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
Al2O3-Ni interface formed under vacuum condition is non-wetting and weak. Severe instantaneous intedecial reaction (i.e. wetting) at the Al2O3-Ni interface promoted by oxygen can create a strengthened interface. The N...Al2O3-Ni interface formed under vacuum condition is non-wetting and weak. Severe instantaneous intedecial reaction (i.e. wetting) at the Al2O3-Ni interface promoted by oxygen can create a strengthened interface. The NiAl2O4 spinel-Ni intedece is weak and growth of the spinel interphase is detrimental to the Al2O3-Ni intedecial bonding. A proper control of the oxygen partial pressure can achieve wetting while avoiding the existence of spinel at the interface, producing stronger interfaces by both mechanical interlocking and more intimate chemical bonding in an Al2O3-20 vol pct Ni composite.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.
文摘Al2O3-Ni interface formed under vacuum condition is non-wetting and weak. Severe instantaneous intedecial reaction (i.e. wetting) at the Al2O3-Ni interface promoted by oxygen can create a strengthened interface. The NiAl2O4 spinel-Ni intedece is weak and growth of the spinel interphase is detrimental to the Al2O3-Ni intedecial bonding. A proper control of the oxygen partial pressure can achieve wetting while avoiding the existence of spinel at the interface, producing stronger interfaces by both mechanical interlocking and more intimate chemical bonding in an Al2O3-20 vol pct Ni composite.
