Papers by Keyword: TEOS

Abstract: Mercury pollution through water causes several dangerous diseases. Various efforts have been made to reduce mercury pollution. One of them is by using sorbent. Many ways to improve absorption efficiency, one of which is using magnetic sorbents. This study focused on the effect of grain size and the concentration of Mn_0.25Fe_2.75O₄@SiO₂ core-shell on mercury absorption efficiency. The synthesis of Mn_0.25Fe_2.75O₄@SiO₂ with 6 and 8 mL of TEOS was carried out through coprecipitation and sol-gel methods. The characterization using XRD, VSM, and FTIR was conducted to determine grain size, properties, and material functional groups proving that SiO₂ was successfully covered on the Fe₃O₄ surface. The percentage of absorption was found by using the AAS instrument. Diffraction data confirmed the presence of Fe₃O₄ and the amorphous SiO₂ phase. According to the Rietveld analysis of all samples demonstrated the particle size of Mn_0.25Fe_2.75O₄ around 11-12 nm. The Mn_0.25Fe_2.75O₄ core had superparamagnetic properties for magnetic separation, and the SiO₂ shell could protect the core of being oxidized or dissolved under acid condition. FTIR results showed the sample had a functional group of the main components of Fe-O and SiO₂ at a wavenumber of 420-507 cm^-1 and 801 cm^-1 (stretching) and 1078 cm^-1 (bending), respectively. The results of the mercury absorption test indicated that the smaller the grain size and the higher the concentration of TEOS, the percentage of mercury uptake would increase. In addition, the absorption percentage increased with the duration of absorption time given.

Abstract: Silica aerogel is a nanostructured porous solid material. It has a low bulk density, low thermal conductivity and can be hydrophobic. In this work, hydrophobic silica gel, a material used to form aerogel, is used instead of its powder form to avoid ultrafine air particles pollution. It is used to surface modified materials to make the materials superhydrophobic and still withstand physical abrasion that ordinary aerogel would not able to do. The superhydrophobic silica aerogel coating was designed by mixing the hydrophobic gel with DOW CORNING^® 2405 resin as binder and varying DOWSIL^™ Z-6137 silane and tetraethyl orthosilicate (TEOS). The coating is characterized by the static contact angles (CA) and abrasion test. Scanning electron micrographs of different coating compositions were investigated. Results show that the hydrophobic gel mixed with resin and Z-6137 silane have contact angle >179º. Superhydrophobic silica aerogel coating can be utilized as material coatings for glass, fiber, polymer, etc.

Abstract: In-situ silica nanoparticles with ammonium laurate surfactant in natural rubber latex composites were characterized to describe the reinforcement mechanism in enhanced mechanical properties. In-situ sol-gel method was introduced to generate silica nanoparticles in natural rubber latex using a mole ratio of water-to-TEOS of 28.9 stirring at room temperature for 24 hours. The addition and effect of adding ammonium laurate surfactant for enhancing dispersion and compatibility between silica nanoparticles and rubber matrix was also studied. The natural rubber latex was then vulcanized by electron beam radiation at 200 kGy. The silica content in rubber composites made in-situ, was analyzed by TGA, showed an increase from 3.08 phr to 8.92 phr, corresponding to addition of TEOS amounts of 10 phr to 30 phr, respectively. The dispersion of silica nanoparticles in rubber matrix with ammonium laurate surfactant was improved and exhibited less aggregation than rubber composites absent of ammonium laurate surfactant as evidenced by SEM-EDX. The increase of silica content in rubber composites exhibited lower swelling ratio and higher crosslink density when compared with neat natural rubber. Also, the modulus at 100% and 300% strain also increased with increasing silica nanoparticles incorporation in contrast to tensile strength.

Abstract: In this work, hydrophobic of modified SiO₂ coating for self cleaning material were prepared by dip-coating methods and solvothermal manual. SiO₂ was successfully prepared from silica sand by purified followed sol-gel methods. Tetraetoxysilane (TEOS) and Hexamethyldisilanze (HMDS) were used as surface chemical modification agents with varied mass of SiO₂, which were 1, 2, 3, and 4 g. X-ray fluorescence spectrometer (XRF) , X-ray powder diffraction (XRD), Particle size analyzer (PSA), Ultraviolet–visible spectrophotometer (UV-Vis), and Water contact angle (WCA) were employed to investigate the element composition, crystal structure, size of particles, transparency, and hydrophobicity of coating. The results indicated that modified SiO₂ coatings has hydrophobic feature as self cleaning material (WCA > 90˚) for indium tin oxide (ITO) glass.

