Sol Gel Combustion Process Research Articles

Enhanced protonic and oxygen-ionic conductivity in Ga-doped Nd2Ce2O7 electrolytes for intermediate-temperature solid oxide fuel cell

Developing mixed oxygen-ion and proton conductors with high ionic conductivity is crucial for advancing intermediate temperature-solid oxide fuel cell (IT-SOFC). In this study, a novel Nd2-xGaxCe2O7 (NGCO, x = 0, 0.05, 0.075, 0.10 and 0.15) ceramic is synthesized by the citric acid-nitrate sol-gel combustion process. The influence of Ga doping on crystal structure, oxygen vacancy, morphology, proton transport characteristic and electrochemical performance of this materials is systematically investigated. It is found that the NGCO exhibits the fluorite-type structure and belongs to space group Fm3¯m. NGCO shows remarkable chemical stability, resisting harmful effects from CO2, water, and wet hydrogen exposure. Adding a small amount of Ga results in high-density ceramics with enlarged grain size and reduced grain boundary density. Nd1.925Ga0.075Ce2O7 (7.5NGCO) displays outstanding conductivities, exceeding Nd2Ce2O7 (NCO) by 271.4% and 248.6% in dry air and wet hydrogen conditions. Further, an anode-supported structure fuel cell with 7.5NGCO electrolyte is constructed and evaluated. The peak power density (PPD) at 700 °C reaches 702 mW/cm2, a 96% enhancement over the fuel cells with NCO electrolyte. These findings indicate that Ga-doped NCO electrolyte holds promise as a proton-conducting electrolyte suitable for IT-SOFC.

Exploring the diverse performance of nickel and cobalt spinel ferrite nanoparticles in hazardous pollutant removal and gas sensing performance.

A simple sol-gel combustion process was employed for the creation of MFe2O4 (M=Ni, Co) nanoparticles. The synthesized nanoparticles, acting as both photocatalysts and gas sensors, were analyzed using various analytical techniques. MFe2O4 (M=Ni, Co) material improved the degradation of methylene blue (MB) under UV-light irradiation, serving as an enhanced electron transport medium. UV-vis studies demonstrated that NiFe2O4 achieved a 60% degradation, while CoFe2O4 nanostructure exhibited a 76% degradation efficacy in the MB dye removal process. Furthermore, MFe2O4 (M=Ni, Co) demonstrated chemosensitive-type sensor capabilities at ambient temperature. The sensor response and recovery times for CoFe2O4 at a concentration of 100ppm were 15 and 20, respectively. Overall, the synthesis of MFe2O4 (M=Ni, Co) holds the potential to significantly improve the photocatalytic and gas sensing properties, particularly enhancing the performance of CoFe2O4. The observed enhancements make honey MFe2O4 (M=Ni, Co) a preferable choice for environmental remediation applications.

A Spectroscopic Correlative Analysis of Eu3+‐Substituted Zn1‐xSnO3 Nano Phosphors for Anticounterfeiting Applications

AbstractA series of orange–red phosphors Zn1‐xSnO3:xEu3+ synthesized using a sol–gel combustion process is used to study the modified local crystal structure by site‐selective substitution of Eu3+ ions. XRD with the Rietveld refinement analysis reveals an orthorhombic ZnSnO3 structure with a space group 61. SEM and TEM with EDAX analyses confirm the flower‐like morphology of Zn1‐xSnO3:xEu3+ nanorods. Photoluminescence (PL) spectroscopy gives substantial confirmation for the inclusion of Eu3+ ions into the ZnSnO3 host. Judd‐Ofelt analysis confirms the substitution of Eu3+ ion in an asymmetric environment in ZnSnO3, which is responsible for orange–red emission at 615 nm. UV–vis–DRS analysis shows that the addition of Eu3+ ions (1% to 17% in phases of 4%) results in the formation of confined energy states with an increased band gap from 2.78 to 3.29 eV. The ability of ZnSnO3 to host Eu3+ ions signifies that it can be used as an effective luminescent material. Cyclic voltammetry analysis reveals the enhanced charge separation in Zn1‐xSnO3:xEu3+(13%) nanophosphor. The optimized Zn1‐xSnO3:xEu3+(13%) nano phosphor mixed with silicone investigated for the generation of anti‐counterfeiting patterns indicates its potential to generate high‐resolution image patterns on various surfaces under monochromatic UV or visible‐LASER LED illumination.

