Conical spin order, where the spin components along the conical axis form magnetization while the spiral parts induce ferroelectric polarization, possesses multiferroicity with inherent magnetoelectric coupling. A Mon...Conical spin order, where the spin components along the conical axis form magnetization while the spiral parts induce ferroelectric polarization, possesses multiferroicity with inherent magnetoelectric coupling. A Monte Carlo simulation performed using a classical Heisenberg spinel （AB2O4） model reveals a multiple conical spin order, i.e., three modulations with different cone angles and wavelengths on A sites and two alternate B sites. The spin order not only exists as the ground state but also survives locally stably in a larger parameter region. The whole existence range can be effectively expanded by anisotropy to cover the cases of CoCr2O4 and MnCr2O4. The multiple conical spin order is well maintained and finely tuned by frustration and anisotropy over the whole existence range, and the magnetic and ferroelectric properties are influenced correspondingly.展开更多
Electron microscopic investigation on low carbon steel strips produced by the CSP process has been carried out. Large number of oxide dispersive precipitates have been observed in the ferrite matrix of the steel strip...Electron microscopic investigation on low carbon steel strips produced by the CSP process has been carried out. Large number of oxide dispersive precipitates have been observed in the ferrite matrix of the steel strips. Dimension of them is about 10~20 nm. Electron diffraction study showed that the structure of these precipitates consists with cubic system spinel structure. Their lattice parameter is about 0.83 nm. The results implied that they should be complex oxides of Fe, Al et al. Small sulfide particles with 100-300 nm in size have also been observed. Remarkable strengthening and grain refinement effects can be obtained by the precipitations. The oxygen and sulfur in steels could play beneficial role under certain conditions.展开更多
The high cost,scarcity,and poor stability of precious-metal-based catalysts have hindered their extensive application in energy conversion and storage.This stimulates the search for earth-abundant alternatives to repl...The high cost,scarcity,and poor stability of precious-metal-based catalysts have hindered their extensive application in energy conversion and storage.This stimulates the search for earth-abundant alternatives to replace noble metal electrocatalysts.Hence,in this study,we investigate a novel and low-cost bifunctional electrocatalyst consisting of ZnCoMnO_(4) anchored on nitrogen-doped graphene oxide(ZnCoMnO_(4)/N-rGO).Benefiting from the strong Co-N interaction in ZnCoMnO_(4) and the coupled conductive N-rGO,the catalysts exhibit high electrocatalytic activity.Moreover,density functional theory calculations support the dominant role of the strong Co-N electronic interaction,which leads to ZnCoMnO_(4)/N-rGO having more favorable binding energies with O2 and H_(2) O,resulting in fast reaction kinetics.The obtained ZnCoMnO_(4)/N-rGO electrocatalyst exhibits superb bifunctional activity,with a half-wave potential of 0.83 V for the oxygen reduction reaction and a low onset potential of 1.57 V for the oxygen evolution reaction in 0.1 M KOH solution.Furthermore,a Zn-air battery driven by the ZnCoMnO_(4)/N-rGO catalyst shows remarkable discharge/charge performance,with a power density of 138.52 mW cm^(-2) and longterm cycling stability for 48 h.This work provides a promising multifunctional electrocatalyst based on non-noble metals for the storage and conversion of renewable energy.展开更多
The effect of an external magnetic field on the structural and magnetic properties of bond frustrated ZnCr2 Se4 at low temperatures is investigated using magnetization, dielectric constants and thermal conductivity ex...The effect of an external magnetic field on the structural and magnetic properties of bond frustrated ZnCr2 Se4 at low temperatures is investigated using magnetization, dielectric constants and thermal conductivity experiments. With an increase in the magnetic field H, the antiferromagnetic transition temperature TN is observed to shift progressively toward lower temperatures. The corresponding high temperature cubic （Fd3m） to low temperature tetragonal （I41amd） structural transition is tuned simultaneously due to the inherent strong spin-lattice coupling. In the antiferromagnetic phase, an anomaly at Hc2 defined as a steep downward peak in the derivative of the M-H curve is dearly drawn. It is found that TN versus H and Hc2 versus T exhibit a consistent tendency, indicative of a field-induced tetragonal （I41amd） to cubic （Fd3m） structural transition. The transition is further substantiated by the field-dependent dielectric constant and thermal conductivity measurements. We modify the T-H phase diagram, highlighting the coexistence of the paramagnetic state and ferromagnetic clusters between 100K and TN.展开更多
