Synthesis Of Spinel Research Articles

Effect of solvent, in the sol–gel synthesis of CoAl2O4, on the structure and catalytic properties in 1,4-butanediol dehydrocyclization

This work presents the synthesis of CoAl2O4 spinel by the sol–gel method using different solvents, such as water, ethanol, methanol and butanol, and cobalt and aluminum precursors.

Study of catalytic oxidation of toluene using Cu-Mn, Co-Mn and Ni-Mn mixed oxides catalysts

The successful synthesis of AMn2O4 (A = Co, Cu, and Ni) spinels via solution combustion was achieved in less time than other methods. All catalysts with the same fuel/nitrate ratio were used to oxidize toluene, and the relationship between their properties and activities was investigated. Among all, nickel manganite exhibited the most promising activity, and by changing the fuel/nitrate ratio, it was sought to obtain the most appropriate structure for the reaction studied. Physico-chemical analysis was used to define the characteristics of the synthesized catalysts. The results showed the successful synthesis of spinels and indicated that other materials peaks (single oxide phases) exist in the catalyst structure. BET-BJH analyses reveal the mesoporous structures and, given the limitations of the equipment, were all classified as less than 10 m2/g. The SEM images evidence the influence of the urea content used. The particle size increases at higher fuel/nitrate ratios. Samples of NiMn1.67 and NiMn2.08 showed larger and denser, sparsely dispersed clusters. Simultaneously considering reactor analysis and test results, it was found that the synthesized catalyst with a fuel/nitrate ratio of 0.5 has the best performance on toluene oxidation.

Rapid microwave-assisted synthesis and magnetic properties of high-entropy spinel (Cr0.2Mn0.2Fe0.2Co0.2-xNi0.2Znx)3O4 nanoparticles

High-entropy oxide (HEO) has recently become popular because of its unique multifunctional performance. In this study, we developed a novel microwave-assisted method for the production of HEO nanoparticles with the composition (Cr0.2Fe0.2Mn0.2Co0.2-xNi0.2Znx)3O4 (x = 0, 0.05, 0.1, and 0.2). The results revealed that all metallic elements were uniformly distributed throughout the single-phase cubic spinel structure of the HEO nanoparticles. The particle size distributions of four fabricated samples ranged from 10 to 50 nm. Because of its numerous advantages such as the ultrafast and low-temperature fabrication of nanoscale and high-purity products at a relatively low cost, the suggested methodology is an excellent synthesis method. The original HEO spinel (x = 0) achieved saturated magnetization (Ms) and coercivity (Hc) values of 24.3 emu/g and 160 Oe, respectively, at room temperature. Zinc substitution in the HEO composition indicated that Ms and Hc decreased with increasing zinc concentration owing to its non-magnetic nature.

Forsterite and magnesium aluminate spinel synthesis and silver extraction by calcination of silicon solar cell from discarded solar Pv panels with bischofite

Forsterite and magnesium aluminate spinel synthesis and silver extraction by calcination of silicon solar cell from discarded solar Pv panels with bischofite

Effect of zinc ion on synthesis of chromium-containing spinel from wastewater and insight into the synthesis mechanism

