Tetraethoxysilane Content Research Articles

Silanization of ZnO nanofibers by tetraethoxysilane

ABSTRACTZinc oxide (ZnO) nanofibers are synthesized by electrospinning technique and then silanized to tailor its structural, optical, and electrical properties. The modification of ZnO nanofibers by chemical treatment of tetraethoxysilane (TEOS) is clearly evident from the appearance of relevant Fourier transform infrared peak at about 1000 cm−1 corresponding to ZnOSi bond. The height of this peak increases linearly with increase in concentration of silane up to 400 μL, and afterward become plateau up to 500 μL. Diffuse reflectance spectroscopy measurement shows that band gap decreases from 3.35 eV for pure zinc oxide nanofibers to 3.11 eV with successive increase in concentration of TEOS from 100 to 500 μL. The electrical characteristics of modified ZnO nanofibers are analyzed by impedance spectroscopy. It is observed that impedance of ZnO nanofibers increases (resistance from 1.69 × 108 to 2.618 × 109 ohm and capacitance from 2.043 × 10−12 to 7.618 × 10−13 F) with increase of TEOS concentration. This study provides guidelines for tailoring the electrical properties of ZnO nanofibers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45378.

Effects of silanization and silica enrichment of carbon fibers on interfacial properties of methylphenylsilicone resin composites

Effects of silane and silica enrichment of carbon fibers (CFs) on interfacial properties of methylphenylsilicone resin (MPSR) composites were investigated. CFs were oxidized, grafted with 3-aminopropyltriethoxysilane (APS) and then modified with silica nanoparticles prepared by the sol-gel polymerization of tetraethoxysilane (TEOS). Chemical structures of CFs were characterized by confirming the successful grafting. Scanning electron microscopy (SEM) showed a uniform distribution of silica nanoparticles on the CFs surface. The interlaminar shear strength (ILSS) and impact toughness of silanized CF (CF-Siloxane) composites were 12.05% and 7.46% higher than those of untreated composites. However, ILSS and impact toughness of the hybrid fiber (CF/Si) composites obtained from the hydrolysis of different concentrations TEOS improved significantly, especially for grafting silica enrichment with the TEOS concentration of 0.05mol/L (CF/Si0.05), increasing 45.64% in ILSS and 29.59% in impact properties. Moreover, the hydrothermal aging resistance was also improved greatly. Meanwhile, functionalization processes did not decrease fiber tensile strength.

Growth process and morphology control of SBA-15 particles: synergistic effects of tetraethoxysilane and Pluronic-123 concentrations

The synergistic effects of the template [Pluronic-123 (P123)] and the silica source [tetraethoxysilane (TEOS)] concentrations on the SBA-15 mesoporous silica morphology were investigated through adjusting the system initial solution volume with the same amounts of silica source and template. It found interestingly that the SBA-15 morphology changed from the hexagonal plate-like shape to the gear-like shape with the decrease of the P123 and TEOS concentration. Based on the morphology variations, the growth of the gear-like morphology was speculated to be formed through the preferential growth at the corner and the layer-by-layer growth in the end face of the ordinary hexagonal plate-like particle.

Enhanced high temperature oxidization resistance of silica coated γ-Ce2S3 red pigments

Silica layer coated γ-Ce2S3 red pigments were successfully prepared based on a Stober method followed by a hydrogen-argon atmosphere heat treatment at 700°C. The effect of water/ethanol volume ratio and tetraethoxysilane concentration on the microstructure of the coating layer and its high temperature oxidizing protection to pigments was investigated. A transparent silica coating layer with dense microstructure and about 60nm thickness can provide a favorable protection for the red hue of the γ-Ce2S3 pigments. The oxidization resistant temperature was enhanced to 550°C for the dense silica layer coated γ-Ce2S3 pigments as compared to ≤350°C for the uncoated ones. A red color (L*=29.59, a*=27.53 and b*=27.66) was still remained for such silica coated γ-Ce2S3 pigments after heated treated at 550°C in air, indicating its potential for high temperature industrial applications.

