Spinel CoCr2O4 Research Articles

Investigation of High-Temperature Oxidation Behavior of Additive Manufactured CoCrMo Alloy for Mandrel Manufacturing.

The cyclic oxidation behavior of an additive manufactured CoCrMo alloy with 0.14 wt.% C was investigated at 914 °C for 32 cycles, each lasting 10 h, resulting in a total exposure time of 320 h. The oxidation rate was assessed for mass gain after finishing each 40 h oxidation cycle. It was experimentally determined that the oxidative process at 914 °C of this CoCrMo alloy follows a parabolic law, with the process being fast at the beginning and slowing down after the first 40 h. The microstructural analysis revealed that in the as-printed state, the phases developed were primarily the γ matrix and minor traces of ε phase. The oxidative process ensured an increase in the ε phase and precipitation of carbides which produced a 12% increase in the material's hardness after the first 40 h of exposure at 914 °C. The oxidation process led to the development of an oxide scale comprising a dense Cr2O3 layer and a porous layer of CoCr2O4 spinel, the latter spalling after the 240 h of exposure. Despite this spallation, the oxide scale continued to develop in the presence of O, Cr, and Co. The experimental analysis provided valuable insights regarding the material's behavior under prolonged exposure at high temperature in air, demonstrating its suitability as a candidate for additive manufactured mandrels used for bending metallic pipe fitting elbows.

In-situ crystallization of CoCr2O4 in tellurite glass with enhanced optical nonlinear limiting, photoluminescence, and magnetic properties: Influence of Co content

This article reports the in-situ growth of spinel CoCr2O4 nanocrystals (NC) in tellurite glass through tailoring the Co content by melt-quenching method. The microstructure, optical, and magnetic properties of NC/ glass systems were systematically studied using various techniques. Well-defined 30 nm crystallization of CoCr2O4 (space group of Fd3m) homogeneously distributed in the glassy matrix and the concurrent formation of cubic BiCoO3 (space group of P4mm) when the Co content exceeds 3%. The coexistence of multivalence and coordination states of Co and Cr significantly modified the glass structure with conversion of TeO4→TeO3, BO4→BO3, and CoO4→CoO6 units. Exceptional performance of the glass containing 5% Co-tuned CoCr2O4 was obtained, showcasing the decrease of Eg (2.09 eV), strong ferro-magnetization of 7.04 emu/g, large α3 (4.88×10−10 m/W) and good optical limiting property (threshhold of 1.31×1012 W/m2). Furthermore, the same glass showed excellent red emission between 650 and 800 nm under the excitation of 460 nm, with an increased lifetime (2.648 ms) and good stability of 90.7% within 25–300 °C. The emission mechanism was discussed. EPR analysis confirmed the active role and spin-states of magnetic Cr and Co ions, contributing synergistically to the improved optical and magnetic properties of the glasses.

Spinel Phase Engineering Boosted Visible-Light Photocatalytic Activity in Co1-xSrxCr2O4.

We synthesized Sr-doped spinel CoCr2O4 using the solution combustion method and characterized the structure, morphology, chemical state, and photocatalytic properties through different techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and electrochemical impedance spectroscopy (EIS). 30-50 nm cuboid CoCr2O4 nanocrystals with Sr doping levels ranging from 0 to 0.6% were obtained; the increasing Sr doping deformed the coordination number of Co and Cr, transitioning to octahedral and tetrahedral units, inducing the phase transition from spinel to inverse spinel at 0.6% Sr content. This modification enhanced optical absorption, reduced the energy band gap, increased photoluminescence intensity, and maintained a high-spin state with oxygen vacancies. 0.6% Sr-doped CoCr2O4 demonstrated the highest photocatalytic efficiency at 93%. The XRD structure and photocatalytic activity remained at 87% over 7 cycles after 14 h. Employing degradation pathways and Mott-Schottky curves elucidated the enhancement mechanism.

