Solid-state Combustion Method Research Articles

CO2 Methanation: Nickel-Alumina Catalyst Prepared by Solid-State Combustion.

The development of solvent-free methods for the synthesis of catalysts is one of the main tasks of green chemistry. A nickel–alumina catalyst for CO2 methanation was synthesized by solid-state combustion method using hexakis-(imidazole) nickel (II) nitrate complex. Using X-ray Powder Diffraction (XRD), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Hydrogen temperature-programmed reduction (H2-TPR), it was shown that the synthesized catalyst is characterized by the localization of easily reduced nickel oxide on alumina surface. This provided low-temperature activation of the catalyst in the reaction mixture containing 4 vol% CO2. In addition, the synthesized catalyst had higher activity in low-temperature CO2 methanation compared to industrial NIAP-07-01 catalyst, which contained almost three times more hard-to-reduce nickel–aluminum spinel. Thus, the proposed approaches to the synthesis and activation of the catalyst make it possible to simplify the catalyst preparation procedure and to abandon the use of solvents, which must be disposed of later on.

Facile and eco-friendly combustion synthesis of NiO particles for photodegradation studies

Nickel oxide (NiO) particles were synthesized by varying temperature through solid-state combustion method. The effects of annealing temperatures such as 650, 750, 850, 950, and 1050 °C, on the crystallite size, absorption properties, and photodegradation of methylene blue (MB) were studied. Progressive enhancement of crystallinity of the samples was clearly observed in FE-SEM images. The photocatalytic degradation of MB with different crystallite sizes was studied, showing that degradation increases with increasing the sample's crystallinity. The percentage of degradation of MB dye is found to be 96% in three hours. Furthermore, the density functional theory (DFT) studies have been performed for NiO to understand the linear optical and chemical properties. The DFT results are found to have a good correlation with the experimental findings.

Effect of Firing Conditions on Phase Formation, Microstructure, and Electrical Properties of (K0.5Na0.5)(Nb0.7Ta0.3)O3 Ceramics Synthesized by Solid-State Combustion Method

The effect of the firing conditions on the phase formation, microstructure, and electrical properties of (K0.5Na0.5)(Nb0.7Ta0.3)O3 (KNNT) ceramics synthesized by the solid-state combustion technique using glycine as fuel has been investigated. All samples were calcined at 600°C to 800°C for 2 h and sintered at 1150°C to 1190°C for 2 h to 5 h. Pure KNNT powders were produced after calcination at 600°C for 2 h. The average particle size increased when the calcination temperature was increased. The KNNT powder calcined at 600°C for 2 h showed rather square morphology with average particle size of ∼ 160 nm. The x-ray diffraction (XRD) analysis results for the ceramics revealed the presence of orthorhombic (O) and tetragonal (T) phases in all samples. When sintering at 1150°C for 4 h, the O:T ratio was 50:50, as verified by the Rietveld refinement technique. The average grain size, density values, and dielectric properties tended to increase when the dwell time was increased from 2 h to 4 h, but then degraded. The KNNT ceramic produced at the optimum firing condition (1150°C for 4 h) showed good crystalline morphology, the highest density (ρ = 5.28 g/cm3), the highest dielectric constant (eC = 5002), and good ferroelectric behavior (Pr = 18.50 μC/cm2 and Ec = 9.04 kV/cm).

Comprehensive experimental study on production of vertically aligned ZnO nanorod thin films and their electrical, optical and antimicrobial properties

