Showing papers on "Boron oxide published in 2007"

Preparation, characterization and photocatalytic activities of boron- and cerium-codoped TiO2.

Abstract: Boron- and cerium-codoped TiO2 photocatalysts were synthesized using modified sol-gel reaction process and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), particle size distribution (PSD), diffuse reflectance spectra (DRS), and Brunauer-Emmett-Teller (BET). The photocatalytic activities were evaluated by monitoring the degradation of dye Acid Red B (ARB). The results showed that the prepared photocatalysts were mixed oxides mainly consisting of titania, ceria, and boron oxide. The structure of TiO2 could be transformed from amorphous to anatase and then to rutile by increasing calcination temperature; the transformation being accompanied by the growth of particle size without any obvious change in phase structure of CeO2. The XPS of B(1.6)Ce(1.0)-TiO2 prepared at 500 degrees C showed that a few boron atoms were incorporated into titania and ceria lattice, whereas others existed as B2O3. Cerium ions existed in two states, Ce3+ and Ce4+, and the atomic ratio of Ce3+/Ce4+ was 1.86. When boron and cerium were doped, the UV-Vis adsorption band wavelength showed an obvious shift toward the visible range (< or =526 nm). As the atomic ratio of Ce/Ti increased to 1.0, the absorbance edge wavelength increased to 481 nm. The absorbance edge wavelength decreased for higher cerium doping levels (Ce/Ti = 2.0). The particles size ranged from 122 to 255 nm with a domain at 168 nm (39.4%). The degradation of ARB dye indicated that the photocatalytic activities of boron- and cerium-codoped TiO2 were much higher than those of P25 (a standard TiO2 powder). The activities increased as the boron doping increased, whereas decreased when the Ce/Ti atomic ratio was greater than 0.5. The optimum atomic ratio of B/Ti and Ce/Ti was 1.6 and 0.5, respectively.

Structure and stability of small boron and boron oxide clusters.

Abstract: To rationally design and explore a potential energy source based on the highly exothermic oxidation of boron, density functional theory (DFT) was used to characterize small boron clusters with 0−3 oxygen atoms and a total of up to ten atoms. The structures, vibrational frequencies, and stabilities were calculated for each of these clusters. A quantum molecular dynamics procedure was used to locate the global minimum for each species, which proved to be crucial given the unintuitive structure of many of the most stable isomers. Additionally, due to the plane-wave, periodic DFT code used in this study a straightforward comparison of these clusters to the bulk boron and B2O3 structures was possible despite the great structural and energetic differences between the two forms. Through evaluation of previous computational and experimental work, the relevant low-energy structures of all but one of the pure boron clusters can be assigned with great certainty. Nearly all of the boron oxide clusters are described h...

Convection Patterns in Liquid Oxide Films on ZrB2–SiC Composites Oxidized at a High Temperature

Abstract: During the high-temperature oxidation of ZrB2–SiC composites, liquid boron oxide (B2O3) is formed at the zirconium diboride–zirconium oxide interface and transported through the overlying layer of silica liquid by convection, forming distinct convection cells arranged like the petals of a flower. The convection cells are localized by a viscous fingering phenomenon, as the fluid B2O3 rich liquid solution rises through the viscous silica layer. The upwelling B2O3 rich liquid contains dissolved zirconium dioxide, which deposits in the center of the flower-like structure as the B2O3 evaporates. The driving force for the B2O3 liquid flow is the volume increase upon oxidation of ZrB2. Convective transport of B2O3 liquids suggests a novel mechanism for the high-temperature oxidation of these materials.

IR spectroscopic study of the phase composition of boric acid as a component of glass batch

Abstract: Analytically pure reagent “boric acid,” used in batches for preparing glass, was investigated by IR spectroscopy. It was found that the reagent consisted of three components — meta-and orthoboric acids and glassy boron oxide, water was present in two forms — molecular and in the form of OH groups, and impurities of organic substances and carbon dioxide were not very probable. The orthoboric acid bands at 1450, 1195, 883, 815, and 548 cm−1 were found for the first time and were not indicated in the previously published reference spectrum.

