Assisted Combustion Synthesis Research Articles

Natural honey (Mellifera) assisted combustion synthesis of ZnO, Ag-ZnO and Fe-ZnO nanoparticles for ethanol gas sensor applications

Biogenic combustion with Mellifera (Honey) capping produced ZnO, Ag-doped ZnO, and Fe-doped ZnO nanoparticles. The phase and crystal structure of metal oxide nanoparticles (MONPs) have been recorded through XRD spectrum. It confirms that the prepared metal oxides are within the nanoscale range. The average crystallite size of Fe-doped ZnO is 8.8 nm, smaller than ZnO and Ag-doped nanoparticles. The vibrational spectra of ZnO, Ag-doped ZnO, and Fe-doped ZnO nanoparticles confirm functional group stretching vibrational modes. The exterior surface morphology of all metal oxide nanoparticles was captured by FESEM. Metal oxide nanoparticle compositional analysis shows elemental presence, atomic, and weight %. The optical properties of metal oxide nanoparticles have been examined using UV–vis spectroscopy. The band gap energy of ZnO nanoparticles reduced from 2.68 eV to 1.74 eV under Fe doing and increased to 2.9 eV under Ag doing. Metal oxide thermal stability is also being investigated to determine how it affects ZnO nanoparticles. Fe-doped ZnO nanoparticles have greater sensor properties than other metal oxides due to their tiny size, band gap, and stability. Gas sensor behaviour of three metal oxide nanoparticles was examined in various accepts. It proves Fe-doped ZnO is a promising gas sensor material.

Microwave-assisted combustion synthesis and characterization studies of novel dysprosium doped yttrium calcium borate (Dy3+: Y2CaB10O19) phosphor materials for efficient white light applications

Micro-wave assisted combustion synthesis technique was adopted to synthesize the dysprosium-doped yttrium calcium borate xDy3+: Y(2-x) CaB10O19 (Dy:YCB) polycrystalline phosphor materials with varying concentrations (x = 1, 3, 5, 7 and 9 mol %) for the first time. The formation of phase, crystal structure was analyzed by x-ray diffraction study and was affirmed to be formed pertaining to the monoclinic crystal structure (a = 11.475 Å, b = 6.345 Å, c = 9.223 Å and α = γ = 90°, β = 91.83°) with C2 space group. The absorption capability of the prepared samples was investigated by UV-DRS spectroscopy and the optical band gap was found to be 5.28 eV. FTIR study validated the presence of functional groups and their molecular vibrations. The excitation wavelength of the synthesized samples was found to be 350 nm from photoluminescence excitation (PLE) spectra. The PL emission spectra were recorded to authenticate the emission wavelengths and found to possess two emission peaks at 480 nm (blue) and 577 nm (yellow) contributed by the Dy3+ ions. The optimized dopant concentration of dysprosium ion was fixed at x = 0.07 to avoid the concentration quenching effect. The chromaticity co-ordinate of optimized sample was determined to be x = 0.3188, y = 0.3233 which are closer to ideal white light co-ordinate. The color temperature was determined to be 6209 K, which occurs in the cool white light region. Luminous efficacy of radiation (LER) was determined to be 269.31 l m/Wopt for the optimal phosphor. The luminous efficiency for the optimal phosphor was determined to be 40%. Color rendering index (CRI) of the optimal sample was evaluated to be 77. Internal quantum yield (IQE) of the optimal sample was determined to be 50.58 %. The phosphor materials have excellent thermal stability as validated from the temperature dependent PL measurements.

Tin and lanthanum modified Ni/CeO2 catalyst systems for low temperature steam reforming of ethanol

This work examines the Ni–Sn/Ce–La–O catalyst systems for low-temperature stream reforming of ethanol. Catalysts of 5 and 20 wt% metal loading, and different Ce:La ratios are prepared by ultra-sonication assisted solution combustion synthesis method. Catalysts at total metal loading 5 wt% with 33 and 67 at. % La and optimum Sn (Ni:Sn = 14:1) demonstrate better efficiency compared to the Ni/CeO2 catalysts. At 20 wt% metal loading and Ni:Sn = 1:1 atomic ratio, catalytic activity degrades. The best activity and stability are revealed for the N14S1(5)/CL21 catalyst with 5 wt.% total metal loading, Ni:Sn = 14:1, and Ce:La = 2:1 mol ratio. Physico-chemical characterizations (XRD, H2 -TPR, NH3-TPD, Raman, FESEM, TEM, XPS, N2 adsorption-desorption, DTA/TGA, etc.) are performed to understand the role of the metal loading, Sn, and La in the catalytic activity and coke deposition behavior.

