Tetraethylortosilicate Research Articles

Modification of Montmorillonite with Cetyl Trimethylammonium Bromide and Tetra Ethyl Ortho Silicate

Modification of montmorillonite (MMt) with cetyltrimethylammonium bromide (CTAB) and tetraethyl ortosilicate (TEOS) has been done. The aim of the research is to study the effect of TEOS and CTAB into MMt. This research is a preliminary step to invent material that can be modified with other functional materials. The study was conducted by recting TEOS with MMt and varying CTAB concentration on MMt previously modified with TEOS. The TEOS concentration was 4.72 M while CTAB concentration was 0.25; 0.5; 2; 3.5; and 5 mmol/g in MMt which has been reacted with TEOS. Material characterization was done by X-Ray Diffraction (XRD), Fourrier Transform Infra-Red Spectrophotometer (FTIR) and Scanning Electron Microscope (SEM). Cation exchange capacity (CEC) of materials was analyzed by titration method. The results show that TEOS and CTAB successfully modified. TEOS adsorbed onto MMt. It was identified from increased basal spacing, specific group and also by its elemental composition, originally having basal spacing 16 Å. After modification with CTAB, basal spacing increased to 28.45 Å or 77.64%. This indicates that CTAB is intercalated within the MMt layers. The CEC of new material is 0.93 meq/g, increase from 0.83 meq/g.

IMPLEMENTATION OF SEQUENTIAL DESORPSION IN DETERMINING Cd (II) ION INTERACTION WITH ADSORBENT OF IONIC IMPRINTING AMINO-SILICA HYBRID

Interactions of Cd (II) ion in solution with the adsorbent of amino-silica hybrid or non-imprinted polymer (NIP) and Cd (II) ionic imprinting (Cd (II)-IIP) have been studied through a sequential desorption process. The adsorbent of NIP and Cd (II)-IIP were synthesized from 3-aminopropyltrimethoxysilane (3-APTMS) and tetraethylortosilicate (TEOS). The value of the Specific surface area, total porous volume, and Cd (II)-IIP porous diameter is each 29.010 m2 g-1, 0.100 mL g-1, and 30.452 A. The interaction contribution of Cd (II) ion was determined by the sequential desorption with water eluent, KNO3 1 M, HONH2HCl 0.3 M in 25 % (v/v) CH3COOH, and Na2EDTA 0.1 M. The sequential desorption result showed that a tendency of Cd (II) ion interaction contribution on NIP and Cd (II)-IIP increased with order of ion exchange interaction < entrapment < complex formation < hydrogen bond.

The viability of MCM-41 as separator in secondary alkaline cells

The viability of MCM-41 membrane as a separator material in secondary alkaline cell is investigated. The inorganic membrane was employed in an alkaline nickel-zinc system. MCM-41 mesoporous material consists of arrays of hexagonal nano-pore channels. The membrane was synthesized using sol-gel route from parent solution comprising of quarternary ammonium surfactant, cethyltrimethylammonium bromide C16H33(CH3)3NBr (CTAB), hydrochloric acid (HCl), deionized water (H2O), ethanol (C2H5OH), and tetraethylortosilicate (TEOS). Both the anodic zinc/zinc oxide and cathodic nickel hydroxide electrodeposited film were coated with MCM-41 membrane. The Ni/MCM-41/Zn alkaline cell was then subjected to 100-cycle durability test and the structural stability of MCM-41 separator throughout the progression of the charge-discharge cycles is studied. X-ray diffraction (XRD) analysis on the dismantled cell shows that MCM-41 began to transform to lamellar MCM-50 on the 5th cycle and transformed almost completely on the 25th cycle. The phase transformation of MCM-41 hexagonal structure into gel-like MCM-50 prevents the mesoporous cell separator from diminished in the caustic alkaline surround. This work has hence demonstrated MCM-41 membrane is viable to be employed in secondary alkaline cells.

