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Silver-doped zirconium ferrite (AxZ1-xFO, x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, and 1) nanoparticles (NPs) have been successfully synthesised by utilising the facile auto-combustion approach. The synthesis of NPs has been confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope with energy-dispersive spectrometer (SEM-EDS), high-resolution transmission electron microscope (HR-TEM) and Brunauer–Emmett–Teller (BET) analytical techniques. The magnetic and optical properties of synthesised AxZ1-xFO NPs have been investigated using a vibrating sample magnetometer (VSM) and UV-Visible spectroscopy, respectively. Additionally, herein the prepared magnetic NPs have been utilised for the photodegradation of hazardous colouring agents, namely, Chromotrope-FB (Chr-FB) and Ponceau-BS (PBS). The prepared NPs, particularly AxZ1-xFO, (x = 0.8), showed excellent photoresponse for photodegradation of Chr-FB and PBS having a % degradation of 99.77% for Chr-FB and 99.21% for PBS in just 40 and 45 min, respectively, under solar irradiation. The photocatalytic degradation has been determined by the electron-hole mechanism in which the electrons are transferred from the valence band to the conduction band of the photocatalyst's surface and combined with oxygen or water to form radicals. It has been found that the $$OH$$ OH radical played a significant role in the photodegradation of Chr-FB and PBSs in the presence of AxZ1-xFO, (x = 0.8). In addition, UV-Visible spectroscopy and mass spectrometry were used to analyse the degradation process. Moreover, the photocatalyst AxZ1-xFO (x = 0.8) achieved notable stability and reusability, thus making it an effective catalyst for environmental pollutant degradation. [ABSTRACT FROM AUTHOR]

A series of Z n 0.5 C o 0.25 C u 0.25 H o 0.037 F e 1.963 O 4 (ZCCHF)/Graphene nanoplatelets (GNPs) nanocomposites (where GNPs = 0 wt%, 1.25 wt%, 2.5 wt%, 3.75 wt%, 5 wt%) were prepared via sol-gel auto-combustion (SGAC) method followed by bath sonication and studied their structural, morphological, optical, dielectric, and magnetic properties. The structural analysis confirmed a single-phase crystal matrix of all the as-prepared nanocomposites. The optical analysis revealed that the energy bandgap (E g) lies within the range of 1.57 eV–1.62 eV. The dielectric analysis showed that the improvement in the dielectric constant (ε ′) and reduction in dielectric tangent loss (tan δ d) with increasing GNPs concentration from 0 wt% to 5 wt%. The real part of permeability (μ ′) was improved and magnetic tangent loss (tan δ M) was reduced with the addition of GNPs. Magnetic properties were studied at different temperatures (5 K, 300 K, and 400 K), and observed high saturation magnetization (M S), and coercivity (H C) at a low temperature (at 5 K). The low M S , and H C values were observed at high temperatures (300 K and 400 K). The combination of improved dielectric and tunable magnetic properties makes ZCCHF/GNPs nanocomposites promising candidates for applications in spintronics, high-frequency magnetic devices, and advanced electronic systems. [Display omitted] • The ZCCHF SFs and ZCCHF/GNPs nanocomposites were synthesized using a sol-gel auto-combustion (SGAC) method followed by bath sonication. • XRD analysis revealed a single-phase crystal structure and the tunable energy bandgap ranges from 1.57 eV to 1.62 eV. • The maximum dielectric constant and minimum dielectric tangent loss were found for ZCCHF/5 wt%GNPs nanocomposites. The nanocomposite with 5 wt%GNPs reveals the highest magnetic permeability around 0.995. The minimum magnetic tangent loss and skin depth was found for ZCCHF/5 wt%GNPs nanocomposites. • The saturation magnetization is lower across all temperatures with GNPs incorporation and the microwave operating frequency was 14.21 GHz at 300 K for ZCCHF/5 wt%GNPs nanocomposites. • The study highlights the multifunctional potential of ZCCHF/GNPs nanocomposites in promising candidates for a broad range of advanced technological applications. [ABSTRACT FROM AUTHOR]

Perovskites refer to ceramic materials with an ABO 3 structure. The optimization of synthesis parameters and material composition can enhance the catalytic efficiency in various chemical reactions, such as dry methane reforming. In order to highlight the differences in the catalytic properties, this study aims to compare three synthesis methods (citrate, auto-combustion and Pechini) for a same perovskite formulation namely SrZr 0·5 Ni 0·4 Fe 0·1 O 3. The crystal structure and reducibility profile are determined by XRD and TPR experiences respectively. Surface properties and composition are identified by chemisorption tests (allowing the study of basicity and nickel dispersion) and XPS analyses, respectively. Isothermal catalytic experiences from 600 to 750 °C, under atmospheric pressure and for a WHSV of 40 L / h. g together with stability tests for 25 h at 750 °C were conducted. The outcomes show the importance of properly choosing the perovskite preparation methods in order to achieve the desired surface, structural and reactivity properties. [Display omitted] • Comparison of synthesis methods for substituted perovskites SrZrO3 with Ni and Fe. • Utilisation of citrate, auto-combustion and Pechini methods. • Dry methane reforming considered as a test reaction. • Effect of the method on surface properties, crystal structure and reactivity. [ABSTRACT FROM AUTHOR]

Agricultural waste availability implies the possibility of recovering energy as biomass. The collateral effect is the production of ashes that, in some cases, have the potential to be reused in the manufacture of cement, mortar, and concrete. This article presents the study of the auto-combustion (unlike all previous studies) of corn (maize) straw (stems and leaves). The auto-combustion temperature was monitored, and the obtained corn straw ash (CSA) was characterized by means of X-ray fluorescence, X-ray diffraction, thermogravimetry, and scanning electron microscopy. Finally, the behavior of ground CSA was analyzed in both the fresh state by measurement of workability on the spreading table and the hardened state by compressive strength measurement on mortars in which 10% of ordinary Portland cement (OPC) was replaced with CSA. These values were compared to both a control mortar (OPC) and a mortar in which OPC was partially replaced with 10% limestone filler. Ashes showed adequate pozzolanic reactivity because, at 90 curing days, the compressive strength of the mortars with 10% replacement of OPC with CSA was practically equal (98% of the strength) to the control mortar without pozzolan replacement. The auto-combustion of biomass is a process that can be easily available, and the results on pozzolanic reactivity of CSA are satisfactory. The auto-combustion could be used by low-income communities to reduce Portland cement clinker use and to recover waste. [ABSTRACT FROM AUTHOR]

Two different methods modified Pechini and green synthesis techniques, are used to synthesize Cobalt ferrite nanoparticles. The modified Pechini is a subset of the sol-gel route and results in nanoparticles from metal salts, ethylene glycol, and citric acid. The plant extracts of ginger root and cardamom seeds are utilized for the auto-combustion, green synthesis process to obtain the nanoparticles. The X-ray diffraction patterns confirm the spinel structure and the average particle size in the range of 14–20 nm for the nano ferrites. Energy dispersive analysis of X-ray shows the elemental analysis of cobalt, iron, and oxygen. The GC-MS analysis determines the structure of phenols present in the plant extracts, which act as fuels in the reaction. Scanning Electron Microscopy helps study nanoparticle morphology and particle size distribution. The FTIR analysis has been performed to identify the functional group in the as-prepared samples. Ultraviolet-Differential Reflectance Spectroscopy (UV-DRS) examines cobalt ferrite's optical properties. The photocatalytic properties of the CoFe2O4 spinel nano ferrites have been tested with Phenol red dye. [ABSTRACT FROM AUTHOR]