Neutron capture of UO2 targets prepared by spin-coating assisted combustion synthesis

Two uranium dioxide (UO2) targets of (414 ± 23) nm and (1092 ± 93) nm thicknesses were prepared on 6061 aluminum alloy and puratronic grade aluminum backing materials. The targets were deposited with a novel method combining spin coating and solution combustion synthesis (SCS). The target layers consisted of small (3–7 nm) UO2 grains and uniformly distributed ultra-small (1–3 nm) pores. The prepared targets were tested at the Los Alamos National Laboratory’s LANSCE facility for neutron irradiation damage and suitability for neutron capture experiments. The samples showed no signs of target material loss after the irradiation. However, irradiation caused a significant increase in the grain size (4–10 nm), as well as upward mass diffusion and coalescence of the pores due to the thermal spikes. The magnesium in the aluminum 6061 alloy backing also diffused into the UO2 layer during neutron irradiation. The structural changes in the target after the irradiation do not affect the data from neutron capture. The new method can be used more broadly to prepare other actinide targets for nuclear physics experiments.

Structural and dielectric properties of ultra-fast microwave-processed La0.3Ca0.7Fe0.7Cr0.3O3−δ ceramics

Perovskite La0.3Ca0.7Fe0.7Cr0.3O3-δ (LCFCr) is a mixed ionic and electronic conductor (MIEC) that can be employed as an electrode material in reversible solid oxide fuel cells (RSOFCs). In this work, an ultra-fast (15 ​min) one-step microwave (MW)-assisted combustion synthesis route has been developed to obtain phase pure and highly crystalline LCFCr powder. The synthesized powders exhibited a sponge-like microstructure with increased electrochemical reaction sites. Neutron thermodiffraction analysis revealed a structural transition above 500 ​°C from the room temperature (RT) orthorhombic Pnma to a rhombohedral R3c perovskite phase. The oxygen vacancy concentration was found to increase from δ ​= ​0.272(7) at RT to δ ​= ​0.333(5) at 900 ​°C. Furthermore, a 3-dimensional G-type antiferromagnetic structure was detected at RT. MW-sintering of pressed green ceramic pellets was carried out at 950 ​°C for 1 ​h, using a MW-transparent quartz fiber crucible or alternatively a SiC crucible acting as a MW-absorber. Impedance spectroscopy data on sintered ceramic pellets revealed electronic inhomogeneity as demonstrated by the occurrence of three dielectric relaxation processes associated with two grain boundary (GB)-like contributions and one bulk. The dielectric inhomogeneity encountered may be restricted to the extrinsic GB areas, which may be rather thin. More homogeneous dielectric properties of the GBs were found in the pellet that was sintered in the SiC crucible.

Facile and template-free synthesis of nano-macroporous LaCoO3 perovskite oxide for efficient diesel soot oxidation

The basic LaCoO3 perovskite oxides were prepared by the series of methods (reverse co-precipitation, citric acid aided sol–gel, glycine assisted solution combustion), underwent physicochemical characterization (XRD, FTIR, BET, XPS and SEM), followed by their soot oxidation activity tests in both “loose” and “tight” conditions of soot-catalyst contact. The activity tests revealed that the LaCoO3 catalyst formed using glycine assisted combustion synthesis gives the best performance with the T10, T50, and T90 at 361 °C, 404 °C and 445 °C, respectively, in loose contact conditions and T10, T50, and T90 at 306 °C, 330 °C and 355 °C, respectively, in tight contact conditions. Its outstanding performance can be attributed to its unique morphology consisting of scaffolds having an extensively interconnected macroporous network with macropores having nanoporous struts as walls as evidenced by SEM results. Such morphology makes the active sites of inner pores accessible to the gaseous (air) as well solid reactant (soot particles), thereby benefitting soot oxidation reaction. Supplementary InformationThe online version contains supplementary material available at 10.1007/s11144-022-02219-5.

