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Modified coincidence Doppler broadening spectroscopy (MCDBS) was used in this study to investigate the electron band structure of zinc aluminate (ZnAl2O4/ZAO). The effect of single and co-doping metal elements on the band structure of valence and core electrons was investigated. At the low momenta range, the annihilation of the maximum number of positrons has been done by the electrons of the pure sample, which indicates more annihilation by valence electrons; in contrast, with the addition of metals, the annihilation of positrons is also done by core electrons. The sample containing silver shows the highest participation of core electrons in the process of positron annihilation. If silver and erbium are simultaneously doped in the sample, the highest participation of electrons in the annihilation of positron occurs in values of momentum of about 15 × 10–3 mOc. Using a new arrangement in electronic panels in the MCDBS allows the detection and study of more energetic momentum of core electrons. [ABSTRACT FROM AUTHOR]

Abstract MgFe2O4@ZnAl2O4 magnetic nanocomposites were synthesized with the easy and green sol–gel method, and their photocatalytic efficiency was followed toward degradation of reactive blue 222 (RB222) dye under visible light irradiation. Prepared nanocomposites were fully characterized. The SEM and TEM images revealed the spherical morphology of the produced nanocomposites, with average size of 20–25 nm. The XRD pattern of sample exhibited the successful synthesis of the MgFe2O4@ZnAl2O4 MNCs with crystallite size 13 nm. The saturation magnetization (Ms) of the nanocomposites was examined using VSM, indicating a value of 6.59 emu/g. The absence of Hc and Mr values confirms the superparamagnetic nature of the nanoparticles. In addition, the surface area was calculated to be 78.109 m2/g utilizing BET analysis, and the band gap was determined to be 1.88 eV by DRS analysis. The photocatalytic, photolysis, and adsorption performance were investigated and result shown photodegradation activity was higher than others. These results confirm the synergetic effect between the MgFe2O4@ZnAl2O4 MNCs and visible light irradiation to degradation of organic dye. The results indicate that rapid degradation of 96% of RB222 dye occurred in just 10 min, with a TOC removal rate of approximately 59%. Furthermore, radical scavenger agents also clarified photodegradation of RB222 dye.

MgFe2O4@ZnAl2O4 magnetic nanocomposites were synthesized with the easy and green sol–gel method, and their photocatalytic efficiency was followed toward degradation of reactive blue 222 (RB222) dye under visible light irradiation. Prepared nanocomposites were fully characterized. The SEM and TEM images revealed the spherical morphology of the produced nanocomposites, with average size of 20–25 nm. The XRD pattern of sample exhibited the successful synthesis of the MgFe2O4@ZnAl2O4 MNCs with crystallite size 13 nm. The saturation magnetization (Ms) of the nanocomposites was examined using VSM, indicating a value of 6.59 emu/g. The absence of Hc and Mr values confirms the superparamagnetic nature of the nanoparticles. In addition, the surface area was calculated to be 78.109 m2/g utilizing BET analysis, and the band gap was determined to be 1.88 eV by DRS analysis. The photocatalytic, photolysis, and adsorption performance were investigated and result shown photodegradation activity was higher than others. These results confirm the synergetic effect between the MgFe2O4@ZnAl2O4 MNCs and visible light irradiation to degradation of organic dye. The results indicate that rapid degradation of 96% of RB222 dye occurred in just 10 min, with a TOC removal rate of approximately 59%. Furthermore, radical scavenger agents also clarified photodegradation of RB222 dye. [ABSTRACT FROM AUTHOR]

For the first of its kind ZnAl 2 O 4 : Ag (1–11 mol % ) nanomaterials (NMs) are synthesized using Tulsi leaves extract (calcination at 500 ∘ C) and subjected to characterization. Structural and electrochemical properties are analyzed. Cubic structure is verified by the Bragg reflections. Both crystallite size and direct energy band gap was found to decrease with an increase in dopant concentration. On the surface morphology, there are numerous pores and hollows. The galvanostatic, CV, EIS spectra, Discharge profile and Cyclic life profile was performed for ZnAl 2 O 4 : Ag (1 and 11 mol % ) NPs. The CV analysis showed only a pair of oxidation peaks and only one reduction peak. According to records, the precise discharge and charge capabilities are 242/214, 196/184, 161/151, 140/126 and 126/115 at 0.1, 0.25, 0.5, 1 and 2.5 C respectively. Additionally, at 2.5 C, the ZnAl 2 O 4 : Ag (1–11 mol%) anode exhibits the greatest cycle stability and Columbic efficiency even after 1000 cycles of cycling. [ABSTRACT FROM AUTHOR]

The paper breaks the general concepts and shows that pore formation is possible in anodic aluminum barrier oxide by anodizing of pure Al, and also presents the results of electrochemical anodizing in boric acid and citrate buffer aqueous solutions of homogeneous binary alloys AlCu (4 wt.%), AlZn (3 wt.%) and AlAg (5.2 wt.% and 16.2 wt.%). Barrier anodizing allowed obtaining Al2O3 thin films doped with copper, zinc and silver. The anodizing behavior and the effect of anodic current density on the charge were studied, and scanning electron microscopy, X-ray photoelectron spectroscopy and Auger electron spectroscopy analyses were performed. The doped alumina thin films, which are a mixture of Al2O3, Cu2O, ZnO, Ag2O, AgO and promising double metal oxides CuAlO2, AgAlO2 and ZnAl2O4, are promising for use as resistive switching, photoelectron, mechanical, photo-thermoelectric and fluorescence materials; sensors; and transparent conductive and photocatalyst films. [ABSTRACT FROM AUTHOR]

