The melting temperature and critical transition temperature Tc of YBa2Cu3O7-δ with deferent content additives of PbO and BaPbO3 were studied. When PbO was doped in YBa2Cu3O7-δ, the melting temperature of YBa2Cu3O7-...The melting temperature and critical transition temperature Tc of YBa2Cu3O7-δ with deferent content additives of PbO and BaPbO3 were studied. When PbO was doped in YBa2Cu3O7-δ, the melting temperature of YBa2Cu3O7-δ was reduced, however its superconductivity was weakened. From the XRD pattern of the sintered mixture of YBa2Cu3O7-δ and PbO, it was known that there was a reaction between YBa2Cu3O7-δ and PbO, and the product was BaPbO3. Hence different contents of BaPbO3 (10mass%, 20mass% and 30mass%) were added in YBa2Cu3O7-δ. It was proved that there were no reactions between YBa2Cu3O7-δ and BaPbO3. And the superconductivity of the mixtures was much better than that of the samples with PbO additive.展开更多
The effects of B2O3 addition, as a sintering agent, on the sintering behavior, microstructure and dielectric properties of CaMgSi2O6 ceramic have been investigated. The CaO-MgO-B2O3-SiO2 glassy phase came forth by add...The effects of B2O3 addition, as a sintering agent, on the sintering behavior, microstructure and dielectric properties of CaMgSi2O6 ceramic have been investigated. The CaO-MgO-B2O3-SiO2 glassy phase came forth by adding B2O3 into CaO-MgO-SiO2 ceramic powders, and it was advantageous to lower the synthesis temperature of CaMgSi2O6 crystalline phase. Moreover, the emergence of CaO-MgO-B2O3-SiO2 glass phase could effectively lower the sintering temperature of CaMgSi2O6 ceramic and promote the CaMgSi2O6 grains growing. With 6 wt pct B2O3 addition, the densification temperature of CaMgSi2O6 ceramic could be effectively reduced from 1300 to 1100℃, and the dielectric constant （εr） and dielectric loss （tanδ） were： εr=7.61 and tanδ=7.4×10^-4 （1 MHz）.展开更多
ZrO2, TiO2 and P2O5 were doped in CaO-B2O3-SiO2 glass-ceramics as nucleating additives. Effects of different nucleating additives on the phase separation and crystalline behaviors were investigated by using gradient t...ZrO2, TiO2 and P2O5 were doped in CaO-B2O3-SiO2 glass-ceramics as nucleating additives. Effects of different nucleating additives on the phase separation and crystalline behaviors were investigated by using gradient temperature furnace, DTA and XRD. Then, sintering process of the glass-ceramics was investigated by testing sintering shrinkage, dielectric constant and loss. The experimental results shows that the glass-ceramics doped with nucleating additives represents higher crystallization, with ZrO2 as an exceptional effective dopant to promote the precipitation of wollastonite crystal. Finally, ZrO2 containing glass-ceramics was chosen to study the influence of sintering temperature and soaking time with the help of X-ray diffraction analysis and density measurement. The glass-ceramics can be well consolidated at 850 ℃ for 10 min, with low dielectric constant （5.87） and loss （3.21×10^-4）, which is desirable for LTCC application.展开更多
To improve the mechanical properties of WC-Al2O3 composites, the effects of trace amount of CeO2 additives on the microstructure and mechanical properties of the WC-Al2O3 composites prepared by hot pressing were inves...To improve the mechanical properties of WC-Al2O3 composites, the effects of trace amount of CeO2 additives on the microstructure and mechanical properties of the WC-Al2O3 composites prepared by hot pressing were investigated. The results revealed that the WC-Al2O3 composites doped with 0.1% CeOz possessed refined microstructure and enhanced mechanical properties compared with that of the undoped WC-Al2O3composites. Trace CeO2 suppressed the decarburization of WC, promoted the microstructural refinement, and improved the interface coherence of the WC matrix and Al2O3. When 0.1% CeO2 was added to the WC-Al2O3 composites, the effect of CeO2 resulted in the achievement of a relative density of 98.82% with an excellent Vickers hardness of 16.89 GPa, combining a fracture toughness of 9.85 MPa. m1/2 with an acceptable flexural strength of 1 024.05 MPa.展开更多
