Al2O3 NiO Research Articles

Influence of Reducing Media on the Structure and Physicomechanical Properties of Ceramics of the ZrO2–Y2O3–Al2O3–NiO – CuO System

Influence of Reducing Media on the Structure and Physicomechanical Properties of Ceramics of the ZrO2–Y2O3–Al2O3–NiO – CuO System

Multi metal oxide CdO–Al2O3–NiO nanocomposite—synthesis, photocatalytic and magnetic properties

A multi metal oxide nanocomposite involving CdO, Al2O3 and NiO was synthesized by precipitation method. The x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) analyses confirmed the formation of heterostructured CdO–Al2O3–NiO composite. Diffraction peaks related to cubic CdO, monoclinic Al2O3 and cubic NiO were observed in the XRD pattern of the composite. SEM images confirmed the presence of spherical shaped grains for CdO, nanorods for Al2O3 and nanoneedles for NiO. Improved photocatalytic activity was observed for the composite better than the binary oxide entities due to the efficient separation of photogenerated electron-hole pairs caused by their vectorial transfer among CdO, Al2O3 and NiO. The results obtained confirmed that CdO–Al2O3–NiO could be a new promising visible light driven photocatalyst with outstanding performance. Ferrimagnetic orderings was observed for the composite which could be due to intrinsic exchange interaction of magnetic moments mediated by the defects present.

Catalysis: An Integrated Textbook

Pd/Al2O3 catalysts modified by different metal oxides (Mn, Fe, La, Mg and Ni oxides) were prepared and tested for fuel-lean methane/air catalytic combustion. It was found that the support material influenced the combustion performance significantly. The addition of NiO or MgO effectively improved the activity and hydrothermal stability of catalysts. X-ray diffraction (XRD) results showed the presence of spinel phase in the Pd/Al2O3–NiO and Pd/Al2O3–MgO catalysts. Temperature-programmed desorption of ammonia (NH3-TPD) measurements indicated that the supports became weakly acidic because of the formation of NiAl2O4 or MgAl2O4 spinel. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed the well dispersion of Pd particles on the Al2O3–NiO and Al2O3–MgO supports. It was concluded that the formation of the NiAl2O4 or MgAl2O4 spinel phase during preparation would be beneficial for the methane catalytic performance of Pd catalysts.

Synthesis of Nickel and Zinc-Doped Aluminogallate Nanocomposite Spinels with the Hydrothermal Method and Wet Atomization for NO Reduction

The levels of nitrogen oxides (NOx = NO + NO2) released from both portable and standing combustion devices are on the increase, which contributes to serious environmental problems such as global warming and air pollution. The selective catalytic reduction (SCR) of NOx by hydrocarbons (HCs) is very effective, so there have been many studies of the performance of various catalysts for HC-SCR. In this study, Ga2O3–Al2O3–NiO–ZnO (GANZ) nanocomposite metal oxides were tested as catalysts for NOx reduction by C2H4. The spinel metal oxide powders were prepared with the hydrothermal reaction method. Aluminum, gadolinium, nickel, zinc nitrate, and ammonium carbonate salts are highly water soluble and were used in these syntheses. The hydrothermally synthesized powders were then processed with wet atomization to obtain highly dispersed fine particles. Finally, the spinel powders were tested in NOx reductions performed in the presence of high levels of oxygen and at a high space velocity, which are demanding conditions since most reported catalysts are not active in this environment. The synthesized product is an uncontaminated spinel phase of GANZ and was found to exhibit high catalytic activity even in the presence of 10 % H2O vapor and SO2 at a high space velocity. GANZ catalysts were also synthesized with the co-precipitation and sol–gel methods for comparison.

Hydrogen production by high temperature water gas shift reaction over highly active and stable chromium free Fe–Al–Ni catalysts

High temperature water gas shift reaction is carried out over nanocrystalline chromium free Fe2O3–Al2O3–NiO catalysts with and without alkaline earth promoters. Mesoporous catalysts are prepared by coprecipitation method. The prepared catalysts are characterized using N2 adsorption (BET), temperature-programmed reduction (TPR) and desorption (TPD), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The results indicate that alkaline earth promoters improve the catalytic activity and suppress the progress of methanation reaction, which is related to the increment of amount in weakly basic sites through promoter addition. Furthermore, it is found that the Fe2O3–Al2O3–NiO catalyst promoted by Ba exhibits the highest catalytic activity and the lowest methanation among the prepared catalysts and the commercial chromium containing one. In addition, the effect of Ba content on the CO conversion is investigated and the results indicate that the catalyst with 3 wt.% Ba possesses high activity and stability without any decrease in CO conversion during 50 h time on stream.