MgxNi1-xFe_(2)O_(4)(x=0,0.25,0.5,0.75,1)spinel ferrite material was analyzed to determine its magnetic properties and structure.X-ray diffraction(XRD),Mössbauer spectroscopy,and vibrating sample magnetometer(VSM)...MgxNi1-xFe_(2)O_(4)(x=0,0.25,0.5,0.75,1)spinel ferrite material was analyzed to determine its magnetic properties and structure.X-ray diffraction(XRD),Mössbauer spectroscopy,and vibrating sample magnetometer(VSM)characterization were performed on the samples prepared using the sol-gel method.The results from XRD confirmed the existence of the single-phase cubic spinel structures Fd3m,as well as the evolution of the crystalline size(D),the lattice parameter(a)and cell volume in compounds.The Mössbauer spectra showed the distribution of cations and changes in the magnetic properties of the sample.VSM measurement revealed that the samples were room-temperature ferromagnetic.Moreover,the saturation magnetization(Ms)of the samples changed with the Mg^(2+)ion content x,and a maximum occured at x=0.5.Doping with Mg^(2+)ions increased the transfer of Ni^(2+)ions to tetrahedral sites,thus increasing the magnetic moment difference between tetrahedral(A)and octahedral(B)sites.Specifically,doping NiFe_(2)O_(4) with Mg^(2+)ions can enhance its magnetic properties and enhance its saturation magnetization.展开更多
Al-3Cu-Mg alloy was fabricated by the powder metallurgy(P/M) processes. Air-atomized powders of each alloying element were blended with various Mg contents(0.5%, 1.5%, and 2.5%, mass fraction). The compaction pressure...Al-3Cu-Mg alloy was fabricated by the powder metallurgy(P/M) processes. Air-atomized powders of each alloying element were blended with various Mg contents(0.5%, 1.5%, and 2.5%, mass fraction). The compaction pressure was selected to achieve the elastic deformation, local plastic deformation, and plastic deformation of powders, respectively, and the sintering temperatures for each composition were determined, where the liquid phase sintering of Cu is dominant. The microstructural analysis of sintered materials was performed using optical microscope(OM) and scanning electron microscope(SEM) to investigate the sintering behaviors and fracture characteristics. The transverse rupture strength(TRS) of sintered materials decreased with greater Mg content(Al-3Cu-2.5Mg). However, Al-3Cu-0.5Mg alloy exhibited moderate TRS but higher specific strength than Al-3Cu without Mg addition.展开更多
Spinel LiMn_(2)O_(4)has been considered to be the most promising alternative cathode material for the new generation of lithium-ion batteries in terms of its low cost,non-toxicity and easy manufacture.The spinel lithi...Spinel LiMn_(2)O_(4)has been considered to be the most promising alternative cathode material for the new generation of lithium-ion batteries in terms of its low cost,non-toxicity and easy manufacture.The spinel lithium manganese mixed oxides were prepared from lithium nitrate,manganese nitrate and citric acid by a sol-gel method and were characterized by thermogravimetric analysis,X-ray diffraction,cyclic voltammetry and constant current charging-discharging technique.The different sintering temperatures for different time have strong influence on the structure,initial discharge capacity and cycling performance of the lithium manganese oxide.It shows that the lithium manganese oxides sintered at 700℃for 10 h have a single spinel structure and better electrochemical properties.The initial discharging capacity can be up to 125.9 mAh·g^(-1),even after six cycles,it still retains 109.1 mAh·g^(-1).展开更多
The micro-single crystal material spinel LiMn2-xAlxO4 was prepared by a sol-gel procedure and modified by alumina; the electrochemical measurements show that the performances and characteristics of modified LiMn2-xAlx...The micro-single crystal material spinel LiMn2-xAlxO4 was prepared by a sol-gel procedure and modified by alumina; the electrochemical measurements show that the performances and characteristics of modified LiMn2-xAlxO4 electrode material are better than those of LiMn204. Hence, the modified LiMn2- AlxO4 is a good cathode material for lithium batteries. This can be explained that the size of the modified particle is larger than that of unmodified material, so electrons can be easily transported between the particles.展开更多
