Showing papers on "Silane published in 1995"

Evidence for a Unique Chain Organization in Long Chain Silane Monolayers Deposited on Two Widely Different Solid Substrates

Abstract: We address the longstanding issue of substrate effects in alkylsiloxane monolayer self-assembly. With proper substrate prehydration, we observe formation of identical quality, compact, quasi-crystalline monolayers on oxidized silicon and gold substrates with widely different chemical character, the former capable of covalent bonding to the adsorbed molecules via silanol groups and the latter devoid of reactive surface sites. Infrared spectroscopy, ellipsometry, and wetting measurements show identical average film structures consisting of highly extended chains tilted at 10 (±2)° with significant end-gauche defect content. This observed substrate independence is consistent with our previous hypothesis that substrate-bound water promotes the decoupling of the organic film from the underlying solid surface.

Effects of Treatment and Storage Conditions on Ceramic/Composite Bond Strength

Abstract: During the past few years, the interest in using ceramic inlays and veneers has increased. New materials and methods have been introduced to bond these restorations to resinous materials. Since our knowledge of how to optimize such bonding is limited, the objective of this study was to test the hypothesis that various surface treatment variables and combinations of these variables affect the strength of the ceramic/composite interphase of ceramic inlays differently. The influences of material composition, surface-roughening method, silane treatment, silane heat treatment, and storage condition on bond strength were investigated. Three ceramics (Dicor, Mirage, Vitabloc), three surface-roughening methods (etching, sandblasting, grinding), three silane treatments (gamma-methacryloxypropyltrimethoxysilane [MPS], MPS+paratoluidine, vinyltrichlorosilane), two heat treatments (20 degrees C for 60 s, 100 degrees C for 60 s), and two storage conditions (24-hour dry, one yr in water at 37 degrees C) were studied. For each of the 108 combinations, five specimens were tested. Ceramic cylinders were treated according to group assignment and bonded to blocks of the same ceramic material with a dual-cured resin. The shear bond strength was determined, and the experimental factors were evaluated by analysis of variance. The results showed that surface-roughening method had the strongest effect on bond strength, while ceramic selection had the least significant effect. Of the surface-roughening methods, etching was associated with higher bond strength values than either sandblasting or grinding.(ABSTRACT TRUNCATED AT 250 WORDS)

Epitaxial growth of 3C–SiC films on 4 in. diam (100) silicon wafers by atmospheric pressure chemical vapor deposition

Abstract: Silicon carbide (SiC) films have been grown on 4 in. diam (100) silicon wafers by atmospheric pressure chemical vapor deposition, using propane, silane, and hydrogen. X‐ray photoelectron spectroscopy data confirm that the films are stoichiometric SiC, with no major impurities. X‐ray diffraction and transmission electron microscopy (TEM) data indicate that the films are single‐crystalline cubic polytype (3C) across the 4 in. substrates. With the exception of slip lines near the edge of the wafers, the films appear featureless when observed optically. The nitrogen concentration, as determined by secondary ion mass spectroscopy, is 4×1018 cm3. Cross‐sectional TEM images show a fairly rough, void‐free interface.

Adhesion of composite to porcelain with various surface conditions

Abstract: This study evaluated the adhesion of composite resin to five different surface conditions of porcelain samples that were treated with three kinds of silance agents. Two of these were commercially available Porcelain Liner M and Tokuso Ceramic Primer, and one was an experimental agent. The commercially available silane agents gave high bond strengths without hydrofluoric acid etching, which gave the greatest roughness on the porcelain surface. One component of these commercially available silane agents was γ-methacryloxypropyl trimethoxysilane, and the other was the carboxylic acid. As a result of the effective formation of siloxane bonds by mixing with acid solution, porcelain surface conditions did not affect the bond strenths.

Plasma‐Enhanced Chemical Vapor Deposition of Silicon Dioxide Deposited at Low Temperatures

Abstract: Thin silicon dioxide films are commonly used as insulating layers in metal-insulator structures, such as integrated circuits and multichip modules. These films are either thermally grown or deposited by thermal or plasma-enhanced chemical vapor deposition (PECVD). The advantage of PECVD is that lower deposition temperatures can be used avoiding defect formation, diffusion, and degradation of the metal layer. However, the low deposition temperature of the PECVD process has a negative effect on the quality of the silicon dioxide. Oxides produced at low temperatures contain more silanol and water impurities and are more porous than those deposited at higher temperatures. The deposition parameters, including substrate temperature, RF power, pressure, and reactant gas flow rate, affect the silanol and water concentration. The substrate temperature has the largest effect on the silanol concentration of the oxide. Using a large RF power, high pressure, and low nitrous oxide to silane ratio will minimize the silanol concentration at a given temperature. This will minimize the dielectric constant and maximize the etch resistance of the oxide produced.

