Al-substituted barium ferrite powders were synthesized using the sol-gel auto-combustion method according to the molecular formula BaAlxFe12-xO19 （x=0, 0.1, 0.2, 0.3, 0.4, 0.5, 1.0）. Compared with non-substituted ba...Al-substituted barium ferrite powders were synthesized using the sol-gel auto-combustion method according to the molecular formula BaAlxFe12-xO19 （x=0, 0.1, 0.2, 0.3, 0.4, 0.5, 1.0）. Compared with non-substituted barium ferrite annealing at 1000 ℃, the vibrating sample magnetometer （VSM） measurement manifested that the optimum magnetic properties formation temperature of Al-substituted barium ferrite was 1 100 ℃. The data from X-ray diffractometer （XRD） showed that with increasing x, the lattice constants （a and c） decreased as well as the unit-cell volume Vcell. Magnetic measurement of non-substituted and Al-substituted powders annealed from 900 ℃ to 1 200 ℃ exhibited that the maximum magnetization M （10 kOe）, the remanent magnetization Mr and the coercivity Hc depended strongly on the chemical composition of powder as well as the annealing temperature. When annealing at 1 100 ℃, BaAl0.5Fe11.5O19 of high coercivity Hc （6584 Oe） was produced. Meanwhile, M （10 kOe） and Mr were 42.83 emu/g and 25.65 emu/g, respectively.展开更多
This work aimed to research the structure models of amorphous materials. Five amorphous and paracrystalline samples(natural or artificial) were investigated via 29Si/27 Al nuclear magnetic resonance(NMR) and field emi...This work aimed to research the structure models of amorphous materials. Five amorphous and paracrystalline samples(natural or artificial) were investigated via 29Si/27 Al nuclear magnetic resonance(NMR) and field emission scanning electron microscopy/energy dispersive spectroscopy(FE-SEM/EDS). The results of NMR showed the resonances of different specimens:-93.2 ppm,-101.8 ppm,-111.8 ppm for natural pozzolana opal shale(POS). These peaks were assigned to the Q2(2OH), Q3(OH)/Q4(1Al) and Q4 respectively. The results of 27 Al MAS NMR indicated that Al substituted for Si site in tetrahedral existing in the POS, while the Al/Si atomic ratio in opal was low(around 0.04). For the alkali-silicate-hydrate gel, there were at least three resolved signals assigned to Q0 and Q1, respectively. For the fused silica glass powder, there were the primary signals centered about at the range from-107 to-137 ppm, which were assigned to Q4 units. In addition, the peaks at around-98 and-108 ppm were corresponding to Q3(1OH) and Q4 units existing in aerogel silica structure.展开更多
Sodium-ion batteries(SIBs)exhibit significant potential for large-scale energy storage systems due to the abundance and low cost of sodium resources.Triggering lattice oxygen redox(LOR)in P2-type transition metal oxid...Sodium-ion batteries(SIBs)exhibit significant potential for large-scale energy storage systems due to the abundance and low cost of sodium resources.Triggering lattice oxygen redox(LOR)in P2-type transition metal oxides is considered a promising approach to enhance energy density in SIB cathodes,providing high operating potential and substantial capacity.However,irreversible phase transitions associated with LOR,particularly from prisms(P-type stacking)to octahedrons(O-type stacking),lead to severe structural distortions and sluggish Na+diffusion kinetics.In this work,an Al-substitution strategy is proposed to suppress the formation of O-type stacking and instead promote the formation of a beneficial Z phase.The flexible Al-O bonds accommodate asymmetric variations in their occupied states during the sodiation process,mitigating local structural distortions through Al-O bond contraction.Stabilization of the local structure ensures the maintenance of a robust Na+diffusion pathway.As a result,the Al-substituted cathode achieves a low Na+diffusion barrier of 0.47 eV and delivers a capacity of 86 mAh/g even at a high current density of 1 A/g within 1.5–4.5 V,maintaining 62.5%capacity retention over 100 cycles.展开更多
In this work, Al-substituted a-Co（OH）2/GO composites with supercapacitive properties were prepared by chemical co-precipitated method in which cobalt nitrate and aluminum nitrate were used as the raw material, and g...In this work, Al-substituted a-Co（OH）2/GO composites with supercapacitive properties were prepared by chemical co-precipitated method in which cobalt nitrate and aluminum nitrate were used as the raw material, and graphite oxide was employed as carrier. The as-prepared materials were characterized by X-ray diffraction （XRD）, field emission scanning electron microscopy （FESEM） and fourier transform infrared spectroscopy （FF-IR）. Cyclic voltammetry （CV） and galvanostatic charge/discharge measurements showed that the Al-substituted a-Co（OH）2/GO electrode material had excellent electrochemical capacitance. The specific capacitance of 1137 F·g-11 was achieved in 6 mol/L KOH solution at a current density of 1 A·g-1 within a potential range of 0-0.5 V. Moreover, only 12% losses of the initial specific capacitance were found after 500 cycles at a current density of 1 A·g-1.展开更多
基金Project supported by the Science Foundation of Shanghai Municipal Commission of Science and Technology （Grant No.0452nm049）
文摘Al-substituted barium ferrite powders were synthesized using the sol-gel auto-combustion method according to the molecular formula BaAlxFe12-xO19 （x=0, 0.1, 0.2, 0.3, 0.4, 0.5, 1.0）. Compared with non-substituted barium ferrite annealing at 1000 ℃, the vibrating sample magnetometer （VSM） measurement manifested that the optimum magnetic properties formation temperature of Al-substituted barium ferrite was 1 100 ℃. The data from X-ray diffractometer （XRD） showed that with increasing x, the lattice constants （a and c） decreased as well as the unit-cell volume Vcell. Magnetic measurement of non-substituted and Al-substituted powders annealed from 900 ℃ to 1 200 ℃ exhibited that the maximum magnetization M （10 kOe）, the remanent magnetization Mr and the coercivity Hc depended strongly on the chemical composition of powder as well as the annealing temperature. When annealing at 1 100 ℃, BaAl0.5Fe11.5O19 of high coercivity Hc （6584 Oe） was produced. Meanwhile, M （10 kOe） and Mr were 42.83 emu/g and 25.65 emu/g, respectively.
