Amount Of CoO Research Articles

Preparation and characterization of CoO-doped and Li2O-stabilized Na-β″-Al2O3 solid electrolyte via a solid-state reaction method

The Na-β"-Al2O3 solid electrolyte ceramic material doped with CoO was synthesized via a solid-state reaction method, which began with α-Al2O3 and Na2CO3 as the raw materials and involved a low-cost burying process. The effects of different contents of CoO on the properties of the material were investigated as Li2CO3 was added as a stabilizer. The CoO amount in the initial materials is the key to obtaining quality products. Therefore, samples sintered from precursors containing different amounts of CoO were systematically characterized using thermogravimetry/differential thermal analysis (TG-DTA), X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM). Additionally, the relative density and electrical properties of the prepared samples were also measured by the Archimedes method and AC impedance spectroscopy. The Na-β"-Al2O3 solid electrolyte with an optimal amount of CoO of 1 wt% exhibited a uniform and dense microstructure with a relative density of as much as 97.98% (3.194 g cm⁻3) of the theoretical density. However, excess 1.25 wt% CoO doping can cause the sample too loose and make pores between the grains larger. This deteriorates the ionic conductivity of the material. In addition, the sample with the appropriate amount of CoO exhibited an ionic conductivity of up to 0.061 S cm−1 at 300 °C with a corresponding activation energy of 0.179 eV.

Preparation of new biosorbents based on poly-γ-glutamic acid and its adsorption of heavy metal ions

In this paper, adsorption effects and characteristics of heavy metal ions by poly-γ-glutamic acid (γ-PGA) and its two complexes (γ-PGA/Gelatin and γ-PGA/Fe3O4) were studied. The adsorption capacity of Cu2+, Pb2+ and Cd2+ with initial concentration of 100 mg/L by unmodified γ-PGA is 1158 mg/g, 1129 mg/g and 301 mg/g, respectively. However, γ-PGA is easy to dissolve in water, which is not conducive to the treatment of heavy metal wastewater under flow state, neither to its reuse. The γ-PGA/Gelatin was prepared by crosslinking γ-PGA with gelatin to enhance γ-PGA’s mechanical strength and adsorption stability. Moreover, Fe3O4 magnetic particles are also the ideal carrier of γ-PGA, which not only improves the strength performance of γ-PGA but also enhances the repetition rate of γ-PGA. The γ-PGA/Fe3O4 magnetic particles were prepared by co-precipitation. The scanning electron microscopy and infrared spectroscopy showed that γ-PGA and Fe3O4 were successfully synthesized, and the magnetic particles showed good paramagnetism. The data shows that the adsorption capacity of regenerated γ-PGA/Fe3O4 to Pb2+ and Cd2+ can reach more than 70% of the first one. The comparison of FTIR spectra shows that the amount of COO− after reaction is greatly reduced, indicating that the -COOH in γ-PGA plays a major role in adsorption process. What’s more, the natural resolution of adsorbent γ-PGA, γ-PGA/gelatin and γ-PGA/Fe3O4 were 11.3%, 0.7% and 0 respectively 24 hours after adsorption for Pb2+.

Mullite–Cobalt (II, III) Oxide System: Preparation of Ceramic Pigment Using Recycling of Fly Ash

The present work depends on recycling of fly ash by preparation of stoichiometric mullite containing various amounts of Co3O4; 0, 5, 10, 15 wt.% to obtain pigment ceramic materials. The mixtures were sintered at different temperatures; 1250, 1350, 1400, 1450, 1500 and 1550 ∘C to follow the phase compositions, structure, physical, mechanical, electrical, magnetic properties and the color behaviors. The results indicate that the sintering at 1250 ∘C is the optimum condition for the formation of the blue pigment ceramic materials. The sintering from 1250 to 1500 ∘C shows increase in the bulk density and the strength properties up to 15 wt.% Co3O4. The incorporation of cobalt (II, III) oxide into the mullite system enhances the electrical and magnetic properties to be used as ferromagnetic materials.

