Low-temperature Combustion Synthesis Research Articles

Fe-doping on CaV2O6 for oxygen vacancy controlling lithium storage

Currently, alkaline earth metal vanadates as the anode materials for lithium-ion batteries (LIBs) are gradually sparking attention due to their low cost, environmental friendliness, high theoretical capacity and safety. However, their practical application is still hampered by the fast capacity degradation resulting from the prolonged cycling condition and intrinsic low electrical conductivity. Herein, single-crystal Fe-doped CaV2O6 is prepared via the low-temperature combustion synthesis route. The Fe-doping accelerates the generation of low-valence-state vanadium in CaV2O6–2%Fe, leading to the production of oxygen vacancies for maintaining electroneutrality. The versatile design of CaV2O6–2%Fe improves the electron conductivity and promotes the Li-ion diffusion rate based on the generated dual defects of interstitial atoms of Fe and oxygen vacancies accordingly. As expected, the CaV2O6–2%Fe electrode exhibits superior rate capacity of 96.6 mA h g−1 at 5 A g−1 and a remarkable capacity retention of 125.6 mA h g−1 after 1000 cycles at 1 A g−1. Additionally, the partial decomposition of CaV2O6 during the initial lithiation stage, and the formation of amorphous Li–V–O in the subsequent cycle can be used to depict the lithium storage mechanism of CaV2O6–2%Fe.

Promoting effect of oxygen vacancies in Co/CoAl2O4 catalyst steered with a straightforward method on hydrogenation of furfural to 2-methylfuran

The exploitation of base metal catalysts to upgrade biomass chemicals remains a daunting challenge and a sustainable strategy. Here, a series of Co-Al spinel catalysts are rapidly prepared by low-temperature solution combustion synthesis for hydrogenation of furfural (FF) to 2-methylfuran (2-MF), in which oxygen vacancies are easily manipulated by regulating the proportion of glycine in the ingredients. The screened Co/CoAl2O4 incorporating adequate oxygen vacancies yields 2-MF over 97 % at 150 ℃ for 5 h, rivalling the state-of-the-art catalysts to date. Characterizations and DFT calculations attribute the success to oxygen vacancies, which not only enhance the adsorption of FF by changing the adsorption geometry, but also facilitate the hydrogen spillover from Co to substrate by moving down the d-band center of CoAl2O4. This study provides a versatile methodology for the efficient and low-temperature preparation of spinel and the construction of defect engineering on catalysts, enlightening the design of phenomenal catalysts.

Porous Mn-doped Fe3O4 as lithium-ion battery anode via low-temperature combustion synthesis

The preparation of Mn-doped Fe3O4 was carried out using the low-temperature combustion synthesis (LCS) method through the addition of Mn2+ to the ferric nitrate-glycine system. Here, we investigate the mechanism of the redox reaction involving Fe3+ and Mn2+ ions, and the results reveal that for the synthesis of porous Mn-doped Fe3O4, the presence of Mn2+ in the raw material is necessary. The carbon source, such as ethylene glycol, glucose, and polyethylene glycol-4000, serves as both reducing and complexing agent, leading to the formation of more pores during the combustion reaction. Increased specific surface area of combustion products. By conducting a LCS reaction in a solution with added ethylene glycol, Mn-doped Fe3O4 was obtained for lithium ions batteries as anode material, at current density of 5 A g−1, it demonstrates an impressive capacity retention rate of 90% with a high capacity of 452.5 mA h g−1 after 650 cycles. Similarly, Mn-doped Fe3O4 obtained with the addition of polyethylene glycol shows a capacity retention rate of 89.7% after 1500 cycles. Our findings provide a new and innovative method for the preparation of manganese ferrites with a porous structure and a new research approach for developing metal oxide anode materials.

