Materials based on aluminum and iron oxides obtained by the hydrothermal method

The influence of the relation [Al³⁺] : [Fe³⁺] on the phase composition and morphology of the products obtained by the hydrothermal method using solutions of salts of metals and combined sols of aluminum and iron (3+) hydroxides has been studied. The hydrothermal treatment of solutions of salts of aluminum and iron (3+) results in the formation of hematite of a cylindrical or capsular shape, while by the treatment of sols, depending on the relation [Al³⁺] : [Fe³⁺], it is possible to obtain particles of hematite with an ellipsoidal shape or bundles of amorphous AlOOH.     

Electrochemical synthesis of perovskite oxides

Hydroxide precursors to perovskite oxides of the formula, LnMO₃ (Ln = La, Pr, Nd; M = Al, Mn, Fe) and LaMO₃ (M = Co and Ni) were synthesized by electrogeneration of base by cathodic reduction of the appropriate mixed-metal nitrate solution. The precursors were heat treated at different temperatures to obtain the perovskite oxides. The bath composition for various systems was optimized to get a single-phase oxide product. This method can be adapted as a simple route to the synthesis of perovskite oxide coatings on conducting substrates.     

电合成纳米金属氧化物

电合成技术提供了一种简单而价廉的方法合成陶瓷薄膜和纳米材料。总结了电合成反应的特点 ,讨论了影响电合成反应的因素 ,综述了用电化学方法合成纳米氧化物的各种可能机理     

Electrochemical synthesis and characterization of mixed molybdenum-rhenium oxides

The electrodeposition of Mo_xRe_1−xO_y films (0.6 ≤ x ≤ 1) on indium-tin oxide (ITO) coated glass substrates from acidic peroxo-polymolybdo-perrhenate solutions is described. Trends in film growth were established as a function of potential from +0.4 V to −0.7 V vs Ag/AgCl by analyzing the composition and stoichiometry of the deposit using inductively coupled plasma mass spectrometry (ICPMS) and X-ray photoelectron spectroscopy (XPS). These experiments show that the concentration of rhenium increases linearly with the deposition potential and that the deposits are mixed-valent containing up to five different metal oxidation states (i.e., Mo^IV, Mo^V, Mo^VI, Re⁰, Re^IV). Electroanalytical techniques were used to explore the deposition mechanism, including chronocoulometry, cyclic voltammetry, spectroelectrochemistry, and electrochemical quartz crystal nanogravimetry (EQCN). At potentials positive to −0.26 V, perrhenate (Re^VIIO₄⁻) behaves as a redox mediator to accelerate the deposition of a mixed-valent molybdenum oxide, but at more negative potentials mixed molybdenum-rhenium oxides are produced.     

Precursor synthesis and properties of nanodispersed tungsten carbide and nanocomposites WC:nC

Nanoscale tungsten carbide (WC) and WC:nC nanocomposites have been synthesized by the precursor method. The precursor, obtained in the form of a glassy mass by thermal treatment of a mixture of (NH₄)₁₀W₁₂O₄₁∙7H₂O and glycerol, was heated in inert gaseous atmosphere up to 1050–1100 °C. The concentration of chemically active carbon in the precursor and nanocomposites depends on the W/C ratio in the initial mixture. At W/C=1/3 pure tungsten carbide is formed; at W/C>1/3 composites of WC and free carbon (WC:nC) are formed. Heating of the precursor with W/C=1/6 up to 1100 °C in helium atmosphere results in the formation of carbon-encapsulated tungsten carbide nanoparticles. An increase in the precursor-heating rate leads to the formation of chain-like structures. Each chain consists of hexagonal WC grains with unit cell parameters a=2.93 Å and c=2.83 Å. Free carbon in WC:nC composites forms agglomerates of carbon “nano-onions” of spherical or multi-layered tubular shapes.     

Electrochemical synthesis and properties of polybenzoxazine

A new kind of polybenzoxazine, poly(3-(p-methyl) benzyl-3,4-dihydro-6-methyl-2H-1,3-benzoxazine), has been synthesized by an electrochemical method in acetonitrile/alkali aqueous solution. The obtained film shows good heat resistance properties. The structure of the obtained film is characterized using Fourier Transform Infrared (FTIR) spectroscopy.     

Role of iron and aluminum oxides as fluxes during the burning of Portlamd cement

Phase equilibrium data show that A?₂O₃ and Fe₂O₃ act as fluxes during the burning of Portland cements. In principle, interactions between the four major components of cement can be determined directly from the relevant phase diagrams but in practice, supplementary constructions are almost essential to show the quantitative relationship between temperature, chemical composition and the amount of liquid formed. The concept of ‘clinkering diagrams’ is developed and applied. The principles underlying the selection of fluxes to assist clinkering reactions are discussed.     

