Search results for "Dissolution"
showing 10 items of 333 documents
A multi-technique characterisation of cronstedtite synthetized by iron-clay interaction in a step by step cooling procedure
2013
International audience; The cooling of steel containers in radioactive-waste storage was simulated in a step-by-step experiment from 90 to 40 degrees C. Among newly formed clay minerals observed in run products, cronstedtite was identified by a number of analytical techniques (powder X-ray diffraction, transmission electron microscopy, and scanning electron microscopy). Cronstedtite has not previously been recognized to be so abundant and so well crystallized in an iron-clay interaction experiment. The supersaturation of experimental solutions with respect to cronstedtite was due to the availability of Fe and Si in solution, as a result of the dissolution of iron metal powder, quartz, and m…
Effect of Aeration on the Microelectrochemical Characterization of Al[sub 2]Cu Intermetallic Phases
2009
Local probing of the galvanic coupling between micrometer-sized Al 2 Cu phases and the surrounding aluminum-based matrix of a specially heat-treated 2011 alloy is investigated using a microcapillary electrochemical cell. The aging of an isolated Al 2 Cu particle, i.e., selective dissolution of aluminum, is controlled by the aeration condition at the tip of the capillary due to the nature of the silicon membrane used as a gasket. The local electrochemical behavior of an isolated particle after aging confirms the mass transport control of the oxygen reduction on the galvanic coupling of the particle with the surrounding matrix.
Water orientation and hydrogen-bond structure at the fluorite/water interface
2016
AbstractWater in contact with mineral interfaces is important for a variety of different processes. Here, we present a combined theoretical/experimental study which provides a quantitative, molecular-level understanding of the ubiquitous and important CaF2/water interface. Our results show that, at low pH, the surface is positively charged, causing a substantial degree of water ordering. The surface charge originates primarily from the dissolution of fluoride ions, rather than from adsorption of protons to the surface. At high pH we observe the presence of Ca-OH species pointing into the water. These OH groups interact remarkably weakly with the surrounding water and are responsible for the…
Indium Doping in Barium Cerate: the Relation between Local Symmetry and the Formation and Mobility of Protonic Defects
2007
The solid solution series Ba(In,Ce)O3-ä has been investigated with respect to structure, formation, and mobility of protonic defects. Compared to the limited solubility of Y2O3 in BaCeO3 and BaZrO3, the complete solubility of In2O3 is suggested to reflect a relation between absolute hardness of the dopant and the ease of insertion into the hosting lattices. Extended X-ray absorption fine structure (EXAFS) was used to probe the local environment of In3+ in barium cerate: in the surroundings of the dopant, the orthorhombic structure is strongly modified, resulting in an increase of local symmetry. The InO6 octahedra are very regular, and there is no indication for any defect clustering. This …
Spray-Drying, Solvent-Casting and Freeze-Drying Techniques: a Comparative Study on their Suitability for the Enhancement of Drug Dissolution Rates.
2019
Purpose Solid dispersions (SDs) represent the most common formulation technique used to increase the dissolution rate of a drug. In this work, the three most common methods used to prepare SDs, namely spray-drying, solvent-casting and freezedrying, have been compared in order to investigate their effect on increasing drug dissolution rate. Methods Three formulation strategies were used to prepare a polymer mixture of polyvinyl-alcohol (PVA) and maltodextrin (MDX) as SDs loaded with the following three model drugs, all of which possess a poor solubility: Olanzapine, Dexamethasone, and Triamcinolone acetonide. The SDs obtained were analysed and compared in terms of drug particle size, drug-lo…
Resolving Point Defects in the Hydration Structure of Calcite (10.4) with Three-Dimensional Atomic Force Microscopy
2018
It seems natural to assume that defects at mineral surfaces critically influence interfacial processes such as the dissolution and growth of minerals in water. The experimental verification of this claim, however, is challenging and requires real-space methods with utmost spatial resolution, such as atomic force microscopy (AFM). While defects at mineral-water interfaces have been resolved in 2D AFM images before, the perturbation of the surrounding hydration structure has not yet been analyzed experimentally. In this Letter, we demonstrate that point defects on the most stable and naturally abundant calcite (10.4) surface can be resolved using high-resolution 3D AFM-even within the fifth h…
Corrosion resistance of passive films on different stainless steel grades in food and beverage industry
2020
Abstract Passive films were grown on 304 L, 316 L and Duplex stainless steels by immersion at open circuit potential in solutions mimicking food and beverage industry environments. In acidic food stainless steel surfaces are covered by Cr rich passive films, and generalized dissolution occurs on their surface with consequent ions release into the electrolyte. In fatty food the concentration of released ions is significantly lower since generalized corrosion does not occur, but the loss on MnS inclusions strongly reduces the polarization resistance in this environment especially for 304 L due to its higher localized corrosion susceptibility with respect to the other grades.
Cut-edge corrosion of a Zn–55Al-coated steel: A comparison between sulphate and chloride solutions
2011
Abstract Ex situ observations and in situ measurements of current and pH distributions over cut-edge coated steels revealed that Zn–55Al coatings are sacrificial only in chloride solutions, because of an activation of both Zn- and Al-rich phases present in the coating. In sulphate solutions, an efficient cathodic protection occurs only for short times of immersion, because only Zn-rich phases are active in this medium. The low solubility and strong acidification induced by Al(OH)SO4 allows only short distance cathodic protection, but cannot prevent red rust precipitation on the steel surface.
Aqueous Dilution of Noble NPs Bulk Dispersions: Modeling Instability due to Dissolution by AF4 and Stablishing Considerations for Plasmonic Assays
2020
Among different nanomaterials, gold and silver nanoparticles (AuNPs and AgNPs) have become useful tools for a wide variety of applications in general, and particularly for plasmonic assays. Particle size and stability analysis are key elements for their practical applications since the NPs properties depend on these parameters. Hence, in the present work, asymmetrical flow field flow fractionation (AF4) coupled to UV-Vis and dynamic light scattering (DLS) detectors in series, has been evaluated for stability studies of citrate-capped AuNPs and AgNPs aqueous dispersions. First, experimental parameters, such as mobile phase or cross-flow rate were optimized. Sodium azide to pH 7 for AuNPs and…
Mechanism of Heavy Element Retention in Hydrated Layers Formed on Leached Silicate Glasses
1988
ABSTRACTWe have investigated the relationship between hydrated layer formation during aqueous corrosion of silicates and retention of heavy elements (Fe, REE, actinides). Our approach is based on the comparison of the dissolution behaviour of silicate glasses, silicate minerals implanted with increasing doses of lead ions (1×E+12 to 1×E+15 ions/cm2), sorption experiments on silica surfaces and direct precipitation of hydrosilicates. The characterization of reacted surfaces was performed by combining Rutherford backscattering spectrometry (RBS) for profiling heavy elements with Resonant Nuclear Reaction Analysis (RNRA) for hydrogen profilimetry. The accumulation of these elements does not ne…