The effects of Yb2O3 particles on the microstructure and transport properties of YBa2Cu3O7-δ(YBCO) were investigated through resistance-temperature(R-T),scanning electron microscope(SEM),X-ray diffraction(XRD) and th...The effects of Yb2O3 particles on the microstructure and transport properties of YBa2Cu3O7-δ(YBCO) were investigated through resistance-temperature(R-T),scanning electron microscope(SEM),X-ray diffraction(XRD) and the critical current density(Jc) versus applied magnetic field(Jc-B) measurements.YBCO powder with Yb2O3 additives was synthesized using standard solid state reaction technique.Rietveld refinements of X-ray diffraction showed that both Yb2O3 and YBCO phases coexisted in the products.The critical current density(Jc) exhibited a maximum at x=0.05 in YBCO+xYb2O3 systems.Moreover,small additions of Yb2O3 in YBCO could enhance Jc by applying the magnetic field,although the superconducting temperature(Tc) decreased monotonically with increasing additive content.The characteristic behavior of Jc might come from the counterbalance of two effects simultaneously,which was caused by the inhomogeneity of grains distribution in nano-scale and degradation on superconducting properties.展开更多
Lead-free glass-ceramic composites in barium sodium niobate silica system with Gd2O3 addition were synthesized through melt-casting fol-lowed by controlled crystallization technique. Crystallization and dielectric pro...Lead-free glass-ceramic composites in barium sodium niobate silica system with Gd2O3 addition were synthesized through melt-casting fol-lowed by controlled crystallization technique. Crystallization and dielectric properties of the Gd2O3 adding glass-ceramic composites were investigated. With the increase in the concentration of Gd2O3, the glass transition temperature and the crystallization temperature of the pre-cursor glass shift towards the higher temperature. The crystallization behavior that occurred during the heat treatment procedure leads to the enhancement of dielectric constant. All the three compositions of glass-ceramic composites exhibit ferroelectricity when tested at room tem-perature. Both the values of the remanent polarization and coercive field are enhanced regularly with the gradual increase in the concentration of Gd2O3 additive under the same testing field.展开更多
Effect of Y2O3-MgO addition on heterogeneous precipitation-thermal reduction synthesis and the sintering of Fe-Mo/Si3N4 powders has been investigated. It was found that the whiskers-like β-Si3N4, good wettability pha...Effect of Y2O3-MgO addition on heterogeneous precipitation-thermal reduction synthesis and the sintering of Fe-Mo/Si3N4 powders has been investigated. It was found that the whiskers-like β-Si3N4, good wettability phases on Si3N4 surface, and high toughness Fe phase appeared in Fe-Mo/Si3N4 cermets with Y2O3-MgO additives. The results show that Y2O3-MgO additives can effectively optimize the microstructures of Fe-Mo/ Si3N4 cermets, and improve the material mechanical properties. Therefore, it indicated that Y2O3-MgO additives can be used for strengthening of eintered cermets, and the dual function of whiskers self-toughening and different metal-composition toughening can be achieved in Fe-Mo/Si3N4 cermets with Y2O3-MgO additives.展开更多
A series of Na-doped 1 wt% Pd/Al2O3 catalysts with different Na loadings were prepared by wet impregnation and tested for the catalytic oxidation of benzene. Suitable addition of Na had a remarkable promotion effect o...A series of Na-doped 1 wt% Pd/Al2O3 catalysts with different Na loadings were prepared by wet impregnation and tested for the catalytic oxidation of benzene. Suitable addition of Na had a remarkable promotion effect on water resistance and enhancement of low temperature activity of Pd/Al2O3 catalysts. The optimal mole ratio between Na and Pd was 1:1. The properties of the prepared catalysts were characterized by X-ray diffraction (XRD), Brunauer Emmett Teller (BET), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), O2-temperature-programmed desorption (O2-TPD), and in situ DRIFTS. Results indicated that the addition of Na not only decreased the content of adsorbed water species but also increased the amount of liable surface oxygen species, which are likely the key factors for the excellent water resistance of the catalyst. Na addition also improved the mobility of the lattice oxygen species, which was favorable for catalytic activity. Moreover, the well-dispersed negatively charged Pd particles and suitable redox properties derived from Na addition also contributed to the improved performance and water resistance of the Na1Pd1/Al2O3 catalyst. In situ DRIFTS results revealed that benzene was oxidized to maleate and acetate species via intermediate o-benzoquinone species, which finally turned into harmless CO2 and H2O.展开更多
Michael addition of nitroalkanes to α,β-unsaturated carbonyl compounds occurs in the presence of KF/AI_2O_3/PEG4000 without solvent.Yields are fair to good and work-ups are easy.
