Solution Combustion Synthesis Technique Research Articles

Sr0.99Zr(PO4)2:0.01Eu3+ ceramic glass for photoluminescence applications

This paper reports the first-time synthesis of Sr0.99Zr(PO4)2:0.01Eu3+ nanophosphor via solution combustion method using glycine as fuel at a fuel-to-oxidizer ratio of 1:1. The PXRD pattern confirmed the formation of the desired phase, while the Scherrer calculation revealed an average particle size of approximately 60 nm. Scanning electron microscopy (SEM) further corroborated the particle size, estimating it around 75 nm. The material exhibited a characteristic mesoporous structure, a hallmark of the solution combustion synthesis technique. Photoluminescence (PL) spectroscopy revealed two intense emission peaks at 590 nm and 615 nm, attributed to Eu3+ ions, suggesting potential applications in LED technology. CIE coordinates indicated emission close to the white region defined by the NTSC standard

Samarium ion-doped calcium silicate: A promising material for fabrication of light emitting diodes

In this work, calcium silicate nanophosphors (CaSiO3) doped with Sm[Formula: see text] ions were prepared at [Formula: see text]C by a simple solution combustion synthesis technique. The particle size, functional groups and morphology of the prepared phosphors were identified by X-Ray diffraction (XRD), Fourier transform infrared (FTIR), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) techniques. The monoclinic phase of the nanophosphors was confirmed by X-ray diffraction studies. The effective excitation of the nanophosphors near the UV region and their yellow emission were confirmed by photoluminescence studies.

Solution combustion synthesis derived Li4SiO4 for post-combustion carbon capture

ABSTRACT Lithium-based sorbents are considered as promising candidates for post-combustion carbon capture because of their superior stability compared to CaO. In the present study, Li4SiO4 powders were synthesized by Solution Combustion Synthesis (SCS) technique using LiNO3 as lithium source, TEOS as silicon source and citric acid as the fuel. CO2 sorption tests were carried out for the synthesized samples and, powder prepared at 650°C during 4 h, which has 17 µm of particle size, 5.2 m2 g−1 of specific surface area, 85.2% Li4SiO4 phase purity with 97 nm of crystallite size showed a sorption performance as 29.5 wt% CO2 uptake value, in thermobalance test under 92 vol% CO2 (N2 balance) gas concentration at 600°C. The sample had a CO2 uptake value of 21.4 wt% under 20 vol% CO2 concentration which was chosen to simulate industrial off-gas conditions. Also, the same sample showed a good cyclic durability during the sorption/desorption tests. The sample maintained its cyclic CO2 uptake capability range between 21 and 24 wt% for 15 cycles.

(Digital Presentation) Multifunctional Lanthanum Perovskite Electrocatalysts (LaMnxCo1-xO3 (0≤x≤1)) for Alkaline Medium Methanol Oxidation and Oxygen Catalysis

Lanthanum-based synthetic perovskites (LaMnxCo1-xO3 (0≤x≤1)) were synthesized using a solution combustion synthesis technique with variable ratios of Co and Mn to investigates the surface and electrocatalytic property (activity and stability of catalysts) for methanol oxidation reaction (MOR), oxygen reduction reaction (ORR), oxygen evolution reaction (OER) under alkaline medium (KOH). The structural and morphological characterizations of the synthesized catalyst were performed by XRD, FTIR, SEM, TEM and XPS techniques. The structural and chemical properties systematically changed by varying the Mn to Co ratio in the perovskite structure. To observe the completion of combustion and temperature characteristics during the synthesis process, which are known to impact structural qualities, the time temperature profile during the combustion process was monitored. SEM/EDX and XPS analysis confirmed the formation of targeted ratio of Mn and Co on the catalyst. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) results revealed that all perovskite samples with different Co:Mn ratios were active for ORR, OER and MOR. The LaMnxCo1-xO3 perovskite with x=0.4 showed the highest current density compared to other samples towards all the investigated electrocatalytic reactions (MOR, ORR and OER) under alkaline reaction conditions.

