- Structural and Photoluminescence properties of nepheline-structure NaAlSiO4:Dy3+ nanophosphors
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Most of the phosphors are composed of known host material with the incorporation of some percentage of an activator into the matrix. In this work Dy3+-activated NaAlSiO4 phosphors have been synthesized using sol-gel combustion techni
- Kumar, Ashwini,Dhoble,Peshwe,Bhatt, Jatin
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- Paralinear oxidation of silicon nitride in a water-vapor/oxygen environment
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Three Si3N4 materials were exposed to dry oxygen flowing at 0.44 cm/s at temperatures between 1200° and 1400°C. Weight change was measured using a continuously recording microbalance. Parabolic kinetics were observed. When the same materials were exposed to a 50% H2O-5% O2 gas mixture flowing at 4.4 cm/s, all three types exhibited paralinear kinetics. The material was oxidized by water vapor to form solid SiO2. The protective SiO2 was in turn volatilized by water vapor to form primarily gaseous Si(OH)4. Nonlinear least-squares analysis and a paralinear kinetic model were used to determine parabolic and linear rate constants from the kinetic data. Volatilization of the protective SiO2 scale could result in accelerated consumption of Si3N4. Recession rates under conditions more representative of actual combustors were compared with the furnace data.
- Fox, Dennis S.,Opila, Elizabeth J.,Nguyen, Quynh Giao N.,Humphrey, Donald L.,Lewton, Susan M.
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- Controlled growth of in situ silica in a NR/CR blend by a solution sol-gel method and the studies of its composite properties
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Silica is grown in situ into a natural rubber (NR)/chloroprene rubber (CR) blend (at 40/60 ratio), by a solution sol-gel method, where the silica content in rubber blend is increased in a controlled manner exceeding the limit found for the same blend ratio in the soaking sol-gel method. Reaction conditions have been optimized to get adequate conversion of tetraethoxysilane (TEOS, a silica precursor) to silica. Rheological, thermal, mechanical and viscoelastic properties of all the composites are compared with those of the unfilled rubber blend at similar conditions. Thermal and mechanical properties of the composites are found to improve consistently as silica content in the composite increases owing to increased rubber-filler interaction as revealed in dynamical mechanical analysis (DMA). Further improvement in the properties is observed for a particular composite where a silane coupling agent ((γ-aminopropyl)trimethoxysilane, γ-APS) is used in the reactive sol-gel system during in situ generation of silica. This is attributed to the uniform distribution of silica in the rubber matrix and strong rubber-filler interaction, caused by bifunctionality of silane, as revealed by morphology and DMA studies respectively. The reinforcement effect of silica is evaluated by comparing the experimental results with theoretical values obtained from the Guth-Gold model and the modified Guth model. The present study supplements the in situ silica generation in NR/CR blend of 40/60 ratio, following the solution sol-gel method, to the earlier study involving the soaking sol-gel method where the maximum reinforcement was found for this composition.
- Bansod, Naresh D.,Kapgate, Bharat P.,Das, Chayan,Basu, Debdipta,Debnath, Subhas Chandra,Roy, Kumarjyoti,Wiessner, Sven
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- Zirconium phosphate combined with Ru/C as a highly efficient catalyst for the direct transformation of cellulose to C6 alditols
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The selective transformation of cellulose to C6 alditols provides a feasible route towards the sustainable synthesis of chemicals and fuels. Herein, the catalytic performance of amorphous zirconium phosphate (ZPA) combined with 5 wt% Ru/C was evaluated in the direct conversion of cellulose to C6 alditols (sorbitol and mannitol) under hydrothermal conditions. The yield of C6 alditols reached 63.5% and 85.5% with microcrystalline cellulose and ball-milled cellulose as the feedstock, respectively. This hybrid catalyst was developed to convert concentrated cellulose to obtain C6 alditols with a high concentration of 68.8 mg mL-1 in the final products. The high yield of C6 alditols from cellulose was ascribed to the fact that ZPA favoured the adsorption of cellulose and promoted its depolymerization to cellobiose and glucose, which was hydrogenated immediately to C6 alditols over Ru/C. The weak adsorption of C6 alditols over ZPA inhibited the dehydration of C6 alditols to sorbitan. Furthermore, ZPA exhibited excellent hydrothermal stability and could be reused for several runs. This journal is the Partner Organisations 2014.