The high hot strength of MgO–Cr2O3 refractory is often ascribed to its intimate aggregate/matrix bonding. For a fundamental comparison with it, ∼2 mm aggregates of MgO and Al2O3 were separately embedded in ZnAl2O4 and MgAl2O4 matrices, sintered at 1600°C, and examined. It was found that similarity of thermal expansion coefficient (TEC) between the aggregate and the matrix is critical to achieve good bonding and this is more important than the extent of interdiffusion. The TEC mismatch of ≥5.7 × 10−6 K−1 caused significant undesirable debonding in MgO aggregate/MgAl2O4 matrix sample and MgO/ZnAl2O4 despite >736 μm Zn2+ diffusion depth in the latter. Direct bonding, as inferred from a thicker interfacial reaction layer and a greater shift of the aggregate/matrix interface before and after firing, was better in MgAl2O4/ZnAl2O4 combination, followed by tabular Al2O3/ZnAl2O4 and Al2O3/MgAl2O4. Powder X‐ray diffraction indicated that the volatilization of ZnAl2O4 at 1600°C in air was negligible compared to MgO–Cr2O3. [ABSTRACT FROM AUTHOR]

Fast and continuous growth in the market of energy storage systems has increased the demand for powerful cathode materials with excellent electrochemical characteristics. In this scene, the micron-sized particles of commercial NMC811 electrode were decorated with ZnAl2O4 nanoparticles via facile coprecipitation method. The slight shifts in XRD peaks to higher angles and in FTIR bands to lower frequencies confirm the formation of ZnAl2O4 coating film surrounding NMC811 particles. The morphological features of ZAO@NMC811 core-shell particles were deeply investigated by FESEM/EDS and HRTEM/SAED techniques. XPS results of the coated sample revealed the co-existence of Zn2+ and Al3+ ions on the surface of NMC811 structure. The charge and discharge capacities of modified NMC811 were significantly increased by 5.7 and 9% achieving about 221 and 188.5 mAhg−1, respectively after first cycle. The reduction in the separation potentials of both anodic and cathodic CV scans gives a strong indication for enhancing the structure stability and lowering the polarization between NMC811 particles after coating. The modified NMC811 exhibited higher capacity retention ∼82% than that ∼ 60.2% of pristine NMC811 after 100 cycles upon 1 C. EIS results of both types of cells elucidated the enhancement of electronic and ionic conductivity as well as Li+ ions diffusion for ZAO@NMC811 cell after cycling. The suggested ZAO coating material is cheaper, easily fabricated and considerably improved the electrochemical performance of pure NMC811 cathode compared to the reported coating materials.

As the demand for sustainable energy sources expands, the production of biodiesel has attracted great attention. The development of effective and ecologically friendly biodiesel catalysts has become an urgent need. In this context, the goal of this study is to develop a composite solid catalyst with enhanced efficiency, reusability, and reduced environmental impact. For that, eco-friendly, and reusable composite solid catalysts have been designed by impregnating different amounts of zinc aluminate into a zeolite matrix (ZnAl2O4@Zeolite). Structural and morphological characterizations confirmed the successful impregnation of zinc aluminate into the zeolite porous structure. Catalytic experiments revealed that the catalyst containing 15 wt% ZnAl2O4 showed the highest conversion activity of fatty acid methyl esters (FAME) of 99% under optimized reaction conditions, including 8 wt% catalyst, a molar ratio of 10:1 methanol to oil, a temperature of 100 °C, and 3 h of reaction time. The developed catalyst demonstrated high thermal and chemical stability, maintaining good catalytic activity even after five cycles. Furthermore, the produced biodiesel quality assessment has demonstrated good properties in compliance with the criteria of the American Society for Testing and Materials ASTM-D6751 and the European Standard EN14214. Overall, the findings of this study could have a significant impact on the commercial production of biodiesel by offering an efficient and environmentally friendly reusable catalyst, ultimately reducing the cost of biodiesel production. [ABSTRACT FROM AUTHOR]

Undoped znc aluminate (ZnAl2O4) nanocrystals were prepared via microwave combustion using natural black pepper extract as fuel. We present the effect of annealing temperatures on the luminescence, structural, and optical properties of zinc aluminate nanocrystals. The samples were chemically and structurally characterized by different techniques including x-ray diffraction, energy dispersive x-ray spectroscopy, Fourier-transform infra-red, and Raman spectroscopy. Further, the optical and luminescence behavior was studied by diffuse reflectance and photoluminescence measurements. The results indicated the formation of normal spinel, single phase ZnAl2O4 with the size in the range 8–22 nm changed by the annealing temperature. No structural transformation was observed after annealing up to 900°C. The presence of Zn-O, Al-O, and Al-Zn bonds and the change in the bond length of the Zn-O bond after annealing the zinc aluminate spinel revealed the existence of certain antisite defects. The annealed zinc aluminate nanocrystals presented an improvement in optical reflectivity (86%) in the visible region and a strong absorption band near 220 nm. In the photoluminescence study, emission bands in the violet-blue regions with weak emission in the green region were observed under UV excitation wavelengths. It was found that the annealing temperature influences a major impact on defects formation and defect-related luminescence characteristics. A significantly enhanced broad blue emission band centered at ~ 450 nm was dominant after thermal treatment, confirmed by the CIE diagram. The possible electronic transitions are presented and discussed by an energy-level diagram. The average decay time of the ZnAl2O4 nanocrystals annealed at 900°C measured by photoluminescence decay was 0.21 ms. Thus, prepared ZnAl2O4 nanocrystals can be potentially applied for solid-state lighting as blue-emitting luminescent material and for biosensing applications. [ABSTRACT FROM AUTHOR]

This study describes the use of novel Cu/ZnO/ZnAl2O4/PAAH (PAAH=polyacrylic acid) hybrid nanomaterials for glycerol hydrogenolysis. Their elaboration by sol‐gel process either in one step or in two steps allowed to modulate their structural properties in terms of specific surface area, Lewis acidity, sizes and dispersion of copper nanoparticles. The presence of PAAH and aluminium during the synthesis particularly showed benefits in terms of dispersion and metal‐support interaction. The characterization of the catalyst surfaces in composition and size of the copper nanoparticles allowed to establish structure‐reactivity relationships. Their optimization allowed to reach remarkable conversions up to 96 % with selectivity towards 1,2‐propanediol of 83 %. A recyclability study also showed a possible reuse of these catalysts after a reactivation step. [ABSTRACT FROM AUTHOR]

