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Effects of Heat-Treatment on Photoluminescence Spectra and Photocatalytic Properties of Solution-Combusted ZnO Nanopowders
摘要： ZnO nanopowders were prepared by a solution combustion method (SCM). The SCM ZnO nanopowders were heat-treated at 200, 400, 500, or 700 °C for 30 min in air and the photoluminescence (PL) of the nanopowders was evaluated. Two strong PL emission peaks are generally recognized as the unique PL signature of ZnO, one is from the band-edge emission and the other corresponds to green emission. The green emission is derived from crystalline defects, and is a critical obstacle for the electrooptical applications of ZnO. Surprisingly, the PL spectra of the SCM ZnO powders showed a single sharp peak near 390 nm. Furthermore, the intensity of this blue emission doubled when the synthesized ZnO powder was heat-treated at 400 °C. The green emission appeared for the sample treated at 500 °C, and was the highest for that treated at 700 °C. To confirm the photocatalytic activity of the ZnO powder heat-treated at 400 °C, the removal of Ag ions from a used photofilm developer was evaluated, with complete removal within 10 min. The removal of the Ag ions by the ZnO powder heat-treated at 400 °C was more than two orders of magnitude faster than that achieved with the SCM ZnO powder. The relation between PL and photocatalytic activity was explained in terms of recombination of the photogenerated electrons. These results might be very useful for highly efficient photocatalyst applications.
关键词： Heat-Treatment,ZnO Nanopowder,PL Spectra,Solution Combustion Method
更新于2025-09-23 15:22:29
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Iron Oxide Nanopowders Obtained via Pulsed Laser Ablation, for Supercapacitors
摘要： Nano-sized magnetite powders with addition of iron nitrides were synthesized via pulsed laser ablation (PLA) of an iron target in atmospheric air. A series of iron oxide nanopowders with various phase compositions (ranging from magnetite to hematite) and structures (from 2D lamellas and spherical nanoparticles to continuous 3D structures) were prepared via heat treatment of the initial (as-synthesized) powder at temperatures in the range 200–500°C. The powders were introduced into the composition of carbon paste electrodes (CPEs). The capacitive characteristics of the electrodes prepared were studied in comparison to a commercial electroexplosive iron oxide powder. The capacitances of electrodes were matched to the structural characteristics of the materials and their phase compositions. With the chosen electrode-preparation method, the powder heat-treated at 500°С (sample Fe/500) showed the highest capacitance. The potential of the studied ultrafine materials based on ablative iron oxide was shown for use in electrodes for supercapacitors.
关键词： supercapacitor,specific capacitance,pulsed laser ablation,iron oxides,nanopowder
更新于2025-09-23 15:19:57
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Synthesis of high-purity zircon, zirconia, and silica nanopowders from local zircon sand
摘要： High-purity zircon (ZrSiO4) nanopowder was successfully produced from Indonesian natural zircon sand using a low-cost purification approach via magnetic separation, immersion in HCl, and reaction with NaOH, followed by a top-down nanosizing process using wet ball-milling for 10 hours and annealing at 200 °C for 2 hours. Furthermore, polymorph zirconia (ZrO2 – amorphous, tetragonal, and monoclinic) and silica (SiO2 – amorphous and cristobalite) nanopowders were also successfully derived from the purified zircon powder using a bottom-up method via alkali fusion and co-precipitation processes followed by calcination. The crystallite size of the powders was estimated from X-ray diffraction (XRD) data analysis to give 40, 31, 61, and 149 nm, respectively, for the zircon, tetragonal- and monoclinic-zirconia, and cristobalite. Microstructural characteristics of the zircon, silica, and zirconia nanopowders were revealed in transmission electron microscopy (TEM) images which confirmed that the average sizes of the particles were in a good agreement with the XRD estimated values.