The effect of the citric acid to metal nitrates molar ratio on the structural and magnetic properties of strontium hexaferrite nanoparticles synthesized by the sol-gel combustion method

Strontium hexaferrite is a hard ferrite with the chemical formula of SrFe12O19 and has a magnetoplumbite structure. Due to high anisotropy, high saturation magnetization, chemical stability, high corrosion resistance, and appropriate Curie temperature, it has been widely used as a permanent magnetic material. A novel sol-gel combustion process was used to synthesize ultrafine particles of strontium hexaferrite. The weight ratio of citric acid to the total weight of strontium and iron salts nitrate (CA/MN) is among the parameters affecting the purity of SrFe12O19 nanoparticles produced by the sol-gel method, which can improve the purity of the final product by controlling this parameter. M-type SrFe12O19 nanostructures with different citric acid to metal nitrates molar ratios (0.5, 1, 2, and 4) were prepared. The results showed that nitrate-citrate gels exhibit self-ignition behavior after combustion in the air at room temperature. The samples were then characterized by XRD, TGA/DTA, FTIR, FE-SEM, VSM. The results showed that the crystallite size of strontium hexaferrite is significantly affected by the molar ratio of citric acid to metal nitrates. As the molar ratio of citric acid to metal nitrates increases, the size of nanostructures decreases. By increasing the molar ratio of citric acid from 0.5 to 1, the saturation magnetization and magnetic remanence magnetization increase, but the coercive field decreases.

Unraveling the effect of Gd doping on the structure, optical, magnetic, dielectric and photocatalytic properties of ZrO2 nanostructures

Nanocrystalline Zr1-xGdxO2 (0≤x ≤ 0.20) samples were synthesized through the sol-gel combustion process and characterized by various characterization techniques.XRDanalysis confirms a highly crystalline tetragonal phase with P42/nmc space group. TEM micrographs exhibitreduction in particle size on Gd doping. Photoluminescence (PL) study shows improved light absorption ability of the Gd-doped ZrO2, signifying an excellent way to control the recombination rate of electron-hole pair. XPS analysis ensures the successful incorporation of Gd in the ZrO2 lattice. Room temperature magnetic measurements revealthe ferromagnetic nature of all the samples. The UV-visible spectroscopy shows increase in band gap from 3.82 eV to 4.45 eV. The dielectric constant varies significantly for the Gd-doped samples. All the prepared catalysts were tested for the photocatalytic activity of the methylene blue (MB) dye under visible light irradiation. After 120 minutes, 20% Gd-doped ZrO2displays∼91% degradation efficiency against the MB dye, which makes it a promising visible light-activated photocatalyst.

Fabrication of Hierarchical Porous Metal Oxides by the HPMC-Assisted Gel Combustion Strategy: Incorporation of Nanoceria into Cookie-like Mn2O3 with Enhanced Oxidation Activity and Excellent Water Resistance

Constructing nonprecious metal oxide catalysts with a hierarchical porous structure by a simple method for the deep catalytic oxidation of toxic volatile organic compounds at low temperatures is of great value and significance. In this work, a porous manganese trioxide catalyst (Mn2O3-H) was prepared by a hydroxypropyl methylcellulose-assisted combustion synthesis strategy for catalytic complete oxidation of gaseous toluene. Benefiting from the rich porous nanostructure, Mn2O3-H has much higher specific surface area and active site density, resulting in better low-temperature reducibility and oxygen activation ability than blank Mn2O3 formed by direct calcination. With this sol–gel combustion process, CeO2 nanoparticles could be successfully introduced to form cookie-like Ce–Mn composite oxide with a hierarchical porous nanostructure, which builds the strong interaction of CeO2–Mn2O3 to weaken Mn–O with more active defects. Among Ce-doped catalysts, 5%CeMn-H shows the best catalytic activity in toluene oxidation with 90% conversion temperature at 242 °C under a weight hour space velocity of 60,000 mL·g–1·h–1, which is about 30 and 133 °C lower than that of Mn2O3-H and Mn2O3-B, respectively. This advantage is also shown in other typical hydrocarbons such as propylene and propane. Moreover, the as-prepared Ce-doped catalyst exhibits excellent stability and water resistance ability. This simple robust sol–gel combustion method will provide valuable enlightenment for designing porous catalysts with high performance for related catalytic reactions.

