Search results for "silica."
showing 10 items of 1087 documents
NO2-controlled cargo delivery from gated silica mesoporous nanoparticles
2017
[EN] Cargo delivery from mesoporous silica nanoparticles loaded with sulforhodamine B and capped with a difluoroboron-dipyrromethene (BODIPY) derivative was triggered by a NO2-induced oxidative process.
Influence of low amounts of nanostructured silica and calcium carbonate fillers on the large-area dielectric breakdown performance of bi-axially orie…
2014
Influence of low amounts (1.0-2.0wt-%) of nanostructured silica and calcium carbonate fillers on the large area dielectric breakdown performance of bi-axially oriented polypropylene (BOPP) is analyzed. A multi-breakdown measurement method based on the self-healing breakdown capability of metallized film is utilized for the breakdown characterization in order to cover relatively large total film areas, thus leading to results of higher relevance from the practical point-of-view. The dispersion and distribution qualities of filler particles at the nanoscale are evaluated with transmission electron microscopy (TEM) imaging. Weibull statistical analysis suggests that the breakdown distribution …
Application of 29Si Homonuclear and 1H−29Si Heteronuclear NMR Correlation to Structural Studies of Calcium Silicate Hydrates
2004
Structural characterization of calcium silicate hydrate (C-S-H) is of major importance, as it is the main constituent of Portland cement and is responsible for its principal cohesion and durability...
Elucidation of reaction process between solid tricalcium silicate and a lanthanum salt solution in connection with the precipitation pH. Extension to…
1993
Abstract Dissolution of tricalcium silicate is strongly accelerated in a La salt solution and releases the amounts of OH, Ca and silicate ions just required to precipitate all of lanthanum at pH 8. It remained to be proved that (1) La silicate hydrate could form at pH 8, and (2) Ca silicate hydrate could not precipitate simultaneously. The plot of silicate hydrate and hydroxide precipitation pH of La, Ca and other elements (Th, Zr) against the dropped volume of K2SiO3 and KOH solution and some physico-chemical characterization methods bring affirmative answers to these questions and allow the immobilization process of La and other elements in the presence of tricalcium silicate to be better…
Aging of MCM41, MSU-H and MSU-F mesoporous systems investigated through the Raman spectroscopy
2014
Here we report an experimental investigation, based on the Raman spectroscopy, on the aging of some mesoporous silica based systems. In details, we studied the aging in air of the MCM41, the MSU-H and the MSU-F materials by acquiring the Raman spectra of as received and of mechanically pressed, at 0.2 and 0.45 GPa, powders. Our data evidenced that the starting powders of the MCM41 and of the MSU-H undergo structural modification when they are exposed to the ambient atmosphere, such modification consisting in the decrease of the D2 Raman band (originated by the three member rings). At variance the powders of the MSU-F appear to be stable. Furthermore, by pressing the starting powders to prod…
Agglomerated non-porous silica nanoparticles as model carriers in polyethylene synthesis
2004
Abstract Non-porous submicron silica particles (250 and 500 nm) with high monodispersity were agglomerated to form spherical agglomerates via spray drying. As a binder, 25 nm sized monodisperse silica spheres were selected from a variety of colloidal systems including Levasil-type and Aerosil-type silica nanoparticles. The use of such binders led to an increase of the specific surface area of the agglomerated carriers. All materials were characterised by nitrogen sorption, mercury intrusion and scanning electron microscopy. The silica agglomerates, with highly defined geometrical and pore structural parameters, were employed as model carriers in the heterogeneous polymerization of ethylene …
Caspase 3 Targeted Cargo Delivery in Apoptotic Cells Using Capped Mesoporous Silica Nanoparticles
2015
[EN] Excessive apoptotic cell death is at the origin of several pathologies, such as degenerative disorders, stroke or ischemia-reperfusion damage. In this context, strategies to improve inhibition of apoptosis and other types of cell death are of interest and may represent a pharmacological opportunity for the treatment of cell-death-related disorders. In this scenario new peptide-containing delivery systems (solids S1-P1and S1-P2) are described based on meso-porous silica nanoparticles (MSNs) loaded with a dye and capped with the KKGDEVDKKARDEVDK (P1) peptide that contains two repeats of the DEVD target sequence that are selectively hydrolyzed by caspase3 (C3). This enzyme plays a central…
Bonding to silicate ceramics : conventional technique compared with a simplified technique
2017
Background Silicate ceramic bonding is carried out by acid-etching with hydrofluoric acid (HF) followed by an application of silane. By replacing HF with ammonium polyfluoride, contained in the same flask as the silane, the number of steps in this clinical procedure, can be reduced, while maintaining bond strength values, and reducing toxicity. A shear bond test was performed to compare the conventional and the simplified surface treatment techniques. Material and methods Twenty ceramic samples were fabricated from IPS emax CAD® ceramic (Ivoclar Vivadent) and divided into two groups (G1 and G2) (n=10). The conventional technique was applied to G1 samples, and the simplified technique to G2 …
A new hydrous Al-bearing pyroxene as a water carrier in subduction zones
2011
Abstract A new Hydrous Al-bearing PYroxene (HAPY) phase has been synthesized at 5.4 GPa, 720 °C in the MgO–Al2O3–SiO2–H2O model system. It has the composition Mg2.1Al0.9(OH)2Al0.9Si1.1O6, a C-centered monoclinic cell with a = 9.8827(2), b = 11.6254(2) c = 5.0828(1) A and β = 111.07(1)°. The calculated density is 3.175 g/cm3 and the water content is 6.9% H2O by weight. Its structure has been solved in space group C2/c by the recently developed automated electron diffraction tomography method and refined by synchrotron X-ray powder diffraction. HAPY is a single chain inosilicate very similar to pyroxenes but with three instead of two cations in the octahedral layer, bonded to four oxygens and…
A New Monte Carlo Method for the Titration of Molecules and Minerals
2007
The charge state of molecules and solid/liquid interfaces is of paramount importance in the understanding of the reactivity and the physico-chemical properties of many systems. In this work, we porpose a new Monte Carlo method in the grand canonical ensemble using the primitive model, which allows us to simulate the titration behavior of macromolecules or solids at constant pH. The method is applied to the charging process of colloidal silica particles dispersed in a sodium salt solution for various concentrations and calcium silicate hydrate nano-particles in a calcium hydroxide solution. An excellent agreement is found between the experimental and simulated results.