Stable spinel can be synthesized in chromium-containing wastewater by ferrite process, which can not only realize the purification of chromium-containing wastewater, but also make chromium resource in the wastewater recycle. However, zinc ion often exists in the chromium-containing wastewater, and easily enters the spinel structure when the wastewater is treated by the ferrite process. Therefore, the effect of zinc ion on the synthesis of chromium-containing spinel from the wastewater was investigated, and the synthesis mechanisms was revealed. The quality of the filtrate, stability and magnetic properties of products synthesized at different initial concentrations of zinc ion were examined, and the results verified that moderate zinc ion enhanced the stability of chromium and magnetic properties of synthetic products, but excessive zinc ion reduced the quality of the filtrate. The synthetic path of products was illustrated by examining the stability and crystal evolution of synthetic product, monitoring the potential and pH, testing the dissolved oxygen, and analyzing the contents of metal ions in the filtrate. The synthesis mechanism was further confirmed by SEM-EDS and mössbauer spectra, and the results demonstrated that the gained solid products were mainly composed of goethite and spinel. It was deduced that the molecular formula of synthetic spinel wasFe3.243+(Fex2+⋅Fe2-x3+⋅Cry3+)O1.5y-0.5x+7.86 in the absence of zinc ion. However, the molecular formula of synthetic spinel was (Zn0.52+⋅Fe2.743+)(Fex2+⋅Fe2-x3+⋅Cry3+)O1.5y-0.5x+7.61 in the presence of zinc ion. The study laid a theoretical foundation for the industrial application of ferrite process in the chromium-containing wastewater.

Effects of clay and fireclay addition on the properties of magnesia–forsterite–spinel refractories synthesized at different firing temperatures

This study investigates the effects of adding clay and fireclay on the physical and mechanical properties of magnesia-based refractories such as contraction, bending strength, bulk density, and apparent porosity. Domestic raw materials were used for the preparation of samples fired at 1350, 1450, and 1550 °C for 2 h. Adding clay exhibited no significant effect on the density and porosity, whereas adding fireclay had a remarkable influence on the shrinkage. Nevertheless, the effects of clay and fireclay on the strength of magnesia were unnoticeable. X-ray diffraction results showed that, after firing, the main phase compositions of the samples with clay addition were periclase and forsterite. Adding fireclay led to the synthesis of magnesite spinel, which can be attributed to the high alumina content. Based on scanning electron microscopy, no liquid phase was formed indicating that the sintering was a solid-state evolution with the synthesis of forsterite.

Exploring the promotional effect of transition metals (Cr and V) on the catalytic activity of MgO for glycerol carbonate synthesis

This work reports the reactivity of Mg containing spinels like MgCr2O4 and MgV2O4 for synthesis of glycerol carbonate from bio-glycerol on the basis of their structural, morphological and catalytic properties. Metal oxides having spinel structure exhibit very amazing catalytic properties due to their unique crystal structure and multiple properties like extended surface area, higher basic strength and multiple redox centres. Several characterization techniques like XRD, XPS, TGA, Raman, N2 adsorption-desorption and SEM-EDX study confirmed the successful synthesis of spinels. Amongst MgCr2O4 (MCO) and MgV2O4(MVO), MCO proved to be very active and contributed excellent catalytic activity towards glycerol valorisation i.e. 98% conversion of glycerol at mild reaction conditions than that of MVO (82% conversion of glycerol). MCO was highly efficient than that of MVO because of its higher basicity, higher crystallite size which are the fundamental properties for enhancing the catalytic activity of heterogeneous catalysts. From environmental point of view MCO was very flexible, efficient and environmentally friendly catalyst as having ideal E-factor, PMI, and AE values. Overall description concluded that the metal oxide spinels are quite active and enormously applied in glycerol biorefinery in lab scale as well as industrial scale.

An electrophoretic co-deposition of metal oxides followed by in-situ copper manganese spinel synthesis on AISI-430 for application in SOFC interconnects

Electrophoretic co-deposition of copper and manganese oxides followed by in-situ reactive sintering is investigated as a method of Cu–Mn spinel coating for application in SOFC interconnects. Effect of electrophoretic deposition parameters including time, voltage, solid concentration and dispersant content on the quality and quantity of deposition are examined. A uniform layer of oxides is co-deposited at 100 V, in 10 min, with 10 g/L oxides in ethanol-acetone solution and 1:16 w/w dispersant:oxides. Based on XRD and SEM-EDS results, rate of Fe and Cr diffusion is unacceptable at above 850 °C. 3 h of sintering in air at 800 and 850 °C is best to synthesize spinel without severe Fe–Cr contamination. In a 100-h cyclic oxidation test, coatings prevent chromium poisoning and reduce the oxidation rate by a minimum of two orders of magnitude decrease in the parabolic rate constant of oxidation from 1.34 × 10−12 in uncoated to 8.50 × 10−14 g2 cm−4 s−1 and 32.3% decrease in Cr at.% in the coated samples.