On the chemical bonding of gold in auro-boron oxide clusters AunBO- (n = 1-3).

Abstract: During experiment on Au−B alloy clusters, an auro−boron oxide cluster Au2BO- was observed to be an intense peak dominating the Au−B mass spectra, along with weaker signals for AuBO- and Au3BO-. Well-resolved photoelectron spectra have been obtained for the three new oxide clusters, which exhibit an odd−even effect in electron affinities. Au2BO- is shown to be a closed shell molecule with a very high electron detachment energy, whereas AuBO and Au3BO neutrals are shown to be closed shell species with large HOMO-LUMO gaps, resulting in relatively low electron affinities. Density functional calculations were performed for both AunBO- (n = 1−3) and the corresponding HnBO- species to evaluate the analogy between bonding of gold and hydrogen in these clusters. The combination of experiment and theory allowed us to establish the structures and chemical bonding of these tertiary clusters. We find that the first gold atom does mimic hydrogen and interacts with the BO unit to produce a linear AuBO structure. This u...

Preparation and Characterization of PVA/Boron Polymer Produced by an Electrospinning Technique.

Abstract: In this study, poly(vinyl alcohol) we re cross-linked with boron in varying concentrations and blend fibers were obtained with diameters ranging from 0.3 μ to 4.0 μm with the use of electrospinni ng process. The resulting product was characterized by SEM, DSC, and FT-IR techniques. There is no beading tendency in either boron doped or undoped fibers. When the amount of boric acid in PVA solutions was increased the conductivity of the polymer decreased. The data indicated the existence of boron oxide in the polymeric structure and the formation of B-O-C bond. SEM micrographs reveal that higher viscosity favors the formation of thicker fibers. Boron addition seems to disturb the easy detachment of the fibers from the tip of the Taylor Cone

Glass yarns capable of reinforcing organic and/or inorganic materials

Abstract: The invention relates to a glass yarn having a chemical composition which is essentially free of boron oxide and includes the following constituents within the limits defined below and expressed in percentage by weight, namely: 55 to 65 SiO2, 9 to 16 Al2O3, 15 to 26 CaO, 1 to 5 MgO, 0.5 to 5 BaO+SrO, 0 to 2 Na2O + K2O + Li2O, 0 to 1 TiO2, 0 to 2 ZnO, and 0 to 2 ZrO2. The invention also relates to composites containing said yarns.

Ceramic with improved high temperature electrical properties for use as a spark plug insulator

Abstract: An insulator including alumina in an amount between about 90 and about 99% by weight and an oxide mixture or glass mixture including Boron Oxide, Phosphorus Oxide, or both Boron and Phosphorus Oxide.

Microstructural Aspects of the Hot-Pressed Hexagonal Boron Nitride Ceramics with Limited Content of Boron Oxide

Abstract: Hexagonal boron nitride (h-BN) based ceramics have been fabricated by hot-pressing in a nitrogen atmosphere at 1900°C for 60 min. under a pressure of 50 MPa with B2O3 as sintering additive. The phase composition was confirmed by XRD. The microstructural properties of h-BN powders and hot-pressed surfaces were evaluated by SEM-EDS analysis. The formation of the secondary phase was also investigated with particular interest on grain boundaries. The sintered densities were also determined by Archimedes’ method. The maximum relative density was obtained to be about 92 %. The effect of the existence of boron oxide on the boron nitride grain growth behaviour was discussed on the basis of microstructural features.

Multilayer Quasi-Aligned Nanowire Webs of Aluminum Borate

Abstract: Multilayer nanowire webs of aluminum borate (Al18B4O33) have been synthesized by a solid-state reaction of boron, boron oxide, and aluminum oxide at high temperature without using any template or substrate. Alumina powder on a micron scale provides an in-situ reaction container resulting in self-oriented growth of the aluminum borate nanowires. The orientation could be maintained by a quenching treatment. The addition of boron should be responsible for the generation of the web morphology. Without any further purification, a large amount of nanowire webs with high purity was obtained. Further experiments were carried out to investigate the morphological dependence on the reactant compositions. The possible growth mechanism for the nanowebs was detailed based on extensive analysis and examination.