Optical character inquest of cobalt containing fluoroborate glass

Glass samples of Fluoroborate glasses of composition 80% B2O3-15%-NaF-5%CaF2 containing different amounts of CoO (0.2, 2, 3%wt) were successfully prepared by melt annealing technique. The samples were characterized using UV-VIS-NIR and FTIR spectrometry. The results showed that the optical properties of the samples are dependent on the Co content within the glass matrix. The optical absorption and transmittance spectra confirmed the incorporation of the CoO in the glass matrix. CoO doped samples showed a blocking region within the visible area which belongs to the tetrahedral Co ions and a transmittance region in the UV. Increasing the CoO content leads to increasing the FWHM of the blocking band and decreasing in the FWHM of the transmittance band. The FTIR spectra showed the characteristics absorption peaks of the triangular and tetrahedral groups in the glass matrix. The existence of CoO leads to resolving and enhancing the bands in the glass samples. The experimental results and the calculated optical parameters for the glass samples recommend them as a promising candidate for band pass filter applications.

Co3O4 nanoparticles-loaded BiOCl nanoplates with the dominant {001} facets: efficient photodegradation of organic dyes under visible light

In this work, a facile method was developed to improve the photocatalytic efficiency of bismuth oxychloride (BiOCl) with the dominant {001} facets and cobalt oxide (Co3O4) through creating a heterojunction between them. The heterostructured Co3O4/BiOCl photocatalyst with different amounts of Co3O4 (0, 0.4, 0.8, 1.2, and 1.6wt%) was successfully synthesized by a simple chemical co-precipitation method. The as-synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy (UV-vis), Brunauer–Emmett–Teller (BET), and photoluminescence spectroscopy (PL). Due to the formation of the heterojunction, which grows along the [001] crystallographic direction of BiOCl, the effectual separation of electron-hole pairs results in the enhanced photocatalytic activity of the Co3O4/BiOCl system. The 0.8wt% Co3O4/BiOCl exhibits the highest photocatalytic activity as compared with other samples (0, 0.4, 1.2, and 1.6wt% Co3O4/BiOCl) because of the enhanced flow of charge carriers through the heterojunction, and light absorbance. The photodegradation mechanisms of Rhodamine B (RhB) and methyl orange (MO) over the heterostructured Co3O4/BiOCl photocatalyst under visible light was also studied, and the enhanced photocatalytic activity could be attributed to the improved separation of photo-induced electron-hole pairs by creating the heterojunction along the [001] crystallographic direction. According to the results obtained from the recyclability experiments, the heterostructured Co3O4/BiOCl photocatalyst could be easily recycled without decreasing photocatalytic activity due to its high photostability.

Electrocapacitive performance of graphene/Co3O4 hybrid material prepared by a nanosheet assembly route

Graphite oxide/Co(OH)2 layered composites are prepared by nanosheet assembling between the exfoliated Co(OH)2 and graphene oxide (GO) nanosheets. The subsequent thermal treatment of GO/Co(OH)2 composites in controlled atmospheres converts GO into reduced graphene oxide (RGO) and Co(OH)2 into Co3O4. The RGO/Co3O4 hybrid nanocomposites with different amounts of Co3O4 are thoroughly characterized, and their electrochemical properties as supercapacitor electrode are systematically investigated by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy in the KOH electrolyte. In particularly, the RGO/Co3O4 hybrid composite with 94.3 wt% Co3O4 exhibits a high specific capacitance of 331 F g−1 at the current density of 5 A g−1, and shows the excellent electrochemical cycle stability with capacitance retention over 122% after 5000 continuous charge–discharge cycles. These outstanding capacitive performances make the RGO/Co3O4 hybrid nanocomposites one of the promising candidates for the supercapacitor electrode.