Study on QPVA/TEOS hybrid anion membrane functionalized with quaternary ammonium groups for adsorption of Rhodamine B from aqueous solutions

Quaternized poly(vinyl alcohol)/tetraethoxysilane hybrid membranes were prepared and their adsorbability for Rhodamine B from aqueous solution was investigated. Experimental parameters, which will affect Rhodamine B sorption, such as tetraethoxysilane contents, pH, contact time, initial concentration and temperature were studied. The research results revealed that adsorption effect of Rhodamine B was enhanced by the formation of organic–inorganic hybrid structure and the grafting of quaternary ammonium groups. The fitting result of kinetic data was revealed that the pseudo-second-order model best described the adsorption of Rhodamine B. The equilibrium data were fitted by three isotherm models, and the Temkin model gave the best fit result based on the adsorption equilibrium data. Also, the adsorption free energy showed that the mechanism of Rhodamine B adsorption onto the membrane was chemisorption. Thermodynamic parameters calculation results revealed that the adsorption process of Rhodamine B onto the hybrid membrane was endothermic and spontaneous. Moreover, the hybrid membrane was successfully utilized for successive five cycles for the adsorption–desorption of Rhodamine B.

Tunable morphology for silica/poly(acrylic acid) hybrid nanoparticles via facile one-pot synthesis

Synthesis of the hybrid nanoparticles through simultaneous polymerization of organic monomer and solgel process of the inorganic precursor is a promising subject for creating new materials. Herein, an efficient one-pot synthesis method using the simultaneous sol-gel process with free radical polymerization technique reports the tunable morphology for silica/ poly(acrylic acid) (PAA) hybrid nanoparticles in which tetraethoxysilane (TEOS) and acrylic acid were used as inorganic and organic precursors, respectively. To achieve the best conditions for a simultaneous synthesis, the most important parameters such as pH, TEOS concentration, AA/TEOS ratio, surfactant concentration and temperature were adopted with respect to particle size. It is experimentally demonstrated that the reaction temperature is the most influential parameter affecting the particle size of hybrid nanoparticles. In addition, transmission electron microscopy images revealed that, the tunable morphology of hybrid nanoparticles from the organic-inorganic core-shell to organic and inorganic heterodimer nano(semi)spheres can be achieved by controlling the concentration of TEOS.

Synthesis and characterization of crystalline carboxymethylated lignin–TEOS nanocomposites for metal adsorption and antibacterial activity

Biodegradable carboxymethylated lignin–tetra ethoxysilane (TEOS) nanocomposites (CML–T) were synthesized using lignin extracted from rice straw (RS) followed by surface modification through carboxymethylation. Composites were characterized by UV-spectroscopy, Fourier transform infrared (FT-IR), scanning electron microscope (SEM), X-ray diffraction pattern (XRD), atomic absorption spectroscopy (AAS) and particle size distribution (PSD). The average diameter (D50) of the CML–T composite particles was observed in the range of 160–560 nm. XRD spectra and SEM micrographs confirmed the high degree of crystallinity (peaks located at lower angle, 2θ = 12 and 22.0°) and porous nature of nanocomposites with increasing concentrations of TEOS. The composite exhibited nickel (Ni2+) and cadmium (Cd2+) adsorption up to 70.72 and 81.79 %, respectively in AAS analysis. The CML–T composite was investigated to assess their future applications as wound dressings and antimicrobial and packaging agents. Based on the antimicrobial properties and potential to remediate toxic heavy metals, the composites are proposed to be used for wastewater treatments, as packaging materials and for preparation of biofilters for environmental protection.

Palygorskite-based hybrid fluorescent pigment: Preparation, spectroscopic characterization and environmental stability

A new hybrid fluorescent pigment was prepared combining the adsorption of a fluorescent yellow X-10GFF (FY-10G, a coumarin derivative fluorescent dye) on palygorskite (PAL) with the silica encapsulation by the hydrolysis of tetraethoxysilane (TEOS) using acetic acid as catalyst. The photo-stability under UV irradiation and the resistance toward acid, alkali and ethanol of the SiO2@FY-10G/PAL hybrid fluorescent pigments were systematically discussed. The results show that the introduction of PAL not only significantly influences the absorption and fluorescence spectra of the FY-10G, but also enhances the thermal stability of FY-10G due to the supramolecular host/guest interactions. The encapsulation of the silica coating can effectively improve thermal- and photo-stability of FY-10G. Moreover, the fluorescent intensity and the resistance of the hybrid fluorescent pigments to acid and organic solvent enhance with the increase of TEOS concentration.