Spectroscopic and Magnetic Performance of Cobalt (Co) Incorporated NiMn0.05Fe1.95O4 Nanoferrites: A Potent Antifungal Activity Against Aspergillus niger (MT675916)

We investigated the impact of cobalt (Co) incorporation on the structural, optical, and magnetic properties of ferrite Ni[Formula: see text]CoxMn[Formula: see text]Fe[Formula: see text]O4, also known as NCMF for [Formula: see text], 0.02, and 0.04, which were successfully synthesized using a low-temperature sol-gel combustion process with nitrates as cations and citric acid (C6H8O7) as the combustion/chelating agent. In X-ray diffraction studies, cobalt incorporation resulted in a significant increase in lattice parameter from 8.31 to 8.36, as well as a significant increase in density from 5.42 to 5.52[Formula: see text]g/cm3; crystal size formation was observed in the range of 44.76[Formula: see text]nm to 48.54[Formula: see text]nm for all samples. Raman spectra analysis confirmed that single phase belongs to the Fd3m space group. Fourier transform infrared (FTIR) spectra were used to identify functional clusters and residual groups in all samples. UV–visible spectroscopy showed a redshift of 0.92[Formula: see text]eV for [Formula: see text]. The effect of dopants on nickel ferrites’ magnetization was observed in the range 52–59[Formula: see text]emu/g, indicating that all samples contain soft magnetic content. Antifungal activity of synthesized sample was analyzed against Aspergillus niger (MT675916) species of plant pathogenic fungi isolated from Capsicum during storage. Biological analysis designated that the sample for [Formula: see text] has shown a 100% potent antifungal activity against Aspergillus niger (MT675916) species. For [Formula: see text] treatment completely inhibits the growth of fungus after 7 days. Therefore, NCMF NPs can be used as applicant resources for industrial, medical, and biological applications.

Enhanced near-infrared transmission of ZnO-doped Y2O3–MgO nanocomposites with reduced light scattering due to decreased refractive index difference

Y2O3–MgO nanocomposites have received attention owing to their high optical and mechanical properties. However, the inevitable light scattering stemming from the refractive index difference between the two phases limits their applications in the near-infrared region. In this study, the grain boundary light scattering was reduced by doping ZnO into MgO. Y2O3–Mg1−xZnxO nanocomposites were fabricated by hot-press sintered nanopowders synthesized via the sol-gel combustion process. The addition of ZnO reduced the sintering temperature by almost 300 °C and reduced the average grain size by more than 50 nm. Transmittance of 75%–85% was maintained for all samples in the wavelength range of 2–6 µm. The near-infrared cut-on wavelength shifted from 1222 to 843 nm when the ZnO concentration was up to 25 mol%. This work demonstrates the potential of ZnO-doped Y2O3–MgO nanocomposites as infrared transparent ceramics over a wide infrared transmission range.

Optimization of sol-gel combustion synthesis for calcium looping CO2 sorbents, part Ⅰ: Effects of sol-gel preparation and combustion conditions

The sol-gel combustion synthesis is a superior method to prepare high-performance CaO-based sorbent which is applicable for flue gas decarbonization and thermochemical energy storage. To optimize this synthesis, this study investigated different preparation variables in the sol-gel formation process and combustion process. The effects of these variables on the cyclic CO2 sorption performance, micromorphology, and physical parameters of the prepared pure CaO sorbents were studied. First, worse cyclic performance was shown when the H2O/Ca2+ molar ratio was over 100:1, and the optimal ratio was 80:1. Second, the citric acid/calcium nitrate ratio influenced the formation of the complex as well as the gas production and adiabatic flame temperature in the combustion process, and the optimal molar ratio was 1:1. Third, the NH4NO3 and Ca-based precipitate would be produced when the pH value of the precursor solution was over 3. The optimal pH value was 2, and the carbonation conversion of the prepared sorbent reached 99% in the 2nd cycle within the 10 min carbonation at 650 °C under 15% volume CO2. After 20 cycles, the conversion was 70.4%. Fourth, a higher heating rate facilitated better cyclic performance and the optimal heating rate was 10 °C/min. Finally, a higher initial ignition temperature accelerated grain growth and particles agglomeration of the combustion product, and the optimal temperature was 300 °C.