Influence of synthesis conditions on structural and spectroscopic properties of the K2SrP2O7 pyrophosphate doped with the Eu3+ and Eu2+ ions

This study is focused on the synthesis condition influence related to structural and spectroscopic properties of the potassium strontium pyrophosphate (K2SrP2O7) co-doped with Eu3+ and Eu2+ ions. The experimental parameters of the urea assisted combustion synthesis were optimized by temperature and time of calcination as well as reduction atmosphere composition. The obtained materials were structurally characterized using the X-Ray Powder Diffraction (XRPD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Spectroscopic properties were determined by emission spectra, excitation spectra, luminescence kinetics and luminescence temperature quenching measurements. It was found that increasing concentration of Eu3+ ions caused an increase of spectroscopic factors, which correspond to the relative integrated luminescence intensities of 5D0–7FJ transitions as well as structural defects. Moreover, the successful Eu2+ ion incorporation was proven by optical spectroscopic measurements, which showed the allowed f-d transitions.

CoOx ceramics synthesized by a facile and rapid combustion method and its application for thermochemical energy storage

Cobalt-based ceramics is one of the most promising candidates for thermochemical energy storage. In this paper, a novel cigarette butts assisted combustion synthesis method was proposed to synthesize nano-CoOx ceramics used for thermochemical energy storage. For this method, cigarette butts were selected as solid fuels. The cigarette butts were impregnated in cobalt nitrate solution, and the cobalt nitrate solution was absorbed, filled and dispersed uniformly in the cigarette butts. The wet cigarette butts were directly burned, and two combustion modes (smoldering and flaming) were considered. After the wet impregnated cigarette butts burned out, nano-CoOx was obtained. The commercial and sol-gel method prepared CoOx was also tested for comparison. Based on the characterization results, the CoOx obtained from the combustion synthesis method was a mixture of Co3O4 and CoO. In addition, CoOx synthesized in the smoldering combustion process (S250) had the highest BET specific surface area and better performance on thermochemical energy storage. The conversion rate was kept above 97% and the oxidation rate could maintain at a stable and higher value (∼175 μmol/min/g) after 30 cycles. For S250, the onset temperature gap between heat charging and discharging was the smallest (15.9 °C), suggesting that S250 could charge and discharge quickly and kept a complete reversibility in multiple cycles. The heat loss of S250 was the smallest and its heat grade was the highest. As a whole, direct combustion of the wet impregnated cigarette butts could be a feasible and rapid method to synthesize nano-CoOx ceramics, which exhibited superior performance on thermochemical energy storage.

Fabrication of FeSi/α-FeSi2–based composites by metallothermically assisted combustion synthesis

Fabrication of FeSi/α-FeSi2–based composites by metallothermically assisted combustion synthesis

Investigation of the thermoluminescence properties Ti4+ doped MgO synthesized solid-state assisted solution combustion synthesis method

In this study, undoped MgO and titanium (Ti4+) doped MgO ceramics were synthesized using the solid state-assisted solution combustion synthesis method. The structural characteristics were investigated using X-ray diffraction (XRD) and scanning electron microscope (SEM). TL curves of the MgO:Ti4+(0.1%wt) ceramic consist of three TL peaks located at 70, 250 and 290 oC with a heating rate of 2 oC/s after 1 Gy beta dose. Radioluminescence (RL) characteristic of the MgO:Ti4+(0.1%wt) ceramic was studied with excitations between 200 - 1000 nm. It was found to be the four emission bands the maximums located at 327 nm (~3.79 eV), 694 nm (~1.78 eV), 715 (~1.73 eV), and 745 (~1.66 eV). Some dosimetric characteristics such as TL curve, reusability, dose-response, of the ceramic were investigated using the thermoluminescence (TL) technique using beta radiation of 90Sr/90Y. Dose-response characteristics showed the integrated TL signals between 170-350 oC exhibited a linear up to 20 Gy. The experimental results showed that if it is developed of the MgO:Ti4+(0.1%wt) ceramic can be considered as a dosimetric material with suitable properties in personal and medical applications.