Cobalt zinc chromium ferrites, which have been doped with chromium Co0.4Zn0.6-xCrxFe2O4 (x = 0.05, 0.10, 0.15, 0.20) (CZC) nanoferrites, are employed by the auto-combustion route. The magnetic and dielectric characteristics of Co–Zn nanoferrites were improved by Cr3+. Analysis using XRD, FTIR, and FESEM reveals the cubic spinel phase for CZC nanoferrites. SEM reveals a lot of clustering. The ferrite samples have cluster form with a spherical shape in the range 54.64–73.38 nm, as seen by the FESEM results. TEM studies show agglomeration. The Cr3+ concentration determines the magnetic properties of specimens. Ms declines from 62.38 emu/g to 42.59 emu/g by increasing Cr3+. For all samples, a frequency-dependent evaluation of the dielectric properties, including dielectric constant, dielectric loss, and ac conductivity, is performed. On the basis of Koop's theory, the Maxwell-Wagner polarization procedure, and the movement of electrons, the fluctuation of dielectric features at frequencies between 50 Hz and 108 Hz has been mentioned. The dielectric constant and dielectric loss tangent decreased with increasing frequency. The conduction of ferrite samples is influenced by the grain boundaries. Both recording media and high-frequency devices can benefit from using these nanoferrites. [ABSTRACT FROM AUTHOR]

This article introduces a ternary nanocomposite‐based flexible thin film ammonia sensor developed on transparent polyethylene terephthalate (PET) substrate in the well‐known in situ chemical oxidative polymerization technique. The nanocomposite consists of three different materials: polyaniline (PANI), reduced graphene oxide (rGO), and zinc ferrite (ZF). Keeping the PANI amount constant, seven PANI/rGO/ZF (PRZ) samples are produced by performing stoichiometric variation between rGO and ZF. Later on, various structural, morphological, and spectroscopic analysis of all the composite materials is accomplished with field emission scanning electron microscopy (FESEM), high‐resolution transmission electron microscopy (HRTEM), X‐ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), and ultraviolet–visible spectroscopy (UV–Vis). The sensing performance of the as‐produced sensors toward ammonia (NH3) is examined in the concentration range from 250 ppb to 100 ppm. The study reveals the excellent sensing ability of the PRZ3 sensor (rGO = 30%, ZF = 20%) achieving minimum and maximum responsivity values of ~51% and ~1052%, respectively, at the lowest (250 ppb) and highest (100 ppm) concentration of ammonia. The sensor also exhibits admirable repeatability, good dynamic responsivity, rapid response (tres ~2.9–5 s), moderately faster recovery (trec ~37.9–69.7 s), superb linearity against ppm variation (R2 ~ 0.989), low detection limit (~123 ppb), and exceptional selectivity toward ammonia. The substrate temperature variation divulges that room temperature (30°C) is the ideal temperature for getting outstanding responsivity of the sensor. The study is further accompanied by humidity variation in the incoming air and bending flexibility test of the substrate. A compulsory and legitimate model regarding the sensing mechanism is presented at the end. [ABSTRACT FROM AUTHOR]

Pure Lanthanum Ferrite (LaFeO3) nanoparticles and Lanthanum Magnesium Ferrite (LaMgxFe1-xO3) nanocomposites have been prepared by the sol-gel auto-combustion method. The structural and morphological properties were investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and energy dispersive X-ray (EDAX) spectroscopy. Powder XRD studies revealed that the samples are pure orthorhombic perovskite crystals with a size of around 20-50 nm. The FT-IR spectra of pure and composites was confirmed the formation perovskite structure. It has been discovered that composites material functions as an electrode in supercapacitors after its electrical characteristics have been examined by galvanostatic charging and discharging (GCD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) with a 2 M KOH electrolyte. [ABSTRACT FROM AUTHOR]

Herein we report the effect of the Cr3+ content on the distinctive features of the first-ever auto-combustion-synthesis-produced Cr3+ doped ZnO nanoparticles utilizing leucine as the fuel. To assess the impact of fuel and Cr3+ content on the structural, optical, and luminescence characteristics, as-synthesized powders were systematically examined using powder XRD, UV–Visible, and Photoluminescence spectroscopy. Structural studies show that the exothermicity of the redox mixture containing oxidizer and fuel combination leads to the development of polycrystalline, single-phase, and nanosized particles. XRD analysis shows that, reduced crystallite size with Cr3+ content. In contrast, other characteristics like lattice parameters, unit cell volume, strain, and dislocation density, were shown to increase linearly with Cr3+ concentration up to 7 mol%. Additionally, it is seen that the predicted Urbach energy values rise as Cr3+ is added to the ZnO host matrix, indicating that the substitution of Cr3+ for Zn in the host ZnO lattice has increased structural disorder. In contrast to the other samples, the 5 mol% Cr3+ doped ZnO sample exhibits the emission near the white region according to the PL emission measurements. Furthermore, the photocatalytic activity of the as-prepared Cr3+ doped ZnO NPs was examined. It was found that the as-prepared samples exhibit outstanding photocatalytic activity in the visible wavelength region against Malachite Green (MG) dye. Among all, 9 mol% Cr3+ doped ZnO has shown the maximum 95.4% degradation against MG dye. All the investigated results conclude that the produced Cr3+ doped ZnO nanoparticles could be exploited in a variety of upcoming optoelectronic and photocatalytic applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fabrication of TmVO 4 nanocomposites by sonochemical approach. • Different solvents and content of TmVO 4 affect the purity, morphology, and size of products. • Investigation effect of tetra ethylene pentaamine as both capping and alkaline agent on size. • Utilization of TmVO 4 as a nanophotocatalyst for water treatment. • High ability of TmVO 4 for degradation of methyl violet dye (83%) in the visible area. The development of photocatalysts with adequate functions, particularly in the visible range, is one of the most significant issues facing scientists since they are essential compounds for the protection of the environment. A primary objective of this work was to simplify the preparation of thulium vanadate (TmVO 4) nanostructures in order to improve their photocatalytic efficiency. By using a facile auto-combustion route, this study presents a new method for fabricating TmVO 4 nanostructures. In order to achieve the desired size and homogeneity of the products, multiple factors were considered. As part of these parameters, several saccharides, such as glucose, fructose, lactose, maltose, and cellulose are analyzed for the first time, as well as the calcination temperature and the molar ratio. Various dye types and dye concentrations were studied to enhance catalyst performance. According to the catalyst activity, TmVO 4 was able to degrade 83.5% of the methyl violet (MV) after 90 min. TmVO 4 was found to be stable in the recycle test, with an efficiency reduction of 14.6% after five cycles. [ABSTRACT FROM AUTHOR]