The role of silanols in the modification of silica gel with aminosilanes

Abstract: In the modification of silica gel with aminoalkoxysilanes, silanols are present on the substrate surface and, after hydrolysis, in the silane molecule. The manner in which both types of silanols participate in the modification mechanism is elucidated, using nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopic techniques. Deuterium exchange of surface hydroxyls before silanation is used in order to distinguish initial surface silanols from those created in the course of the modification. Surface hydroxyls are the active sites for the bonding of coating molecules. Small patches of unreacted hydroxyls remain after modification. An FTIR peak at 3731 cm -1 is assigned to silane silanols, which are stable at low silane surface loadings.

Surface and Structural Properties of Silica Gel in the Modification with γ-Aminopropyltriethoxysilane

Abstract: Three mesoporous silica gels with variable pore size were modified with γ-aminopropyltriethoxysilane. The degree of surface hydration and hydroxylation and the available specific surface area were varied by a variation of pretreatment temperature. The effect of surface and structural properties of the silica substrate on both chemical and physical interaction of the silane with the silica were characterized using spectrophotometric and elemental analysis data. Total deposition is governed by the degree of hydration and the specific surface area of the substrate. Hydration causes hydrolysis and polymerization of the grafted molecules. On the dehydrated but hydroxylated substrate, a coating layer with a coverage of 2.05 molecules/nm2 is formed. The degree of chemical bonding is controlled by the number of surface hydroxyls if a relative excess of silane over surface silanols is used. On dehydroxylated silica a diverging reaction behavior is observed. The relative amount of physisorption increases largely. If the average pore radius r ⩽ 20 A steric hindrance lowers the surface coverage value.

Silane-crosslinkable, substantially linear ethylene polymers and their uses

Abstract: Curable, silane-grafted substantially linear ethylene polymers are described which are useful as wire and cable coatings, weatherstripping, fibers and the like. These silane-grafted polymers can be either filled or unfilled and cure quickly relative to many commercial coatings.

Hydrolytic stability of silanated zirconia-silica-urethane dimethacrylate composites

Abstract: SUMMARY The effect of the method of silanation of zirconia-silica hy 3-methacrylox ypropyItrimethoxysilane (MAPM) and 3-acryloxypropyltrimethoxysilane (APM) on the diametral tensile and transverse strength of composites made from these silanated fillers and a urethane dimethacrylate was determined after 0-lOSh of hoiling in water. The water sorption of these composites was also measur-?d at times up to 108 h. Silanation with either silane significantly increased the tensile and transverse strengths and decreased water sorption relative to comparable unsilanated controls. Silanation with MAPM from ethaaol solution at three times the minimum uniform coverage gave the best overall results, and the tensile strength tests appeared to be most predictive of effectiveness of the silane treatments.

High activity polyethylene catalysts

Abstract: An ethylene polymerization catalyst is prepared by impregnating a porous support, such as silica, with an organomagnesium compound such as a dialkylmagnesium compound, contacting the magnesium-containing support with a silane compound which is free of hydroxyl groups, such as tetraalkoxysilanes, e.g. tetraethyl orthosilicate, and incorporating a transition metal component, such as titanium tetrachloride, in a specific ratio to the magnesium and silane components. Activation of this catalyst precursor with dimethylaluminum chloride as a cocatalyst results in a catalyst system which is effective for the production of ethylene copolymers with multimodal molecular weight distributions.

Titanium nitride and multilayers formed by chemical vapor deposition of titanium halides

Abstract: A gaseous mixture of a titanium halide and silane is introduced to a plasma or thermal CVD reactor to induce a reaction such that a conformal and pure titanium film is deposited onto a semiconductor device within the reactor. The titanium halide has a chemical form of TiX 4 , where X is a halogen. Other gaseous combinations of the titanium halide, ammonia, hydrogen, a halogen and silane are subjected to plasma or thermal CVD to induce a reaction to deposit titanium silicide and titanium nitride films onto the semiconductor device. Successive CVD processes create bilayers of TiSi x /TiN or Ti/TiN, and/or trilayers of TiSi x /Ti/TiN onto the semiconductor device.