Low-Temperature Combustion Synthesis and Characterization of Co-Containing Catalysts Based on Modified Silica Gel

Low-Temperature Combustion Synthesis and Characterization of Co-Containing Catalysts Based on Modified Silica Gel

Thermoelectric Properties of Cu2Se Compound Fabricated at Low-Temperature Combustion Synthesis as a New Approach with Alternative Techniques

Thermoelectric Properties of Cu2Se Compound Fabricated at Low-Temperature Combustion Synthesis as a New Approach with Alternative Techniques

Enhanced up-conversion emission of fluoride phosphor in the dual-fuel system under 1550 nm excitation

A 1.5 μm multi-component fluoride nanocrystal PbxNay-nLinYzF2x+y+3z+3m: Er3+m was synthesized by the low temperature combustion synthesis (LCS) method. On the basis of the orthogonal experiment and optimization experiment, Li+ ion was introduced into the matrix and the dual-fuel system was established, and the up-conversion luminescence intensity was enhanced by changing the matrix composition and improving the process methods. The results show that when the concentration of Li+ ion is 2.07 mol%, the fuel consumption in the dual-fuel system is 2.2 stoi., 0.7 stoi., the up-conversion luminescence intensity is obviously improved. The structure and morphology of samples were analyzed by the X-ray diffraction (XRD) and scanning electron microscopy (SEM), and a schematic model of physical mechanism for the luminescence intensity of Li+ ion enhanced materials was confirmed. The exothermic characteristics of the dual-fuel system were analyzed by the differential scanning calorimetry and thermogravimetric analysis (DSC-TGA). The influence of the introduction of Li+ ion and the dual-fuel system on the luminescence intensity was discussed in detail.

Low-Temperature Combustion Synthesis of Halloysite-Based Catalysts for the Deep Oxidation of Hydrocarbons and Carbon Monoxide and the Methanation of Carbon Dioxide

Low-Temperature Combustion Synthesis of Halloysite-Based Catalysts for the Deep Oxidation of Hydrocarbons and Carbon Monoxide and the Methanation of Carbon Dioxide

Reaction Model and Mechanism of Preparing (Al2O3 + C) Precursor for Carbothermal Synthesis of AlN by a Modified Low Temperature Combustion Synthesis Method.

The preparation of a homogeneous mixture of (Al2O3 + C) precursor is the key step for the successful synthesis of AlN powders by the carbothermal reduction and nitridation method. In the present work, the homogeneous (Al2O3 + C) precursor prepared by a modified low temperature combustion synthesis (MLCS) method by using aluminum nitrate, glucose, and urea as materials exhibited high reaction activity. Furthermore, in order to absolutely control the MLCS process and continuously improve the properties of (Al2O3 + C) precursor, the reaction model of preparing precursors from various molar ratios of urea to aluminum nitrate (U/Al) was investigated by carrying out thermodynamic calculation and by performing experiments in the present work. The whole process was found to involve various phenomena. First, the type and amount of various generated nitrogen-containing gases (N2, NO, N2O, N2O3, N2O4, and NO2) vary with the change of U/Al during combustion process. Second, under the present experimental condition of ignition temperature, the decomposition reaction of aluminum nitrate is more prone to occur than the combustion reaction of urea. Third, the real reaction system with U/Al = 2.5 reaches the highest combustion temperature which is well consistent with the propellant chemical theory. The occurrence of above phenomena was discussed in detail. Moreover, the reaction mechanism of synthesizing precursor from U/Al = 1 with high reaction activity was investigated by using various techniques such as FTIR, XRD, and DTA.

Structural and Thermal Properties of a Selected Host Crystal Lattice: Exploration of Inherent Possibilities

Host Ba2MgSi2O7 phosphor was successfully prepared via low temperature combustion synthesis route. The phase identification of the prepared phosphor was done with the help of powder XRD technique. The XRD pattern of the phosphor revealed its monoclinic crystal symmetry with a space group C2/c. The XRD pattern have well clarified with JCPDS PDF card no. #23-0842. The average crystallite size was calculated as 42nm and crystal lattice strain size calculated as 0.24, respectively. It is acquired that the sample UV exposed for 15min gives optimum TL intensity at 112.190C temperature and displays single TL glow peak. On the basis of TL glow curve, it can be suggested that the Ba2MgSi2O7 (BMS) phosphor is an efficient host lattice but not a better TL phosphor. In our present study, we have discussed on the XRD, FESEM and thermo-luminescence (TL) characteristics as well as different kinetic parameters of this phosphor.