关键词： zircon,tetragonal zirconia,amorphous silica,nanopowder,cristobalite,monoclinic zirconia
更新于2025-09-23 15:19:57
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Enhancing the structural, optical and electrical properties of ZnO nanopowders through (Al+Mn) doping
摘要： Undoped ZnO and Zn0.97-xAl0.03MnxO (x = 0, 1, 2 and 3%) nanopowders (NPs) were synthesized by co-precipitation method. They were characterized by X-ray diffraction (XRD), Fourier transformed infrared (FTIR), Raman, UV-visible, photoluminescence (PL) and impedance spectroscopies. All samples exhibit a single phase wurtzite type. The average crystallite size lying between 22 and 42 nm was found to increase for all doped ZnO samples. The optical transmission in the visible region was improved due to doping. The optical band gap is in the range of 3-3.4 eV and was found to decrease up to 2% of Mn content but slightly increases with further doping. All PL spectra exhibit two emission peaks in UV and visible regions. The deconvolution of the visible emission peak reveals different emissions for all samples. An additional yellow emission is noticed for (Al+Mn) ZnO doped samples suggesting that the incorporation of aluminum and manganese in the zinc oxide host lattice enhances luminescence properties of ZnO. The ac conductivity (σac) was found to follow Jonscher’s power law and was improved with doping. Cole-Cole plots of all samples were suitably fitted to a circuit consisting in a parallel combination of a resistance and a constant phase element (CPE).
关键词： optical properties,XRD,doping,conductivity,ZnO nanopowder
更新于2025-09-19 17:15:36
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Selective Laser Melting of Nanocomposite Ti-6Al-4V and TiC Powder
摘要： The paper presents the study results of the selective laser melting process of the Ti-6Al-4V alloy and nanosized powder TiC composition. The results of the particles morphology study of resulting powder composition after blending are presented. The microstructure and mechanical characteristics of the obtained composite material were studied. Study of microstructures using optical and electron microscopes were conducted.
关键词： Titanium Alloy Composite,Powder Metallurgy,Selective Laser Melting,TiC,Nanopowder
更新于2025-09-16 10:30:52
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Spectroscopic studies on Cr3+ doped ZnCdO nanostructures for optoelectronic device application
摘要： Cr3+ ion doped ZnCdO nanopowder was synthesized by chemical solution method. Structural (X-ray di?raction, surface morphology and energy dispersion), di?erent spectroscopic studies like FT-IR, EPR, Optical and PL were performed on the prepared nanopowders. From the XRD pattern, it was con?rmed that the crystalline size of the nanopowder was at nanoscale range. The morphological surface of the powder was analyzed by SEM. FT-IR showed the trademark assimilation groups identi?ed with the metal oxides and additionally other natural particles. EPR spectrum exhibited characteristic Cr3+ ion resonance signal at g = 1.98. By connecting EPR and optical information, the holding parameters have been resolved. From the optical absorption studies, the assimilation groups are assessed. Photoluminescence studies showed that the out?ow groups are in UV and blue area. These parameters recommended that Cr3+ ions are in octahedral site symmetry with covalent bonding nature.
关键词： Cr3+ ion doped ZnCdO nanopowder,EPR,FTIR,XRD,Optical,PL
更新于2025-09-12 10:27:22
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Fabrication of Metal Matrix Composite by Laser Metal Deposition—A New Process Approach by Direct Dry Injection of Nanopowders
摘要： Laser Metal Deposition (LMD) offers new perspectives for the fabrication of metal matrix nanocomposites (MMnCs). Current methods to produce MMnCs by LMD systematically involve the premixing of the nanopowders and the micropowders or require in-situ strategies, thereby restricting the possibilities to adjust the nature, content and location of the nano-reinforcement during printing. The objective of this study is to overcome such restrictions and propose a new process approach by direct injection of nanoparticles into a metallic matrix. Alumina (n-Al2O3) nanoparticles were introduced into a titanium matrix by using two different direct dry injection modes in order to locally increase the hardness. Energy dispersive X-ray spectroscopy (EDS) analyses validate the successful incorporation of the n-Al2O3 at chosen locations. Optical and high resolution transmission electron microscopic (HR-TEM) observations as well as X-ray diffraction (XRD) analyses indicate that n-Al2O3 powders are partly or totally dissolved into the Ti melted pool leading to the in-situ formation of a composite consisting of fine α2 lamellar microstructure within a Ti matrix and a solid solution with oxygen. Mechanical tests show a significant increase in hardness with the increase of injected n-Al2O3 amount. A maximum of 620 HV was measured that is almost 4 times higher than the pure LMD-printed Ti structure.