We herein report the synthesis of monoclinic calcium aluminate (CaAl2O4) nanoparticles via a facile auto-combustion method followed by calcination. We performed the auto-combustion method using aluminium nitrate and calcium nitrate as oxidants and different fuels as reductants such as urea, glycine, and a mixture of urea and glycine, with various fuel-to-oxidant equivalence ratios (Φ c). Then, the combusted samples were calcined at different temperatures; 600 and 800 °C. The products were characterized by means of X-ray diffraction, Fourier transform infrared spectroscopy, thermo-gravimetric analysis, field-emission scanning electron microscope, and high-resolution transmission electron microscope. CaAl2O4 nanoparticles with an average crystallite size of 40.4, 38.8, and 33.7 nm were obtained after calcination at 800 °C using the aforementioned fuels, respectively. TEM images revealed that CaAl2O4 nanoparticles tend to form partially sintered aggregates owing to the high thermal treatment temperature, so they have non-uniform shapes. The produced CaAl2O4 nanoparticles exhibited good absorptivity toward Ni(II) and As(III) ions form aqueous media. The maximum sorption capacities (qm) of CaAl2O4 for the removal of Ni(II) and As(III) were found to be 58.73 and 43.9 mg.g−1, at pH 7 and 5, respectively. The equilibrium isotherms and adsorption kinetics studies revealed that the adsorption data fitted well Freundlich isotherm and pseudo-second-order models, respectively. Besides, the adsorption of Ni(II) and As(III) ions on CaAl2O4 nanoparticles is physisorption. Overall, the obtained results indicated that calcium aluminate nano-adsorbent is a good candidate for the removal of Ni(II) and As(III) ions from wastewater, due to its high efficiency, stability, and re-usability. [ABSTRACT FROM AUTHOR]

[Display omitted] • The initial endeavors in employing Cr-doped CeO 2 , synthesized using the modified auto-combustion technique, for electrochemical applications. • Studied the effect of various percentages of Cr doping on CeO 2 matrix and its influence on structural, morphological, vibrational and optical properties of CeO 2. • The specific capacitance of pristine CeO 2 attained 30.42F/g and it further achieves to 73.56F/g for Ce 0.925 Cr 0.025 O 2 at 0.5 A/g. • C e 1 - x C r x O 2 x = 0 , 0.1 samples show no magnetic long-range ordering ensuring zero hysteresis loss. • C e 1 - x C r x O 2 x = 0 , 0.025 , 0.05 can be used as functional, and low-cost supercapacitors for energy storage applications and also in data storage applications. The emergence of cerium oxide (CeO 2) has garnered significant interest as an energy storage gadget owing to its inspiring electrochemical, electrical and mechanical properties. Current work, we have synthesized C e 1 - x C r x O 2 x = 0 , 0.025 , 0.05 , 0.1 via simple auto-combustion method. The structure–property relations were characterized by several physicochemical characterizations such as XRD, FESEM, EDAX, vibrational spectroscopy, XPS, BET and UV–visible spectroscopy. The suds-like CeO 2 morphology and oxygen defects were highly suitable for the electrolytic ion intercalation to the electrode. By employing the Trassati model, Power law establishment and Dunn's model, the innate charge storage mechanisms in the synthesized materials were revealed. The specific capacitance of pristine CeO 2 attained 30.42F/g and it enhances to 73.56F/g for Ce 0.925 Cr 0.025 O 2 at 0.5 A/g. Further Ce 0.925 Cr 0.025 O 2 possesses a capacitance retention of 108.85 % even after 1000 GCD cycles at a current density of 4 A/g. The electrochemical results suggest C e 1 - x C r x O 2 x = 0.025 as a good material for supercapacitor applications. The magnetic measurements on the doped and undoped samples show no long-range ordering indicating zero hysteresis loss. Further, magnetic studies suggests the suitability of C e 1 - x C r x O 2 x = 0.1 for supercapacitance applications. [ABSTRACT FROM AUTHOR]

Zinc substituted magnesium ferrite with the compositional formula Mg1-xZnxFe2O4 (where x = 0.05, 0.10, 0.15, 0.20, 0.25) was synthesized using auto-combustion method. The ash obtained was calcined in microwave furnace at 550 °C for 30 min. The calcined powder was further annealed at 600 °C in the furnace. The structural, dielectric and magnetic properties were studied using XRD, LCR meter and vibrating sample magnetometer (VSM) for all the samples. XRD pattern confirmed the formation of the spinel cubic phase of magnesium ferrite. Lattice constants and density were determined from the Rietveld analysis of the XRD pattern. The crystallite size of all the samples was calculated. Presence of Fe-O bond in all the samples was confirmed by FTIR spectra. Dielectric properties such as dielectric constant and dielectric loss of all the samples were studied as a function of frequency. Both the quantities show dispersion with frequency. Dielectric constant and ac conductivity were found to be minimum when the concentration of Zn2+ is x = 0.15 while dielectric loss is maximum at this concentration. The VSM measurement showed that the saturation magnetization increased with the Zn2+ concentration up to x = 0.20. Electric polarizations of the samples were studied using P-E hysteresis loop. It was found that electric polarization decreased with the increasing concentration of Zn2+ up to x = 0.20. [ABSTRACT FROM AUTHOR]

In this manuscript, we report a successful synthesis and characterization of pure ZnO (ZO), Mn/Ni (ZMNO), and Mn/Co (ZMCO) co-doped ZnO nanoparticles which were prepared using low-cost and simple sol–gel auto-combustion method. These nanoparticles were analyzed by X-ray diffraction (XRD) and Fourier-transform infra-red (FTIR) spectroscopy for structural properties, scanning electron microscopy (SEM) along with energy-dispersive X-ray (EDX) spectroscopy for morphological analysis, and UV–Vis and photoluminescence spectroscopy for optical investigations. XRD and FTIR measurements substantiated that each sample is crystallized in the single-phase polycrystalline wurtzite hexagonal geometry of ZnO nanoparticles. The average crystallite size inferred from XRD spectra is found to be in the decreasing order of ~ 39 nm (ZO), ~ 38 nm (ZMNO), and ~ 37 nm (ZMCO), along with a significant reduction in the optical bandgap from 3.26 to 3.04 to 2.86 eV. The SEM images show that the nanostructures in the prepared samples are arranged in an agglomerated spherical patterns, while the EDX spectra signify the presence of Zn, Mn, Ni, Co, and O elements in the synthesized samples with their substantial percentage. The dielectric constant of all samples decline with frequency hence exhibits typical dielectric dispersion. AC conductivity of the samples increased with increasing frequency but decreased while doping. [ABSTRACT FROM AUTHOR]

Al–Cr substituted CoFe2O4 nano spinels (CoAlxCrxFe2−2xO4 where x = 0.1 to 0.6) were successfully prepared for the first time via sucrose sol–gel auto-combustion technique. The structural parameters as well as magnetic and electrical properties of the prepared ferrites have been investigated. X-ray diffraction (XRD) confirmed single-phase formation and showed a decrease in the calculated values of lattice parameters by substitution attributed to the difference in the ionic radii. Based on the obtained structural parameters, an appropriate cation distribution was proposed and discussed. In this distribution, most of Al3+ and Cr3+ ions preferred octahedral sites occupation however, small amount of Al3+ seek the tetrahedral sites. Accordingly, the magnetic characterization via vibrating sample magnetometer (VSM) measurements revealed a decrease in the saturation magnetization (Ms) by successive substitution from 57.9 to 4.7 emu/g, indicating the incorporation of non-magnetic Al3+ and anti-ferromagnetic Cr3+ ions in the octahedral sites instead of Fe3+ ions. The much lower magnetization values obtained than that prepared by other methods could be attributed to the present lower sizes. The coercivity measurements indicated soft ferrimagnetic properties favoring their uses as high frequency transformers. Ac-conductivity as well as dielectric properties, as a function of frequency and temperature, indicated semiconducting behavior with decreasing trend by Al–Cr substitution due to decreasing in the Fe3+-Fe2+ hopping probability in octahedral sites. The obtained results suggest the using of the present materials in electronic inductors, electromagnets and transformers and microwave devices.

