Showing papers on "Mixed oxide published in 1979"

Electrical behaviour of powdered tin–antimony mixed oxide catalysts

Abstract: A series of tin + antimony mixed oxide powders, calcined at 773 K, has been studied by electrical conductivity. A continuity in the electrical behaviour is found between semiconducting SnO2 and insulating Sb2O4. Pure stannic oxide is an n-type semiconductor and its free electrons come from the first ionization of anionic vacancies whose concentration is ≈ 1018 cm–3 at 608 K under 2.13 × 104 Pa O2. The enthalpy of formation of these vacancies and the ionization energy of their 2nd electrons have been estimated. As the Sb content increases, antimony dissolves into the SnO2 structure in the 5+ state, which increases the conductivity, σ, up to a maximum corresponding to 6.1 Sb atom %. Around this value formation of the Sb2O4 phase begins. The increased conductivity of mixed oxides with high Sb content (>20 atom %), compared with that of Sb2O4, which is an insulator, is attributed to a doping effect by Sn4+ cations in Sb3+ lattice positions of Sb2O4. Comparison of how both σ and catalytic properties vary with Sb content shows that electron transfer between catalyst and adsorbed species is not the rate limiting step in propene oxidation and that the solid solution of Sb5+ in SnO2 cannot constitute the active phase for acrolein formation.

Synthesis of mixed oxide composition

Abstract: A non-aqueous gel of at least two metal oxides which is a precursor for glassy amorphous or crystalline mixed oxides is produced by reacting an alkoxide of one metal and a halide of another metal producing a low molecular weight polymeric reaction product, heating the reaction product to produce a polymeric product of substantially higher molecular weight, and heating the higher molecular weight polymeric product in air to remove its carbonaceous content.

Method of stabilising electrodes coated with mixed oxide electrocatalysts during use in electrochemical cells

Abstract: An electrochemical cell with an electrode having deposited thereon an electrocatalyst which is a mixed oxide of nickel-molydenum, nickel-tungsten, cobalt-molydenum or cobalt-tungsten and containing an aqueous alkaline electrolyte comprising an aqueous solution of a molybdenum, vanadium or tungsten compound The electrodes are preferably prepared by alternately coating an electrode core with a compound of nickel or cobalt, and with a compound of molydenum or tungsten, said compounds being capable of thermal decomposition to the corresponding oxides, heating the coated core at an elevated temperature to form a layer of the mixed oxides on the core and finally curing the core with the mixed oxide layer thereon in a reducing atmosphere at a temperature between 350° C and 600° C The cells are particularly suitable for use in the electrolysis of water or brine

Panes with IR reflecting properties - obtd. by sputtering on first an indium oxide-tin oxide layer, then a gold, silver or copper layer

Abstract: Panes which are transparent to visible light while reflecting IR are obtd. by reactive cathode sputtering of an indium oxide layer onto a substrate followed by coating with Au, Ag or Cu. A target consisting of an In alloy contg. 10-35 wt.% of Sn is sputtered in a pure O2 atmos. until a mixed oxide layer of thickness 1/100 - 1/10 of a wavelength (based on a wavelength lambda = 550 nm) is produced. A layer of Au, or Cu is then sputtered on in an inert atmos. until a layer 5-20 nm thick is obtd. Opt. another mixed oxide layer of In2O3 and SnO2 can then be applied to improve the filter properties. IR-reflecting panes are produced economically with largely uniform coatings.

Mixed oxide bonded copper conductor compositions

Abstract: Thick film copper conductor compositions useful for forming microwave conduit conductors are disclosed. The compositions contain copper, copper oxide, lead oxide and bismuth oxide dispersed in an inert liquid vehicle.

Influence of calcination on the electrical properties of tin-antimony mixed oxide catalysts

Abstract: The electrical conductivity study of Sn−Sb mixed oxide powders is consistent with an enrichment in Sb (due to calcination) of the surface region where a solid solution of Sb in SnO2 and a Sb2O4 surface phase coexist.

