Morphology Of Oxide Research Articles

Engineering morphologies of yttrium oxide supported nickel catalysts for hydrogen production

Engineering morphologies of yttrium oxide supported nickel catalysts for hydrogen production

Investigation of the parameters affecting the morphology of zinc oxide (ZnO) nanoparticles synthesized by precipitation method

In this work, zinc oxide (ZnO) nanoparticles were synthesized using aqueous solutions of ZnSO4 and NaOH at ambient temperature and 70 °C. The nanoparticles synthesized at these two temperatures were identified and analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), infrared spectroscopy (FTIR), dynamic light scattering (DLS), and zeta potential (ZP). SEM micrographs showed that temperature, method of mixing, and stoichiometric ratio could significantly affect the formation of particles of different sizes and morphology. Phase analysis of synthesized particles was performed by X-ray diffraction. The result showed that temperature had the tremendous potential to convert precursors into products to form a single-phase compound completely. These results were confirmed by the observed characteristic peaks in FTIR. The crystallite size was calculated using Scherer's equation and Rietveld analysis to investigate the effect of the calcination process on the crystal size of the synthesized particles. The results showed that the calcination process could significantly affect the crystal size of the synthesized particles. Both methods showed an increase in the average crystal size of zinc oxide particles after the calcination process. The absolute magnitude of the zeta potential for zinc oxide particles with a pyramidal rod morphology with an average diameter of 80–90 nm was 33.2 and for star-like morphology with an average diameter of 800–900 nm was 11.8.

Insights into the Fe oxidation state of sphere-like Fe2O3 nanoparticles for simultaneous Pb2+ and Cu2+ detection

Iron-based oxides have been widely used in investigating the performance of electrochemical sensing due to their abundant sources, excellent biocompatibility, and high catalytic activity. However, previous studies mainly focused on the effect of the morphology or crystal phases of iron oxides on the electrochemical sensing performance, while the influence of different valence states was rarely reported. Therefore, for designing iron-based oxides with highly active components, it is meaningful to understand the effect of their oxidation states on the electrochemical sensing performance. In this study, monodisperse sphere-like Fe2O3 nanoparticles (Fe2O3 NPs) with a diameter of 80–100 nm were synthesized through a novel emulsion hydrothermal method and a subsequent annealing process in Ar atmosphere. The results of X-ray photoelectron spectroscopy (XPS) indicated that the Fe2+/Fe3+ ratio and oxygen vacancy content in Fe2O3 NPs can be tuned by changing the annealing temperature. As a modified electrode, the electrochemical sensing performance of Fe2O3 NPs improved with the increase in the Fe2+/Fe3+ ratio, indicating that the oxidation state of Fe played an important role in the electrochemical sensing of heavy metal ions (HMIs). As a result, a typical electrode, namely, Fe2O3 NPs-550 annealed at 550 °C with optimal Fe2+/Fe3+ ratio and oxygen vacancy content exhibited the best performance for simultaneously detecting Pb2+ and Cu2+ (limits of detection: 9.48 nM and 38.31 nM, respectively). Electrochemical adsorption experiments revealed that the Fe2O3 NPs-550 electrode (Fe2O3 NPs-550/GCE) showed the highest adsorption capacity for Pb2+ and Cu2+, demonstrating that the presence of Fe2+ and oxygen vacancies were beneficial for the adsorption of heavy metal ions and enhancing the sensing performance. This study emphasizes the important role of different oxidation states of Fe in the electrochemical sensing of HMIs and provides a new idea for the design and preparation of high-performance metal oxide nanosensors for real-time environmental detection.

Effect of Al2O3 Content on High-Temperature Oxidation Resistance of Ti3SiC2/Al2O3

Considering the lack of an effective anti-oxidation protective layer for the oxidation process of Ti3SiC2, an in situ synthesis of Ti3SiC2 and Al2O3 was designed. Thermally stable Al2O3 was used to improve the high-temperature oxidation resistance of Ti3SiC2. Samples without TiC were selected for the oxidation test, and the oxidation morphology and weight gain curves of the oxidized surface in air at 1400 °C are reported. The change in the oxidation behavior occurred 4 h after oxidation. The addition of Al2O3 changed the composition of the oxide layer and compensated for the lack of a dense protective layer during Ti3SiC2 oxidation. Moreover, after 4 h of oxidation, the newly generated Al2TiO5 and the composite layer formed by diffusion were the main reasons for the large difference in the final weight gain between the two sets of samples.

