Commercially available niobium (V) oxide [Nb2O5], with barium acetate [Ba(CH3COO)2] and magnesium acetate [Mg(CH3COO)2-4H2O] was used as the starting material in the sol-gel process for preparing Ba(Mg1/3Nb2/3)O3 (BMN...Commercially available niobium (V) oxide [Nb2O5], with barium acetate [Ba(CH3COO)2] and magnesium acetate [Mg(CH3COO)2-4H2O] was used as the starting material in the sol-gel process for preparing Ba(Mg1/3Nb2/3)O3 (BMN) nanopowders. At first, Nb2O5 reacted with melting sodium hydroxide and transformed into dispersible oxide. The resulting glassy substance after cooling was dispersed and washed several times in distilled water to remove the Na+ ions. The as-prepared colloidal Nb2O5-nH2O was subsequently mixed with acetic solution of barium acetate and magnesium acetate according to the required molar proportions and followed by gelation. The ultrafine BMN powders were finally obtained after heat-treating the gel at 820℃for 1 h, and the as-sintered nanoceramics revealed a high relative density of 98.2%, and a high microwave Q-factor, of 10397 at 1.45GHz.展开更多
Commercially available niobium (V) oxide [Nb_2O_5], with barium acetate[Ba(CH_3COO)_2] and magnesium acetate [Mg(CH_3COO)_2·4H_2O] was used as the starting material inthe sol-gel process for preparing Ba(Mg_(1/3)...Commercially available niobium (V) oxide [Nb_2O_5], with barium acetate[Ba(CH_3COO)_2] and magnesium acetate [Mg(CH_3COO)_2·4H_2O] was used as the starting material inthe sol-gel process for preparing Ba(Mg_(1/3)Nb_(2/3))O_3 (BMN) nanopowders. At first, Nb_2O_5reacted with melting sodium hydroxide and transformed into dispersible oxide. The resulting glassysubstance after cooling was dispersed and washed several times in distilled water to remove the Na^+ions. The as-prepared colloidal Nb_2O_5·nH_2O was subsequently mixed with acetic solution ofbarium acetate and magnesium acetate according to the required molar proportions and followed bygelation. The ultrafine BMN powders were finally obtained after heat-treating the gel at 820℃ for 1h, and the as-sintered nanoceramics revealed a high relative density of 98.2%, and a high microwaveQ-factor, of 10397 at 1,45GHz.展开更多
Agglomeration-free nanosized ZrO2-HfO2-Y2O3-Sc2O3 composite powders were successfully synthesized by Sol-Gel technique in heated aqueous solution of alcohol, using analytically pure ZrOCl2 · 8H2O, HfOCl2·8H2...Agglomeration-free nanosized ZrO2-HfO2-Y2O3-Sc2O3 composite powders were successfully synthesized by Sol-Gel technique in heated aqueous solution of alcohol, using analytically pure ZrOCl2 · 8H2O, HfOCl2·8H2O, Y（NO3）3·6H2O, and Sc2O3 as raw materials. The effect of synthesis condition on the size and dispersity of the composite powders was investigated by means of XRD, TEM, and TG-DSC techniques. The results showed that well-dispersed predecessor of ZrO2-HfO2-Y2O3-Sc2O3 composite nanopowders could be obtained. The optional condition ： PEG6000 as dispersant was 1%, alcohol/H2O ratio was 5/1, metallic ion concentration in whole solution was 0.5 mol·L^-1 and the pH value of the solution was 12. After calcined at 620 ℃, the powder obtained was in uniform cubic structure, and its average particle size was about 13 nm, which was good for producing nanocrystalline solid electrolyte.展开更多
（Y0.87La0.1Zr0.03）2O3 nanopowders doped with various concentrations of Tm^3＋ and Ho^3＋ were prepared by the citrate method. The standard cubic Y2O3 phase can be matched in the Tm^3＋/Ho^3＋ co-doped（Y0.87La0.1Zr0...（Y0.87La0.1Zr0.03）2O3 nanopowders doped with various concentrations of Tm^3＋ and Ho^3＋ were prepared by the citrate method. The standard cubic Y2O3 phase can be matched in the Tm^3＋/Ho^3＋ co-doped（Y0.87La0.1Zr0.03）2 O3 nanopowders. The nanopowders exhibit average particle sizes of 40,60, 80 and 100 nm after calcinated at 900,1000,1100 and 1200℃,respectively. The energy transfer from Tm^3＋ to Ho^3＋ and the optimum fluorescence emission around 2 μm were investigated. Results indicate that the emission bands at around 1.86 and 1.95 μm correspond to 3 F4→3 H6 transition of Tm^3＋ and 5 I7→5 I8 transition of Ho^3＋, respectively.Better spectral properties were achieved in Tm^3＋/Ho^3＋ co-doped（Y0.87La0.1Zr0.03）2O3 nanopowders with the average size of 100 nm obtained at the conditions of the treatment of precursors calcinated at 1200 ℃ for 2 h doped with 1.5 mol% Tm^3＋ and 1 mol% Ho^3＋.展开更多
A hydrothermal method was successfully used for synthesis of CuO/ZnO/AI203 （CZA） nanopowder with atomic ratio of 6：3：1. The effect of crystallization time （3, 6, 9, and 12 h） on physicochemical properties of nan...A hydrothermal method was successfully used for synthesis of CuO/ZnO/AI203 （CZA） nanopowder with atomic ratio of 6：3：1. The effect of crystallization time （3, 6, 9, and 12 h） on physicochemical properties of nanopowder was investigated. Nanopowders were characterized using XRD, FESEM, EDX, FTIR, TG, and BET techniques. The XRD patterns confirmed metal oxides formation and their good crystallinity with average crystallite size of 20nm as obtained by the Scherrer equation. Relative crystallinity was shown to increase with increasing crystallization time. In agreement with XRD results, FESEM images also illustrated nanosized particles. EDX mapping indicated homogenous dispersion of elements. BET specific surface area analysis showed acceptable surface area for CZA nanopowder, FTIR spectroscopy confirmed metal oxides formation during hydrothermal and calcination processing. TG results illustrated high thermal stability of the synthesized nanopowders. TG-DTG and FTIR analyses were used to propose a reaction mechanism for nanopowder formation during processing. Physicochemical characterization showed optimal crystallization time to be 6 h.展开更多
