Pure Zinc Research Articles

Sparked ZnO nanoparticles-based electrochemical sensor for onsite determination of glyphosate residues.

Glyphosate (N-(phosphonomethyl)glycine) is well known nonselective and broad-spectrum herbicide that has been extensively used in agricultural areas around the world to increase agricultural productivity. However, the utilization of glyphosate can cause environmental contamination and health problems. Therefore, the detection of glyphosate with a fast, low-cost, and portable sensor is still important. In this work, the electrochemical sensor has been developed by modifying of working surface on the screen-printed silver electrode (SPAgE) with a mixtures solution between zinc oxide nanoparticles (ZnO-NPs) and poly(diallyldimethylammonium chloride) (PDDA) by the drop-casting process. The ZnO-NPs have been prepared based on a sparking method by using pure zinc wires. The ZnO-NPs/PDDA/SPAgE sensor shows a wide range of glyphosate detection (0μM-5 mM). The limit of detection of ZnO-NPs/PDDA/SPAgE is 2.84μM. The ZnO-NPs/PDDA/SPAgE sensor exhibits high selective towards glyphosate with minimal interference from other commonly used herbicides including paraquat, butachlor-propanil and glufosinate-ammonium. Furthermore, the ZnO-NPs/PDDA/SPAgE sensor demonstrates a good estimation of glyphosate concentration in real samples such as green tea, corn juice and mango juice.

The effects of saline water on the recovery of lead and zinc sulfide during froth flotation

In this study, we investigated the effects of water salinity on the flotation performance of pure lead and zinc sulfide mineral samples as well as a Pb/Zn complex sulfide ore by means of micro-flotation and batch flotation experiments. Our results showed higher PbS and ZnS recoveries in more concentrated NaCl salt solutions. The results for the experiments using seawater demonstrated that in the presence of additional ions, such as Ca2+ and Mg2+, the recovery of PbS and ZnS was significantly reduced.As part of this investigation, we developed and implemented a surface complexation model for ZnS based on the presence of two differently charged surface sites. Zeta potential measurements of ZnS particles were used to optimise the parameters of our model. It was found that the surface potentials calculated using this model were in good agreement with the experimental zeta potentials, validating the model for predicting the zeta potential behaviour of ZnS particles over a broad range of pH and NaCl concentrations.Additionally, total interaction free energies were determined as a function of separation distance, representing particle–particle and particle-bubble interactions of our study in different NaCl concentrations. The theoretical analyses showed that asymmetric Pb/Zn particle–particle interactions were repulsive at lower NaCl concentrations, before becoming purely attractive at higher NaCl concentrations. For the case of the symmetric particle–particle interactions, attraction controlled all interactions, regardless of NaCl concentration. The calculated PbS-bubble interactions were repulsive in lower NaCl concentrations but became increasingly attractive in higher NaCl concentrations. Strong repulsions controlled all ZnS-bubble interactions, and these interactions remained repulsive with increasing NaCl concentration. The theoretical projections presented in this study were in good agreement with the measured saline water flotation phenomena.

Effect of pre-oxidation at 850 °C under low oxygen pressure on the zinc liquid corrosion resistance of Fe-20Cr-5B–3Al alloy

