Search results for "composite"

Electrochemistry of TiO2–iron hexacyanocobaltate composite electrodes

2014

Abstract In this paper we investigate the electrochemical behavior of iron hexacyanocobaltate (FeHCC) in comparison to the cobalt hexacyanoferrate (CoHCF). The best results were achieved on electrochemical synthesized film of FeHCC on the TiO2 modified electrodes. The chemical and physical characterizations confirm the formation of the FeHCC with the classical cubic crystal structure of the Prussian blue analogs, with cell parameter a very close to 10 A, as well as the formation of micro aggregates of TiO2 covered by FeHCC. The synthesis was performed on various substrates such as glassy carbon (GC), graphite foil (GF) and indium tin oxide (ITO) in order to develop new technological applica…

Experimental investigation on the effectiveness of basalt-fibre strengthening systems for confining masonry elements

L’impiego di materiali compositi per il rinforzo di colonne in muratura è diventato una pratica ampiamente diffusa nel corso degli ultimi decenni. Questa tecnica, che consiste generalmente nell’applicazione di materiali polimerici fibrorinforzati (Fibre Reinforced Polymer-FRP), ha mostrato buone potenzialità, essendo in grado di garantire notevoli incrementi di resistenza e duttilità dell’elemento rinforzato, grazie ad un’azione di confinamento passivo. Tuttavia, l’impiego di compositi a matrice polimerica presenta alcuni limiti legati soprattutto alle prestazioni delle resine epossidiche, che a causa della loro natura sintetica danno luogo a problemi di compatibilità con il supporto murari…

Pb(II) adsorption by a novel activated carbon - alginate composite material. A kinetic and equilibrium study.

2016

The adsorption capacity of an activated carbon – calcium alginate composite material (ACAA-Ca) has been tested with the aim of developing a new and more efficient adsorbent material to remove Pb(II) ion from aqueous solution. The study was carried out at pH = 5, in NaCl medium and in the ionic strength range 0.1–0.75 mol L−1. Differential Pulse Anodic Stripping Voltammetry (DP-ASV) technique was used to check the amount of Pb(II) ion removed during kinetic and equilibrium experiments. Different kinetic (pseudo first order, pseudo second order and Vermuelen) and equilibrium (Langmuir and Freundlich) models were used to fit experimental data, and were statistically compared. Calcium alginate …

Microwave response properties of epoxy resin composites filled with graphitic fillers

2014

Composite materials based on epoxy resin filled with various kinds of graphite particles: exfoliated graphite (EG), natural graphite, and coarse, medium and fine artificial graphites have been prepared. The dielectric permittivity strongly increases with graphite particle size. This effect is related to the distance of the investigated filler concentrations to the composites' percolation threshold. Microwave experiments show that exfoliated graphite is, out of investigated graphite particles, the only one being a really effective additive for producing electromagnetic (EM) interference (EMI) shielding: 2 wt.% epoxy/EG is absolutely opaque to electromagnetic radiation at 30 GHz.

Synthesis, Characterization and Catalytic Activity of mesoporous Mn-MCM-41 materials

2011

MCM-41 has been synthesized at two different pH using cetyl-trimethylammonium bromide (CTAB) surfactant as template and adding the silica precursor to aqueous solutions containing CTAB. The obtained solids were calcined at 600 ◦C for 4 h. Mn-MCM-41 powders with different Mn/Si molar ratios were prepared using the incipient wetness method, followed by calcination at 550 ◦C for 5 h. At the end of the impregnation process the powders colour changed from white to brown whose intensity depends on manganese quantity. The materials characterization was performed by X-ray diffraction, N2 adsorption, 29Si Cross Polarization–Magic Angle Spinning NMR, and X-ray Photoelectron Spectroscopy. The effects …

Preparation and characterisation of Ce:YAG -polycarbonate composites for white LED

2016

Ce:YAG-polycarbonate composites were prepared with several amounts of Ce:YAG in the range 0.1-5 wt.% by using melt compounding. The structure and morphology of the composites were investigated by means of X-ray diffractometry and transmission electron microscopy. The optical properties of the composites were studied by using photoluminescence spectroscopy. The intermolecular interaction between the polymer and the filler surface was investigated using 13C cross-polarization magic-angle spinning NMR spectroscopy (13C {1H} CP-MAS NMR). The results showed that the dispersion of the particles in the polymer, and the optical properties, depend on the Ce:YAG amount. The composites were combined w…

Discontinuous Galerkin models for composite multilayered shells with higher order kinematics

2021

Composite multilayered shells are widely employed in aerospace, automotive and civil engineering as weight-saving structural components. In multilayered shells, despite its versatility, the interplay between the curved geometry and the properties of the composite layers induces a complex distribution of the mechanical fields, which must be accurately resolved to safely employ generally curved composite shells as load-bearing structures. The problem can be addressed through the two-dimensional shell theories, which are based on suitable assumptions on the behavior of the mechanical fields throughout the thickness of the considered structures and are a viable strategy for reducing the computa…

Optimal design of flax fiber reinforced polymer composite as a lightweight component for automobiles from a life cycle assessment perspective

2019

The present study combines the generalized rule-of-mixture (ROM) model and the Ashby material selection method for the life cycle assessment (LCA) of flax fiber reinforced polymers (FRPs) and glass FRPs (GFRPs). The ROM model allows life cycle environmental impact predictions according to specific parameters of flax FRPs such as fiber format, volume fraction, manufacturing technique, and load-bearing capacity. The comparisons applied in this study are constructed on two common composite structures: mat panels and injection molded struts with equal stiffness and strength as the design criteria. On the one hand, the parametric LCA predicts that the equal strength design criterion for flax FRP…

Marginal integrity of low-shrinkage and methacrylate-based composite resins: Effect of three different hemostatic agents.

2015

Background: Moisture control is very important in restorative procedures in dentistry. Use of hemostatic agents helps control moisture; however, they might result in changes on enamel and dentin surfaces, affecting composite resin bond quality. The aim of this in vitro study was to evaluate the marginal microleakage of two different composite resins with the use of three different hemostatic agents. Material and Methods: Standardized Class V cavities were prepared on the buccal and lingual surfaces of 48 premolars with cervical margins 1 mm apical to the cementoenamel junction (CEJ). The samples were randomly divided into 8 groups. In groups 1 to 4, an etch-and-rinse adhesive (Adper Single …

Polydimethylsiloxane composites containing 1,2-naphtoquinone 4-sulphonate as unique dispositive for estimation of casein in effluents from dairy indu…

2015

A unique dispositive to determine casein which is the most abundant protein in dairy sewages has been proposed. In this sensing technology, the derivatization reagent 1,2-naphtoquininone 4-sulphonate (NQS) is embedded into a polydimethylsiloxane-tetraethylortosilicate-SiO2 nanoparticles composite (PDMS-TEOS-SiO2NPs). When the composite is immersed into the samples, casein is extracted from the solution and derivatized inside the PDMS matrix after 10 min at 100°C. The sensing support changes its color from yellow to orange depending on the casein concentration. Quantitative analysis can be carried out by measuring the absorbance with a reflection probe or by image-processing tool (GIMP). Thi…