This paper describes the combustion synthesis ofα-Fe2O3 nanopowder at much lower temperature and its catalytic activity for the one-pot preparation of 3,4-dihydropyrano[c]chromenes.The combustion derivedα-Fe_2O_3 na...This paper describes the combustion synthesis ofα-Fe2O3 nanopowder at much lower temperature and its catalytic activity for the one-pot preparation of 3,4-dihydropyrano[c]chromenes.The combustion derivedα-Fe_2O_3 nanopowder was characterized by powder X-ray diffraction（PXRD）,Braunauer,Emmett and Teller（BET） surface area,scanning electron microscopy（SEM） and Fourier transform infrared spectroscopy（FTIR）.Highly efficient,three-component condensation of aromatic aldehyde,malanonitrile and 4- hydroxycoumarin catalyzed byα-Fe2O3 nanoparticles at room temperature is described.The method offers an excellent alternative to the synthesis of 3,4-dihydropyrano[c]chromenes.The reactions are rapid,clean,and the products with good yield and high purity.展开更多
Nanosized terbium doped Lu2O3 phosphors were synthesized via a modified co-precipitation processing. The as-prepared Tb:Lu2O3 phosphors was consisted of well crystallized nanosized sphere particles with a diameter of ...Nanosized terbium doped Lu2O3 phosphors were synthesized via a modified co-precipitation processing. The as-prepared Tb:Lu2O3 phosphors was consisted of well crystallized nanosized sphere particles with a diameter of about 30 nm. Local structure of Tb ions in Lu2O3 lattice was investigated by an analytical approach based on Fourier transformation of the extended X-ray absorption fine structure (EXAFS) data. X-ray near edge structure (XANES) spectra suggested that all Tb ions doped were tervalence. EXAFS results indicated that Tb ions have entered the Lu2O3 cubic lattice by means of solid solution. The coordination number and first shell Tb-O distance dropped with the increasing of Tb concentration. Emission spectra of the phosphors was shown to be typical for Tb3+ with main components at 542, 550 and 490 nm, derived from irradiative relaxation of 5D4 level. The emission intensity decreased severely with the increasing of Tb concentration from 1 mol.% to 15 mol.%, suggesting a significant concentration quenching above 1 mol.% Tb. The reduction of emission intensity was interpreted by higher distortion derived relaxation among the surface state resident Tb3+ ions.展开更多
W-Y2O3 composite nanopowders prepared via wet chemical method exhibit unique morphologies and micro structures.The yttrium addition during chemical reaction process affects not only the composition of tungsten acid hy...W-Y2O3 composite nanopowders prepared via wet chemical method exhibit unique morphologies and micro structures.The yttrium addition during chemical reaction process affects not only the composition of tungsten acid hydrate precursors,but also the reduction property of tungsten oxide transformed from precursors.In this study,the morphology evolution of the samples with and without yttrium during reduction process has been studied,and it is found that the addition of yttrium can exert a strong influence on the reduction route of tungsten oxide and the final morphology of tungsten particles.The cause of the difference of reduction route and tungsten particle morphology is also analyzed.It is suggested that the composition of the samples with yttrium at the beginning of reduction is pure cubic system WO3(c-WO3),and the c-WO3 particles have c-WO3 whiskers attached to the surface.This kind of whiskers is essential for c-WO3 to be reduced directly to tungsten and also helpful to obtain W-Y2O3 powders with small size and good uniformity.展开更多
文摘Commercially available niobium (V) oxide [Nb2O5], with barium acetate [Ba(CH3COO)2] and magnesium acetate [Mg(CH3COO)2-4H2O] was used as the starting material in the sol-gel process for preparing Ba(Mg1/3Nb2/3)O3 (BMN) nanopowders. At first, Nb2O5 reacted with melting sodium hydroxide and transformed into dispersible oxide. The resulting glassy substance after cooling was dispersed and washed several times in distilled water to remove the Na+ ions. The as-prepared colloidal Nb2O5-nH2O was subsequently mixed with acetic solution of barium acetate and magnesium acetate according to the required molar proportions and followed by gelation. The ultrafine BMN powders were finally obtained after heat-treating the gel at 820℃for 1 h, and the as-sintered nanoceramics revealed a high relative density of 98.2%, and a high microwave Q-factor, of 10397 at 1.45GHz.