Natural fuels (Honey and Cow urine) assisted combustion synthesis of zinc oxide nanoparticles for antimicrobial activities

A novel green synthesis of the combustion pathway was adopted for the preparation of ZnO nanoparticles using Honey and Cow urine. The effects of honey and cow urine on crystalline size, structure, morphology, band gap and thermal properties of ZnO nanoparticles have been analyzed. The polycrystalline hexagonal wurtzite structure of ZnO nanoparticles is confirmed by XRD spectra. The mean crystalline sizes of the ZnO nanoparticles were 23 nm and 29 nm respectively, for the honey and cow urine phase. The external morphology and grain size of the products have been visualized via FE-SEM and TEM. The average sizes of the grains of the ZnO nanoparticles were perfectly associated with the crystalline size measured from the XRD. Spherical and hexagonal shaped nanostructures were reported using FE-SEM and TEM micrographs. The optical absorption spectra of ZnO nanoparticles have been analyzed using UV–Vis spectrometry. In the FT-IR spectra, around 400 cm−1 to 600 cm−1 range have been allotted to the Zn–O vibration. The thermal properties of ZnO nanoparticles have been analyzed using TGA. Changes in weight loss for different ZnO nanoparticles using honey and cow urine have been documented. Gram Positive (B.Subtilis) and Gram-Negative (E.Coli)Bacteria were tested using plate counting technique to study the antimicrobial activity of ZnO nanoparticles prepared by cow's urine and honey. Compared with cow urine-prepared ZnO nanoparticles, honey-assisted ZnO nanoparticles demonstrate strong antibacterial activity.

Mesoporous manganese cobaltate: Colloid assisted ethylene glycol combustion synthesis and application in efficient water oxidation

The development of oxygen evolution reaction (OER) electrocatalysts with attractive price, robust activity, and superior durability are desirable for efficient water splitting. In the present work, a facile and fast colloid assisted ethylene glycol (EG) combustion synthesis strategy was developed to prepare mesoporous manganese cobaltate (MnCo2O4) with a large specific surface area (SSA). The as-prepared MnCo2O4 delivered a high SSA of 124.4 m2 g−1 with hierarchical mesopores in the range of 3–30 nm. It offered short diffusion paths and rich active sites, which can promote the OER catalytic activity. When applied as the electrocatalyst for OER, the mesoporous MnCo2O4 demonstrated an ultra-low overpotential of 0.24 V at 10 mA cm−2, and a moderate Tafel slope with robust durability. This work not only puts forward a novel synthetic route towards mesoporous MnCo2O4 with high SSA but also reveals its tremendous prospects in the field of electrocatalytic water oxidation.

Nb2O5 nanoparticles obtained by microwave assisted combustion synthesis under different conditions

The microwave assisted combustion synthesis (MACS) as a new, quick and low cost synthesis method was used for preparation of niobium pentoxide (Nb2O5) powders. The present paper investigated the effect of reactant concentrations (ammonium niobium oxalate, urea and ammonium nitrate) on the characteristics of Nb2O5 nanoparticles. Three samples were synthesized with stoichiometric ratio between the fuel and oxidant (C1), excess of oxidant (C2) and excess of fuel (C3). In all samples, Nb2O5 crystalline nanoparticles with irregular morphology were detected. The synthesis of nanoparticles with smaller diameter in the C2 and C3 samples was confirmed by greater values of band gap energy measured through UV-Visible diffuse reflectance spectroscopy (indicating quantum confinement) and by the Rietveld refinement of X-ray diffraction patterns. The results showed that the amounts of oxidant and fuel can change synthesis temperature, influencing the final characteristics of the particles, such as size and existent phases. In these cases the excess of oxidant and fuel in the C2 and C3 samples, respectively, decreases the average synthesis temperature and decelerates the particle growth and the formation of the monoclinic phase.