Designing of Z‐Scheme MgFe2O4/Fe2O3 Coupled CoCr2O4 Heterojunction with High Photocatalytic Activity for the Removal of Tetracycline Hydrochloride in Wastewater

AbstractA simple solution combustion method is used to synthesize spinel type MgFe2O4 (MFO) and CoCr2O4 (CCO) oxides, which are combined with the mechanical mixing method to construct a Z‐scheme MFO/wt%CCO heterojunction, which effectively degraded tetracycline hydrochloride (TC) under simulated sunlight irradiation. Various characterization techniques are used to confirm the phase structure, composition, near‐spherical morphology, ferromagnetic behavior, optical properties, and photocatalytic activity of Z‐scheme MFO/wt%CCO heterojunction. A variety of environmental experimental parameters confirmed that when the optimal initial TC concentration is 50 mg L−1, the catalyst content is 1 g L−1, and pH 13, the degradation percentage of TC by the MFO/75%CCO composites reached 89%. Active species verification experiments showed that the hole (h+), hydroxyl radical (•OH), and superoxide radical (•O2 −) are the main active species in photocatalytic reactions. Based on mass spectrometry, toxicity analysis, and energy band theory, the degradation pathway, toxicity, and photocatalytic mechanism of MFO/75%CCO composites for the degradation of TC are discussed in detail.

Morphologically controlled preparation of CoCr2O4 nanomaterials for high-performance asymmetric supercapacitor application

CoCr2O4 nanoparticles (NPs) with four different and unique morphologies were synthesized using various surfactants of PVP, PEG, and CTAB and employed as electrodes for high-performance double-layer supercapacitors. The hydrothermal process required to make the CoCr2O4 spinel structure of the nanospheres allows for precise control of particle size, and quick and uniform heating. Electrochemical analysis proves that CoCr2O4 material exhibits EDLC behaviour. In three-electrode cells of cobalt chromite as the electrode material for EDLC and operating in 1 M Na2SO4 electrolyte, CTAB surfactant-induced material exhibits excellent specific capacitance up to 883 F g−1 at a scan rate of 5 mV s−1 and excellent cyclic stability of 92 % of initial capacitance after 5000 cycles. These results are due to the material's increased surface area, surface roughness, and more active sites for ion adsorption. The asymmetric device offers a high energy density of 26.33 W h kg−1 with a power density of 400 W kg−1 and cyclic stability of 91.5 % after 5000 charge/discharge cycles. These outstanding electrochemical properties encourage the development of the possibility of using CoCr2O4 nanoparticles introduced by the CTAB template for advanced energy storage applications.

CoCr2O4/Graphene modified glass carbon electrode for highly dual-sensing detection of hydrogen peroxide and glucose

The development of a non-enzymatic electrochemical sensor possessing well dual-sensing to H2O2 and glucose remains challenging due to less report. Herein, spinel CoCr2O4 nanoparticles with small size were synthesized by sol–gel reaction, which were then simply mixed with commercial graphene under ultrasonic to obtain uniformly dispersed CoCr2O4/Graphene composite. They were deposited onto the surface of bare glassy carbon electrode (GCE) through a common drop-coating method. The CoCr2O4/Graphene/GCE sensor firstly achieves highly dual-sensing to H2O2 and glucose in 0.1 M NaOH solution. At 0.4 and 0.55 V, its sensitivities to H2O2 and glucose can separately reach up to 1168.6 and 1722.5 μA mM−1 cm−2, and the corresponding detection limits are as low as 18 nM and 12 nM. These key indexes are the best among reported dual-functional spinel oxide-based electrodes. This excellent electrochemical sensing ability stems from its large electrode active area, good conductivity, and the synergism between graphene and CoCr2O4 nanoparticles with mixed redox couplings, which provides an efficient platform for dual-sensing detection. In addition, the modified electrode can accurately determine glucose in human tears, rat serum and orange juice, as well as H2O2 in milk whey, mouthwash and disinfectant, thus predicting its good application prospects.