Enhanced dual-wavelength up-conversion luminescence and temperature sensitivity of NaYF4:Yb3+, Er3+ phosphors by Bi3+ introducing

The up-conversion composite fluoride phosphor BixNayYzF3x + y+3z +3z+3m+3n: Er3+m, Yb3+n were synthesized using the optimized low-temperature combustion synthesis (LCS) method. The optimal formula was determined by step-by-step orthogonal experiments. The effects of the introduction of Bi3+ ions on phase formation and fluorescence intensity were systematically studied. The results indicate that introducing 10 mol% Bi3+ ions can substantially strengthen the dual-wavelength up-conversion fluorescence intensity of the sample. Then the temperature sensitivity of the sample is calculated, indicating that the sample has good temperature sensitivity and can be used as an effective material for temperature sensors. X-ray diffraction and scanning electron microscopy (SEM) were used to analyze the phase composition and morphology of the phosphor. The product exhibits characteristic emission of Er3+ ions under the excitation of 1550 nm ＆ 980 nm dual-wavelength, and its luminescence mechanism was studied. This work provides new ideas for studying photothermal dual response up-conversion fluoride phosphors under excitation at 1550 nm & 980 nm.

Green synthesis of CuO nanoparticles using Mimosa pudica leaf extract for antibacterial activity

Herein, we report the preparation of copper oxide nanoparticles (NPs) by low temperature combustion synthesis using Mimosa pudica leaf extract as fuel material. The synthesized particles are well crystalline in nature and average crystallite size was found to be 27–40 nm. The morphology of the copper oxide nanoparticles is weakly bounded agglomerated. Further, as-formed CuO NPs exhibit significant antibacterial activity against pathogenic bacterial strains namely Gram –ve Escherichia coli, Gram + ve bacteria Staphylococcus aureus.

Nonlinear Isotherm and Kinetic Modeling of Cu(II) and Pb(II) Uptake from Water by MnFe2O4/Chitosan Nanoadsorbents

Researchers are in continuous search of better strategies to minimize, if not prevent, the anthropogenic release of toxic heavy metals, such as Cu(II) and Pb(II), into drinking water resources and the natural environment. Herein, we report for the first time the low-temperature combustion synthesis of magnetic chitosan-manganese ferrite in the absence of toxic cross-linking agents and its removal of Cu(II) and Pb(II) from single-component metal solutions. The nonlinear Langmuir model best described the isotherm data, while the nonlinear pseudo-second order model best described the kinetic data, signifying monolayer Cu(II) or Pb(II) adsorption and chemisorption as the rate-determining step, respectively. Adsorption capacities by magnetic chitosan-manganese ferrite obtained for both metals were consistently higher than those by manganese ferrite, indicating that chitosan enhanced the performance of the magnetic adsorbent. The maximum adsorption capacities of magnetic chitosan-manganese ferrite for Cu(II) and Pb(II) were 14.86 and 15.36 mg g−1, while that of manganese ferrite were 2.59 and 13.52 mg g−1, respectively. Moreover, the adsorbents showed superior binding affinity and sorption for Pb(II) than Cu(II) owing to the stronger ability of the former to form inner-sphere complexes with manganese ferrite and magnetic chitosan-manganese ferrite. Finally, thermodynamic studies revealed that the uptake of either Pb(II) or Cu(II) by magnetic chitosan-manganese ferrite was spontaneous and endothermic. The as-prepared adsorbent was characterized for morphology, elemental composition, surface functional sites, and particle size using scanning electron microscopy, energy dispersive spectroscopy, Fourier transform infrared spectroscopy, and dynamic light scattering technique, respectively.

Low-temperature combustion synthesis method to prepare Na+-doped ultrafine micron-sized γ-Ce2S3 bright red pigments

In this study, the preparation of Na+-doped γ-Ce2S3 bright red pigments by low-temperature combustion synthesis method (abbreviated as LCS) was reported. The effects of different molar ratios for complexing agent and Ce salt (abbreviated as n(EDTA:Ce)) on the particle size and morphology of the precursors as well as the particle size and chromaticity of the pigments obtained after sulfidation were systematically investigated. The results showed that when n(EDTA:Ce) ​= ​2.0, the obtained precursor particles were fluffy, and the average particle size of the pigments obtained by sulfidation was only 1.14 ​μm. At same sulfidation condition, the average particle size of the pigments prepared by conventional gas-solid phase method (abbreviated as GS) reached 5.42 ​μm. The pigments chromaticity was greatly improved from L∗ ​= ​29.36, a∗ ​= ​30.45, and b∗ ​= ​24.38 (GS method) to L∗ ​= ​33.43, a∗ ​= ​38.32, and b∗ ​= ​32.34 (LCS method), which indicates that the pigments prepared by LCS method have smaller particle size and brighter red color.