High-temperature thin film lithium niobium oxide transducers for bolts

In the present work, we studied structure, surface morphology, and ultrasonic response of thin film Lithium Niobium Oxide (LNO) transducers deposited on Inconel bolts, stainless steel and silicon substrates by radio frequency magnetron sputtering. The deposited transducer material was a mixture of LiNbO3/LiNb3O8 phases, having a well-developed columnar structure. Further, the in-situ high-temperature ultrasonic response was studied in the temperature range of 18–800 °C in ambient air during short-term annealing. It was observed that long-term annealing (at 700 °C for 160 h and 800 °C for 40 h) deteriorated the ultrasonic response, owing to the irreversible change from the initial columnar structure to the porous granular structure. Dielectric and piezoelectric properties of the thin film LNO transducers were also studied. The thin film LNO ultrasonic transducers have potential applications in bolts and screws up to 700 °C.

Investigation of Optical Properties and Electronic Transfer of Temperature-Dependent ZnO Nanocolumnars Grown by DC Sputtering

The morphology of zinc oxide (ZnO) can determine the distribution of defects in the system, which plays an important role in determining its optical and electronic properties. Here, we investigate the optical and electronic transfer properties of different ZnO surface morphologies. ZnO nanocolumnar was synthesized by direct-current (DC) sputtering followed by annealing using a ratio of T / Tm are 0.15, 0.20, and 0.25. The x-ray diffraction (XRD) results show that an increase in annealing temperature causes an increase in crystal size accompanied by a decrease in lattice strain. Furthermore, the surface morphology of the sample changed with increasing annealing temperature treatment, following the structural zone model. The optical and electronic transfer properties of the samples were investigated in three regions; region 1 ( T / Tm is 0.15), region 2 ( T / Tm is 0.20), and region 3 ( T / Tm is 0.25) using optical modeling. The highest surface electronic transfer was noted in region 2, which is indicated by the highest surface energy loss function (SELF). This research can provide a good understanding in designing optoelectronic systems based on their morphological features. DOI: 10.17977/um024v7i22022p086

Enhanced Electrocatalytic Properties of Co3O4 Nanocrystals Derived from Hydrolyzed Polyethyleneimines in Water/Ethanol Solvents for Electrochemical Detection of Cholesterol

The present study describes the effect of hydrolysis of polyethyleneimines in water/ethanol mixture on the morphology of the cobalt oxide (Co3O4), used as the main sensor component. The structure of the generated Co3O4 nanocrystals is consistent with a well-defined cubic phase crystallography, having only cobalt and oxygen elements. Developing simple, low-cost, sensitive, and selective cholesterol biosensors is essential for accurate monitoring of cholesterol to avoid cardiovascular diseases. These nanocrystals exhibit large surfaces suitable for facile and high loading of cholesterol oxidase enzyme through the physical adsorption method. Then, the fabricated cholesterol oxidase/ Co3O4 nanocrystals composite was implemented for potentiometric detection of cholesterol in 10 mM phosphate buffer of pH 7.3. Importantly, the presented cholesterol biosensor revealed a wide linear range of 0.005 mM to 3.0 mM with a limit of detection (LOD) of 0.001 mM. Additionally, the sensitivity of biosensor was estimated around 60 mVdec−1. The selectivity, stability, reproducibility, and repeatability were also observed as satisfactory. The dynamic response of the proposed method demonstrated a fast response time of less than 1 s. Furthermore, the successive addition method confirmed a remarkably stable response towards various cholesterol concentrations. Thus, the developed cholesterol oxidase/ Co3O4 nanocomposite may be used as an efficient alternative method to monitor low cholesterol concentrations form real samples.

