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
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.
Additive Ba（N3）2 as a source of nitrogen is heavily doped into the graphite-Fe-based alloy system to grow nitrogendoped diamond crystals under a relatively high pressure （about 6.0 GPa） by employing the temperatur...Additive Ba（N3）2 as a source of nitrogen is heavily doped into the graphite-Fe-based alloy system to grow nitrogendoped diamond crystals under a relatively high pressure （about 6.0 GPa） by employing the temperature gradient method. Gem-grade diamond crystal with a size of around 5 mm and a nitrogen concentration of about 1173 ppm is successfully synthesised for the first time under high pressure and high temperature in a China-type cubic anvil highpressure apparatus. The growth habit of diamond crystal under the environment with high degree of nitrogen doping is investigated. It is found that the morphologies of heavily nitrogen-doped diamond crystals are all of octahedral shape dominated by {111} facets. The effects of temperature and duration on nitrogen concentration and form are explored by infrared absorption spectra. The results indicate that nitrogen impurity is present in diamond predominantly in the dispersed form accompanied by aggregated form, and the aggregated nitrogen concentration in diamond increases with temperature and duration. In addition, it is indicated that nitrogen donors are more easily incorporated into growing crystals at higher temperature. Strains in nitrogen-doped diamond crystal are characterized by micro-Raman spectroscopy. Measurement results demonstrate that the undoped diamond crystals exhibit the compressive stress, whereas diamond crystals heavily doped with the addition of Ba（N3）2 display the tensile stress.展开更多
Nitroalkanes react smoothly with CF_3CCl_2COCH=CHPh via Michael addition in the presence of inorganic bases such as KF/Al2O3 or K2CO3, giving fluorinecontaining γ-nitro ketones in good yields.
In this study, we applied a novel, mild, and convenient synthetic method involving the oxidative cyclization of 1-(pyrazin-2-yl)guanidine derivatives to produce [1,2,4]triazolo[4,3-a ]pyrazin-3-amines. We optimized th...In this study, we applied a novel, mild, and convenient synthetic method involving the oxidative cyclization of 1-(pyrazin-2-yl)guanidine derivatives to produce [1,2,4]triazolo[4,3-a ]pyrazin-3-amines. We optimized the reaction procedure to easily obtain 5-chloro-[1,2,4]triazolo[4,3-a ]pyrazin-3-amine. Various types of halogenated pyrazines can successfully undergo this process. We synthesized a series of 1-(pyrazin-2-yl)guanidines and [1,2,4]triazolo[4,3-a ]pyrazin-3-amines, and then elucidated their structures based on their ~1H-NMR, ^(13)C-NMR, ESI-HRMS, and nuclear Overhauser effect spectra.展开更多
Zinc metal batteries have been considered as a promising candidate for next-generation batteries due to their high safety and low cost.However,their practical applications are severely hampered by the poor cyclability...Zinc metal batteries have been considered as a promising candidate for next-generation batteries due to their high safety and low cost.However,their practical applications are severely hampered by the poor cyclability that caused by the undesired dendrite growth of metallic Zn.Herein,Ti_(3)C_(2)T_(x) MXene was first used as electrolyte additive to facilitate the uniform Zn deposition by controlling the nucleation and growth process of Zn.Such MXene additives can not only be absorbed on Zn foil to induce uniform initial Zn deposition via providing abundant zincophilic-O groups and subsequently participate in the formation of robust solid-electrolyte interface film,but also accelerate ion transportation by reducing the Zn^(2+) concentration gradient at the electrode/electrolyte interface.Consequently,MXene-containing electrolyte realizes dendrite-free Zn plating/striping with high Coulombic efficiency(99.7%)and superior reversibility(stably up to 1180 cycles).When applied in full cell,the Zn-V_(2)O_(5)cell also delivers significantly improved cycling performances.This work provides a facile yet effective method for developing reversible zinc metal batteries.展开更多
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
Nanocrystalline TiO2 was prepared by high frequency plasma chemical vapor deposition (HF-PCVD). The effects of additive AlCl3 on crystal phase, particle size and microstructurai parameters of TiO2 nanocrystallites wer...Nanocrystalline TiO2 was prepared by high frequency plasma chemical vapor deposition (HF-PCVD). The effects of additive AlCl3 on crystal phase, particle size and microstructurai parameters of TiO2 nanocrystallites were investigated by X-ray diffraction(XRD) and transmission electron microscopy (TEM). The nanocrystallites obtained experimentally are mixture of anatase and rutile, the uniform diameters of particles are about 30 nm. The phase transformation from anatase to rutile was accelerated by AlCl3, and rutile content is increased from 26.7 wt pct to 53.6 wt pct with increasing of addition of AlCl3 from 0.0 wt pct to 5.0 wt pct. The particle size is reduced and the size distribution becomes very narrow. The crystal lattice constants have the trend to decrease, and celi volumes appear as shrinkable.展开更多
