Effect Of Silica Addition Research Articles

Effect of silica addition on the photocatalytic activity of MO2@SiO2 (M=Ti, Zr, Sn, Ce) nanocomposites prepared by sol-gel

AbstractPhotocatalysis uses wide band gap ceramic semiconductors (anatase, zirconia, ceria, cassiterite…) that have the ability to promote electron-hole pairs by UV light irradiation producing both reducing and oxidants ions and radicals. In general, oxidizing species are more efficient, using photocatalysis as an advanced oxidation process (AOP) for the biodegradation of organic substances refractory to conventional treatments, such as azo dyes, or atmospheric pollutants as NOx. In this communication, the photocatalytic activity of xSiO2@(1-x)MO2 (M = TiO2, ZrO2, SnO2, CeO2, x = 0, 0.1, 0.3 and 0.5) composites on the Orange II azo dye in solution, as well as on NOx in air, was analysed. The composites were obtained by Sol-Gel methods based on the hydrolysis-condensation of alcoholic solutions of silicon tetraethoxide (TEOS) and titanium n-butoxide, zirconium iso-propoxide, SnCl2.2H2O and Ce(NO3)3.6H2O as precursors of MO2 oxides. The resulting xerogels were studied by XRD, bandgap measurements from UV-Vis-NIR diffuse reflectance spectroscopy, photocatalytic activity against Orange II in dissolution and NOx in air (efficiency in nitrate abatement), and SEM-EDX microstructural analysis. In the case of non-stabilized samples, charring samples at 300 °C/1 h and fired samples at 500 °C/1 h were also studied. The cassiterite-silica composite stands out for its photocatalytic activity against Orange II in solution and the cerianite-silica composite against NOx in air. Silica increases the photocatalytic activity on NOx in zirconia, tin oxide and ceria composites and also on Orange II in zirconia and tin oxide. Graphical Abstract

Effect of Silica Addition on Lead Ion Adsorption Ability of Alkali-Activated Blast Furnace Slag

Effect of Silica Addition on Lead Ion Adsorption Ability of Alkali-Activated Blast Furnace Slag

The effect of silica addition on dielectric properties of barium titanate nanoparticles

The effect of silicon dioxide (SiO2) nanoparticles on the dielectric constant was studied. Different weight percentages of silica (3, 5, and 7 %) were added to BaTiO3 nanoparticles. The structure, morphology, and dielectric properties were obtained using X-ray diffraction (XRD) and scanning electron microscopy (SEM), and an LCR meter. The diffraction patterns were shown that the crystallite size of BaTiO3 increased with the addition of SiO2. The dielectric constant and the dielectric loss were measured with various temperatures ranging from 27 to 180 °C at a constant frequency of 10 kHz. It was found that the value of the dielectric constant for the pure BaTiO3 is the highest at the Curie temperature (128 °C). The Curie temperature shifted to a higher value and the dielectric constant was decreased when the silica was added to BaTiO3. Moreover, with increasing the silica percentage, the variation in the dielectric loss values with the temperature was observed.

Effect of silica addition on microstructure, sintering behavior, and dielectric properties of borosilicate glass/alumina composites for LTCC application

Effect of silica addition on microstructure, sintering behavior, and dielectric properties of borosilicate glass/alumina composites for LTCC application

Evaluation the Effects of Waste Glass Powder Mixed with Hydrated Lime on the Unconfined Compressive Strength of Clayey Soil

Stabilization of clayey soil is commonly used to enhance unfavorable engineering properties. The effects of silica additives on soil improvement have been considered recently, and documented research studies on the characteristics of problematic clays stabilized by silica additives are interesting for many researchers. Alternative waste disposal strategies that would be both economically beneficial and environmentally friendly have been identified by this study. In the present study, waste silica-based addition is used to stabilize clayey soil, and the time-dependent changes in strength properties are investigated. Unconfined compressive strength (UCS) tests were conducted on stabilized samples at various curing durations to investigate macro-level properties. The UCS test results revealed that the 7.5% of GP+ 5% L content was optimal for the clayey soil as the strength was increased by 166.06%. The addition of the glass powder with hydrated lime components to the clayey soil resulted in stabilized samples, indicating a dense and compact matrix and reduced soil porosity, which increased the mechanical strength, according to the SEM analysis. This curing reaction technique is very beneficial and economical for geotechnical engineering applications.

