Search results for "hydroxide"
showing 10 items of 317 documents
A zinc-doped endodontic cement facilitates functional mineralization and stress dissipation at the dentin surface
2018
Objective: The purpose of this study was to evaluate nanohardness and viscoelastic behavior of dentin surfaces treated with two canal sealer cements for dentin remineralization. Material and Methods: Dentin surfaces were subjected to: i) 37% phosphoric acid (PA) or ii) 0.5 M ethylenediaminetetraacetic acid (EDTA) conditioning prior to the application of two experimental hydroxyapatite-based cements, containing sodium hydroxide (calcypatite) or zinc oxide (oxipatite), respectively. Samples were stored in simulated body fluid during 24 h or 21 d. The intertubular and peritubular dentin were evaluated using a nanoindenter to assess nanohardness (Hi). The load/displacement responses were used f…
Layered Double Hydroxides in Bioinspired Nanotechnology
2020
Layered Double Hydroxides (LDHs) are a relevant class of inorganic lamellar nanomaterials that have attracted significant interest in life science-related applications, due to their highly controllable synthesis and high biocompatibility. Under a general point of view, this class of materials might have played an important role for the origin of life on planet Earth, given their ability to adsorb and concentrate life-relevant molecules in sea environments. It has been speculated that the organic–mineral interactions could have permitted to organize the adsorbed molecules, leading to an increase in their local concentration and finally to the emergence of life. Inspired by nature, material s…
Insights into the formation of metal carbon nanocomposites for energy storage using hybrid NiFe layered double hydroxides as precursors
2020
[EN] NiFe-carbon magnetic nanocomposites prepared using hybrid sebacate intercalated layered double hydroxides (LDHs) as precursors are shown to be of interest as supercapacitors. Here, the low-temperature formation mechanism of these materials has been deciphered by means of a combined study using complementaryin situ(temperature-dependent) techniques. Specifically, studies involving X-ray powder diffraction, thermogravimetry coupled to mass spectrometry (TG-MS), statistical Raman spectroscopy (SRS), aberration-corrected scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS) have been carried out. The experimental results confirm the early formation o…
Novel Functionality of Lithium-Impregnated Titania as Nanocatalyst
2019
The present work incorporates the synthesis of a multifunctional catalyst for the transesterification of waste cooking oil (WCO) to biodiesel and recovery of rare earth elements (REEs). For this purpose, TiO2 nanoparticles and TiO2 doped with lithium ions were prepared. The influence of lithium ions on the catalytic performance of TiO2 was attained by impregnation of the different molar ratios of lithium hydroxide to bare TiO2. Then each catalyst was screened for catalytic conversion of WCO to fatty acid methyl ester (FAME) and also for REEs recovery. All synthesized materials were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Transmission electron microsc…
Sepiolite-Hydrogels: Synthesis by Ultrasound Irradiation and Their Use for the Preparation of Functional Clay-Based Nanoarchitectured Materials.
2021
International audience; Sepiolite and palygorskite fibrous clay minerals are 1D silicates featuring unique textural and structural characteristics useful in diverse applications, and in particular as rheological additives. Here we report on the ability of grinded sepiolite to generate highly viscous and stable hydrogels by sonomechanical irradiation (ultrasounds). Adequate drying of such hydrogels leads to low-density xerogels that show extensive fiber disaggregation compared to the starting sepiolite-whose fibers are agglomerated as bundles. Upon re-dispersion in water under high-speed shear, these xerogels show comparable rheological properties to commercially available defibrillated sepi…
Effects of pH on ion transport in weak amphoteric membranes
1997
Abstract We have studied theoretically the effect of pH on the ion transport through amphoteric polymer membranes composed of weak polyelectrolytes where the charged groups are randomly distributed along the axial direction of the membrane. This system serves as a simplified model for the pH controlled ion transport and drug delivery through membranes of biological interest. The theoretical approach employed is based on the Nernst-Planck equations. The complete system of electrical charges formed by: (i) the pH dependent, amphoretic membrane fixed charge, and (ii) the four mobile charges (the salt ions and the hydrogen and hydroxide ions) have been taken into account without any additional …
pH and supporting electrolyte concentration effects on the passive transport of cationic and anionic drugs through fixed charge membranes
1999
Abstract The effects of pH and supporting electrolyte concentration on the passive transport of an ionized (cationic or anionic) drug through a thick fixed charge membrane have been theoretically studied. This system constitutes a simplified model for the pH controlled ion transport and drug delivery through membranes of biological and pharmaceutical interest. Calculations were carried out for different values of the membrane fixed charge, supporting electrolyte and drug concentrations covering a broad range of the conditions usually found in experiments. The theoretical approach employed is based on the Nernst–Planck flux equations, and all of the species present in the system (the neutral…
Removal of algae from biological cultures: a challenge for electrocoagulation?
2014
BACKGROUND In the search for novel technologies for the treatment of urban wastewater, combined anaerobic–algae membrane bioreactors have become a very interesting choice. Recovery of algae produced in these reactors has become the key point to obtain a good economic efficiency with this technology. In this work, electrocoagulation is studied as an alternative for the coarse removal of algae from a biological culture. RESULTS Results demonstrate that the electrochemical technology is a suitable technology for this purpose allowing the removal of more than 90% of the algae without modifying significantly the pH and with an operating cost below 0.04 € m−3. The same general trends are observed…
Magneto-structural correlations in Ni(ii) [2 × 2] metallogrids featuring a variable number of μ-aquo or μ-hydroxo extra bridges
2019
Four new [2 × 2] grid-type metallosupramolecular species have been obtained by using the ditopic 3,6-bis(2′-pyridyl)pyridazine ligand (dppn) and nickel(II) salts containing poorly coordinating anions. Three of them have the formula [Ni4(μ-dppn)4(μ-OH)2(μ-H2O)2]X6·nH2O [with X = ClO4− (1), NO3− (2) and CF3SO3− (3), and n = 6.5 (1), 14 (2) and 4 (3)]. Their crystal structure shows the same tetranuclear core, constituted by four six-coordinate metal ions and four dppn molecules. Two hydroxo groups and two water molecules efficiently interact forming two hydrated hydroxide (H3O2−) supramolecular bridging anions, further stabilizing the grid. The other compound, [Ni4(μ-dppn)4(μ-OH)3(μ-H2O)](ClO4…
ChemInform Abstract: Magnetic Properties of NiIICrIIILayered Double Hydroxide Materials.
2009
This paper describes the isolation of four layered double hydroxide (LDH) compounds having the general formula[NiII3–xCrIIIx(OH)6](CO3)x/2·yH2O [x = 0.57 (1), 0.69 (2), 0.81 (3) and 0.93 (4)] by using homogeneous precipitation methods and varying the metal ratio in the synthetic solutions. All the reported compounds have carbonate anions in the interlamellar space. This fact forces the interlayer distances to remain unchanged in all the cases, thus providing an ideal system in which the changes observed in magnetic properties can be correlated with metal composition along the hydroxide layers.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)