Method of converting PCA to sapphire and converted article

Abstract: Polycrystalline alumina (PCA) that has been doped with magnesium oxide is converted to sapphire by additionally doping the PCA with boron oxide and sintering to induce abnormal grain growth. The boron oxide may be added to an already formed green PCA ceramic shape by applying an aqueous boric acid solution to the green ceramic and heating the green ceramic in air to convert the boric acid to boron oxide.

Aluminium-alloy iron-removing solvent

Abstract: An aluminum alloy deironing flux consists of sodium chloride 20-40wt%, potassium chloride 20-40wt%, cryolite 1-10wt%, sodium fluoride 0-10wt%, boron oxide and/or sodium borate 9-30wt%. It's simple, convenient and cheap and has better effect.

Synthesis and characterization of nanocrystalline hexagonal boron carbo-nitride under high temperature and high pressure

Abstract: A study of the synthesis of hexagonal boron carbo-nitride (h-BCN) compounds via a two-step high-temperature and high-pressure (HTHP) technique using melamine (C3N6H6) and boron oxide (B2O3) as raw materials is presented. An amorphous BCN precursor was prepared at 1000 K under vacuum in a resistance furnace and then single-phase h-BCN nanocrystalline was synthesized at 1600 K and 5.1 GPa in a multi-anvil apparatus. X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated that the final products were pure h-BCN crystals with the lattice constants a = 0.2510 nm and c = 0.6690 nm. The average grain size was about 150 nm. X-ray photoelectron spectroscopy (XPS) results confirmed the occurrence of bonding between C–C, C–N, C–B and N–B atoms. Raman scattering analysis suggested that there were three strong Raman bands centered at 1359, 1596 and 1617 cm−1, respectively. The band at 1617 cm−1 was considered to be consistent with the characteristic Raman peak of h-BCN.

CZT X-ray detectors obtained by the boron encapsulated vertical Bridgman method

Abstract: Recently, some of the authors showed that it is possible to grow CZT crystals by the boron oxide encapsulated vertical Bridgman method. The most important feature of the technique is that the crystal, during the growth, is fully encapsulated by a thin layer of liquid boron oxide, so that the crystal-crucible contact is prevented. The stress of the crucible to the crystal is strongly reduced also during the cooling, because the boron oxide layer is molten down to about 500°C. A number of detectors have been prepared out of these crystals. The transport properties (μτ product) have been studied by photoconductivity measurements as well as by determining the response to hard X-ray irradiation. The transport properties have been studied as a function of the indium content and of the position of the wafer which the detector was cut out.

Preparation method of quasi one-dimensional boron nitride nanostructure

Abstract: The invention discloses a controlled preparing method of pseudo one-dimensional boron nitride nanometer structure through adjusting preparation parameter to control diverse pseudo one-dimensional boron nitride nanometer structure, which comprises the following steps: choosing bis nickel, bis ferrum, bio cobalt or the mixture as suspended activator forerunner body; volatilizing in the low temperature region; carrying through gas-carrier to high-temperature region; disintegrating to metallic catalyst; accelerating B2O2 vapour generated through mixing boron powder and boron oxide to react with ammonia gas; generating the product; getting boron nitride nanometer thread and bamboo joint state boron nitride nanometer pipe with diverse diameter and outlook through controlling component, time, temperature of the activator. The structure of the boron nitride nanometer thread and pipe possesses essential difference, which the front (0002) face grow vertically and the back (0002) face parallel-grows.