Oxidation of sintered cobalt oxide

Abstract: The kinetics and mechanism of the oxidation of sintered pellets of CoO and Co/sub 0/ /sub 5/Mg/sub 0/ /sub 5/O in air at high temperatures were investigated to find stable heat sources containing /sup 60/Co. The initial stages of oxidation of both materials were nuclei-growth-controlled, i.e. In (1/(1-x))=kt/sup m/. The reaction rate constant for CoO decreased at 800/sup 0/ to 960/sup 0/C, the temperature where the cobalt oxide spinel decomposed. The reaction-rate constant for decomposition of the mixed oxide was maximum at 700/sup 0/C and decreased at higher temperatures. This decrease confirmed the validity of the nuclei-growth solid-state reaction-rate equations.

Electrically conductive mixed oxide prodn. by reactive spray drying - of mixed oxide of lanthanum with manganese, nickel, or cobalt contg. chromium and small amts. of other metal cations

Abstract: Prodn. of electrically conductive oxidic material (I) for application at high temp. and in a wide range of O2 partial pressures involves adding small amts. of Cr and mono- or di-valent alkali, alkaline earth, Zn, Cd, Mn, Sn and/or Pb cations to mixed oxides with perovskite structure based on LaMnO3, LaNiO3 or LaCoO3. A soln. of the cations in the exact stoichiometric ratio is sprayed into a hot reaction tube at 1000-1500 K, together with or with injection of the O2 needed for the reaction, and the solvent is vapourised. The non-volatile constituents pass through the tube, where the desired (I) with homogeneous distribution forms in the hot reaction zone, and the powder is deposited in a cyclone, the solvent vapour being removed. (I) is useful in electrochemical high temp. cells, esp. fuel cells, and for supplying current under conditions of high temp. (hot conductors, probes etc.) and in reducing or varying gas atmos.

Electrochemical cell with an electrode having deposited thereon an electrocatalyst; preparation of said cell

Abstract: The invention relates to an electrochemical cell with ar electrode having deposited thereon an electrocatalyst whict is a mixed oxide of nickel-molybdenum, nickel-tungsten, cobalt-molybdenum or cobalt-tungsten and containing an aqueous alkaline electrolyte comprising an aqueous solution of a molybdenum, vanadium or tungsten compound. The electrodes are preferably prepared by alternately coating an electrode core with a compound of nickel or cobalt, and with a compound of molybdenum or tungsten, said compounds being capable of thermal decomposition to the corresponding oxides, heating the coated core at an elevated temperature to form a layer of the mixed oxides on the core and finally curing the core with the mixed oxide layer thereon in a reducing atmosphere at a temperature between 350°C and 600°C. The cells are particularly suitable for use in the electrolysis of water or brine.

Solid electrolyte cell for measuring oxygen activity in steel melt - uses oxidic chromium-aluminium cermet as standard solid

Abstract: Solid electrolyte cell is used for correction-free measurement of low oxygen activities in steel melts, in which the cell is immersed, by comparison with a standard solid of known oxygen activity surrounded by a solid mixed oxide electrolyte, which conducts oxygen ions but has negligible electronic conductivity at relatively high temps. The novel feature is that the standard solid consists of oxidic mixed crystals, one oxide component (I) of which is an ordinary material for the prodn. of standard substances, whilst the other oxide component (II) has a lower O2 partial pressure, and the mixed crystals of the metal components. The standard solid has an O2 partial pressure in the 10-15 to 10-12 range, as required for the determn. of oxygen activities under 50 ppm in the melt.

Method of preparing an oxychlorination catalyst

Abstract: An oxychlorination catalyst which is an intimate mixture of the oxides of magnesium, aluminum and copper obtained by calcining is prepared by precipitating the hydrated oxides of magnesium and aluminum, drying and calcining these hydrated oxides to form a mixed oxide of magnesium and aluminum, treating the mixed oxide with a copper salt solution and again calcining to provide the copper oxide.

The anodic characteristics of massive manganese oxide electrode

Abstract: The massive Mn oxides were synthesized and their anodic characteristics were investigated in aqueous solutions. The thermal treatment of the massive β-MnO 2 at 480°C or above leads to the formation of α-Mn 2 O 3 , and the relatively high activity was observed for the anodic evolution of oxygen on the mixed oxide of ν-MnO 2 and α-Mn 2 O 3 , compared with the pure oxide of β-MnO 2 . The active sites for the oxygen evolution reaction were regarded as the Mn(III) sites on the oxide surfaces. From the kinetic considerations for the oxygen and chlorine evolutions, it was suggested that the oxidation process of the electrode surface is a common rate-determining step in both reactions on the massive Mn oxide electrodes.