Comparative studies on oxidation behaviour of cobalt-based D-gun coatings on boiler steel

The protection system against material degradation at elevated temperatures is gaining technological importance. Three cobalt-based coatings were developed on SAE213-T91 boiler steel using the detonation gun method. The oxidation performance of all the specimens was examined for 50 cycles of 1 h heating at 900 °C in a thermal cyclic furnace and 20 min cooling at 25 °C outside the furnace. All the oxidised samples were investigated through SEM/X-ray mapping and an X-ray diffraction analyser. All the specimens obeyed the parabolic rate law of oxidation approximately. The oxidation resistance of Stellite 6 coating was found to be superior among all coated and uncoated specimens due to the growth of protective oxide Cr2O3 and CoCr2O4 spinel in it. The development of Ni, Cr and Co oxides in Stellite 21 coating resulted into its slow oxidation rate, whereas the growth of the non-protective WO3 and CoWO4 phases in WC-Co coating caused its rapid oxidation.

Mechanical milling/alloying, characterization and phase formation prediction of Al0.1–0.5(Mn)CoCrCuFeNi-HEA powder feedstocks for cold spray deposition processing

In the present work the synthesis of multicomponent nanocrystalline Al0.1- 0.5(Mn)CoCrFeNi HEA powder feedstocks by mechanical alloying (MA) through high energy ball milling to produce HEA coatings with cold spraying were studied. Pure (>99.5) elemental powders of Al (Mn), Co, Cr, Cu, Fe & Ni were mixed in predetermined ratios and mechanically alloyed under Ar gas in a Planetary Ball Mill. MA HEA powder feedstocks were characterized by optical microscopy, SEM+EDAX, XRD & XPS to determine powder particle size, shape & distribution, particle surface condition, chemical composition, crystal & phase structures & microstructures. MA-processed Al-HEA powder feedstocks exhibited tri-modal particle size distribution (PSD) while Mn-HEA had four distinct PSD modes. Fine size fraction of the MA- HEA powders contained A2/B2 (BCC) harder phases with lattice parameters of 2.8831 and .2.8690 Å, respectively and coarse size fraction contained (ductile) softer A1 phase/Cu-rich regions combined (FCC) having a lattice parameter of 3.6181 Å. The ratio of the phases varied depending on the Al and Mn contents in the powder. For higher aluminium contents, there was more disordered A2/B2 phases and less disordered A1 phase in Al0.1–0.5 HEA powder feedstocks. A1 phase contained Fe, Cr, Co and Ni; A2 phase contained Fe, Cr; and B2 phase contained Al, Ni elements in Al0.1–0.5 HEA powder feedstocks. There were passive surface oxide films on the rough surfaces of MA HEA powder feedstocks consisting of a main mixture of surface oxides such as Al2O3, MnO, Cr2O3, Mn2O3, and minor oxides such as CuO, Fe2O3, NiO, Fe3O4, and a few CoCr2O4 spinel oxide. Dual FCC-dual BCC phase prediction of thermodynamic stable phase formation criteria reported in the literature on MA-HEA powder feedstocks were consistent with the experimental results of the present study.

Hot Corrosion Behavior of Plasma-Sprayed WC-CoCr Coatings on AISI 316L Steel Substrate in Na2SO4-25% NaCl Salt Environment

This study investigates the hot corrosion resistance characteristics of plasma-sprayed WC-CoCr coatings deposited on AISI 316L stainless steel. Coated and uncoated samples were exposed to a fused Na2SO4-25%NaCl salt deposit at 700 °C in cyclic conditions for fifty thermal cycles. The corrosion kinetics were determined using a thermogravimetric method. To determine the hot corrosion rate, weight-change measurements were taken after every cycle. X-ray diffraction, energy dispersive spectroscopy, and scanning electron microscopy were performed on samples to examine the hot corrosion characteristics. With a fused salt deposit at 700 °C, the uncoated AISI 316L steel substrate samples experienced faster high-temperature oxidation as compared to coated samples. It was noticed that the uncoated steel substrate gained a little weight during the first few cycles, afterwards as the number of thermal cycles increased, the weight gain followed a linear kinetics. The WC-CoCr coating reduced the weight gain of steel substrate by about 75% in a corrosive salt environment. The plasma-sprayed WC-CoCr coatings had adhesion strength and microhardness of 10.8 ± 2.4 MPa and 410 ± 25 HV0.5, respectively. The hot corrosion-affected coatings displayed slow-scaling kinetics. The oxides of the coatings, formed at the surface were rich in chromium and tungsten. These oxides helped in providing hot corrosion resistance in the corrosive environment as they worked as obstacles to the penetration/diffusion of corrosive elements through coatings. The higher content of tungsten inside the coating promoted WO3 formation, which improved resistance to corrosion at elevated temperatures. Chromium in the coating caused the formation of spinel CoCr2O4 and Cr2O3 the spinel CoCr2O4 that emerged as an intermediate phase also contributes to the maintenance of corrosion resistance. Some oxides such as Fe2O3, FeCr2O4, and CoSO4 were found. Apart from that some traces of Na were also found.