Feasibility study on the use of magnetic susceptibility for recovery of vanadium component in magnetite

ABSTRACT Vanadium in the vanadium-bearing titanomagnetite (VTM) exist by replacing iron in the magnetite crystal, and magnetite should be recovered separately from titanium components in the vanadium-bearing titanomagnetite. In the present study, a sensing system was proposed by measuring magnetic susceptibility of magnetite because the magnetic susceptibility can be easily and quickly measured. The effects of mixing ratio of magnetite and ilmenite with silica and the distance between the magnetic susceptibility meter and the sample bed on the magnetic susceptibility were investigated. The magnetic susceptibility of the mixture of magnetite and ilmenite with 0.1 g or 0.2 g of silica decreased with increasing the ratio of ilmenite in the mixture, but the effect of silica addition was not significant. When the distance between the magnetic susceptibility meter and the sample bed increased, the magnetic susceptibility of magnetite decreased, but the magnetic susceptibility decreased with increasing the thickness of magnetite sample bed of magnetite. Because the magnetic susceptibility depended strongly on the content of magnetite, the sensing system using the magnetic susceptibility measurement could be successfully applied to detect magnetite.

Effect of Silica Addition to Resin on Fiber Matrix Interfacial Shear Strength of Carbon Fiber Reinforced Polyamide Resin at High Temperature

Effect of Silica Addition to Resin on Fiber Matrix Interfacial Shear Strength of Carbon Fiber Reinforced Polyamide Resin at High Temperature

Effect of Silica Addition on Mechanical Properties of Eggshell-Derived Hydroxyapatite

Eggshell is a solid waste that is available in abundance but is being left unused. Eggshell containing calcium in a high amount. Calcium can be used as a precursor for hydroxyapatite (HAp). Modification of HAp with SiO2 is expected to improve its low mechanical properties for biomedical applications. In this study, HAp is synthesized from the eggshell. Then, it was modified by adding SiO2 utilizing the coprecipitation method with concentrations of 10%, 20%, 30%, and 40%, respectively. The HAp and HAp/SiO2 were characterized using; X-ray diffraction and Fourier transform infrared spectroscopy. The analysis HAp and HAp/SiO2 were density, compressive strength, and hardness. The best mechanical properties of HAp/SiO2 were characterized using SEM-EDS. The HAp were prepared successfully with a ratio of Ca/P was 1.673, close to the theoretical 1.67. The addition of SiO2 caused a decrease in crystallite size and density but increased compressive strength and hardness. The best mechanical properties of HAp/SiO2 were obtained with SiO2 of 30% and 40% with similar values.

Thickness controlled SiO2/TiO2 sol-gel coating by spraying

SiO2/TiO2 composite sol-gel coatings can be used in many industrial applications for their self-cleaning and photocatalytic properties. In this study, SiO2/TiO2 composite sol-gel coatings were deposited by spray coating as it allows a better thickness control than dip coating, which is now mostly used. The most critical spray coating parameters were first determined by a fractional factorial experimental design for a TiO2 sol coating. Then, the effect of silica addition in combination with a hydrophobic precursor on the thickness, the water contact angle and the adhesion strength of the coatings was studied.The most critical spray parameters for controlling the thickness of the coating were the reservoir pressure and the height of the spray gun above the substrate, while the atomisation pressure had almost no effect. A thin coating can be obtained by using a great height in combination with a low reservoir pressure.

The effects of silica addition on the structural, electrical and mechanical characteristics of MgAl2O4 spinel ceramic phase

The ceramic compound Mg1-xSixAl2O4 (x= 0, 0.1, 0.2, 0.3, 0.4) was prepared from nano powder of Al2O3 and MgO doped with Nano powder of SiO2 at different molar ratios. The specimens were prepared by standard chemical solid reaction technique and sintered at 1450 oC. Structure of the specimens was analyzed by using X-ray diffraction (XRD). The X-ray patterns of the specimens showed the formation of pure simple cubic spinel structure MgAl2O4 phase with space group of ̅ . The average grain size and surface topology were studied by atomic force microscopy. The results showed that the average grain size was about 73-90 nm. The DC electrical properties of the specimen were measured. The apparent density was found to increase and the porosity and water absorption were found to decrease with increase of Si addition. Mechanical properties were characterized by Vicker’s micro hardness and Brazilian fracture test to measure the fracture toughness of the samples. The micro hardness decreased with Si addition increase. Fracture toughness increased with the increase in Si addition.

Corrosion studies of rebar in contact with saturated solution produced by leaching of Portland Type-II cement: examining the effects of chloride, carbonation and an amorphous silica additive

ABSTRACTThis study examined the effects of silica addition on electrochemical behavior of rebar in native pH 12.5 saturated solutions prepared by leaching of Portland Type-II cement, and in solutions reduced by CO2 to pH 9. Cyclic polarizations showed that at pH 12.5 the silica additive increased the threshold concentration required for pitting from 100 to 105mM, and from 0.3 mM to 0.5 mM at pH 9. Passivation kinetic exponents were consistently larger for solutions with either pH when silica was present. The silica additive provided the passive film with generally increased resistance and lower capacitance, as confirmed by electrochemical impedance spectroscopy. Charge carrier densities calculated from Mott-Schottky plots were on the order of 1020 (cm-3), increasing significantly after the passive film breakdown. Raman spectroscopy of rebar samples immersed in saturated cement solutions showed films predominantly composed of iron oxyhydroxides with a new shoulder attributed to amorphous silica.