One-dimensional (1D) zinc oxide (ZnO) nanomaterials (e.g. nanorods, nanowires) are the most important due to their electrical and optical properties. As the surface-to-volume ratio in ZnO nanorods (NRs) is very high, the surface states have a crucial role on optical and other properties. So, determination of the production parameters of the ZnO-NRs is important. In this study, a well-aligned ZnO-NRs thin film was produced via the sol–gel and hydrothermal methods. For this purpose, in the first step, a ZnO seed layer was coated onto a cleaned microscope glass slide (sizes of 1.25 × 3.75 cm) by the sol–gel spin coating method. In the second step, ZnO-NRs were grown on the ZnO seed layer by the hydrothermal method. Production parameters for the first step, such as type of the zinc salt; type of the solvent; solution concentration; type of the stabilizer; ageing time process of the solution; spin speed; duration of the spin process; number of repeated coating cycle; heating treatment temperature between coating cycles; duration between coating cycles; final heating treatment temperature and final heating treatment duration of the ZnO seed layer, were obtained. Then similar optimization processes were repeated for the second stage for the ZnO-NRs. The crystal structure, morphological and optical properties of all the produced samples were characterized via X-ray diffraction (XRD) spectroscopy; scanning electron microscopy (SEM); and ultraviolet–visible (UV–Vis) spectroscopy. For comparison, ZnO-NR powders were produced via the mechanochemical solid-state combustion method. The electrical conductivity and optical transparency of the ZnO-NR thin film samples were higher than those of the ZnO-NR powder sample. It was also observed that the well-aligned ZnO-NR thin film sample had a higher bactericidal effect against Bacillus thuringiensis than the ZnO-NR powder sample.

Facile solid-state combustion synthesis of Al–Ni dual-doped LiMn2O4 cathode materials

A series of aluminum and nickel (Al–Ni) co-doped LiAl0.15NixMn1.85−xO4 composites are prepared through a facile solid-state combustion method. All the as-obtained materials show a spinel structure and analogous spherical morphology with uniform particle distribution. Moreover, the synergistic merits of Al and Ni dual substitutions endow the spinel LiMn2O4 with an elevated Mn average valence state of 3.59 and relatively alleviative Jahn–Teller distortion. Among these samples, the LiAl0.15Ni0.03Mn1.82O4 (LANMO-0.03) cathode exhibits an optimal electrochemical performance with the discharge capacities of 103.3 mAh g−1 and 102 mAh g−1 at 1 C and 5 C in the first cycle, and the capacity retentions are 72.0% and 68.6% after 1000 cycles, respectively. Even at 1 C and high temperature of 55 °C, an excellent capacity retention remained to be 76.6% after 200 cycles. Furthermore, the LANMO-0.03 has good Li+ diffusion capability during charge/discharge, the DLi+ value of the LANMO-0.03 (1.65 × 10–11 cm2∙s−1) is higher than that of the LiAl0.15Mn1.85O4 (LAMO) (8.12 × 10–12 cm2∙s−1), and the charge transfer resistances of the LAMO and LANMO-0.03 samples are almost the same at 150 Ω before cycling but decrease to 130 Ω and 95 Ω after 1000 cycles at 1 C, respectively. These results demonstrate that the Al–Ni co-doped strategy can enhance the structural stability and provide stable Li+ diffusion channel during the long cycles even at elevated temperature. Meanwhile, the facile solid-state combustion approach can also be extended to the preparation of other dual cation-doped electrode materials.

Production of hydrogen-rich syngas and multiwalled carbon nanotubes by biogas decomposition over zirconia supported iron catalysts

A set of Fe/ZrO2 catalysts were successfully synthesized by a facile urea-assisted solid-state combustion method, and their catalytic test was evaluated for the thermal decomposition of undiluted-biogas into hydrogen-rich syngas and multiwalled carbon nanotubes (MWCNTs). The as-prepared catalysts were characterized by X-Ray diffraction (XRD), Scanning and Transmission electron microscopy (SEM and TEM), Nitrogen-physisorption, X-ray photoelectron spectroscopy and Temperature programmed reduction analyses. The iron was found in the form of hematite and metallic-iron in the fresh and reduced catalysts respectively. A suitable metal-support interaction due to the fine surface dispersion of iron species on ZrO2 was observed in the catalysts. The N2-physisorption analysis indicated the reduced surface area of the catalysts after iron loading. However, it does not influence the catalytic efficiency since the metal amount and metal-support interaction was determined to play the main role. The Fe/ZrO2 catalysts exhibited improved catalytic efficiency. With increasing the amount of iron and increasing the reaction temperature, the CH4 and CO2 conversions were increased significantly. A highest CH4 and CO2 conversions of 92% and 89% respectively, with an H2/CO ratio of ∼2.25 were obtained for the 50%Fe/ZrO2 catalyst at 900°C. The enhanced catalytic performance could be attributed to the fine-surface dispersion of iron-nanocrystals on ZrO2. Moreover, the MWCNTs were characterized by XRD, SEM, TEM and Raman analyses for their structural properties.