文摘Commercially available niobium (V) oxide [Nb_2O_5], with barium acetate[Ba(CH_3COO)_2] and magnesium acetate [Mg(CH_3COO)_2·4H_2O] was used as the starting material inthe sol-gel process for preparing Ba(Mg_(1/3)Nb_(2/3))O_3 (BMN) nanopowders. At first, Nb_2O_5reacted with melting sodium hydroxide and transformed into dispersible oxide. The resulting glassysubstance after cooling was dispersed and washed several times in distilled water to remove the Na^+ions. The as-prepared colloidal Nb_2O_5·nH_2O was subsequently mixed with acetic solution ofbarium acetate and magnesium acetate according to the required molar proportions and followed bygelation. The ultrafine BMN powders were finally obtained after heat-treating the gel at 820℃ for 1h, and the as-sintered nanoceramics revealed a high relative density of 98.2%, and a high microwaveQ-factor, of 10397 at 1,45GHz.
基金Project supported by the National Natural Science Foundation of China (20101006)Nano Technology Special Foundationof Shanghai Science and Technology Committee (0452nm073) and Shanghai Education Committee
文摘Agglomeration-free nanosized ZrO2-HfO2-Y2O3-Sc2O3 composite powders were successfully synthesized by Sol-Gel technique in heated aqueous solution of alcohol, using analytically pure ZrOCl2 · 8H2O, HfOCl2·8H2O, Y（NO3）3·6H2O, and Sc2O3 as raw materials. The effect of synthesis condition on the size and dispersity of the composite powders was investigated by means of XRD, TEM, and TG-DSC techniques. The results showed that well-dispersed predecessor of ZrO2-HfO2-Y2O3-Sc2O3 composite nanopowders could be obtained. The optional condition ： PEG6000 as dispersant was 1%, alcohol/H2O ratio was 5/1, metallic ion concentration in whole solution was 0.5 mol·L^-1 and the pH value of the solution was 12. After calcined at 620 ℃, the powder obtained was in uniform cubic structure, and its average particle size was about 13 nm, which was good for producing nanocrystalline solid electrolyte.
基金Project supported by Zhejiang Provincial Natural Science Foundation of China(LZ14B010001)
文摘（Y0.87La0.1Zr0.03）2O3 nanopowders doped with various concentrations of Tm^3＋ and Ho^3＋ were prepared by the citrate method. The standard cubic Y2O3 phase can be matched in the Tm^3＋/Ho^3＋ co-doped（Y0.87La0.1Zr0.03）2 O3 nanopowders. The nanopowders exhibit average particle sizes of 40,60, 80 and 100 nm after calcinated at 900,1000,1100 and 1200℃,respectively. The energy transfer from Tm^3＋ to Ho^3＋ and the optimum fluorescence emission around 2 μm were investigated. Results indicate that the emission bands at around 1.86 and 1.95 μm correspond to 3 F4→3 H6 transition of Tm^3＋ and 5 I7→5 I8 transition of Ho^3＋, respectively.Better spectral properties were achieved in Tm^3＋/Ho^3＋ co-doped（Y0.87La0.1Zr0.03）2O3 nanopowders with the average size of 100 nm obtained at the conditions of the treatment of precursors calcinated at 1200 ℃ for 2 h doped with 1.5 mol% Tm^3＋ and 1 mol% Ho^3＋.