BSA adsorption on aliphatic and aromatic acid SAMs: Investigating the effect of residual surface charge and sublayer nature

In this work, the influence of surface charge and layer rigidity on Bovin Serum Albumin (BSA) adsorption has been investigated. To this aim, Self Assembled Monolayers (SAMs) bearing terminal COOH or COO− groups were built on gold surfaces. The rigidity of the acid terminated SAMs was modified using either an aliphatic, mercaptoundecanoic acid (MUA), or an aromatic, mercaptobenzoic acid (MBA) thiol. X-Ray Photoelectron Spectroscopy (XPS), Polarization Modulation Reflection Absorption Infrared Spectroscopy (PM-RAIRS) and contact angle measurements, were used to deeply characterize the so-built layers. The surface charge was successfully modified by varying the pH of the rinsing solution. Indeed, COOH were the dominating species upon rinsing at pH 2 and COO− species dominated upon rinsing at pH 11. Rinsing at an intermediate pH, 5.5, led to the coexistence of both carboxylic and carboxylate moieties. The hydrophilic character of the surface was also found to depend on the rinsing pH, with a minimum after rinsing at intermediate pH. Using aromatic or aliphatic thiols did not affect the speciation but led to considerable differences in the hydrophilic character of these surfaces. Eventually, the adsorption of BSA on the acidic layers was investigated using PM-RAIRS. The results showed interesting differences between the charged layers. Thus, for both MUA and MBA -based SAMs, the amount of adsorbed proteins decreased when the amount of COO− on the surface increased. Interestingly, these effects were totally annihilated when the adsorption was carried out in PBS buffer. Moreover, for similar surface charges, the aromatic layers were able to bind higher amounts of proteins than the aliphatic ones. This work points out the key role of both surface charge and rigidity on protein adsorption. The influence of additional parameters, such as hydrophilicity and SAMs’ rigidity is also established.

Co3O4-KIT-6 composite catalysts: synthesis, characterization, and application in catalytic decomposition of N2O

Two sets of Co3O4-KIT-6 composite catalysts were prepared. To prepare the first set of catalysts, mesoporous silica (KIT-6) samples with different pore sizes were obtained by changing the hydrothermal temperature during synthesis, and the same amount of Co3O4 (10 %) was loaded by impregnation. In the second set, KIT-6 prepared by hydrothermal synthesis at 100 °C was used to load different amounts of Co3O4 (up to 50 %). These materials were characterized by low-angle and wide-angle X-ray diffraction, transmission electron microscopy (TEM), and N2 adsorption–desorption. The TEM results showed that Co3O4 species do not disperse on the inner pores of KIT-6 homogeneously, nor do they form separate Co3O4 particles detached from KIT-6. Rather, Co3O4 crystals grow into the KIT-6 matrix, forming Co3O4-KIT-6 composite grains in some parts of the KIT-6 matrix, whereas there are empty mesoporous silica channels in other parts. The influences of textural properties of KIT-6 support and the loading of Co3O4 on the catalytic activity in N2O decomposition were studied. It was found that the textural properties (e.g., pore size, surface area) of KIT-6 have little effect on the catalytic activity, whereas the amount of Co3O4 directly correlates with the catalytic activity.

Air-Oxidation Behavior of a [(Co50Cr15Mo14C15B6)97.5Er2.5]93Fe7 Bulk-Metallic Glass at 873 K to 973 K (600 °C to 700 °C)

The oxidation behavior of a [(Co50Cr15Mo14C15B6)97.5Er2.5]93Fe7 bulk-metallic glass (Co7-BMG) was studied over the temperature range of 873 K to 973 K (600 °C to 700 °C) in dry air. The oxidation kinetics of the Co7-BMG generally followed the parabolic-rate law, as its oxidation rates increased with temperature. The scaling rate of the Co7-BMG was significantly lower than that of pure Co, which indicates a better oxidation resistance for the amorphous alloy. The scales formed on the Co7-BMG consisted mostly of CoMoO4 and Co3O4, as well as minor amounts of CoO, Cr2O3, and uncorroded Co3B. The formation of CoMoO4 and Cr2O3 is responsible for the lower oxidation rates of the glassy alloy with respect to those of pure Co. In addition, the presence of Co3B further indicated that the crystallization of the amorphous substrate during the oxidation was taken place.