基金Funded by the the National Natural Science Foundation of China(Nos.51278086 and 51578108)the Program for New Century Excellent Talents in University by Ministry of Education of the People’s Republic of China(No.NCET-12-0084)+3 种基金China Petroleum Science and Technology Innovation Fund Research Project(No.2013D-5006-0606)Henan Open and Cooperation Project of Science and Technology(No.142106000023)Liaoning Bai Qian Wan Talents Program(No.2012921073)Dalian Plan Projects of Science and Technology(No.2013A16GX113)
文摘This work aimed to research the structure models of amorphous materials. Five amorphous and paracrystalline samples(natural or artificial) were investigated via 29Si/27 Al nuclear magnetic resonance(NMR) and field emission scanning electron microscopy/energy dispersive spectroscopy(FE-SEM/EDS). The results of NMR showed the resonances of different specimens:-93.2 ppm,-101.8 ppm,-111.8 ppm for natural pozzolana opal shale(POS). These peaks were assigned to the Q2(2OH), Q3(OH)/Q4(1Al) and Q4 respectively. The results of 27 Al MAS NMR indicated that Al substituted for Si site in tetrahedral existing in the POS, while the Al/Si atomic ratio in opal was low(around 0.04). For the alkali-silicate-hydrate gel, there were at least three resolved signals assigned to Q0 and Q1, respectively. For the fused silica glass powder, there were the primary signals centered about at the range from-107 to-137 ppm, which were assigned to Q4 units. In addition, the peaks at around-98 and-108 ppm were corresponding to Q3(1OH) and Q4 units existing in aerogel silica structure.
基金supported by the National Natural Science Foundation of China(Grant No.22209106)This research used beamline 7-BM of the NSLS II,a US DOE Office of Science user facility operated for the DOE Office of Science by Brookhaven National Laboratory under contract No.DE-SC0012704.
文摘Sodium-ion batteries(SIBs)exhibit significant potential for large-scale energy storage systems due to the abundance and low cost of sodium resources.Triggering lattice oxygen redox(LOR)in P2-type transition metal oxides is considered a promising approach to enhance energy density in SIB cathodes,providing high operating potential and substantial capacity.However,irreversible phase transitions associated with LOR,particularly from prisms(P-type stacking)to octahedrons(O-type stacking),lead to severe structural distortions and sluggish Na+diffusion kinetics.In this work,an Al-substitution strategy is proposed to suppress the formation of O-type stacking and instead promote the formation of a beneficial Z phase.The flexible Al-O bonds accommodate asymmetric variations in their occupied states during the sodiation process,mitigating local structural distortions through Al-O bond contraction.Stabilization of the local structure ensures the maintenance of a robust Na+diffusion pathway.As a result,the Al-substituted cathode achieves a low Na+diffusion barrier of 0.47 eV and delivers a capacity of 86 mAh/g even at a high current density of 1 A/g within 1.5–4.5 V,maintaining 62.5%capacity retention over 100 cycles.
基金Project supported by the National Natural Science Foundation of China （Nos. 20963009, 21163017）, Gansu Science and Technology Committee （No. 0803RJA005） and the postgraduate advisor program of Provincial Education Department of Gansu.
文摘In this work, Al-substituted a-Co（OH）2/GO composites with supercapacitive properties were prepared by chemical co-precipitated method in which cobalt nitrate and aluminum nitrate were used as the raw material, and graphite oxide was employed as carrier. The as-prepared materials were characterized by X-ray diffraction （XRD）, field emission scanning electron microscopy （FESEM） and fourier transform infrared spectroscopy （FF-IR）. Cyclic voltammetry （CV） and galvanostatic charge/discharge measurements showed that the Al-substituted a-Co（OH）2/GO electrode material had excellent electrochemical capacitance. The specific capacitance of 1137 F·g-11 was achieved in 6 mol/L KOH solution at a current density of 1 A·g-1 within a potential range of 0-0.5 V. Moreover, only 12% losses of the initial specific capacitance were found after 500 cycles at a current density of 1 A·g-1.