This paper studies the structure and electronic properties of Li4Ti5O12, as anode material for lithium ion batteries, from first principles calculations. The results suggest that there are two kinds of unit cell of Li...This paper studies the structure and electronic properties of Li4Ti5O12, as anode material for lithium ion batteries, from first principles calculations. The results suggest that there are two kinds of unit cell of Li4Ti5O12： n-type and p-type. The two unit cells have different structures and electronic properties： the n-type with two 16d site Li ions is metallic by electron, while the p-type with three 16d Li ions is metallic by hole. However, the Li4Ti5O12 is an insulator. It is very interesting that one n-type cell and two p-type cells constitute one Li4Ti5O12 supercell which is insulating. The results show that the intercalation potential obtained with a p-type unit cell with one additional electron is quite close to the experimental value of 1.5 V.展开更多
Co-precipitation is an important issue in chemical analysis, where it is often undesirable, but in some cases, it can be exploited. The Zn0.5Mn0.5−xLi2xFe2O4 nanomaterials (x = 0.0, 0.1, 0.2, 0.3 and 0.4) wa...Co-precipitation is an important issue in chemical analysis, where it is often undesirable, but in some cases, it can be exploited. The Zn0.5Mn0.5−xLi2xFe2O4 nanomaterials (x = 0.0, 0.1, 0.2, 0.3 and 0.4) was afforded by utilizing co-precipitation method. The structural and optical characteristics were analyzed for the samples employing X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR) and Ultraviolet-visible spectrophotometer (UV-Vis). XRD revealed that the structure of certain nanoparticles is a cubic spinel with space group (Fd-3m) and crystallite size in the scale 124 - 150 nm. Lattice parameter was determined to increments with Li+1 and that may occur due to the larger ionic radius of the Li1+ ion. FTIR spectroscopy confirmed the form of spinel ferrite and explicated the properties of absorption bands approximately 593, 1111, 1385, 1640, 2922 and 3430. The energy band gap was estimated for all samples with diverse ratios and was observed in the range of 2.58 - 2.52 eV.展开更多
High entropy oxides(HEOs),as a new type of single-phase multielement solid solution materials,have shown many attractive features and promising application prospect in the energy storage fleld.Herein,six-element HEOs(...High entropy oxides(HEOs),as a new type of single-phase multielement solid solution materials,have shown many attractive features and promising application prospect in the energy storage fleld.Herein,six-element HEOs(CoNiZnFeMnLi)_(3)O_(4) and(CoNiZnCrMnLi)_(3)O_(4) with spinel structure are successfully prepared by con-ventional solid-phase method and present outstanding lithium storage performances due to the synergy effect of various electrochemically active elements and the entropy stabilization.By contrast,(CoNiZnFeMnLi)_(3)O_(4) delivers higher initial discharge specific capacity of 1104.3 mAh·g^(−1),better cycle stability(84%capacity retention after 100 cycles at 100 mA·g^(−1)) and rate performance(293 mAh·g^(−1)at 2000 mA·g^(−1))in the half-cell.Moreover,the full-cell assembled with(CoNiZnFeMnLi)_(3)O_(4) and LiCoO_(2)provides a reversible specific capacity of 260.2 mAh·g^(−1)after 100 cycles at 500 mA·g^(−1).Ex situ X-ray diffraction reveals the electrochemical reaction mechanism of HEOs(CoNiZnFeMnLi)_(3)O_(4),and the amorphous phase and the large amount of oxygen vacancies were obtained after the initial discharge process,which are responsible for the excellent cycle and rate performance.This research puts forward fresh insights for the development of advanced energy storage materials for high-performance batteries.展开更多
Mn2+and the trivalent europium(Eu3+)-doped MgGa2O4 ceramics are characterized using a multi-experimental approach.The formation of spinel-structured ceramics is ascertained from X-ray diffraction(XRD)analysis.Morpholo...Mn2+and the trivalent europium(Eu3+)-doped MgGa2O4 ceramics are characterized using a multi-experimental approach.The formation of spinel-structured ceramics is ascertained from X-ray diffraction(XRD)analysis.Morphology investigations with transmission electron microscopy(TEM)show irregularly shaped grains and grain boundaries with a homogeneous distribution of Eu3+ions.The inability of Eu activator to penetrate the bulk of ceramic grains is inferred from positron annihilation lifetime spectroscopy data.The Eu doping is shown to enhance the positron trapping rate due to the occupancy of vacancy-type defects at ceramic grains by Eu3+ions.Both Mn2+and Eu3+doped samples show a broad multi-color luminescence in 350–650 nm range under 240 nm and 270–300 nm excitations.Blue emission is concluded to originate from host defects,whereas green emission and narrow lines in the red region of the spectrum are attributed to Mn2+and Eu3+ions,respectively.High asymmetry around Eu3+ions can be concluded from the photoluminescence and positron annihilation lifetime spectra analysis.展开更多