TiO_2 modified Al_2O_3 binary oxide was prepared by a wet-impregnation method and used as the support for ruthenium catalyst. The catalytic performance of Ru/TiO_2–Al_2O_3catalyst in CO_2 methanation reaction was inv...TiO_2 modified Al_2O_3 binary oxide was prepared by a wet-impregnation method and used as the support for ruthenium catalyst. The catalytic performance of Ru/TiO_2–Al_2O_3catalyst in CO_2 methanation reaction was investigated. Compared with Ru/Al_2O_3 catalyst, the Ru/TiO_2–Al_2O_3catalytic system exhibited a much higher activity in CO_2 methanation reaction. The reaction rate over Ru/TiO_2–Al_2O_3 was 0.59 mol CO_2·(g Ru)1·h-1, 3.1 times higher than that on Ru/Al_2O_3[0.19 mol CO_2·(gRu)-1·h-1]. The effect of TiO_2 content and TiO_2–Al_2O_3calcination temperature on catalytic performance was addressed. The corresponding structures of each catalyst were characterized by means of H_2-TPR, XRD, and TEM. Results indicated that the averaged particle size of the Ru on TiO_2–Al_2O_3support is 2.8 nm, smaller than that on Al_2O_3 support of 4.3 nm. Therefore, we conclude that the improved activity over Ru/TiO_2–Al_2O_3catalyst is originated from the smaller particle size of ruthenium resulting from a strong interaction between Ru and the rutile-TiO_2 support, which hindered the aggregation of Ru nanoparticles.展开更多
The β-aminocarboxylic acid derivatives were synthesized by Michael addition reaction of alkyl amine and α,β-unsaturated carbonyl compounds in the presence of potassium fluoride on alumina.
Photodegradation has emerged as an environmentally friendly method of decomposing harmful dyes in wastewater. In this study, core-shell Fe3O4/SiO2/ TiO2 nanospheres with magnetic cores were obtained from synthesised m...Photodegradation has emerged as an environmentally friendly method of decomposing harmful dyes in wastewater. In this study, core-shell Fe3O4/SiO2/ TiO2 nanospheres with magnetic cores were obtained from synthesised magnetic Fe3O4 nanoparticles through the precipitation method, the surface of the magnetic Fe3O4 nanoparticles was coated with a silica (SiO2) layer by hydrolysis of tetramethoxysilane (TMOS) as a silica source, and finally, Fe3O4/SiO2 nanospheres were coated with titanium (TiO2) layer using tetrabutyltitanate (TBT) as a precursor through the sol-gel process. The morphology and structure of the prepared materials were characterised by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), X-ray energy dispersive spectrometry (EDAX), Fourier transform infrared spectroscopy (FT-IR), and atomic force microscopy (AFM). The photocatalytic activities of the prepared core-shell nanospheres were studied using binary azo dyes, namely methyl orange (anionic dye, MO) and methylene blue (cationic dye, MB) in aqueous solution under UV light irradiation (365 nm), and UV-Vis spectrophotometer was utilised to monitor the amount of each dye in the mixture. It was found that 90.2% and 100% of binary MO and MB were removed for 5 h, respectively. The results revealed that the efficiency of the photocatalytic degradation of the core-shell nanospheres was not degreased after five runs that can be used as recyclable photocatalysts. The results show that the performance of the prepared core-shell nanospheres was better than that of commercial TiO2 nanoparticles. Moreover, the magnetic separation properties of the core-shell Fe3O4/SiO2/TiO2 nanospheres can enable the prepared materials to have wider application prospects.展开更多
