Dense nanostructured zirconia compacts obtained by colloidal filtration of binary mixtures

As starting materials two commercial nanosized zirconias doped with 3 mol% of Y 2O 3 were used: a powder of about 100 nm (TZ3YE, Tosoh, Japan) and a colloidal suspension of about 15 nm (Mel Chemicals, UK). Colloidal stability in water was studied for both zirconias in terms of zeta potential as a function of deflocculant concentration and pH. Concentrated suspensions were prepared by dispersing the powder in the colloidal suspension to solids loadings ranging from 5 to 30 vol.% using a sonication probe to achieve dispersion. The rheological behavior was optimized in terms of solids content, deflocculant content and sonication time. Optimized suspensions with up to 25 vol.% solids showed a nearly Newtonian behavior and extremely low viscosities and maintain stable for long times (days) which is an important drawback of conventional nanoparticle suspensions. Samples obtained by slip casting in plaster moulds were used for dynamic sintering studies and dense, nanostructured specimens were obtained at temperatures of 1300-1400°C.This work has been supported by Spanish Ministry of Science and Innovation (Projects MAT2009-14144-C03-02 and MAT2009-14369-C02-01). R. Moreno thanks to Universidad Politecnica de Valencia for the concession of a grant in the frame of its Programme of Support to R + D (PAID-02-11, R-1752).Benavente Martínez, R.; Salvador Moya, MD.; Alcázar, M.; Moreno, R. (2012). Dense nanostructured zirconia compacts obtained by colloidal filtration of binary mixtures. Ceramics International. 38(3):2111-2117. https://doi.org/10.1016/j.ceramint.2011.10.051S2111211738

Proposals for environmental impact decreasing in a suburban zone of limestone quarries: Southem Madrid Community, Spain

Over 30 Mm3 of limestones are extracted at least 100 quarries in southem part ofMadrid, its environmental impact is described in this paper. Three main reclamation areas are distinguished: surrounding of quarries, faces or highwalls of quarries and the floor. For soil reclamation in the environs of quarries we suggest to sow it with forage of fast growth plants (Lupinus, Tripho/ium ... ), in the floor of quarries is possible a spontaneous revegetation or even may be reclaimed for agricultural uses. For quarried rocks faces previous blasting and/or wider benchs are proposed. In opinion of the authors it is necessary to concentrate the limestone extraction in two or three Iarge quarries that allows a best policy and reclamation

Microstructure and photocatalytic activity of suspension plasma sprayed TiO2 coatings on steel and glass substrates

In this study, TiO 2 coatings were deposited by suspension plasma spraying (SPS) from a commercial TiO 2 nanoparticle suspension on two different substrates: a standard stainless steel and a Pyrex glass. Coatings were sprayed on both substrates with an F4-MB monocathode torch; a Triplex Pro tricathode torch was also used to spray coatings just on the stainless steel substrates. Spraying distance and cooling were varied.The anatase content in the coatings, determined by XRD, ranged from 32 to 72 wt% A significant amount of anatase to rutile transformation was found to occur during cooling. Examination of the microstructure revealed that the coating microstructure was bimodal, involving a non-molten region consisting mainly of anatase nanoparticle agglomerates and a molten region. The glass substrate coatings displayed a segregated phase distribution, particularly when the surface to be coated was cooled. Photocatalytic activity was determined by a methylene blue test.The experimental data fitted well to a first-order kinetic. All the coatings exhibited high photocatalytic activity in comparison with that of a commercial sol-gel coating. However, unlike much of the previous research, photocatalytic activity did not correlate with the anatase content determined by XRD. © 2011 Elsevier B.V.This work has been supported by the Spanish Ministry of Science and Education (MAT2009-14144-C03-01), by the Spanish Ministry of Science and Innovation (PID-600200-2009-5) and by the European Commission in the frame of the Interreg IV B Sudoe programme (Eliare: SOE1/P1/F169).Bannier, E.; Darut, G.; Sánchez, E.; Denoirjean, A.; Bordes, M.; Salvador Moya, MD.; Rayón Encinas, E.... (2011). Microstructure and photocatalytic activity of suspension plasma sprayed TiO2 coatings on steel and glass substrates. Surface and Coatings Technology. 206(2):378-386. https://doi.org/10.1016/j.surfcoat.2011.07.039S378386206