[Display omitted] • Preparation of double perovskite La 2 CrMnO 6 nanoparticles by auto-combustion route. • Preparation of La 2 CrMnO 6 /g-C 3 N 4 nanocomposites by ultrasonic-assisted co-precipitation method. • Higher photodegradation yield due to synergistic effect between La 2 CrMnO 6 and g-C 3 N 4. • La 2 CrMnO 6 /g-C 3 N 4 (80:20) nanocomposites showed 80.98 % removal of methyl orange (MO). • Photocatalytic mechanism in nanocomposite system for MO degradation was proposed. Constructing semiconductor materials based on layered graphitic carbon nitride (g-C 3 N 4) and metal oxides can help in extending the lifetime of charge carriers and aid in resolving the low number of active sites on their surface for light-driven processes. Herein, we initially designed La 2 CrMnO 6 nanostructures through trimesic acid-assisted auto-combustion route and subsequently, La 2 CrMnO 6 /g-C 3 N 4 nanocomposites were prepared by ultrasonic-assisted co-precipitation method with improved UV-catalytic performance. The shape, size distribution and various properties of nano-sized products were measured via diverse description systems of microscopic and spectroscopic. The photocatalytic performances of the La 2 CrMnO 6 nanoparticles and La 2 CrMnO 6 /g-C 3 N 4 nanocomposites were compared by degradation of artificial dyes under the UV-light region. Besides, the impacts of dye type, diverse weight percentages of g-C 3 N 4 :La 2 CrMnO 6 in composite, scavenger kind and dye solution concentration were studied on modifying ability of nano-catalyst utility. The outcomes manifested La 2 CrMnO 6 /g-C 3 N 4 (80:20) nanocomposites have the greatest efficiency, where the highest MO decomposition of 80.98 % was achieved at 10 ppm within 90 min of irradiation. Moreover, the feasible mechanism of MO elimination by UV catalytic purpose was considered. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mn x Fe 2-x Mg 0.5 Ni 0.5 O 4 spinel ferrites were prepared utilizing a flash auto-combustion technique. • XRD confirmed formation of cubic phase spinel ferrite phase with space group Fd-3 m. • FTIR spectra validate the positions of the cations and their vibrational modes. • Optical band gaps Eg of investigated samples were found to decrease from 1.79 eV to1.24 eV. • The magnetic properties demonstrated soft ferrite nature with small hysteresis curve. Mn x Fe 2-x Mg 0.5 Ni 0.5 O 4 spinel ferrite nanoparticles (0.0 ≤ x ≤ 1) were prepared utilizing a flash auto-combustion technique. The as-prepared ferrite nanoparticles have been investigated and characterized using X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and Fourier transform infrared analysis (FTIR). The dielectric, optical and magnetic characteristics of the synthesized spinel ferrite samples were investigated using broadband dielectric spectroscopy (BDS), diffuse reflectance spectroscopy (DRS) and vibration sample magnetometers (VSM). The cubic phase spinel ferrite with space group Fd-3m was identified through XRD. X-ray diffraction indicates that the lattice constant increases and the crystallite size declines with increasing Mn concentration. The positions of the cations and their vibrational modes in the crystal structure with oxygen ions are demonstrated through the FTIR spectra. The morphology was examined using HRTEM showed polycrystalline cubic spinel structure with faceted planes. The optical band gap Eg was determined using Kubelka–Munk model where, it decreased from 1.79 eV to1.24 eV as Mn content increases. The replacement of manganese significantly affects the dielectric characteristics of the synthesized spinel ferrites. The real (ε′), imaginary (ε″) parts of dielectric constant and ac conductivity exhibit an increase in their values as manganese substitution (x) increases from 0 to 0.25 mol %, and thereafter decreases. The presence of a relaxation phenomenon in all prepared samples except the undoped sample (Ni 0.5 Mg 0.5 Fe 2 O 4) is shown by the imaginary modulus's (M′′) dependence on frequency. The magnetic properties exhibited soft ferrite nature with small hysteresis curve for all spinel ferrites samples. The magnetic properties of Mn x Fe 2-x Mg 0.5 Ni 0.5 O 4 nanoparticles were measured and analysed, including saturation magnetization (Ms), remanence (Mr), coercivity (Hc), and squareness ratio. (Ms), and (Mr), exhibit an increase in their values as manganese substitution (x) increases from 0 to 0.25 mol %, and thereafter decreases while squareness ratio decreased. The magnetic parameters greatly affected by Mn substitution ratio. [ABSTRACT FROM AUTHOR]

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The present paper reports the structural, dielectric and ac electrical properties of nanoparticles of mixed polycrystalline spinel ferrite ternary compound Mn0.6Co0.2Ni0.2Fe2O4 synthesized by using the citrate-gel auto-combustion technique. The standard characterization techniques such as EDAX, XRD and FTIR were primarily employed to confirm the elemental stoichiometry, crystallized single-phase, IR-functional groups. These measurements ascertained the formation of monophasic and pure ferrite compound. The powder X-ray diffraction analysis was done to determine the lattice constant(0.8420 nm), crystallite size(21 nm), X-ray density (5.16 g/cm3), distribution of cations among the tetrahedral and octahedral sites of spinel lattice(with iron-Fe3+ distribution ratio among A and B sites is 0.25), bond angles and bond lengths. The theoretical lattice constant is found to be 0.8422 nm. The nature and position of the IR-bands were observed through FTIR spectroscopy. The high-frequency band v1 (A-site vibrations) lies at 563.07 cm-1 while the low-frequency band v2 (B-site vibrations) lies at 462.59 cm-1. The force constants for the tetrahedral site (kt) and octahedral site (ko) were deduced 1.33 x 10² N/m and 1.27 x 10² N/m, respectively. Frequency dependence of dielectric constant and tangent loss has been explained by the Maxwell Wagner model and Koop's theory. The Jonscher's power low was used to describe the ac conductivity measurements. The Nyquist and cole-cole plots indicated presence of grain contribution in the conduction mechanism. [ABSTRACT FROM AUTHOR]

Mn0.8Zn0.2Fe2O4 ferrites were successfully prepared via a recycling process of spent Zn–C batteries (SZCBs) using sol–gel auto-combustion techniques and different fuels, including citric acid and sucrose chitosan, gelatin, and egg-white. The cost of this recycling technology, as well as the used fuels, have both economic and environmental advantages, facilitating many promising industrial applications. XRD confirmed single-phase formation with average crystallite sizes in the range from 15 to 55 nm. The appropriate cation distribution, elucidated using structural parameters, indicated the preferential occupancy of Zn+2 ions only by the A-sites while Mn+2 and Fe+3 ions preferentially occupy both A and B-sites. TEM images exhibited cubically agglomerated particles with wide size distribution. VSM indicated a wide range of magnetization values (51.0–19.8 emu/g) depending on the preparation route, suggesting the impact of the fuel used. The prepared ferrite using citric acid showed the highest value, while that prepared using egg-white indicated the lowest one. The obtained coercivities indicated soft magnetic materials with a decreasing behavior by increasing sizes. The ac-conductivity indicated semiconducting characteristics with a noticeable improvement in the conductivity than that of the bulk ferrite. The temperature dependence of the ac-conductivity showed a transition from ferro- to paramagnetic by increasing temperature. The estimated Curie temperatures (TC) indicated an improvement in the magnetic characteristics. In addition, the frequency dependence of ac-conductivity indicated a change in the conduction mechanism from the electron hopping to polaron type by increasing temperature. The very high dielectric values obtained in the order of 105 at low frequency warrant their application at low frequencies. Highlights: Mn0.8Zn0.2Fe2O4 ferrites were prepared from spent Zn-C batteries with different fuels. The entire ferrites were prepared using environment-friendly auto-combustion routes. Ferrites were characterized using XRD, TEM, and VSM. The different obtained properties were investigated and discussed. [ABSTRACT FROM AUTHOR]