Synthesis of Janus Mesoporous Silica Nanostructures with Organic–Inorganic Hybrid Components through a Sprout‐Like Growth Method

AbstractIn this paper, we have established a simple and generalizable sprout‐like growth method for the facile synthesis of Janus mesoporous silica nanostructures with organic–inorganic hybrid components by using periodic mesoporous organosilica (PMO) nanoparticles as seeds with mesoporous SiO2 as branches growing on the PMO surface. The morphology of Janus nanostructures with different lengths and numbers of SiO2 branches can be easily controlled by varying the tetraethoxysilane concentration in the synthesis system. The Janus nanostructures are also easily modified with different SO3H and NH2 groups on the SiO2 branches and PMO cores, respectively, and exhibit excellent catalytic performance in the deacetalization–Henry cascade reaction.

Studies on Thermal and Mechanical Properties of Epoxy-Silicon Oxide Hybrid Materials

Ultrasonic dual mixing (UDM) process involving ultrasonic vibration with simultaneous stirring is used to prepare epoxy-silicon oxide hybrid materials with inorganic nanoscale building blocks by incorporating nanoscale silicon oxide network in epoxy matrix. The silicon oxide network is obtained from tetraethoxysilane (TEOS) by using the in situ sol-gel process. Same epoxy-silica hybrid materials were also prepared by mixing with simple impeller stirring, and its properties were compared with the material of same composition prepared by the UDM process. The epoxy-silicon oxide hybrid materials are characterized by using FT-IR, DSC, FESEM, and XRD techniques. The glass transition temperature, tensile strength, and elastic modulus of the epoxy-silicon oxide hybrid materials treated by UDM process are found comparatively better than those of the materials processed by a rotating impeller. FESEM studies confirm that amount of TEOS varies the distribution and size of silicon oxide network, which remains relatively finer at lower content of TEOS. Significant improvement of thermal and mechanical properties of the neat epoxy is noted in the presence of 3.05 wt.% TEOS content in it is giving rise to the formation of inorganic building block of silicon oxide of size 88 ± 45 nm in the matrix. In this regard, the use of UDM process is found superior to mixing by simple impeller stirring for enhancement of properties of epoxy-silicon oxide hybrid materials. Lowering of properties of the epoxy-silicon oxide hybrid materials with TEOS addition beyond 3.05 wt.% up to 6.1 wt.% occurs primarily due to increase of amount and size (up to 170 ± 82 nm) of the inorganic building block in the matrix.

Ferrocenyl-functionalized organic-inorganic hybrid silica: A New kind of anion chemsensor toward flouride anion

A new kind of ferrocenyl based chemosensor toward anions covalently bonded to silica have been successfully prepared by co-condensation of the modified Fc-Urea-Si 5 and tetraethoxysilane (TEOS). The hybrid material was characterized by IR, 1HNMR, SEM, and XRD experiments. And the selective anion sensing property of the hybrid material was studied by Uv–vis and CV. The morphology of the hybrids could be tuned by pH and the content of TEOS. The hybrid networks were able to donate –NH units for selectively sensing fluoride anion with optical and electrochemical changes, accompanied by color and electrochemical changes. Hybrid network formation as well as fluoride sensing mechanism is proposed. Such nanostructure based hybrids would have potential applications in biological systems.

Dendritic silica nanoparticles synthesized by a block copolymer-directed seed-regrowth approach.

A facile seed regrowth method is presented for the preparation of a new type of colloidal dendritic silica nanoparticles (DSNPs) with unique Konpeito-like morphology and high surface area (∼400 m(2) g(-1)). Growth of silica nanoprotrusions on the surfaces of colloidal silica nanoparticles proceeds by hydrolysis and polycondensation of tetraethoxysilane (TEOS) in the presence of a PEO-PPO-PEO-type block copolymer (Pluronic F127) under controlled pH conditions. The polymers adsorbed on the seed surface play a crucial role in the formation of DSNPs. DSNPs with controllable size (28-85 nm) and narrow size distributions can be obtained by using monodisperse silica nanoparticles with various sizes as seeds. The surface morphology of DSNPs is tunable by changing the concentration of TEOS. Additionally, novel dendritic silica nanochains are prepared using one-dimensionally assembled silica nanoparticles as the seeds.