In the process of hot-dip galvanizing, components working in liquid zinc for a long period of time naturally corrode and fail prematurely. Meanwhile, Cr and Al elements can be used to improve the corrosion resistance of Fe-B alloy in Zn liquid, unfortunately, the α-Fe matrix still gets preferentially corroded. In this work therefore, pre-oxidation is performed under a low oxygen pressure to form oxides of Cr2O3, Al2O3 and FeCr2O4 on the surface of the alloy, which effectively prevents the diffusion of zinc liquid. The oxidation behavior of Fe-5B–20Cr-3Al alloy at 850 °C is then analyzed by thermodynamic calculation and experimentally studied. The corrosion properties of the pre-oxidized alloy in Zn-55 wt% Al liquid and pure zinc liquid are subsequently investigated. Findings revealed that the oxide film forms under oxygen pressure of 10−20.5 atm. is dense, and the thickness reaches 8 µm. Moreover, FeCr2O4 and a small amount of B and Cr oxides are distributed in the upper part of the oxide film, coupled with internal oxidation of Al2O3 on the α-Fe phase. These ensure the continuity and compactness of the oxide film, thus exhibiting the best corrosion resistance to zinc liquid and zinc aluminum liquid. Consequently, pre-oxidation of Fe-5B–20Cr-3Al alloy under low oxygen pressure at 850 °C is proposed as an efficient method to ensure corrosion resistance of the alloy in a zinc-aluminum solution.

Effect of Hexagonal Boron Nitride Nanoparticles Additions on Corrosion Resistance for Zinc Coatings of Weathering Steel in Rainwater

Zinc and its alloy coatings are commonly used to provide cathodic protection for weathering steel. However, the steel substrate corrodes faster than the Zinc coating because of the coating's negative corrosion potential. Many studies have examined Zinc and alloy coatings' resistance to corrosion. Hot-dip galvanizing, Electrodeposition, and Zinc-rich coat (ZRC) spray are just some of the methods that can be used to deposit such coatings. Commercially available 99.95 % pure Zinc oxide was used in the electroplating process in this investigation. Steel samples were plated in Zinc sulphate and Zinc oxide solutions and were controlled by different bath parameters such as voltage, current, pH, temperature, and coating time. The addition of hexagonal Boron Nitride (h-BN) nanoparticles has also shown significant improvements in corrosion resistance. However, Zinc-based coating techniques reinforced with h-BN incorporation show the best corrosion current density (Icorr) of Hot dip 2 % wt. (2.1 μA/cm2), ZRC 2.5 % wt., (4.4 μA/cm2), and electroplating 15.75 g/L (0.081 μA/cm2), which is an order of magnitude lower than coatings without h-BNs. The corrosion rates and current densities of Zn/h-BN coated layers were investigated in a controlled laboratory environment that mimicked natural conditions (Rainwater solution) by extrapolating polarization curves.

Valproic acid drug detection study through the pure and doped zinc oxide nanoclusters in gas and solvent phase: Density functional theory and thermodynamic study

In this study, to explore a potential sensor for the valproic acid drug, pure and doped zinc oxide nanoclusters (Zn12O12, AlZn11O12, and, GaZn11O12) were utilized in the gas and solvent phase using the density functional theory calculations. The adsorption energies were calculated at −21.87, −39.64, and −24.73 kcal mol−1 for Zn12O12, AlZn11O12, and, GaZn11O12 complexes in their most stable configuration, respectively. Thermodynamic investigations were shown the interaction of valproic acid with the nanoclusters is spontaneous and exothermic. Sensor response investigation indicated 10.17, 6113.83, and 3.22 after the adsorption process for the Zn12O12, AlZn11O12, and, GaZn11O12, respectively. Thus, it is clear that the AlZn11O12 nanocluster demonstrated a significant sensor response. Further, the AlZn11O12 nanocluster had a practical short recovery time of 11.18 s. The solvent phase calculations indicated that these structures were stable in water. UV–vis calculation showed after the interaction of valproic acid with the AlZn11O12 spectrum shifted significantly to the higher wavelength region (red shift). Consequently, this study proposes the AlZn11O12 nanocluster as a potential candidate for valproic acid detection based on its suitable outcomes.