Chromium slag usually contains various heavy metals,making its safe treatment difficult.Glassceramic sintering has been applied to resolve this issue and emerged as an effective method for metal immobilization by inco...Chromium slag usually contains various heavy metals,making its safe treatment difficult.Glassceramic sintering has been applied to resolve this issue and emerged as an effective method for metal immobilization by incorporating heavy metals into stable crystal structures.Currently,there is limited knowledge about the reaction pathways adopted by multiple heavy metals and the co-stabilization functions of the crystal structure.To study the Cu/Cr co-stabilization mechanisms during thermal treatment,a simulated system was prepared using a mixture with a molar ratio of Al_(2)O_(3):Fe_(2)O_(3):Cr_(2)O_(3):CuO=1:1:1:3.The samples were sintered at temperatures 600–1300℃ followed by intensive analysis of phase constitutions and microstructure development.A spinel phase(CuFe_(x)Al_(y)Cr_(2–x–y)O_(4))started to generate at 700℃ and the incorporation of Cu/Cr into the spinel largely complete at 900℃,although the spinel peak intensity continued increasing slightly at temperatures above 900℃.Fe_(2)O_(3)/Cr_(2)O_(3) was more easily incorporated into the spinel at lower temperatures,while more Al_(2)O_(3) was gradually incorporated into the spinel at higher temperatures.Additionally,sintered sample microstructures became more condensed and smoother with increased sintering temperature.Cu/Cr leachability substantially decreased after Cu/Cr incorporation into the spinel phase at elevated temperatures.At 600℃,the leached ratios for Cu and Cr were 6.28%and 0.65%,respectively.When sintering temperature was increased to 1300℃,the leached ratios for all metal components in the system were below 0.2%.This study proposes a sustainable method for managing Cu/Cr co-exist slag at reasonable temperatures.展开更多
文摘Conical spin order, where the spin components along the conical axis form magnetization while the spiral parts induce ferroelectric polarization, possesses multiferroicity with inherent magnetoelectric coupling. A Monte Carlo simulation performed using a classical Heisenberg spinel （AB2O4） model reveals a multiple conical spin order, i.e., three modulations with different cone angles and wavelengths on A sites and two alternate B sites. The spin order not only exists as the ground state but also survives locally stably in a larger parameter region. The whole existence range can be effectively expanded by anisotropy to cover the cases of CoCr2O4 and MnCr2O4. The multiple conical spin order is well maintained and finely tuned by frustration and anisotropy over the whole existence range, and the magnetic and ferroelectric properties are influenced correspondingly.
文摘Electron microscopic investigation on low carbon steel strips produced by the CSP process has been carried out. Large number of oxide dispersive precipitates have been observed in the ferrite matrix of the steel strips. Dimension of them is about 10~20 nm. Electron diffraction study showed that the structure of these precipitates consists with cubic system spinel structure. Their lattice parameter is about 0.83 nm. The results implied that they should be complex oxides of Fe, Al et al. Small sulfide particles with 100-300 nm in size have also been observed. Remarkable strengthening and grain refinement effects can be obtained by the precipitations. The oxygen and sulfur in steels could play beneficial role under certain conditions.
基金financially supported by the National Natural Science Foundation of China for Youths(No.21601067,21701057)the China Postdoctoral Science Foundation(No.2020 M673037)a project funded by the Priority Academic Program Development of the Jiangsu Higher Education Institutions。
文摘The high cost,scarcity,and poor stability of precious-metal-based catalysts have hindered their extensive application in energy conversion and storage.This stimulates the search for earth-abundant alternatives to replace noble metal electrocatalysts.Hence,in this study,we investigate a novel and low-cost bifunctional electrocatalyst consisting of ZnCoMnO_(4) anchored on nitrogen-doped graphene oxide(ZnCoMnO_(4)/N-rGO).Benefiting from the strong Co-N interaction in ZnCoMnO_(4) and the coupled conductive N-rGO,the catalysts exhibit high electrocatalytic activity.Moreover,density functional theory calculations support the dominant role of the strong Co-N electronic interaction,which leads to ZnCoMnO_(4)/N-rGO having more favorable binding energies with O2 and H_(2) O,resulting in fast reaction kinetics.The obtained ZnCoMnO_(4)/N-rGO electrocatalyst exhibits superb bifunctional activity,with a half-wave potential of 0.83 V for the oxygen reduction reaction and a low onset potential of 1.57 V for the oxygen evolution reaction in 0.1 M KOH solution.Furthermore,a Zn-air battery driven by the ZnCoMnO_(4)/N-rGO catalyst shows remarkable discharge/charge performance,with a power density of 138.52 mW cm^(-2) and longterm cycling stability for 48 h.This work provides a promising multifunctional electrocatalyst based on non-noble metals for the storage and conversion of renewable energy.