Fabrication and characterization of layered double hydroxide/silane nanocomposite coatings for protection of mild steel

Abstract In this paper, environmentally friendly layered double hydroxide nanoparticles/silane hybrid nanocomposite coatings were fabricated on mild steel substrate. Zinc–aluminum layered double hydroxides (Zn–Al LDHs) pillared with different anions (nitrate, molybedate and phosphate) were synthesized and characterized by X-ray diffraction (XRD). Various LDHs was employed in a hybrid silane coating based on mixture of tetraethyl ortosilicate (TEOS) and aminopropyl triethoxy silane (APTES). The silane coatings including LDHs were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and contact angle measurement. Then, the corrosion characterization of the coatings was investigated by electrochemical impedance spectroscopy (EIS), polarization and electrochemical noise (EN) techniques. Addition of LDHs to the sol–gel film increased its barrier properties due to their planar structure. The results revealed that the silane coating in the presence of phosphate could provide superior electrochemical corrosion protection compared to the sol–gel film which is solely incorporated with molybedate and nitrate.

Anoda Pb dan Gel Elektrolit Untuk Propulsi Kapal Selam

Battery is the most important component in the sub marine energy system. Up to now, majority of the sub marine are still using lead acid battery as the power source or propulsion, due to more safe in application as very high capacity of single cell (i.e. 10.000 – 15.000 Ah). The drawbacks of aqueous based battery, which utilize liquid electrolyte, are because of having produced the hydrogen gas during charging process, in which it caused the electrolyte solution to become dry and reduced the performance of battery. In addition that the hydrogen gas generated in the sub marine was dangerous. Therefore, the aim of this research is how to reduce or eliminate of those drawbacks by modifying kind of the liquid electrolyte by using gel electrolyte. The gel electrolyte was synthesized to reduce the evaporation of electrolyte and to avoid the leaking when submarine maneuver. The gel electrolyte was made by using inorganic nanoporous MCM-41. It was synthesized by hydrothermal method, using Tetraethylortosilicate (TEOS) as silica sources, Cethyltrimethylammonium bromide (CTAB) as organic template and H 2 SO 4 as catalyst. The MCM-41 lead acid battery gave a result of OCV ca. 2,1 V.

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The results of structural, microchemical and physicoceramic characterization of ceramic samples (red clay) immersed in solutions TiO2 - ZrO2- SiO2 is presented. Samples were prepared by the sol-gel method using tetraethyl ortosilicate, titanium tetrabutoxide and zirconium tetrabutoxide. Ceramics samples for immersion were prepared with atomized powders of red clay and subjected to firing at 1000 °C. The samples were made from ceramic powders atomized red clay, fired at 1000 °C. After firing ceramics were immersed in the solutions in volume concentrations 10/20/70: Si /Ti /Zr and 10/70/20: Si/Ti /Zr. Immersion times were 2, 4 and 6 minutes respectively. Subsequent to drying the samples were subjected to firing at 600 °C for 1 hour, at a rate of 2 °C/min. Microchemical and microstructural aspects of the fired samples were established using X-ray diffraction (XRD), infrared spectroscopy (FTIR) and x-ray dispersive energy (EDX). Technological properties evaluated were water absorption, bulk density and mechanical resistance to flexion. The study results allowed to determine that mechanical resistance to flexion improvement in samples immersed in the solution 10/70/20: Si/Ti/Zr. Similarly, a slight reduction in the percentage of water absorption with this same treatment was observed. Treatment with greater amount of zirconium, shows no significant changes in relation to the standard used.

Viability of MCM-41 Inorganic Membrane Separator in Secondary Nickel-Zinc Cell

The viability of MCM-41 inorganic membrane as a separator material in secondary nickel-zinc cell is investigated. MCM-41 mesoporous material consists of arrays of hexagonal nano-channels. The membrane is synthesized by dip-coating procedures from parent solution comprising of quarternary ammonium surfactant, cethyltrimethylammonium bromide C16H33(CH3)3NBr (CTAB), hydrochloric acid (HCl), deionized water (H2O), ethanol (C2H5OH), and tetraethylortosilicate (TEOS). Both the anodic zinc foil and cathodic nickel hydroxide electrodeposited film are coated with MCM-41 membrane. The Ni/MCM-41/Zn alkaline cell is then subjected to 100-cycle durability test. The charge-discharge plot showed typical secondary zinc anode profile – rapid capacity fading. X-ray diffraction analysis on the dismantled cell indicated the transformation of MCM-41 hexagonal matrix structure into MCM-50 lamellar gel form which prevent the mesoporous cell separator from diminished in the caustic alkaline surround.