Investigation of the structure, elemental and phase compositions of Fe3O4-SiO2 composite layers by scanning electron microscopy, X-ray spectroscopy, and thermal nitrogen desorption methods

The composite layers formed by drying a Fe3O4-SiO2-based colloidal solution were studied. The colloidal solution was obtained by the precipitation of Fe3O4 in the presence of highly dispersed silicon dioxide synthesized by the sol-gel method from a tetraethoxysilane alcohol solution. The microstructure and composition of the layers were analyzed using scanning electron microscopy, energy-dispersive X-ray microanalysis, thermal nitrogen desorption, and Raman spectroscopy. The emphasis was placed on the study of phase transitions in iron oxides under laser radiation. It was found that the tetraethoxysilane content has a substantial influence on the ratio of iron oxide and silicon dioxide in the layer, the specific surface area of SiO2 powders, the threshold laser radiation power necessary to induce the Fe3O4 α -Fe2O3 phase transformation, and on the position of the maximum of the absorption band corresponding to the A1g vibrations in α-Fe2O3.

Deoxygenation performance of polydimethylsiloxane mixed‐matrix membranes for dissolved oxygen removal from water

ABSTRACTThe removal of dissolved oxygen (DO) from water is an essential and important step in many industrial applications. The membrane technique offers much potential superiority over conventional physical and chemical processes. The development of a high‐performance membrane is the core of the membrane separation technique. In this study, a crosslinked matrix composed of a polydimethylsiloxane (PDMS) membrane with incorporated silica networks by the sol–gel method was manufactured. The application of the membrane method for the removal of DO from water on the laboratory scale was studied. The membrane properties and morphological structure were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, crosslinking density, and mechanical measurements. The PDMS hybrid membranes on the deoxygenation experiment by a vacuum degassing process were investigated. The results show that the crosslinked PDMS hybrid membranes effectively improved the oxygen‐removal efficiency with increasing tetraethoxysilane (TEOS) content, and the best performance was obtained when the weight ratio of PDMS–TEOS concentrations was 10:5. The optimal conditions for the deoxygenation performance were also investigated, and the results indicate that the degassing performances were related to the operating temperature, vacuum level, and feed flow rate. The PDMS nonporous composite membranes showed superior performances and have good potential for applications in industry for the removal of DO from water. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41350.

Hybrid films with (trimethoxysilylpropyl) methacrylate (TMSM), poly (methyl methacrylate) PMMA and tetraethoxysilane (TEOS) applied on tinplate

The tetraethoxysilane (TEOS) influences morphological and electrochemical properties of hybrid films by function of concentration. Moreover, the use of acetic acid as a catalyst in the sol enables a more complete hydrolysis of the silane precursors due to the fact that the acetic acid goes through a more complete ionization when in aqueous solution. The aim of this paper is to study the effect of the concentration of tetraethoxysilane (TEOS) on the protective properties of the film on tinplate substrate. The tinplate was coated with a hybrid film obtained from a sol-gel method constituted of the following alkoxide precursors: 3 - (trimetoxisililpropil) methacrylate (TMSM) and poly(methyl methacrylate) PMMA. The effect of tetraethoxysilane (TEOS) concentration has also been evaluated. The films hydrolysis was performed at a pH value of 3. 0 using acetic acid as a catalyst. The films were obtained by dip-coating process, cured for 3 hours at 160 ºC. The film morphology was evaluated by SEM and profilometry. The electrochemical behavior of the films was evaluated by open circuit potential monitoring, potentiodynamic polarization and electrochemical impedance spectroscopy. The film hydrophobicity was determined by contact angle measurements. The studied films have shown good performance as to corrosion resistance on tinplate. The hybrid film which was obtained through the addition of an excessive amount of TEOS (T3A3) showed increased thickness. Nevertheless, due to an intense densification of the film, promoted by the addition of TEOS, a formation of cracks was registered, thereby compromising the corrosion resistance.

Preparation of Silica-Coated Ultrathin Gold Nanowires with High Morphological Stability

We demonstrated a preparation method of silica-coated straight ultrathin Au nanowires (NWs). Water-dispersive ultrathin Au NWs capped with a long-chain amidoamine derivative (C18AA) were used for silica coating. The Au NWs were partially covered with 3-mercaptopropanoic acid by the ligand exchange method, and silica coating of the Au NWs was carried out by the hydrolysis of tetraethoxysilane (TEOS) at pH > 6.7 because the shape of the Au NWs was changed under acidic conditions. The thickness of the silica layer depended on the concentration of TEOS, and the layer was able to decrease to 6-10 nm thick. We also demonstrated that the silica-coated Au NWs had high morphological stabilities against external stimuli such as a TEM electron beam, heat, and pH compared with the bare Au NWs.