Grain refinement mechanism and mechanical properties of wrought Zn-0.1Mg-0.02Mn alloys by rolling at different reductions

Zinc alloys have great potential to become a new generation of biodegradable implant materials for biomedical applications due to their moderate corrosion rates. However, the poor mechanical properties restrict the application of pure zinc as biomedical materials. In this study, Zn–0.1Mg–0.02Mn alloy was rolled to different reductions at room temperature. The 80% reduction rolled alloy showed the best mechanical performance with ultimate tensile strength and elongation of 397.7 MPa and 15.9%, respectively, which satisfy the requirement of biomedical implant materials. Grain refinement mainly promoted the strength enhancement with increased rolling reductions. The microstructure evolution reveals that the basal-oriented grains and non-basal-oriented grains had different deformation mechanisms to induce DRX process during rolling. DRX could be directly accelerated in basal-oriented grains by basal slip, while twinning and de-twinning process operate to refine the non-basal-oriented grains.

Microstructural and nonlinear optical properties of quaternary gallium-titanium-zinc-oxide transparent conductive semiconductor thin films

Transparent and conductive quaternary gallium-titanium-zinc-oxide films were grown on glass substrates by radio-frequency magnetron sputtering. The effects of growth temperature on structure, morphology, electrical, and nonlinear optical properties of the films were investigated systematically. All the deposited films possess hexagonal wurtzite structure with (002) preferred crystallographic orientation. The obtained optical bandgaps of the deposited films are larger than that of pure zinc oxide, which is ascribed to the reduction in band tail width. The film deposited at growth temperature of [Formula: see text]C exhibits the optimum crystalline quality with the lowest dislocation density of [Formula: see text] nm[Formula: see text], the highest visible light transparency of 82.06%, the minimum sheet resistance of 11.2 [Formula: see text]/sq, and the maximum figure-of-merit of [Formula: see text] [Formula: see text][Formula: see text]. The present findings indicate that the gallium-titanium-zinc-oxide films are promisingly utilized as transparent conductive layer. The refractive index and extinction coefficient of the deposited films were estimated by using spectrum fitting approach. A normal optical dispersion behavior was observed in visible region, while an anomalous dispersion behavior appeared in ultraviolet region. In addition, the nonlinear optical parameters were obtained. This first-hand information is useful for future rational design of multicomponent zinc oxide semiconductor materials for optoelectronic applications.

Hydrothermal Synthesis of Boron-Doped Graphene for High-Performance Zinc-Ion Hybrid Capacitor Using Aloe Vera Gel Electrolyte

The great interest in developing emerging zinc-ion capacitors (ZIC) for energy storage applications is due to their inexpensiveness and the future necessity for hybrid electrical energy storage devices. The Zn-ion hybrid capacitor device was assembled using boron (B)-doped reduced graphene oxide (B-RGO) material, which acts as the cathode, and pure zinc metal as an anode. This research work aims to study the influence of B-doped reduced graphene oxide (B-RGO) with Aloe vera gel as an electrolyte. The reduced graphene oxide (RGO) and B-RGO electrode active materials were confirmed through X-ray diffraction (XRD), RAMAN, Fourier transformation infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM) and field emission-transmission electron microscopy (FE-TEM) analysis. The surface morphological images reveal that a few-layered nanostructure B-RGO was used in the Zn-ion hybrid capacitor device. The electrochemical performance of the Zn-ion hybrid capacitor was evaluated through cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) measurements, with a wide active potential range of 0–2 V versus Zn/Zn+. The mixture composition of Aloe vera extract and 1M ZnSO4 electrolyte generated a stable voltage and exhibited good capacitive behavior. The fabricated ZIC coin cell device with the Aloe vera gel semi-gel electrolyte containing ZnSO4 demonstrated improved Zn+ ionic exchange and storage efficiency. Moreover, the B-RGO electrode active material exhibited excellent cycle stability. The simple one-step electrochemical technique is the most suitable process for boron doping into graphene nanosheets for future energy storage applications.