Low-cost flame synthesized La2/3Cu3Ti4O12 electro-ceramic and extensive investigation on electrical, impedance, modulus, and optical properties

An environmentally-friendly synthesis route and low-cost starting materials are more appropriate for the production of ceramic materials at the industry level. With this concern we prepared the La2/3Cu3Ti4O12(LCTO), which is isostructural of CaCu3Ti4O12 (CCTO), using the low-cost TiO2 instead of a high-cost of titanium source (titanium isopropoxide or titanium chloride) using a low-cost wet-chemical route. Although, there are lots of synthetic methods reported for LCTO fabrication in terms of duration, cheap reagents, energy consumption, feasibility, etc. The present method is far better than the others. The prepared ceramic samples were sintered at 1050 °C/12 h and studied their structural, morphology and impedance, and modulus studies for further confirmation. The prepared LCTO ceramic shows the pure phase with the cubic type of morphology. The homogenous distribution of all the elements was observed through dispersive X-ray analysis. X-ray photoelectron spectroscopy studies revels that La is in +3 oxidation state, Cu is in a +2 oxidation state, and Ti is multiple (+3 and + 4) oxidation state. The LCTO ceramic displayed the very high dielectric constant (∼3852) and dielectric loss (0.322), at 1 kHz and at room temperature. Calculated the activation energy using the impedance and modulus data and it shows the superior to that of CCTO ceramic synthesized by the same method. The prepared samples exhibited Debye-type relaxation, which is evoked from the impedance and modulus studies. The calculated optical energy bandgap of LCTO (2.06 eV) is found to be lesser than that of the well-known structure of perovskites (BaTiO3 (3.28 eV), PbTiO3 (3.18 eV), LiNbO3 (3.78 eV) and BiFeO3 (2.67 eV) as well as structure of spinel CoCr2O4 (3.10 eV) and LuFe2O4 (2.18 eV)) materials.

Low-temperature gas-phase toluene catalytic combustion over modified CoCr2O4 spinel catalysts: Effect of Co/Cr content and calcination temperature

Un-supported spinel-type cobalt chromite catalysts were synthetized by propionic acid-mediated sol-gel method and tested for toluene oxidation. The influence of the Co and Cr content and the preparation conditions on physico-chemical, surface and catalytic properties for this reaction has been for the first time evaluated. Co-rich CoCr2O4 was the most active catalyst, likely due to the formation of a single CoCr2O4 spinel phase, a favorable surface composition and higher low-temperature reducibility. Besides, the increase of the calcination temperature, despite worsening textural properties, also has a promoting effect on the catalytic activity by preserving a suitable reducibility and further enhancing the surface properties. Surface Cr6+ ions and adsorbed oxygens (Oads), which are more abundant in the most efficient catalyst (Co-rich catalyst calcined at 685 °C), seem to play an important role on toluene oxidation reaction. These findings may open potential strategies in the development of efficient and economically competitive catalysts for elimination of VOCs like toluene.

Controlled preparation of spinel CoCr2O4 nanocrystals with variable proportions of mixed redox couplings for enhanced sensing to hydrogen peroxide