基金Supported by the National Basic Research Program of China under Grant No 2011CBA00111the National Natural Science Foundation of China under Grant No U1332143
文摘The effect of an external magnetic field on the structural and magnetic properties of bond frustrated ZnCr2 Se4 at low temperatures is investigated using magnetization, dielectric constants and thermal conductivity experiments. With an increase in the magnetic field H, the antiferromagnetic transition temperature TN is observed to shift progressively toward lower temperatures. The corresponding high temperature cubic （Fd3m） to low temperature tetragonal （I41amd） structural transition is tuned simultaneously due to the inherent strong spin-lattice coupling. In the antiferromagnetic phase, an anomaly at Hc2 defined as a steep downward peak in the derivative of the M-H curve is dearly drawn. It is found that TN versus H and Hc2 versus T exhibit a consistent tendency, indicative of a field-induced tetragonal （I41amd） to cubic （Fd3m） structural transition. The transition is further substantiated by the field-dependent dielectric constant and thermal conductivity measurements. We modify the T-H phase diagram, highlighting the coexistence of the paramagnetic state and ferromagnetic clusters between 100K and TN.
基金Project supported by the National Natural Science Foundation of China (Grant No.11447231)the National Undergraduate Innovation and Entrepreneurship Training Program Support Projects of China+2 种基金the Natural Science Foundation of Hunan Province,China (Grant No.2020JJ4517)the Research Foundation of the Education Bureau of Hunan Province,China (Grant Nos.19A434,19A433,and 19C1621)the Opening Project of the Cooperative Innovation Center for Nuclear Fuel Cycle Technology and Equipment,University of South China (Grant Nos.2019KFY10 and 2019KFY09)。
文摘MgxNi1-xFe_(2)O_(4)(x=0,0.25,0.5,0.75,1)spinel ferrite material was analyzed to determine its magnetic properties and structure.X-ray diffraction(XRD),Mössbauer spectroscopy,and vibrating sample magnetometer(VSM)characterization were performed on the samples prepared using the sol-gel method.The results from XRD confirmed the existence of the single-phase cubic spinel structures Fd3m,as well as the evolution of the crystalline size(D),the lattice parameter(a)and cell volume in compounds.The Mössbauer spectra showed the distribution of cations and changes in the magnetic properties of the sample.VSM measurement revealed that the samples were room-temperature ferromagnetic.Moreover,the saturation magnetization(Ms)of the samples changed with the Mg^(2+)ion content x,and a maximum occured at x=0.5.Doping with Mg^(2+)ions increased the transfer of Ni^(2+)ions to tetrahedral sites,thus increasing the magnetic moment difference between tetrahedral(A)and octahedral(B)sites.Specifically,doping NiFe_(2)O_(4) with Mg^(2+)ions can enhance its magnetic properties and enhance its saturation magnetization.
基金Project(NRF-2012R1A1A1012983) supported by the Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Science,ICT&Future PlanningProject supported by the New Faculty Research Fund of Ajou University,Korea
文摘Al-3Cu-Mg alloy was fabricated by the powder metallurgy(P/M) processes. Air-atomized powders of each alloying element were blended with various Mg contents(0.5%, 1.5%, and 2.5%, mass fraction). The compaction pressure was selected to achieve the elastic deformation, local plastic deformation, and plastic deformation of powders, respectively, and the sintering temperatures for each composition were determined, where the liquid phase sintering of Cu is dominant. The microstructural analysis of sintered materials was performed using optical microscope(OM) and scanning electron microscope(SEM) to investigate the sintering behaviors and fracture characteristics. The transverse rupture strength(TRS) of sintered materials decreased with greater Mg content(Al-3Cu-2.5Mg). However, Al-3Cu-0.5Mg alloy exhibited moderate TRS but higher specific strength than Al-3Cu without Mg addition.
基金This work was financially supported by the Program of YET and NCET and the Specialized Research Fund for the Doctoral Program of Higher Education of MOE of China(No.20050699011).