Facile catalytic construction of one-pot two-component 1,3,4-oxadiazole derivatives over Zn promoted Cu/CeO3 catalysts in semi-aqueous condition

Novel Zn promoted Cu/CeO3 catalysts was investigated to the green 1,3,4-oxadiazole synthesis via two component condensation of 2-aminobenzhydrazide and aldehydes in semi-aqueous environment. FT-IR, XRD, SEM, Raman, XPS, and BET have been used to examine catalyst through structural investigation. To determine the catalyst's use, some 1, 3,4-Oxadizole compounds were produced with varied catalyst concentrations in semi-aqueous circumstances. It was thoroughly investigated how pure Cerium oxide, Zinc nitrate and Copper nitrate affect the yield and reaction time of 1, 3,4-Oxadizole derivatives. The model compound under optimized condition afforded maximum yield (96%) in just 45 min. The goal of current research is to create a cheap, reusable catalyst that can be easily handled, produces a lot of products, and reacts quickly. The produced organic molecules were further examined using FT-IR and NMR techniques to identify the synthesized compounds. Furthermore, the novel catalyst can be characterized using several analytical techniques for both the fresh and recycled ones, demonstrating that there is no activity or stability loss during four reaction cycles.

Consolidation of Zn-Hydroxyapatite and Zn-Bioactive Glass Composites Using High-Pressure Torsion

There has been a great interest in developing zinc-based composites for biological applications. Mixing bioactive particles and obtaining a well-dispersed structure is not straight forward though. The present study reports a novel processing route in which zinc particles are mixed with hydroxyapatite and bioactive glass particles and consolidated at room temperature using high-pressure torsion. The composites display good dispersion of second phase particles, enhanced strength and an increased corrosion rate in the Hank’s balanced salt solution. The incorporation of these particles can be used to tailor the corrosion rate of zinc. It is shown that the surface layer of the corrosion product in the zinc-bioactive particle composites is richer in calcium and phosphorous than the pure zinc counterpart.

Effect of metal ion on optical, photoluminescence, morphological, and photocatalytic properties of ZnS nanoparticles.

The semiconducting materials of pure zinc sulfide (ZnS), 2.5 wt%, 5.0 wt%, 7.5 wt%, and 10 wt% of Ag-doped ZnS nanoparticles were prepared using the sol-gel technique. The prepared nanoparticles were analyzed by powder X-ray diffraction (PXRD), Fourier transformed infrared (FTIR), UV-visible absorption, diffuse reflectance photoluminescence (PL), high-resolution transmission electron microscope (HRTEM), and field emission scanning electron microscope (FESEM) to study the properties of pure ZnS and Ag-doped ZnS nanoparticles (NPs). The Ag-doped ZnS nanoparticles have a polycrystalline nature, which is confirmed by PXRD analysis. The functional groups were identified by the FTIR technique. The bandgap values decrease with increasing Ag concentration compared to pure ZnS NPs. The crystal size lies between 12 and 41nm for pure ZnS and Ag-doped ZnS NPs. The presence of Zn, S, and Ag elements was confirmed by EDS analysis. Using methylene blue (MB), the photocatalytic activity of pure ZnS and Ag-doped ZnS NPs was performed. The highest degradation efficiency was observed for 7.5 wt% Ag-doped ZnS NPs.

Sacrificial Doping as an Approach to Controlling the Energy Properties of Adsorption Sites in Gas-Sensitive ZnO Nanowires