Chromium-based spinels with multiple mixed valence states have been considered as promising electrocatalysts. However, they are rarely reported as electrochemical sensors. Herein, spinel CoCr2O4 nanocrystals with mixed redox couplings were controllably synthesized through a simple sol-gel method followed by air calcination at 500 °C and 600 °C. The X-ray photoelectron spectrum analyses reveal that CoCr2O4-500 and CoCr2O4-600 products possess different surface ratios of Co3+/Co2+ and Cr3+/Cr2+. Meanwhile, non-enzymatic H2O2 electrochemical sensors were successfully fabricated by drop-coating the aforementioned nanomaterials onto the surface of bare glassy carbon electrode (GCE). Amongst, CoCr2O4-500/GCE shows high sensitivity (1016 μA mM-1 cm-2), low detection limit (150 nM) and wide detection range to H2O2 in 0.1 M NaOH solution. These important indicators are better than those of CoCr2O4-600/GCE. It is also the first time to achieve highly sensitive detection of H2O2 by pure chromite spinels so far. Such excellent electrochemical sensing performance stems from the synergistic effect of its large apparent electrode area, high electrical conductivity and proper surface ratio of mixed redox couplings for Co3+/2+/Cr3+/2+. Moreover, it also exhibits good selectivity, stability and recovery rate to trace H2O2 in milk whey, mouthwash and contact lens cleaning solution.

Crystal evolution of nano-sized CoCr2O4 synthesized by a modified sol–gel method

The present study provides a comprehensive assessment of the synthesis, crystal evolution, and degree of inversion of the spinel CoCr2O4 (i.e., cochromite) by a modified sol–gel method using propylene oxide and ultrasonication. Ultrasonic assistance promotes the dissociation and dispersibility of Co2+ and Cr3+ precursors, contributing to the hydrolysis reaction to form hydrated ions. Propylene oxide serves as a proton scavenger to provide the conditions needed for homogeneous gelation. Heat treatments at different temperatures (400, 550, and 700 °C) for different durations (1, 4, and 8 h) have been applied to follow the crystal evolution and the inversion of the spinel system. The formation of CoCr2O4 particles was observed at approximately 400 °C. An increase in calcination temperature induced particle size growth (from 12 to 42 nm) and sintering effects. A significant decrease in the specific surface area (from 144 to 33 m2 g−1) was observed with changes in the lattice parameter (8.304–8.334 Å). Raman, XPS, XRD, and Rietveld analyses indicated the presence of a pure cochromite phase. The Bertaut method has been applied to monitor the inversion process of CoCr2O4 during post-synthesis heat treatment. The spinel conformation became a regular type beyond 700 °C, whereas a fully inverted structure was obtained at lower temperatures. The modified sol–gel method may be convenient for large-scale production to synthesize other spinel-type compounds.

Morphology-Dependent Electrocatalytic Behavior of Cobalt Chromite toward the Oxygen Evolution Reaction in Acidic and Alkaline Medium.

Exploiting an affordable, durable, and high-performance electrocatalyst for the oxygen evolution reaction (OER) under lower pH condition (acidic) is highly challengeable and much attractive toward the hydrogen-based energy technologies. A spinel CoCr2O4 is observed as a potential noble-metal-free candidate for OER in alkaline medium. The presence of Cr further leads to electronic structure modulation of Co3O4 and thereby greatly increases the corrosive resistance toward OER in acidic environment. Herein, a typical CoCr2O4 with three different morphologies was synthesized for the very first time and employed as an electrocatalyst for OER in alkaline (1 M KOH) and acidic (0.5 M H2SO4) medium. Moreover, different morphologies display a different intrinsic exposed active site and thereby display different electrocatalytic activities. Likewise, the CoCr2O4 Mic (synthesized by the microwave heating method) displays a higher catalytic activity toward OER and delivers a low overpotential of 293 and 290 mV to attain 10 mA/cm2 current density and smaller Tafel slope values of 40 and 151 mV/dec, respectively, in alkaline and acidic environment than the synthesized CoCr2O4 Wet (wet-chemically synthesized) and CoCr2O4 Hyd (hydrothermally synthesized). Moreover, CoCr2O4 Mic exhibits a long-term durability of 24 h (1 M KOH) and 10.5 h (0.5 M H2SO4). The optimized Co-O bond energy in OER condition makes the CoCr2O4 Mic superior than the CoCr2O4 Hyd and CoCr2O4 Wet. Moreover, the substitution of Cr induces the electron delocalization around the Co active species and thereby, positive shifting of the redox potential leads to providing an optimal binding energy for OER intermediates. Also, interestingly, this work represents a catalytic activity trend by a simple experimental result without any complex theoretical calculation. The morphology-dependent electrocatalytic activity obtained in this work will provide a new strategy in the field of electrochemical conversion and energy storage application.

