Papers by Keyword: Cobalt Oxide

Abstract: Oil reservoir formation damage is a significant issue in secondary and tertiary oil recovery operations. Enhanced oil recovery (EOR) approaches can address these issues while increasing production rates and resource recovery. However, challenges include chemical degradation, high chemical volumes, and high costs. Nanotechnologies can improve oil recovery by improving subsurface porous media and pore fluids, separating fluid phases, and introducing influencing coatings. Cobalt oxide-based materials have been extensively evaluated for their amphiphilic properties, thermal stability, and high reactivity, which can modify physicochemical properties and improve crude oil recovery. CoO nanoparticles were characterized using various techniques, including Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectronic spectrometry, and Field Emission Scanning Electron Microscope (FSEM). Results showed that CoO nanofluid positively affects reservoir minerals with electromagnetic fields and improves oil recovery. It also improves thermal stability, promotes stable emulsion formation, decreases the interfacial tension (IFT) up to 15% for the light-crude-oil/water system at concentrations of 0.5 wt% nanofluid, and can improve thermal stability with respect to CoO in a wide range of temperatures, favouring the formation of stable emulsions.

Abstract: The preparation of apolymeric membrane by a chemical method was introduced for a Polymer Electrolyte Membrane (PEM) fuel cell. Cobalt oxide (Co₃O₅) was used in the coexistent of two polymers to speed up the reaction process and to obtain the best results. Different tests were implemented along the research to evaluate the new membrane such as X-ray, Scanning Electron Microscopy (SEM) and Fourier-Transform Infrared Spectroscopy (FTIR). The new membrane shown an increment both in the current (I) and the volume of Hydrogen (H₂) at a constant voltage (V).

Abstract: Nanoparticles fabrication using pulsed laser synthesis is considered a straightforward, reliable, and green approach for the fabrication of nanomaterials. In this study, cobalt oxide (CoO) nanoparticles were synthesized from cobalt targets using pulsed laser ablation inside a 10% v/v ethanol solution. This study examined the effect of the laser energies on the size and morphology of CoO nanoparticles. The size, morphology of the fabricated nanomaterials were studied using transmission electron microscopy (TEM), and their optical properties were obtained using ultraviolet-visible (UV-Vis) spectroscopy. Uniform size distribution of nanoparticles with diameters less than 60 nm was observed at 30, 45, and 60 mJ. The optimum condition at which the CoO nanoparticles are fabricated with a narrower size distribution was reported, which would be helpful in several applications such as electronic thin film, pigments and dyes, capacitors, gas sensors, and lithium-ion batteries.

Abstract: High energy and power density, good life cycle are highly sought in fabricating supercapacitors. In this study, Co₃O₄ was successfully deposited on nickel foam via electrochemical route. The nucleation of cobalt hydroxide and its transformation to oxide were monitored using chronoamperometry and cyclic voltammetry. Changes in current density and detected redox peaks suggest the electrochemical activity of Co₃O₄ in an alkaline media. A specific capacitance 1291 F/g at current density of 2.5 mA/cm was achieved showing the supercapacitive property of the synthesized Co₃O₄. EDX results confirms the incorporation of samarium to cobalt oxide. Furthermore, scanning electron microscopy (SEM) reveals the evolution of nanosheets to nanoflowers as the electrochemical synthesis parameters were varied. The effect of morphology on the electrochemical activity and performance of Co₃O₄ with Samarium could pave way in developing high energy and power density electrode for supercapacitors.

Abstract: Cobalt oxide (Co₃O₄) nanosheets were successfully synthesized and deposited onto the nickel foam substrate via electrochemical route. The chronoamperograms during the deposition revealed electrochemical activity resulting to the nucleation of the cobalt ions forming cobalt hydroxide and transformation to cobalt oxide. Energy dispersive xray (EDX) results elucidates the presence of samarium, cobalt and oxygen in the sample. The formation of nanosheets was confirmed by scanning electron microscopy. It was found that adding more samarium in the electrochemical bath changes the morphology of the final product from nanosheets to nanoflowers. The evolution of nanosheets to nanoflowers of the synthesized material could pave way for its potential application in the field of electrochemical energy storage devices and electrochemical sensors.