Enhancing the durable performance of LiMn2O4 at high-rate and elevated temperature by nickel-magnesium dual doping

Various nickel and magnesium dual-doped LiNixMg0.08Mn1.92−xO4 (x ≤ 0.15) were synthesized via a modified solid-state combustion method. All as-prepared samples show typical spinel phase with a well-defined polyhedron morphology. The Ni-Mg dual-doping obviously decreases the lattice parameter that gives rise to the lattice contraction. Owing to the synergistic merits of metal ions co-doping, the optimized LiNi0.03Mg0.08Mn1.89O4 delivers high initial capacity of 115.9 and 92.9 mAh·g−1, whilst retains 77.1 and 69.7 mAh·g−1 after 1000 cycles at 1 C and high current rate of 20 C, respectively. Even at 10 C and 55 °C, the LiNi0.03Mg0.08Mn1.89O4 also has a discharge capacity of 92.2 mAh·g−1 and endures 500 cycles long-term life. Such excellent results are contributed to the fast Li+ diffusion and robust structure stability. The anatomical analysis of the 1000 long-cycled LiNi0.03Mg0.08Mn1.89O4 electrode further demonstrates the stable spinel structure via the mitigation of Jahn-Teller effect. Hence, the Ni-Mg co-doping can be a potential strategy to improve the high-rate capability and long cycle properties of cathode materials.

Synthesis, characterization and antibacterial study of Ag doped magnesium ferrite nanocomposite

Nanomaterials are attracted a great deal of attention from scientific community due its unique properties and applications. The small size ferrites have opened up the door for intensive research to utilize their properties for biomedical applications. Ferrite nanomaterials like MgFe2O4 and its silver doped nanocomposites (Ag– MgFe2O4) have been prepared using solid state combustion method using polyvinyl alcohol (PVA) as a fuel. The structure of as prepared ferrites and its silver doped nanocomposites were characterized using X-ray diffraction (XRD) tool and morphology by Scanning Electron Micrograph (SEM) tool respectively. Presence of the metals in the ferrite and its composite was confirmed by EDX pattern. Bonding nature in the composite is well studied by Fourier transform infrared (FT-IR) tool. Antibacterial activity study of the nanocomposite is carried out against various bacteria. Ag doped magnesium ferrite shows moderate activity against bacteria.

Luminescent properties of stoichiometric Er:LiTaO3 submicron particles synthesized by a modified solid-state combustion route

Erbium-doped lithium tantalate submicron phosphor particles were produced by an efficient one-step solid-state combustion method. Well-crystallized products with uniform grain morphology were confirmed by X-ray diffraction and field-emission scanning electron microscopy. Thermogravimetric and differential thermal analysis were used to further analyze the combustion reaction process. In addition, down- and up-conversion luminescence (DCL, UCL) as well as the relationship between luminescence intensity and erbium doping level were revealed. The luminescence spectra for the UCL processes under different excitation intensities showed a remarkable three-photon absorption phenomenon in Er-doped system. These results demonstrate that the modified solid-state combustion method possesses practical value for large-scale synthesis of rare earth-doped submicron phosphors and has great potential for application in solid-state laser and display fields.