The importance of water is so high that new methods and materials are constantly being developed to increase freshwater quality. For this purpose, to investigate the unique properties of double perovskites in the photocatalytic process, novel Tb2CoMnO6 nanoparticles were synthesized using the sol-gel auto-combustion method. In this method, maltose, cellulose, and Date syrup were used as fuel. Two different ratios of maltose were tested to investigate the effect of fuel content on size and morphology. The synthesized particles in the presence of maltose in an equal ratio to the precursor were selected as the optimal sample by using different analyses such as X-ray diffraction (XRD) and scanning electron microscopy (SEM). Other properties of optimal nanoparticles were investigated using transmission electron microscopy (TEM), energy dispersive spectrometry (EDS), Fourier transform infrared (FTIR), vibrating sample magnetometer (VSM) and diffuse reflectance analysis (DRS) analysis. These nanoparticles were used to investigate the photocatalytic properties under UV light in the aqueous solution of Eriochrome black T, Rhodamine B, Thymol blue, and Acid red dyes. The results of the photocatalytic process showed 70% discoloration for the Eriochrome Black T. Three compounds, include Ethylenediaminetetraacetic acid, 1,4-Benzoquinone, and Benzoic acid, were used as scavengers to investigate the mechanism of the photocatalytic process. The results showed that the mechanism of the photocatalytic process proceeds through superoxide radicals, which Benzoquinone scavenges.

In the present work, undoped and nickel doped zinc ferrite (ZnFe2−xNixO4) nano-composites were synthesized using a facile auto-combustion method using glycine as fuel. Effects of Ni dopant concentration and annealing process on structural and morphological properties were investigated by X-ray Diffraction (XRD), Raman spectroscopy, Fourier Transform InfraRed (FTIR) spectroscopy, and Scanning Electron Microscopy/Energy-dispersive X-ray spectroscopy (SEM/EDS). The formation of cubic spinel ferrites is confirmed by XRD analysis while asserting particles with a size range of 55–58 nm. Analysis of Raman spectra showed a transition of normal to inverse spinel-type with the increase in Ni content. Photocatalytic studies of as-synthesized nanoparticles using methylene blue (MB) demonstrated a strong correlation between photocatalytic efficiency and Ni doping. Ni-doped zinc-ferrites exhibited 98% photocatalytic efficiency at an optimum Ni doping concentration of 30%. As-synthesized ferrites have the potential to be used as an efficient, reusable, and magnetically removable photocatalyst system for removing organic pollutants. [ABSTRACT FROM AUTHOR]

In this paper, BaLa‌xGdxFe12-2xO19 (x=0.2, 0.4, 0.6 and 0.8) were synthesized via sol-gel auto-combustion method. Fourier transform infrared spectroscopy (FTIR) of samples was represented that the bands at 400 and 500 cm-1 were related to the formation of hexaferrite phase. The (x-ray diffraction) XRD patterns were matched exactly with the structure of barium hexaferrite. (Field emission scanning electron microscopy) FESEM were represented the hexagonal shapes of all products. Magnetic analysis of barium hexaferrite were investigated by (vibrating sample magnetometer) VSM. The saturation magnetization of all samples decreased by increasing dopant’s substitution due to the different occupation sites of dopants instead of Fe3+ (64 to 36.56 emu/g) in the hexaferrite structure. The coercivity increased because of its reverse relation with saturation magnetization (5010 to 5500 Oe). Microwave absorption properties of samples was investigated by (vector network analyzer) VNA. The maximum value of reflection loss was -7.8 db at 10.4 GHz frequency in 3mm thickness for x=0.4 sample.

Nanoscale SrAl2O4: Eu2+, Dy3+ with controllable size and morphology was synthesized by sol-gel auto-combustion method. The surface morphology and structural characterization were carried out with TEM and XRD. Optical properties were analyzed by comparing excitation spectra, emission spectra and afterglow decay of the nanoscale phosphor with that of the bulk phosphor. The results showed that citric acid acted as a soft template in the reaction system. The morphology and size changed clearly with pH value and sintering temperature. The crystallinity was affected by the quantity of citric acid. Both the nanoscale phosphors with different particle size and the bulk one have the strongest emission at 525 nm. But their strongest peaks in excitation spectra are very different from each other. The phosphorescence of nanoscale phosphor decays more rapidly than that of the bulk phosphor. [ABSTRACT FROM AUTHOR]

Nanoscale SrAl2O4: Eu2+, Dy3+ with controllable size and morphology was synthesized by sol-gel auto-combustion method. The surface morphology and structural characterization were carried out with TEM and XRD. Optical properties were analyzed by comparing excitation spectra, emission spectra and afterglow decay of the nanoscale phosphor with that of the bulk phosphor. The results showed that citric acid acted as a soft template in the reaction system. The morphology and size changed clearly with pH value and sintering temperature. The crystallinity was affected by the quantity of citric acid. Both the nanoscale phosphors with different particle size and the bulk one have the strongest emission at 525 nm. But their strongest peaks in excitation spectra are very different from each other. The phosphorescence of nanoscale phosphor decays more rapidly than that of the bulk phosphor. [ABSTRACT FROM AUTHOR]

In this article, MgO/Ca 2 Mn 3 O 8 nanocatalyst was used for the first time in the transesterification process for the production of green fuel from sunflower oil. Besides, the synthesis of layered nanostructured Ca 2 Mn 3 O 8 was done for first applied by combustion route as well. The effects of two heating sources including muffle furnace and microwave irradiation, and also various fuels including urea, glycine, and ethylene glycol were investigated on the characteristics of calcium-manganese oxide (Ca 2 Mn 3 O 8) as the support of the nanocatalysts loaded by MgO as active phase. The synthesized samples were characterized by different analyzes such as AFM, HRTEM, FESEM, FTIR, EDX, XRD, and BET-BJH. The nanocatalyst produced by the microwave irradiation combustion method and urea fuel scored the best performance. This nanocatalyst had the highest specific surface area (46.4 m2/g), and better pore size distribution, too. The roughness of this sample was reported at 5.1 nm in the range of 2 μm. It was found that the optimum sample has converted 96.7% of the oil extracted from sunflower seed to fatty acid esters that are gained by transesterification of fats with methanol. This sample exhibited better reusability in the same operating conditions in proportion to the sample synthesized with muffle furnace in twelve runs, which justified the positive influence of microwave irradiation on the catalytic properties. [ABSTRACT FROM AUTHOR]