Abstract: Ultrafine Co₂O₃ powder was prepared via hydrothermal synthesis. The effect of technology on the performance of the superfine Co₂O₃ powders was investigated, and the hydrothermal parameters in preparing Co₂O₃ were gradually improved. In addition, the morphology and grain size of the Co₂O₃ powder were analyzed by FESEM. Results show that reducing the salt–alkali molar ratio resulted in more uniform Co₂O₃ powder and smaller particles, with average particle size of approximately 40 nm. Reaction time displayed little effect on the Co₂O₃ powder, but the particle size decreased with the reaction time. The concentration of salt solution remarkably affected the morphology of the Co₂O₃ powder. Lower concentration resulted in smaller particle aggregation and particle size.

Abstract: Cobalt (Co) nanowires were synthesized via electroless deposition in ethylene glycol under an external magnetic field then oxidized in air via thermal oxidation at 250 to 300 °C. The nanowires have lengths in the range of 10 to 14 µm while the diameter increases with oxidation temperature. This can be attributed to the partial melting of the nanowires during oxidation, resulting to sintering. The peaks in the XRD patterns show complete oxidation of Co nanowires, producing a mixture of Co₃O₄ and CoO. It was observed that Co₃O₄ and CoO peaks were more intense at 270 °C. There is a decrease in specific capacitance (F/g) with increase in scan rate due to poor electron exchange between active material electrode and electrolyte. Highest calculated specific capacitance was 339.28 F/g using nanowires oxidized at 270 °C at 1 mV/s scan rate.

Abstract: The morphology of cobalt oxide / cobaltous oxide (Co₃O₄) nanostructures was controlled using different seed layer concentrations and deposition time. Co₃O₄ nanostructures were deposited on ITO glass synthesized using two step solution route. The morphological evolution of the Co₃O₄ nanostructures has been investigated using scanning electron microscopy (SEM). This has been correlated to the electrochemical activity of the material using cyclic voltammetry (CV) in a potassium hydroxide (KOH) and phosphoric acid (H₃PO₄) media. Other characterization technique such as x-ray diffraction analysis (XRD) was used to verify the crystal structures of the Co₃O₄ nanostructures. The Co₃O₄ nanostructures revealed pronounced redox peaks in a 1M KOH electrolyte which proved its high electrochemical activity. Also the redox peaks increases with the increase in scan rate which demonstrated good reversibility of a fast charge-discharge response. Varying CV curves have been observed in a 1M H₃PO₄ electrolyte which denotes the instability of Co₃O₄. The change in the morphology of Co₃O₄ certainly affects the electrochemical property of the Co₃O₄. This leads to an advance study for its promising electrochemical applications for a cleaner energy.

Abstract: Metal oxide semiconductors such as cobaltous oxide (Co₃O₄) and cuprous oxide (Cu₂O) have caught the attention of many researchers due to their wide variety of applications. The attachment of Cu₂O to Co₃O₄ was assisted by polyethylene glycol and the nanostructuring by ultrasonic sound. X-ray Diffraction (XRD) analysis of the fabricated composite reported characteristic peaks for crystalline Co₃O₄ and Cu₂O. Results from Energy Dispersive X-ray (EDX) Spectroscopy showed the presence of cobalt, copper, and oxygen atoms which supports the result obtained in XRD. Cauliflower to nearly spherical shaped Cu₂O - Co₃O₄ nanostructures were formed as observed in the Scanning Electron Micrographs (SEM) with a mean diameter of 0.5-1.0 μm. the shape of the composite and its surface morphology was altered with the use of different precursor materials for the synthesis of the Co₃O₄ seed. A blue shift in the UV-vis was observed upon the use of nitrate based precursor indicating the presence of smaller and finer particles in the composite. Overall results prove that Cu₂O and Co₃O₄ can be synthesized using a facile solution approach with the aid of PEG and ultrasonic sound its application in the field of photocatalysis is probable.

Abstract: The most promising application field of materials based on nano-sized Co₃O₄ is catalysis. The method of production is one of the factors, which greatly affects the catalytic activity of Co₃O₄ catalysts. The aim of this research is to study possibilities of a new promising extractive-pyrolytic method (EPM) for the production of Co₃O₄ nanopowders and silica- and ceria-supported Co₃O₄ nanocomposites. Solutions of cobalt hexanoate in hexanoic acid and trioctylammonium tetrachlorocobaltate in toluene preliminary produced by solvent extraction were used as precursors. The precursors’ thermal stability, phase composition, morphology and the magnetic properties of the final products of pyrolysis were studied. The performed investigations have shown that the mean size of the Co₃O₄ crystallites in the materials produced by the EPM varies from amorphous to 55 nm due to the production conditions.