Process for the preparation of silane polysulfides

Abstract: Sulfur-containing organosilicon compounds useful as coupling agents in vulcanizable rubbers to enhance various properties, including low rolling resistance for automobile tires, are prepared. Preferred compounds include Ω, 106 '-bis (trialkoxysilylalkyl) polysulfides. In the preferred process scheme, sodium ethoxylate is reacted with hydrogen sulfide gas to yield sodium sulfide. The sodium sulfide is then reacted with sulfur to form the tetrasulfide. The product of that reaction is then reacted with chloropropyltriethoxysilane to form the compound 3,3'- bis (triethoxysilylpropyl) tetrasulfide. The use of hydrogen sulfide gas and sodium metal alcoholates provides an efficient and economical process.

Durability of Resin Bonds to Pure Titanium

Abstract: PURPOSE This study evaluated the bond strength and bond durability of new adhesive systems to pure titanium. MATERIALS AND METHODS Plexiglass tubes filled with composite were bonded to titanium discs. Groups of 24 samples were bonded using six different bonding systems. Subgroups of eight bonded samples were stored in an isotonic artificial saliva solution (37 degrees C) for 1, 30, or 150 days. In addition, the 30- and 150-day samples were thermal cycled for 7,500 or 37,500 cycles between 5 degrees C and 55 degrees C, respectively. After these storage conditions, all samples were debonded in tension. RESULTS The bond strength of a conventional bisphenol-A glycidyl methacrylate composite to sandblasted titanium was significantly lower than using chemomechanical bonding systems and decreased slightly during the storage time of 150 days. The additional use of a silane on sandblasted titanium resulted in an insignificant increase in bond strength and decreased over storage time to the same level as on sandblasted-only titanium. Statistically significant higher bond strengths were achieved either with the combination of silica coating and use of a conventional bisphenol-A glycidyl methacrylate composite or with the combination of sandblasting and the use of composites modified with a phosphate monomer. In the latter systems, the bond strengths were only limited by the cohesive strength of the composite resins. A new phosphate monomer containing composite showed a tendency to lose cohesive strength over time (statistically not significant). CONCLUSIONS Using chemomechanical bonding systems, ie, silica-coating systems or modified composites with adhesive monomers, resulted in 2 to 2.5 times increased bond strength to titanium compared with the bond strength of a conventional bisphenol-A glycidyl methacrylate composite. With chemomechanical bonding systems, the resin bond to titanium was durable over 150 days, even after being stored in water and thermal cycled.

Biotin-silane compounds and binding matrix containing these compounds

Abstract: The invention concerns a binding matrix containing a carrier material with an oxidic surface and a solid phase reactant covalently bound thereto via anchor groups which is capable of binding to at least one free reaction partner, which is characterized in that the solid phase reactant forms a diluted and essentially laterally homogeneous binding layer on the surface of the carrier material and that the anchor groups are silane groups and are linked to the solid phase reactant via a spacer molecule.

An Epoxy‐Silane Approach to Prepare Anode Materials for Rechargeable Lithium Ion Batteries

Abstract: A series of carbonaceous materials containing silicon and oxygen have been synthesized via pyrolysis of epoxy-silane composites prepared from hardened mixtures of epoxy novolac resin and epoxy-functional silane. Chemical composition of the pyrolyzed materials has been determined to be C{sub 1{minus}y{minus}z}Si{sub z}O{sub y} by a combination thermogravimetric analysis, Auger electron spectroscopy, carbon, hydrogen, and nitrogen analyses, and wet chemical analyses. Pyrolysis of the epoxy novolac resin gives pure carbon made up predominantly of single graphene sheets having lateral dimension of about 20 {angstrom} which are stacked like a house of cards. Pyrolysis of the pure epoxy-functional silane gives C{sub 0.50}Si{sub 0.19}O{sub 0.31} with a glassy structure. X-ray diffraction and electrochemical tests show that pyrolyzed materials prepared from mixtures initially containing less than 50% (by weight) silane are mixtures of the carbon single-layer phase and the glassy phase, while those initially with greater than 50% silane show predominantly the glassy phase. The reversible specific capacity of these materials increases from about 500 mAh/g for the pure disordered carbon up to about 770 mAh/g in the material which contains the most silicon and oxygen. However, the voltage profile develops hysteresis of about 1 V and the irreversible capacity associated with the firstmore » reaction within lithium increases as the silicon and oxygen contents are increased. Further work is needed to eliminate these drawbacks.« less

