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Showing papers on "Mixed oxide published in 1991"


Journal ArticleDOI
TL;DR: In this article, the properties of calcined and sulfided CoO/SiO{sub 2} catalysts were analyzed using XPS, TPR, TEM, DRS-VIS, and XRD techniques.
Abstract: Physicochemical characterization of calcined and sulfided CoO/SiO{sub 2} catalysts were carried out to reveal the interaction modes between cobalt and SiO{sub 2} using XPS, TPR, TEM, DRS-VIS, and XRD techniques. The CoO/SiO{sub 2} catalysts were prepared by an impregnation method using cobalt acetate as well as cobalt nitrate and by an ion-exchange technique. It was found that several kinds of cobalt species are formed on CoO/SiO{sub 2}. These species are assigned to Co{sub 3}O{sub 4}, Co-Si-O mixed oxide, surface Co{sup 3+} species, surface silicate, surface Co{sup 2+} species in the order of the TPR reduction temperature. Their proportions strongly depended on the starting salt, cobalt content, and preparation method. Cobalt acetate was found to provide highly dispersed CoO/SiO{sub 2} catalysts with a uniform distribution of cobalt species throughout the catalyst particles as compared to conventionally employed cobalt nitrate. The proportion of Co{sup 3+} greatly decreases when cobalt acetate was used instead of cobalt nitrate. All the cobalt species interacting with SiO{sub 2} were found to be sulfided at 673 K.

163 citations


Journal ArticleDOI
TL;DR: In this article, the performance of mixed oxide capacitors was investigated for detection at the concentration range of hundreds of ppm, and at a percentage level, respectively, and the results showed that the capacitance change of on exposure to was small, it was greatly enhanced by the combination with.
Abstract: Oxide capacitors consisting of and an oxide are studied as a sensor for detection. Although the capacitance change of on exposure to was small, it was greatly enhanced by the combination with . Sensitivity to and optimum operating temperature were strongly dependent on the oxide combined with . The element which contains basic oxides such as and , is highly sensitive to , but the operating temperature exceeded 1073 K. Among the elements investigated in this study, exhibited the highest sensitivity to . selectively responded to , and this element could distinguish the concentrations up to 6%. On the other hand, the capacitance of decreased linearly with increasing concentration up to 20%. Mixed oxide capacitors of and , therefore, are suitable for sensing at the concentration range of hundreds of ppm, and at a percentage level, respectively.

163 citations


Journal ArticleDOI
TL;DR: In this paper, a range of mixed Mo/V/Nb oxide catalysts were investigated for the oxidative dehydrogenation of ethane, and a correlation was observed between the ease of reduction of the catalyst and the activity and selectivity, with the most easily reduced catalyst being the most active and selective for the formation of ethene.

114 citations


Journal ArticleDOI
TL;DR: In this article, the capacitances of mixed oxide CuO-SrTiO 3, CaTiO3, and ZnO-ZnO were investigated for CO 2 sensing.
Abstract: Characteristics for CO 2 sensing of a CuO-based oxide capacitor were studied. The capacitances of CuO mixed with BaSnO 3 , CaTiO 3 , and ZnO are dependent on the CO 2 concentration, similar to CuO-BaTiO 2 . In particular, the mixed oxide CuO-SrTiO 3 , is more sensitive to CO 2 than CuO-BaTiO 3 , but requires a rather long time to rather long time to recorver

97 citations


Journal ArticleDOI
TL;DR: In this paper, the influence of synthesis parameters on the structural properties of mixed oxides derived from silicon tetraethoxide and titanium tetra-isopropoxide precursors has been studied by 29 Si NMR speectroscopy.
Abstract: The influence of synthesis parameters on the structural properties of mixed oxides derived from silicon tetraethoxide and titanium tetra-isopropoxide precursors has been studied by 29 Si NMR speectroscopy. A first set of gels, prepared by complete hydrolysis of the individual precursors and subsequent mixing of the hydrosols, is characterized by comparatively narrow lines for the Q 2 , Q 3 , and Q 4 silica sites. Both the chemical shift values and the time constants of 1 H 29 Si magnetization transfer are similar to those found in pure silica gels. This indicates that these oxides consist of domains of the individual components. A different appearance of the CP/MAS spectra is noted for the second set of gels, which is prepared by addition of the titanium alkoxide component at a stage where the silicon alkoxide hydrolysis has only proceeded to about 50%, on average. The spectra of these samples are characterized by broad lines for the three types of sites. Larger contributions observed for Q 2 and Q 3 sites in these samples are attributed to the presence of SiOTi bridges. The influence of preparation parameters such as hydrolysis pH, drying temperature, and pore ripening treatment by redispersion in base, is studied by monitoring the spectral and dynamic parameters derived from the CP/MAS spectra.