ZnAl 2 O 4 has recently been reported to enhance thermomechanical properties and slag corrosion resistance of refractory castables. The pore generation and deleterious expansion during in situ ZnAl 2 O 4 formation can limit their amount in a refractory composition. A comprehensive dilatometric study is presented, identifying the optimum raw materials and processing conditions. Preformed ZnAl 2 O 4 refractory aggregates were synthesized from industrial ZnO and reactive Al 2 O 3 by two-stage firing at 1050 ℃ and 1700 ℃ resulting in 0% open porosity. The ZnAl 2 O 4 powder calcined at 1050 ℃ is also a good refractory matrix material as it has better sinterability than preformed refractory-grade MgAl 2 O 4 and calcined alumina. The thermal expansion coefficient of ZnAl 2 O 4 aggregate in the range of 70–1600 ℃ was found to be 10.7 × 10−6 K−1, which is similar to tabular Al 2 O 3 (10.3 × 10−6 K−1) and MgAl 2 O 4 (10.3 × 10−6 K−1), but lower than dead burned MgO (16.4 × 10−6 K−1), creating the possibility of developing thermal shock resistant refractories by utilizing this mismatch. [ABSTRACT FROM AUTHOR]

Zinc aluminates form a niche class of ceramics, which are useful in various applications, including photoelectronic devices, catalysts, and high efficacy optical materials. Selecting appropriate starting precursors is the key impertive to control synthetic parameters in ceramics syntheses for the improvement of phase purity and corresponding physicochemical properties. The current study reports the successful preparation of high crystallinity and purity of ZnAl 2 O 4 via thermal decomposition of the metal complex precursor using triethanolamine (TEA) as the additive and chelating agent. The effects of calcination temperatures and the existence of TEA on the formation of the desired ZnAl 2 O 4 and the suppression of ZnO impurity are thoroughly investigated. Herein, the correlation between the in-depth analysis of the thermal decomposition profile of the mixed metal-TEA precursor and the characteristic features of the obtained ZnAl 2 O 4 product are highlighted. The variation of optical bandgap energy of the derived materials by controlling the structural defects via a variation of synthetic parameters is explored. The obtained results show strong evidence that the ZnAl 2 O 4 powders derived from the thermal decomposition of the mixed metal-TEA precursor are superior in terms of crystallinity, phase purity, and optical properties to those without using the TEA chelating agent. [ABSTRACT FROM AUTHOR]

Materials in nanoscale dimensions have a high surface-to-volume ratio, and thus have better reactions with other materials. The development of nanotechnology over the past decades has opened up opportunities for discovering the antibacterial effects of metallic nanoparticles. In this study, the antibacterial properties of nanoparticles on aluminate (ZnAl2O4) were studied on Escherichia coli and Pseudomonas aeruginosa bacteria. Antibacterial activity was assessed by using the disk diffusion method on agar using nanoparticles on synthesized aluminate. The non-growth halo diameter indicates the sensitivity of bacteria to antimicrobials. The minimum inhibitory concentration of bacterial growth (MIC) and minimum bacterial leaching concentration (MBC) was measured by microdilution in sterile tubes. Statistical analysis was done by T-test. The results of this study showed that Pseudomonas aeruginosa sensitivity (16.06±1.8mm) was higher than E. coli (11.64±2.2mm) (p < 0.05). The minimum inhibitory concentration (MIC) and bactericidal concentration MBC of bacteria Pseudomonas aeruginosa and Escherichia coli bacteria MIC and MBC was lacking. According to the results obtained in this study, we conclude that Pseudomonas aeruginosa was more sensitive to alumina than that of E. coli against nanoparticles.

The use of heterogeneous catalysts in the transesterification reaction is an eco-friendly and cost-effective approach for biodiesel production as compared to the homogeneous catalyst-based processes. In this study, a heterogeneous cobalt doping Zn/Al complex oxide was prepared by a simple birch-templating method, and successfully applied to the transesterification of jatropha oil with methanol. The catalyst had strong diffraction peaks of ZnAl 2 O 4 spinel crystal with substitutional doping of amorphous cobalt atom. It had a tendency to achieve a high base strength whilst increasing the specific surface area in the presence of cobalt. By contrast to the impregnation and coprecipitation methods, the crystalline particles from templating method were uniformly distributed on the catalyst surface, thus forming a well-defined tiled network with large amounts of grain-free pores. The exposure of available activity sites resulted in a biodiesel yield of 91.4%. After used several times and recycled, the regenerated catalyst also exhibited good catalytic potency without obvious deactivation. The transesterification kinetics satisfied the Pseudo first order model that controlled by the reaction temperature and catalyst dosage. The thermodynamic parameters of Δ H of 16.7 kJ/mol, Δ S of −284.6 J/mol/K, and Δ G of 140.0 kJ/mol suggested an endothermic, endergonic, and non-spontaneous nature of the reaction. [Display omitted] • Co doped Zn-Al spinel was prepared for biodiesel production by different methods. • Templating method had high specific surface area with pores evenly distributed. • Efficient biodiesel yield above 90% was achieved with low levels of residual metal. • The catalyst exhibited good catalytic potency and reusability after reactivation. • Kinetic and thermodynamic properties of biodiesel production were assessed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co/ZnAl 2 O 4 catalysts for the combustion of propane and naphthalene are studied. • The promoter effect of Rh on Co/ZnAl 2 O 4 catalysts is investigated. • Different catalysts were prepared, characterized and tested. • The addition of rhodium generates changes in various physicochemical properties. • The catalysts are active for the propane an naphthalene combustion. Zinc aluminate (ZnAl) was used as support to obtain a series of rhodium-modified Co-ZnAl catalysts for the catalytic oxidation of propane and naphthalene. The catalysts were characterized by various techniques including N 2 adsorption (BET), X-ray diffraction (XRD), temperature programmed reduction (TPR), diffuse reflectance spectroscopy (DRS), FTIR and X-ray photoelectron spectroscopy (XPS), to correlate chemical and physical characteristics with catalytic properties. TPR and XPS techniques show the presence of segregated cobalt compounds, as well as cobalt species interacting with the support. Segregated cobalt species are considered responsible for the catalytic activity, due to their high reducibility. The addition of Rh promotes the reducibility of the cobalt compounds yielding to an increase in the surface content of Co2+. For propane oxidation, the best activity shown by the Rh(0.5)Co(5)-ZnAl sample could be associated with a synergic effect between rhodium and cobalt species. No specific effects were revealed due to the addition rhodium for the naphthalene oxidation. [ABSTRACT FROM AUTHOR]