- Liao, Yuhe,Liu, Qiying,Wang, Tiejun,Long, Jinxing,Ma, Longlong,Zhang, Qi
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- Influence of annealing temperature on structural and optical properties of SiO2:RE2O3 [RE = Y, Gd] powder
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SiO2:RE2O3 [RE = Y, Gd] powder were prepared by wet chemical technique and the prepared binary oxides annealed at 500 °C and 900 °C. The crystalline structure, phase transformation, and surface morphologies of as-prepared and annealed samples were investigated by XRD and TEM. The normal transmission was measured using FTIR spectroscopy. Optical properties have been studied with UV-Vis spectroscopy and PL study. XRD results shows that the as prepared samples of SiO2:RE2O3 [RE = Y, Gd] powder has mixed phases of RE(NO3)3 and Si(OH)3. However, cubic rare earth oxide phase alone is found for annealed samples. The strain values are calculated from W-H plot for annealed samples. TEM micrograph shows that the samples are composed of individual spherical nanocrystallites at 500 °C and aggregated nanocrystallites at 900 °C. From the UV-Vis spectra, it is found that the position of the absorption peak is shifted toward the higher wavelength side when annealing temperature is increased. In the PL spectra, the broad emission bands are observed between 570-600 nm and the presence of O-Si-O (silica) and metal oxide is confirmed by FTIR spectra.
- Ahlawat, Rachna
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- Interactions of water vapor with oxides at elevated temperatures
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Many volatile metal hydroxides form by reaction of the corresponding metal oxide with water vapor. These reactions are important in a number of high temperature corrosion processes. Experimental methods for studying the thermodynamics of metal hydroxides include: gas leak Knudsen cell mass spectrometry, free jet sampling mass spectrometry, transpiration and hydrogen-oxygen flame studies. The available experimental information is reviewed and the most stable metal hydroxide species are correlated with position in the periodic table. Current studies in our laboratory on the Si-O-H system are discussed.
- Jacobson, Nathan,Myers, Dwight,Opila, Elizabeth,Copland, Evan
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- Ionic Liquid-Hybrid Molecularly Imprinted Material-Filter Solid-Phase Extraction Coupled with HPLC for Determination of 6-Benzyladenine and 4-Chlorophenoxyacetic Acid in Bean Sprouts
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A new method involving ionic liquid-hybrid molecularly imprinted material-filter solid-phase extraction coupled to high-performance liquid chromatography (IL-HIM-FSPE-HPLC) was developed for the simultaneous isolation and determination of 6-benzyladenine (6-BA) and 4-chlorophenoxyacetic acid (4-CPA) in bean sprouts. Sample preconcentration was performed using a modified filter, with the new IL-HIM as the adsorbent, which shows double adsorption. The first adsorption involves special recognition of molecular imprinting, and the second involves ion exchange and electrostatic attraction caused by the ionic liquid. This method combines the advantages of ionic liquids, hybrid materials, and molecularly imprinted polymers and was successfully applied to determine 6-BA and 4-CPA in bean sprouts. The adsorption of 6-BA to IL-HIM is based on selective imprinted recognition, whereas the adsorption of 4-CPA is mainly dependent on ion-exchange interactions.
- Han, Yehong,Yang, Chunliu,Zhou, Yang,Han, Dandan,Yan, Hongyuan
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- Near-infrared spectroscopic study of [AlO4Al12(OH)23(H2O)12]7+-O-Si(OH)3 nitrate crystals formed by forced hydrolysis of Al3+ in the presence of TEOS.
