Search results for "Dissolution"

The use of local electrochemical probes and surface analysis methods to study the electrochemical behaviour and pitting corrosion of stainless steels

2007

Abstract In this paper, the electrochemical microcell technique is combined with ex situ (SIMS and XPS) and in situ (SVET) techniques to study the electrochemical behaviour and pitting corrosion of inclusion-contaning stainless steels. Dissolution of metallurgical heterogeneities, depassivation and pitting mechanisms are first discussed in 1 M NaClO4, pH 3, and 1 M NaCl, pH 3, by considering the chemical composition and morphology of inclusions. The influence of the chemical composition of passive films on the electrochemical reactions and the microgalvanic coupling processes occurring at the corrosion potential is also investigated on the same specimen microstructure.

Karstic overprint of Upper Triassic peritidal cycles: The example of the Panormide Carbonate Platform at San Vito lo Capo (Sicily)

2012

Processi paleocarsici e geositi: il caso del “libeccio antico” nel distretto marmifero di Custonaci, Sicilia nord-occidentale

2016

Abstract The Upper Triassic strata that crops out along the northern slope of Monte Sparagio, in the Custonaci “marble” district in northwestern Sicily, show an extensive development of dissolution cavities with a very variable shape and dimensions. Several different types of dissolution morphologies can be differentiated from microkarst to giant caverns. The cavities are filled up by polychrome silts or calcite cements or, in the larger caverns, by collapse breccias. The matrix between the collapse breccias is a polychrome silt that gives rise to an attractive ornamental stone, quarried in the past with the name of “Libeccio Antico”. The diagenetic processes that have controlled the format…

Mine sinkhole in Siciliy: geomorphologic and environment hazard

2009

Molecular Biomineralization: Toward an Understanding of the Biogenic Origin of Polymetallic Nodules, Seamount Crusts, and Hydrothermal Vents

2011

Polymetallic nodules and crusts, hydrothermal vents from the Deep Sea are economically interesting, since they contain alloying components, e.g., manganese or cobalt, that are used in the production of special steels; in addition, they contain rare metals applied for plasma screens, for magnets in hard disks, or in hybrid car motors. While hydrothermal vents can regenerate in weeks, polymetallic nodules and seamount crusts grow slowly. Even though the geochemical basis for the growth of the nodules and crusts has been well studied, the contribution of microorganisms to the formation of these minerals remained obscure. Recent HR-SEM (high-resolution scanning electron microscopy) analyses of …

Degradation of silica particles functionalised with essential oil components under simulated physiological conditions

2020

[EN] In this work, the biodurability of three silica particle types (synthetic amourphous silica, MCM-41 microparticles, MCM-41 nanoparticles) functionalised with three different essential oil components (carvacrol, eugenol, vanillin) was studied under conditions that represented the human gastrointestinal tract and lysosomal fluid. The effect of particle type, surface immobilised component and mass quantity on the physico-chemical properties of particles and silicon dissolution was determined. Exposure to biological fluids did not bring about changes in the zeta potential values or particle size distribution of the bare or functionalised materials, but the in vitro digestion process partia…

Effect of the dissolution time into an acid hydrolytic solvent to tailor electrospun nanofibrous polycaprolactone scaffolds

2017

[EN] The hydrolysis of the polycaprolactone (PCL) as a function of the dissolution time in a formic/acetic acid mixture was considered as a method for tailoring the morphology of nanofibrous PCL scaffolds. Hence the aim of this research was to establish a correlation between the dissolution time of the polymer in the acid solvent with the physicochemical properties of the electrospun nanofibrous scaffolds and their further service life behaviour. The physico-chemical properties of the scaffolds were assessed in terms of fibre morphology molar mass and thermal behaviour. A reduction of the molar mass and the lamellar thickness as well as an increase of the crystallinity degree were observed …

Changes in fluid geochemistry and physico-chemical conditions of geothermal systems caused by magmatic input: The recent abrupt outgassing off the is…

2005

Abstract Hydrothermal systems and related vents can exhibit dramatic changes in their physico-chemical conditions over time as a response to varying activity in the feeding magmatic systems. Massive steam condensation and gas scrubbing processes of thermal fluids during their ascent and cooling cause further compositional changes that mask information regarding the conditions evolving at depth in the hydrothermal system. Here we propose a new stability diagram based on the CO2-CH4-CO-H2 concentrations in vapor, which aims at calculating the temperatures and pressures in hydrothermal reservoirs. To filter gas scrubbing effects, we have also developed a model for selective dissolution of CO2-…

Bioorganic/inorganic hybrid composition of sponge spicules: matrix of the giant spicules and of the comitalia of the deep sea hexactinellid Monorhaph…

2007

The giant basal spicules of the siliceous sponges Monorhaphis chuni and Monorhaphis intermedia (Hexactinellida) represent the largest biosilica structures on earth (up to 3 m long). Here we describe the construction (lamellar organization) of these spicules and of the comitalia and highlight their organic matrix in order to understand their mechanical properties. The spicules display three distinct regions built of biosilica: (i) the outer lamellar zone (radius: >300 mu m), (ii) the bulky axial cylinder (radius: <75 mu m), and (iii) the central axial canal (diameter: <2 mu m) with its organic axial filament. The spicules are loosely covered with a collagen net which is regularly perforated …

Dry adsorbed emulsion: 2. Dissolution behaviour of an intricate formulation

2002

The behaviour of a pharmaceutical form, called dry adsorbed emulsion (DAE), containing a sparingly soluble drug (i.e. theophylline) was studied for dissolution drug release kinetic, in relation with DAE structure characterisation. In vitro dissolution testings were performed under different experimental conditions (medium at pH 1.2 and 7.4, medium with or without surfactant addition, different particle sizes, discrete or densified particles). Discrete DAE particles showed an extended release, in comparison with the native drug powder, depending on both drug solubility in the medium and particle size. The relevance of dissolution data was not improved by surfactant addition (0.1% sodium laur…