Highly Active Lanthanum Perovskite Electrocatalysts (LaMnxCo1-xO3 (0 ≤ x ≤ 1)) by Tuning the Mn:Co Ratio for ORR and MOR in Alkaline Medium

AbstractLanthanum-based perovskites (LaMnxCo1-xO3 (0 ≤ x ≤ 1)) were synthesized using a solution combustion synthesis technique with variable ratios of Co and Mn to investigate the surface property and electrocatalytic characteristics (stability and activity of catalyst) for methanol oxidation reaction (MOR), oxygen reduction reaction (ORR), and oxygen evolution reaction (OER) under alkaline medium (KOH). The structural, chemical, and morphological characterizations of the synthesized catalyst were performed by XRD, FTIR, SEM, TEM, and XPS techniques as a function of the Mn:Co elemental ratio. The time–temperature profile during the combustion process was also monitored to study the completion of the combustion reaction and to understand its impact on the structure of the perovskites. SEM/EDX and XPS analysis confirmed the formation of the targeted ratio of Mn and Co on the catalyst. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) results revealed that all perovskite samples with different Co:Mn ratios were active for ORR, OER, and MOR. The LaMnxCo1-xO3 perovskite with x = 0.4 showed the highest current density compared to the other samples toward all the electrocatalytic reactions under alkaline reaction conditions. Graphical Abstract

Effect of Bi2O3 contents on magnetic and electromagnetic properties of LiZnMn ferrite ceramics

Soft LiZnMn ferrites with low coercive force values and small grain sizes were developed by the solution combustion synthesis and low temperature sintering technique for microwave applications at a high frequencies. Bismuth oxide was used as an additive to lower the sintering temperature. The examination covered the influence of Bi2O3 on the crystal structure, microstructure, primary magnetic and dielectric characteristics of lithium-zinc-manganese ferrites. The most promising sample designed for using in microwave devices was produced by sintering at 1075 ℃ temperature for 8 h with added 1.5 wt% Bi2O3. These production conditions have yielded 2.98 µm average grain size in a ceramic product, the density is 4.84 cu cm/g, and the coercive force, residual induction, and saturation induction are 58 A/m, 2078.4 G, and 3439.1 G, respectively. In addition, this sample demonstrates a high initial magnetic permeability (μi = 168), Curie temperature (Tc = 437.5 ℃), high values of the dielectric loss tangent (tan δɛ = 6.32⸱10−3), ferromagnetic resonance line width (ΔH = 280 Oe) and the resonance line of spin waves (ΔHk = 1.87 Oe). Further increase in the bismuth oxide content allows observing a change in the ceramics microstructure, accompanied by a deterioration in the magnetic and electromagnetic characteristics. Here, the discussion covers the mechanism of change in the functional properties of lithium-zinc-manganese ferrites produced in the conditions of solution combustion with added bismuth oxide. Thus, synthesizing of initial pre-ceramic powder by glycine-nitrate combustion and subsequent low-temperature sintering with added bismuth oxide is a novel efficient technique of producing advanced soft high-frequency LiZnMn ferrites.

Combustion synthesis of copper ceria solid solution for CO2 conversion to CO via reverse water gas shift reaction

The reverse water–gas shift chemical (RWGS) reaction is a promising technique of converting CO2 to CO at low operating temperatures, with high CO selectivity and negligible side products. In this study, we investigate the synthesis of Cu/CeO2 catalyst using Solution Combustion Synthesis (SCS) technique and its performance for the RWGS reaction using a tubular packed bed reactor. Results indicate that the catalytic activity and stability of CeO2 at low and moderate temperatures can be effectively improved by the addition of a small quantity of copper (1 wt%). The conversion of CO2 improves with an increase in temperature, with a maximum value of 70% at 600 °C, showing a steady time on stream (TOS) performance for 1200 min with negligible carbon deposition of <0.05 wt%. The high catalyst activity is due to the synergistic interaction between the active Cu0 species and Ce3+-oxygen vacancy. The Cu/CeO2 catalyst was also found to have 100% selectivity for CO, and no CH4 was detected in the outlet stream. Moreover, the morphological characteristics of the support and catalysts (fresh and post-reaction samples), as well as the impact of reaction on the catalysts surface were investigated using various methods such as x-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy with energy dispersive x-ray spectra (SEM/EDX). The results demonstrate that Cu/CeO2 offers a good potential for being a robust RWGS catalyst with exclusive selectivity for CO without the undesired methanation side-reaction.

