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Effect of Synthesis Temperature on Structural, Optical, and Magnetic Properties of ZnO Nanoparticles Synthesized by Combustion Method
摘要： ZnO nanoparticles at different temperatures were synthesized by using the combustion method. The effect of synthesis temperature on the properties of the nanoparticles was studied by using XRD, FESEM, EDS, TEM, photoluminescence (PL), Raman, diffuse reflectance spectra (DRS), and VSM characterization techniques. The XRD results reveal that the grown nanoparticles have a hexagonal wurtzite structure without any impurities and agreed with EDS results. FESEM and TEM micrographs show that the ZnO nanoparticles possess a spherical shape with agglomeration free, and the size increases with increase of synthesis temperature. From DRS studies, it was noticed that the band gap decreases with increase of synthesis temperature. In PL studies, blue peak at 465 nm may be due to defect-related transitions. A sharp intense peak in Raman spectra at 485 cm?1 represents E2H mode is a characteristic of a hexagonal wurtzite structure. The magnetic studies show that the magnetization decreases from 0.0172 to 0.0042 emu/g as the synthesis temperature increases from 400 to 550 °C. ZnO synthesized at 500 °C has a large squareness ratio. These materials are potential candidates for memory devices.
关键词： Combustion method,Spintronics,Ferromagnetism,ZnO nanoparticles
更新于2025-09-09 09:28:46
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Influence of alkali substitution in La0.7Ca0.3Mn0.8Cr0.2O3 perovskite manganite on structural, magnetic, and transport properties
摘要： In order to study the effect of A-site cation mismatch on the structural, magnetic, and transport properties, a systematic investigation of La0.7Ca0.25A0.05Mn0.8Cr0.2O3 (A = Ca, Li, Na, K) has been undertaken. The XRD data of the materials, prepared by glycine-nitrate combustion method, have been analyzed by Rietveld refinement technique. The iodometric and EDX results show that except K doped sample, the desired stoichiometry of all the phases remains the same. The phases display a paramagnetic to ferromagnetic transition at low temperature with Tc found to decrease with decreasing ?rA?. It has been concluded that the conduction mechanism was dominated by small polaron hopping model in the high temperature paramagnetic semiconducting region.
关键词： Combustion method,Transport properties,Magnetic properties,Rietveld refinements
更新于2025-09-09 09:28:46
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Elemental mercury removal from flue gas over TiO2 catalyst in an internal-illuminated honeycomb photoreactor
摘要： TiO2 catalyst in an internal-illuminated honeycomb photoreactor was prepared for Hg0 removal from flue gas. The Hg0 removal efficiency was above 95% under the optimal operation condition. With the increasing TiO2 coating value, the Hg0 removal efficiency significantly increased. The catalyst calcined at 400 oC presented optimal Hg0 removal performance, while higher calcination temperature weakened the Hg0 photocatalytic removal activity. Similar Hg0 removal performances were obtained under UV irradiation when the reaction temperature was in the range of 25-90 oC, and 1.5 mW/cm2 of UV light irradiation was competent for Hg0 photocatalytic removal. With the same quantity utilization of TiO2 catalyst, the internal-illuminated honeycomb photoreactor presented better Hg0 removal performance than fixed-bed reactor. Finally, the procedure of Hg removal from flue gas over TiO2 catalyst in internal-illuminated honeycomb photoreactor was proposed, and the product in the Hg0 photocatalytic removal process was analyzed as well.
关键词： mercury,coal combustion,TiO2,photocatalytic removal,photoreactor
更新于2025-09-09 09:28:46
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Investigations on gas-air mixture formation in the ignition chamber of two-stage combustion chamber using high-speed Schlieren imaging
摘要： Combustion of the lean mixture in the spark ignition engines provides higher thermal efficiency compared to the combustion of the stoichiometric mixture but is more restrictive to the ignition systems. Due to the limitations of conventional ignition systems, advanced concepts are being used, e.g. spark-jet ignition. Presented research has been carried to determine: 1. The impact of fuel injection pressure on the velocity of mixture formation, 2. Fuel distribution inside the ignition chamber in defined phases of chamber filling, 3. Influence of chamber back-pressure on gas jet development. Investigations have been carried using the Schlieren-method with “Z”-setup basing on two ? = 150 mm parabolic mirrors. Images have been recorded with LaVision HSS5 camera with CMOS transducer. The paper contains a comparison of gas penetration parameters for a different injection pressures and chamber backpressures. The injection into the quasi-static air has been compared to the injection in dynamic conditions. It is stated, that both injection pressure and chamber back-pressure influence gas jet-development in the ignition chamber. The regions of the chamber with increased swirling and therefore providing more efficient micromixing have been identified.