文摘The melting temperature and critical transition temperature Tc of YBa2Cu3O7-δ with deferent content additives of PbO and BaPbO3 were studied. When PbO was doped in YBa2Cu3O7-δ, the melting temperature of YBa2Cu3O7-δ was reduced, however its superconductivity was weakened. From the XRD pattern of the sintered mixture of YBa2Cu3O7-δ and PbO, it was known that there was a reaction between YBa2Cu3O7-δ and PbO, and the product was BaPbO3. Hence different contents of BaPbO3 (10mass%, 20mass% and 30mass%) were added in YBa2Cu3O7-δ. It was proved that there were no reactions between YBa2Cu3O7-δ and BaPbO3. And the superconductivity of the mixtures was much better than that of the samples with PbO additive.
基金supported by the Program for New Century Excellent Talents in University (No. NCET-07-0786)the Nature Science Foundation of Zhejiang Province (No. R406007)the Science Technology of Zhejiang Province (No. 2008C21054)
文摘The effects of B2O3 addition, as a sintering agent, on the sintering behavior, microstructure and dielectric properties of CaMgSi2O6 ceramic have been investigated. The CaO-MgO-B2O3-SiO2 glassy phase came forth by adding B2O3 into CaO-MgO-SiO2 ceramic powders, and it was advantageous to lower the synthesis temperature of CaMgSi2O6 crystalline phase. Moreover, the emergence of CaO-MgO-B2O3-SiO2 glass phase could effectively lower the sintering temperature of CaMgSi2O6 ceramic and promote the CaMgSi2O6 grains growing. With 6 wt pct B2O3 addition, the densification temperature of CaMgSi2O6 ceramic could be effectively reduced from 1300 to 1100℃, and the dielectric constant （εr） and dielectric loss （tanδ） were： εr=7.61 and tanδ=7.4×10^-4 （1 MHz）.
基金Funded by the Shanghai Leading Academic Discipline Project (B502)Shanghai Key Laboratory Project (08DZ2230500)
文摘ZrO2, TiO2 and P2O5 were doped in CaO-B2O3-SiO2 glass-ceramics as nucleating additives. Effects of different nucleating additives on the phase separation and crystalline behaviors were investigated by using gradient temperature furnace, DTA and XRD. Then, sintering process of the glass-ceramics was investigated by testing sintering shrinkage, dielectric constant and loss. The experimental results shows that the glass-ceramics doped with nucleating additives represents higher crystallization, with ZrO2 as an exceptional effective dopant to promote the precipitation of wollastonite crystal. Finally, ZrO2 containing glass-ceramics was chosen to study the influence of sintering temperature and soaking time with the help of X-ray diffraction analysis and density measurement. The glass-ceramics can be well consolidated at 850 ℃ for 10 min, with low dielectric constant （5.87） and loss （3.21×10^-4）, which is desirable for LTCC application.
文摘To improve the mechanical properties of WC-Al2O3 composites, the effects of trace amount of CeO2 additives on the microstructure and mechanical properties of the WC-Al2O3 composites prepared by hot pressing were investigated. The results revealed that the WC-Al2O3 composites doped with 0.1% CeOz possessed refined microstructure and enhanced mechanical properties compared with that of the undoped WC-Al2O3composites. Trace CeO2 suppressed the decarburization of WC, promoted the microstructural refinement, and improved the interface coherence of the WC matrix and Al2O3. When 0.1% CeO2 was added to the WC-Al2O3 composites, the effect of CeO2 resulted in the achievement of a relative density of 98.82% with an excellent Vickers hardness of 16.89 GPa, combining a fracture toughness of 9.85 MPa. m1/2 with an acceptable flexural strength of 1 024.05 MPa.