Mesoporous Ba-promoted chromium free Fe2O3–Al2O3–NiO catalyst with low methanation activity for high temperature water gas shift reaction

Mesoporous Ba-promoted chromium free Fe2O3–Al2O3–NiO catalyst with low methanation activity was prepared for a high temperature water gas shift reaction. The prepared catalyst showed high surface area of 165.5m2g−1 with a particle size of 6.8nm. This catalyst exhibited stable activity and higher CO removal rate compared to Fe2O3–Al2O3–NiO catalyst and commercial chromium containing one. The results revealed that the addition of Ba noticeably suppressed the methanation activity.

Changes in the mechanical properties of support materials for segmented-in-series type solid oxide fuel cells as a function of time

As the substrate materials for segmented-in-series type solid oxide fuel cells (SOFCs), the mechanical characteristics, such as Young's modulus, of Al2O3–NiO–YSZ, TiO2–NiO–YSZ and MgO–NiO–YSZ were examined under SOFC operating conditions. The Young's modulus for all of the samples decreased at a high temperature. For the Al2O3–NiO–YSZ samples, the behaviours of the Young's modulus changed at each process including as-sintered, 100 h reduction and 2000 h reduction. For the TiO2–NiO–YSZ samples, the Young's modulus behaviour varied between the as-sintered and reduced samples. However, further reduction did not change the behaviour of the Young's modulus. For the MgO–NiO–YSZ samples, the Young's modulus of the samples exhibited a nearly constant behaviour through the sequence of processes from as-sintered to 100 h reduction and 2000 h reduction. Based on the microstructural analysis, the compositions of the framework of the samples and the sliding of the grain boundary strongly affected the Young's modulus.

Influence of metal oxides on the performance of Pd/Al2O3 catalysts for methane combustion under lean-fuel conditions

Pd/Al2O3 catalysts modified by different metal oxides (Mn, Fe, La, Mg and Ni oxides) were prepared and tested for fuel-lean methane/air catalytic combustion. It was found that the support material influenced the combustion performance significantly. The addition of NiO or MgO effectively improved the activity and hydrothermal stability of catalysts. X-ray diffraction (XRD) results showed the presence of spinel phase in the Pd/Al2O3–NiO and Pd/Al2O3–MgO catalysts. Temperature-programmed desorption of ammonia (NH3-TPD) measurements indicated that the supports became weakly acidic because of the formation of NiAl2O4 or MgAl2O4 spinel. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed the well dispersion of Pd particles on the Al2O3–NiO and Al2O3–MgO supports. It was concluded that the formation of the NiAl2O4 or MgAl2O4 spinel phase during preparation would be beneficial for the methane catalytic performance of Pd catalysts.

Preparation of Co–Al and Ni–Al layered double hydroxide thin films by a sol–gel process with hot water treatment

Using hot water treatment of sol–gel derived precursor gel films, Co–Al and Ni–Al layered double hydroxide (LDH) thin films were prepared. The precursor gel films of Al2O3–CoO or Al2O3–NiO were prepared from cobalt or nickel nitrates and aluminum tri-sec-butoxide using the sol–gel method. Then, the precursor gel films were immersed in a NaOH aqueous solution of 100 °C. Nanocrystallites of Co–Al and Ni–Al LDH were precipitated with the hot water treatment with NaOH solution. The largest amounts of nanocrystals were obtained with a solution of pH = 10 for Co–Al LDH, and with that of pH = 9 for Ni–Al LDH. X-ray diffraction measurements confirmed that this process formed CO32− intercalated LDHs. Both Co–Al and Ni–Al LDH thin films were confirmed to work as electrodes for electrochemical devices by cyclic voltammogram measurements.