The Effect of Ni2+ Ions Substitution on Structural, Morphological, and Optical Properties in CoCr2O4 Matrix as Pigments in Ceramic Glazes.

The structural, morphological, and optical properties of Ni2+ ions substitution in CoCr2O4 matrix as ceramic pigments were investigated. The thermal decomposition of the dried gel was performed aiming to understand the mass changes during annealing. The X-ray diffraction (XRD) studies reveal a spinel-type Face-Centered Cubic structure and a secondary Cr2O3 phase when x ≤ 0.75 and a Body-Centered Tetragonal structure when x = 1. Fourier Transform Infrared Spectroscopy (FT-IR) indicated two strong absorption bands corresponding to the metal-oxygen stretching from tetrahedral and octahedral sites, characteristic of spinel structure. Ultraviolet-Visible (UV-Vis) spectra exhibited the electronic transitions of the Cr2+ Cr3+ and Ni2+ ions. From the UV-Vis data, the CIE color coordinates, (x, y) of the pigments were evaluated. The morphology was examined by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) showing the agglomeration behavior of the particles. The stability, coloring properties and potential ceramic applications of studied pigments were tested by their incorporation in matte and glossy tile glazes followed by the application of obtained glazes on ceramic tiles. This study highlights the change in pigment color (from turquoise to a yellowish green) with Ni2+ ions substitution in the CoCr2O4 spinel matrix.

Fabrication of ternary nano-heterojunction via hierarchical deposition of α-Fe2O3 and β-La2S3 on cubic CoCr2O4 for enhanced photodegradation of doxycycline

The current study offers the design of a novel photocatalyst for the effective removal of pharmaceuticals wherein the heterojunction was constructed with the objective of capturing maximum solar spectrum and to ensure effective separation of photogenerated charge carriers. The nano-heterojunction was fabricated through ultrasonication-assisted co-precipitation method by the hierarchical deposition of α-Fe2O3 and β-La2S3 on cubic CoCr2O4 spinel. The fabricated nanomaterials were extensively characterized by using XRD, Raman, FTIR, XPS, SEM, TEM, EDAX, PL, EIS, BET, and DRS. The photoluminescence and EIS analysis revealed the mitigated charge carrier recombination in CoCr2O4/α-Fe2O3/β-La2S3 (CFL) that resulted in superior photodegradation of doxycycline (DOX) (92.83 %) under visible light irradiation. Mineralization percentage of 92.5 % was affirmed by TOC analysis. Further, the influence of pH, ions, concentration of DOX and CFL dosage on the photodegradation process was studied. The active participation of the reactive species involved in the reaction were identified by scavenging assay and ESR. Finally, a possible photocatalytic mechanism of CFL for the degradation of DOX with underlying pathway is proposed with the help of GC–MS/MS analysis. The study highlights the great promise of CFL photocatalyst as well as the potential of n-n-p heterojunction for appliances in the photodegradation of organic pollutants.

Insight into the design and construction of Cr substituted Co-based columnar activated coke catalysts for effective and reliable removal of methylbenzene and Hg0 concurrently

An array of CoCr oxides co-modified activated cokes pretreated with HNO3 (XCoyCr1-y/ACs) were synthesized and evaluated for simultaneously effective and credible elimination of methylbenzene (MB) and Hg0. BET, SEM, TEM, EDX, XRD, H2-TPR, in situ DRIFTS and XPS were adopted for exploring the physicochemical characteristics and reaction mechanisms of aforesaid samples. H2-TPR result showed the Cr-doped Co-Cr catalysts excellent reducibility in view of the synergistic effect between CoOx and CrOx. Especially, 6 %Co0.5Cr0.5/AC obtained outstanding performance and prominent stability for MB and Hg0 removal, and it behaved the optimal performance of MB (96.1 %) and Hg0 (88.3 %) at 240 ℃. It could be explained by that the formation of CoCr2O4 spinel entailed more uniform distribution of active components, abundant lattice defects and even the redox cycle of Cr6++Co2+↔Cr3++Co3+, which spawned adequate Co3+ species and active oxygen species. The interaction between MB removal and Hg0 removal was estimated and the presence of Hg0 barely affected MB removal, whereas the existence of MB manifested a distinctly suppressive influence on Hg0 removal, suggesting that MB removal might prevail over Hg0 removal. Meanwhile, the rivalry between MB and Hg0 progressively shifted from adsorption sites to active oxygen species with time. Moreover, the influences of O2, NO, SO2 and H2O on MB and Hg0 simultaneous removal were systematically appraised. Notably, 6 %Co0.5Cr0.5/AC exerted remarkable resistance to SO2 and H2O. Combined with characterizations and experiments, the pathway for the simultaneous removal of MB and Hg0 via adsorption and catalytic oxidation on 6 %Co0.5Cr0.5/AC was summarized. This work could deliver references to the design of advanced catalysts for simultaneous removal of MB and Hg0.

