Multiple regression equations of liquidus temperature, electrical conductivity and bath density of the Na_3AlF_6-AlF_3-BaC1_2-NaCl system were obtained from experiments by using orthogonal regression method. The exper...Multiple regression equations of liquidus temperature, electrical conductivity and bath density of the Na_3AlF_6-AlF_3-BaC1_2-NaCl system were obtained from experiments by using orthogonal regression method. The experiments were carried out in 100A cell with low melting point electrolyte, the influences of cathodic current density, electrolytic temperature, density differences of bath and liquid aluminum on current efficiency (CE) were studied; when the electrolyte cryolite ratio was 2.5, w(BaC1_2) and w(NaCl) were 48% and 10%, respectively, CE reached 90% and specific energy consumption was 10.97k Wb/kg/kg. Because of the fact that aluminum metal obtained floated on the surface of molten electrolyte, this electrolysis method was then defined as low temperature aluminum floating electrolysis. The results showed that the new low temperature aluminum electrolysis process in the Na_3AlF_6-AlF_3-BaC1_2-NaCl bath system was practical and promising.展开更多
The alumina solubility in the title system within the composition range of KR{m(K3AlF6)/[m(K3AlF6)+m(Na3AlF6)]}10%―50%,a ternary Na_(3)A1F_(6)-K_(3)A1F_(6)-A1F_(3)molten system with 23%―29%(mass fraction)AlF3 was in...The alumina solubility in the title system within the composition range of KR{m(K3AlF6)/[m(K3AlF6)+m(Na3AlF6)]}10%―50%,a ternary Na_(3)A1F_(6)-K_(3)A1F_(6)-A1F_(3)molten system with 23%―29%(mass fraction)AlF3 was investigated by measuring the mass loss of a rotating sintered corundum disc.And the following empirical equation was derived when superheat degree was no more than 60°C:w(Al2O3)sat=A×(T/1000)B,where A=–1.85774+26.754234w(AlF3)–0.3683–0.00783KR2.363+0.010266KR2.3048+0.7902w(AlF3)0.00652,B=112.4625–53.2567w(AlF3)0.4236+5.1079w(AlF3)0.9241+0.01542w(AlF3)1.3540.Considering both higher alumina solubility and not too high superheat de gree are required,alumina solubility of different compositions at not the same temperature but the same superheat degree was studied,which will be more industrial helpful for selecting prospective compositions.The results show that the composition deserved to be further tested in lower temperature cells is 10%―30%KR and 23%―26%(mass fraction)AlF3.展开更多
Full-spectrum phosphor-converted white-light-emitting diodes(pc-WLED)are emerging as a mainstream technology in semiconductor lighting.Nevertheless,high-performance blue phosphor which can be excited efficiently by a ...Full-spectrum phosphor-converted white-light-emitting diodes(pc-WLED)are emerging as a mainstream technology in semiconductor lighting.Nevertheless,high-performance blue phosphor which can be excited efficiently by a 400 nm NUV diode chip is still lacking.Herein,we present a blue-emitting Na_(3)KMg_(7)(PO_(4))6:Eu^(2+)phosphor synthesized by the solid-reaction method.Particularly,we find that the using of Li_(2)CO_(3)as flux can significantly improve the crystal quality and thus the emission efficiency of the phosphor.Meanwhile,the excitation peak of the phosphor shifts from 365 to 400 nm,which is pivotal for efficient NUV(400 nm)diode chip excitation.The practical Eu^(2+)concentration is also enhanced by using Li_(2)CO_(3)as flux,and the absorption efficiency is greatly increased.This phosphor exhibits superior PL thermal stability,namely retains 94%integrated photoluminescence intensity at 150℃of that at 25℃.As a result,the optimized phosphor shows an emission band peaked at 437 nm with a bandwidth of 40 nm and a high external photoluminescence quantum yield of 51.7%.Finally,a pc-WLED was fabricated by using NKMPO:Eu^(2+)blue,Sr_(2)SiO_(4):Eu^(2+)green,CaAlSiN_(3):Eu^(2+)red phosphors,and a 400 nm NUV diode chip.It shows a high color rendering index of R_(a)=96.4 and a correlated color temperature of 4358 K.These results prove that NKMPO:Eu^(2+)is a promising blue phosphor for full-spectrum WLED based on NUV diode chips.展开更多