60 citations


Journal ArticleDOI
E. N. Balko1, P. H. Nguyen1
TL;DR: In this paper, mixed oxide coatings of tin and iridium oxide on titanium substrates have been studied over the composition range of 5 to 100 mol % iridium oxides.
Abstract: Mixed oxide coatings of tin and iridium oxide on titanium substrates have been studied over the composition range of 5 to 100 mol % iridium oxide. While stannic oxide behaves as a simple diluent for the electrocatalytically active precious metal oxide, substantial replacement of iridium by tin may be made with little degradation of coating performance in oxygen evolution.

56 citations


Journal ArticleDOI
TL;DR: In this article, the structure of MoO3/Al2O3-SiO2 mixed oxide catalysts was studied by XRD, IR and UV-Vis spectroscopy.

48 citations


Patent
11 Dec 1991
TL;DR: In this article, the authors described a catalyst for purification of exhaust gases containing nitrogen oxides wherein oxygen is co-existent in excess of a stoichiometric amount, characterized in that a coprecipitated mixed oxide of copper and tin is loaded on a carrier composed of at least one type selected from the group consisting of crystalline aluminosilicate, aluminogallosilicates and gallos-ilicate.
Abstract: of the Disclosure There is described a catalyst for purification of exhaust gases containing nitrogen oxides wherein oxygen is co-existent in excess of a stoichiometric amount, characterized in that a coprecipitated mixed oxide of copper and tin is loaded on a carrier composed of at least one type selected from the group consisting of crystalline aluminosilicate, aluminogallosilicate and gallosilicate, or the coprecipitated mixed oxide of copper and tin and further at least one noble metal selected from the group consisting of platinum, palla-dium, rhodium, iridium, ruthenium, silver and gold are co-loaded thereon. This invention provides a lean NOx purification catalyst having high NOx purification performance and markedly increased durability over a wide temperature range.

34 citations


Patent
Rodney L. Mieville1
20 Dec 1991
TL;DR: In this paper, a membrane of an oxidative conversion contact material of a mixed oxide of aluminum and at least one multivalent activator metal with the membrane permitting selective conveyance of a form of oxygen therethrough, as well as methods for the oxidative conversion of a gaseous hydrocarbon reactant using such membranes are provided.
Abstract: A membrane of an oxidative conversion contact material of a mixed oxide of aluminum and at least one multivalent activator metal with the membrane permitting selective conveyance of a form of oxygen therethrough, as well as methods for the oxidative conversion of a gaseous hydrocarbon reactant using such membranes are provided.

26 citations


Journal ArticleDOI
TL;DR: The corrosion behavior of Mo-Al, Cr-Al and Cr-Mo-Al surface alloys produced by ion implantation and ion beam mixing was examined in de-aerated, 01 M NaCl as mentioned in this paper.

26 citations


Journal ArticleDOI
TL;DR: In this article, the structural and surface properties of 12molybdophosphoric (abbreviated as PM012) and 10molybdo-2-vanadophosphorusoric (ABbreviating as PM010V2) acids as they are decomposed at high temperatures have been studied by IR, XRD, XPS, and TPD experiments.
Abstract: Changes in the structural and surface properties of 12-molybdophosphoric (abbreviated as PM012) and 10-molybdo-2-vanadophosphoric (abbreviated as PM010V2) acids as they are decomposed at high temperatures have been studied by IR, XRD, XPS, and TPD experiments. PMo12 simply decomposes into MoO3 by heat-treatment at 580C, but PMo10V2 yields a mixed oxide whose properties are different from those of either MoO3 or V2O3. After the thermal decomposition, PMo12 loses the initial acidic and rt’dox properties almosl completely but PMo10V2 retains some extent of the redox capability that is larger than that of MoO3 and V3O5. The redox capability of the mixed oxide obtained by PMo10V2 decomposition is correlated with its catalytic activity in oxidation processes.