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The polymer [AlO4Al12(OH)23(H2O)12]7+-O-Si(OH)3 was prepared by forced hydrolysis of Al3+ up to an OH/Al molar ratio of 2.0 in the presence of monomeric orthosilicic acid. Crystalline material was obtained by slow evaporation. Although the near-infrared spectra of the Al13-sulfate and Al13-O-Si(OH)3 are very similar, there are differences related to the bonding of the -O-Si(OH)3 group to the Al13-unit. The strong complex of bands around 7000 cm(-1) associated with the overtones and combination bands of the OH-stretching modes for Al13-sulfate is much weaker for Al13-O-Si(OH)3 and the opposite is true for the complex of bands around 5000 cm(-1) associated with the water overtone and combination modes, suggesting that the outer OH-groups of the Al13-unit are involved in the formation of the new Al13-O-Si(OH)3 units. A weak band around 7370-7631 cm(-1) is interpreted as the overtone of the Si-OH stretching vibration around 3740 cm(-1). A low intensity band, absent for Al13-sulfate and -nitrate is observed around 5550-5570 cm(-1) and is interpreted as the overtone of the OH-stretching mode of the OH-groups in the vicinity of the central AlO4 in the Al13-unit around 2890-2935 cm(-1). The interaction between the -O-Si(OH)3 group and the Al13-unit has a small influence on other bands like the combination modes of water in the 4400-4800 cm(-1) region, which show a small shift towards higher wavenumbers. The internal OH-groups in the Al13-complex are relatively shielded by the water molecules and therefore do not reflect the influence of the -O-Si(OH)3 in their band positions.
- Kloprogge,Ruan,Frost
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- Morphosynthesis of complex inorganic forms using pollen grain templates.
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Porous micron-sized particles of silica, calcium carbonate or calcium phosphate are prepared with complex morphologies by template-directed synthesis employing intact pollen grains; the materials adsorb and release drug molecules and can be functionalized
- Hall, Simon R,Bolger, Helen,Mann, Stephen
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- Effect of polyethylenimine on hydrolysis and dispersion properties of aqueous Si3N4 suspensions
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The roles of polyethylenimine (PEI) in the hydrolysis and dispersion properties of aqueous Si3-N4 suspensions were studied in terms of the hydrolysis, adsorption, electrokinetic, and rheological measurements. It was found that the pH change of the suspensions in the acidic environment could be minimized in the presence of ≥ 0.5 dwb% PEI. The ammonia and oxygen measurements suggest that this phenomenon is primarily attributed to the buffer mechanism generated by the ionized PEI, instead of the protection mechanism. The constant pH enables the suspensions to retain a better stability with time at acidic pH. The adsorption of PEI on Si3N4 is a high-affinity type at highly basic pH, but is a low-affinity type at acidic pH. As the PEI amount increases, the adsorption shifts the isoelectric point (IEP) of Si3N4 from pH 5.9 to pH ~11 until complete coverage is attained. The stability of Si3N4 suspensions is found to depend strongly on the saturated adsorption of PEI, which is as a function of the pH and PEI amount. Once the saturated adsorption limit is reached, the excess free PEI molecules become more detrimental to the stability with increased solid loading. The stabilization mechanisms of Si 3N4 suspensions by PEI were discussed in detail.
- Zhu, Xinwen,Uchikoshi, Tetsuo,Suzuki, Tohru S.,Sakka, Yoshio
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- POLYMERIZATION OF SILICIC ACID ADSORBED ON ALUMINIUM HYDROXIDE
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Factors controlling the absorption of silicic acid on aluminium hydroxide from aqueous solution and the polymerization of adsorbed silicic acid were studied.Measurements included the amount of silicic acid adsorbed on aluminium hydroxide, the amount and size distribution of the polysilicic acid formed, and the differential thermal analysis curve of aluminium hydroxide which had adsorbed silicic acid.The adsorption and polymerization of silicic acid are affected by pH, the relative amounts of silicic acid and aluminium hydroxide, the reaction time between monosilicic acid and aluminium hydroxide, the formation of amorphous aluminosilicate.The amount of adsorbed silicic acid and the rate of its polymerization are maximum at pH 9.0-9.5.A part of adsorbed monosilicic acid reacts with aluminium hydroxide to form an aluminosilicate.In an early stage of the polymerization of adsorbed silicic acid, the polymerization mainly proceeds by the reactions between monosilicic acids and between monosilicic and polysilicic acids; the particle sizes of polysilicic acids gradually increase with time.When the polymer particles grow large enough to touch neighboring polymers, the growth rate of polymer particles becomes faster due to the polymer-polymer reactions.
- Yokoyama, Takushi,Nakamura, Osamu,Tarutani, Toshikazu
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- Mass spectrometric identification of Si-O-H(g) species from the reaction of silica with water vapor at atmospheric pressure
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A high-pressure sampling mass spectrometer was used to detect the volatile species formed from SiO2 at temperatures between 1200° and 1400°C in a flowing water vapor/oxygen gas mixture at 1 bar total pressure. The primary vapor species identified was Si(OH)4. The fragment ion Si(OH)3+ was observed in quantities 3 to 5 times larger than the parent ion Si(OH)4+. The Si(OH)3+ intensity was found to have a small temperature dependence and to increase with the water vapor partial pressure as expected. In addition, SiO(OH)+, believed to be a fragment of SiO(OH)2, was observed. These mass spectral results were compared to the behavior of silicon halides.