Over the past 30 years,additive manufacturing(AM)has developed rapidly and has demonstrated great potential in biomedical applications.AM is a materials-oriented manufacturing technology,since the solidification mecha...Over the past 30 years,additive manufacturing(AM)has developed rapidly and has demonstrated great potential in biomedical applications.AM is a materials-oriented manufacturing technology,since the solidification mechanism,architecture resolution,post-treatment process,and functional application are based on the materials to be printed.However,3D printable materials are still quite limited for the fabrication of bioimplants.In this work.2D/3D AM materials for bioimplants are reviewed.Furthermore,inspired by Tai Chi,a simple yet novel soft/rigid hybrid 4D AM concept is advanced to develop complex and dynamic biological structures in the human body based on 4D printing hybrid ceramic precursor/ceramic materials that were previously developed by our group.With the development of multi-material printing technology,the development of bioimplants and soft/rigid hybrid biological structures with 2D/3D/4D AM materials can be anticipated.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
With a series of 1.0 wt%Bi_(2)O_(3)-x wt%CuO(x=0.0,0.2,0.4,0.6,and 0.8)serving as sintering additives,Ni_(0.23)Cu_(0.32)Zn_(0.45)Ee_(2)O_(4)ferrites are successfully synthesized at a low temperature(900℃)by using the...With a series of 1.0 wt%Bi_(2)O_(3)-x wt%CuO(x=0.0,0.2,0.4,0.6,and 0.8)serving as sintering additives,Ni_(0.23)Cu_(0.32)Zn_(0.45)Ee_(2)O_(4)ferrites are successfully synthesized at a low temperature(900℃)by using the solid state reaction method.The effects of the additives on the phase formation,magnetic and dielectric properties as well as the structural and gyromagnetic properties are investigated.The x-ray diffraction(XRD)results indicate that the added Bi_(2)O_(3)-CuO can lower the synthesis temperature significantly without the appearing of the second phase.The scanning electron microscope(SEM)images confirm that Bi_(2)O_(3)is an important factor that determines the sintering behaviors,while CuO affects the grain size and densification.With CuO content x=0.4 or 0.6,the sample shows high saturation magnetization,low coercivity,high real part of magnetic permeability,dielectric permittivity,and small ferromagnetic resonance linewidth(ΔH).The NiCuZn ferrites are a promising new generation of high-performance microwave devices,such as phase shifters and isolators.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.
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.
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Project supported by the National Natural Science Foundation of China (Grant No.50572032)
文摘Additive Ba（N3）2 as a source of nitrogen is heavily doped into the graphite-Fe-based alloy system to grow nitrogendoped diamond crystals under a relatively high pressure （about 6.0 GPa） by employing the temperature gradient method. Gem-grade diamond crystal with a size of around 5 mm and a nitrogen concentration of about 1173 ppm is successfully synthesised for the first time under high pressure and high temperature in a China-type cubic anvil highpressure apparatus. The growth habit of diamond crystal under the environment with high degree of nitrogen doping is investigated. It is found that the morphologies of heavily nitrogen-doped diamond crystals are all of octahedral shape dominated by {111} facets. The effects of temperature and duration on nitrogen concentration and form are explored by infrared absorption spectra. The results indicate that nitrogen impurity is present in diamond predominantly in the dispersed form accompanied by aggregated form, and the aggregated nitrogen concentration in diamond increases with temperature and duration. In addition, it is indicated that nitrogen donors are more easily incorporated into growing crystals at higher temperature. Strains in nitrogen-doped diamond crystal are characterized by micro-Raman spectroscopy. Measurement results demonstrate that the undoped diamond crystals exhibit the compressive stress, whereas diamond crystals heavily doped with the addition of Ba（N3）2 display the tensile stress.
文摘Nitroalkanes react smoothly with CF_3CCl_2COCH=CHPh via Michael addition in the presence of inorganic bases such as KF/Al2O3 or K2CO3, giving fluorinecontaining γ-nitro ketones in good yields.
基金supported by the National Nature Science Foundation of China(Nos.21576195 and 21776207)
文摘In this study, we applied a novel, mild, and convenient synthetic method involving the oxidative cyclization of 1-(pyrazin-2-yl)guanidine derivatives to produce [1,2,4]triazolo[4,3-a ]pyrazin-3-amines. We optimized the reaction procedure to easily obtain 5-chloro-[1,2,4]triazolo[4,3-a ]pyrazin-3-amine. Various types of halogenated pyrazines can successfully undergo this process. We synthesized a series of 1-(pyrazin-2-yl)guanidines and [1,2,4]triazolo[4,3-a ]pyrazin-3-amines, and then elucidated their structures based on their ~1H-NMR, ^(13)C-NMR, ESI-HRMS, and nuclear Overhauser effect spectra.