Effect of controlled cooling process on the atmospheric corrosion behaviour of HRB400E hot rolled rebar

To address the problem of rusting of reinforcing bars that occurs in industry, the aim is to control the denseness of the iron oxide skin by changing the controlled cooling process without increasing the production cost, thereby improving the corrosion resistance of the bars. In this paper, the effect of different cooling control processes on the industrial atmospheric corrosion behaviour of HRB400E hot-rolled rebar was investigated using alternating wet and dry corrosion tests. The morphology and structure of iron oxide on the surface and cross-section of the rebar were observed using scanning electron microscopy (SEM) and field emission electron probe microanalysis (EPMA); the corrosion products and electrochemical behaviour of the specimens after alternating wet and dry tests were compared using x-ray diffraction analysis (XRD) and electrochemical methods. The results showed that the hot-rolled rebar without controlled cooling had a dense surface, a thicker iron oxide skin and a tighter bond between the iron oxide skin and the substrate; the corrosion rate of the hot-rolled rebar without controlled cooling was less than that of the rebar with controlled cooling in the alternating wet and dry corrosion tests; the corrosion products mainly consisted of α-FeOOH, γ-FeOOH and Fe3O4; the self-corrosion potential and rust layer resistance of the hot rolled rebar without controlled cooling after rolling are higher than those of the controlled cooling bars, showing good corrosion resistance.

Reagent-and solvent-mediated Fe2O3 morphologies and electrochemical mechanism of Fe2O3 supercapacitors

A solvothermal technique was used to synthesize nine different ferric oxide (Fe 2 O 3 ) morphologies: rhomb ( R ), flower ( F ), hollow sphere ( HS ), crystal ( C ), elongated hexagon ( EH ), hexagon ( H ), sugar apple ( SA ), sand/spherical particle ( SSP ) and mixed particle ( MP ). X-ray diffraction, high-resolution transmission electron microscopy and selected area electron diffraction reveal six of the nine powders to be composed of the pure α-Fe 2 O 3 structure, whereas the EH-Fe 2 O 3 , H-Fe 2 O 3 and SA-Fe 2 O 3 powders contain the mixed α-Fe 2 O 3 /Fe 3 O 4 structure. The F-Fe 2 O 3 powder has the highest total specific pore volume (0.059 cm 3 g −1 ), the largest average pore size (23.983 nm), and a high specific surface area (9.82 m 2 g −1 ), which subsequently produce the highest specific capacitance of 218.49 F g −1 . X-ray photoemission spectroscopy and energy dispersive spectroscopy detect H 2 O and K + adsorption on the F-Fe 2 O 3 electrode and the reduction of Fe 3+ to Fe 2+ in the charged state, whereas H 2 O molecules and K + ions are released from the F-Fe 2 O 3 electrode, and Fe 2+ is oxidized to Fe 3+ in the discharged state. The simulated K-inserted-α-Fe 2 O 3 structure shows an increased electron density surrounding Fe atoms, which is indicative of Fe 3+ reduction during the charged state. The F-Fe 2 O 3 film is able to retain 76.81 % of its 20 th cycle value after 1,000 cycles. Four series-supercapacitor coin cells constructed from the F - Fe 2 O 3 anode and the MnO 2 cathode deliver an outstanding energy density of 10.96 Wh kg −1 and power density of 0.461 kW kg −1 . • Nine Fe 2 O 3 morphologies were synthesized by different reagents and solvents. • F-Fe 2 O 3 electrodes have the highest specific capacitance of 218.49 F g −1 . • The charged/discharged F-Fe 2 O 3 electrode inserts/deinserts H 2 O molecules and K + ions. • K-inserted-α-Fe 2 O 3 structure displays increasing electron density on Fe atoms. • MnO 2 // F-Fe 2 O 3 gives high energy (15.58 Whkg −1 ) and power densities (399 Wkg −1 ).

Ultrahigh Energy Density and Long-Life Cyclic Stability of Surface-Treated Aluminum-Ion Supercapacitors.