Luminescence properties and energy transfer of Tb3+, Eu3+ co-doped YTaO4 phosphors obtained via sol-gel combustion process.

Tantalate is considered as a valuable and efficient luminescence host because of its intense absorption in the ultraviolet area and excellent chemical properties. In this work, a series of pure YTaO4:Eu3+ and/or Tb3+ crystals were prepared via a sol–gel combustion method. The morphology, structure, and optical properties of the samples were discussed in detail. The Eu3+, Tb3+ co-doped YTaO4 samples are consisted of small spherical particles of around 18 nm. The prepared YTaO4:Tb3+ and/or Eu3+ samples exhibit the characteristic wide excitation band around 210–300 nm, the characteristic narrow red emission of Eu3+ (5D0 → 7F2) transitions and green emission of the Tb3+ (5D4 → 7F5) transitions when excited by UV light. It is focused on the energy transfer processes from the YTaO4 to Tb3+ as well as Eu3+ ions and from Tb3+ to Eu3+ ions of YTaO4:Eu3+/Tb3+ phosphors. Color-tunable emissions are realized through adjusting the types of rare earth ion (Eu3+ and Tb3+) and relative doping concentrations excited by a single wavelength. That is to say, the obtained Tb3+ and Eu3+ co-doped YTaO4 phosphors have a promising prospect in lasers, white light diodes (WLED), fluorescent lamp, and field emission display devices, etc.

Low temperature synthesis of Lu3Al5-xGaxO12:Ce3+,Cr3+ powders using a sol-gel combustion process and its persistent luminescence properties

Lu3Al5-xGaxO12:Ce3+,Cr3+ powders were prepared using a sol-gel combustion (SGC) process. To clarify the effects of the preparation method on the phase formation and luminescence properties, Lu3Al3Ga2O12:Ce3+,Cr3+ powders were also prepared at different calcination temperatures using a solid-state reaction (SSR) process for comparison with the SGC process. The photoluminescence spectra of the synthesized powders consisted of strong bands of Ce3+ and weak peaks of Cr3+ within the green and red regions, respectively. A Lu3Al3Ga2O12:Ce3+,Cr3+ single phase can be achieved even at a low temperature of 1100 °C for the SGC process, whereas it is formed at a higher temperature of 1500 °C for the SSR process. The green emission intensities of the Lu3Al3Ga2O12:Ce3+,Cr3+ powders prepared using the SGC process were significantly higher than those prepared using the SSR process. This behavior can be explained using a crystal structure, particle morphology, and uniformity of the dopant distribution. For the Lu3Al5-xGaxO12:Ce3+,Cr3+ powders prepared using the SGC process, increasing the Ga content caused an increase in the lattice constant, resulting in a blue-shift of the green band of Ce3+. The synthesized powders exhibited a persistent luminescence, which resulted from the trapping and de-trapping behaviors between the Ce3+ and Cr3+ ions. The longest persistent luminescence was observed for the Lu3Al3Ga2O12:Ce3+,Cr3+ powders prepared at 1700 °C using the SGC process, lasting approximately 40 min.

Synthesis and antibacterial activity of iron manganite (FeMnO3) particles against the environmental bacterium Bacillus subtilis.

Nanocrystalline iron manganite powder was synthesized using the sol–gel combustion process, with glycine as fuel. It was further calcined at 900 °C for 8 h, resulting in the formation of a loose cubic FeMnO3 powder with a small specific surface area, net-like structure and plate-like particles as confirmed by XRD, N2 physisorption, FESEM and TEM analyses. The metal ion release was studied by ICP-OES and showed that less than 10 ppb of Fe or Mn ions were released by leaching in water, but 0.36 ppm Fe and 3.69 ppm Mn was found in LB (Luria–Bertani) bacterial medium. The generation of reactive oxygen species (ROS) was monitored in distilled water and bacterial medium and showed that FeMnO3 particles do not generate O2˙− ions with or without UV irradiation, but synthesize H2O2 and show an antioxidative effect. Besides the higher stability of FeMnO3 particles in aqueous solution they showed an inhibitory effect on Bacillus subtilis growth in LB medium even at low concentrations (0.01 mg ml−1), but not in BHI medium even at 1 mg ml−1. This study points out that the mechanism of antibacterial action of engineered metal oxides needs continued investigation and specific experimental controls.