基金Project supported by the Program for Key Teachers in Jiangsu University of Science and Technology (37270901)
文摘The effects of Yb2O3 particles on the microstructure and transport properties of YBa2Cu3O7-δ(YBCO) were investigated through resistance-temperature(R-T),scanning electron microscope(SEM),X-ray diffraction(XRD) and the critical current density(Jc) versus applied magnetic field(Jc-B) measurements.YBCO powder with Yb2O3 additives was synthesized using standard solid state reaction technique.Rietveld refinements of X-ray diffraction showed that both Yb2O3 and YBCO phases coexisted in the products.The critical current density(Jc) exhibited a maximum at x=0.05 in YBCO+xYb2O3 systems.Moreover,small additions of Yb2O3 in YBCO could enhance Jc by applying the magnetic field,although the superconducting temperature(Tc) decreased monotonically with increasing additive content.The characteristic behavior of Jc might come from the counterbalance of two effects simultaneously,which was caused by the inhomogeneity of grains distribution in nano-scale and degradation on superconducting properties.
基金supported by the National Natural Science Foundation of China (No. 51107005)
文摘Lead-free glass-ceramic composites in barium sodium niobate silica system with Gd2O3 addition were synthesized through melt-casting fol-lowed by controlled crystallization technique. Crystallization and dielectric properties of the Gd2O3 adding glass-ceramic composites were investigated. With the increase in the concentration of Gd2O3, the glass transition temperature and the crystallization temperature of the pre-cursor glass shift towards the higher temperature. The crystallization behavior that occurred during the heat treatment procedure leads to the enhancement of dielectric constant. All the three compositions of glass-ceramic composites exhibit ferroelectricity when tested at room tem-perature. Both the values of the remanent polarization and coercive field are enhanced regularly with the gradual increase in the concentration of Gd2O3 additive under the same testing field.
基金supported by the National Natural Science Foundation of China (Nos. 51274093 and 50804016)the Key Discipline Project Foundation of Hunan Province, China (No. 0805)
文摘Effect of Y2O3-MgO addition on heterogeneous precipitation-thermal reduction synthesis and the sintering of Fe-Mo/Si3N4 powders has been investigated. It was found that the whiskers-like β-Si3N4, good wettability phases on Si3N4 surface, and high toughness Fe phase appeared in Fe-Mo/Si3N4 cermets with Y2O3-MgO additives. The results show that Y2O3-MgO additives can effectively optimize the microstructures of Fe-Mo/ Si3N4 cermets, and improve the material mechanical properties. Therefore, it indicated that Y2O3-MgO additives can be used for strengthening of eintered cermets, and the dual function of whiskers self-toughening and different metal-composition toughening can be achieved in Fe-Mo/Si3N4 cermets with Y2O3-MgO additives.
基金supported by the National Natural Science Foundation of China (No. 51608504)Youth Innovation Promotion AssociationChinese Academy of Sciences(No. 2017064)
文摘A series of Na-doped 1 wt% Pd/Al2O3 catalysts with different Na loadings were prepared by wet impregnation and tested for the catalytic oxidation of benzene. Suitable addition of Na had a remarkable promotion effect on water resistance and enhancement of low temperature activity of Pd/Al2O3 catalysts. The optimal mole ratio between Na and Pd was 1:1. The properties of the prepared catalysts were characterized by X-ray diffraction (XRD), Brunauer Emmett Teller (BET), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), O2-temperature-programmed desorption (O2-TPD), and in situ DRIFTS. Results indicated that the addition of Na not only decreased the content of adsorbed water species but also increased the amount of liable surface oxygen species, which are likely the key factors for the excellent water resistance of the catalyst. Na addition also improved the mobility of the lattice oxygen species, which was favorable for catalytic activity. Moreover, the well-dispersed negatively charged Pd particles and suitable redox properties derived from Na addition also contributed to the improved performance and water resistance of the Na1Pd1/Al2O3 catalyst. In situ DRIFTS results revealed that benzene was oxidized to maleate and acetate species via intermediate o-benzoquinone species, which finally turned into harmless CO2 and H2O.