In this study, aluminum-graphene supercapacitors (denoted as aluminum-ion supercapacitors; ASCs), consisting of a battery-type aluminum anode, a capacitor-type graphene cathode, and ionic liquid 1-ethyl-3-methylimidazolium chloride (EMImCl) and aluminum chloride (AlCl3) electrolyte, were prepared. This study primarily aimed to investigate the enhanced electrochemical performance of ASCs arising from changes in the surface oxide layer and morphology via electrochemical surface treatments, including electropolishing and electrodeposition of aluminum anodes. The ASC devices based on an electrodeposited anode at a current density of 3 A g-1 exhibited a high specific capacity of 211 F g-1 compared to that of the electropolished anode (∼186 F g-1); these were 20 and 5.7%, respectively, higher than that of the pristine aluminum anode. In particular, the electrodeposited ASC delivered an energy density of 151 W h kg-1 at a power density of 3,390 W kg-1. Furthermore, a maximum power density of 11,104 W kg-1 was achieved at an energy density of 124.3 W h kg-1. These values are among the best as compared to those of previously reported aluminum-based supercapacitors, suggesting the potential feasibility of these ASCs with outstanding energy and power densities for next-generation energy storage devices.

Crystallization, Phase Stability, Microstructure, and Chemical Bonding in Ga2O3 Nanofibers Made by Electrospinning.

We report on the crystal structure, phase stability, surface morphology, microstructure, chemical bonding, and electronic properties of gallium oxide (Ga2O3) nanofibers made by a simple and economically viable electrospinning process. The effect of processing parameters on the properties of Ga2O3 nanofibers were evaluated by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Thermal treatments in the range of 700–900 °C induce crystallization of amorphous fibers and lead to phase stabilization of α-GaOOH, β-Ga2O3, or mixtures of these phases. The electron diffraction analyses coupled with XPS indicate that the transformation sequence progresses by forming amorphous fibers, which then transform to crystalline fibers with a mixture of α-GaOOH and β-Ga2O3 at intermediate temperatures and fully transforms to the β-Ga2O3 phase at higher temperatures (800–900 °C). Raman spectroscopic analyses corroborate the structural evolution and confirm the high chemical quality of the β-Ga2O3 nanofibers. The surface analysis by XPS studies indicates that the hydroxyl groups are present for the as-synthesized samples, while thermal treatment at higher temperatures fully removes those hydroxyl groups, resulting in the formation of β-Ga2O3 nanofibers.

Cage-like MnSe@PPyC/rGO as superior dual anode materials in Li/Na-ions storage

Along with high reversible capacity, superior cycling and rate performances, transition metal-based materials have been considered as promising dual anode materials for lithium/sodium ion storage. However, one of the greatest challenges during the selenization process is that the as-prepared transition metal selenides with designed morphology could retain the original morphology of transition metal oxides well. To address this key issue, in this work, a cage-like MnSe@PPyC/rGO composite is successfully developed by one-step selenization/carbonization treatment with in-situ formed polypyrrole coated MnO2 nanorods and graphene oxide as precursors, which effectively preserve the original rod-like morphology and endow a conductive network. The morphology control process, composition and microstructural change have been systematically characterized with SEM, EDS, TEM, TGA, BET, XRD, and XPS. Benefited from the above composition and structure, cage-like MnSe@PPyC/rGO exhibits good rate performance (310.3 mAh/g at 3.2 A/g) and high reversible lithium storage capacity (776.9 mAh/g at 0.1 A/g after rate testing). As anode materials for SIBs, the composite demonstrates high capacity of 546.6 mAh/g at 0.2 A/g as well as outstanding rate capability and cycle stability (294.4 mAh/g after 455 cycles at 2 A/g and 194.5 mAh/g after 2000 cycles at 10 A/g). The finding provides a new avenue for the study of transition metal/carbon composites with special morphology as dual anode materials for Li/Na-ions storage.