Na_(2)Ti_(3)O_(7)and Na_(2)Ti_(6)O_(13)are two typical titanate-based sodium-storage materials,featuring the high theoretical capacity and favorable structure stability,respectively.Regulating the ratio of them in the...Na_(2)Ti_(3)O_(7)and Na_(2)Ti_(6)O_(13)are two typical titanate-based sodium-storage materials,featuring the high theoretical capacity and favorable structure stability,respectively.Regulating the ratio of them in the composite material is the key to strengthen its electrochemical characteristics.Herein,based on the high specific surface area and abundant surface functional groups of carbon dots(CDs),sodium titanate precursors containing CDs were in situ prepared by one-step hydrothermal method.After the thermal conversion of the precursors,a composite material(NNTO/C)of Na_(2)Ti_(3)O_(7)and Na_(2)Ti_(6)O_(13)was obtained,containing conductive carbon derived from CDs.The introduc⁃tion of conductive carbon not only adjusts the composition ratio of the mixed phases,but also provides a small charge transfer impedance(Rct,7.48Ω)and a big specific surface area(100.8 m^(2)/g).As a result,NNTO/C composites exhibit better sodium storage behavior while playing the synergistic interaction of mixed phases.When employed as the anode,after 200 cycles at 0.05 A/g,NNTO/C still maintains a specific capacity of 143.8 mA‧h/g.After 400 cycles at 1.00 A/g,the specific capacity remains as high as 108 mA‧h/g.This study suggests an innovative thinking for designing two-phase structures of electrode materials and the greater use of CDs in electrochemical energy storage.展开更多
铁基硫酸盐聚阴离子材料因其成本低廉、电化学性能优异等优点,是钠离子电池大规模应用最有前景的候选材料之一.尽管Na_(2)Fe_(2)(SO_(4))_(3),Na_(2)Fe_(1.5)(SO_(4))_(3),Na_(2.4)Fe_(1.8)(SO_(4))_(3)和Na_(2.4)Fe_(1.8)(SO_(4))_(3)...铁基硫酸盐聚阴离子材料因其成本低廉、电化学性能优异等优点,是钠离子电池大规模应用最有前景的候选材料之一.尽管Na_(2)Fe_(2)(SO_(4))_(3),Na_(2)Fe_(1.5)(SO_(4))_(3),Na_(2.4)Fe_(1.8)(SO_(4))_(3)和Na_(2.4)Fe_(1.8)(SO_(4))_(3)等Na_(6-2x)Fe_(x)(SO_(4))_(3)(NFSO-x 1.5≤x≤2.0)材料在储钠方面取得了巨大成果,但这些NFSO-x的相和结构特性仍存在争议,难以实现具有最佳电化学性能的纯相材料.本文通过实验方法和密度泛函理论计算研究了6个具有不同x的NFSO-x样品,以分析其相和结构特性.结果表明在NFSO-x的1.6≤x≤1.7区域存在纯相,部分Na离子倾向于占据Fe位点以形成更稳定的框架.NFSO-1.7在NFSO-x样品中表现出最佳的电化学性能,具有高的放电容量(0.1 C时为104.5 mAh g^(-1),接近其理论容量105 mAh g^(-1))、出色的倍率性能(30 C时为81.5 mAh g^(-1)),并在10,000次循环中具有超长的循环稳定性,容量保持率为72.4%.本研究有助于阐明铁基硫酸盐聚阴离子材料的相和结构特征,以促进其在大规模储能中的应用.展开更多
基金The project was financially supported by the National Natural Science Foundation of China! (Gmnt No.59574018)China Postdocto
文摘Multiple regression equations of liquidus temperature, electrical conductivity and bath density of the Na_3AlF_6-AlF_3-BaC1_2-NaCl system were obtained from experiments by using orthogonal regression method. The experiments were carried out in 100A cell with low melting point electrolyte, the influences of cathodic current density, electrolytic temperature, density differences of bath and liquid aluminum on current efficiency (CE) were studied; when the electrolyte cryolite ratio was 2.5, w(BaC1_2) and w(NaCl) were 48% and 10%, respectively, CE reached 90% and specific energy consumption was 10.97k Wb/kg/kg. Because of the fact that aluminum metal obtained floated on the surface of molten electrolyte, this electrolysis method was then defined as low temperature aluminum floating electrolysis. The results showed that the new low temperature aluminum electrolysis process in the Na_3AlF_6-AlF_3-BaC1_2-NaCl bath system was practical and promising.
基金Supported by the National Basic Research Program of China(No.2005CB623703)the National High-Tech Research and Development Program of China(No.2008AA030503)
文摘The alumina solubility in the title system within the composition range of KR{m(K3AlF6)/[m(K3AlF6)+m(Na3AlF6)]}10%―50%,a ternary Na_(3)A1F_(6)-K_(3)A1F_(6)-A1F_(3)molten system with 23%―29%(mass fraction)AlF3 was investigated by measuring the mass loss of a rotating sintered corundum disc.And the following empirical equation was derived when superheat degree was no more than 60°C:w(Al2O3)sat=A×(T/1000)B,where A=–1.85774+26.754234w(AlF3)–0.3683–0.00783KR2.363+0.010266KR2.3048+0.7902w(AlF3)0.00652,B=112.4625–53.2567w(AlF3)0.4236+5.1079w(AlF3)0.9241+0.01542w(AlF3)1.3540.Considering both higher alumina solubility and not too high superheat de gree are required,alumina solubility of different compositions at not the same temperature but the same superheat degree was studied,which will be more industrial helpful for selecting prospective compositions.The results show that the composition deserved to be further tested in lower temperature cells is 10%―30%KR and 23%―26%(mass fraction)AlF3.