Cellulose assisted combustion synthesis of high surface area Ni-MgO catalysts: Mechanistic studies

The objective of this study was to determine the combustion mechanism of cellulose paper impregnated with Mg(NO3)2, Ni(NO3)2, glycine solutions, and their different combinations. It was established that the combustion mechanism changes as a function of the impregnated media composition. In the Mg(NO3)2-cellulose system, Mg2+ ions strongly catalyze cellulose pyrolysis; hence no atmospheric oxygen is needed for the self-sustained combustion reaction. In the Ni(NO3)2-cellulose system, Ni2+ ions catalyze pyrolysis at a lower rate, and atmospheric oxygen assists the combustion wave propagation. In glycine containing systems, glycine blocks the ability of metal cations to catalyze the early cellulose pyrolysis, and the combustion front propagates due to the exothermic reactions between metal nitrates and glycine. The above mechanisms influence the microstructure of the combustion products. Due to the near-complete degradation of cellulose fibers during the Mg2+ catalyzed pyrolytic combustion, the resulting materials had a highly porous, sponge-like microstructure with a BET surface area of up to 152 m2/g. After the reduction in hydrogen, Ni segregates to the surface of NiO-MgO solid solution, and the resulting catalysts exhibited near-equilibrium methane conversion during the dry reforming of methane reaction at 600°C with low carbon formation and no deactivation for 24 h of time on stream.

Enhancing the electrocatalytic properties of LaMnO3 by tuning surface oxygen deficiency through salt assisted combustion synthesis

In this work, we report a detailed investigation on the salt assisted combustion synthesis of LaMnO3 perovskite catalyst for improving the electrochemical properties through agglomeration control and enhanced oxygen defects for fuel cell and battery applications. The main challenge in conventional solution combustion synthesis (SCS) is the nanoparticle agglomeration that masks the active sites in catalysts. Herein, we follow a salt assisted solution combustion synthesis route to synthesize LaMnO3 perovskites (LaMnO3-SA) with a lower level of agglomeration and investigate its application for oxygen electrocatalysis. Through an effective incorporation of salt in the redox combustion mixture, the surface area of the particles doubled along with an improved pore size and pore volume distribution. The surface analysis by x-ray photoelectron spectroscopy indicated the formation of more surface oxygen defects with the introduction of inert salt that helps the absorption of oxygenated species during electrochemical process. Remarkably, LaMnO3-SA showed superior characteristics in terms of limiting current density, onset potential and half wave potential displaying enhanced bifunctionality towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The mass activity of LaMnO3-SA was almost double and kinetic current density was threefold the value at -0.25 V in comparison to the traditional SCS LaMnO3. This work demonstrates that active sites accessible for oxygen electrocatalysis in solution combustion synthesis can be enhanced through the introduction of an inert salt during the synthesis.

Luminescence properties of nitrogen-rich Ca-SiAlON:Eu2+ phosphors prepared by freeze-drying assisted combustion synthesis

Nitrogen-rich Eu2+-doped Ca-α-SiAlON phosphors (Cam/2−xSi12−m−nAlm+nOnN16−n:xEu) were synthesized by a freeze-drying assisted combustion synthesis (CS) route. Fast-synthesized products with high purity and uniform particle morphology were confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The analysis of lattice parameters by comparison with empirical equations showed that the as-prepared phosphors had low oxygen content. A series of samples were prepared according to the stoichiometry of Cam/2−0.08Si12−mAlmN16:0.08Eu for further research. The influences of m value on the luminescence properties were investigated in detail. As m increased, a redshift phenomenon was observed in both the excitation and emission spectra. First-principle electronic structure calculations showed that the 3d energy level of Ca played an important role in the occurrence of the redshift phenomenon.