In Situ X-ray Absorption Fine Structure Probing-Phase Evolution of CuFe2O4 in Nanospace Confinement.

The thermal transformation of Cu(NO3)2 and (Fe(NO3)3 into a CuFe2O4 spinel structure in the confined space of SBA-15 has been investigated. Interestingly, we observed the new formation mechanism of CuFe2O4 in SBA-15 via isolated metal ions (Cu2+ and Fe3+) surrounded by oxygen atoms, which gradually transformed to CuO and ferrihydrite. The latter evolved to maghemite spinel ferrite and reacted with CuO to form CuFe2O4 as the final species. In contrast, in the nonconfined space where the spinel was produced via a sol-gel combustion method, the nanostructure of CuFe2O4 immediately formed during the sol-gel combustion process and its crystallinity was improved after calcination. This is the first report on probing-phase formation using high-temperature in situ X-ray absorption fine structure.

Comparison of the effect of nickel and cobalt cations addition on the structural and magnetic properties of manganese-zinc ferrite nanoparticles

Abstract The aim of this study was to investigate the effect of nickel and cobalt cations on magnetic properties of manganese-zinc ferrite (MZF) nanoparticles. The nanoparticles were produced through sol-gel combustion process with citric acid as the fuel. Then the obtained nanoparticles were calcinated for 30 min at 500 °C. In order to characterize the compounds, four methods were employed, including X-ray diffraction (XRD), vibrating sample magnetometer (VSM), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). Spinel formation was confirmed by XRD and it was shown that the crystallite size in all samples was less than 12 nm (nm). In addition, FESEM images revealed that the nanoparticle size was less than 70 nm after calcination. Saturation magnetization (MS) and coercivity (HC) of the MZF nanoparticles are increased by adding Ni and Co cations.

Tuning the Magnetic Properties of ZnFe2O4 Nanoparticles Through Partial Doping and Annealing

The aim of this study was to investigate the effect of annealing temperature and cobalt cation (Co2+) doping on the magnetic properties of zinc ferrite (ZFO) nanoparticles. The nanoparticles were prepared through sol-gel combustion process with citric acid as the fuel. The obtained nanoparticles were annealed at several temperatures from 300 to 1000 °C for 2 h. Spinel formation was proved by X-ray diffraction (XRD) patterns, and the average crystallite size in all samples was estimated between 22 and 32 nm. It is worthwhile to mention that Fe2O3 and ZnO are detected as the medium phases. Meanwhile, Fe2O3 phase transformation to the other allotropes has happened around 400 °C and was characterized via the simultaneous thermal analysis (STA) and XRD. For higher annealing temperatures, diffusion has gradually been completed and, finally, the single phase of spinel structure was prepared at 1000 °C. In addition, field-emission scanning electron microscopy (FESEM) images revealed that the nanoparticle size after annealing was between 30 and 200 nm for the whole samples. The formation of the spinel phase was considered the most important factor on the magnetic properties of ZFO. Cobalt doping, annealing temperature, and also Fe2O3 phase were the main factors on changing magnetic properties. Paramagnetic nanoparticles with higher coercivity for doped samples rather than un-doped samples have been obtained.

Unique Spectral Overlap and Resonant Energy Transfer between Europium(II) and Ytterbium(III) Cations: No Quantum Cutting

AbstractSamples of the Ca3Sc2Si3O12 (CSS) host singly doped with Eu2+ or Yb3+, doubly doped with Eu2+ and Yb3+, and triply doped with Ce3+, Eu2+ and Yb3+ were synthesized by a sol–gel combustion process under reducing conditions. Unlike previous reports of Eu2+→Yb3+ energy transfer in other systems, the energy transfer is resonant in the CSS host and the transfer efficiency reaches 100 % for lightly doped samples. The transfer mechanism is multipolar rather than electron transfer for the sample compositions employed herein. The emission intensity of Yb3+ is further enhanced by co‐doping with Ce3+ in addition to Eu2+. The quantum efficiencies of the doped materials range between 9 % and 93 %.

Unique Spectral Overlap and Resonant Energy Transfer between Europium(II) and Ytterbium(III) Cations: No Quantum Cutting.

