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Effect of calcium oxide doping on the microstructure and optical properties of YAG transparent ceramics
摘要： Yttrium aluminium garnet (YAG, Y3Al5O12) transparent ceramics were fabricated by vacuum sintering the co-precipitated raw powders with calcium oxide (CaO) as the sintering aid. The influence of CaO content on the phase composition, particle size and the morphologies of resultant YAG powders, as well as the microstructural and optical properties of YAG ceramics, was investigated in detail. Our results show that with increasing of CaO additives, the particle size and agglomeration degree of the powders were slightly increased and the grain growth of the ceramics was inhibited. Specifically, the grain size initially decreased dramatically till reaching a minimum value of 1.85 μm with 0.3 at% CaO, then slightly increased. In addition, for YAG ceramics with a high CaO doping level, the existence of liquid phase was observed for the first time and its sintering mechanism was discussed. The excess of CaO causes the formation of grain boundary phases and residual pores, which are detrimental for maintaining higher optical quality of YAG ceramics. We obtained a fully dense and pore-free YAG ceramic with an in-line transmittance of 80.8% at 1100 nm by adopting 0.1 at% level of CaO during sintering of the green bodies at 1780°C for 20 h in vacuum.
关键词： Microstructure evolution,YAG transparent ceramic,Co-precipitation method,CaO additives
更新于2025-09-10 09:29:36
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The effects of gadolinium doping on the structural, morphological, optical, and photoluminescence properties of zinc oxide nanoparticles prepared by co-precipitation method
摘要： Pure and gadolinium (Gd)-doped zinc oxide (ZnO) nanoparticles were prepared by co-precipitation method. The EDS analysis confirmed the presence of Gd3+ ions in ZnO lattice. The X-ray diffraction measurement indicated the formation of hexagonal wurtzite structure for both pure and Gd-doped ZnO nanoparticles. The structural parameters of nanoparticles such as lattice constant, crystallite size, dislocation density, micro strain and other lattice parameters were calculated from XRD data. FESEM images of nanoparticles showed that the grain morphology of nanoparticles tends to hexagonal form by introducing Gd3+ ions into the ZnO lattice. The presence of functional groups and chemical bonding attributed to ZnO was confirmed by FT-IR measurement. The optical properties of nanoparticles were investigated by UV–Vis spectroscopy. The UV–Vis absorbance spectra, for Gd-doped samples, illustrated a blue shift by increasing Gd concentration. Also, the band gap of nanoparticles increased by increasing Gd concentration. The photoluminescence spectra of Gd-doped nanoparticles showed that the intensity of green luminescence increases by substitution of Gd3+ ions into the ZnO lattice attributed to the oxygen vacancies.
关键词： structural properties,morphological properties,co-precipitation method,gadolinium doping,zinc oxide nanoparticles,optical properties,photoluminescence properties
更新于2025-09-10 09:29:36
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Eu:Lu2O3 transparent ceramics fabricated by vacuum sintering of co-precipitated nanopowders
摘要： Europium doped lutetium oxide (Eu:Lu2O3) nanopowders were synthesized by a co-precipitation method using hydrogen carbonate (AHC) as a precipitant. Influence of the terminal pH value on properties of the Eu:Lu2O3 precursors and calcined powders was investigated. It is found that the terminal pH value has little influence on compositions of the precursors, and all the powders calcined at 1100 °C show good crystallinity. However, the terminal pH value has significant influence on morphology and agglomeration degree of both the precursors and the calcined powders. The powders are found to have the optimal dispersity with the average particle size of 68 nm when the terminal pH is 6.57. Using the nanopowders as starting materials, Eu:Lu2O3 transparent ceramics were fabricated by vacuum sintering at 1700 °C for 30 h. The ceramics prepared from the powders whose terminal pH is 6.57 were found to have the best transparency and the in-line transmittance reaches 68% at 611 nm. The influence of vacuum sintering temperatures on the microstructure and transmittance of the Eu:Lu2O3 transparent ceramics was also investigated. The Eu:Lu2O3 ceramics sintered at 1825 °C for 30 h show the highest in-line transmittance of 72% at 611 nm. The average grain size of the prepared Eu:Lu2O3 ceramics is about 454 μm and the light output of the sample is about 10 times higher than that of commercial BGO single crystal.
关键词： Vacuum sintering,Eu:Lu2O3 transparent ceramics,Terminal pH value,Co-precipitation method,Light yield,Microstructure
更新于2025-09-10 09:29:36
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Preparation of TiO <sub/>2</sub> nanoparticles by hydrolysis of TiCl <sub/>4</sub> using water and glycerol solvent system
摘要： The anatase phase TiO2 nanoparticles (NPs) were synthesized by precipitation method using TCl4 as a precursor in a new reaction medium containing water and glycerol. The as-synthesized photocatalysts were characterized by Raman spectroscopy, Fourier Transform Infra-red Spectroscopy (FT-IR), UV-Visible spectroscopy and Field Emission Scanning Electron Microscopy (FESEM). The Raman spectra indicate the formation of crystalline anatase phase TiO2 NPs after calcination at 300 and 4000C. TiO2 NPs formation was confirmed by observing the major characteristic, FT-IR vibration bands of Ti-O network. The band gap calculated from UV-Vis DRS spectra ranged from 3.02-3.28 eV. FESEM images exhibit spherical shape TiO2 NPs in the form of nano-clusters with crystallite sizes ranged from 9.50-26.14 nm. FESEM images show that as the calcination temperature increases, the sizes of the TiO2 NPs also increase. The inclusion of glycerol promotes the formation of smaller particles and lowers the band gap of TiO2 NPs.