Study on the Surface Area of Electrospun Magnesium Oxide (MgO) Nanofibers

The optimized surface morphology of electrospun magnesium oxide (MgO) nanofibers can be achieved based on the parameters set during the fabrication of nanofibers. However, not all materials used during the electrospinning process can be synthesized together as it depends on the application’s needs. This research aims to study the factors that influence the surface area of the MgO nanofibers due to material preparations and electrospinning parameters. The research is based on data obtained from the previous research and was analyzed to evaluate the effect on MgO nanofibers that synthesized with different materials. Based on the data analysis using Brunauer-Emmert-Teller (BET), the surface area for carbon sorbent is higher than organic sorbent. The surface area for carbon sorbent of nitrogen could be achieved up to 324.5 m2/g compared to only 104.8 m2/g using organic sorbent for magnesium oxalate dihydrate (MO). The studies show that the use of nitrogen as a carbon sorbent in the fabrication of electrospun MgO nanofibers may produce a good quality of nanofibers.

Thermal reduction of graphene oxide and polyethyleneimine composite membranes with selective ion permeability

Graphene oxide has great potential as filtration membranes because its permeability and selectivity can be controlled through its functional groups. Herein, we studied the morphologies of graphene oxide and polyethyleneimine composite membranes. We demonstrated that polyethyleneimine helps to reduce oxygen-containing functional groups in such composite membranes through Raman, X-ray photoelectron, and Fourier-transform infrared spectroscopies. This indicates that thermally annealed graphene oxide and polyethyleneimine composite membranes tend to remove oxygen functional groups. Furthermore, we investigated the change in permeability due to the reduction in oxygen groups. Consequently, we revealed that the loss of hydroxyl and carboxyl groups impart hydrophobicity to the membranes. Our study is useful for the construction of artificial membranes.

Morphology and Vibrational Modes of Lanthanum Oxide (La2O3) Nanoparticles Prepared with Reflux Routes at Different Reaction Times

Morphology and Vibrational Modes of Lanthanum Oxide (La2O3) Nanoparticles Prepared with Reflux Routes at Different Reaction Times

Environmentally benign approach for the efficient sequestration of methylene blue and coomassie brilliant blue using graphene oxide emended gelatin/κ-carrageenan hydrogels

Herein, we report the synthesis and characterization of gelatin/κ-carrageenan crosslinked polyacrylic acid hydrogel (GT-CAG-cl-polyAA) and graphene oxide incorporated hydrogel nanocomposite (GOHNC) through a free radical crosslinking pathway. Under optimized reaction conditions, GT-CAG-cl-polyAA displayed 486 % maximum swelling percentage. TEM image depicted wrinkled silk veil wave-type surface morphology of graphene oxide (GO), whereas, the SEM analysis indicated the porous nature of the GT-CAG-cl-polyAA and GOHNC capable of accumulating a large number of water/dye molecules. GT-CAG-cl-polyAA exhibited 96.11 % and 82.16 % dye removal potential for the adsorption of methylene blue (MB) and coomassie brilliant blue (CB), respectively under optimized conditions. GOHNC enhanced the % dye removal efficiency (98.39 % for MB and 94.50 % for CB). The maximum adsorption capacity of GOHNC for the removal of CB and MB was 312.7 mg/g and 94.9 mg/g, respectively. The adsorption of CB and MB exhibited best fitting with Flory-Huggins adsorption isotherms data. The negative values of ΔG° and positive values of ΔS° which were obtained from the adsorption isotherm plot suggested the thermodynamic feasibility of the adsorption. Also, the samples were reusable for up to five consecutive cycles without any degradation and hence suggested a considerable pathway for the separation of textile dyes.

Effects of different zinc oxide morphologies on photocatalytic desulfurization of thiophene