Preparation of TiO2-SiO2 using Rice Husk Ash as Silica Source and The Kinetics Study as Photocatalyst in Methyl Violet Decolorization

Preparation, characterization and utilization of TiO2-SiO2 as photocatalyst for methyl violet (MV) decolorization has been conducted. In this research, preparation of TiO2-SiO2 was developed based on natural renewable silica source; rice husk ash (RHA) via a sol-gel technique. The composite was formed by the dispersing of titanium isopropoxide as titania precursor into the gel of silica followed by aging, drying and calcination. The TiO2-SiO2 sample was characterized by powder X-ray diffraction (XRD), diffuse reflectance-UV Visible spectrophotometric analysis (DRUV-Vis), gas sorption analyzer and Scanning electron micrograph (SEM) before its utilization as photocatalyst in methyl violet photooxidation. As comparison to the physicochemical character study, the synthesis of TiO2-SiO2 by using tetraethyl ortosilicate (TEOS) was performed as a confirmation. Result showed that prepared TiO2-SiO2 has the character similar to TiO2-SiO2 as synthesized by TEOS precursor. The formation of crystalline titania in anatase and rutile phase was identified with increasing surface porosity data and the value of band gap energy which sufficiently contribute to a photocatalytic mechanism. The character data are in line with the kinetic data of methyl violet decolorization. From the compared photooxidation, photolysis, photocatalysis and adsorption process, it can be concluded that TiO2-SiO2 acts efficiently as a photocatalyst. © 2015 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0)

Critical Assessment of the Surface Tension determined by the Maximum Pressure Bubble Method

The main factors that influence the value of surface tension of a liquid measured with the Maximum Pressure Bubble Method are critically evaluated. We present experimental results showing the effect of capillary diameter, capillary depth, bubble spheroidicity and liquid density at room temperature. We show that the decrease of bubble spheroidicity due to increase of capillary immersion depth is not sufficient to explain the deviations found in the measured surface tension values. Thus, we propose a simple experimental procedure that allows determining the surface tension of a liquid without any previous knowledge of its density. This procedure is especially useful when the liquid of interest exhibits variations of surface tension and density with time, as for example during condensation reactions to obtain SiO2 sols from a tetraethyl ortosilicate (TEOS) solutions during their aging process.

Preparation and characterization of organo-functionalized silicas for bilirubin removal

Hybrid-silica materials containing octyl, phenyl and urea-propyl functional groups were reported. These functionalized silicas were prepared by a via one-pot synthesis method through co-condensation of tetraethyl ortosilicate with organosilanes co-precursors. The obtained materials were analyzed by a number of techniques including scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction pattern and nitrogen sorption measurement. The main elements: morphology and surface properties of the final products that are basically dependent on the type and the quantity of functional-containing groups were fully discussed. The adsorption properties of the modified silicas were investigated against bilirubin in aqueous solution at pH 7.4, the effect of time was studied as well. The modified silicas showed a greatly increasing of adsorption capacity for bilirubin compared to pure amorphous silica. The results indicate that the type of functional-containing groups and surface properties affect the adsorption behavior. These materials show a potential application as effective adsorbents for bilirubin removal.

Wash fastness improvement of malachite green-dyed cotton fabrics coated with nanosol composites of silica-titania

Washing fastness of dyed cotton fabrics by malachite green (MG) blended with nanosols composite of SiO2-TiO2 has been significantly enhanced. The nanoparticulate inorganic sols were prepared by acid-catalyzed hydrolysis of titanium (IV) tetraisopropoxide (TTIP) and tetraethylortosilicate (TEOS) in ethanol at room temperature. The effect of silica on the characteristics of nanosols composite of TiO2-SiO2 was studied. Nanosols morphology was examined by transmission electron microscope (TEM). The nanosols silica-titania composite showed homogeneous morphology of interconnected spheres of about 20–25 nm. Enhanced dye absorption was observed at nanosols with silica content. The reflection spectra of the samples before and after leaching test using sodium dodecyl sulphate were recorded. The results showed that embedding TiO2-SiO2 and SiO2 sols into the MG dye can improve the wash fastness by 40–95%. The highest improvement was obtained by SiO2-MG-coated cotton fabrics as well as composites of SiO2-TiO2-MG-dyed cotton fabrics at highest silica content. The MG-nanosols composite silica-titania dyed cotton fabric has also shown remarkable antibacterial activity over Staphylococcus aureus and Escherichia coli.