Journal ArticleDOI
TL;DR: In this paper, a theoretical treatment of the E vs. x curve was proposed to determine the repulsive interaction between the inserted species as insertion occurs and the influence of the electronic term on the potential.
Abstract: The formation of hydrogen tungsten bronzes H{sub 1}WO{sub 3}, has been thermodynamically studied. The variation of the chemical potential of the inserted species in these thin films of oxide at ambient temperature has been measured using an electrochemical method. The authors point out in this paper that it is necessary to consider insertion of proton-electron pairs into the oxide instead of considering the formation of a mixed oxide. A theoretical treatment of the E vs. x curve allows the authors to determine the repulsive interaction between the inserted species as insertion occurs and the influence of the electronic term on the potential.

Journal ArticleDOI
TL;DR: In this article, a mixture of mixed oxide catalysts for propene oxidation and ammoxidation has been prepared and their reactivity has been established by both temperature programmed desorption (TPD) after the adsorption of propene and reactor rate measurements.

Journal ArticleDOI
TL;DR: In this article, a mixture of zincian malachite and aurichalcite was used to detect tetrahedral copper in the tenorite lattice of the mixture of CuO and ZnO.


Patent
29 Aug 1991
TL;DR: In this paper, the optical thickness of the undercoating is selected for the reduction of reflected visible light interference effects due to the tin oxide overcoat, and the intermediate product comprises a glass substrate bearing a pyrolytically formed oxidised metal coating which comprises a layer in which said metal comprises aluminium with a minor proportion of vanadium and which has a refractive index of at least 1.67.
Abstract: Pyrolytic tin oxide coatings formed on soda-lime glass, particularly those formed from a tin chloride precursor, suffer from haze at the glass/coating interface due to the migration of sodium ions from the glass into the coating. Tin oxide coatings also exhibit iridescence in certain thicknesses. In order to reduce iridescence and to provide a barrier against the incorporation of sodium into the tin oxide layer, the glass is first provided with an undercoating layer of oxidised metal which contains aluminium with a minor proportion of vanadium. The optical thickness of the undercoat is selected for the reduction of reflected visible light interference effects due to the tin oxide overcoat. An intermediate product comprises a glass substrate bearing a pyrolytically formed oxidised metal coating which comprises a layer in which said metal comprises aluminium with a minor proportion of vanadium and which has a refractive index of at least 1.67. The undercoating is prepared using a precursor solution comprising aluminium acetyl acetonate and vanadium acetyl acetonate, which may contain glacial acetic acid as solvent. The substrate is preferably formed of float glass. The tin oxide coating may have a thickness of 250-700nm and may be prepared by pyrolysis of an aqueous solution of stannous chloride containing ammonium bifluoride for the provision of fluoride doping ions.

Journal ArticleDOI
TL;DR: Injection and ejection of D + and Li + ions in thermally prepared Ir-Ti mixed oxide films have been followed by means of nuclear reaction analysis Tests were carried out after the application of a potential that allows the maximum cation uptake and under conditions that correspond to the minimum cation consumption as mentioned in this paper.

Journal ArticleDOI
TL;DR: An alternative synthetic approach was attempted for the fabrication of the Bi-Ca-Sr-Cu oxide superconductor as mentioned in this paper, where a mixed oxide/carbonate precursors was first formed, and the resulting powder was subsequently reacted with Bi2O3.
Abstract: An alternative synthetic approach was attempted for the fabrication of the Bi–Ca–Sr–Cu oxide superconductor. In this approach a mixed Sr–Ca–Cu oxide powder was first formed, and the resulting powder was subsequently reacted with Bi2O3. With this reaction scheme, problems associated with the low reactivity of CuO and SrCO3 can be partially removed by converting the mixed oxide/carbonate precursors to the reactive Sr–Ca–Cu compound. An enhanced rate of formation of the high-Tc (110 K) phase was observed in the two-step reaction, and this was explained in terms of the low activation free energy path for the formation of the high-Tc phase, which increased the decomposition rate of the remnant CuO. Under the condition of rapid heating, the formation of the high-Tc phase in the one-step reaction was expedited by the Cu-rich liquid phase. However, the liquid phase caused the formation of an insulating layer between the superconducting grains in spite of its catalytic activity in the high-Tc phase formation.