Effect of [formula omitted] additive on the crystallization of zircon via SCS method: Synthesis, characterization and reaction mechanism

A demonstration was represented to exhibit the crystallization of ZrSiO4 from ZrO2-SiO2 binary composite using additive of NH4VO3 via solution combustion synthesis (SCS) technique. The XRD and Rietveld results revealed favorable crystallization of zircon with crystallite size about 50 nm. FE-SEM images showed the particles with uniform hexagonal-close-packed morphology. Furthermore, the effect of vanadium on self-sustained reaction was studied by Kissinger-Akahira-Sunose method and DSC data. The results indicated that the presence of vanadium decreased flame temperature and activation energy. The activation energies in combustion reaction for ZrO2-SiO2 and ZrSiO4 were found to be 189.401 kJ/mol and 66.032 kJ/mol, respectively.

A review of solution combustion synthesis: an analysis of parameters controlling powder characteristics

ABSTRACT The solution combustion synthesis technique is a versatile method for the production of powders used in a variety of applications. It has been used to produce hundreds of compounds, thus demonstrating its versatility, especially for the preparation of oxides, and is now a workhorse technique in materials science. Its success resides in the ease of implementation, high-throughput, the versatility of chemistries, and capacity for the production of high-surface area powders. The main limitations of the technique include problems with powder agglomeration, possible lack of control of powder morphologies, and the presence of leftover organic impurities from incomplete combustion. In this contribution, we review the influence of a variety of factors of relevance for the technique, including the type of fuel, fuel-to-oxidizer ratio, and combustion temperature, as well as the presence of additives and other special considerations, with a particular focus on the crystallite size and particle size of the resulting powders.

Optically stimulated luminescence of MgO:Na,Li phosphor prepared using solution combustion method

Abstract The purpose of this study is to synthesize magnesium oxide polycrystals doped with sodium and lithium (MgO:Na,Li) using Solution Combustion Synthesis (SCS) technique for developing a storage material with required Optically Stimulated Luminescence (OSL) properties. In this work, we investigated the dosimetric and luminescence characteristics of the synthesized MgO:Na,Li ceramic in pellet form. The phase identification and morphology of the samples were performed using x-ray diffraction (XRD) and scanning electron microscope (SEM) analysis. The radioluminescence (RL) emission of the obtained MgO:Na,Li pellet samples showed two different emissions bands that are dominant at ∼730 nm, and with a weak and broad emission between 300 and 590 nm. The samples characterized by a Thermoluminescence (TL) glow curve having dominant TL peaks at around 80, 155 and 315 °C at a heating rate of 5 °C/s. We carried out a step-annealing procedure to investigate the depth of the trapping centers associated with the OSL signal. The thermally affected OSL traps seems to be originated mostly from practically a single deconvoluted TL peak between 170 and 250 °C with intensity comparable to Al2O3:C when Hoya U-340 filter was used. The stability of the OSL signal was tested for shorth-term and long-term fading in dark. We determined that the total OSL area decayed around 15% after 5 weeks. We evaluated the kinetic parameters of the MgO:Na,Li using the computerized glow curve deconvolution (CGCD), Tm-Tstop method and extended initial rise method (IRM) for the TL traps, and isothermal annealing method for the OSL traps. We presented MgO:Na5%,Li5% as a workable OSL material sensitive to ionizing irradiation with suitable dosimetric properties.

Nickel–Ceramic Electrodes with High Nickel Content for Solid Electrolyte Electrochemical Devices

Composite powders (66 wt % NiO + 34 wt % Zr0.84Y0.16O1.92 were obtained according to the solution combustion synthesis technique by crystallization of nickel oxide particles on the surface of Zr0.84Y0.16O1.92particles. The samples pressed from powders after sintering and reduction in moist hydrogen had high electrical conductivity, more than 16 × 103 S cm–1 at room temperature. Impedance spectroscopic studies have shown that in a humid atmosphere of Ni – Zr0.84Y0.16O1.92, electrodes formed on the surface of a dense Zr0.84Y0.16O1.92 electrolyte have low electrochemical activity. The impregnation of the electrodes with a solution of cerium nitrate followed by thermolysis made it possible to increase the electrochemical activity of the electrode by two to three orders of magnitude. An analysis of the electrochemical impedance spectra through the calculation of the distribution function of the relaxation time showed that the rate of hydrogen oxidation at the electrodes is limited by surface–adsorption processes. After impregnation, the gas diffusion resistance significantly limits the electrode reaction rate.