Nanocrystalline LaCoO3 powders were fabricated via the sol–gel microwave-induced combustion approach using metal nitrates as oxidant and citric acid as fuel. Calcination of the precursor was performed in the temperature range 400–800 °C. The precursor of the LaCoO3 powder as well as the calcination products were investigated using thermal analysis (TGA and DTA), FTIR, XRD and N2 adsorption techniques. In a dynamic air atmosphere, calcination was implemented in the temperature range 400–800 °C. XRD patterns show the fabrication of the perovskite rhombohedral phase of LaCoO3. The average nanoparticle size calculated from the XRD patterns was in the range 8–21 nm. Surface area measurements calculated from the N2 adsorption isotherms show low surface area values. The porosity of these materials was identified to be microporous in nature. SEM and TEM tests endorsed the findings. Analysis of TGA and DTA showed a sharp exothermic peak of about 358 °C and a steady weight loss of up to about 600 °C. The vapor-phase dehydration/dehydrogenation of isopropanol, in the temperature range 350–425 °C, was adopted to assess the catalytic performance. The activity of the LaMnO3 catalysts is mainly directed towards the dehydrogenation reaction forming acetone as a main product. The maximum yield was found for the sample calcined at 600 °C. A strong correlation was identified between the selectivity of dehydrogenation and the redox couple species evaluated. A potential reaction mechanism was suggested that would be compatible with the data obtained. [ABSTRACT FROM AUTHOR]

Iron oxide (Fe2O3) nanoparticles were prepared by combination of sol-gel autocombustion and ultrasonic irradiation. The XRD pattern reveals that the crystallite size of sample is 36.7 nm and the phase identification shows hematite, syn has been crystalized. The morphology of the sample investigated by FESEM showed that particle size of the sample was about 76 nm. The optical property of Fe2O3 investigated by DRS showed that there may exist three energy band gaps in iron oxide nanoparticles . FT-IR technique was used to determine the functional group of product. In agreement to XRD results, the result of FT-IR revealed no organic residue in product. Photo catalyst nanoparticles were immobilized on the surface of glass slide using Doctor Blade method. Photocatalytic degradation of reactive red 4 (RR4) was investigated under UV light using iron oxide nanoparticles as catalyst. The kinetic of RR4 degradation under UV light irradiation in the presence of Fe2O3 as photocatalyst, and rate constant was determined. Experiments exhibited that Fe2O3 nanoparticles decomposed 52% of azo dye RR4 in solution duration 135 min. The photo catalytic reaction kinetic of RR4 degradation in the presence of Fe2O3 nanoparticles followed Langmuir-Hinshelwood model with the rate constant of about 0.005 min-1.

A relaxor electroceramic 0. 3 5 Pb ( Mg 1 / 3 Nb 2 / 3) O 3 – 0. 3 5 ( Pb 1 − 1. 5 x La x) TiO 3 –0.30- ( Ba 1 − 1. 5 x La x) TiO 3 (PMN–PLT–BLT) with x = 0.25, 0.50 and 0.75 was synthesized using the two combination methods of auto-combination and hot-pressing. Characterization of the crystal phase, microstructure, optical and dielectric properties of PMN–PLT–BLT was made primarily by X-ray diffraction and TEM and SEM methods. The pure perovskite crystals (rhombohedral and tetragonal) prepared at 8 5 0 ∘ C for 2 h calcination were revealed by using X-ray diffraction. The average optical transmittance of these electroceramics in the range between 450 nm and 900 nm is higher than 60% while in the IR region reached 100%. The PMN–PLT–BLT with x = 0.75 displays the highest transparency around 70% near 1100 nm. The microstructures and dielectric measurements show that these three electroceramics have densities of about 98.8% and exhibit a normal relaxation characteristic. [ABSTRACT FROM AUTHOR]

LaFeO 3 was prepared via simple, economical and environmentally friendly auto-combustion methods using different fuels, including citrate, urea, sucrose, egg whites, gelatin and chitosan. The prepared ferrites were systematically characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, high resolution transmission electron microscopy (HRTEM), vibrating sample magnetometry (VSM) and electrical measurements to study the impact of the synthetic routes on the various properties. XRD showed the formation of a single orthorhombic phase, except for the samples prepared via egg white, gelatin and urea methods, which indicated a secondary La 2 O 2 CO 3 phase. The FT-IR and TEM studies confirmed the formation of the phase. Differential thermal analysis-thermogravimetry techniques (DTA-TG) were used to characterize the auto-combustion process up to ferrite formation. The obtained unsaturated magnetization for all of the samples suggested the presence of anti-ferromagnetic ordering in addition to weak ferromagnetic ordering. The egg white method showed higher magnetization (1.78 emu/g), while the urea and chitosan methods indicated lower magnetization (0.13 emu/g). The coercivity measurements confirmed the presence of ferromagnetic/anti-ferromagnetic interfaces with higher values than those reported in the literature. The AC-conductivity measurements indicated semiconducting characteristics and exhibited a change in the conduction mechanism from hopping to polaron conduction by increasing the temperature. LaFeO 3 prepared via the egg white method indicated an anti-ferromagnetic/paramagnetic transition at approximately 715 K. The dielectric measurements confirmed the AC-conductivity results and exhibited values higher than those reported in the literature. [ABSTRACT FROM AUTHOR]

Abstract It is extremely desirable but challenging to develop a facile synthesis to directly prepare permanent magnet foam with high coercivity (H c) and low mass density to meet the requirements of advanced magnets in modern industry. In this work, we developed a facile strategy to synthesize cobalt ferrite foam by solution combustion method and subsequently annealing treatment. The structure and magnetic properties of the foams can be influenced by the ratios of glycine to nitrate (G/N), Co content and annealing treatment temperatures. The increase in the mean grain sizes within the single domain range gives rise to an enhancement in coercivities. The highest H c of ∼3 kOe with an ultra-low mass density of ∼45 mg/cm3 can be successfully obtained by controlling the preparation process. The work opens up a new way to prepare ultra-light Fe-based oxides for magnetic and catalytic applications. Highlights • Foam-like porous Co x Fe 3- x O 4 was prepared by facile auto-combustion method. • The effects of glycine to nitrate ratios and Co content were studied. • Ultra low mass density ∼45 mg/cm3 and large coercivity ∼3 kOe were obtained. [ABSTRACT FROM AUTHOR]

The concept of spontaneous combustion has huge appeal as an historical fiction but it has no scientific background. However, in some deaths involving fire, a body can burn away virtually completely with minimal thermal destruction to the neighboring environment. We report an extraordinary case of the self-immolation of an elderly woman who set herself on fire with suicidal intentions. The unusual appearance and location of the body closely resembled the phenomenon of so-called spontaneous human combustion because the upper parts of the body were almost totally destroyed by fire, while the legs and surrounding structures remained almost untouched by flames. The results of all investigations proved that the woman set fire to her body using a box of matches and accelerants (concentrated ethanol and a solid firelighter). Near-total combustion of her body subsequently occurred during the postmortem period. The development of alleged spontaneous human combustion requires the following: ignition (external heat source), fuel (molten human fat), a wick (e.g. charred and porous clothing, bedding, or ground), time, and an optimal microclimate for gradual burning. [ABSTRACT FROM AUTHOR]