Journal ArticleDOI
TL;DR: In this article, the solid compounds KLnU(C 2 O 4 ) 4 ·8H 2 O, where Ln = La, Ce, Pr, Nd and Tb have been synthesised and characterised by chemical, X-ray diffraction, infrared and thermogravimetric methods.

Journal ArticleDOI
TL;DR: In this article, the relative ion and neutral partial pressures in the plasma above the sputtered region of a solid appear to be controlled by ion-molecule equilibria.
Abstract: In this work, first-row transition-metal oxides and several series of mixed first-row transition-metal oxides have been examined under dynamic SIMS conditions.For studies on the mixed oxides, relative sensitivity factors have been derived for a given type of mixed oxide from positive SIMS spectra, which can be used to quantitatively analyse other mixed oxides of that type.In addition, an investigation was made to determine the factors which control relative ion intensities observed in positive SIMS spectra recorded for mixed transition-metal oxides. Attempts to correlate experimental relative ion intensities with solid-state properties such as bulk composition, lattice parameter or metal–oxygen bond strength in the solid met with limited success. However, evidence was obtained for the observed relative ion intensities being controlled by the relative stability of the ions produced in the vapour phase above the solid. Relative ion and neutral partial pressures in the plasma above the sputtered region of a solid appear to be controlled by ion–molecule equilibria.

Journal ArticleDOI
TL;DR: In this paper, a graphite-based Pt electrode modified with In + Pb mixed oxide exhibited a considerable level of electrocatalytic activity towards methanol electrooxidation, showing a very low zero-current potential, i.e. 95 mV.

Patent
22 Jul 1991
TL;DR: In this paper, the method consists in producing zinc oxide by precipitation of a precursor comprised of a mixed monophase zinc carbonate and of dopes wherein atoms of bismuth and other dopes are substituted for zinc atoms.
Abstract: The method consists in producing zinc oxide by precipitation of a precursor comprised of a mixed monophase zinc carbonate and of dopes wherein atoms of bismuth and other dopes are substituted for zinc atoms; the mixed carbonate is then subjected to decomposition heat treatment resulting in a mixed oxide of zinc, bismuth and other dopes. The method can be used to produce powders of doped zinc oxide which are homogeneous with respect to all elements present and having a controllable morphology.

Patent
21 Nov 1991
TL;DR: In this paper, the authors described a process for the preparation of beta-isophorone from alphaisophoric acid, which was then converted to betaisophore in the gas phase in the presence of a heterogeneous catalyst.
Abstract: The invention relates to a process for the preparation of beta-isophorone from alpha-isophorone, alpha-isophorone being converted to beta-isophorone in the gas phase in the presence of a heterogeneous catalyst The heterogeneous catalyst used is in particular an oxide or mixed oxide of the elements Mg, Al, Si and Ni

Journal ArticleDOI
TL;DR: In this article, results of oxidation experiments on Fe•Nd alloys are presented, and two mechanisms of oxidation are observed, one with precipitation of a fine Nd2O3 dispersion in the alloy matrix, with simultaneous displacement of the phase compositions to Fe•rich values.
Abstract: In this work results of oxidation experiments on Fe‐Nd alloys are presented. Samples were prepared by melting the metals and Nd oxide, and by melting the metals, stabilizing the alloys through long heat treatments, and oxidizing them in low‐oxygen partial pressures. Two mechanisms of oxidation are observed, one with precipitation of a fine Nd2O3 dispersion in the alloy matrix, with simultaneous displacement of the phase compositions to Fe‐rich values. Eventually, pure Fe striae are formed. The second mechanism corresponds to the direct formation of a mixed oxide and Nd2O3.

Patent
26 Sep 1991
TL;DR: In this article, the authors proposed a method to obtain a highly reliable sintered compact having high strength and toughness by firing a mixture of Si3N4 and a mixed oxide produced by adding silica to a rare-earth metal oxide-alumina-based oxide.
Abstract: PURPOSE:To obtain a highly reliable sintered compact having high strength and toughness by firing a mixture of Si3N4 and a mixed oxide produced by adding silica to a rare-earth metal oxide-alumina-based oxide. CONSTITUTION:The objective silicon carbide-mixed oxide sintered compact free from detects such as void and pore can be produced by mixing 5-95wt.% of a mixed oxide consisting of 95-5wt.% of rare-earth metal oxide, 4.9-94.9wt,% of alumina and 0.1-10wt.% of silica and 90-5wt.% of Si3N4 powder, whisker or their mixture, forming the obtained mixture, heating the formed product in a non-oxidizing atmosphere at a heating rate of 5-2000 deg.C /min and maintaining at 1500-1900 deg.C for 0.1-600min. The above mixed oxide is e.g. composed of 99.9-90wt.% of Ln4Al2O9 or LaAlO3 (Ln is rare-earth elements or their mixture) and 0.1-10wt.% of silica.