Complex Processing of Adsorbent Used in the Purification of Hydrogen-Containing Gas

The problems of processing spent adsorbents with a high concentration of chemisorbed chlorine-containing compounds for their reuse are studied in this article. The genesis of the phase composition and morphology at all technological stages of thermochemical regeneration of the spent adsorbent - Axstrap-860 by means of alkaline modification with a combined solution of sodium and potassium hydroxides has been tested by diffractometry and elemental analysis. The results show that the formation of a layer with an increased concentration of alkali metals in the form of the corresponding carbonates and NaOH on the surface of the granules and in the volume of sodium and potassium aluminates provides adsorption of HCl, which are slightly inferior to the fresh adsorbent. The conditions for the removal of halogen-containing substances from technogenic raw materials with the subsequent isolation of useful products have been optimized: (1) crystalline NaCl intended for the preparation of electrolyte for electrode boilers and steam generators; (2) a mixture of chlorides and hydroxochlorides of aluminum tested in the process of coagulation purification of turbid natural and waste waters; (3) pseudoboehmite for the production of an adsorbent-desiccant and the synthesis of magnesium-aluminum spinel using the technology of destruction-epitaxial transformation, and a promising carrier for catalysts for steam reforming of hydrocarbons. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Electroplating Sludge-Derived Multiple-Metal-Doped Spinel with Superior CO Selectivity in Reverse Water–Gas-Shift Reaction

At present, carbon reduction is one of the hottest topics and CO is the raw source of many industrial products. For the first time, this work reported CO2 conversion to CO with superior selectivity via hydrogenation using an electroplating sludge-derived catalyst. As a result, the optimized catalyst attained a best CO2 conversion of 45.88% and CO selectivity of 99.97% at 600 °C. What is more, the catalyst stably maintained a high conversion of 55.39% and selectivity of 99.68% for 100 h at 550 °C. At the same time, the total amount of byproducts was less than 0.32%. After detailed characterizations, the catalyst was featured by CuFeMn-doped ZnCr spinel, which had the ability of mild C–O dissociation and weak CO adsorption. After all, above results show that electroplating sludge is a good precursor for the synthesis of spinel for excellent catalytic CO2 conversion to CO.

Micro-mechanism of Shear Strength and Water Stability Enhancement of Montmorillonite by Microwave Heating

Microwave heating potentially reinforces the muddy intercalation to eliminate slope failure. Montmorillonite has the worst water resistance among the muddy intercalation components, which is a primary facet of inducing muddy intercalation failure. This study investigates the mechanism of shear strength and water stability enhancement of montmorillonite heated by the microwave oven and muffle furnace from room temperature to 800 °C. Results show that montmorillonite mineralogical evolution can be divided into three stages: room temperature-300 °C, 300-600 °C, and 600-800 °C. Microwave heating is more efficient in montmorillonite heat treatment than muffle furnace heating and makes the montmorillonite dehydroxylated earlier. It is worth noting that hot spots formed inside the montmorillonite specimens during the microwave heat treatment. Microwave significantly promotes the shear resistance of montmorillonite, where the maximum increases are 39.94% of cohesion at 600 °C and 20.54% of internal friction angle at 700 °C. This enhancement is due to the rough surfaces and large particles produced by dehydroxylation and Mg-Al spinel synthesis, and the significant degree of disorder state of MMT after dehydroxylation also plays a vital role. The microwave-heated montmorillonite over 500 °C presents good integrity in the water immersion test over 24 h. Considering the shear behavior and water stability, we believe the most reasonable heating interval for microwaves is 500-600°C.