• Highly reactive ashes from bamboo leaves (BLA) were prepared by autocombustion. • BLA presented a high silica content (74.23%) most of it was amorphous silica. • Pozzolanic reactivity of BLA was characterized by different procedures. • Replacement of OPC by BLA (5–30%) was achieved, yielding good mechanical performance. • BLA is a suitable and sustainable alternative for partial OPC replacement. In the context of world concern with the environment, this study aims to characterize an auto-combustion produced bamboo leaf ash (BLA) by its pozzolanic behaviour, reactivity and its influence in the total porosity, pore size distribution, tortuosity and mechanical behaviour of cementitious matrices. The chemical and physical characterization of the BLA was carried using X-ray fluorescence, determination of amorphous silica content, X-ray diffraction, Fourier Transform Infrared Spectrophotometry (FTIR), laser granulometry and field emission scanning electron microscopy (FESEM). The assessed BLA is a siliceous material (74.23%) with an amorphous nature due to the amorphous silica content, which represents 92.33% of the total silica. The BLA was classified as highly reactive by assessing its pH and conductivity in a saturated calcium hydroxide (CH) medium for different proportions and temperatures. Frattini analysis, the study of CH:BLA pastes (Thermogravimetric analysis and FTIR) and Portland cement (OPC)/pozzolan pastes (Thermogravimetric analysis and FESEM) are in agreement with this classification. The replacement of OPC by BLA improved the mechanical behaviour of the cementitious matrices, as well their durability. All the mortars containing BLA presented very similar compressive strength to a control mortar (100% OPC) after only 3 days of curing and at the following tested curing ages: 7, 28 and 90 days. In the mercury intrusion porosimetry analysis, the pastes with 20 and 30% BLA content presented higher tortuosity or fewer connected pores than the control paste. Thus, the auto-combustion method proved to be successful and BLA is a suitable alternative for sustainable high-performance matrices. [ABSTRACT FROM AUTHOR]

• Nd-Fe-B wastes have been recycled by auto-combustion method assisted with microwave. • After recycling Nd-Fe-B/α-Fe composite magnetic powders are directly synthesized. • The coercivity of as-synthesized Nd 15 Fe 77 B 8 powders is higher than 400 kA/m. • The magnetic properties of products are comparable with those using pure reagents. The present work provides a facile and energy-saving approach to recycle Nd-Fe-B wastes. Employing the severely oxidized and contaminated sintered Nd-Fe-B scraps as the raw materials, sub-micro sized Nd-Fe-B/α-Fe composite magnetic powders were successfully synthesized by microwave assisted auto-combustion method followed by a reduction diffusion process. In details, the waste magnets were dissolved in HNO 3 solution and both the rare earth oxides and iron oxide were obtained by auto-combustion approach with the help of microwave heating. These oxides were then reduced to achieve Nd-Fe-B alloys with the reducing agent CaH 2. To modify the composition of the final product, Nd(NO 3) 3 ·6H 2 O and H 3 BO 3 were added during dissolving and consequently three compositions of the final products were obtained. TEM results demonstrate that the sizes of α-Fe and Nd 2 Fe 14 B grains are below 10 nm and 20 nm, respectively. The magnetic properties of the composite powders obtained from the wastes in this study are comparable to those obtained by other methods using pure reagents. The room temperature coercivity of as-synthesized Nd 15 Fe 77 B 8 is higher than 400 kA/m. In addition, an appropriate mass ratio of CaH 2 to Nd-Fe-B oxides is required in order to obtain good magnetic properties. [ABSTRACT FROM AUTHOR]

Abstract Palm oil mill effluent (POME) is a serious and expensive environmental problem in Malaysia. In this paper, CaFe 2 O 4 is introduced as a novel photocatalyst for the degradation of POME under visible light irradiation. Two synthesis routes, auto-combustion and co-precipitation, and two calcination temperatures 550 °C and 700 °C were used to produce four CaFe 2 O 4 catalysts AC550, AC700, CP550 and CP700. CP550 exhibited the greatest photocatalytic degradation at 56% chemical-oxygen-demand (COD) removal after 8 h of irradiation which dropped to 49% after three consecutive cycles indicating reasonable conversion and high recyclability. BET analysis indicated CP550 had the highest S BET (27.28 m2/g) and pore volume (0.077 cm3/g) which dropped precipitously for CP700 upon increasing the calcination temperature to an S BET of 9.73 m2/g and pore volume of 0.025 cm3/g due to annealing which created a smoother surface area as evidenced by the SEM images. UV–Vis DRS indicated CP550 had the highest band-gap (1.52 eV) which is likely due to the presence of a highly crystalline pure CaFe 2 O 4 phase compared to the other products which existed as a mixture of Fe oxidation states evidenced by the XRD data. The PL spectra for all catalysts indicated significantly lower recombination rate for both CP550 and CP700. Introduction of IPA into the reaction mixture to eliminate hydroxyl radicals resulted in a diminishing of COD removal from 56% to 7% proving hydroxyl radicals to be the primary reactive species responsible for photodegradation of POME. Highlights • Visible light-active CaFe 2 O 4 was synthesized to treat POME. • Auto-combustion and co-precipitation were employed to produce CaFe 2 O 4. • Scavenging studies showed OH. as a responsible radical to degrade POME. • Recyclability studies showed a mere 7% reduction in POME degradation. [ABSTRACT FROM AUTHOR]

Highlights • Sol-gel auto-combustion method was exploited to prepare homogeneous nanocomposite. • Structural and microscopic analysis confirmed formation of two distinct phases. • Samples prepared by combustion method show single-step hysteresis loops. • Good exchange coupling between hard and soft phases confirmed by Henkel plots. • Increase in (BH) max was observed by overcoming exchange on dipolar interaction. Abstract Ferrite based hard-soft magnetic nanocomposites with the composition of (100 − x) SrFe 10 Al 2 O 19 /(x) Co 0.8 Ni 0.2 Fe 2 O 4 , where x = 10, 15, 20 and 30 wt%, were prepared by one-pot sol-gel auto-combustion method. The nanocomposites prepared by this method showed crystallographically two phase behavior, but magnetically a good single phase exchange spring-coupled behavior with high saturation as well as high coercivity. The nature of magnetic interactions in these nanocomposites and their magnetic properties were evaluated in detail using various characteristic methods including vibrating sample magnetometer measurements, Henkel plots measurements, magnetic force microscopy and magneto-optical Kerr effect microscopy. Microstructural evolution showed formation of soft phase below the critical size of exchange length in the vicinity of hard phase. The nanocomposite with 15 wt% of soft phase showed a 10.5% increase in the maximum energy product compared to pure hard phase and reaches as high as 29.5 kJ/m3 that is a high value of (BH) max for this type of materials. [ABSTRACT FROM AUTHOR]

The three-dimensional porous ceria (CeO 2) nanostructures and cobalt (Co) doped porous ceria with different cobalt contents (1 %, 2.5 %, 5 %, and 10 % wt%) were prepared by using the auto-combustion technique. Several characterization techniques, including ICP elemental analysis, XRD, DR UV-Vis, SEM, and TEM, were utilized to describe the fabricated products. The findings confirmed the incorporation of cobalt ions into the ceria framework. Furthermore, the light absorption property of cobalt-doped porous ceria samples was observed to be red-shifted, with the calculated bandgap decreasing from 3 to 2.1 eV for neat porous ceria and 10 % Co doped ceria, respectively. The photocatalytic efficiency of cobalt-doped porous CeO 2 was investigated in the decolourization of methyl green dye by utilizing visible light illumination. The photocatalytic data obtained revealed a remarkable increase in activity that is nearly three times greater than the un-doped ceria sample. Furthermore, the best performed cobalt-doped ceria sample was reusable until the fourth consecutive reaction without treatment. [ABSTRACT FROM AUTHOR]