An active and stable NiOMgO solid solution based catalysts prepared by paper assisted combustion synthesis for the dry reforming of methane

Ni supported on solid solution (NiOMgO) catalysts with different Ni concentration (10, 20 and 30 wt.%) were prepared by a novel paper assisted combustion synthesis (PACS) method, followed by a reduction stage. All as-synthesized materials formed NiOMgO solid solutions, which under optimum PACS conditions exhibited up to about 140 m2/g BET surface area, which is one of the highest reported so far for this type of materials. Solid solutions were not active unless reduced at higher temperatures, causing a fraction of the Ni to segregate to the surface to become the active sites. The activity during the dry reforming of methane was studied as a function of temperature, and time on stream (TOS). The PACS solid solution with 10 wt.% of Ni had the highest surface area and, upon reduction, it was the most active and stable catalyst exhibiting low carbon formation at 600 °C, and no carbon deposition at 700 °C during 24 h TOS. The activity results correlated well with the higher surface area of the starting solid solutions, the smaller Ni crystallite sizes, and the number of Ni2+ and Ni3+ sites on the surface.

Super porous TiO2 photocatalyst: Tailoring the agglomerate porosity into robust structural mesoporosity with enhanced surface area for efficient remediation of azo dye polluted waste water

The low surface area of TiO2 (50 m2g-1 - Degussa P25) due to randomly oriented, agglomerated nanostructures and charge carrier recombination tendency, has till date been its major limitation for photocatalytic remediation of polluted wastewater. This study presents an innovative process to design super porous TiO2 nanostructures with high effective surface area (238 m2g-1), robust, structurally ordered mesoporosity via a simple sol-gel assisted reflux method. Detailed material characterization studies suggest that the higher degree of intermolecular ligation in novel templates such as butanetetracarboxylic or tricarballylic acid modified titanium hydroxide gels resulted in retainment of the porous structure during the urea assisted combustion synthesis. The induction of robust structural porosity is accompanied by a reduction in pore size distribution, an increase in pore volume leading to significantly higher total surface area of the synthesized TiO2. Detailed investigation of dye adsorption kinetics and photocatalytic degradation kinetics, complemented by kinetic modeling analysis confirmed that the super porous TiO2 with robust mesoporous structure outperforms the rest of synthesized TiO2 catalyst (having only agglomerate porosity) in terms of its superior adsorption capacity, faster diffusion kinetics and photocatalytic activity for degradation of Amaranth dye. Thus, the super porous TiO2 shows promising potential for application in sustainable photocatalytic technology for remediation of wastewater contaminated with azo dyes.

Jatropha extract mediated synthesis of ZnFe2O4 nanopowder: Excellent performance as an electrochemical sensor, UV photocatalyst and an antibacterial activity

This research work reports green assisted combustion synthesis of zinc ferrite nanoparticles (ZnFe2O4 NPs) using Jatropha extract and their electrochemical sensor with antibacterial activities were studied. The 98% dye degradation was achieved for photocatalytic decomposition of Malachite Green (MG) dye using prepared ZnFe2O4 NPs under UV irradiation. Electrochemical analysis was conducted in 0.1 M KCl with modified Graphite-ZnFe2O4 electrode showed charge-discharge battery type mechanism and showed excellent performance in electrochemical sensor activity for Mifepristone and Misoprostol. Also antibacterial activity of ZnFe2O4 NPs was discussed against E. coli and Pseudomonas aeruginosa bacteria at different concentrations by agar gel diffusion method.

Microwave assisted combustion synthesis of photolumiescent ZnAl2O4:Eu nano powders

In the present study, ZnAl2O4:Eu nano particles were synthesized via microwave assisted combustion route using aluminium nitrate nonahydrate, and zinc nitrate hexahydrate as starting materials, and ethylene glycol, glycine, glucose and citric acid as fuels. Effect of different parameters such as calcination temperature, fuel type, oxidizer to fuel (O:F) ratio and Eu dopant concentration on the structure, microstructure, photoluminescence and optical properties was studied. Results showed that these parameters can strongly affect structure, microstructure, and consequently photoluminescent properties. As-synthesized samples were amorphous and must be post-heated up to 900 °C to form crystalline phase. Moreover, morphology of nano particles was sponge plate- like with using different fuels. Furthermore, photoluminesce emission at red region was observed by introducing Eu.