文摘Michael addition of nitroalkanes to α,β-unsaturated carbonyl compounds occurs in the presence of KF/AI_2O_3/PEG4000 without solvent.Yields are fair to good and work-ups are easy.
基金Supported by the National Natural Science Foundation of China(211031735127108721476226 and 51471076)DICP Fundamental Research Program for Clean Energy(DICPM201307)
文摘TiO_2 modified Al_2O_3 binary oxide was prepared by a wet-impregnation method and used as the support for ruthenium catalyst. The catalytic performance of Ru/TiO_2–Al_2O_3catalyst in CO_2 methanation reaction was investigated. Compared with Ru/Al_2O_3 catalyst, the Ru/TiO_2–Al_2O_3catalytic system exhibited a much higher activity in CO_2 methanation reaction. The reaction rate over Ru/TiO_2–Al_2O_3 was 0.59 mol CO_2·(g Ru)1·h-1, 3.1 times higher than that on Ru/Al_2O_3[0.19 mol CO_2·(gRu)-1·h-1]. The effect of TiO_2 content and TiO_2–Al_2O_3calcination temperature on catalytic performance was addressed. The corresponding structures of each catalyst were characterized by means of H_2-TPR, XRD, and TEM. Results indicated that the averaged particle size of the Ru on TiO_2–Al_2O_3support is 2.8 nm, smaller than that on Al_2O_3 support of 4.3 nm. Therefore, we conclude that the improved activity over Ru/TiO_2–Al_2O_3catalyst is originated from the smaller particle size of ruthenium resulting from a strong interaction between Ru and the rutile-TiO_2 support, which hindered the aggregation of Ru nanoparticles.
文摘The β-aminocarboxylic acid derivatives were synthesized by Michael addition reaction of alkyl amine and α,β-unsaturated carbonyl compounds in the presence of potassium fluoride on alumina.
文摘Photodegradation has emerged as an environmentally friendly method of decomposing harmful dyes in wastewater. In this study, core-shell Fe3O4/SiO2/ TiO2 nanospheres with magnetic cores were obtained from synthesised magnetic Fe3O4 nanoparticles through the precipitation method, the surface of the magnetic Fe3O4 nanoparticles was coated with a silica (SiO2) layer by hydrolysis of tetramethoxysilane (TMOS) as a silica source, and finally, Fe3O4/SiO2 nanospheres were coated with titanium (TiO2) layer using tetrabutyltitanate (TBT) as a precursor through the sol-gel process. The morphology and structure of the prepared materials were characterised by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), X-ray energy dispersive spectrometry (EDAX), Fourier transform infrared spectroscopy (FT-IR), and atomic force microscopy (AFM). The photocatalytic activities of the prepared core-shell nanospheres were studied using binary azo dyes, namely methyl orange (anionic dye, MO) and methylene blue (cationic dye, MB) in aqueous solution under UV light irradiation (365 nm), and UV-Vis spectrophotometer was utilised to monitor the amount of each dye in the mixture. It was found that 90.2% and 100% of binary MO and MB were removed for 5 h, respectively. The results revealed that the efficiency of the photocatalytic degradation of the core-shell nanospheres was not degreased after five runs that can be used as recyclable photocatalysts. The results show that the performance of the prepared core-shell nanospheres was better than that of commercial TiO2 nanoparticles. Moreover, the magnetic separation properties of the core-shell Fe3O4/SiO2/TiO2 nanospheres can enable the prepared materials to have wider application prospects.