Electrical and transport properties of nickel manganite obtained by Hall effect measurements

Intrinsic resistivity and carrier transport parameters of sintered nickel manganite samples (NTC thermistor grade) were determined using a Hall effect measurement system based on the van der Pauw method. Powder mixtures composed of MnO, NiO and with small amounts of CoO and Fe2O3 were free surface energy activated by milling in an ultra fast planetary mill for 5, 15, 30, 45 and 60 min. The powders were uniaxially pressed with 196 MPa into discs and sintered at 1200 °C for 60 min. Full characterization of nickel manganite samples was done using SEM, EDS and XRD analysis. The Hall effect was measured at different temperatures (room temperature, 50, 80, 100 and 120 °C) with an applied field of 0.37 T and also 0.57 T at room temperature. The activation energy E a (energy of conduction) and the coefficient of temperature sensitivity B 25/80, were calculated from measured resistivity values. The measured mobility, resistivity/conductivity, U-I plots, and Hall coefficients were mutually compared and correlated versus microstructure development and macroscopic parameters such as the powder activation time and ambient temperature.

Effect of element substitution on the superconducting properties of Gd-based melt-processed bulk-superconductors

We studied the effect of Co doping on the superconducting properties of melt-processed Gd-Ba-Cu-O bulk-superconductors and compared the results with Zn doping, the former substitutes for Cu of the Cu-O chain while the latter to the CuO2 plane. The critical current density (Jc) at 77 K of the region beneath the seed crystal increased with the Co3O4 content up to 0.23 wt.%, and that of the a-growth region about 5 mm away from the seed crystal up to 0.30 wt.%. The analysis of the pinning force showed that Co doping increases the amount of normal pins (δl pinning). The measurements of the time dependence of the trapped field of the samples doped with various amounts of Co3O4 indicated that the creep rate at 77 K increases with Co3O4 content. This result suggests that the pinning potential of the normal pin created by the addition of Co3O4 is relatively small.

Deposition of CoO onto MoO3/Al2O3 hydrodesulfurization catalysts by solvent assisted spreading

Solvent assisted spreading of CoO over monolayer MoO3/Al2O3 catalysts has been studied. CoCO3 · Co(OH)2 and CoCO3 reacted with MoO3/Al2O3 in water slurries. CoO deposition over MoO3/Al2O3 extrudates was followed by EPMA. In the set of eleven MoO3/Al2O3 catalysts, the amount of CoO adsorbed was roughly proportional to the surface area of MoO3 monolayer. The adsorbed Co species efficiently enhanced the HDS activity.

Nanocrystalline cobalt oxide immobilized on titanium dioxide nanoparticles for the heterogeneous activation of peroxymonosulfate