关键词： lean mixture,combustion,Schlieren method,spark-jet ignition,gas jet development
更新于2025-09-09 09:28:46
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Coherent Anti-Stokes Raman Spectroscopy of a Hydrogen Diffusion Flame in a Ramjet
摘要： Dual-pump coherent anti-Stokes Raman spectroscopy (CARS) was used to measure the mole fractions of major species as well as the rotational and vibrational temperatures of molecular nitrogen in a hydrogen-fueled dual-mode scramjet flowpath operated in the “ram” mode. Developments in CARS methods and uncertainties are described, including a detailed analysis of the effects of spatial averaging. The mean and standard deviation of the turbulent fluctuations of the temperature and mole fractions at multiple planes in the flowpath and scatter plots of vibrational and rotational temperature are presented. The flame is stabilized downstream of the ramp and grows under the influence of turbulence and rollup of the counterrotating vortex pair formed at the ramp; combustion continues in accelerating flow approaching the end of the measurement domain. Thermal nonequilibrium is observed in the mixing of air with the molecular hydrogen jet close to the injector. Spatial averaging errors are significant at some locations; new methods to correct these errors are described.
关键词： Coherent Anti-Stokes Raman Spectroscopy,CARS,thermal nonequilibrium,hydrogen diffusion flame,supersonic combustion,spatial averaging,ramjet
更新于2025-09-04 15:30:14
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Application of Al-Doped SiC High Emissivity Powder Material Based on Infrared Radiating Coating
摘要： Combustion synthesis technology was used to prepare an Al-doped SiC infrared radiating ceramic powder material. The material’s microstructure was analyzed by XRD, TEM and an IRE-2 infrared emitting ability survey meter. The relationship between the powder’s architectural feature and the infrared radiating performance was obtained. According to the results, the Al atom enters the intracell by replacing a silicon atom and forms a structure of finite replacement-type solid solution, which results in an expansion of the SiC lattice parameter that consequently forms multiple structural defects, distorts the lattice and improves the emissivity. Furthermore, we found that the powder’s normal emissivity in the scope of 8-12 μm can reach 0.99. Finally, the powder’s application to infrared heating coating is discussed.
关键词： SiC lattice,Emissivity,Infrared radiating coating,Combustion synthesis
更新于2025-09-04 15:30:14
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Bi <sub/>5</sub> O <sub/>7</sub> NO <sub/>3</sub> and Ag/Bi <sub/>5</sub> O <sub/>7</sub> NO <sub/>3</sub> composites: one-step solution combustion synthesis, characterization and photocatalytic properties
摘要： In the present study, Bi5O7NO3 and Ag/Bi5O7NO3 composites, as novel efficient photocatalysts, were synthesized via a one-step solution combustion synthesis (SCS) using bismuth nitrate (Bi(NO3)3·5H2O) as an oxidant, tartaric acid (C4H6O6) as a fuel, and silver nitrate (AgNO3) as an Ag source. The amount of Ag in the composite was tailored by varying the AgNO3 content during the SCS process. The orthorhombic Bi5O7NO3 crystal structure was confirmed by XRD, FT-IR and XPS. It was found by EDS and TEM that in the Ag-containing composite, Ag was uniformly distributed on the Bi5O7NO3 matrix. The Ag decoration improved the Bi5O7NO3 photocatalytic efficiency for methyl orange (MO) degradation, likely owing to the relatively low recombination rates of electrons and holes. The 5 mol% Ag/Bi5O7NO3 composite exhibited the best photocatalytic performance (95% in 60 min), which was 1.5 times higher compared to that of pure Bi5O7NO3. In addition, a mechanism of the photocatalytic MO degradation reaction was proposed, which the reactive species O2? played an important role in degrading pollutants.
关键词： Bi5O7NO3,methyl orange degradation,Ag/Bi5O7NO3 composites,solution combustion synthesis,photocatalytic properties
更新于2025-09-04 15:30:14