Production of 5-hydroxymethylfurfural from glucose using aluminium doped MCM-41 silica as acid catalyst

Mesoporous aluminium doped MCM-41 silica catalysts were prepared by a sol–gel method in two reaction steps (acid and alkaline hydrolysis) from joint hydrolysis of tetraethylortosilicate (TEOS) and aluminium triisoproxide, using n-dodecylammonium chloride as surfactant, at room temperature, and subsequent calcination at 550°C. Two solids with different Si/Al molar ratios (5 and 10) were synthesized, which possess high specific surface area and acidity, with both Brönsted and Lewis acid sites. By using a biphasic water/MIBK as reaction medium and a 30wt.% of the 10Al-MCM catalyst with respect to the substrate weight (glucose), 87% of glucose conversion and 36% of HMF yield were achieved at 195°C after 150min of reaction time. The reaction is quite selective toward HMF, since only fructose was detected as by-product, but neither levulinic acid nor furfural were found. Moreover, the use of a sodium chloride aqueous solution (20wt.%) and MIBK ameliorates the partition coefficient between the organic and the aqueous phases up to 1.9, leading to an enhancement of the glucose conversion and HMF yield, attaining values of 98% and 63%, respectively, in a time as short as 30min. The catalytic performance of this acid solid, associated to the presence of strong acid sites, is well maintained after three catalytic cycles.

Study on the Fabrication of Superhydrophobic Microporous Polypropylene Flat Membrane Using &lt;i&gt;In Situ&lt;/i&gt; Synthesis of Modified Fluorinated Silica Nano Particles

The wettability is the most important features of membrane, when it works as contactors. Although the membrane contactors offer many advantages over conventional contacting equipments, additional mass transfer resistance is introduced when micropores are filled with aqueous absorbents. Therefore, fabrication of superhydrophobic membrane which prevents diffusion of aqueous absorbent into membrane pores is a highly challenging task. In this work, superhydrophobic polypropylene (PP) membrane was fabricated using in situ synthesis of silica nano particles via thermally induced phase separation (TIPS) method. Flat sheet fabricated PP membranes were casted with methanolic solution containing various ratios of perfluorooctyltriethoxysilane (PFOTES)/ tetraethylortosilicate (TEOS) and then sol-gel reaction between the mixed silances was completed. The contact angle of coated membrane was reached to 168 degree, when the percentage of PFOTES/TEOS was fixed at 50% (mol/mol). Interestingly, due to the microporous structure of PP membrane, the synthesized fluorinated silica nanoparticles were observed on the surface as well as in the cross-sectional area of the membrane. Field emission scanning electron microscopy (FE-SEM) images were confirmed this point. Chemical structure of the coated membranes with 50% PFOTES was compared with pure PP membrane using ATR-IR. In order to evaluate the operational performance, coated membranes were immersed in aqueous solutions of mono ethanol amine (MEA), di ethanol amine (DEA) and pure water. In comparison with pure PP membrane, obtained results showed that the wettability of coated membranes was considerably decreased.

Effect of hydrothermal treatment on Cr-SiO2 mesoporous materials

Cr/SiO2 (MCM-41) materials were prepared by the sol–gel method by hydrolysis of tetraethylortosilicate (TEOS) using cetyltrimethylammonium bromide (CTAB) as a template. The effect of hydrothermal treatment between 120–220°C on the structural properties was studied. Well ordered Cr/MCM-41 with a very narrow pore size distribution was obtained after hydrothermal treatment from RT to 150°C.Materials synthesized at higher temperatures (200 or 220°C) showed the collapse of the ordered mesoestructure to give mesoporous Cr/SiO2 with an open surface. Superficial Cr3+/Cr6+ ratio was determined by XPS over materials hydrothermically synthesized at different temperatures, and calcined in air at 300°C. The hydrothermal treatment improved the chromium to silica interaction, promoting a higher resistance to form Chromium (VI) sites. The chromium (III) ions incorporated to the silica structure developed acid sites responsible for the 2-PrOH dehydration.