Preparation of SiO2 /epoxy nanocomposite via reverse microemulsion in situ polymerization

Reverse water/oil (w/o) microemulsions composed of epoxy resin (EP) (the oil phase) and nonionic surfactant and ammonia aqueous solutions (the water phase) were used in the synthesis of SiO2/EP nanocomposites. The stability of reverse microemulsion was evaluated by measuring water solubilization of the microemulsion. Effects of surfactant type and content, ammonia concentration and temperature on the water solubilization were systematically investigated. Higher water solubilization capacity was obtained by nonionic surfactant TX-100 compared with other two surfactants, Span-80 and Tween-80. Ammonia concentration of 5 wt% and preparation temperature at 35°C were favorable for forming a stable microemulsion and enabling the subsequent hydrolysis and condensation reaction of inorganic precursor tetraethoxysilane (TEOS). SiO2/ epoxy nanocomposites were prepared via in situ polymerization of TEOS within the nanoscale reverse microemulsion “water pool”. FTIR, SEM, and universal testing machine were used to characterize the structural and mechanical properties of the composite. The results revealed that the optimal mechanical properties were obtained at 3 wt% TEOS content. Compared with neat epoxy resin, the tensile and flexural strength of the composite were 40% and 12% higher, respectively. The formation of the silica structure in the hybrid was investigated with FTIR. The SEM and optical observations showed a ductile fracture morphology and good miscibility between inorganic and organic phases. POLYM. COMPOS., 35:1388–1394, 2014. © 2013 Society of Plastics Engineers

The effect of silica morphology on properties of PVA/silica nano-composites

Two kinds of poly(vinyl alcohol) (PVA)-silica composites were prepared with different methods. One composite was prepared by directly mixing PVA with 80 nm silica nano-particles which were made from tetraethoxysilane (TEOS). The another was obtained by the mixing PVA and hydrolyzed TEOS in the presence of acid-catalyst. The properties of the two PVA/silica hybrids were characterized by means of scanning electron microscopy (SEM), UV-Visible spectroscopy, solubility tests, limiting oxygen index (LOI) test, tensile test and dynamical mechanical analysis (DMA), respectively. The results indicate that PVA-TEOS composites (PT for short) display more transparency than PVA-silica nano-particles hybrids (PS for short). At the same time, The PT composites presented more excellent performance than PS in water resistance, fire resistance and mechanical properties. Moreover, the Tg of PT increased with increasing TEOS content, while that of PS decreased.

Study on the Preparation and Particle Size Control of Silica Sphere in a Sol-Gel Process

Silica sphere has wide applications not only in the field of physical chemistry dealing with dynamic behavior and stability of particulate systems, but also in industries including catalysts, ceramics, pigments, pharmacy, etc. However, the control on the particle size is a key factor in the preparation process of silica sphere. In this paper, silica sphere with uniform sphere morphology and amorphous structure was prepared by a sol-gel method, and the control of particle size was emphatically studied. The results showed that the particle size of the as-prepared silica sphere was obviously influenced by the raw materials concentration. The average size of the product increased from 0.66 μm to 0.90 μm when ethanol concentration increased from 7.14M to 9.55M, increased from 0.50 μm to 0.90 μm with the increase of ammonia concentration in the range of 1.88M to 2.36M, and increased from 0.47 to 0.90 μm while tetraethoxysilane concentration increased from 0.08M to 0.11M. Further study indicated that the silica particle size was also influenced by reaction temperature, it increased with the increase of temperature from 26°C to 28°C, and decreased with the further increase of temperature in the scope of 28°C to 32°C.

Application of ultrasound irradiation on sol–gel technique for corrosion protection of Al65Cu20Fe15 alloy powder

Al65Cu20Fe15 alloy powder was firstly encapsulated by the conventional sol–gel technique utilizing tetraethoxysilane (TEOS) as the precursor in order to improve its corrosion resistance. The optimization was based on nine well-planned orthogonal experiments (L9 (34)). Four main factors in the encapsulation process (i.e. reaction temperature, ethylenediamine concentration, TEOS concentration and feeding method) were investigated. According to the visual analyses of the result, the optimum condition was obtained. Based on the optimal condition in the conventional sol–gel technique, the encapsulation process was then conducted under ultrasonic irradiation. The effects of ultrasound amplitude and irradiation time on the encapsulation process were also studied. FTIR, XRD, SEM, DLS and EDS were also used to characterize the resulting sample. Finally, the corrosion inhibition efficiency of encapsulated powder attained 99.3% in the acidic condition of pH 1, and the average grain size (d50) of the encapsulated powder was just 4.8% larger than that of the raw powder, implying that there was a thin silica film on the surface of powder.