Currently, devices for environmental gas analyses are required in many areas of application. Among such devices, semiconductor-resistive gas sensors differ advantageously. However, their characteristics need further improvement. The development of methods for controlling the surface properties of nanostructured metal oxides for their use as gas sensors is of great interest. In this paper, a method involving the sacrificial doping of ZnO nanowires to control the content of their surface defects (oxygen vacancies) was proposed. Zinc oxide nanowires were synthesized using the hydrothermal method with sodium iodide or bromide as an additional precursor. The surface composition was studied using X-ray photoelectron spectroscopy. The sensor properties of the isopropyl alcohol vapors at 150 °C were studied. It was shown that a higher concentration of oxygen vacancies/hydroxyl groups was observed on the surfaces of the samples synthesized with the addition of iodine and bromine precursors compared to the pure zinc oxide nanowires. It was also found out that these samples were more sensitive to isopropyl alcohol vapors. A model was proposed to explain the appearance of additional oxygen vacancies in the subsurface layer of the zinc oxide nanowires when sodium iodide or sodium bromide was added to the initial solution. The roles of oxygen vacancies and surface hydroxyl groups in providing the samples with an increased sensitivity were explained. Thus, a method involving the sacrificial doping of zinc oxide nanowires has been developed, which led to an improvement in their gas sensor characteristics due to an increase in the concentration of oxygen vacancies on their surface. The results are promising for percolation gas sensors equipped with additional water vapor traps that work stably in a high humidity.

Modified-ZnO-mediated dye detoxification by a heterogeneous Fenton process

The continuous and unchecked discharge of effluents by the dyeing industry into water bodies has led to the rising importance of water treatment. This study focuses on the successful abatement of the auramine O (AM) dye in an aqueous system through a heterogeneous Fenton process using ultrasonication. Zinc oxide (ZnO) nanoparticles (NPs) were obtained by using a straightforward precipitation method and then modified with glycine (M-ZnO). The NP size sharply decreased upon modification with glycine. X-ray diffraction was used to determine the basic crystal properties, such as crystallinity. It was observed that the size of NPs sharply decreased from 24.6 nm (pure zinc oxide) to 17.3 nm upon modification of zinc oxide with glycine. A bandgap of 3.4 eV was determined for M-ZnO using a UV–visible spectrophotometer. Thermal gravimetric analysis revealed the excellent thermal stability of M-ZnO compared with that of zinc oxide. The catalytic activity for AM abatement was determined using a Fenton process at pH 6. Detoxification assays showed that pure hydrogen peroxide (H2O2) and pure zinc oxide exhibited 38 and 37% AM dye degradation, respectively. Meanwhile, M-ZnO showed 97% AM dye degradation in 240 min. A plausible mechanism is proposed for AM abatement using zinc oxide.

Electrochemical Hydrogen Storage Kinetics and Microstructure of the Rapidly Quenched Alloy Mg2Ni0.75Zn0.25

The Mg2Ni0.75Zn0.25 alloys are prepared from Mg2Ni as master alloy and pure Zinc ingot by remelting process in this work. The microstructures, electrochemical properties and desorption kinetics of the as-cast and melt-spun alloys are investigated. The phase compositions and microstructures of the alloys are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron backscattering diffraction (EBSD). The results show that the segregation atoms rich in Zn can inhibit the growth of Mg2Ni grains, especially the nanocrystalline grains formed in Mg2Ni0.75Zn0.25 alloy after melt-spinning process. The rapidly quenched Mg2Ni0.75Zn0.25 alloy exhibits the largest discharge performance (102.1 mAh g−1) and dehydrogenation activation energy (14.68 kJ mol−1). The improvement of the kinetic properties is related to the hydrogen diffusion rate (D) in the alloys and the charge transfer reaction on the surface. The rapidly quenched Mg2Ni0.75Zn0.25 alloy has the largest D, 6.187 × 10−11 cm2 s−1. The doping of Zn aggravates the corrosion of alloy electrodes, which destroys the oxide layer on the alloy surface, provides a channel for the diffusion of hydrogen atoms.