Reactions of boron carbide and other boron compounds with carbon dioxide

Abstract: In the reaction of boron-containing materials with carbon dioxide, most of them oxidise quite rapidly to form boron oxide, which itself reacts to give a volatile boron compound. The major part of the work concerns boron carbide, and the effects of temperature, pressure and additions of water vapour and carbon monoxide have been considered. Other materials investigated are ZrB2, TiB2, CrB2, BN, BSi9 and elemental boron.

Hexagonal nanometer boron nitride microsphere and its synthesis process and application

Abstract: The present invention is hexagonal nanometer boron nitride microsphere and its synthesis process and application. The hexagonal nanometer boron nitride microsphere is laminated structure of 30-150 nm diameter and with 30-50 nm diameter fraction not less than 60 %. The preparation process includes the esterification between boron oxide and monobasic alcohol to produce the mixture of trihydroxy boric acid ester and boric acid, carrying the mixture into nitriding furnace to react with excessive ammonia at high temperature, and washing the reaction product with methanol to eliminate boron oxide to obtain hexagonal nanometer boron nitride microsphere. The preparation process is simple, reliable, low in cost and suitable for large scale production, and the synthesized hexagonal nanometer boron nitride microsphere has high purity and is used as lubricant.

Method of making glass including use of boron oxide for reducing glass refiting time

Abstract: This invention relates to a method of making soda-lime-silica based glass. In certain example embodiments, boron oxide (e.g., B2O3) is used in the glass for reducing the refining time (or increasing the refining rate) thereof. The boron oxide may be introduced into the glass batch or melt in the form of boric acid, sodium tetraborate pentahydrate, sodium tetraborate decahydrate, sodium pentahydrate, or in any other suitable form. In certain example embodiments, the resulting soda-lime-silica based glass ends up including from about 0.1 to 3%, more preferably from about 0.1 to 2.5%, and most preferably from about 0.5 to 2.0% (e.g., about 1%), boron oxide. It has been found that the use of boron oxide, and/or the form in which the same is introduced into the glass, is advantageous in that it permits the refining time of the glass to be substantially reduced.

Influence of boron on the point defect equilibrium in highly n-doped gallium arsenide single crystals

Abstract: High n-type conductivity of melt-grown gallium arsenide single crystals is usually achieved by doping with tellurium or silicon. The lower carrier concentration and Hall mobility in silicon-doped crystals is attributed to the formation of acceptor defects, in particular Si As - , the isolated gallium vacancy V Ga 3 - and the ( Si Ga – V Ga ) 2 - complex. We show that the contamination of the crystals with boron, which is unavoidable in growing techniques using a boron oxide encapsulant, is decisive for the degree of compensation. In highly n-doped gallium arsenide crystals boron is not only incorporated as the isoelectronic defect B Ga 0 . Additionally, high concentrations of B As 2 - and the negatively charged B As -donor complex are formed. These acceptors can dominate the equilibrium of point defects depending on the concentration ratio of the n-dopant and boron.

Cosmetic compositions containing pearlescent pigments

Abstract: The present invention is directed to a cosmetic composition comprising an effect pigment based on a glass flake as a substrate with a coating, said coating comprising at least one layer of at least one high refractive material, said material having a refractive index of at least 1.8, and/or a semitransparent metal coating wherein said glass flakes comprising the following composition: 65 - 75 wt.-% silicon oxide, preferably SiO 2 2 - 9 wt.-% aluminium oxide, preferably Al 2 O 3 0.0 - 5 wt.-% calcium oxide, preferably CaO 5 - 12 wt.-% sodium oxide, preferably Na 2 O 8 -15 wt.% boron oxide, preferably B 2 O 3 0.1 - 5 wt.-% titanium oxide, preferably TiO 2 0.0 - 5 wt.-% zirconium oxide, preferably ZrO 2 based on the weight of said glass flakes. The invention is also directed to the use of the cosmetic composition.

