Tetraethyl orthosilicate, TEOS

Various inorganic esters have been claimed as coupling agents for reinforced plastics, including aminobenzyl phosphonates, dicetylisopropylborate, alkoxy compounds of aluminum, zirconium and titanium, zircoaluminates, and numerous substituted titanates [1]. These metal alkoxides could function in a similar manner to the orthosilicates by reacting with hydroxylated substrates. Like the simple orthosilicates such as tetraethyl orthosilicate (TEOS), it is less evident how an-... 

MOCVD of Silica. Considerable work is being done with the MOCVD of silica, which is rapidly expanding in semiconductor processing. The most common MOCVD reaction is the decomposition of tetraethyl orthosilicate (TEOS), shown in simplified form as follows ]... 

A widely used glass is phosphosilicate (PSG), which is used extensively in semiconductor devices as a passivation and planarization coating for silicon wafers. It is deposited by CVD by the reaction of tetraethyl orthosilicate (TEOS) (C2H50)4Si, and trimethylphosphate PO(OCH3)3, in a molecular ratio corresponding to a concentration of 5 to 7% P. Deposition temperature is usually 700°C and pressure is 1 atm. 

The first category is layered organosilanes. Layered alkylsilanes are synthesized from akyltrialkoxysilane [CH3(CH2) iSi(OR)3, R is often CH3 or C2H5] and tetraethyl orthosilicate (TEOS) [62-66]. Alkoxy groups are hydrolyzed and condensed into... 

Phenylene-bridged periodic mesoporous organosilicas, with both amorphous and crystal-like walls, (referred to in the following as AW-Ph-HMM and CW-Ph-HMM, respectively) were synthesized and characterized as previously reported [6,7]. BTEB was used as a precursor for both solids the surfactant was Brij-76 (Ci8H37(OCH2CH2)nOH) in acidic media for AW-Ph-HMM and octadecyl-trimethylammonium bromide(ODTMA) in basic media for CW-Ph-HMM. A purely siliceous MCM-41 sample was also synthesised, the first step being the solution of octadecyltrimethylammonium bromide in a basic aqueous solution (NH3), kept a 333 K. Tetraethyl orthosilicate (TEOS) was then added in all cases dropwise, and the mixture stirred for 24h at room temperature (H20 34.2 g/ NH3 (15%) 8.52 g/ ODTMA 0.73 g TEOS 3.24 g). After further 24 hours in hydrothermal conditions at 368 K, the sample... 

S.-i. Kawano, S.-i. Tamaru, N. Fujita, and S. Shinkai, Sol-gel polycondensation of tetraethyl orthosilicate (TEOS) in sugar-based porphyrin organogels Inorganic conversion of a sugar-directed porphyrinic fiber library through sol-gel transcription processes, Chem. Eur. J., 10 (2004) 343-351. 

Later, Thangaraj et al. (275,281) developed a novel, improved route (prehydrolysis method) for the preparation of good quality TS-1 samples. In this method the silica source (tetraethyl orthosilicate TEOS) in Ao-propanol was first hydrolyzed with 20% aqueous TPAOH solution prior to the (dropwise) addition of titanium butoxide in dry iso-propanol under vigorous stirring. Crystallization was done statically at 443 K for 1-5 days and the solid was calcined at 823 K for 10 h. The TS-1 samples thus obtained exhibited high catalytic activity in hydroxylation reactions. 

The 4,4 -dibromobiphenyl was used as the starting material The strategy taken for the synthesis of the organosilica was to carry out Grignard-type reaction to incorporate tetraethyl orthosilicate (TEOS) to 4,4 -dibromobiphei5rl to create 4,4 -Bis(triethoxysilyl)biphenyl. Materials from this procedure had been subjected to polymerization surfactant-mediated polymerization. The product obtained was a white powder aggregate. Shown in Table 47.1 are the formulations used for the samples and the heat treatment. 

Nakamura and Matsui [71] prepared silica nanotubes as a spin-off product of sol-gel synthesis wherein tetraethylorthosilicate (TEOS) was hydrolyzed in the presence of ammonia and D, L-tartaric acid. Ono et al. [72] showed that certain cholesterol derivatives can gelate tetraethyl orthosilicate (TEOS) to obtain tubular silica structures. Using cholesterol based gelators nanotubes of transition metal (Ti, V and Ta) oxides can also be prepared. The organogelators used in these processes are chiral diamino... 

In this paper, we report the synthesis of mesoporous silica and alumina spheres with nanometer size (80 to 900 nm) in the present of organic solvent with aqueous ammonia as the morphological catalyst to control the hydrolysis of tetraethyl orthosilicate (TEOS) and aluminum tri-sec-butoxide.1181 Mesoporous silica spheres show hexagonal arranged pores with monodispersed pore sizes ( 2.4 nm) and high surface areas ( 1020 m2/g) similar to MCM-41. A large pore ( 10 nm) mesoporous alumina sphere templated by triblock copolymer is thermally stable. Calcined alumina sphere shows disordered mesoporous arrays with relatively uniformed pore size distribution and high surface areas ( 360 m2/g). 