Parameters of Glycine–Nitrate Synthesis of NiCo2O4 Spinel

Parameters of Glycine–Nitrate Synthesis of NiCo2O4 Spinel

Synthesis of Anti-poisoning Spinel Mn-Co-C as Cathode Catalysts for Low-Temperature Anion Exchange Membrane Direct Ammonia Fuel Cells.

Low-temperature anion exchange membrane direct ammonia fuel cells (AEM-DAFCs) have emerged as a potential power source for transportation applications with the recognition that liquid ammonia is a carbon-free hydrogen carrier and facilitates storage, refill, and distribution. However, ammonia crossover from the cell anode to cathode can decrease the fuel efficiency, drop the voltage, and poison the cathode catalysts. In this work, the Mn-Co spinel on three different carbon supports [BP2000, Vulcan XC-72R, and multiwalled carbon nanotubes (MWCNTs)] has been successfully synthesized and demonstrated a high oxygen reduction reaction (ORR) activity with good ammonia tolerance. The structure and composition of the obtained Mn-Co-C catalysts were characterized by high-angle annular dark-field scanning transmission electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. All three catalysts exhibit superb ammonia tolerance, and Mn-Co-BP2000 demonstrates the highest ORR activity, even better than the commercial Pt-C in the presence of ammonia. When paired with the commercial PtIr-C anode, the Mn-Co-BP2000 cathode improved the peak power density of single cells from 100.1 mW cm-2 for the Pt-C cathode to 128.2 mW cm-2 under a 2 bar backpressure in both electrodes at 80 °C. All the results have manifested that Mn-Co-BP2000 is a good cathode catalyst for low-temperature AEM-DAFCs.

Effect of Reaction Time on the Synthesis and Sintering of Magnesium-Aluminium Spinel by Microwave Hydrothermal Synthesis

In this study, microwave hydrothermal synthesis of magnesium-aluminium spinel from pseudo-boehmite (AlOOH.nH2O) (n=0.62) and magnesium hydroxide (Mg(OH)2) for different reaction times is researched. X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) are used to find out how the reaction time affects the synthesis of magnesium aluminium spinel precursors. The superficial properties of magnesium aluminium spinel precursors are investigated with scanning electron microscopy (SEM). According to XRD analysis, magnesium hydroxide reacts with pseudo-boehmite to form magnesium aluminium hydroxide hydrate. The median diameter of the samples obtained at 200 min was 5.958 μm. The agglomeration phenomenon was very serious especially when the synthesis time is greater than 200 min. The sintered sample obtained at 150°C for 200 min had more dense structure and smaller average grain size. The average grain size of the sintered sample was 0.527 μm. The best reaction time for microwave isothermal synthesis and sintering of magnesium aluminium spinel is 200 min.

Research Progress in Synthesis of Spinel M (M=Mg, Sr, Ba) Aluminate Based Photocatalyst by Polyacrylamide Gel Method

Research Progress in Synthesis of Spinel M (M=Mg, Sr, Ba) Aluminate Based Photocatalyst by Polyacrylamide Gel Method

Formation of lithium-selective sorbent in nanoreactors of the support based on titanium dioxide

Nanocomposite sorbents, which consist of anatase (binder) and lithium-containing spinel (selective towards Li+ ions), where synthesized. Hydrated titanium dioxide was used as a matrix, where spinel was formed. Preliminarily it was shown that azeotropic drying affects the porous structure of titanium dioxide during its transformation from hydrogel to xerogel. The largest volume of mesopores has been found for the xerogel, which was dried with benzene. Mesopores perform a function of nanoreactors, where synthesis of Li-containing spinel occurs: their volume correlate with the amount of Li-containing spinel. Its composition is LiTi2O4 or Li4Ti5O12. These phases are formed at 500 and 600–700 °C respectively. The sample containing the largest amount of spinel demonstrates the largest sorption capacity towards Li+ ions (about 2 mmol g−1). The spinel nanoparticles are the selective constituents of the sorbents. Anatase performs a function of a binder. The sorbent of the optimal composition was used for multiple sorption–desorption. It is possible to increase the ratio of Li+ and Na+ ions in 1600 times comparing with that for sea water.