Investigations of enhanced luminescence properties of Sm3+ doped LaAlO3 nanophosphors for field emission displays

LaAlO3: Sm3+ (1–9 mol%) nanophosphors were synthesized using solution combustion synthesis technique. The structural analysis is carried out using different analytical techniques such as Powder X-Ray Diffraction (PXRD), Fourier Transform InfraRed spectra (FTIR), Scanning Electron Microscopy (SEM), transmission electron microscopy (TEM). The bandgap is found to be in the range 4.9–5.3 eV. Photoluminescence and cathodoluminescence spectra are studied for the investigation of the optical property of the synthesized nanoparticles. The pure rhombohedral phase is obtained after calcination at 900 °C. The agglomerated porous structure is revealed from SEM images of the nanoparticles. Under the 406 nm excitation wavelength and 10 keV accelerating voltage the PL and CL spectra are observed with characteristic emission peaks of Sm3+ ions from 4G5/2 to 6HJ=5/2,7/2,9/2 transitions with yellowish-orange color. The CIE coordinates confirm the emission of yellowish-orange luminescence from LaAlO3: Sm3+ phosphors. The results obtained reveal that these materials are potential candidates for the fabrication of field emission displays, photoluminescence liquid crystal displays, and other optical devices.

Enhanced photoluminescence intensity of blue-light-emitting BaMgAl10O17:Eu2+ phosphor with Dy3+ co-doping

Eu2+-doped and Eu2+, Dy3+-co-doped BaMgAl10O17 phosphors were prepared by solution combustion synthesis technique. The main aim of this work is to study the effect of Eu2+, Dy3+ co-doping on the morphological and optical properties of BaMgAl10O17. The co-doping of Dy3+ ions could not produce any change in the morphology, but the photoluminescence emission intensity of BaMgAl10O17:Eu2+, Dy3+ increased nearly 36% with the addition of Dy3+ ions compared to BaMgAl10O17:Eu2+ phosphor. The BaMgAl10O17:Eu2+, Dy3+ phosphor emitted good-quality blue light at wavelength 450 nm. The blue emission was originated from 4f65d1 → 4f7 transition of Eu2+ ions, whereas Dy3+ ions were vital in creating traps. Thermoluminescence study was performed to calculate the activation energy of the traps formed and the order of kinetics. The inclusion of Dy3+ ions not only enhanced the photoluminescence intensity but also improved the thermal stability of BaMgAl10O17:Eu2+ phosphor. The results of the present work indicate that photoluminescence properties and thermal stability of BaMgAl10O17:Eu2+ phosphor can be enhanced by Dy3+ co-doping.

Cobalt and Nickel Phosphates as Multifunctional Air-Cathodes for Rechargeable Hybrid Sodium-Air Battery Applications.

Noble-metal-free bifunctional electrocatalysts are indispensable to realize low-cost and energy-efficient rechargeable metal-air batteries. In addition, power density, energy density, and cycle life of these metal-air batteries can be improved further by utilizing the fast faradaic reactions of metal ions in the catalyst layer together with the oxygen evolution/reduction reactions (OER/ORR) for charge storage. In this work, we propose mixed metal phosphates of nickel and cobalt, NixCo3-x(PO4)2 (x = 0,1, 1.5, 2, and 3), as multifunctional air-cathodes exhibiting bifunctional electrocatalytic activity and reversible metal redox reaction (M3+/2+, M = Ni and Co). Submicron-sized NixCo3-x(PO4)2 particles were synthesized by a solution combustion synthesis technique with urea acting as the fuel. Electrocatalytic activity toward the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) in 0.1 M NaOH was systematically tuned by varying the Ni-to-Co ratio. The synthesized NixCo3-x(PO4)2 with x = 1.5 (NCP11) showed superior bifunctional catalytic activity to other samples. Moreover, the catalyst material delivered a specific capacity of ∼110 mAh g-1 by the redox reactions of its metal sites. The hybrid Na-air battery fabricated using the NCP11 catalyst-loaded air-cathode exhibited low overpotential, stable cycling performance, and round-trip energy efficiency exceeding 78% in a 0.1 M NaOH aqueous electrolyte.