• LSMO-AC and LSMO-PC crystallized in mixed phases with R-3c and Pbnm symmetries. • LSMO-AC and LSMO-PC samples are close to conventional universality class. • LSMO-PC, with porous surface, allows faster heat exchange. • LSMO-AC displays very high thermal stability of both ΔT M and ΔS M. In this work, La 0.8 Sr 0.2 MnO 3 (LSMO) nanopowders are synthesized using two different methods: Pechini (LSMO-PC) and auto-combustion (LSMO-AC). Nanoparticle sizes, structural, magnetic, and magnetocaloric properties were determined and compared. The X-ray diffraction confirms the coexistence of two phases; rhombohedral symmetry with space group R-3c and orthorhombic symmetry with space group Pbnm. The rhombohedral phase is dominant. The scanning electron microscope images show that LSMO-PC has larger nanoparticle sizes (∼495 nm) than LSMO-AC (∼195 nm). The samples exhibit ferromagnetic properties with distinct hysteresis loops and Curie temperatures of 340 K and 290 K for LSMO-PC and LSMO-AC, respectively. The variation of the magnetic entropy was measured indirectly using the Maxwell approach with increasing magnetic field. For LSMO-PC it reaches a maximum -ΔS M = 1.69 J/kg.K at 340 K and ΔH = 5 T. The associated adiabatic temperature change ΔT M is 1.04 K. While LSMO-PC demonstrates superior magnetic and magnetocaloric properties, LSMO-AC displays significant magnetocaloric thermal stability. The obtained values make LSMO-PC and LSMO-AC promising candidates for eco-friendly room-temperature magnetocaloric applications. [ABSTRACT FROM AUTHOR]

Pure phase spinel ferrite nanoparticles (Mn0.5Zn0.5Fe2O4) were one-step synthesized by the sol-gel auto-combustion method at low temperature. The structural characteristics, morphology and thermal decomposition were characterized by X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), TG-DSC analyzer, respectively. The results indicate that pure phase Mn0.5Zn0.5Fe2O4 ferrite nanoparticles of about 60nm in diameter can be directly synthesized after auto-combustion of the nitrate-citrate xerogel under the conditions of pH=7.0, R=1:1 and C(CA)=0.7 mol/L. The obtained nanoparticles show the diameter increases and the diffraction peak narrows but the strength increases after calcined at 400℃ which improves the crystal structure.

M-type barium hexaferrite (BaFe _12 O _19 ) particles are synthesized by using sol-gel auto-combustion reaction for microwave absorption study in X-band. Three different materials namely BaNd _0.02 Fe _11.98 O _19 (Nd2), BaNd _0.04 Fe _11.96 O _19 (Nd4) and BaNd _0.06 Fe _11.94 O _19 (Nd6) have been developed by varying doping of neodymium in barium hexaferrite. The synthesis of particles has been confirmed using SEM micrographs and XRD diffraction pattern. The hysteresis study is carried out for saturation magnetization using vibrating sample magnetometer (VSM). As the doping concentration of neodymium increases, the saturation magnetization of the material is decreased from 47.272 emu g ^−1 to 16.479 emu g ^−1 . The vector network analyzer (VNA) is used for complex permittivity and complex permeability measurements of the developed materials. Nd4 material shows highest values of permittivity and permeability losses among other developed materials. From the complex permittivity and complex permeability, the reflection loss results of the developed materials have been calculated. The maximum reflection loss of −33.17 dB was obtained for 2.2 mm pallet of BaNd _0.04 Fe _11.96 and −10 dB bandwidth reaches 2.94 GHz.

Undoped and Ba and Ag-doped SrTiO3-based nanopowders (NPs) were successfully grown by a modified auto-combustion method. An optimum ratio of citric acid and nitric acid was used as the polymerization agent and fuel. The X-ray diffraction (XRD) results revealed that the products were crystalline with cubic and tetragonal structures. The particle aggregation state, nanoparticles size distribution, morphology and electrical properties were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), atomic force microscopy (AFM) and ultraviolet–visible (UV–vis) were studied, respectively. Using the X-ray peak broadening and size–strain plot (SSP) method the crystallite sizes and lattice strain of the samples were investigated. The UV–vis absorption spectra revealed that the band gap of the STO-based has a strong absorption peak which lies in the UV region.

Biodiesel was produced in laboratory in two consecutive steps i.e. esterification followed by transesterification using a novel heterogeneous base catalyst and Madhuca indica (Mahua) oil as a feedstock. Barium lanthanum oxide, a novel catalyst was synthesized by four different methods i.e., co-precipitation (BLOC), solid state (BLOS) and the citrate route or auto-combustion method (BLOA1 and BLOA2). The catalyst was characterized and the catalytic activity was measured by quantifying the FAME content of the biodiesel. It has been observed that BLOA1, BLOA2, and BLOC resemble with each other as they have the same phase with an identical structural formula of Ba 2 La 2 O 5 . This observed structural formula constituted the mixture of the perovskite and metal oxides. The BLOS sample had the structural formula of Ba 10 La 2 O 13 which proved the extensive formation of individual metal oxides. Out of the samples, BLOA2 synthesized by citrate route was efficient in biodiesel production. The citrate route synthesis performed at pH 2.31 enriched the catalyst mixed metal oxide surface with free OH − groups, which ultimately avoided the formation of the carbonate species, produced biodiesel with 97.5% FAME conversion. Hence, Barium Lanthanum Mixed metal oxide prepared by citrate route in acidic medium is a potential catalyst for biodiesel production. The reaction mechanism followed first-order kinetics. The activation energy (E A ) was 34.44 kJ mol −1 and the frequency factor (A) was 7.94 min −1 . The physicochemical properties of the synthesized Mahua oil methyl ester (MOME) were measured according to ASTM D 6751 and were found to be within the permissible range. [ABSTRACT FROM AUTHOR]

The effect of Ni 2+ doping on the magnetic and magnetocaloric properties of La 0.7 Ca 0.3 MnO 3 manganites synthesized via the auto-combustion method is reported. The aim of studying Ni 2+ -substituted La 0.7 Ca 0.3 Mn 1 − x Ni x O 3 ( x = 0 , 0.02 , 0.07 , and 0.1) manganites was to explore the possibility of increasing the operating temperature range for the magnetocaloric effect through tuning of the magnetic transition temperature. X-ray diffraction analysis confirmed the phase purity of the synthesized samples. The substitution of Mn 3+ ions by Ni 2+ ions in the La 0.7 Ca 0.3 MnO 3 lattice was also corroborated through this technique. The dependence of the magnetization on the temperature reveals that all the compositions exhibit a well-defined ferromagnetic to paramagnetic transition near the Curie temperature. A systematic decrease in the values of the Curie temperature is clearly observed upon Ni 2+ doping. Probably the replacement of Mn 3+ by Ni 2+ ions in the La 0.7 Ca 0.3 MnO 3 lattice weakens the Mn 3+ –O–Mn 4+ double exchange interaction, which leads to a decrease in the transition temperature and the magnetic moment in the samples. By using Arrott plots, it was found that the phase transition from ferromagnetic to paramagnetic is second order. The maximum magnetic entropy changes observed for the x = 0 , 0.02 , 0.07 , and 0.1 composites was 0.85, 0.77, 0.63, and 0.59 J/kg K, respectively, under a magnetic field of 1.5 T. In general, it was verified that the magnetic entropy change achieved for La 0.7 Ca 0.3 Mn 1 − x Ni x O 3 manganites synthesized via the auto-combustion method is higher than those reported for other manganites with comparable Ni 2+ -doping levels synthesized via standard solid state reaction. The addition of Ni 2+ increases the value of the relative cooling power as compared to that of the parent compound. The highest value of this parameter (∼60 J/kg) is found for a Ni-doping level of 2% around 230 K in a field of 1.5 T. [ABSTRACT FROM AUTHOR]