Plasma-assisted combustion synthesis of p-type transparent Cu incorporated NiO thin films—Correlation between deposition chemistry and charge transport characteristics

Optically transparent and conducting Cu-incorporated NiO thin films are deposited by low-temperature plasma-assisted solution combustion synthesis. The hole conductivity, crystallographic nature, and the film morphology in this semiconductor highly depend upon the amount of Cu incorporation in the material, which is found to have a strong influence on the defect density in these films, ultimately leading to a larger variation in their optoelectronic properties. The change in conductivity with Cu incorporation follows the generalized effective medium theory model with a fitted percolation threshold near zero. Under optimal composition of the Cu to Ni ratio in the as-deposited thin film, the p-type electrical resistivity of 0.85 Ω cm is obtained with a hole concentration of 3.9 × 1018 cm−3 and hole mobility of 1.9 cm2 V−1 s−1, with an average visible transmittance of 76%. Hole transport over a wide range of temperatures and Cu incorporation can be successfully modeled by Mott variable range hopping.

Green Synthesis of Ba1−Sr TiO3 ceramic nanopowders by sol-gel combustion method using lemon juice as a fuel: Tailoring of Microstructure, ferroelectric, dielectric and electrical properties

Abstract This article represents a simple, economic and low-temperature green combustion synthesis of Ba1−xSrxTiO3 (BST) ceramic nanopowders for composition x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 with lemon juice as a firing agent. The fabricated nanopowders were characterized by TGA/DSC, XRD, FTIR, FESEM, TEM etc. analytical techniques. XRD analysis reveals the formation of single-phasic tetragonal perovskite structure with no impurity phases for x = 0.0 to 0.2 samples. However, cubic phase was appeared for x = 0.4 to 1.0 samples. FTIR spectroscopic study evidenced the formation of perovskite structure by demonstrating a noticeable band in between 400 and 750 cm−1. The Scherrer and Williamson-Hall (W–H) analysis was utilized to evaluate the crystallite size. TEM study showed that, spherical shaped and uniform nanocrystalline powders (23–28 nm) were fruitfully synthesized. The saturation electric polarization (Ps), remanence polarization (Pr) and coercive field (Ec) decreases with increase in Sr2+ content expected to be dependent on the creation of oxygen vacancies and occurrence of cubic polymorphs by doping of Sr2+ ions. The ideal ferroelectric characteristics were obtained Ps = 5.6661 μC/cm2 and Ec = 2.1242 kV for pristine BaTiO3 sample. Dielectric constant (e’) was obtained at room temperature as a function of frequency, which shows exponential decay with the increase of frequency. The Maxwell-Wagner polarization and dipole polarization were existing in the Sr2+-substituted BaTiO3 nanopowders and were responsible for the obtained dielectric properties. The variation of DC-electrical resistivity (log ρ) versus temperature (300 K–833 K) was observed to be decreased with increasing temperature and Sr2+ substitution; demonstrating that an electrical energy transfer was a thermally stimulated procedure. The Sr2+-substitution has brought an overall enhancement in dielectric and electrical properties. However, the ferroelectric characteristics are weakened, which is primarily attributed to a considerable variation in the micro-structure of the solid.

Boosting the coercivity of SrFe12O19 nanocrystalline powders obtained using the citrate combustion synthesis method

Strontium hexaferrite nanocrystalline powders were synthesized using a citrate combustion method and subsequently subjected to post-synthesis processing with the aim of tuning the micro-nanostructure to improve the magnetic properties. Firstly, the synthesis thermal treatments were optimized in order to minimize the formation of secondary phases, mainly hematite. Secondly, the as-synthesized powders were conditioned by a two-step process: ball milling in wet medium (ethanol) and high-speed mixing. The final processed powders exhibited a saturation magnetization of 74 emu g−1 and a coercivity of 6450 Oe. Following a low-temperature combustion synthesis, the coercivity is one of the largest values reported for strontium ferrites. The combination of the two-step conditioning procedure results in a useful methodology to obtain SrFe12O19 nanocrystalline powders with competitive properties. The morphological, structural and magnetic properties of the processed material make it a promising candidate for hard-soft ferrite-based composite magnets, where large coercivity values are highly desirable.