Effect of nanodispersed zirconium dioxide on the consolidation and properties of a zircon-based ceramic

Electron microscopy and thermomechanical analysis are used to study how introducing nanodispersed ZrO₂ powder stabilized with Y₂O₃ into a zircon-based composite affects the production and properties of the composite. It was established that the introduction of more than 1 mass %of nanodispersed ZrO₂ slows the consolidation of the zircon matrix during sintering. Sintering a zircon-based composite with 15 mass % ZrO₂ by the regime that was developed in the study makes it possible to reduce the porosity of the material and significantly increase its ultimate compressive strength. It was also determined that nanodispersed particles of ZrO₂ react with SiO₂ formed during thermal dissociation of the zircon to form zircon of nonstoichiometric composition.     

3种氢氧化铝佐剂的理化性质分析

目的分析3种氢氧化铝佐剂的理化性质。方法通过X-射线衍射(X-ray diffraction,XRD)、透射电镜观察、颗粒大小和吸附能力检测、沉降分析及灭菌前后p H变化检测分析本室配制的氢氧化铝佐剂(佐剂C)与两种商品化的氢氧化铝佐剂(佐剂A和佐剂B)的理化性质。结果 3种氢氧化铝佐剂均为弱晶型勃姆石(poorly-crystalline boehmite,PCB)的晶体形态,颗粒大小主要分布在1~10μm,吸附能力均大于2 mg BSA/mg Al,沉降情况符合《欧洲药典》(7.0版)的要求,灭菌前后p H值变化均小于0.5。结论本室配制的氢氧化铝佐剂与商品化氢氧化铝佐剂多数检测参数值较接近,但吸附能力高于商品化佐剂。本研究为氢氧化铝佐剂质控标准的建立提供了参考。     

Electrochemical oxidation of divalent iron mixed oxides using carbon paste electrodes

The electrochemical behaviours of several iron(II) mixed oxides, Fe(II)M₂O₄ [where M = Fe(III), Al(III) and Cr(III)], and Fe(II) Ti(IV)O₃ were investigated using a carbon paste electrode with 1 M HCl binder. Solids containing Fe(III), Al(III) and Ti(IV) are not oxidized when the potential varies from +0.2 to + 1.1 V/sce whereas FeCr₂O₄ exhibits two oxidation peaks. The first one at about +0.4 V/sce, is due to iron(II) ions because the finest particles (< 100 nm) are immediately chemically solubilized. The second peak occurring at more positive potential is larger and corresponds to the oxidation of the biggest particles. This behaviour is similar to that of the reduction of Fe₂O₃ described elsewhere. So the oxidation phenomenon is the addition of two consecutive steps: a chemical solubilization followed by an oxidation and the shape of the second peak is influenced by the morphology of the oxide under study. Influences of the nature of the binder, of the synthesis procedure and of the grinding are reviewed.     

Electrochemical polymerization and initial corrosion properties of polyaniline-benzoate film on aluminum

Electrochemical synthesis of polyaniline (PANI) on aluminum electrode from aqueous solution of 0.25 mol dm⁻³ aniline and 0.2 mol dm⁻³ sodium benzoate has been investigated under potentiodynamic and galvanostatic conditions. Initial corrosion behavior of aluminum and PANI coated aluminum electrode exposed to 3% NaCl has been investigated using electrochemical potentiodynamic and impedance spectroscopy technique (EIS). It was shown that PANI coating initially provide corrosion protection of aluminum, decreasing the corrosion current density at least 15 times.     

Combustion of highly exothermic mixtures based on iron and chromium oxides

The combustion of highly exothermic heterogeneous mixtures containing metal oxides (FeO, Cr₂O₃) and metallic (Al) or nonmetallic (C) reducing agents has been studied under dynamic conditions. A relation between the temperature of ignition and the ratio of the components of the mixture has been established. The ignition temperature was compared with the theoretical value derived from the quasisteady theory of ignition of condensed systems of hot material with a high thermal conductivity and a variable surface temperature. The theoretical values were in agreement with the experimental results.Chernogolovka. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 4, pp. 46–48, July–August, 1993.     

Composite materials based on sitall glass and technical aluminum and titanium oxides

The possibility of fabrication of glass-ceramic composite materials based on sitall glass of the SiO₂-TiO₂-Al2O₃-CaO-BaO-B₂O₃ nonalkaline system and fillers-powdered industrial oxides with low sintering and crystallization temperatures and high wear resistance — was investigated. Industrial aluminum and titanium oxides were used as the fillers.