Acid sites development on Cr3+/SiO2 catalysts obtained by the sol–gel method and hydrothermal treatment: Effect of calcination temperature

Cr/SiO2 catalysts (4–8% Cr, w/w), obtained from Cr(III) salts and tetraethylortosilicate (TEOS), were prepared by the sol–gel method. After TEOS hydrolysis in ammoniacal solution (pH: 9.5), the gel was treated under hydrothermal conditions at 120–220°C. The solids were characterized by N2 sorptometry, TG–DTA, DRUV–vis, XRD, and FTIR. In vacuum or N2 atmosphere, Cr3+ ions were stable up to 450°C. However, calcination in air promotes the partial oxidation of Cr3+ to Cr6+ as the temperature increases from 200 to 450°C. The amount of Cr6+ formed depends on the temperature of the hydrothermal treatment. 2,6-Lutidine adsorption allows to determine the evolution, with respect to calcination temperature, of both Lewis and Brönsted acid centers. Cr3+ ions were related to the presence of Lewis sites, and Cr6+ ions to the development of weak Brönsted acid sites. Accordingly, the 2-propanol dehydration reaction rate shows an increase when the catalysts are treated in N2 at 450°C, while catalysts calcined in air develop a lower acidity. The dehydration reaction is attributed to the presence of Lewis acid centers.

Preparation of sol–gel based nano-structured hybrid coatings: effects of combined precursor’s mixtures on coatings morphological and mechanical properties

Nanostructured hybrid clearcoats were produced using sol–gel based organic/inorganic precursors. To this end, clearcoats containing mixtures of a network former (tetraethyl ortosilicate; TEOS) and a network modifier (methacryloxy propyltrimethoxysilane; MEMO) and their hydrolyzed forms were prepared. Scanning electron microscope and atomic force microscope were utilized in order to investigate the morphology of different sol–gel prepared films. The mechanical properties of the bulk and surface of the clearcoats were studied by dynamic mechanical thermal analysis and nanoindentation techniques. The scratch resistance of the hybrid clearcoats was also studied by a laboratory carwash simulator. Decrease in glass transition temperature (Tg), cross-linking density, hardness and elastic modulus were seen for the clearcoat composed of hydrolyzed network modifier combined with hydrolyzed and non-hydrolyzed network former. However, a reverse effect was seen when the hydrolyzed TEOS and non-hydrolyzed MEMO was used. No improvement was observed using hydrolyzed MEMO in the clearcoat composition. Generally, results revealed improved mechanical properties of the clearcoat when the hydrolyzed network former was used together with non-hydrolyzed MEMO. Greater phase separation and silica cluster formation were seen for the clearcoats loaded with hydrolyzed MEMO compared with hydrolyzed TEOS.

OTES modified transparent dip coated silica coatings

The present paper describes the room temperature synthesis of dip coated water repellent silica coatings on glass substrates using octyltriethoxysilane (OTES) as a co-precursor with two-step sol–gel process. Silica sol was prepared by keeping the molar ratio of tetraethylortosilicate (TEOS) precursor, methanol (MeOH) solvent, acidic water (0.001M oxalic acid) and basic water (12M NH4OH) constant at 1:11.03:0.17:0.58 respectively, throughout the experiments and the OTES weight percentage was varied from 0% to 15%. It was found that with an increase in wt% of OTES, the roughness and hydrophobicity of the films increased, however the optical transmission decreased from 93% to 88% in the visible range. The hydrophobic silica films retained their hydrophobicity up to a temperature of 259°C and above this temperature, the films became hydrophilic. The hydrophobic silica thin films were characterized by taking into consideration the surface roughness studies, Fourier transform infrared (FT-IR) spectroscopy, percentage of optical transmission, scanning electron microscopy (SEM), Thermogravimetric-differential thermal analysis (TG-DTA) and contact angle measurements.