Effects of silica addition on chromium distribution in stainless-steel slag

ABSTRACTThe present study was aimed at highlighting the effect of silica on chromium distribution and enrichment in certain stainless-steel slag when basicity ranged from 0.96 to 1.96. Industrial slag samples of the CaO–Al2O3–MgO–SiO2–CrOX–FeXO system were investigated with different silica addition contents and soaked at the targeted regime. X-ray diffraction, electron probe micro-analyzer with wavelength-dispersive X-ray spectrometer, as well as Fourier-transform infrared spectroscopy and NIH ImageJ software were used for sample characterisation. FactSage version 6.4 was employed to calculate phase equilibria at 1200°C for the slag system to understand the crystallisation procedure. Results indicated that chromium was enriched in CaCr2O4 at high basicity, but in spinel at lower basicity. The spinel phase increased in size and chromium distribution with Fe(II) participated in growth with the decrease in depolymerisation of the slag structure.

Effects of silica additives on fracture properties of carbon nanotube and carbon fiber reinforced Portland cement mortar

Fiber reinforcements provide many benefits to cementitious composites, including reduction of crack widths and increases in ductility. However, the interfacial transition zone between fibers and hydrated cement can contain a high proportion of calcium hydroxide and porosity. With their high moduli of elasticity, carbon nanotubes and carbon fibers could provide substantial mechanical reinforcement at multiple length scales, but only if their bond to the matrix can be controlled. Surface treatments of fibers and addition of supplemental materials in the matrix can influence both the mechanical interaction at the interface and the dispersion of these relatively small reinforcements. We performed a broad study of Portland cement mortar mixtures containing silica fume, plain or silica-functionalized carbon nanotubes, and carbon fibers to characterize changes in fracture properties. The early age hydration kinetics of cement pastes containing carbon nanotubes were compared using isothermal calorimetry. Early age fracture surfaces of cement pastes containing carbon fibers were observed using a scanning electron microscope. The notched beam test method of the Two Parameter Fracture Model was used to determine the fracture properties of each mix. We observed that silica fume and silica functional groups improved the fracture performance of mixtures containing carbon nanotubes and carbon fibers. Further optimization of dosage, size, and interface strength is required to fully utilize carbon nanotubes in cementitious composites.

Effects of silica addition on the particle characteristics and phase transition of flame-synthesized γ-Al2O3 nanoparticles

The effects of silica addition on the thermal stability of flame-synthesized γ-Al2O3 nanoparticles are investigated in this study. Based on the electron microscope images of pure alumina, nanoparticles with diameters ranging from 20 nm to 30 nm were synthesized. No significant changes were observed after heat treatment at 900°C, 1100°C, and 1180°C. After heat treatment at 1260°C, sintered particles larger than 100 nm were observed. All images of the nanoparticles doped with silica, including those taken after heat treatment at 1260°C, showed similar particle sizes regardless of treatment temperature. Based on the X-ray diffraction patterns and specific surface areas, the onset temperature of the phase transition to α-Al2O3 for the flame-synthesized pure alumina was near 1180°C. The addition of silica greatly increased the thermal stability of the synthesized γ-Al2O3 nanoparticles.

The effect of silica addition on the microstructure and properties of polyethylene separators prepared by thermally induced phase separation

ABSTRACTNovel composite polyethylene (PE) separators were prepared via thermally induced phase separation using SiO2 as the inorganic dopant and dioctyl phthalate as solvent. Through the control of silica content, the microstructure, thermal and crystalline properties, electrolyte uptake, thermal stability, and mechanical properties of the as‐prepared separators were investigated. The results showed that the doped silica particles favored the formation of the large pore size. The crystalline degree of PE was enhanced when doping silica in the ternary system below 3 wt %. The liquid electrolyte uptake was increased from 30.2% to 63.2% with doping silica content at 5 wt % in the mixed system, which benefits from the large pore size structure and the hydrophilicity of silica. The thermal decomposition temperature of the composite PE separators is 40°C higher than the pure PE separator due to the steric stabilization and the more stable space structure induced by the doped silica. The tensile strength was increased from 12 MPa to 13.3 MPa when doping 1 wt % silica, but decreased with further silica addition. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40724.