Optically transparent samples of ceramic materials based on the magnesium aluminate and zinc aluminate spinels of density close to the theoretically attainable one have been obtained, and their heat conductivity was measured in the temperature range 50–300 K. It is shown that the heat conductivities of these ceramic materials at room temperature are close and fall within the range 17–18 W/(m·K). At a cryogenic temperature (T = 50 K), the heat conductivity of the ceramic materials based on the zinc aluminate spinel (180 W/(m·K)) is much higher than the heat conductivity of the ceramic materials based on the magnesium aluminate spinel (122 W/(m·K)). The absolute heat conductivities of the ceramic materials based on the indicated spinels are dependent on the sintering additives used in their production. [ABSTRACT FROM AUTHOR]

In this work, zinc aluminate spinel was prepared by two methods of directly synthesis (without calcination): microwave assisted combustion and hydrothermal method. The materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and N2-adsorption/desorption isotherms. The XRD patterns confirmed the formation of cubic ZnAl2O4 spinel structure with no secondary phases for both synthesis routes, whereas the hydrothermal method yielded powders with crystallite size 3 times smaller (6.9 nm), as compared to the powders produced by microwave assisted combustion method (25.6 nm). The micrographs revealed agglomerated powders with plate-like morphologies for both routes. Nitrogen adsorption/desorption isotherms (BET) revealed higher surface area (183 m2.g-1) and greater pore volume (0.173 cm3.g-1) for ZnAl2O4 powders prepared by the hydrothermal method.

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ZnAl _2 O _4 with spinel structure has attracted more attentions due to its robust dielectric and luminescence properties. Complex cation distribution in spinel structure influences the optical and magnetic properties. Herein, we report white emission related to the defects and the magnetism assigned to Fe impurity in ZnAl _2-x Fe _x O _4 ( $0\leqslant x\leqslant 0.6$ ) nanocrystals fabricated by using common sol-gel method at a relatively lower temperature (700 °C) than that reported earlier. ZnAl _2-x Fe _x O _4 phosphors reveal single spinel phase without impure phase. Complex cation distribution is observed in all samples, for instance, Fe and Zn in antisites, cation vacancies, and with Fe content increasing, cation distribution reveals obvious change. The band gap energy of ZnAl _2-x Fe _x O _4 phosphors is reduced from 3.84 eV to 3.33 eV when the content of Fe ions (x value) increases from 0 to 0.6. Two wide band emissions assigned to the various types of shallow and deep donor/acceptor defects are observed, monitoring with the excitation wavelength of 280 nm. The Commission International de I’Eclairage (CIE) colour coordinate (x, y) of the ZnAl _2-x Fe _x O _4 phosphors is found to shift from (0.3218, 0.2957) to (0.3422, 0.3122) with Fe doping in spinel lattices owing to rearrangement of defects, indicating the potential application in white-light illumination. ZnAl _2-x Fe _x O _4 reveals a room ferromagnetism resulting from Fe3 + ions in spinel lattices.

Abstract Ce3+, Eu3+ and Tb3+ singly and triply doped ZnAl 2 O 4 nano-powders were successfully synthesized via the citrate sol-gel method. X-ray diffraction (XRD) analysis showed that the powder samples consisted of the cubic crystalline phase. Energy dispersive X-ray spectroscopy (EDS) results confirmed the presence of all expected elements and the EDS map showed that the foreign ions were distributed homogeneously on the surface. Scanning electron microscopy (SEM) results revealed that the prepared powder morphology was influenced by doping. The transmission electron microscopy (TEM) results confirmed that the prepared powders were in the nano-scale region. The ultraviolet–visible (UV–vis) spectra showed that different dopants and varying the Tb3+ concentration influenced the effective band gap (E g) of the host. The photoluminescence (PL) results showed that the emission at 395 nm was due to the defects emission within the host material. Ce3+ doped samples showed a broad emission peak centered at 425 nm which is attributed to the 5d → 4f transition of Ce3+ ions. The sample doped with Eu3+ showed two emission peaks at 592 and 616 nm ascribed to the 5D 0 → 7F 1 and 5D 0 → 7F 2 transitions of Eu3+ ions, respectively. Tb3+ singly-doped sample showed four peaks located at 489, 545, 587 and 616 nm, which were respectively ascribed to 5D 4 → 7F 6 , 7F 5 , 7F 4 and 7F 3 transitions of Tb3+ ions. The Commission Internationale de l'Elcairage (CIE), or International Commission on Illumination, co-ordinates showed that the emission colour could be tuned by varying the Tb3+ concentration. Highlights • Ce3+, Eu3+ and Tb3+ doped and triple doped ZnAl 2 O 4 nano-powders were successfully synthesized via the citrate sol-gel method. • Energy dispersive X-ray spectroscopy (EDS) results confirmed that the samples were made up of Zn, Al, O, Ce, Eu and Tb ions. • The transmission electron microscopy (TEM) results confirmed that the prepared powders were in the nano-region. • The ultraviolet–visible (UV–vis) spectra showed that different dopants and concentrations of Tb3+ influenced the bandgap of the host material. • The photoluminescence (PL) results showed that there are emissions peaks from each dopant. [ABSTRACT FROM AUTHOR]