基金Sahand University of Technology for the financial support of the project and Iran Nano-technology Initiative Council for supplementary financial supports
文摘A hydrothermal method was successfully used for synthesis of CuO/ZnO/AI203 （CZA） nanopowder with atomic ratio of 6：3：1. The effect of crystallization time （3, 6, 9, and 12 h） on physicochemical properties of nanopowder was investigated. Nanopowders were characterized using XRD, FESEM, EDX, FTIR, TG, and BET techniques. The XRD patterns confirmed metal oxides formation and their good crystallinity with average crystallite size of 20nm as obtained by the Scherrer equation. Relative crystallinity was shown to increase with increasing crystallization time. In agreement with XRD results, FESEM images also illustrated nanosized particles. EDX mapping indicated homogenous dispersion of elements. BET specific surface area analysis showed acceptable surface area for CZA nanopowder, FTIR spectroscopy confirmed metal oxides formation during hydrothermal and calcination processing. TG results illustrated high thermal stability of the synthesized nanopowders. TG-DTG and FTIR analyses were used to propose a reaction mechanism for nanopowder formation during processing. Physicochemical characterization showed optimal crystallization time to be 6 h.
基金VTU(VTU/Aca./2009-10/A-9/11714) for the financial support and Chemistry-TEQIP Laboratory of MSRIT and SSMRV College, Chemistry Research Center
文摘This paper describes the combustion synthesis ofα-Fe2O3 nanopowder at much lower temperature and its catalytic activity for the one-pot preparation of 3,4-dihydropyrano[c]chromenes.The combustion derivedα-Fe_2O_3 nanopowder was characterized by powder X-ray diffraction（PXRD）,Braunauer,Emmett and Teller（BET） surface area,scanning electron microscopy（SEM） and Fourier transform infrared spectroscopy（FTIR）.Highly efficient,three-component condensation of aromatic aldehyde,malanonitrile and 4- hydroxycoumarin catalyzed byα-Fe2O3 nanoparticles at room temperature is described.The method offers an excellent alternative to the synthesis of 3,4-dihydropyrano[c]chromenes.The reactions are rapid,clean,and the products with good yield and high purity.
基金Project supported by the National Natural Science Foundation of China (11079026)the Basic Research Key Project of Shanghai Municipal (09JC1406500)+1 种基金Shanghai leading Academic Disciplines (S30107)the Postgraduate Innovation Fund of Shanghai University (SHUCX102237)
文摘Nanosized terbium doped Lu2O3 phosphors were synthesized via a modified co-precipitation processing. The as-prepared Tb:Lu2O3 phosphors was consisted of well crystallized nanosized sphere particles with a diameter of about 30 nm. Local structure of Tb ions in Lu2O3 lattice was investigated by an analytical approach based on Fourier transformation of the extended X-ray absorption fine structure (EXAFS) data. X-ray near edge structure (XANES) spectra suggested that all Tb ions doped were tervalence. EXAFS results indicated that Tb ions have entered the Lu2O3 cubic lattice by means of solid solution. The coordination number and first shell Tb-O distance dropped with the increasing of Tb concentration. Emission spectra of the phosphors was shown to be typical for Tb3+ with main components at 542, 550 and 490 nm, derived from irradiative relaxation of 5D4 level. The emission intensity decreased severely with the increasing of Tb concentration from 1 mol.% to 15 mol.%, suggesting a significant concentration quenching above 1 mol.% Tb. The reduction of emission intensity was interpreted by higher distortion derived relaxation among the surface state resident Tb3+ ions.
基金financially supported by the National Natural Science Foundation of China(Nos.51822404 and 51574178)the Science and Technology Program of Tianjin(No.18YFZCGX00070)+1 种基金the Natural Science Foundation of Tianjin(No.18JCYBJC17900)the Seed Foundation of Tianjin University(Nos.2018XRX-0005 and 2019XYF-0066).
文摘W-Y2O3 composite nanopowders prepared via wet chemical method exhibit unique morphologies and micro structures.The yttrium addition during chemical reaction process affects not only the composition of tungsten acid hydrate precursors,but also the reduction property of tungsten oxide transformed from precursors.In this study,the morphology evolution of the samples with and without yttrium during reduction process has been studied,and it is found that the addition of yttrium can exert a strong influence on the reduction route of tungsten oxide and the final morphology of tungsten particles.The cause of the difference of reduction route and tungsten particle morphology is also analyzed.It is suggested that the composition of the samples with yttrium at the beginning of reduction is pure cubic system WO3(c-WO3),and the c-WO3 particles have c-WO3 whiskers attached to the surface.This kind of whiskers is essential for c-WO3 to be reduced directly to tungsten and also helpful to obtain W-Y2O3 powders with small size and good uniformity.