Electrochemical performance of porous CaFe2O4 as a promising anode material for lithium-ion batteries

Abstract The performance of existing lithium-ion batteries (LIBs) is greatly hindered by the low specific capacity of graphite-based anodes (372 mAh g−1). Therefore, development of suitable anode materials that exhibit higher and stable capacity is necessary to improve performance. Transition metal oxides have attracted tremendous attention as next-generation anode materials for LIBs due to their high theoretical capacity. Herein, we report the synthesis of a porous CaFe2O4 by a facile and time efficient solution combustion synthesis technique for use in an anode for LIBs. The as-prepared material exhibited improved electrochemical performance with specific discharge capacities of 441 mAh g−1, 518 mAh g−1, and 516 mAh g−1 for the initial three cycles. It achieved stability with a deliverable specific discharge capacity of 551 mAh g−1 after 150 cycles at a current density of 200 mA g−1. The porous CaFe2O4 exhibits improved cyclic performance and rate capability. These improvements are attributed to the porous nature of active material and, more importantly, the presence of CaO, which effectively alleviates the volume changes by acting as a buffer matrix.

Surface Alloying in Silver-Cobalt through a Second Wave Solution Combustion Synthesis Technique.

Herein, we report the synthesis of silver-cobalt nanopowders using three different modes of solution combustion synthesis, and we present the effects of the synthesis conditions on particle morphology. The synthesized nanoparticles were characterized using X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), UV-Visible spectrophotometer (UV-vis), Transmission electron microscopy (TEM), and X-Ray Photoelectron Spectroscopy (XPS) to understand the structural and elemental properties. When Co is synthesized over Ag in a second wave of combustion, peak shifts observed in XRD and XPS show a change in the cell parameters and prove the existence of a strong electronic interaction between Ag and Co. Better control of mixing and alloying through the second wave combustion synthesis mode (SWCS) was evident. The sequence of combustion affects the structure and composition of the material. SWCS reduces the amount of carbon content, as compared to single-stage combustion, and the combustion of carbon is followed by a rearrangement of atoms.

Exploration of Iron-Based Mixed Polyanion Cathode Materials for Thin Film Sodium-Ion Batteries

Li-ion batteries are promising power sources for portable electronics and electric vehicles due to their high energy density. However, its application in grid storage is limited due to high cost and low abundance of Li resources. Next to Li-ion, Na-ion batteries (NIBs) are getting prominent interest due to its low cost, intercalation properties similar to Li and electrochemical potential of Na/Na+ (-2.71 V vs SHE) [1]. Recent studies based on layered NaMnO2 showed high specific capacity of 140 mA h g-1 by six biphasic transitions. However, the layered materials deliver poor cycling performance due to multiple phase transitions in Na insertion/extraction reactions [2]. On the other hand, Polyanion-type compounds are the most promising electrode materials for NIBs due to their stability, safety, and suitable operating voltages. Recently, Na4M3(PO4)2P2O7 (M=Co, Mn, Ni and Fe) are evaluated as electrode materials for energy storage applications due to its Na-ion intercalating properties, low cost and environmental friendliness [3,4]. In this work, the bulk powder of carbon coated Na4Fe3(PO4)2P2O7 material was prepared by solution combustion synthesis technique using ascorbic acid. The crystal structure was identified to be orthorhombic with Pna21 symmetry from Rietveld refinement. It has a 3D intercalating structure for Na-ion with a theoretical capacity of 129 mAh g-1. The Na-ion cell with the carbon coated nano-Na4Fe3(PO4)2P2O7 cathode delivered a discharge capacity of ~110 mAh g-1 at a 0.1C rate (Fig. 1a). The Na4Fe3(PO4)2P2O7 showed excellent rate capability with good cycling stability 100 cycles. Overall the voltage profile shows two plateau regions with the average voltage of ~3.1 V (Fig. 1b). The electrochemical results motivated us to synthesize the Na4Fe3(PO4)2P2O7 thin films for all-solid-state Na-ion batteries, which can be useful to design thin film micro-batteries. Thin films of Na4Fe3(PO4)2P2O7 electrode was deposited on stainless steel substrates using pulsed laser deposition (PLD) using KrF Laser source. Various deposition parameters were optimized to grow uniform thin films on substrates. From X-ray diffraction it was observed that films were crystallized into orthorhombic structure with Pna21 symmetry. Nano size and thickness of Na4Fe3(PO4)2P2O7 thin film grains were identified by field emission electron microscopy (FE-SEM) and atomic force microscopy (AFM) (Fig. 1d). Here, Na-ion intercalating properties of iron-based mixed-polyanion Na4Fe3(PO4)2P2O7 thin films was investigated. The electrochemical properties of both bulk and thin films of Na4Fe3(PO4)2P2O7 were studied. The thin films with thickness of ~200 nm delivered a maximum capacity and similar voltage profiles to the bulk material (Fig. 1d). The work demonstrates the capability of the mixed polyanionic material as high performance thin film Na-ion battery cathode. The electrochemical performances of the bulk and thin films of Na4Fe3(PO4)2P2O7 will be presented. Finally, an all-solid-state thin film micro-battery will be demonstrated using the full cell configuration having Na4Fe3(PO4)2P2O7 as cathode, NASICON Na3Zr2Si2O12 as solid electrolyte and Na3Ti2(PO4)3 as anode [5]. Figure 1. Electrochemical performances of Na4Fe3(PO4)2P2O7 in sodium half-cell architecture. (a) Galvanostatic charge/discharge curves of Na4Fe3(PO4)2P2O7 at a C/10 current rate. (b) Differential capacity vs. voltage (dQ/dV) plots, (c) Rate capability at different C rates and (d) Galvanostatic charge/discharge curves of Na4Fe3(PO4)2P2O7 thin film (inset) AFM and SEM images of the thin films grown by PLD technique [5]. Acknowledgement Author B.S. gratefully acknowledges the DST (SERB), New Delhi, India (PDF/2015/00217) for providing Fellowship. Figure 1