Machine Learning-Assisted Estimation of the Photoantioxidant Activities of Bare, Mg, Cu, and Mg/Cu Dual-Doped ZnO

Green-synthesized pure zinc oxide (ZnO), Mg-doped ZnO, Cu-doped ZnO, and Mg/Cu dual-doped ZnO using aqueous leaf extract of Ziziphus mauritiana were analyzed for their antioxidant activities. In this study, the data-driven approach has been used to estimate the photoantioxidant activities of ZnO, Mg-doped ZnO, Cu-doped ZnO, and Mg/Cu dual-doped ZnO based on the experimental data and synthetic data generated through simulations. Three different machine learning models, including artificial neural network, extreme gradient boosting, and automated machine learning, were explored and compared for both data sets. These models were validated by using external validation and applicability domain methods based on the values of coefficient of determination, root mean square, and mean absolute errors. The performance of the machine learning techniques showed that photoantioxidant activities could be predicted accurately from the input variables such as types of dopants, percentage of dopants, average crystallite size, lighting condition, and concentration of antioxidants (photocatalyst). Doping and the lighting condition were found to have a more significant impact on the values of photoantioxidant activities of the ZnO, Mg-doped ZnO, Cu-doped ZnO, and Mg/Cu dual-doped ZnO in comparison to other variables. Based on three artificial neural network models, the variables for Mg doping and the lighting condition had weights with values ranging between 1.1 and 2.9.

Synthesis of copper-doped indium zinc sulfide nanosheets for high efficiency photocatalytic hydrogen production

The excessive use of fossil energy has caused a series of environmental problems. Hydrogen is a green energy substitute for fossil energy, and photocatalytic hydrogen production is an effective means of hydrogen production. Indium zinc sulfide catalyst has great application prospect in the field of photocatalysis due to its advantages of high stability and visible light absorption. Based on this, Cu doped indium zinc sulfide nanosheets were prepared in this paper. Compared with pure indium zinc sulfide nanosheets, copper doped indium zinc sulfide nanosheets have better photocatalytic hydrogen production performance. The design and synthesis of photocatalytic hydrogen-producing catalyst has important guiding significance.

Novel Laser-Assisted Chemical Bath Synthesis of Pure and Silver-Doped Zinc Oxide Nanoparticles with Improved Antimicrobial and Photocatalytic Properties

Antimicrobial resistance poses a significant threat to global health, amplified by factors such as water scarcity and suboptimal hygienic practices. Addressing AMR effectively necessitates a comprehensive strategy encompassing enhanced access to potable water, developing innovative antibiotics, and exploring alternative treatment modalities, such as harnessing solar photocatalysis with zinc oxide nanoparticles for water purification and antimicrobial applications. The Laser-Assisted Chemical Bath Synthesis (LACBS) technique facilitates the fabrication of pure ZnO nanostructures, providing a potentially efficacious solution for mitigating pathogen proliferation and managing wastewater. The photocatalytic degradation of MB and MO dyes was investigated using blue laser light at 445 nm, and degradation rates were determined accordingly. Ag-doped ZnO nanostructures were characterized through X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and Fourier-transform infrared spectroscopy. The antimicrobial efficacy of LACBS-synthesized ZnO nanoparticles was assessed against C. albicans, S. aureus, B. subtilis, E. coli, and K. pneumoniae using the disc diffusion method, revealing 40 mm, 37 mm, 21 mm, 27 mm, and 45 mm inhibition zones at the highest concentration of doped-Ag (4.5%), respectively. These inhibition zones were measured in accordance with the guidelines established by the Clinical and Laboratory Standards Institute. X-ray diffraction patterns for ZnO, ZnOAg(1.5%), ZnO:Ag(3%), and ZnO:Ag(4.5%) samples revealed variations in intensity and crystallinity. Scanning electron microscopy exposed morphological disparities among the nanostructures, while energy-dispersive X-ray spectroscopy verified their elemental compositions. UV-Vis absorption analyses inspected the optical band gaps, and Fourier-transform infrared spectra identified the stretching mode of metal-oxygen bonds. Under blue laser irradiation, Ag-doped ZnO exhibited enhanced photocatalytic activity during the photocatalytic degradation. These nanoparticles, synthesized via the cost-effective and straightforward LACBS method, benefit from silver doping that augments their electron-trapping properties and photocatalytic activity, thereby enabling efficient dye degradation. Consequently, Ag-doped ZnO nanoparticles hold promise as a potent solution for counteracting drug-resistant microorganisms and as an effective disinfectant.