Abstract: The influence of surface modification with various concentrations of zinc acetate solution on the structural and optical properties of ZnAl2O4:Cr3+ particles was studied. The X-ray diffraction peaks assigned to the spinel structure of ZnAl2O4:Cr3+ powders revealed a tiny shift towards the lower angle, and ZnO phase was detected when ZnAl2O4:Cr3+ crystals surface was modified. The results of X-ray photoelectron spectra confirmed that the antisite defects related to tetrahedral Al existed in the surface lattices of zinc aluminate crystals. The signal intensity of XPS assigned to tetrahedral Al decreased after surface modification, while that of XPS assigned to octahedral Zn increased. The results of transmission electron microscope showed that the surface lattices of ZnAl2O4:Cr3+ particles became more ordered after surface modification, and zinc oxide nanocrystals were observed as a coating layer or dispersed particles surrounding ZnAl2O4:Cr3+ particles when the concentration of Zn(AC)2 solution increased up to 1.5 mol/L. The red emission assigned to Cr3+ ions in spinel lattices was detected at room temperature, and the emission intensity was enhanced when ZnAl2O4:Cr3+ crystals was modified. While the emission intensity was reduced when the concentration of Zn(AC)2 solution increased up to 1.5 mol/L.ZnAl2O4:Cr3+ crystals were modified by using with various concentrations of zinc acetate (0.5 M, 1.0 M and 1.5 M). These crystals surfaces showed different morphologies, and the crystallinity and photoluminescence performances were enhanced. The crystallinity of ZnAl2O4:Cr3+ crystals is improved by using surface modification.The defects transform from AlZn to ZnAl after surface modification.The PL intensity is 2.5 times than that of crystals without surface modification [ABSTRACT FROM AUTHOR]

We propose a procedure to remove lead (Pb) via catalytic chelation using peracetic acid (PAA) catalyzed using zinc aluminate (ZnAl2O4) prepared at different calcination temperatures of 900, 1,000, and 1,100 °C. In addition, their characterization in terms of the thermogravimetry analysis‐differential thermal analysis (TGA‐DTA), X‐ray diffraction (XRD), field‐emission scanning electron microscopy‐energy dispersive X‐ray analysis (FESEM‐EDX), Brunauer–Emmett–Teller (BET) analysis, Fourier transform infrared spectroscopy (FTIR), inductively coupled plasma mass spectrometry (ICP‐MS), and X‐ray photoelectron spectroscopy (XPS) was achieved. Moreover, response surface methodology (RSM) was employed for modeling. This study confirms that the properties of ZnAl2O4 are highly influenced by the calcination temperature. In addition, up to 95.3% of Pb can be removed using the proposed approach by employing optimum parameters such as temperature, pH, treatment time, PAA concentration, catalyst loading, and dissolved oxygen. We propose a procedure to remove lead (Pb) via catalytic chelation using peracetic acid (PAA) catalyzed by zinc aluminate (ZnAl2O4) prepared at different calcination temperatures. Up to 95.3% of Pb can be removed by employing optimum parameters such as temperature, pH, treatment time, PAA concentration, catalyst loading, and dissolved oxygen. [ABSTRACT FROM AUTHOR]

The conversion of ethanol over a commercial ZnAl2O4 has been investigated. The catalyst has been fully characterized by XRD, IR, UV-Vis-NIR, ICP-OES, EDX-FE-SEM, BET and porosimetry. The catalyst is active in converting ethanol. At low conversion, diethyl ether is the main product while at higher conversions acetaldehyde is the main product (max yield ~ 50%). Ethylene and ethyl acetate are coproduced. Acetone and propylene become relevant products at complete conversion. The mechanism of formation of the products is discussed based on infrared surface chemical data, thermodynamic and kinetic data. Two independent catalytic sites exist, one for dehydration, the other for dehydrogenation, similar to those of Zinc oxide, giving rise to two parallel reaction sequencies. Criteria for developing selective catalysts towards dehydrogenation products are briefly discussed. [ABSTRACT FROM AUTHOR]

Cadmium-substituted ZnAl 2 O 4 (Cd x Zn (1- x) Al 2 O 4 , where x = 0, 0.1, 0.3, and 0.5) nanoparticles were synthesized by the microwave combustion process. The XRD analysis confirmed the cubic system. The crystallite size of Cd2+ doped ZnAl 2 O 4 isin the range between 20.82 and 15.12 nm. Fourier transform infrared (FT-IR) spectra are displayed the stretching frequencies. The energy gap values decrease from 4.15 to 2.67 eV with increasing doping concentrations of Cd2+, which is due to the formation of sub-bands and is calculated by the Kubelka-Munk function. HR-SEM pictures showed the features of nanoclusters grain boundaries. The elemental mixing of Zn2+/Cd2+, Al3+andO2− was confirmed by EDX analysis. Magnetic properties reveal that the undoped ZnAl 2 O 4 has diamagnetism and Cd2+ doped ZnAl 2 O 4 system has superparamagnetic behaviour. The nonlinear index of refraction (10−8 cm2/W), nonlinear absorption coefficient (10−4 cm/W) and the 3rd order nonlinear susceptibility (10−6 esu) are found out by Z-scan experiments. The obtained results of optical limiting analysis confirm that these materials are viable candidates for devices like optical power limiters and optical switches. • The Cd x Zn (1- x) Al 2 O 4 (x = 0, 0.1, 0.3, and 0.5) composites were prepared via microwave strategy. • Optical, thermal, and magnetic properties of Cd x Zn (1- x) Al 2 O 4 composites were studied. • Third-order nonlinear parameters for prepared composites were obtained via Z-scan experiments. • Low limiting threshold values make these composites suitable for optoelectronic devices. [ABSTRACT FROM AUTHOR]