Template free synthesis route to monophasic BaMgAl10O17:Eu2+ with high luminescence efficiency

Luminescence properties of BaMgAl10O17:Eu2+ phosphors are greatly affected by its pure phase and uniform morphology. Hitherto different synthesis techniques have been adopted to achieve the same but phase purity and good crystallinity still remain desirable for BaMgAl10O17:Eu2+ nanophosphor. To obtain a highly intense blue light emitting BaMgAl10O17:Eu2+ nanophosphor, it was prepared in the absence of templates and additives by a simple solution combustion synthesis technique. The obtained powders were further acid leached and heat treated at 600 °C under argon atmosphere. BaMgAl10O17:Eu2+ samples obtained after this treatment show pure phasic characteristics having radical improvement in crystallinity with transformed morphology from multifaceted to rod-like. This structural modification has led to substantial increase in photoluminescence emission intensity of about 65% in comparison to the samples prepared by conventional solution combustion synthesis route.

Earth‐Abundant Alkali Iron Phosphates (AFePO4) as Efficient Electrocatalysts for the Oxygen Reduction Reaction in Alkaline Solution

AbstractWater‐splitting systems are essential for clean energy production. The oxygen reduction reaction (ORR) is a key reaction involved in water splitting, which requires a catalyst. The current work explores the possible application of sodium and potassium iron phosphates (AFePO4, A=Na and K) as electrocatalysts for ORR activity. These earth‐abundant iron phosphates were synthesized by the solution combustion synthesis (SCS) technique by using ascorbic acid both as fuel and reducing agent for Fe. The crystal structure was analyzed by Rietveld refinement. The formation of carbon coating was identified by thermogravimetric analysis and Raman spectroscopy. Electrocatalytic properties of AFePO4 were investigated in alkali electrolytes for the first time by using linear sweep voltammetry with a rotating disk electrode (RDE). The ORR activities of these alkali iron phosphates are comparable to that of the Pt/C system. The Tafel slope and electron transfer number of the alkali iron phosphates were calculated. The ORR activity of NaFePO4 was found to be better than KFePO4 and FePO4. This work demonstrates alkali iron phosphates as alternate cost‐effective, novel electrocatalysts for productive ORR activity in alkaline solution.

One-Step Solution Combustion Synthesis of Cobalt Nanopowder in Air Atmosphere: The Fuel Effect.

In this paper, we report a new modified solution combustion synthesis technique for one-step production of metallic Co nanoparticles. The main unique feature of our approach is the use of microwave-assisted foam preparation. Also, the effect of different types of fuels (urea, citric acid, glycine, and hexamethylenetetramine) on the combustion process and characteristics of resultant solid products were investigated. It was shown that the combination of microwave-assisted foam and hexamethylenetetramine as a fuel allows us to produce metallic Co nanoparticles with the broad size distribution (∼5-40 nm), high coercivity (370 Oe), and high value of saturation magnetization (137 emu/g) by the one-step solution combustion synthesis under normal air atmosphere without any post reduction.