Effect of the firing temperatures on the phase formation, microstructure and electrical properties of BaTi0.91 Sn0.09O3 ceramics synthesized via the solid state combustion method

BaTi0.91Sn0.09O3 (BTS) ceramics were synthesized by the solid state combustion method with glycine as the reducting agent and metal nitrates as the oxidants. The calcination and sintering temperatures were in the range of 1200 °C–1300 °C and 1300 °C–1450 °C, respectively, for 2 h. Pure perovskite powders were obtained from the samples calcined at ≥1275 °C for 2 h. The crystal size calculated by Scherrer equation was in the range of 22–30 nm. XRD results of the sintered ceramics showed the coexistence of the tetragonal (T) and orthorhombic (O) phases in all samples, and were confirmed by Rietveld refinement. The grain sizes increased from 9.04 to 29.83 µm when the sintering temperatures increased from 1300 °C–1450 °C for 2 h. The highest density (5.95 g⋅cm−3), large piezoelectric strain (d33* = 830 pm/V) and best dielectric constant (εr = 14841) were obtained from the sample sintered at 1350 °C for 2 h. This study clearly demonstrates the potential of the solid state combustion method for producing high density and good dielectric properties in BTS ceramics.

Phase Formation, Dielectric, Ferroelectric and Magnetic Properties of Cr2O3 Doped (Ba0.85Ca0.15)(Ti0.90Zr0.10)O3 Ceramics

In this paper, we studied the effect of Cr2O3 doping (0–0.8 wt%) on the phase formation, dielectric, ferroelectric and magnetic properties of (Ba0.85Ca0.15)(Ti0.90Zr0.10)O3 (BCTZ) ceramics prepared by the solid state combustion method. All samples were prepared with a calcined and sintered temperature of 1050 °C and 1450 °C, respectively, for 2 h. The results of the XRD patterns showed the coexistence between the tetragonal (T) and orthorhombic (O) phases for all samples, and the tetragonal phase increased with increasing amounts of Cr2O3. The dielectric constant decreased when Cr2O3 increased. The P-E hysteresis loops of the BCTZ ceramics doped with Cr2O3 between 0 and 0.2 wt% showed slim and saturated loops. By increasing Cr2O3 doping from 0.4 to 0.8 wt%, the P-E loops were unsaturated and a leakage current was produced. The undoped BCTZ ceramics exhibited diamagnetic behavior. The sample with 0.2 wt% Cr2O3 showed ferromagnetic behavior. Increasing Cr2O3 doping from 0.4 to 0.8 wt%, caused the ceramics to exhibit paramagnetic behavior. Doping with Cr2O3 led to improper ratios between the tetragonal and orthorhombic phases, decreased density and increased porosity which caused a decrease in the electric properties.

Phase transition, electrical properties and large strain response in lead-free (1-x-y)BNT-xBKT-yKNN ceramics

Lead-free piezoelectric composition ceramics of (1-x-y)Bi0.5Na0.5TiO3–xBi0.5K0.5TiO3–yK0.5Na0.5NbO3; (1-x-y)BNT-xBKT-yKNN (with 0.18≤x ≤ 0.26 and 0≤y ≤ 0.07) were fabricated using the solid-state combustion method. The structure exhibited co-existing rhombohedral and tetragonal phases for all samples. Increasing of x and y contents, the average grain size decreased from 1.42 μm to 1.02 μm and 1.25 μm to 0.70 μm, respectively. The diffuseness exponent (γ) of the ceramics was between 1.817 and 1.939 for x composition and between 1.766 and 1.999 for y composition indicating that the (1-x-y)BNT-xBKT-yKNN solid solutions had diffuse phase transition behavior. The change in the P-E loops of the ceramics indicated that the long-range ferroelectric order of the samples was disturbed and turned to the polar nano-regions (PNRs) with increased x and y contents. The polarization hysteresis loop transformed from well saturated typical ferroelectric, to pinched, and then to the relaxor state with increased x and y content. The addition of BKT and KNN contents significantly enhances the field-induced strain in BNT ceramics. The largest Smax of 0.25% corresponded to a high-field effective d33* of 509 pm/V, which was found in the composition of 0.79BNT-0.20BKT-0.01KNN.