In 1995, Tanev and Pinnavaia [1] have reported the synthesis of a new type of mesoporous molecular sieve designated as the hexagonal mesoporous silica (HMS). Instead of using the ionic inorganic precursor and surfactant as in the case of MCM-41 [2], HMS is manufactured by hydrolysis reaction between a neutral inorganic precursor, tetraethyl-orthosilicate (TEOS) and a neutral primary amine surfactant (8-18 carbons). HMS possesses numerous favourable characteristics, but, like MCM-41, its synthesis process can only be concluded by the removal of the surfactant. This was reportedly done either by calcination at 630°C or by warm ethanol extraction [1]. 

Al-containing SBA mesoporous solid was prepared as reported 9 mL tetraethyl orthosilicate (TEOS) and the calculated amount of aluminum tri-tert-butoxide, in order to obtain a well defined Si/Al ratio equal to 10, were added to 10 mL of HC1 aqueous solution at pH=1.5 water. This solution was stirred for over 3 h and then added to a second solution containing 4 g triblock poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (EO20PO70EO20 Aldrich) in 150 mL of HC1 aqueous solution at pH=1.5 at 313 K. The mixture was stirred for another 1 h and allowed to react at 373 K for 48 h. The solid product was filtered, dried at 373 K, and finally calcined in air flow (9 L h 1) at 823 K for 4 h with a heating rate of 24 K h"1. The SBA-15 was prepared according to the literature [11]. In what follows, the samples are denoted AlSBA and SBA, respectively. 

In a recent study the IT-catalyzed rearrangement of allyl (3,5-di-terr-butylphenyl) ether was used as selective probe for the outer surface activity.44 The best passivation results were obtained by treatment of the Beta crystals with tetraethyl orthosilicate (TEOS). Slow hydrolysis of TEOS by traces of water present in the pores of the zeolite provides a thin, porous layer of amorphous silica and leads to complete outer surface passivation on 1 p,m crystals. 

A preparation in two steps has been chosen hrst a new hybrid silica precursor P-CDAPS, containing P-CD groups and amine functions, has been prepared and characterized. Then, this precursor has been co-condensed with tetraethyl orthosilicate (TEOS) via a sol-gel process involving the use of surfactant. We chose the anionic surfactant sodium dodecylsulfate (SDS). The chemical and structural characterization combined with adsorption tests of p-nitrophenol and lead nitrate led to the evaluation of the accessibility and the effectiveness of the binding functions in these hybrid materials. 

The parent siliceous MCM 41 material was synthesised by hydrolysis of tetraethyl orthosilicate (TEOS) under mild alkali conditions, based on a procedure described by Schmidt and co-workers. ... 

Commercially available tetraethyl orthosilicate (TEOS), dodecyltrimethyl- ammonium chloride (DTMACl) and trimethylammonium hydroxide (TMAOH) were mixed in water and the solution was stirred for 4 h at room temperature. The composition of the gel mixture was Si DTMACl TMAOH H2O = 1 0.6 0.3 60. White precipitates were filtered and dried at 393 K. This as-synthesized powder was calcined at 903 K for 4 h to obtain MCM-41. The silica was stirred vigorously in toluene containing a monolayer equivalent amount (1.0 per 1 nm ) of [l-(2-aminoethyl)-3-aminopropyl]trimethoxysilane... 

Lastly, if the SiOj deposition is highly conformal, the regions between closely spaced metal lines may be filled without the production of gaps. If the film thickness is equal to half the space width, the space will fill completely and the comers of the film will join at the top of the space, thereby leaving a nearly planar film. Examples of CVD SiOj processes capable of the required high degree of conformality are ECR deposition and tetraethyl orthosilicate (TEOS) plasma CVD-enhanced. While this approach yields local planarization above closely spaced lines, the wide spaces between metal lines are not filled, and thus a sharp step is experienced at the edge of such spaces. Therefore, this approach is often coupled with SOG or resist etch-back processes or CMP.< >... 

A nonmetallic element, silicon, was prepared sonodiemically by reducing tetraethyl orthosilicate (TEOS) with a colloidal solution of sodium. The product was obtained as 2-5 nm sized, highly aggregated partides. The silicon exhibited a luminescence similar to that of porous silicon. This procedure is suggested as a general sonochemical reduction leading to the formation of metallic nanopartides [26]. 

The preparation of the europium oxide-doped silica nano-particles (99.0S1O2-I.OEU2O3 mol%) was different. It was also carried out by the hydrolysis of tetraethyl orthosilicate (TEOS) in the presence of H2O, ethanol, and a europium nitrate solution. 25% aqueous ammonia was added dropwise during the sonication. In this way, europium oxide incorporated into silica particles was obtained. 

The sol-gel process is a novel technique for the preparation of various inorganic oxide glasses at low temperatures without melting.51 They are produced by condensation-polymerization of a suitable metal alkoxide. For instance, the sol-gel process of tetraethyl orthosilicate (TEOS) consists of the hydrolysis reaction... 

Mesoporous SBA-15 silica that contains both benzenesulfonic acid and propylamine was prepared by the sol-gel technique from tetraethyl orthosilicate (TEOS, 120), 2-(4-chlorosulfonylphenyl)ethyl-trimethoxysilane (119) and (3-aminopro-pyl)trimethoxysilane (118) in the presence of poly(ethylene glycol)-Z)/ock-poly (propylene glycol)-Z)/ock-poly(ethylene glycol) [P123] (Scheme 3.34). ... 

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