- Opila, Elizabeth J.,Fox, Dennis S.,Jacobson, Nathan S.
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- Investigation of the pH Dependence of the Kinetics of Quartz Dissolution at 25 deg C
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The dissolution kinetics of two samples of commercial ground Fontainebleau sand consisting of >99.6percent quartz are studied at 25 deg C in constant ionic strength conditions and in the pH range 4.5 - 10.5.The strong pH dependence of the reaction rate is attributed to changes in the surface speciation of quartz.The ionization of the surface silanol groups is investigated using potentiometric methods and the results are compared with literature data using a simple surface speciation model that accounts for the effects of the electrical double layer on the hydrogen ion activity.The surface speciation model produces titration curves in good agreement with the experimental data and offers an interpretation of the relationship between the density of ionized groups, , and pH.The rate constant, k+, for the dissolution reaction: SiO2(solid) + 2H2O -> Si(OH)4(aq) is determined from 25 experiments as: log k+ = -14.547 +/- 0.162 + 0.361 +/- 0.022 pH at 25 deg C, ionic strength of 0.010 mol dm-3 and pH in the range 4.5 - 10.5.The constant, k+, is in units of mol m-2 s-1.The results are compared with the available literature data at 25 deg C.Although there is general agreement between the experimental data and the surface speciation model concerning the pH dependence of the dissolution rates, the variation between the absolute values of the rate constants from different quartz samples is large.The pH dependence observed in this work and that of Brady and Walther, is consistent with a pK for the dissociation of surface silanol groups and surface density of terminal silanol groups of ca. 7.5 and 11 nm-2, respectively.A slope of ca. 0.33 obtained from the regression of pH and log k+ is predicted from the surface model.Similar gradients have been observed in other studies using quartz and also for a range of other silicate minerals for solution pH >/= 7.
- House, William A.,Orr, Douglas R.
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- Preparation and luminescence property of red-emitting hardystonite phosphors by near-ultraviolet irradiation
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A1.95ZnSi2O7:Eu0.05 3+ (A=Ca, Sr, Ba) red phosphors were prepared by combustion-assisted synthesis method and their efficient red emission under near ultraviolet (UV) were observed. The luminescence and crystallinity were investigated using luminescence spectrometry and X-ray diffractometer, respectively. The emission spectrum shows that the most intense peak is located at 614 nm, which corresponds to the 5D0→7F2 transition of Eu3+. These phosphors have two main excitation peaks located at 394 and 465 nm, which match the emission of UV and blue light-emitting diodes, respectively. Thus, these phosphors could be used as red components for white light-emitting diodes.
- Yao, Shanshan,Xue, Lihong,Yan, Youwei,Yan, Mifang
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- The formation, precipitation and structural characterisation of hydroxyaluminosilicates formed in the presence of fluoride and phosphate
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Hydroxyaluminosilicates (HAS) are important secondary mineral phases formed by the reaction of silicic acid (Si(OH)4) with aluminium. Two discrete forms of HAS have been identified (HASA and HASB) and their structures and
- Strekopytov, Stanislav,Exley, Christopher
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- Sonochemical synthesis of silica and silica sulfuric acid nanoparticles from rice husk ash: A new and recyclable catalyst for the acetylation of alcohols and phenols under heterogeneous conditions
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Silica nanoparticles were synthesized from rice husk ash at room temperature by sonochemical method. The feeding rate of percipiteting agent and time of sonication were investigated. The nanostructure of the synthesized powder was realized by the FE-SEM photomicrograph, FT-IR spectroscopy, XRD and XRF analyses. These analytical observations have revealed that the nano-sized amorphous silica particles are formed and they are spheroidal in shape. The average particle size of the silica powders is found to be around 50 nm. The as-synthesized silica nanoparticles were subsequently modified with chlorosulfonic acid and prepared silica sulfuric acid nanoparticles, which were employed as an efficient catalyst for the acylation of alcohols and phenols with acetic anhydride in excellent yields under solvent-free conditions at room temperature. This reported method is simple, mild, and environmentally viable and catalyst can be simply recovered and reused over 9 times without any significant loss of its catalytic activity.