基金the National Natural Science Foundation of China(No.51902036,51702138,22075115)Natural Science Foundation of Chongqing Science&Technology Commission(No.cstc2019jcyj-msxm1407)+4 种基金Natural Science Foundation of Chongqing Technology and Business University(No.1952009)the Venture&Innovation Support Program for Chongqing Overseas Returnees(Grant No.CX2018129)the Science and Technology Research Program of Chongqing Municipal Education Commission(Grant No.KJQN201900826 and KJQN201800808)the Innovation Group of New Technologies for Industrial Pollution Control of Chongqing Education Commission(Grant No.CXQT19023)Key Disciplines of Chemical Engineering and Technology in Chongqing Colleges and Universities during the 13th Five Year Plan provided the financial support.
文摘Zinc metal batteries have been considered as a promising candidate for next-generation batteries due to their high safety and low cost.However,their practical applications are severely hampered by the poor cyclability that caused by the undesired dendrite growth of metallic Zn.Herein,Ti_(3)C_(2)T_(x) MXene was first used as electrolyte additive to facilitate the uniform Zn deposition by controlling the nucleation and growth process of Zn.Such MXene additives can not only be absorbed on Zn foil to induce uniform initial Zn deposition via providing abundant zincophilic-O groups and subsequently participate in the formation of robust solid-electrolyte interface film,but also accelerate ion transportation by reducing the Zn^(2+) concentration gradient at the electrode/electrolyte interface.Consequently,MXene-containing electrolyte realizes dendrite-free Zn plating/striping with high Coulombic efficiency(99.7%)and superior reversibility(stably up to 1180 cycles).When applied in full cell,the Zn-V_(2)O_(5)cell also delivers significantly improved cycling performances.This work provides a facile yet effective method for developing reversible zinc metal batteries.
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.
文摘Nanocrystalline TiO2 was prepared by high frequency plasma chemical vapor deposition (HF-PCVD). The effects of additive AlCl3 on crystal phase, particle size and microstructurai parameters of TiO2 nanocrystallites were investigated by X-ray diffraction(XRD) and transmission electron microscopy (TEM). The nanocrystallites obtained experimentally are mixture of anatase and rutile, the uniform diameters of particles are about 30 nm. The phase transformation from anatase to rutile was accelerated by AlCl3, and rutile content is increased from 26.7 wt pct to 53.6 wt pct with increasing of addition of AlCl3 from 0.0 wt pct to 5.0 wt pct. The particle size is reduced and the size distribution becomes very narrow. The crystal lattice constants have the trend to decrease, and celi volumes appear as shrinkable.
基金This work was supported by the National Key R&D Program of China(2017YFA0204403)the Major Program of the National Natural Science Foundation of China(51590892)+3 种基金the General Research Fund Research Grants Council(Hong Kong)(CityU 11209918)the Hong Kong Collaborative Research Fund Scheme(C4026-17W)the Hong Kong Theme-based Research Scheme(T13-402/17-N)the Shenzhen-Hong Kong cooperation zone for technology and innovation(HZQB-KCZYB-2020030).
文摘Over the past 30 years,additive manufacturing(AM)has developed rapidly and has demonstrated great potential in biomedical applications.AM is a materials-oriented manufacturing technology,since the solidification mechanism,architecture resolution,post-treatment process,and functional application are based on the materials to be printed.However,3D printable materials are still quite limited for the fabrication of bioimplants.In this work.2D/3D AM materials for bioimplants are reviewed.Furthermore,inspired by Tai Chi,a simple yet novel soft/rigid hybrid 4D AM concept is advanced to develop complex and dynamic biological structures in the human body based on 4D printing hybrid ceramic precursor/ceramic materials that were previously developed by our group.With the development of multi-material printing technology,the development of bioimplants and soft/rigid hybrid biological structures with 2D/3D/4D AM materials can be anticipated.
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 National Key Research and Development Program of China(Grant No.2018YFE0115500)the National Natural Science Foundation of China(Grant Nos.52003256 and 51902037)the Natural Science Foundation of Shanxi Province,China(Grant No.201901D211259)。
文摘With a series of 1.0 wt%Bi_(2)O_(3)-x wt%CuO(x=0.0,0.2,0.4,0.6,and 0.8)serving as sintering additives,Ni_(0.23)Cu_(0.32)Zn_(0.45)Ee_(2)O_(4)ferrites are successfully synthesized at a low temperature(900℃)by using the solid state reaction method.The effects of the additives on the phase formation,magnetic and dielectric properties as well as the structural and gyromagnetic properties are investigated.The x-ray diffraction(XRD)results indicate that the added Bi_(2)O_(3)-CuO can lower the synthesis temperature significantly without the appearing of the second phase.The scanning electron microscope(SEM)images confirm that Bi_(2)O_(3)is an important factor that determines the sintering behaviors,while CuO affects the grain size and densification.With CuO content x=0.4 or 0.6,the sample shows high saturation magnetization,low coercivity,high real part of magnetic permeability,dielectric permittivity,and small ferromagnetic resonance linewidth(ΔH).The NiCuZn ferrites are a promising new generation of high-performance microwave devices,such as phase shifters and isolators.
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.