Patent
06 Jun 1991
TL;DR: The use of the mixed oxide according to the invention as a catalytic material was discussed in this article, where an aluminosilicate carrier was used for a mixture of 12-13% Al₂O, 66-67% SiO, 2-3% CaO, 1-2% MgO, 0.5-1.5% NaO and 13-15% HCO.
Abstract: A mixed oxide approximately corresponding to the general formula: R p (M q Z y )O x , wherein R is at least one of La, Ce, Pr, Nd; M is at least one of Ca, Sr, Ba, Zr; Z is at least one of Zn, Co, Ni, Cu; p is 1-2; q is 0-0.4; y is 0.6-1.0 and x is 3-4, the values of p, q, y, and x, respectively, being approximate. The use of the mixed oxide according to the invention as a catalytic material. An aluminosilicate carrier for a catalytic material comprising 12-13% Al₂O₃, 66-67% SiO₂, 2-3% CaO, 1-2% MgO, 2-3% K₂O, 0.5-1.5% Na₂O and 13-15% H₂O.

Journal ArticleDOI
TL;DR: In this paper, a photoelectrode system for hydrogen production through photoassisted electrolysis of water was described, where mixed oxide electrodes have been synthesized by solid state sintering.

Journal ArticleDOI
TL;DR: In this paper, the constituents of the Y4Al2O9 phase were determined by quantitative phase analysis with the method of inner standards, and corresponding gauge curves for the conditions of the temperatures of sintering were drawn.
Abstract: For the preparation and transformation sequence in the system Y4O3–Al2O3 the sintering of homogeneously mixed oxide powders was chosen. The constituents of the Y4Al2O9 phase were determined by quantitative phase analysis with the method of inner standards. Corresponding gauge curves for the conditions of the temperatures of sintering were drawn. At low temperatures appears as first in the whole molar range the (2:1) phase, i.e. Y4Al2O9. With increasing temperature and sintering time the yield of this mixed crystal phase depends on the concentration of the oxide components in the powder mixture of the start materials. In flux mixtures of the components PbO, PbF2, and B2O3 and despite suitable nucleation it was not possible to obtain this compound. In the melt the compound Y4Al2O9 was prepared frequently in near molar conditions. Also a glass was prepared with (2:1) stoichiometry. Single crystals were identified by X-rays.

Journal ArticleDOI
TL;DR: In this paper, the authors used Raman spectroscopy to obtain information on the structure of vanadia species in amorphous SiO2 matrix, in which the vanadium species are molecularly dispersed in an amorphou2 matrix and the three-dimensional linked network exhibits a high stability against thermal aggregation of the vanadia particles.
Abstract: The preparation of V2O5/SiO2 mixed gels by the sol-gel process provides a novel class of active catalysts for the selective catalytic reduction (SCR) of nitric oxide [1]. Raman spectroscopy is used to obtain information on the structure of these systems, in which the vanadia species are molecularly dispersed in an amorphous SiO2 matrix. This three-dimensionally linked network exhibits a high stability against thermal aggregation of the vanadia particles. At high vanadia contents small crystalline domains of V6O13 and V3O7 are detected in the Raman spectrum, in accordance with high resolution electron microscopy studies. The controlled grafting of vanadia layers onto the surface of oxidic supports is another attractive route to highly active SCR catalysts. The interaction of the carrier material with the immobilized vanadia layers can be tuned by using TiO2/SiO2 mixed oxide supports. Raman spectroscopy has been used to characterize monolayers of vanadia, which had been immobilized on a 20% TiO2/80% SiO2 mixed oxide from a vanadyl alkoxide precursor. Characteristic vibrations observed in the Raman spectrum, as well as UV-visible reflection data, indicate that the most abundant vanadia species on the surface consists of disordered polymeric arrays: the central vanadium ion is surrounded by one tightly bound vanadyl oxygen, four oxygen ions in the basal plane, and a distant sixth oxygen ligand in bridging position to the support.