Samples of the Ca3 Sc2 Si3 O12 (CSS) host singly doped with Eu2+ or Yb3+ , doubly doped with Eu2+ and Yb3+ , and triply doped with Ce3+ , Eu2+ and Yb3+ were synthesized by a sol-gel combustion process under reducing conditions. Unlike previous reports of Eu2+ →Yb3+ energy transfer in other systems, the energy transfer is resonant in the CSS host and the transfer efficiency reaches 100 % for lightly doped samples. The transfer mechanism is multipolar rather than electron transfer for the sample compositions employed herein. The emission intensity of Yb3+ is further enhanced by co-doping with Ce3+ in addition to Eu2+ . The quantum efficiencies of the doped materials range between 9 % and 93 %.

In vitro bioactivity studies of larnite and larnite/chitin composites prepared from biowaste for biomedical applications

Larnite (Ca2SiO4) was synthesized by the sol–gel combustion process by using raw eggshell powder as a calcium source and urea as a fuel. The main focus of this work is to convert biowaste into a biomedical material at a low-processing temperature. X-ray diffraction (XRD) pattern confirms the phase purity of the larnite and Fourier transform infrared (FTIR) spectra confirms the presence of characteristic functional groups of larnite. Scanning electron microscopy (SEM) image shows agglomerated particles with cauliflower-like morphology and energy dispersive X-ray spectroscopy (EDX) confirms the presence of the stoichiometric ratio of required elements. Atomic force microscope (AFM) images reveal the presence of pores on the surface of spherical particles. Larnite/chitin composites were fabricated into scaffold with different ratios of bioceramic to biopolymer (70:30, 80:20) to investigate the influence of the polymer content on the apatite formation ability in simulated body fluid (SBF) medium. XRD pattern and FTIR spectra of the scaffold immersed in SBF shows apatite deposition within 5 days. The deposition of hydroxyapatite (HAP) on the scaffold surface increases with the increase in polymer content of the composite.

Ammonium citrate-assisted combustion synthesis and photoluminescence properties of Dy:YAG nanophosphors

Dy3+-doped yttrium aluminum garnet (YAG) nanocrystalline powders were synthesized by employing a sol–gel combustion process, in which triammonium citrate was used as both fuel reagent and dispersant. The influence of citrate-to-nitrate molar ratio (0–2) on slurry rheology, phase formation, composition, morphology, and particle size distribution of the Dy:YAG powders was evaluated systematically. The effects of Dy3+ dopant concentration (various from 1 to 3 at.%) and annealing temperature (1000–1300 °C) on the structural and optical properties of Dy:YAG phosphors were also investigated, and the chromaticity coordinates of the phosphor were calculated. Results show that pure Dy:YAG nanopowders were produced by calcining the combustion synthesis products with a citrate–nitrate ratio of 1 at or above 850 °C. Study of the luminescence behavior of the synthesized powders reveals that the phosphors exhibit greenish-blue emission pre-annealing and red emission post-annealing. Furthermore, emission band intensity is increased with an increase in both the Dy3+ dopant concentration and annealing temperature. The Dy:YAG phosphor’s temperature-dependent variation between greenish-blue and red luminescence emission makes it attractive as a potential candidate for applications in temperature monitoring of fuel sprays.

Phase Investigation and Multi Objective Optimization of Dielectric Behaviour of Bismuth Titanate–Calcium Copper Titanate Nanocomposites Using Grey Relational Grade Analysis

First time, bismuth titanate–calcium copper titanate (BTOX–CCTO1−X) composite materials were produced through sol–gel combustion process. X-ray diffraction analysis revealed that the obtained products were phase pure with dual phase composite system. Atomic percentage of each element present in the composite, observed by energy dispersive spectroscopy, was consistent with that in the raw materials as per stoichiometry. Field emission scanning electron microscopy showed evidence that the large CCTO grains embedded in small BTO grains and both co-existed with a bimodal distribution. The composite materials showed excellent dielectric behaviour that made them promising candidates for the high dielectric embedded capacitors. An efficient grey relational grade approach was introduced for improving the condition of major controlled parameters like frequency, operating temperature and molar composition and optimizing these parameters to obtain maximum dielectric constant and minimum dielectric loss simultaneously.