Sol–gel synthesis of nanostructured titania–silica mesoporous membranes with photo-degradation and physical separation capacities for water purification

Abstract The effect of silica addition on the photocatalytic and separation properties of mesoporous titania–silica membranes was investigated. Macroporous α-alumina support was used as substrate, and intermediate layer was obtained by deposition and calcination of the colloidal titania sol on the substrate. Then, titania and titania-5% silica polymeric sols were prepared for deposition on the interlayer as membrane top layer. The samples were characterized by DLS, TG-DTA, XRD, FTIR, BET, FESEM, TEM and AFM. The photocatalytic capability of the membranes was evaluated using methyl orange photo-degradation. The mesoporous composite membrane was prepared with the average pore size of 3.94 nm. The dye removal efficiency of the titania–silica membrane has been determined to be 63% after 60 min UV-irradiation. By coupling separation process with photocatalytic technique, the removal efficiency was improved up to 94%. The synthesized titania–silica membrane showed a great potential due to its multifunctional capability for water treatment.

Influence of silica addition on the properties of epoxidised natural rubber/polyvinyl chloride composite membrane

AbstractFlexible and porous epoxidised natural rubber (ENR)/polyvinyl chloride (PVC) membranes were prepared via phase inversion technique. The pore formation on ENR/PVC membranes was initiated with the introduction of inorganic particles (silica). Two types of silica, microsilica (microcrystalline silica powder) and nanosilica [generated from Tetraethoxysilane (TEOS)] were used. Effects of silica addition on the membrane structure are investigated by means of FTIR, SEM, TGA, and UTM. FTIR results showed the presence of signature peak of SiOSi at 1102 and 1088 cm−1 for ENR/PVC/SiO2 and ENR/PVC/TEOS membrane, respectively. Morphological studies showed that pores developed in ENR/PVC/TEOS membranes were more homogenous as compared to ENR/PVC/SiO2 membranes. Thermal and mechanical stability of the membranes improved with the incorporation of silica. ENR/PVC/SiO2 membrane exhibited better mechanical and thermal properties as compared to ENR/PVC/TEOS membranes. CO2 and N2 gas permeation of silica‐filled membranes increased with increasing silica content and the permeability of ENR/PVC/SiO2 membrane toward N2 and CO2 gasses was higher than ENR/PVC/TEOS membrane. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Effects of silica addition on the chemical, mechanical and biological properties of a new α-Tricalcium Phosphate/Tricalcium Silicate Cement

The addition of tricalcium silicate (C3S) to apatite cements results in an increase of bioactivity and improvement in the mechanical properties. However, adding large amounts raises the local pH at early stages, which retards the precipitation of hydroxyapatite and produces a loss of mechanical strength. The introduction of Pozzolanic materials in cement pastes could be an effective way to reduces basicity and enhance their mechanical resistance; thus, the effect of adding silica on the chemical, mechanical and biological properties of α-tricalcium phosphate/C3S cement was studied. Adding silica produces a reduction in the early pH and a decrease in setting times; nevertheless, the presence of more calcium silicate hydrate (C-S-H) delays the growth of hydroxyapatite crystals and consequently, reduces early compressive strength. The new formulations show a good bioactivity, but higher cytotoxicity than traditional cements and additions higher than 2.5% of SiO2 cause a lack of mechanical strength and an elevated degradability.

Enzyme immobilisation in permselective microcapsules

The objective of this investigation was to study the permselective behaviour of calcium alginate membranes, including the modifying effects of silica additives, which were subsequently used as microcapsule shells. Diffusion experiments and HPLC were carried out to ascertain the size-exclusion property of the membranes for a mixed molecular-weight dextran solution. Hollow microcapsules containing the enzyme dextranase were prepared using double concentric nozzles and the encapsulation performance was evaluated based on an analysis of the enzyme reactivity and stability. To improve mass transport within the microcapsules, magnetic nanoparticles were introduced into the liquid core and agitated using an alternating external magnetic field. The modified membranes exhibited better size-exclusion behaviour than the unmodified membranes. The magnetic nanoparticles slightly improved mass transport inside the microcapsule. The encapsulated enzyme yielded nearly 80% of the free enzyme activity and retained about 80% of the initial catalytic activity even after being used for eight reaction cycles.

Effect of silica addition on thermal stability of heat treated flame synthesised TiO2 nanoparticles

The effect of silica addition on the thermal stability of flame synthesised TiO2 nanoparticles was investigated. TiO2 nanoparticles with varying silica content were prepared using hydrogen diffusion flames. Characterisation and measurement of photocatalytic ability of formed nanoparticles before and after the heat treatment were carried out. On the basis of transmission electron microscope images and particle diameters that were calculated from specific surface area data and X-ray diffraction patterns, it is believed that the addition of silica might interrupt the growth of smaller particles to larger ones in the flame, but could enhance the thermal stability of the formed nanoparticles. Meanwhile, based on the decomposition of methylene blue, the anatase fractions and the calculated particle diameters, the TiO2 nanoparticles that were synthesised with the addition of silica corresponding to 0·03 L min−1 of the silica precursor carrier gas were the most thermally stable among those tested with heat treatment at 1000°C.