“…4. The broadband at 3430–3450 cm −1 frequency observed at the spectra is attributed to the stretching vibration of hydroxyl group which exist in LHD layers and inter-lamellar water molecules [24, 33, 34]. Fig.…”
Cobalt-chromium layered double hydroxide (CoCr LDH), α- and β- Co(OH)2 and amorphous Cr(OH)3 have been synthesized under different reaction conditions. The obtained CoCr LDH was modified by stearic acid (SA) and sodium stearate (SS). The obtained samples have been characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), Ultraviolet-visible- (UV-Vis), Fourier transform infrared- (FTIR) and Energy-dispersive X-ray- (EDX) spectroscopy. The influence of reaction conditions on product composition, structural and optical properties of the samples have been discussed in detail. The basal spacing of CoCr-LDH increased from 7.366 Å to 7.428 Å and 25.214Å after the intercalation by stearic acid and sodium stearate, respectively. The average particles size by SEM analyze was estimated to be approximately 100–150 nm and 30–50 nm for CoCr-LDH0.6M(90°C) and CoCr-LDH0.6M(90°C)/SS nanostructures, respectively. Mixed hydroxides like α- and β- Co(OH)2 have been obtained along with LDH at lower pH value (pH ∼ 7). The number of diffraction peaks corresponding to β-Co(OH)2 has increased with relatively decreasing of Co2+ ions in the reaction medium. At high chromium concentrations (Co2+:Cr3+ = 1:3 and 1:5), amorphous Cr(OH)3 were formed in the experiment.
“…4. The broadband at 3430–3450 cm −1 frequency observed at the spectra is attributed to the stretching vibration of hydroxyl group which exist in LHD layers and inter-lamellar water molecules [24, 33, 34]. Fig.…”
Cobalt-chromium layered double hydroxide (CoCr LDH), α- and β- Co(OH)2 and amorphous Cr(OH)3 have been synthesized under different reaction conditions. The obtained CoCr LDH was modified by stearic acid (SA) and sodium stearate (SS). The obtained samples have been characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), Ultraviolet-visible- (UV-Vis), Fourier transform infrared- (FTIR) and Energy-dispersive X-ray- (EDX) spectroscopy. The influence of reaction conditions on product composition, structural and optical properties of the samples have been discussed in detail. The basal spacing of CoCr-LDH increased from 7.366 Å to 7.428 Å and 25.214Å after the intercalation by stearic acid and sodium stearate, respectively. The average particles size by SEM analyze was estimated to be approximately 100–150 nm and 30–50 nm for CoCr-LDH0.6M(90°C) and CoCr-LDH0.6M(90°C)/SS nanostructures, respectively. Mixed hydroxides like α- and β- Co(OH)2 have been obtained along with LDH at lower pH value (pH ∼ 7). The number of diffraction peaks corresponding to β-Co(OH)2 has increased with relatively decreasing of Co2+ ions in the reaction medium. At high chromium concentrations (Co2+:Cr3+ = 1:3 and 1:5), amorphous Cr(OH)3 were formed in the experiment.
“…Despite extensive investigations ,,,,,, of NiO reduction by methane, many questions remain about its kinetics and molecular and structural transformation mechanisms. The carbon deposition, however, limits the kinetic measurement of NiO reaction with CH 4 . , Nonisothermal experiments with low heating rates (25 K/min) showed that reduction starts at ∼625 K and the full conversion can be achieved at ∼1000 K, while further heating results in pyrolytic carbon deposition . The use of diluted CH 4 allows overcoming such difficulty in kinetic measurements.…”
Section: Introductionmentioning
confidence: 99%
“…33,34 Nonisothermal experiments with low heating rates (25 K/min) showed that reduction starts at ∼625 K and the full conversion can be achieved at ∼1000 K, while further heating results in pyrolytic carbon deposition. 34 The use of diluted CH 4 allows overcoming such difficulty in kinetic measurements. For example, Rashidi et al used the thermogravimetry method to investigate the reaction kinetics under the argon-diluted CH 4 gas flow.…”
Nickel oxide reduction by methane is of particular importance in catalysis, extractive metallurgy, and clean power generation technologies. Despite extensive investigations of the NiO + CH 4 reaction, many questions remain about its kinetics and molecular and structural transformation mechanisms. This work reports the reduction kinetics of bulk polycrystalline NiO by CH 4 using a new calorimetric method. The method permits rapid, controllable heating of the NiO/Ni wires and continuous data (electrical power, the electrical resistivity of the wire, and temperature) acquisition with a frequency of 10 kHz. The method also allows arresting and preservation of the structure of the sample by programmed termination of electric power in thin specimens. This approach, coupled with ex situ electron microscopy, allows determination of the reaction rate and tracking of the ongoing structural transformations. The mechanism of NiO reduction by methane is suggested based on direct correlations between reaction kinetics and the observed microstructure transformations. The kinetic data treatment revealed that the nucleation−growth model describes the reaction kinetics. Ex situ microscopy observations of reacted specimens showed that the first nuclei rapidly accelerate the process. Pore formation occurs at the nucleation sites, and the porous structure then quickly grows into the bulk NiO. The second type of reduced Ni microstructure, compact layer, can be observed only on the outer surface of the wire. Based on kinetic data and microstructural observations, a mechanism of reduction was suggested according to which porous microstructure forms predominantly by NiO reduction with carbon. The compact layer observed on the outer surface of the wire forms through the diffusion-controlled hydrogen reduction.
“…The anneal probably leads to a thermal reduction of the material, as has been reported in ref. [ 29 ] . Apparently, this is only the case if excess oxygen is present, as a stoichiometric film is not reduced further (at this temperature).…”
Thin films of the prototypical charge transfer insulator nickel oxide appear to be a promising material for novel nanoelectronic devices. The fabrication of the material is challenging, however, and mostly a p-type semiconducting phase is reported. Here, the results of a factorial experiment are presented that allow optimization of the properties of thin films deposited using sputtering. A cluster analysis is performed, and four main types of films are found. Among them, the desired insulating phase is identified. From this material, nanoscale devices are fabricated, which demonstrate that the results carry over to relevant length scales. Initial switching results are reported.
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