In this paper, zinc aluminate (ZnAlO) nanoparticles were obtained by a new synthesis method, thermal decomposition of Zn(II) and Al(III) carboxylates mixture. Complex combinations were obtained in the redox reaction between Zn(NO)·6HO, Al(NO)·9HO, and 1,3-propanediol at ~130 °C. The mechanism of Zn(II) and Al(III) carboxylates formation and decomposition was observed by thermal analysis and Fourier transform infrared spectroscopy. Zn(II) carboxylate, Al(III) carboxylate, and Zn(II) and Al(III) carboxylates mixture were annealed at different temperatures. Metal oxides synthesized from carboxylates precursors in single metal systems crystallized very well at 400 °C (ZnO) and weak at 800 °C (AlO), as shown by X-ray powder diffractometry. Homogenous mixture of Zn(II) and Al(III) carboxylates heated at 400 °C has led to a mixture of amorphous ZnO and AlO, which reacted forming at 600 °C well-crystallized ZnAlO, with mean crystallites size of 14.2 nm. The decomposition of carboxylates precursors is an appropriate method to obtain ZnAlO spinel as well-crystallized single phase at low temperatures. [ABSTRACT FROM AUTHOR]

ZnAlO:Cr crystals were synthesized by using sol-gel method at 1000 °C. The results showed that with the concentration of Cr in spinel lattices increasing, the x-ray diffraction peaks shifted toward lower diffraction angles, and the grain size revealed a rapid increase and became invariable when the Cr dopant concentration was above 0.7 mol%. All the samples showed a series of emission peaks ranging from 660 to 730 nm assigned to spin-forbidden E→A transition of Cr ions in spinel lattices. The intensity of emission peaks revealed a strong dependence on the Cr concentration. An additional emission peak at 740 nm was present when the Cr ions concentration was above 0.5%. All emission peaks were quenched when the Cr concentration reaches 1.3 mol%. The results of x-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) suggested that the Cr ions occupied the octahedral sites in spinel lattices, and with the Cr concentration increasing, the exchange interaction and coupling interaction between Cr-Cr were enhanced and the antisite defects related to Zn in octahedral sites increased. Graphical abstract: [ABSTRACT FROM AUTHOR]

In the current work, zinc aluminate and bismuth doped zinc aluminate (ZnAl 2-x Bi x O 4 , x = 0, 0.05, 0.1) spinel oxide nanoparticles were synthesized by co-precipitation method. The obtained samples were characterized by powder XRD, FT-IR, DRS, SEM-EDX and BET. Photocatalytic degradation of zinc aluminate and bismuth doped zinc aluminate nanoparticles were investigated using methylene blue as a model pollutant under UV light. 98. 28% of photodegradation of methylene blue was achieved in 150 min using the bismuth doped zinc aluminate catalyst. The reduction of 4-nitrophenol to 4-aminophenol was completed within 7 s using bismuth doped catalyst. [ABSTRACT FROM AUTHOR]

Zinc aluminate and cerium-doped zinc aluminate nanoparticles are synthesised by co-precipitation method. Ammonium hydroxide is used as a precipitating agent. The synthesised compounds are characterised by powder X-ray diffraction (XRD), Fourier transform Infrared spectroscopy (FT-IR), Ultraviolet diffuse reflectance spectroscopy (UV-DRS), Thermogravimetric analysis (TGA), Scanning electron microscopy (SEM) and Surface area measurements. The photocatalytic activity of zinc aluminate and cerium doped zinc aluminate nanoparticles are studied under the UV light and visible light taking methylene blue as a model pollutant. The amount of catalyst, concentration of dye solution and time are optimised under UV-light. Degradation of methylene blue under the UV-light is found to be 99% in 20 min with 10 mg of cerium doped catalyst. Compared to visible light degradation, the degradation of dye under UV-light is higher. Cerium doping in zinc aluminate (ZnAl 2 O 4 :Ce 3+ ) increased the photocatalytic activity of zinc aluminate. [ABSTRACT FROM AUTHOR]

Zinc based or doped ceramics have shown to be capable of increasing osteoblasts proliferation, biomineralization and bone formation. However, studies regarding the biological applications processes in ZnAl2O4 ceramic films are very scarce. For this reason, the objective of this in vitro study was to investigate the response of osteoblasts cells cultured onto ZnAl2O4 films. Our results showed a good biological response related to attachment and viability, with good cell morphology attached to the semi-spherical grains of the ceramic and the analysis of mineral-like tissue showed a high quantity of mineral deposited and organized as tiny spherical-like nodules attached to nanostructure surface of ZnAl2O4 material films. Based in our results, ZnAl2O4 films stimulated the bioactivity of osteoblasts cells and provide a microenvironment that favors cell differentiation and mineralization processes, suggesting their potential use as osteoconductive coating onto currently orthopedic and dental implants.

In this study, the effect of a low concentration additive of the metal element Praseodymium (Pr+3) on electron band structure of ZnAl 2 O 4 (ZAO) was investigated. The crystal structure of ZAO:Pr was studied by X-ray diffraction. The results of the X-ray diffraction pattern show that very little change has occurred in the peak position of the crystal structure of zinc aluminate in low concentration additive. Modified Coincidence Doppler Broadening-spectroscopy (MCDBS) was used to study the effect of dopants on electron structure of ZAO:Pr. The results of the longitudinal component of linear momentum show that the core electron bands are more affected with increasing additive concentration. Because of decreasing the effects of unwanted gamma rays in this new technique it could be possible to detect the effects of Pr dopants on electron band structure of ZAO with more details. • Core electron ban structure study by CDBS. • Modified CDBS as a new spectroscopic method. • Effect of Pr on core electron band changes of ZnAl 2 O 4 by MCDBS. [ABSTRACT FROM AUTHOR]

ZnAl 2 O 4 :Cr 3 + nanocrystals were fabricated by using solvothermal method at various temperatures ranging from 160 °C to 220 °C. The influence of sodium acetate (NaAC) on the structural, photoluminescence and magnetic properties of Cr-doped zinc aluminate ceramics was investigated. The results showed that ZnAl 2 O 4 :Cr 3 + polycrystals with sphere morphology (about 500 nm) were formed without NaAC in precursors, while after adding NaAC into the precursors, octahedral and hexagonal single crystals of ZnAl 2 O 4 :Cr 3 + were present. The PL spectra showed a series of sharp emission peaks ranging from 650 nm to 730 nm assigned to spin-forbidden 2 E g → 4 A 2g transition of Cr 3 + ions in spinel lattices corresponding to the result of EPR. Comparing to the PL spectra of ZnAl 2 O 4 :Cr 3 + nanocrystals prepared by using sol-gel method, the intensity of R lines (originating from 2 E g → 4 A 2g transition of Cr 3 + ions in normal spinel lattices) was much larger than that of N lines (originating from 2 E g → 4 A 2g transition of Cr 3 + ions in inverse spinel lattices) for all samples. The EPR and VSM results showed that with grain size increasing, the interaction between Cr-Cr ions became weaker and the ferromagnetism of ZnAl 2 O 4 :Cr 3 + nanocrystals was enhanced. [ABSTRACT FROM AUTHOR]

