NiAl2O4,CuAl2O4,and ZnAl2O4 aluminate spinel nanoparticles were synthesized by sol-gel auto combustion method using diethanolamine(DEA)as a fuel.The effects of calcination temperature on structure,crystallinity,morpho...NiAl2O4,CuAl2O4,and ZnAl2O4 aluminate spinel nanoparticles were synthesized by sol-gel auto combustion method using diethanolamine(DEA)as a fuel.The effects of calcination temperature on structure,crystallinity,morphology,and optical properties of MAl2O4(M=Ni,Cu,Zn)have been investigated by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM),UV–visible diffuse reflectance spectroscopy(UV-DRS),and photoluminescence(PL)spectroscopy.The XRD and FT-IR results confirm the formation of single-phase spinel structure of NiAl2O4,CuAl2O4,and ZnAl2O4 at 1200,1000,and 600℃,respectively.The direct band gap of these aluminate spinels,calculated from UV-DRS spectra using the Kubelka–Munk function,is found to increase with calcination temperature.The PL spectra demonstrate that NiAl2O4 gives the highest blue emission intensity,while CuAl2O4 and ZnAl2O4 exhibit a very strong violet emission.During fluorescence process,the ZnAl2O4 emits visible light in only violet and blue regions,while Ni Al2O4 and CuAl2O4 emissions extend to the green region.It seems therefore that the transition metal type and intrinsic defects in these aluminate powders are responsible for these phenomena.展开更多
Microstructure of reaction sintering of ZnAl2O4 at 1500℃ by hot-pressing(HP) and pulse electric current was investigated. The results indicated that the existed cracks in sintered body were caused by structure mismat...Microstructure of reaction sintering of ZnAl2O4 at 1500℃ by hot-pressing(HP) and pulse electric current was investigated. The results indicated that the existed cracks in sintered body were caused by structure mismatch. It is the evidence that periodical temperature field existed during pulse electric current sintering of nonconductive materials. The distance between high temperature areas was related to die diameter.展开更多
A ZnAl2O4@SiO2 nanocomposite was prepared from metal nitrates and tetraethyl orthosilicate by the sol-gel process,and characterized by X-ray diffraction,Fourier transform infrared,transmission electron microscopy,and ...A ZnAl2O4@SiO2 nanocomposite was prepared from metal nitrates and tetraethyl orthosilicate by the sol-gel process,and characterized by X-ray diffraction,Fourier transform infrared,transmission electron microscopy,and N2 adsorption-desorption measurements.The nanocomposite was tested as a heterogeneous catalyst for the acetylation of alcohols,phenols,and amines under solvent-free conditions.Under optimized conditions,efficient acetylation of these substrates with acetic anhydride over the ZnAl2O4@SiO2 nanocomposite was obtained.Acetylation of anilines and primary aliphatic amines proceeded rapidly at room temperature,while the reaction time was longer for the acetylation of alcohols and phenols,showing that an amine NH2 group can be selectively acetylated in the presence of alcoholic or phenolic OH groups.The catalyst can be reused without obvious loss of catalytic activity.The catalytic activity of the ZnAl2O4@SiO2 nanocomposite was higher than that of pure ZnAl2O4.The method gives high yields,and is clean,cost effective,compatible with substrates having other functional groups and it is suitable for practical organic synthesis.展开更多
With the solid phase reaction between pulsed-laser-deposited (PLD) ZnOfilm and α-Al2O3 substrate, ZnAl2O4/α-Al2O3 complex substrates were synthesized. X-ray diffraction (XRD) spectra show that as the reaction procee...With the solid phase reaction between pulsed-laser-deposited (PLD) ZnOfilm and α-Al2O3 substrate, ZnAl2O4/α-Al2O3 complex substrates were synthesized. X-ray diffraction (XRD) spectra show that as the reaction proceeds, ZnAl2O4 changes from the initial (111)-oriented single crystal to poly-crystal, and then to inadequate (111) orientation. Corresponding scanning electron microscope (SEM)images indicate that the surface morphology of ZnAl2O4 transforms from uniform islands to stick structures, and then to bulgy-line structures. In addition, XRDspectra present that ZnAl2O4 prepared at low temperature is unstable at the environment of higher temperature. On the as-obtained ZnAl2O4/α-Al2O3 substrates, GaN films were grown without any nitride buffer using light-radiation heating low-pressure MOCVD (LRH-LP-MOCVD). XRD spectra indicate that GaN film on this kind of complex substrate changes from c-axis single crystal to poly-crystal as ZnAl2O4 layer is thickened. For the single crystal GaN, its full width at half maximum (FWHM) of X-ray rocking curve is 0.4°. Results indicate that islands on thin ZnAl2O4 layer can promote nucleation at initial stage of GaN growth, which leadsto the (0001)-oriented GaN film.展开更多