Alumina support, method for making alumina support and method for making dehydrogenation catalyst of c3-c5 paraffin hydrocarbons on this support

Abstract: FIELD: chemistry ^ SUBSTANCE: group of inventions refers to supports (alumina support), to methods for making supports of catalysts activated in aerated layer and chrome-alumina catalyst for dehydrogenation of C3-C5 paraffin hydrocarbons to related olefines being monomers used for manufacturing of chemical rubbers, polymers, blending fuels There is disclosed alumina support of boehmite morphology, specific surface 80 to 250 m2/g, pore size at least 02 cm3/g, microcrystallite size by coherent scattering region 500 to 3000 A It contains interlayer water in amount corresponding to mole ratio aluminium oxide to water 08 to 12 There is described method for making support by high-temperature processing of hydrargillite in inert gas and/or ammonia, and/or carbon oxide medium at temperature 100 to 300°C and pressure 01 to 150 kgs/cm2 and following drying Besides, there is disclosed method for making dehydrogenation catalyst of C3-C5 paraffin hydrocarbons by impregnation of support produced as described above with precursor solutions of chrome oxide, potassium oxide and activating agent representing, at least, one oxide chosen from the group: copper oxide, zinc oxide, manganous oxide, tin oxide, boron oxide, zirconium oxide, there after dried and baked at temperature 600 to 900°C ^ EFFECT: production of alumina support, development of production methods and methods for making dehydrogenation catalyst on this support of high mechanical strength, low abrasiveness and high activity and selectivity in dehydrogenation of propane, isobutane and isopentane ^ 7 cl, 2 tbl, 10 ex

Solder glass contains specified percentage ranges of silica, boron oxide, zinc oxide, bismuth oxide and aluminum oxide, ratio of silica to aluminum oxide being below specified value

Abstract: Solder glass contains (wt%): silica 1 - 2; boron oxide 5 - 10; zinc oxide 4.5 - 10; bismuth oxide 79 - 88; aluminum oxide 0.6 - 2. The ratio of silica to aluminum oxide is less than 2. It has a coefficient of thermal expansion below 11.5 x 10 -> 6>/K and transformation temperature below 380[deg] C. An independent claim is included for use of the solder glass in which up to 20 wt% of filler is added to the glass to modify its coefficient of expansion.

Oxygenate conversion using boron-containing molecular sieve cha

Abstract: A process for the production of light olefins from a feedstock comprising an oxygenate or mixture of oxygenates, the process comprising reacting the feedstock at effective conditions over a catalyst comprising boron-containing molecular sieve having the CHA crystal structure and comprising (1) silicon oxide and (2) boron oxide or a combination of boron oxide and aluminum oxide, iron oxide, titanium oxide, gallium oxide and mixtures thereof; and wherein the mole ratio of silicon oxide to boron oxide in said boron-containing molecular sieve is between 15 and 125. A method for production of light olefins, comprising selecting the catalyst and reacting a feedstock comprising an oxygenate or mixture of oxygenates, at effective conditions, over the catalyst. Also, a method for production of light olefins, comprising selecting the catalyst, selecting the oxygenate feedstock, and reacting the feedstock at effective conditions over the catalyst.

Reduction of oxides of nitrogen in a gas stream using boron-containing molecular sieve cha

Abstract: A process for reduction of oxides of nitrogen contained in a gas stream comprising contacting the gas stream with a boron-containing molecular sieve, the boron-containing molecular sieve having the CHA crystal structure and comprising (1) silicon oxide and (2) boron oxide or a combination of boron oxide and aluminum oxide, iron oxide, titanium oxide, gallium oxide and mixtures thereof; and wherein the mole-ratio of silicon oxide to boron oxide in said boron-containing molecular sieve is between 15 and 125. A method for reduction of oxides of nitrogen, comprising a) selecting the boron-containing molecular sieve; and b) contacting a gas stream with the molecular sieve. A method for reduction of oxides, comprising: a) selecting the boron-containing molecular sieve containing a metal or metal ions capable of catalyzing the reduction of the oxides of nitrogen; and b) contacting an exhaust stream of an internal combustion engine with the molecular sieve.