Recently, sulfate radical-based advanced oxidation technologies have shown significant implications for environmental remediation to decompose water pollutants. In this study, we evaluated the performance of heterogeneous activation of peroxymonosulfate (PMS) to generate sulfate radicals using cobalt catalyst immobilized on titanium dioxide nanoparticles (Co/TiO2). The Co/TiO2 catalyst was prepared via an incipient wetness impregnation method employing Degussa P-25 TiO2 and Co(NO3)·6H2O. The activity of Co/TiO2 system was compared with those of Co(NO3)2 solution for homogeneous PMS activation and neat Co3O4 for heterogeneous PMS activation. More emphasis was given to the effect of cobalt loading and heat treatment on the physicochemical properties of Co/TiO2 and cobalt leaching. The results showed that heat treatment of Co/TiO2 at 500°C, where cobalt existed as Co3O4, induced negligible Co leaching and enhanced catalytic activity to decompose 2,4-dichlorophenol. The Co/TiO2 catalyst at Co/Ti molar ratio of 0.1 showed the highest activity via heterogeneous PMS activation. On the other hand, Co/TiO2 catalysts with Co/Ti molar ratio of above 0.2 exhibited rather much lower activity which was initiated predominantly via a homogeneous pathway from leached cobalt, although they contained considerable amounts of Co3O4. The formation of CoOH complexes at the surface of Co/TiO2 nanoparticles, due to the ability of TiO2 to dissociate H2O for the formation of surface hydroxyl groups, was proposed to facilitate the heterogeneous PMS activation. However, high cobalt loading covering the TiO2 surface diminished the beneficial role of TiO2 due to the reduction in the concentration of surface hydroxyl groups and thus decreased the heterogeneous PMS activation. The activity of Co3O4 in Co/TiO2 catalysts was much higher than that of neat Co3O4 due to the presence of surface hydroxyl groups and uniform distribution of well-defined 10−15nm nanocrystalline Co3O4 particles at the surface of 30−40nm TiO2 nanoparticles.

Effect of CoO Doping on the Sintering Ability and Mechanical Properties of Y-TZP

The effect of CoO addition into Y-TZP (Yttria doped Tetragonal Zirconia Polycrystals) was studied on the evolution of its sintering ability, grain size, grain boundary structure and mechanical properties. The doping of a small amount of CoO effectively reduced the sintering temperature. A small amount of CoO up to ~ 0.3 mol% was effective for the suppression of grain growth, but the addition of 1.0 mole % resulted in an enhanced grain growth. The hardness and toughness of the CoO doped TZP were about the same as those of undoped TZP. Furthermore, despite the grain refinement, CoO doped TZP did not exhibit improved mechanical properties. This may be suggesting that CoO dopant had weakened the grain boundary strength.

Effect of firing atmosphere on Pb(Co1/3Nb2/3)O3-PZT ceramics

We investigated the ceramic bulk density, crystalline phase, microstructure and electrical property in Pb(Co1/3Nb2/3)O3—PZT ceramics fired in air and oxygen atmosphere to clarify the origin of their semiconductive characteristics. Although a pyrochlore phase due to B-site vacancies produced by Co vaporization while both firings was segregated and suppressed the grain growth, the ceramics showed high resistivity (ρ) and small dielectric loss (tan δ). An addition of CoO (∼0.1 wt%) to the ceramic composition with stoichiometry inhibited the Co vaporization and the production of the pyrochlore phase in the perovskite phase. As a result, the ceramic bulk density of the compositions added a small amount of CoO increased. However, the grain growth was promoted and the ceramics became low ρ and large tan δ in case of the compositions added a large amount of CoO (0.4—6.0 wt%). Although PbO was segregated in addition to a perovskite phase on the ceramics fired in air, the perovskite single phase was obtained on the ceramics fired in O2. There was a great difference (0.2g/cm3) in bulk density between ceramics fired in air and annealed in O2. It was thought that the decrease in bulk density with and witout annealing was due to the production of ilmenite phase such as CoTiO3 and the oxidation of Co on grain surface from Co2- to Co3+. The firing atmosphere dependence of ρ and tan δ was also explained by the production of the ilmenite phase.