基金financially supported by Faculty of Science at Sriracha, Kasetsart University, Sriracha Campusthe Kasetsart University Research and Development Institute (KURDI), Bangkok, Thailand
文摘NiAl2O4,CuAl2O4,and ZnAl2O4 aluminate spinel nanoparticles were synthesized by sol-gel auto combustion method using diethanolamine(DEA)as a fuel.The effects of calcination temperature on structure,crystallinity,morphology,and optical properties of MAl2O4(M=Ni,Cu,Zn)have been investigated by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM),UV–visible diffuse reflectance spectroscopy(UV-DRS),and photoluminescence(PL)spectroscopy.The XRD and FT-IR results confirm the formation of single-phase spinel structure of NiAl2O4,CuAl2O4,and ZnAl2O4 at 1200,1000,and 600℃,respectively.The direct band gap of these aluminate spinels,calculated from UV-DRS spectra using the Kubelka–Munk function,is found to increase with calcination temperature.The PL spectra demonstrate that NiAl2O4 gives the highest blue emission intensity,while CuAl2O4 and ZnAl2O4 exhibit a very strong violet emission.During fluorescence process,the ZnAl2O4 emits visible light in only violet and blue regions,while Ni Al2O4 and CuAl2O4 emissions extend to the green region.It seems therefore that the transition metal type and intrinsic defects in these aluminate powders are responsible for these phenomena.
基金This work was supported by the National Natural Science Foundation of China under grant No.50232020 and 50220160657.
文摘Microstructure of reaction sintering of ZnAl2O4 at 1500℃ by hot-pressing(HP) and pulse electric current was investigated. The results indicated that the existed cracks in sintered body were caused by structure mismatch. It is the evidence that periodical temperature field existed during pulse electric current sintering of nonconductive materials. The distance between high temperature areas was related to die diameter.
基金supported by the Lorestan University Research Council and Iran nanotechnology Initiative Council
文摘A ZnAl2O4@SiO2 nanocomposite was prepared from metal nitrates and tetraethyl orthosilicate by the sol-gel process,and characterized by X-ray diffraction,Fourier transform infrared,transmission electron microscopy,and N2 adsorption-desorption measurements.The nanocomposite was tested as a heterogeneous catalyst for the acetylation of alcohols,phenols,and amines under solvent-free conditions.Under optimized conditions,efficient acetylation of these substrates with acetic anhydride over the ZnAl2O4@SiO2 nanocomposite was obtained.Acetylation of anilines and primary aliphatic amines proceeded rapidly at room temperature,while the reaction time was longer for the acetylation of alcohols and phenols,showing that an amine NH2 group can be selectively acetylated in the presence of alcoholic or phenolic OH groups.The catalyst can be reused without obvious loss of catalytic activity.The catalytic activity of the ZnAl2O4@SiO2 nanocomposite was higher than that of pure ZnAl2O4.The method gives high yields,and is clean,cost effective,compatible with substrates having other functional groups and it is suitable for practical organic synthesis.
基金Special Funds for Major State Basic Research Projects of China(Grant No.#G20000683)Distinguished Young Scientist Grant of China (Grant No.60025411)+1 种基金the National Natural Science Foundation of China(Grant Nos.69806006,69976014,69636010 and 69987001)the National High Technology Research & Development Project of China
文摘With the solid phase reaction between pulsed-laser-deposited (PLD) ZnOfilm and α-Al2O3 substrate, ZnAl2O4/α-Al2O3 complex substrates were synthesized. X-ray diffraction (XRD) spectra show that as the reaction proceeds, ZnAl2O4 changes from the initial (111)-oriented single crystal to poly-crystal, and then to inadequate (111) orientation. Corresponding scanning electron microscope (SEM)images indicate that the surface morphology of ZnAl2O4 transforms from uniform islands to stick structures, and then to bulgy-line structures. In addition, XRDspectra present that ZnAl2O4 prepared at low temperature is unstable at the environment of higher temperature. On the as-obtained ZnAl2O4/α-Al2O3 substrates, GaN films were grown without any nitride buffer using light-radiation heating low-pressure MOCVD (LRH-LP-MOCVD). XRD spectra indicate that GaN film on this kind of complex substrate changes from c-axis single crystal to poly-crystal as ZnAl2O4 layer is thickened. For the single crystal GaN, its full width at half maximum (FWHM) of X-ray rocking curve is 0.4°. Results indicate that islands on thin ZnAl2O4 layer can promote nucleation at initial stage of GaN growth, which leadsto the (0001)-oriented GaN film.
