclodextrins, which may enhance the aqueous solubility and dissolution rate of etodolac, in an effort to increase oral bioavailability. In certain instances, this approach can be used to increase drug solubility, improve organoleptic properties and maximize the gastrointestinal tolerance by reducing drug irritation after oral administration. Differential UV measurements as well as continuous variation plots revealed the formation of equimolar complex with hydroxypropyl-b-cyclodextrin and 1:2 complexes with b-cyclodextrin and its methyl derivative. Differential scanning calorimetry (DSC), X-ray and FT-IR measurements were applied to prove inclusion complex formation and characterize the complexes. These results lend support to the idea that solubilization of etodolac is mainly related to inclusion complex formation and to a lesser extent to cyclodextrin aggregates. Understanding the factors that influence the performance of etodolac, will allow us to state that molecular encapsulation of the drug and other modifications with appropriate hydroxylation or methylation of parent b-cyclodextrin is able to overcome its problems and facilitate safe and efficient delivery of the drug.Springer Science+Business Medi