Efficacy of biomaterial based photocatalytic composite in treating dye pollutants

A biomaterial based photocatalytic composite, hydroxyapatite–TiO2–ZnO (HAp-TiO2–ZnO) has been developed following a solid-state combustion method while its efficacy was investigated through the photodegradation of (i) aquatic solution of synthetic dye, methylene blue (MB); and (ii) real textile dye effluent. The degradation profile was explored considering several factors, e.g.: (i) initial dye concentration; (ii) illumination span; (iii) dose of photocatalyst; and (iv) pH of targeted dye solution. The photodegradation was performed in both indoor and outdoor environment using halogen lamp (500 W) and sunlight respectively. Observed photodegradation revealed that though the photocatalytic composite effectively decomposed methylene blue at various extents under different experimental conditions but a dose of 0.5g photocatalyst/100 mL substrate solution (10×10-6 M methylene blue solution at pH 4) expedited optimal degradation (~ 97%) at 2 hours’ time interval. On the other hand though it was possible to degrade the textile effluent to some extent by illuminating through halogen lamp and sunlight but the success rate did not exceed 50%.Bangladesh J. Sci. Ind. Res.53(2), 139-144, 2018

Study on Electrochemical Performance of LiMg0.06Mn1.94O4 Synthesized by Solid-State Combustion Method

Study on Electrochemical Performance of LiMg0.06Mn1.94O4 Synthesized by Solid-State Combustion Method

Effect of firing temperatures on properties of BNT-BCTZ-0.007mol%BFCO lead free piezoelectric ceramics synthesized by the solid state combustion method

Abstract In this study, the effects of calcination temperature (550–750 °C for 2 h) and sintering temperature (1100–1200 °C for 2 h) on the phase formation, microstructure, electric and magnetic properties of the 0.94Bi 0.5 Na 0.5 TiO 3 -0.06(Ba 0.85 Ca 0.15 )(Ti 0.90 Zr 0.10 ) lead-free piezoelectric ceramic doped with 0.007 mol%Bi 2 FeCrO 6 (BNT-BCTZ-BFCO) were investigated. These ceramics were prepared by the solid state combustion technique using glycine as fuel. The pure perovskite phase was observed in the BNT-BCTZ-BFCO powders attained at the calcined temperature of 650 °C for 2 h. The morphology of the BNT-BCTZ-BFCO powders exhibited an almost-spherical shape and the average particle size increased when the calcination temperature increased from 550 to 750 °C. TEM results of pure BNT-BCTZ-BFCO powder calcined at 650 °C for 2 h showed rounded shapes and the average particle size was ∼ 200 nm. The XRD results of all ceramics exhibited a single perovskite structure with the co-existence of the rhombohedral and tetragonal phases. The average grain size increased with increasing sintered temperature. The density, dielectric constant (e at T r and T m ) and piezoelectric constant (d 33 ) increased when the sintered temperature increased up to 1150 °C and then reduced in values. At a sintered temperature of 1150 °C, BNT-BCTZ-BFCO ceramic showed the highest relative density (97.2%), maximum dielectric properties (e at T r = 1783 and e at T m = 5117), d 33 value (178 pC/N), d * 33 (549 pm/V) and the remnant polarization (P r = 34.66 µC/cm 2 ). At higher sintering temperatures, the properties of BNT-BCTZ-BFCO ceramics decreased due to the evaporation of Bi and Na. All ceramics exhibited the paramagnetic behavior and the magnetization increased with increasing sintering temperature.

Excellent piezoelectric and ferroelectric properties of KNLNTS ceramics with Fe2O3 doping synthesized by the solid state combustion technique