Investigation conditions of formation Co–Al double layered hydroxides

The process of formation of double layered hydroxides in the system Со2 + – Al3 + – SO4 2– – ОН- at the stoichiometric ratio of Al3 +/Сo2 + = 2 cations was studied by a complex method. The possibility of coprecipitation of cobalt and aluminum hydroxides, the optimal range of pH values for the production of precipitation, which are precursors of the synthesis of aluminocobalt spinel. X-ray diffraction analysis revealed the phase composition of the final product. Spectrophotometrically determined color characteristics of spinel.

Temperature Effect on the Topotatic Synthesis of Spinel MnCoO Nanoparticles for Efficient Oxygen Reduction Electrocatalyst

In this study, we demonstrated the temperature effect of our previously developed topotatic catalysis for the formation of Mn0.005Co2.995O4 (MnCoO) spinel nanoparticles. Topotatic catalysis induces spinel MnCoO nanoparticles through the redox reaction of the metal cation (Co2+ and Mn2+) on the Co(OH)2 nanosheet surface, acting as a growth template. This study particularly elucidates the temperature effect on spinel MnCoO nanoparticles' size, morphology, and crystallinity based on their electrocatalytic performance in an oxygen reduction reaction (ORR). We found that lower temperature produces an amorphous phase, whereas higher temperature induces a large aggregate. We obtained the monodispersed MnCoO nanocubes at approximately 90°C, exhibiting the best ORR performance with an electron‐transfer number of 3.86.

Slag resistant and refractory ceramic compositions in MgO – Al2O3 – SiO2 system on the base of local raw materials of Uzbekistan

Forsterite and spinel-corundum ceramic materials were obtained in the MgO-Al2O3-SiO2 system based on local raw materials of Uzbekistan - talc-magnesite of Zinelbulak deposit, kaolin of Angren deposit and inorganic additives (fused periclase PPE-87, electric fused corundum). The formations of various phases were studied using XRD and SEM-EDS. Study of chemical-mechanical properties of ceramic samples showed that spinel-corundum composition have density from 2520 to 2770 kg/m3, water absorption rate from 10.52 to 11.71%, open porosity from 27 to 31%, apparent density from 2420 to 2750 kg/m3, compressive strength from 100 to 120 MPa, characterized by increased refractoriness (it was 1750 °C for forsterite ceramic materials, for spinel-corundum more than 1800 °C) and slag resistance under metallurgy slags. The synthesis of spinel in optimal compositions occurs at 300 °C lower than the traditional sintering temperature of spinel products, which contributes to significant energy savings in the synthesis of highly refractory spinel-corundum materials.

Mechanochemical effect on synthesis and sintering behavior of MgAl2O4 spinel

This research work accomplishes the mechanochemical effect on synthesis and sintering behavior of MgAl2O4 spinel prepared by separate vibrating ball milling (VBM) and planetary micro-milling (PMM-P7) processes. The pure stoichiometric magnesium aluminate spinel (MgAl2O4) was produced from the precursors [Mg(OH)2 & AlOOH], and their densification at an optimum sintering profile. Non-gelation, soft agglomeration, and compressive stress induced by micro-milling in ethanol solvent facilitated the pure phase at low calcination temperature and confirmed through TEM. Eventually, the formation of nanoscale (25 nm) particles, ~98% densification, and grain size (38 μm) in atmospheric sintering are being achieved through planetary micro-milling. Critical discussion on the effect of planetary micro-milling is emphasized to understand the enhanced densification and optimum grain size that may expedite to development of other oxide particles and dense ceramics.