基金Project supported by the National Natural Science Foundation of China(11974351)。
文摘Full-spectrum phosphor-converted white-light-emitting diodes(pc-WLED)are emerging as a mainstream technology in semiconductor lighting.Nevertheless,high-performance blue phosphor which can be excited efficiently by a 400 nm NUV diode chip is still lacking.Herein,we present a blue-emitting Na_(3)KMg_(7)(PO_(4))6:Eu^(2+)phosphor synthesized by the solid-reaction method.Particularly,we find that the using of Li_(2)CO_(3)as flux can significantly improve the crystal quality and thus the emission efficiency of the phosphor.Meanwhile,the excitation peak of the phosphor shifts from 365 to 400 nm,which is pivotal for efficient NUV(400 nm)diode chip excitation.The practical Eu^(2+)concentration is also enhanced by using Li_(2)CO_(3)as flux,and the absorption efficiency is greatly increased.This phosphor exhibits superior PL thermal stability,namely retains 94%integrated photoluminescence intensity at 150℃of that at 25℃.As a result,the optimized phosphor shows an emission band peaked at 437 nm with a bandwidth of 40 nm and a high external photoluminescence quantum yield of 51.7%.Finally,a pc-WLED was fabricated by using NKMPO:Eu^(2+)blue,Sr_(2)SiO_(4):Eu^(2+)green,CaAlSiN_(3):Eu^(2+)red phosphors,and a 400 nm NUV diode chip.It shows a high color rendering index of R_(a)=96.4 and a correlated color temperature of 4358 K.These results prove that NKMPO:Eu^(2+)is a promising blue phosphor for full-spectrum WLED based on NUV diode chips.
文摘Na_(2)Ti_(3)O_(7)and Na_(2)Ti_(6)O_(13)are two typical titanate-based sodium-storage materials,featuring the high theoretical capacity and favorable structure stability,respectively.Regulating the ratio of them in the composite material is the key to strengthen its electrochemical characteristics.Herein,based on the high specific surface area and abundant surface functional groups of carbon dots(CDs),sodium titanate precursors containing CDs were in situ prepared by one-step hydrothermal method.After the thermal conversion of the precursors,a composite material(NNTO/C)of Na_(2)Ti_(3)O_(7)and Na_(2)Ti_(6)O_(13)was obtained,containing conductive carbon derived from CDs.The introduc⁃tion of conductive carbon not only adjusts the composition ratio of the mixed phases,but also provides a small charge transfer impedance(Rct,7.48Ω)and a big specific surface area(100.8 m^(2)/g).As a result,NNTO/C composites exhibit better sodium storage behavior while playing the synergistic interaction of mixed phases.When employed as the anode,after 200 cycles at 0.05 A/g,NNTO/C still maintains a specific capacity of 143.8 mA‧h/g.After 400 cycles at 1.00 A/g,the specific capacity remains as high as 108 mA‧h/g.This study suggests an innovative thinking for designing two-phase structures of electrode materials and the greater use of CDs in electrochemical energy storage.
基金supported by the National Natural Science Foundation of China(U20A20249,22209125,and 21972108)the Key Research Program of Hubei Province(2020BAA030)。
文摘铁基硫酸盐聚阴离子材料因其成本低廉、电化学性能优异等优点,是钠离子电池大规模应用最有前景的候选材料之一.尽管Na_(2)Fe_(2)(SO_(4))_(3),Na_(2)Fe_(1.5)(SO_(4))_(3),Na_(2.4)Fe_(1.8)(SO_(4))_(3)和Na_(2.4)Fe_(1.8)(SO_(4))_(3)等Na_(6-2x)Fe_(x)(SO_(4))_(3)(NFSO-x 1.5≤x≤2.0)材料在储钠方面取得了巨大成果,但这些NFSO-x的相和结构特性仍存在争议,难以实现具有最佳电化学性能的纯相材料.本文通过实验方法和密度泛函理论计算研究了6个具有不同x的NFSO-x样品,以分析其相和结构特性.结果表明在NFSO-x的1.6≤x≤1.7区域存在纯相,部分Na离子倾向于占据Fe位点以形成更稳定的框架.NFSO-1.7在NFSO-x样品中表现出最佳的电化学性能,具有高的放电容量(0.1 C时为104.5 mAh g^(-1),接近其理论容量105 mAh g^(-1))、出色的倍率性能(30 C时为81.5 mAh g^(-1)),并在10,000次循环中具有超长的循环稳定性,容量保持率为72.4%.本研究有助于阐明铁基硫酸盐聚阴离子材料的相和结构特征,以促进其在大规模储能中的应用.