The effect of various fuels on the yield, structural and optical properties zinc zirconate nanocomposite

Various types of fuels were used in a low-temperature solution combustion synthesis of zinc zirconate nanocomposite at a pH of 7. In the synthesis, the fuels used were citric acid, glycine, urea, hydrazine hydrate, and ammonium nitrate while zirconium butoxide and zinc nitrate were the precursor sources of Zr4+ and Zn2+ ions, respectively. The samples were calcined for 2 h at a temperature of 600 °C. The study of the structural properties showed varied morphologies ranging from highly agglomerated surfaces, crystalline aggregates as well as nanorods. There was a gradual growth of zinc zirconate perovskite within phases of zirconia and zinc oxide. It was observed that there were prominent photoluminescence emissions spread from violet-blue into the yellow-white regions with peaks varying from about 400 to 490 nm. The energy bandgap of the nanocomposites was between 2.93 and 3.22 eV depending on the fuel used in the preparation of the sample.

Blue light excited novel Eu doped CaGd2ZnO5 nanophosphors: Structural and photoluminescent properties

Herein, we report undoped and Eu doped CaGd2ZnO5 (CGZ) phosphors synthesized via low-temperature combustion synthesis route using urea as a fuel. The as-synthesized phosphors are characterized via X-ray diffraction, field-emission scanning electron microscopy, UV/visible spectroscopy, and photoluminescent techniques. The excitation spectra of the synthesized phosphors consist of intense peak at 465 nm lying in the blue region of the visible spectrum. The phosphors emit intense red emission spectra at 612 nm corresponding to the 5D0 → 7F2 transition under blue excitation. This feature of synthesized phosphors makes them pristine candidates for red emission under blue excitation over the other phosphors which are excited under UV or near-UV excitation.

Spherical layered Li-rich cathode material: Unraveling the role of oxygen vacancies on improving lithium ion conductivity

The commercialization of layered lithium-rich manganese oxide material (LLMO) suffers from low conductivity, poor cycling performance, and complicated synthetic techniques. Herein, we develop a low-cost, short-time, and simple low-temperature combustion synthesis (LCS) method for massive production of spherical LLMO material with high oxygen vacancy concentration. In our LCS method, the microstructure and oxygen vacancy concentration of the products are controllable by regulating the dosage of fuel (i.e., urea). Positron annihilation and electron paramagnetic resonance both accurately characterize oxygen vacancy in materials with different urea dosages. When the dosage of urea is 1.5 times of stoichiometric ratio, both the free electron density and oxygen vacancy concentration of the obtained U1.5@LLMO are the highest, which are favorable for rapid transfer of electrons and ions. At rate of 1 C, the average discharge capacity of U1.5@LLMO is 185 mAh g−1 with a high capacity retention of 94.33% after 100 cycles. The corresponding lithium ion diffusion is 1.346*10−12 cm2 S−1, much higher than those of other samples. DFT calculation demonstrated that the electrochemical activity of Li+ increased significantly with the increase of oxygen vacancy concentration. This powerful LCS method for the production of LLMO with excellent electrochemical properties shows great potentials for large-scale applications.

Low temperature combustion synthesis and photoluminescence mechanism of ZnO/ZnAl2O4 composite phosphors

ZnO, ZnAl2O4 and ZnO/ZnAl2O4 composite phosphors were prepared by one - or two-step low temperature combustion synthesis method. The ZnO, ZnAl2O4 and ZnO/ZnAl2O4 composite phosphors were obtained by auto-ignited combustion of a carbamide–nitrate precursor gel which is produced by a simple thermally induced redox reaction. The crystalline phase attributes, functional groups, surface morphology, optical and photoluminescence properties of the ZnO, ZnAl2O4 and ZnO/ZnAl2O4 composite phosphors were characterized by X-ray diffraction analysis, fourier transform infrared spectroscopy, scanning electron microscopy, UV–vis spectrophotometer and fluorescence spectrophotometer. The results showed that ZnO/ZnAl2O4 composite phosphors with the type II energy band arrangement were synthesized by two-step low temperature combustion synthesis method. The introduction of zinc oxide into zinc aluminate system improved the crystallinity of zinc oxide and enhanced the optical and photoluminescent properties of the single phase of materials. Based on the energy band theory, the photoluminescence mechanism of ZnO/ZnAl2O4 composite phosphors was proposed.