关键词： precipitation method,TiO2 nanoparticles,hydrolysis,anatase phase,Raman spectroscopy,FESEM,UV-Visible spectroscopy,water and glycerol solvent system,FT-IR,TiCl4
更新于2025-09-09 09:28:46
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An efficient fabrication of ZnO–carbon nanocomposites with enhanced photocatalytic activity and superior photostability
摘要： Synthesis of carbon nanoparticles (CNPs) and their composite with ZnO has proposed for the first time by combustion of camphor and chemical precipitation method. TEM image shows the surface of ZnO covered by tiny CNPs and acts as structure directing agent that transforms ZnO nanorods to uniform spherical ZnO. CNPs play a vital role to improve the photocatalytic activity and photostability of ZnO up to five runs due to impeding the photo-corrosion of ZnO. Enhance in the photocatalytic activity of ZnO–carbon nanocomposite could be attributed to the excellent dye adsorption capacity, direct photooxidation of dye and suppression of photoinduced electron–hole recombination. The presence of CNPs in nanocomposite served as the main role in accepting the photogenerated electrons due to electronic interaction between ZnO and CNPs. The cytotoxicity studies of meristematic root tip cells of Allium cepa reveals that photocatalytically degraded products were less toxic.
关键词： Photostability,ZnO–carbon nanocomposites,Photocatalytic activity,Chemical precipitation method,Camphor combustion
更新于2025-09-09 09:28:46
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Optimization of the liquid–liquid interfacial precipitation method for the synthesis of $$\hbox {C}_{60}$$C60 nanotubes
摘要： Tubular fullerene nanowhiskers called ‘fullerene nanotubes’ are composed of C60 fullerene molecules (C60 NTs) are synthesized at room temperature using the liquid–liquid interfacial precipitation method in the pyridine and isopropyl alcohol (IPA) system. The growth control of fullerene nanotubes is important for their chemical and physical properties as well as for their future applications. In the present study, we investigated the effect of light, water, solvent ratio and temperature on the synthesis of C60 nanotubes. A marked development in the yield of C60 NTs was achieved using dehydrated solvents, a solution with a volume ratio of 1:9 for pyridine: IPA, a growth temperature equal to 5?C and by illuminating the C60-pyridine solution with ultraviolet light (wavelength 302 nm) for 102 h. The synthesized fullerene nanotubes were characterized by different analytical techniques including Raman and Fourier transform infrared spectroscopy, optical microscopy, focussed ion beam scanning electron microscopy and transmission electron microscopy.
关键词： solution growth,liquid–liquid interfacial precipitation method,light,temperature,solvent,Fullerene nanotubes
更新于2025-09-09 09:28:46
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Improved Hydrophobicity of Polydimethylsiloxane (PDMS) Coating with ZnO Nanostructures
摘要： In this present work, an environmentally safe hydrophobic cotton surface comprising of PDMS and different morphology of Zinc oxide (ZnO) nanostructures via simple dip coating method was developed. ZnO nanosphere and ZnO nanoflakes were synthesized via sol gel method while ZnO nanorods were synthesized via solution precipitation method. The precursors used to prepared ZnO nanospheres, nanoflakes and nanorods are zinc acetate dehydrate, zinc chloride and zinc nitrate tetrahydrate respectively. ZnO nanostructures were analysed using FESEM and XRD. The hydrophobic cotton surface was characterized via FT-IR and WCA analysis. A WCA of 144.15° was achieved when coating the cotton with ZnO nanoflakes (ZnO-NF:PDMS).
关键词： ZnO nanostructures,Polydimethylsiloxane,Solution precipitation method,Hydrophobicity,Sol gel method,Dip coating
更新于2025-09-04 15:30:14
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Ultra-small amorphous carbon dots: preparation, photoluminescence properties, and their application as TiO2 photosensitizers
摘要： Ultra-small carbon quantum dots (s-CQDs) with excitation wavelength-independent fluorescence had been obtained by hydrothermal-followed acid precipitation method and were characterized by FT-IR, TEM, XPS, UV–Vis and XRD. It was found that as-prepared s-CQDs were amorphous spherical particles with an average diameter of 1.51 nm, and there were abundant hydroxyl and carbonyl groups on their surfaces. Moreover, fluorescence emission study found that the luminescence of s-CQDs was aroused by oxygen group decorated on its surface, and the fluorescence properties of s-CQDs were much different from those of large CQDs (l-CQDs), which showed higher quantum yield and better photoluminescence (PL) property than that of l-CQDs. The PL of s-CQDs possessed two emission centers and was exhibited to be excitation independent. When s-CQDs was used as photosensitizer for TiO2 to photocatalytic degradation of methylene blue under visible light irradiation, it showed significantly improved photocatalytic activities compared with 1-CQDs, and the degradation efficiency of methylene blue reached up to 96.6%. The high degradation efficiency was attributed to the ultra-small particle size, abundant acidic groups, and excellent optical properties of s-CQDs.
关键词： Photocatalytic degradation,Ultra-small carbon quantum dots,TiO2 photosensitizers,Photoluminescence,Hydrothermal-followed acid precipitation method
更新于2025-09-04 15:30:14