Search results for " Silicate"
showing 10 items of 126 documents
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.
Intermediate Range Order in Silicate Melts and Glasses: Computer Simulation Studies
2002
ABSTRACTWe present the results of large scale computer simulations to discuss the structural and dynamic properties of silicate melts with the compositions (Na2O)(2·SiO2), (Na2O)(20·SiO2) and (Al2O3)(2·SiO2). We show that these systems exhibit additional intermediate range order as compared to silica (SiO2) where the characteristic intermediate length scales stem from the tetrahedral network structure. Furthermore we show that the sodium dynamics in the sodium silicate systems exhibits a very peculiar feature: the long–time decay of the incoherent intermediate scattering function can be described by a Kohlrausch law with a constant exponent β for q > qth whereby qth is smaller than the l…
The dynamics of melts containing mobile ions: computer simulations of sodium silicates
2003
We present the results of large-scale computer simulations in order to discuss the structural and dynamic properties of sodium silicate melts with the compositions (Na2O)2(SiO2) (NS2) and (Na2O)20(SiO2) (NS20). We show that, compared to silica (SiO2), these systems exhibit additional intermediate range order on intermediate length scales that stem from the tetrahedral network structure. By means of intermediate-scattering functions, we characterize the dynamics of sodium in the system under consideration. Whereas in NS2 the incoherent scattering functions for Na decay much faster to zero than the coherent ones for Na–Na, in NS20 this different behaviour of the incoherent and coherent functi…
Remineralization ability of two hydraulic calcium-silicate based dental pulp capping materials: Cell-independent model
2019
Background This study aimed to evaluate remineralizing ability of two hydraulic calcium-silicate cements (Biodentine and TheraCal LC). Material and Methods Artificial carious lesions were introduced into the pulpal floors (1-1.5 mm) and axial walls of occlusal prepared cavity halves through pH cycling. Cycling was made through demineralizing solution (pH 3), for 8 hours and remineralizing solution (pH 7) for 16 hours. The total period of pH cycling was 14 days. Prepared cavities with the tested materials seated directly on the pulpal floor and in contact with the axial walls were stored in phosphate buffer solutions (PBS) (pH 7.2–7.4). The changes in the weight percentages (wt%) of calcium …
Retrograde filling material in periapical surgery: a systematic review
2021
Background Periapical surgery focuses on the treatment of teeth with persistent periapical lesions when orthograde root canal treatment fails. Although MTA® is the gold standard material for retrograde filling, Biodentine® - a tricalcium silicate-based cement - has been proposed in order to resolve several of its limitations. A systematic review has been carried out to compare the physicochemical properties of Biodentine® versus MTA® as root-end filling material in periapical surgery. Material and Methods An electronic search was conducted by two independent examiners during March 2020 in the Cochrane, PubMed-MEDLINE and Scopus databases. In addition, a manual search was made in specialized…
Comparative Cytocompatibility and Mineralization Potential of Bio-C Sealer and TotalFill BC Sealer
2019
The aim of this study was to investigate the cytocompatibility and mineralization potential of two premixed hydraulic endodontic sealers compared with an epoxy resin-based root canal sealer. The cellular responses and mineralization capacity were studied in human periodontal ligament stem cells (hPDLSCs) that were exposed to premixed hydraulic sealers, Bio-C Sealer (Angelus, Londrí
Transport of Mobile Particles in an Immobile Environment: Computer Simulations of Sodium Silicates
2007
Molecular dynamics (MD) simulations of various sodium silicate melts, (Na2O)x(SiO2) with x=2, 3, 20, are presented. In these systems, the mobility of sodium ions is much higher, often by orders of magnitude, than that of the silicon and oxygen atoms forming a tetrahedral network structure. We show that the high mobility of sodium is intimately related to the chemical ordering in sodium silicates. A network of percolating sodium-rich channels is formed in the static structure that serve as diffusion channels for the sodium ions. This channel network is revealed in static structure factors by a prepeak at the wavenumber q=0.95 A-1. Inelastic neutron scattering experiments of sodium silicate m…
Lithium silicate admixture in mortars to be used as putty for limestone
2018
Marble is a very common material in artworks for its softness, relative isotropy and homogeneity and its characteristic waxy look that gives "life" to sculptures. Even if in geology the term "marble" refers to metamorphosed limestone, commonly the term ‘marble’ is used more broadly encompassing hard unmetamorphosed limestone that can be polished assuming a glossy aspect. In the restoration field when marble artworks have cracks that alter the smoothness of their surface, a putty is used to fill them, for both aesthetic and conservative reasons. Putties usually consist of epoxy resin mixed with marble powder. The use of a synthetic resin raises some doubts on compatibility and durability of …
Silicate and Hydroxide Concentration Influencing the Properties of Composite Al2O3-TiO2 PEO Coatings on AA7075 Alloy
2021
This work evaluates the effect of sodium meta-silicate pentahydrate (SMS) and potassium hydroxide concentrations on properties of Al2O3-TiO2 coatings produced through plasma electrolytic oxidation in a solution containing 3 g L−1 potassium titanyl oxalate, (PTO), using a unipolar waveform with constant current density. The surface and cross-section characteristics of PEO coatings including morphology, elemental distribution, and phase composition were evaluated using FESEM, EDS, and XRD techniques. Voltage-time response indicated the concentration of SMS and KOH had a significant effect on the duration of each stage of the PEO process. More cracks and pores were formed at the higher concent…
Control of the pore wall thickness and thermal stability in low-cost bimodal porous silicas
2019
Abstract A new hierarchical bimodal mesoporous silica, labelled as UVM-12 (acronym of University of Valencia Materials), has been prepared by using a solution of sodium silicate as low-cost silicon source. The final self-assembling between cationic micelles of CTAB and anionic inorganic Si-based oligomers occurs in a homogeneous aqueous medium. The reaction is carried out from low-sized building blocks through a bottom-up approach. The UVM-12 solids combine two mesopore systems according to N2 adsorption–desorption isotherms, what is corroborated by TEM micrographs and XRD patterns. This material has been inorganically modified by incorporation of Al or Ti (M-UVM-12, M = Al, Ti) without alt…