Frozen spatial chaos induced by boundaries

We show that rather simple but non-trivial boundary conditions could induce the appearance of spatial chaos (that is stationary, stable, but spatially disordered configurations) in extended dynamical systems with very simple dynamics. We exemplify the phenomenon with a nonlinear reaction-diffusion equation in a two-dimensional undulated domain. Concepts from the theory of dynamical systems, and a transverse-single-mode approximation are used to describe the spatially chaotic structures.Comment: 9 pages, 6 figures, submitted for publication; for related work visit http://www.imedea.uib.es/~victo

Microstructure and photocatalytic activity of APS coatings obtained from different TiO2 nanopowders

In recent years, intense research has shown that thermal spray techniques, especially atmospheric plasma spraying (APS), can be used to obtain nanostructured TiO2 coatings with effective photocatalytic activity. This study compares the photocatalytic activity of APS coatings obtained from different powders: two nanostructured TiO2 powders produced by spray-drying of two TiO2 nanosuspensions with different solids contents, one spray-dried powder obtained from a suspension comprising a mixture of submicronic and nanometric TiO2 particles and finally one commercial, nanostructured, TiO2 spray-dried powder. All powders were characterised by XRD, FEG-ESEM, granule size distribution, and a flowability evaluation. Feedstock powders were then deposited on austenitic stainless steel coupons using APS. Hydrogen or helium was used as secondary plasma gas. Coating microstructure and phase composition were characterised using FEG-ESEM and XRD techniques; coating anatase content was quantified by the Rietveld method. A significant amount of anatase to rutile transformation was found to take place during the plasma spraying process. In general, the coatings had a bimodal microstructure characterised by the presence of completely fused areas in addition to non-molten areas consisting of agglomerates of anatase nanoparticles. Results also showed that anatase content and porosity of the coatings largely depend on the secondary plasma gas nature, as well as on the characteristics of the feedstock. Finally the photocatalytic activity of the coatings was determined by measuring the degradation of methylene blue dye in an aqueous solution. A reasonably good fit of a first-order kinetic model to the experimental data was found for all coatings. The values of the kinetic constant were related to feedstock characteristics as well as to plasma spraying conditions. (C) 2012 Elsevier B.V. All rights reserved.Bordes, MC.; Vicent, M.; Moreno, A.; Moreno, R.; Borrell Tomás, MA.; Salvador Moya, MD.; Sanchez, E. (2013). Microstructure and photocatalytic activity of APS coatings obtained from different TiO2 nanopowders. Surface and Coatings Technology. 220:179-186. doi:10.1016/j.surfcoat.2012.08.059S17918622

A placebo-controlled proof-of-concept study of alirocumab on postprandial lipids and vascular elasticity in insulin-treated patients with type 2 diabetes mellitus

Aim: Type 2 diabetes mellitus (T2DM) is associated with an increased risk of cardiovascular disease (CVD) linked to atherogenic dyslipidaemia and postprandial hyperlipidaemia. Alirocumab, a proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor, improves CVD risk by reducing the concentration of low-density lipoprotein-cholesterol (LDL-C). However, effects of PCK9 inhibitors on other aspects of diabetic dyslipidaemia, particularly in the postprandial situation, are less clear. Material and Methods: Twelve male patients with T2DM on an intensive insulin regimen completed a 6-week randomized, double-blind, placebo-controlled, proof-of-concept study. Participants received three biweekly dosages of subcutaneous alirocumab (150 mg) or placebo. Before and after the intervention, fasting and postprandial triglyceride (TG) plasma levels, apolipoprotein (apo) B48, lipoprotein composition isolated by ultracentrifugation, vascular function and markers of inflammation were evaluated. Results: Alirocumab treatment reduced fasting plasma TG levels (between group median change −24.7%; P = 0.018) and fasting apoB48 serum levels (−35.9%; P = 0.039) compared with placebo. Alirocumab reduced the plasma TG area under the curve (AUC) (−26.4%; P = 0.006) and apoB48 AUC (−55.7%; P = 0.046), as well as plasma TG incremental AUC (−21.4%; P = 0.04) and apoB48 incremental AUC (−26.8%; P = 0.02). In addition, alirocumab reduced fasting and postprandial TG levels in very low-density lipoprotein (VLDL) and LDL. Alirocumab improved fasting pulse wave velocity, but no changes in postprandial markers of inflammation were observed. Conclusions: In addition to the well-known LDL-C-reducing effects, 6 weeks of alirocumab treatment lowered both fasting and postprandial plasma TG levels by reducing the TG levels in VLDL and LDL and the concentration of intestinal remnants