- Salavati-Niasari, Masoud,Javidi, Jaber
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- A solution study of silica condensation and speciation with relevance to in vitro investigations of biosilicification
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Requiring mild synthesis conditions and possessing a high level of organization and functionality, biosilicas constitute a source of wonder and inspiration for both materials scientists and biologists. In order to understand how such biomaterials are formed and to apply this knowledge to the generation of novel bioinspired materials, a detailed study of the materials, as formed under biologically relevant conditions, is required. In this contribution, data from a detailed study of silica speciation and condensation using a model bioinspired silica precursor (silicon catechol complex, SCC) is presented. The silicon complex quickly and controllably dissociates under neutral pH conditions to well-defined, metastable solutions of orthosilicic acid. The formation of silicomolybdous (blue) complexes was used to monitor and study different stages of silicic acid condensation. In parallel, the rates of silicomolybdic (yellow) complex formation, with mathematical modeling of the species present, was used to follow the solution speciation of polysilicic acids. The results obtained from the two assays correlate well. Monomeric silicic acid, trimeric silicic acids, and different classes of oligomeric polysilicic acids and silica nuclei can be identified and their periods of stability during the early stages of silica condensation measured. For experiments performed at a range of temperatures (273-323 K), an activation energy of 77 kJ·mol-1 was obtained for the formation of trimers. The activation energies for the forward and reverse condensation reactions for addition of monomers to polysilicic acids (273-293 ± 1 K) were 55.0 and 58.6 kJ-mol-1, respectively. For temperatures above 293 K, these energies were reduced to 6.1 and 7.3 kJ·mol-1, indicating a probable change in the prevailing condensation mechanism. The impact of pH on the rates of condensation were measured. There was a direct correlation between the apparent third-order rate constant for trimer formation and pH (4.7-6.9 ± 0.1) while values for the reversible first-order rates reached a plateau at circumneutral pH. These different behaviors are discussed with reference to the generally accepted mechanism for silica condensation in which anionic silicate solution species are central to the condensation process. The results presented in this paper support the use of precursors such as silicon catecholate complexes in the study of biosilicification in vitro. Further detailed experimentation is needed to increase our understanding of specific biomolecule silica interactions that ultimately generate the complex, finely detailed siliceous structures we observe in the world around us.
- Belton, David J.,Deschaume, Olivier,Patwardhan, Siddharth V.,Perry, Carole C.
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- Poly(γ-glutamic acid)/silica hybrids with calcium incorporated in the silica network by use of a calcium alkoxide precursor
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Current materials used for bone regeneration are usually bioactive ceramics or glasses. Although they bond to bone, they are brittle. There is a need for new materials that can combine bioactivity with toughness and controlled biodegradation. Sol-gel hybrids have the potential to do this through their nanoscale interpenetrating networks (IPN) of inorganic and organic components. Poly(γ-glutamic acid) (γ-PGA) was introduced into the sol-gel process to produce a hybrid of γ-PGA and bioactive silica. Calcium is an important element for bone regeneration but calcium sources that are used traditionally in the sol-gel process, such as Ca salts, do not allow Ca incorporation into the silicate network during low-temperature processing. The hypothesis for this study was that using calcium methoxyethoxide (CME) as the Ca source would allow Ca incorporation into the silicate component of the hybrid at room temperature. The produced hybrids would have improved mechanical properties and controlled degradation compared with hybrids of calcium chloride (CaCl2), in which the Ca is not incorporated into the silicate network. Class II hybrids, with covalent bonds between the inorganic and organic species, were synthesised by using organosilane. Calcium incorporation in both the organic and inorganic IPNs of the hybrid was improved when CME was used. This was clearly observed by using FTIR and solid-state NMR spectroscopy, which showed ionic cross-linking of γ-PGA by Ca and a lower degree of condensation of the Si species compared with the hybrids made with CaCl 2 as the Ca source. The ionic cross-linking of γ-PGA by Ca resulted in excellent compressive strength and reduced elastic modulus as measured by compressive testing and nanoindentation, respectively. All hybrids showed bioactivity as hydroxyapatite (HA) was formed after immersion in simulated body fluid (SBF). Organic/inorganic hybrid materials: Calcium methoxyethoxide (CME) was found to be an effective precursor for successfully introducing calcium into organic/inorganic hybrid materials (see figure). The Ca2+ ions were found to successfully cross-link the polymer chains, thereby avoiding a burst release of polymer and Ca2+ in buffered media. CME was found to distribute within the inorganic silica network thanks to the high reactivity of CME with hydroxyl groups.