Synthesis and Analysis of Zn-Substituted CoCr2O4 Spinel Oxide

Synthesis and Analysis of Zn-Substituted CoCr2O4 Spinel Oxide

Facile Synthesis of Spinel CoCr2O4 and Its Nanocomposite with ZrO2: Employing in Photo‐catalytic Decolorization of Fe (II)-(luminol-Tyrosine) Complex.

In this project, the deep green power from spinel cobalt chromite (CoCr2O4) nano-crystals carried out using the co-precipitation method and then calcinated at 600 oC for 4 hours. This produced nano-crystal (spinel CoCr2O4) fabricated using the ultrasonic technique to link it with zirconium dioxide (ZrO2) in ratios 1:2 and 1:3, respectively. The X-ray diffraction (XRD), scan electron microscopy (SEM), and energy-dispersive X-rays (EDX), as well as ultraviolet-visible spectrophotometry used to describe the characterizations of prepared materials. The XRD analysis demonstrated that the spinel CoCr2O4 synthesis and their composites were found to be nanoparticles. XRD spectra indicated that the spinel CoCr2O4 is successfully loaded on ZrO2, because, the 2θ of ZrO2 is shifted toward a high 2θ value after spinel CoCr2O4 loaded. This case is attituded to the tiny Co2+ and Cr3+ ions combined with Zr4+ ‌in crystal lattice. The SEM images and EDX spectra of these obtained nanomaterials were found to be spherical agglomerations with an enhanced degree of surface roughness after surface fabrication. On the other side, the bandgap of spinel CoCr2O4 nanocrystals elevated from 3.2 to 4.8 eV with increasing the ZrO2 dose. Under UV-A light, the photocatalytic decolorization efficiency of Fe (II)-(luminol-Tyrosine) complex utilizing spinel CoCr2O4 nanocrystals was tested, and it increases from 17.57 % to 30.67% and 41.97% when its nanocomposite was used in 1:2 and 1:3 ratios, respectively. The elevated efficiency after modified the spinel CoCr2O4 surface with ZrO2 as nanocomposite, due to increasing the acidity of the spinel CoCr2O4 surface that enhances the adsorption of hydroxyl on its surface then generality of the hydroxyl radical, and reducing the recombination. The photoreaction using spinel CoCr2O4 nanocrystals, ZrO2, and their composites were followed pseudo-first-order kinetics depended on the complex concentration.

Preparation and characterisation of green nano-sized ceramic pigments with the spinel structure AB2O4 (A = Co, Ni and B = Cr, Al)

Inorganic pigments based on AB2O4 (A = Co, Ni; B = Cr, Al) spinel structures with green colour were successfully synthesised by the polymeric route. The effect of the substitution of trivalent and divalent cations on the structural, optical and morphological properties of the pigments was investigated. The synthesised nanopowders were examined using thermogravimetry-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller analysis (BET), UV–vis diffuse reflectance measurements, and CIEL*a*b* colorimetric analyses. The results show that the CoCr2O4 spinel and the spinels substituted by nickel and aluminium cations were obtained with a single phase after heat treatment at 900 °C. The produced powders present shades of the green colour with improvement in morphology for the substituted samples. The Ni0·5Co0·5CrAlO4 nanoparticles consisted of grains of quasi-spherical shape with sizes between 50 and 75 nm. This powder was used in small quantities with glazes for colouring tests on the surfaces of ceramic substrates.