SYNTHESIS OF Na-Y NANOZEOLITE ON GLASSY CARBON BY SEEDING METHOD

Nanozeolite synthesis was carried out through seeding method, in which the seed was Y zeolite (member of faujasite, FAU, family) using tetraethyl orto silicate (TEOS) as silica source, and aluminium isopropoxide Al[(CH3)2CHO)]3 as aluminum source, and tetramethylammoniumhydroxide (TMAOH) as template, under hydrothermal condition. The seeds then were grown on glassy carbon (GC) sheet, that prior being used was modified, using layer by layer (LbL) technique, with three layers of polyelectrolytes: Poly(diallyldimethylammoniumchloride), PDDA; Poly-4 sodiumstyrenesulfonate, PSS; and PDDA again. The seeded GC sheet then was immersed into colloidal suspension with molar composition as follow: 14Na2O: Al2O3: 10SiO2: 798H2O: 3Na2SO4 and the pH of the suspension was kept at 9,0 before was treated hydrothermally for 20 hours at 100 oC. The variation on number of seed layers on GC (1, 2 and 3 layers), observed by SEM, showed that homogenous structure and crystal size was obtained with 1 layer of seeds applied on the surface of glassy carbon. When more layers of seeds applied, the agregation and intergrowth of zeolite crystals in the thin film of zeolite became more visible. XRD pattern of the as-prepared thin film zeolite indicates that the zeolite has nanoparticle structure. Furthermore, the pattern of glassy carbon predominated the XRD pattern and covered the pattern of Y-zeolite. On the other hand, XRD of as prepared bulk Y-zeolite shows structure of FAU framework. Keywords: glassy carbon, FAU, nanozeolite, seeding method

Synthesis and Characterization of New Silica‐Titania Mixed Oxides Obtained by Sol‐Gel Technique

AbstractSummary: Although titanium dioxide has a high surface area, it is not thermally stable and its surface area decreases strongly at high temperature due to phase transformation and crystal growth. To improve the thermal stability of titanium dioxide, the synthesis of mixed oxides can be an elegant approach. In this study different experimental variables for the synthesis and characterization of new titania‐silica mixed oxides intended to be used as fillers have been proposed. To manufacture the mixed oxides, different tetraethylortosilicate (TEOS)/Tetrabutyl orthotitanate (TBTi) mixtures in different ratio, ethanol as solvent, and acetic acid as catalyst were used via sol‐gel synthesis route. These oxides were characterized by transmission electron microscopy coupled with EDX analysis (TEM‐EDX), optical microscopy, X‐ray diffraction, textural properties, and pH measurements and wettability with liquids of different polarity.

Characterisation of nickel–zinc ferrite/silica nanocomposites with low ferrite concentration obtained by an improved modified sol–gel method

The paper presents a study regarding the structure, morphology and magnetic behaviour of x% (Ni0.65Zn0.35Fe2O4)/(100 − x)% SiO2 ferrimagnetic nanocomposites for low Ni–Zn ferrite concentration (x = 5, 10, 15, 20 and 30 mass percent) obtained by an improved modified sol–gel method. The obtained gels and nanocomposites have been characterized by fast Fourier transform-infrared (FT-IR) spectrometry, X-ray diffraction (XRD), transmission electron microscopy (TEM) and magnetic measurements (MM). The addition of a supplementary quantity of diol in the synthesis, corresponding to a molar ratio EG : TEOS = 1:1, and the control of the thermal treatment applied to the precursor xerogels tetraethylortosilicate (TEOS)–metal nitrates (MN)–ethylene glycol (EG) leads to fine (~2–9 nm), almost spherical Ni–Zn ferrite nanoparticles homogenously dispersed inside the amorphous SiO2 matrix. TEM images reveal the fine nature and the narrow size distribution of the ferrite nanoparticles. Nanoparticles diameter increases with the ferrite concentration and with the annealing temperature. For all concentrations of ferrite in SiO2 and all annealing temperature, we have obtained Ni0.65Zn0.35Fe2O4 ferrite as single phase (proven by XRD) in the amorphous silica matrix, only after a pre-treatment of synthesized gels, at 573 K, for 3 h. The magnetic behaviour of ferrite nanoparticles in quasi-static magnetic fields is very particular, depending on the annealing temperature and the ferrite content in silica matrix. We have obtained superparamagnetic behaviour for the nanocomposites, for a concentration of 30% ferrite in SiO2 at high annealing temperature, of 1,273 K.