Zinc oxide (ZnO) nanoparticles are superior photocatalysts for pollutant degradation due to their stability, low hazard, and high photosensitivity. The morphology of this material is one of the key factors influencing the performance of pollutant degradation. In fact, studies on the effects of different ZnO morphologies on thiophene desulfurization via photocatalysis process are limited. Thus, this study focuses on the performance of different ZnO morphologies for thiophene desulfurization. Nine ZnO nanoparticles were synthesized and categorized into two groups, namely flower-like and non-flower-like ZnO. Flower-like ZnO included flakes, clusters, rods, and needles, while the non-flower-like ZnO comprised nanoballs, short-nanorods, nanocubes, and nanoporous. The physical properties of all ZnO morphologies were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and Fourier-transform infrared (FTIR), and compared with commercial ZnO. From the findings, flower-like ZnO flakes showed the highest performance in thiophene desulfurization (30%). High pH and turbidity reduction in the permeate confirmed that the thiophene compound in the solution was highly degraded after treatment. Moreover, all ZnO morphologies applied to pseudo-second-order models due to higher linear regression (R2) values. Greater thiophene desulfurization was indicated by the highest Ce value of ZnO flakes (909.09 mg/g). The optimum conditions for thiophene desulfurization were at pH 7 and 0.05 g/L ZnO flakes loading for 90 min contact time.

Transitions in porous oxide morphologies on AA2024-T3 anodized under high currents and low temperatures: Impact on corrosion behaviour

The surface morphology, cell geometry, and electrochemical response of porous anodic films of comparable thickness, generated on AA2024‐T3 in sulphuric acid electrolyte under hard and soft anodizing conditions, were studied to disclose the impact of the anodizing parameters on corrosion behaviour. Localised oxide growth associated with a transition from sponge-like morphology to linear cells was observed with increasing current density and/or reducing electrolyte temperature. The anticorrosion performance of films with the higher barrier layer thickness was inferior due to the defective surface induced by localised oxide growth at high currents or low temperatures. Viceversa, the films displaying sponge-like morphology performed better due to the beneficial effect of inter-cell porosity in facilitating the self-sealing process.

Preparation of matrix-grafted graphene/poly(poly(ethylene glycol) methyl ether methacrylate) nanocomposite gel polymer electrolytes by reversible addition-fragmentation chain transfer polymerization for lithium ion batteries

A structural design and appropriate morphology of polymer-functionalized graphene oxide are occupied to optimize nanocomposite polymer electrolytes. The nanocomposite gel polymer electrolytes (GPEs) based on poly(poly (ethylene glycol) methyl ether methacrylate and RAFT agent-functionalized graphene oxide [P(PEGMA/GO-S-(thiobenzoyl)thioglycolic acid (STTA))] have been successfully prepared by in-situ polymerization method in different ratio of GO-STTA and crosslinking by poly(ethylene glycol) diallyl (PEGDA). The P(PEGMA/GO-STTA) GPE with 0.5 wt% of GO-STTA exhibited a high ionic conductivity of 5.5 mS cm−1 at room temperature, a superior lithium transfer number (t+) value of 0.61, and electrochemical window up 4.7 V. The GPE based P(PEGMA/GO-STTA0.5%) indicated 92% coulombic efficiency, the charge capacity value of 191.7 mAh g−1, and capacity retention was about 92% after 100 cycles at 0.1C. P(PEGMA/GO-STTA) GPEs showed great potential for lithium ion battery with high safety and long cycle life.

Cardiovascular biomarker troponin I biosensor: Aptamer-gold-antibody hybrid on a metal oxide surface.

Myocardial infarction (MI) is highly related to cardiac arrest leading to death and organ damage. Radiological techniques and electrocardiography have been used as preliminary tests to diagnose MI; however, these techniques are not sensitive enough for early-stage detection. A blood biomarker-based diagnosis is an immediate solution, and due to the high correlation of troponin with MI, it has been considered to be a gold-standard biomarker. In the present research, the cardiac biomarker troponin I (cTnI) was detected on an interdigitated electrode sensor with various surface interfaces. To detect cTnI, a capture aptamer-conjugated gold nanoparticle probe and detection antibody probe were utilized and compared through an alternating sandwich pattern. The surface metal oxide morphology of the developed sensor was proven by microscopic assessments. The limit of detection with the aptamer-gold-cTnI-antibody sandwich pattern was 100 aM, while it was 1 fM with antibody-gold-cTnI-aptamer, representing 10-fold differences. Further, the high performance of the sensor was confirmed by selective cTnI determination in serum, exhibiting superior nonfouling. These methods of determination provide options for generating novel assays for diagnosing MI.