Wear resistance of crystals of corundum doped with Cr 2O 3, TiO 2, and CoO

The wear resistance of crystals of corundum sliding on cast iron was determined as a function of crystallographic orientation with respect to the plane of wear and rubbing direction and as a function of changes of structure of crystals. The experimental work was based on Verneuil grown single crystals of synthetic corundum (α-Al 2O 3); non-doped and doped with: Cr 2O 3 amount 0.5 and 1.5% wt.; TiO 2 amount 0.1 and 0.25% wt.; CoO amount 0.1 and 0.5% wt.. Wear resistance ( as an inverse of abrasion wear) was determined on four crystallographic planes: (0001); {112̄0}; {11 2 ̄ .12}; {11 2 ̄ 3} and twelve rubbing directions, started from [1100] direction, every 30 °. A varying sliding rate of the specimens of the crystals over the surface of the cylinder of cast iron was used. The orientation of the specimens was determined by standard Laue techniques, and after this, was checked by X-ray-line-reflection techniques ( simultaneously the [1̄100] direction was determined), The volume of material lost by wear from the surface of crystals was calculated from the change of the planimetred profile of the surface (before and after wear) of two perpendicular outlines of specimens.

Initial stages of cobalt oxidation by FTIR spectroscopy

The behaviour of specular reflectance of cobalt oxides on metal has been studied theoretically (CoO/Co system) and experimentally (Co304/Co system; the thin films are obtained by chemical spray pyrolysis) in the infrared region. COO may be identified by a LO mode at 585 cm-I and by a T O mode at 345 cm-l. Co304 is characterized by five bands respectively at 690 (LO), 660 (TO), 605 (LO), 560 (TO) and 390 cm-l. These experimental results allow the characterization of COO and Cos04 grown on metal during the initial stages of thermal oxidation (400-750 OC). For film thicknesses in the range 10-1000 nm, the amounts of COO and Co304 in the duplex structure layers may be estimated by FTIR reflectance spectroscopy. FTIR and XRD studies reveal a cyclic behaviour in the growth of the Co304/CoO/Co system.

ESCA studies of Cr-Co alloys

ESCA examination of films formed on Cr-Co alloys after immersion in 0.1M NaCl for 24 h has shown that the thickness of passive films decreased with an increase in chromium content. Surface films consisted of chromium and cobalt oxides as Cr2O3 and CoO. The amount of CoO in the surface film of the alloy was decreased with an increase in chromium but Cr2O3 was found at a greater depth in the passive film at any composition. Cr2O3 was a major component of the surface film when the chromium content in the alloy was 10% or higher. Electrochemical techniques according to ASTM G59 and ASTM G5 were used for the determination of the relative corrosion rate. Both Co-10 wt.% Cr and Co-30 wt.% Cr alloys investigated showed a lower corrosion rate than the Co-5 wt.% Cr alloy. Corrosion rate measured could be correlated to the surface film composition and structure as determined by ESCA.

Application of cross-correlation analysis to EXAFS: Investigation of the cobalt phase on boron modified cobalt/alumina catalysts

Boron modified Co/Al2O3 catalysts, previously characterized by ESCA, are examined by EXAFS. A method of data analysis based on cross-correlation of the χ(E) spectra is used to determine the relative amounts of Co3O4 and cobalt surface phase present on the catalysts. The results are compared with those obtained previously by ESCA. The EXAFS analysis agrees well with the ESCA results. No gas-phase reactions were required to elucidate the relative proportion of cobalt species by EXAFS as is necessary for the ESCA analysis.

Effect of cobalt oxide on the a.c. conduction mechanism of copper tellurite glasses

Electrical measurements on binary and ternary glasses of compositions 65TeO2-35CuO and 65TeO2-34CuO-1CoO (mol%) are reported at temperatures between 293–458 K in the frequency range up to 10−6 Hz. The measured conductivity shows a frequency dependence obeying the equation σ(ω) =Aωs withs <1 but taking different values at different temperatures. The capacitance of the glasses shows an increase in value with increase in temperature at low frequencies. The tangent of the loss angle (tan δ) and dielectric loss factor ɛr″were found to increase with the increase in temperature and decrease in frequency but the usual Debye loss peaks were absent even at high temperatures. The relative dielectric constant ɛr was unexpectedly high, approximately 103, and was found to decrease very slightly with increasing frequency. Overall the effect of a small amount of CoO (a 1 mol%) is found to have a dominant effect on the dielectric properties of copper tellurite glasses.