- Poologasundarampillai, Gowsihan,Yu, Bobo,Tsigkou, Olga,Wang, Daming,Romer, Frederik,Bhakhri, Vineet,Giuliani, Finn,Stevens, Molly M.,McPhail, David S.,Smith, Mark E.,Hanna, John V.,Jones, Julian R.
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- METHOD FOR PRODUCING SILANOLS AND NOVEL SILANOLS
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PROBLEM TO BE SOLVED: To provide a method for efficiently producing silanols useful as functional chemicals, and to provide novel silanols. SOLUTION: There is provided a method for producing silanols including a reaction step of reacting alkoxysilanes having Si-OR bonds (R represents a hydrocarbon group having 1 to 6 carbon atoms) with water or heavy water in the presence of a catalyst, wherein a method for producing silanols having an Si-OR' bond (R' represents a hydrogen atom or a deuterium atom) is characterized in that the catalyst is an inorganic solid acid catalyst having a regular pore structure. There is also provided novel silanols obtained thereby. SELECTED DRAWING: None COPYRIGHT: (C)2021,JPOandINPIT
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Paragraph 0092
(2021/08/13)
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- Silanol Compound, Composition, and Method for Producing Silanol Compound
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The purpose of the present invention is to provide silanol compounds that can be used as raw materials of siloxane compounds and the like, and a composition of the silanol compounds, as well as to provide a production method that makes it possible to produce silanol compounds at excellent yield. A composition comprising 5 mass % to 100 mass % of a silanol compound represented by Formulas (A) to (C) can be prepared by devising to produce silanol compounds under water-free conditions, to produce silanol compounds in a solvent having the effect of suppressing the condensation of silanol compounds, and to perform other such processes, the composition being able to be used as a raw material or the like of siloxane compounds because the silanol compounds can be stably present in the resulting composition.
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Paragraph 0242; 0243
(2017/07/14)
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- Hollow silica nanospheres and methods of making same
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The disclosure provide hollow nanospheres and methods of making and using the same. The methods and compositions of the disclosure are useful for drug delivery and gene transfer.
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Page/Page column 27
(2016/02/03)
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- DENTAL MATERIALS, METHODS OF MAKING AND USING THE SAME, AND ARTICLES FORMED THEREFROM
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Disclosed herein is a dental material composition comprising a polymer matrix material and a biocatalyst that promotes the deposition of a mineral, for example silica or hydroxylapatite. A dental restoration comprising the polymer matrix material and biocatalyst is also claimed. In another embodiment, a method of forming a dental material comprises combining a biocatalyst that promotes the deposition of a mineral and a polymer matrix material to form a biocatalyst-polymer composite.
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Page/Page column 10-11
(2010/11/28)
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- PROCESS FOR PRODUCING ALCOHOL AND/OR KETONE
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The present invention relates to a method for producing an alcohol and/or a ketone from a corresponding alkene(s) in a gas phase in the presence of water vapor by the use of an oxide catalyst. According to the present invention, there is provided a method for producing an alcohol and/or a ketone by bringing a starting material containing an alkene(s), as a gas phase into contact with an oxide catalyst in the presence of water vapor to carry out the reaction, wherein the oxide catalyst satisfies the following requirements: (a) it comprises an oxide(s) of molybdenum and/or tin, and (b) the amount of carbonaceous substances accumulated on the oxide catalyst is controlled to be within a range of 0.1 to 10% by mass, during the reaction.
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Page/Page column 9
(2008/06/13)
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- Silicate Species in Solution. Part 1. Experimental Observations
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Changes in the pH or concentration of sodium silicate solutions produce changes in the degree of polymerisation of the silicate species, and these have been followed by the technique of trimethylsilylation.Provided that the pH remains relatively high, abo
- Glasser, Lesley S.,Lachowski, Eric E.
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p. 393 - 398
(2007/10/02)
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