关键词： laser metal deposition,solid solution,direct nanopowder injection,lamellar microstructure,hardness,titanium aluminide,metal matrix composite
更新于2025-09-12 10:27:22
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Fabrication of La2O3 Uniformly Doped Mo Nanopowders by Solution Combustion Synthesis Followed by Reduction under Hydrogen
摘要： This work reports the preparation of La2O3 uniformly doped Mo nanopowders with the particle sizes of 40–70 nm by solution combustion synthesis and subsequent hydrogen reduction (SCSHR). To reach this aim, the foam-like MoO2 precursors (20–40 nm in size) with different amounts of La2O3 were first synthesized by a solution combustion synthesis method. Next, these precursors were used to prepare La2O3 doped Mo nanopowders through hydrogen reduction. Thus, the content of La2O3 used for doping can be accurately controlled via the SCSHR route to obtain the desired loading degree. The successful doping of La2O3 into Mo nanopowders with uniform distribution were proved by X-ray photon spectroscopy and transmission electron microscopy. The preservation of the original morphology and size of the MoO2 precursor by the La2O3 doped Mo nanopowders was attributed to the pseudomorphic transport mechanism occurring at 600 ?C. As shown by X-ray diffraction, the formation of Mo2C impurity, which usually occurs in the direct H2 reduction process, can be avoided by using the Ar calcination-H2 reduction process, when residual carbon is removed by the carbothermal reaction during Ar calcination at 500 ?C.
关键词： hydrogen reduction,La2O3,Mo nanopowder,doping,solution combustion synthesis
更新于2025-09-10 09:29:36
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Tailoring the Structural and Optical Parameters of Eu3+:CeO2-SiO2 Nanopowder Via Thermal Treatment
摘要： Nanocrystalline Eu3+:CeO2-SiO2 powder samples were prepared by sol-gel technique. This technique is suitable for large-scale production and it is also a cost effective process. The prepared samples were annealed at different temperatures which were characterized by many complementary techniques. The formation of cubic fluorite structure of CeO2 nanocrystal with a uniform distribution was confirmed by x-ray diffraction (XRD) and transmission electron microscopy (TEM). The average nanocrystalline size has been calculated as 3, 7 and 15 nm using Debye-Scherrer formula for different annealed samples. The calculated nanocrystalline sizes were compared with W-H plot and TEM histograms. It was investigated that FWHM of diffraction peaks decreases with increase in temperature results in increase nanocrystalline size. The FTIR spectroscopy provides the valuable information and identification of different chemical group/bonds present in the prepared samples. It is found that if we fixed the dopant concentration, then particle size, morphology and band gap energy of prepared nanopowder can be tailored by applying the annealing conditions. Comparative studies of absorption spectra and corresponding band gap energies have been done and a red shift has been observed in absorption spectra with thermal treatment. The shift of the optical absorption edge of prepared nanopowder towards lower energies increases its utilization in the visible region specially photocatalytic activity.
关键词： Thermal annealing,Absorption spectra,Structural properties,Nanopowder,Band gap energy
更新于2025-09-10 09:29:36
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An investigation on electroless nickel coating on yttria stabilized zirconia nanoparticles via single step surface activation methods
摘要： Metal coated ceramic nanopowders have a considerable potential for many fields of applications. Here, electroless coating of pure nickel onto yttria-stabilized zirconia nanoparticles is studied. We introduce a single step method to activate ceramic nanoparticles surface to reduce complexities of electroless coating on ceramic nanoparticles by conventional double step pre-treatments. X-ray diffraction and electron diffraction patterns beside transmission electron microscopy images are used to analyze the coated nanoparticles. We observe that palladium hydroxide acts as a catalyst for electroless nickel reaction like palladium and the ceramic nanopowders surface is effectively activated for electroless reaction by simpler single step activation methods. Atomic absorption spectroscopy results show that the performance of electroless reaction is not enhanced by increase in catalyst amount. Also, relative changes in amount of deposited nickel are investigated via magnetization curves of the coated particles. The vibrating sample magnetometery results demonstrate the magnetic behavior of the processed particles can be modified by deposited nickel amount.
关键词： Catalysis,Nickel,coating,Palladium,Electroless,YSZ nanopowder
更新于2025-09-09 09:28:46