Infrared Study of the Adsorption of 1-Aminopropyltrialkoxysilanes on Silica at the Solid/Liquid Interface

Abstract: Infrared spectra are reported for silica in two states of surface hydroxylation immersed in carbon tetrachloride containing in particular (MeO)3SiCH2CH2CH2NH2. Adsorption involved hydrogen bonding between silanol and OMe or NH2 groups. At moderate coverages the silane was bonded to two or three silanol groups via OMe groups, but at high coverages reorientation in the adsorbed layer accompanied further adsorption, leading to 1:1 silanol:silane hydrogen bonding solely via amino groups. This behavior was unaffected by the degree of overall surface hydroxylation. Adjacent interacting surface silanol were more reluctant to be involved in bi- or tridentate bonding but at high silane concentrations also gave a 1:1 interaction via NH2 groups.

Laser marking of fluoropolymer composition

Abstract: Laser marking of pigmented fluoropolymer substrates is enhanced by using titanium dioxide pigment coated with organo silane.

Plasma-enhanced growth, composition, and refractive index of silicon oxy-nitride films

Abstract: Secondary ion mass spectrometry and refractive index measurements have been carried out on silicon oxy‐nitride produced by plasma‐enhanced chemical vapor deposition (PECVD). Nitrous oxide and ammonia were added to a constant flow of 2% silane in nitrogen, to produce oxy‐nitride films with atomic nitrogen concentrations between 2 and 10 at. %. A simple atomic valence model is found to describe both the measured atomic concentrations and published material compositions for silicon oxy‐nitride produced by PECVD. A relation between the Si–N bond concentration and the refractive index is found. This relation suggest that the refractive index of oxy‐nitride with a low nitrogen concentration is determined by the material density. It is suggested that the relative oxygen concentration in the gas flow is the major deposition characterization parameter, and that water vapor is the predominant reaction by‐product. A model, that combine the chemical net reaction and the stoichiometric rules, is found to agree with me...

Metal pretreated with an aqueous solution containing a dissolved inorganic silicate or aluminate, an organofunctional silane and a non-functional silane for enhanced corrosion resistance

Abstract: Painted metal sheet pretreated with an insoluble, composite layer containing siloxane. The composite layer is formed by rinsing the sheet with an alkaline solution containing at least 0.005M of a dissolved silicate or a dissolved aluminate, at least 0.1 vol.-% of an organofunctional silane and at least 0.02 vol.-% of a crosslinking-agent having two or more trialkoxysilyl groups. After the sheet is dried, the composite layer has a thickness of at least 10 Å. After being painted, the siloxane forms a tenacious covalent bond between the paint and the metal substrate.

Development of highly conductive n‐type μc‐Si:H films at low power for device applications

Abstract: Highly conductive phosphorus‐doped n‐type hydrogenated microcrystalline silicon (μc‐Si:H) films have been prepared by the usual (13.56 MHz) radio‐frequency glow discharge of silane (SiH4), phosphine (PH3), and hydrogen (H2) in an ultrahigh‐vacuum deposition system. The highest conductivity of the films obtained in this study is 100 S cm−1 after optimizing the hydrogen dilution ratio, chamber pressure, substrate temperature, and doping concentration of phosphorus. The formation of microcrystallinity in the material has been studied by transmission electron microscopy, x‐ray‐diffraction studies, and Raman spectroscopy. The volume fraction of microcrystallinity in these amorphous‐microcrystalline mixed‐phase materials has been estimated from Raman spectra. Sizes of the crystallites and volume fraction of microcrystallinity vary with hydrogen dilution, chamber pressure, and substrate temperature. The variations in the properties with deposition parameters have been explained in terms of the growth kinetics. The n‐type μc‐Si:H thin film, thus developed, has been applied in the first cell of a double‐junction amorphous silicon solar cell. The prepared p‐i‐n–p‐i‐n stacked cell employing the n‐type μc‐Si:H film has exhibited appreciable improvement in open‐circuit voltage, fill factor, and efficiency compared to the one with amorphous n layer in the inner n–p contact. Degradation of the cells prepared with and without μc‐n layer has been studied.