Zn x Al 2 O 4 :Cr 3+ (0.8 ≤ x ≤ 4) phosphors with spinel structure were prepared by using sol-gel method. The structure, morphology and photoluminescence properties were analyzed by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron paramagnetic resonance (EPR) and photoluminescence (PL). The spinel structure of ZnAl 2 O 4 was formed for all samples, and hexagonal structure of ZnO appeared in the powders with x ≥ 1.1. The results of XRD, SEM and TEM showed that the crystallinity of Zn x Al 2 O 4 :Cr 3+ phosphors was improved with increasing the value of x . The PL spectra showed a series of sharp emission peaks ranging from 650 nm to 730 nm assigned to spin-forbidden 2 E g → 4 A 2 g transition of Cr 3+ ions in spinel lattices. The most intense emission was observed in Zn 1.2 Al 2 O 4 :Cr 3+ powders, and the results of EPR showed that this enhancement resulted from the best dispersity of Cr 3+ ions in Zn x Al 2 O 4 lattices. [ABSTRACT FROM AUTHOR]

Layered solid solution materials Li 1.2 Ni 0.2 Mn 0.6 O 2 were synthesized with one sample heat treated and three other coated with ZnAl 2 O 4 with varying amounts (0.5, 1 and 2.5 wt%) at high temperature. The materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The effect of ZnAl 2 O 4 coatings on the electrochemical performance of the pristine material was evaluated from charge/discharge cycles, rate performance, and electrochemical impedance spectroscopy (EIS). The results from TEM and selected area electron diffraction (SAED) indicate that the ZnAl 2 O 4 coating assumes a spinel structure on the Li 1.2 Ni 0.2 Mn 0.6 O 2 . The discharge capacities and coulombic efficiencies of the Li 1.2 Ni 0.2 Mn 0.6 O 2 materials in the first cycle are improved with the addition of ZnAl 2 O 4 . Li 1.2 Ni 0.2 Mn 0.6 O 2 coated with 1 wt% ZnAl 2 O 4 shows the highest discharge capacity (254.3 mAhg −1 ), highest capacity retention (98.6% for 50 cycles), and best rate capability (84 mAhg −1 at 10 C). EIS indicates that the resistance of Li 1.2 Ni 0.2 Mn 0.6 O 2 electrodes decrease with the addition of ZnAl 2 O 4 consistent with the excellent rate capability. [ABSTRACT FROM AUTHOR]

Methyl ester produced by esterification of palm fatty acid distillate (PFAD) is considered as a non-toxic alternative and biodegradable source of energy. In this work, a polymeric mixed metal oxide with different (Al/(Zn + Al) molar ratio was initially synthesized as a parent mesoporous ZnAl 2 O 4 material. Then, a post-sulfonation treatment was established to prepare a polymeric solid acid SO 3 H ZnAl 2 O 4 catalyst with certain sulfonation degree. The physicochemical, structural, textural, thermal stability characteristics of the synthesized mesoporous catalysts were investigated by X-ray diffraction (XRD), surface area analysis (Brunauer–Emmett–Teller equation), Fourier transform infrared (FT-IR) spectroscopy, temperature programmed desorption (TPD) and thermogravimetric analysis (TGA). The optimized mesoporous SO 3 H ZnAl 2 O 4 catalyst possesses unique properties such as a surface area of 352.39 m 2 g −1 , the average pore diameter of 3.10 nm, a total pore volume of 0.13 cm 3 g −1 , and high acid density up to 1.95 mmol g −1 , simultaneously. The catalytic activity of the synthesized catalyst was further examined through the esterification of PFAD, containing high free fatty acid (FFA around 90%), resulted in PFAD methyl ester yield of 94.65%. The combination of unique textural properties allows the diffusion of reagents easily into inner acid sites. Moreover, the polymeric mesoporous SO 3 H ZnAl 2 O 4 catalyst was able to be reused for eight consecutive cycles without substantial losses of activity. [ABSTRACT FROM AUTHOR]

Zinc aluminate (ZAO), a member of spinel class of inorganic compounds has been of much interest of late due to its wide range of use in catalysis, optical, electronic and ceramic industries. When doped with several lanthanides, this material has proved to be a potential host matrix for phosphors. As lanthanides suffer from poor (direct) excitation and emission cross sections, the use of a co-dopant ion can help to circumvent this and extract better emission from a lanthanide doped ZAO system. In this connection, energy transfer mechanism from uranium to europium in the ZAO host was investigated by photoluminescence spectroscopic technique. It was seen that uranium gets stabilized in the hexavalent state as UO 6 6 − (octahedral uranate) where as the lanthanide ion, Eu is stabilized in its trivalent state in the ZAO host. In the co-doped system, an efficient energy transfer pathway from the uranate to europium ion was observed. Based upon emission and life time data a suitable mechanism was proposed for the energy transfer (quenching) process. It was proposed that after excitation by photons, the uranate ions transfer their energy to nearby 5 D 1 level of Eu 3 + ions which non-radiatively de-excites to the corresponding lower levels of 5 D 0 . Further this 5 D 0 level decays in a radiative mode to the 7 F manifold giving the characteristic emission profile of trivalent Eu. It was proposed that both static and dynamic types of energy transfer mechanism were responsible for this process. [ABSTRACT FROM AUTHOR]