A novel heterostructure ZnO/PbBiO2Cl as a type-II photocatalyst for persulfate activation in tetracycline degradation under visible light

In the present study, the novel ZnO/PbBiO2Cl heterostructure nanocomposite was fabricated by the simple hydrothermal method. The synthesized nanocomposite was applied to remove tetracycline (TC) in the photocatalytic process under visible light. Different analyses (XRD, FTIR, EDX, DRS, BET, TEM, FESEM, and PL) were carried out to determine the characterization of materials. The results showed that compared to pure zinc oxide, the ZnO/PbBiO2Cl (40%) sample has excellent efficiency in TC degradation, which is about 97% in 150 min. Also, the effect of parameters such as initial TC concentration, solution pH, and catalyst dosage was evaluated. After that, ZnO/PbBiO2Cl photocatalyst was used for persulfate (PS) activation. The kinetic study showed that the reaction rate constant in the ZnO/PbBiO2Cl (40%) + PS system is approximately 23 and 4 times faster than ZnO and ZnO/PbBiO2Cl (40%) samples, respectively. Furthermore, the complete TC removal was achieved in 50 min. Finally, by identifying the active species and using the optical properties of photocatalysts, the degradation mechanism was predicted. Accordingly, it is expected that by using highly stable ZnO/PbBiO2Cl photocatalysts, TC pharmaceutical pollutants can be removed with high efficiency.

Effects of Different CO2 Concentrations and Degradation Media on Static Corrosion of Commercially Pure Zinc

Zn alloys have lately captivated the attention of the scientific community as possible materials for cardiovascular applications, showing a corrosion behavior and mechanical properties in between of those of Mg and Fe alloys. To better understand the different aspects of the interaction of Zn with body fluids, the basic corrosion pattern and the degradation products’ formation were investigated considering the effect of CO2 amount in the atmosphere and different pseudo-physiological media; that is Hanks’ balanced salt (HSS), Dulbecco’s phosphate-buffered saline (PSS) and physiological saline solution (NSS), through a 14-day static immersion study. A mixed degradation layer mainly composed of ZnO with Zn3(PO4)2·4H2O and Zn(CO3)2 precipitates was found on surfaces immersed in both HSS and PSS, independently of the atmosphere, while a ZnO/ZnCl2 layer was found on the surface immersed in NSS, which also revealed the higher corrosion rate due to the effect of Cl− ions. Samples tested under a CO2-rich atmosphere showed a more compact passivating layer, higher dimensions crystals and less cavities when tested in HSS, PSS and NSS, respectively.

Mn- and Fe-spinels' formation through sintering of pure and waste materials: Mechanical, electrical and magnetic properties

This study focuses on fabrication of some spinel composites from pure and waste materials for electronic and magnetic applications. Six batches were designed from pure MgO, ZnO, Fe2O3, MnO2 and iron oxide extracted from alum sludge. The designed batches were sintered at 1250 and 1350 °C then investigated for their phase composition, microstructure, physical, mechanical, electrical and magnetic properties. The results indicated that, after sintering at 1350 °C, all batches formed spinel structures as main phases. The formed spinel structures were MgFe2O4, MgMn2O4, ZnMn2O4 and ZnFe2O4, in addition to some minor pervoskite structures. The batch that prepared from pure manganese and zinc oxides (B4), formed ZnMn2O4 spinel and exhibited the best densification parameters (bulk density; 4.7 g/cm3 and apparent porosity; 10%) as well as highest hardness (4.53 GPa). On the other hand, the specimen that fabricated from pure MgO, MnO2 and Fe2O3 (B2) formed MgFe2O4 and MgMn2O4 spinel structures and exhibited the highest electrical resistivity (1.3E + 09 Ohm.cm) as well as highest saturation magnetization (Ms = 24.948 emu/g).