Lead-free piezoelectric (K0.44Na0.52Li0.04)(Nb0.84Ta0.10Sb0.06)O3 (KNLNTS) ceramics doped with Fe2O3 at compositions between 0 and 1.0 wt% were prepared by the solid state combustion method with glycine used as the fuel. The effect of Fe2O3 doping on the phase formation, morphology, density, electric and magnetic properties was investigated. The crystal structure of the ceramics doped with Fe2O3 ≤ 0.6 wt% exhibited a pure perovskite phase, while the secondary phases of FeNbO4 and FeTaO4 were detected in the ceramics doped with Fe2O3 > 0.6 wt%. The phase formation changed from orthogonal phase to the dominated orthorhombic phase and cubic phase when Fe2O3 doping increased from 0 to 1.0 wt%. The microstructure exhibited a rectangular shape grain in all samples. The average grain size and the density of the ceramics increased from 1.52 to 2.10 μm and 4.42–4.65 g/cm3 by increasing Fe2O3 content from 0 to 0.6 wt% then dropping in a value with further Fe2O3 doping. The highest dielectric constant (εr at Tr = 2782 and εm at TC = 7520), excellent ferroelectric properties (Pr = 27.9 μC/cm2 and Ec = 9.9 kV/cm) and the highest d33 (311 pC/N) were obtained from the sample doped with 0.6 wt% Fe2O3. This sample exhibited ferromagnetic behavior with Mr and Hc of 0.015 emu/g and 143 Oe, respectively. The dopant of Fe2O3 at appropriate amount and the solid state combustion technique are a new alternative for increment and improvement of densification, microstructure, piezoelectric, ferroelectric and ferromagnetic properties.

Upconversion Luminescence Properties of Y2Mo4O15: Yb3+, Er3+ by Solid State Combustion Method.

The Yb3+ and Er3+ co-doped yttrium molybdenum oxide upconversion phosphors were prepared by the solid state combustion method using urea as fuel at ignition temperature of 550 °C. The upconversion phosphors were characterized by X-ray diffraction (XRD), scanning electronic microscope (SEM), and photoluminescence spectra XRD results revealed the samples were pure monoclinic Y2Mo4O15 phases when the sintering temperature was 700 °C. SEM micrographs illustrated particle size distribution was almost uniform with an average particle diameter of about 0.5-1.0 µm. The obtained Y2MO4O15: Yb3+, Er3+ presents bright and pure green upconversion luminescence during daylight pumping under 980 nm LD. According to the analysis of upconversion luminescent mechanism, the cross relaxation processes of Er3+ ions restrained the electron population of red emission energy level, which not only increased the green light upconversion emissions fluorescent branching ratio (IGIR = 153:1) but also enhanced the efficiency and purity of green light emissions.

Formic acid-assisted synthesis of highly efficient Cu/ZnO catalysts: effect of HCOOH/Cu molar ratios

Metallic Cu/ZnO catalysts were directly prepared by a formic acid-assisted solid-state combustion method without further reduction.

Efficient Synthesis of Stoichiometric Lithium Tantalate Powder by a Solid-State Combustion Route

Stoichiometric lithium tantalate (SLT) powder was prepared by a solid-state combustion method from the raw powder of Li2CO3, Ta2O5, and urea, which is characterized by a short reaction time and relatively low temperatures. The urea, added into the mixture (Li2CO3 and Ta2O5), serves as a fuel and an inducer to produce intermediate compounds and cause a solid-state combustion reaction as well. Various temperatures and urea contents were employed to optimize the synthesis of SLT. The chemical process and the quality of LiTaO3 powder were investigated by X-ray diffraction, electron microscope, thermogravimetry, and Raman spectroscopy. The optimized synthesis shows great capability to reduce the volatilization of lithium-ion and presents an efficient way to manufacture high-quality SLT.

Rapid synthesis of high-cycling performance LiMgxMn2–xO4 (x ≤ 0.20) cathode materials by a low-temperature solid-state combustion method

A series of LiMgxMn2-xO4 (x ≤ 0.20) cathode materials were rapidly synthesized at a low temperature of 500°C for 1h by a solid-state combustion process. The morphologies and crystal structures of LiMgxMn2-xO4 were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. All LiMgxMn2-xO4 samples exhibited a single phase LiMn2O4 spinel structure with good crystallinity. The linear decrease of the lattice parameters with the increase of Mg-doping content could suggest that Mg2+ ions had put into the spinel LiMn2O4 lattice substituting for Mn3+. The effect of Mg2+ ions on the electrochemical performance of LiMgxMn2-xO4 was investigated by galvanostatic charge-discharge test, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results showed that the Mg-doped LiMn2O4 possessed better cycling stability, for example, a capacity retention of 93.2% for LiMg0.08Mn1.92O4 after 150 cycles at 0.2C.