Periodic antiphase boundary spinel-based structures in aluminates, gallates, aluminium oxynitrides and transition aluminas

The crystallographic structures of several transition aluminas possessing a face-centred cubic packing of oxygen anions can be considered as deriving from that of a non-stoichiometric spinel. However, they are not yet known in detail owing to the poor crystallinity of most of the samples studied by X-ray or electron diffraction. Conversely, relatively large crystals have been produced in the case of non-stoichiometric spinels in the alumina-rich (or Ga2O3-rich) parts of the Al2O3–AlN, Al2O3–MgO, Al2O3–NiO, Al2O3–Li2O and Ga2O3–MgO systems. Detailed studies of their diffraction patterns have shown that all these phases possess periodic antiphase boundary (PAPB) structures based on the spinel structure. In the case of the so-called δ-transition aluminas, various structural models have been previously proposed and in this paper we are focusing on the striking similarities between their diffraction patterns and those of several metastable PAPB aluminate structures. This makes it possible to show that at least three distinct PAPB structures must be taken into account in the case of δ-transition aluminas. APB planes are either {100} or {110} whereas APB vectors are either 1/2 ⟨001⟩ or 1/4 ⟨110⟩ when referring to the spinel structure. Neighbouring octahedral and tetrahedral incompatible sites are observed in the vicinity of each APB and cation vacancies are shown to occupy these octahedral sites.

Phase Equilibrium between Ni-S Melt and CaO-Al<SUB>2</SUB>O<SUB>3</SUB> Based Slag in CO-CO<SUB>2</SUB>-SO<SUB>2</SUB> Gas Mixtures at 1773 K

To provide thermodynamic data for converting the nickel matte to liquid nickel, an experimental study was conducted in the phase equilibrium between the Ni–S alloy and the CaO–Al2O3 based slag melted in a MgO or Al2O3 crucible at 1773 K under controlled PSO2 of 10.1 kPa and PO2 in a range between 5.0×10−3 and 1.6 Pa by using CO–CO2–SO2 gas mixtures. The contents of nickel in these slags at PO2 of 1.6 Pa, above which solid NiO is expected to precipitate in equilibrium state, were found to be 5.6 and 7.2 mass% for the slags melted in the MgO and Al2O3 crucibles, respectively. The contents of sulfur and oxygen in the nickel melt at PO2 of 1.6 Pa were 2 and 0.4 mass%, respectively. The CaO–Al2O3 based slag with the mass% ratio (CaO/Al2O3) of about 1 melted in the MgO crucible was homogeneous in the investigated PO2 range. While, that with the ratio of about 0.5 melted in the Al2O3 crucible formed two phases composed of a liquid and an Al2O3–NiO solid solution whose nickel content was increased with increasing PO2. The dissolutions of nickel and sulfur in the slag melted in the MgO crucible were discussed on the basis of distribution ratio and sulfide capacity, respectively.

The effect of the grain structure of Al2O3 substrate on the solid state reaction with a layer of NiO: A comparative backscattering spectrometry study 1

AbstractThe solid state reaction of Al2O3NiO reaction couples was investigated by means of Rutherford backscattering spectrometry. NiO films on the alumina substrates were obtained by vapour–deposition of Ni and subsequent oxidation at 800°C in air. Substrates of about the same surface roughness, thus providing equal contact areas for the reaction couples, were used. The materials were characterized by scanning electron microscopy. In spite of the different structure and a grain size that varied within a factor of 10, of the Al2O3 materials, no obvious difference in the spectra based on the used reaction couples could be detected. Suggested substantial contribution to the reaction from surface diffusion and grain boundary diffusion along the substrate grain boundaries could therefore be rejected.

Phases ε obtenues par decomposition des spinelles non-stoechiometriques dans les systemes Ga 2O 3-MgO, Al 2O 3-NiO, Al 2O 3-AlN et Al 2O 3-Li 2O

In the systems Al 2O 3-AlN, Al 2O 3-NiO, Al 2O 3-Li 2O and Ga 2O 3-MgO, non-stoechiometric spinels, when decomposed at high temperatures, form an intermediate metastable phase ε. This phase has a one-dimensional periodic antiphase-domain structure. The antiphase boundaries are parallel to the (310) plane and the displacement vector is 1 4 [110] when referred to the spinel structure. Across each antiphase boundary, some octahedral and tetrahedral sites share faces instead of corners. In the case of ε AlN, cationic vacancies occupy these sites; in the other cases, this is likely to go along with a segregation of the more charged ions.