Abstract: The spherical silica particles were prepared by sol-gel method with TEOS as precursor, ethanol as solvent in the presence of ammonia. The effects of reaction temperature and the amount of ammonia and TEOS on the size and morphology of silica particles were investigated. The hydrolysis temperature , alkali and TEOS content does not affect the morphology of silica, the silica particles were spherical; With the increase of hydrolysis temperature, particle size of silica showed first increased and then decreased, when the hydrolysis temperature is 30 °C, the silica particle size up to 0.6 μm, when the hydrolysis temperature is 60 °C, the silica particle size is 0.15 μm; With the increase of the content of alkali, silica particle size showed first increased and then decreased, when the alkali content is 20 ml, the silica particle size up to 0.6 μm and when the alkali content is 10 ml, the silica particle size is 0.2 μm; With the increase of TEOS dosage, the amount of spherical silica increased and the particle size of silica spherical particles first increased and then decreased.

Abstract: Hybrid adhesives epoxy-silica-zirconia were prepared and applied to bond aluminum sheet specimens. Silica nanoparticles were synthesized with the sol-gel “in situ” technique utilizing two different precursors, namely tetraethyl orthosilicate (TEOS) and 3 glycidyloxypropyltrimethoxysilane (GPTMS). Zirconia nanoparticles were prepared also with sol-gel technique and added to the hybrid adhesives before curing. The adhesive properties of the prepared materials were improved after performing several physical and chemical treatments to the aluminium specimens. The best apparent shear strength tests were for the adhesive hybrid materials prepared at 100°C with TEOS.

Abstract: In this paper we presented the synthesis of TEOS with photoresist in order to use it like a hybrid material for 3D printer on the micrometer scale by means of the two-photon polymerization process, in which two photon are absorbed simultaneously by the material using an ultrafast laser causing its polymerization. We analyzed the mix of TEOS and photoresist with UV-VIS and FTIR spectrometers, checking that complies with two important conditions: has an optical transmission at 780 nm and absorbs at 390 nm. Finally we fabricated micro-structures with a new hybrid material; TEOS does not absorb the laser in this system and does not interfere with the formation of a three-dimensional structure. After formation the 3D microstructure, samples were heated to form the SiO. These samples of microstructures were observed under digital microscope and SEM.

Abstract: In this study, hydrophilic-oleophobic antireflective coatings with high transmittance were prepared via simplely mixing the base-catalyzed TEOS and acid-catalyzed MTES with different weight ratio. The refractive index of the AR coatings increase continuously from 1.23 to 1.44. When the weight ratio of acid-catalyzed MTES reached 60%, a hydrophilic-oleophobic antireflective coatings with a high transmittance of 99.09% can be obtained. The water contact angle and the oil contact angle of the coating are 113.8o and 74.4o, which can effectively prevent the absorption of water and polar organic molecules from the environment.

Abstract: In order to research the structure and morphology of silica after calcined at different tempreture, as well as the influence of particles shape with coupling agent. Use TEOS as raw material, prepared inorganic silica particles by acid-catalyzed, Characterization methods have FT-IR, XRD, TG-DSC, SEM. The results showed that: only the presence of characteristic absorption peak of SiO₂ when the calcination temperature reached 1000°C, tetragonal α-cristobalite formed when reached 1500°C. porous structures densified when 1500°C, obtained by a small particle size and a good degree of dispersion. KH550 will affect particle morphology characteristics.

Abstract: Humidity sensitive layers elaborated from pure HMDSO and TEOS by PECVD technique have been studied. Humidity sensing properties including impedance relative humidity (RH) and current RH characteristics were investigated. TEOS films show higher sensitivity and excellent linearity over the explored range of humidity (20–95% RH). However, HMDSO films exhibits a small response and recovery of about 8 and 34 s for humidification and desiccation, respectively, in addition to very low hysteresis (2%). Structural analyses of sensitive layers were characterized by Fourier transform infrared spectroscopy (FTIR).