The autoignition technique using glycine as fuel and related nitrate salts as an oxidiser is able to produce zinc aluminate spinel. The precursors were synthesised with lean and rich fuel at pH of 7.0 and the materials so obtained were calcined at various temperatures ranging from 600-1200°C. The autoignition process of precursors was studied by the simultaneous thermo-gravimetric and differential thermal analyses to determine the ignition mechanism. The calcined powders were characterised by X-ray diffraction, Brunauer-Emmett-Teller technique and transmission electron microscopy. The product contains nano-sized particles with an average size of approximately 20 nm. The XRD patterns showed the formation of ZnO in the powder obtained by the fuel-rich precursor and calcined at 600°C which disappears at 800°C due to solid-state reaction and proper crystallisation after heat treatment. The results presented here can be useful in manufacturing nano and micro-sized ZnAl2O4 on an industrial scale using the combustion technique. [ABSTRACT FROM AUTHOR]

Nanocrystalline zinc aluminate (ZnAl 2 O 4 ) doped with terbium (III) was synthesized using a chemical co-precipitation reaction followed by calcination. The system has an average crystallite size of 6.5 ± 2.0 nm, calculated by the X-ray diffraction data, which is in close agreement with the particle size determined via high resolution transmission electronic microscopy. Rietveld refinement of the X-ray powder diffraction profile of the samples confirms that the aluminum ions are substituted by terbium ions in the host lattice. The effects of the terbium concentration and particle size of the samples on their luminescence properties were studied. The photoluminescence spectra exhibited a green emission band, with an excitation wavelength of 230 nm. Technological tests in several ceramic applications confirmed that these pigments and their luminescence properties are very stable at high temperatures, and these results suggest that these pigments have the potential to be applied as satisfactory ceramic luminescent pigments. [ABSTRACT FROM AUTHOR]

Zinc aluminate (ZnAl 2 O 4 ) hosts and 0.1% Ce 3+ , x % Eu 3+ co-activated ZnAl 2 O 4 phosphor were successfully prepared at a relatively low temperature (~80 °C) using the sol–gel method. The co-activator (Eu 3+ ) concentration was varied in the range of 0≤ x ≤2 mol%, while the 0.1% Ce 3+ was kept constant. The X-ray diffraction (XRD) data revealed that all annealed samples consisted of the pure cubic ZnAl 2 O 4 structure. The estimated crystallite size was in the range of 18–21 nm in diameter. The results showed that the full width at half maximum (FWHM) increased with the increase in Eu 3+ mol%, which suggested a decrease in particle size. The nanopowder microstructure revealed that the material consisted of non-uniform sizes and the loss of lattice fringes as the Eu 3+ concentration was increased suggested the increase in strain or disorder. The photoluminescence (PL) results showed that the host, activated and co-activated nanophosphor emitted at different wavelengths. The peak shifts suggested that the luminescence might originate either from the defects in the host, Ce 3+ or Eu 3+ ions. The incorporation of the co-activator (Eu 3+ ) at higher concentration resulted in radiative energy transfer from Ce 3+ →Eu 3+ . The CIE colour coordinates showed a shift from the blue to orange region as the Eu 3+ concentration was increased. [ABSTRACT FROM AUTHOR]

Zinc aluminate (ZnAl2O4) nanopowders were synthesized by co-precipitation method using zinc chloride and aluminum chloride as starting precursors. The calcination temperature which was a crucial preparation factor was varied and its influence on relevant physical properties of the product was investigated. Structural properties of synthesized nanoparticles were investigated by X-ray diffraction, X-ray absorption spectroscopy, scanning electron microscope, and Raman spectroscopy. The results suggest that that ZnAl2O4 in spinel structure with high crystallinity can be obtained after calcination beyond specific temperature affirmed by XRD results. Raman result indicates the correlated chemical bonding relating to the formation of ZnAl2O4 structure. Meanwhile, the Zn K-edge X-ray absorption near-edge structure (XANES) spectra of these samples with different calcination temperature obtained from the synchrotron X-ray absorption spectroscopy measurement show the existence of accurate oxidation state for zinc ion (Zn2+) in the spinel crystal structure. Moreover, it is revealed that the calcination temperature has significant effect on the local environment of the zinc absorbing atoms through the interesting change of white line appearance. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Zn 0.9 Mn 0.1 Al 2 O 4 :Cr3+ phosphors with pure spinel structure were fabricated by using co-precipitation method. The influence of reducing time on the structure, photoluminescence and temperature sensing properties were investigated by using X-ray diffraction (XRD), electron paramagnetic resonance (EPR) and photoluminescence (PL). With the reducing time increasing, the diffraction peak reveals a shift toward lower angle, and the isolated six refined peaks of EPR assigned to Mn2+ in spinel lattices reveal a large increasing overlap, indicating the increasing concentration of Mn2+. A red emission assigned to 2E g →4A 2g of Cr3+ is observed, but its intensity is very tiny in the as-synthesized Zn 0.9 Mn 0.1 Al 2 O 4 phosphors, and with reducing time increasing, the emission intensity is enhanced sharply. The energy level of 2E g is split into 2E(2 A ‾) and 2E(E ‾) corresponding to 687 nm (R 1) and 689 nm (R 2) emissions due to the high crystal field in ZnAl 2 O 4 lattices. The emission assigned to Mn2+-Vo (Oxygen vacancy) at 530 nm reveals a strong temperature dependence, and the highest relative sensitivity of 2.55 %K−1 is achieved based on the luminescence integral intensity ratio of I 530nm / Mn 2+, which is higher than that based on the lifetime of 512 nm emission peak assigned to Mn2+ and based on the luminescence integral intensity ratio of the excitation peaks of I 427nm /I 530nm, indicating that the potential application in multi-reading temperature nanoprobe. [Display omitted] • The samples have good crystallinity and luminescence properties after sintered at 1000 °C. • The luminescence properties of ZnMnAlO:Cr3+ were improved by changing the reduction time. • The change of grain size affects the sensitivity of samples with different reduction time. • The relatively higher sensitivity for optical thermometry is obtained. [ABSTRACT FROM AUTHOR]