文摘Spinel LiMn_(2)O_(4)has been considered to be the most promising alternative cathode material for the new generation of lithium-ion batteries in terms of its low cost,non-toxicity and easy manufacture.The spinel lithium manganese mixed oxides were prepared from lithium nitrate,manganese nitrate and citric acid by a sol-gel method and were characterized by thermogravimetric analysis,X-ray diffraction,cyclic voltammetry and constant current charging-discharging technique.The different sintering temperatures for different time have strong influence on the structure,initial discharge capacity and cycling performance of the lithium manganese oxide.It shows that the lithium manganese oxides sintered at 700℃for 10 h have a single spinel structure and better electrochemical properties.The initial discharging capacity can be up to 125.9 mAh·g^(-1),even after six cycles,it still retains 109.1 mAh·g^(-1).
基金the Science and Research Reward Fund Program of Shandong Excellent Young Scientist of China (No. 2007BS04044)
文摘The micro-single crystal material spinel LiMn2-xAlxO4 was prepared by a sol-gel procedure and modified by alumina; the electrochemical measurements show that the performances and characteristics of modified LiMn2-xAlxO4 electrode material are better than those of LiMn204. Hence, the modified LiMn2- AlxO4 is a good cathode material for lithium batteries. This can be explained that the size of the modified particle is larger than that of unmodified material, so electrons can be easily transported between the particles.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10604023 and 50802089)Science Foundation of Department of Education of Jiangxi Province (Grant No 2007-121)+1 种基金supported by Qianjiang Talent Project(Grant No 2007R10028)Natural Science Foundation of Zhejiang Province (Grant No Y407188)
文摘This paper studies the structure and electronic properties of Li4Ti5O12, as anode material for lithium ion batteries, from first principles calculations. The results suggest that there are two kinds of unit cell of Li4Ti5O12： n-type and p-type. The two unit cells have different structures and electronic properties： the n-type with two 16d site Li ions is metallic by electron, while the p-type with three 16d Li ions is metallic by hole. However, the Li4Ti5O12 is an insulator. It is very interesting that one n-type cell and two p-type cells constitute one Li4Ti5O12 supercell which is insulating. The results show that the intercalation potential obtained with a p-type unit cell with one additional electron is quite close to the experimental value of 1.5 V.
文摘Co-precipitation is an important issue in chemical analysis, where it is often undesirable, but in some cases, it can be exploited. The Zn0.5Mn0.5−xLi2xFe2O4 nanomaterials (x = 0.0, 0.1, 0.2, 0.3 and 0.4) was afforded by utilizing co-precipitation method. The structural and optical characteristics were analyzed for the samples employing X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR) and Ultraviolet-visible spectrophotometer (UV-Vis). XRD revealed that the structure of certain nanoparticles is a cubic spinel with space group (Fd-3m) and crystallite size in the scale 124 - 150 nm. Lattice parameter was determined to increments with Li+1 and that may occur due to the larger ionic radius of the Li1+ ion. FTIR spectroscopy confirmed the form of spinel ferrite and explicated the properties of absorption bands approximately 593, 1111, 1385, 1640, 2922 and 3430. The energy band gap was estimated for all samples with diverse ratios and was observed in the range of 2.58 - 2.52 eV.
基金the National Natural Science Foundation of China(Nos.51902046,51871046,52071073,51771046 and 51971055)Natural Science Foundation of Hebei Province(Nos.E2019501097,E2018501091 and E2020501004)+1 种基金the Science and Technology Project of Hebei Province(No.15271302D)Funds for the Central Universities(N2123032)。
文摘High entropy oxides(HEOs),as a new type of single-phase multielement solid solution materials,have shown many attractive features and promising application prospect in the energy storage fleld.Herein,six-element HEOs(CoNiZnFeMnLi)_(3)O_(4) and(CoNiZnCrMnLi)_(3)O_(4) with spinel structure are successfully prepared by con-ventional solid-phase method and present outstanding lithium storage performances due to the synergy effect of various electrochemically active elements and the entropy stabilization.By contrast,(CoNiZnFeMnLi)_(3)O_(4) delivers higher initial discharge specific capacity of 1104.3 mAh·g^(−1),better cycle stability(84%capacity retention after 100 cycles at 100 mA·g^(−1)) and rate performance(293 mAh·g^(−1)at 2000 mA·g^(−1))in the half-cell.Moreover,the full-cell assembled with(CoNiZnFeMnLi)_(3)O_(4) and LiCoO_(2)provides a reversible specific capacity of 260.2 mAh·g^(−1)after 100 cycles at 500 mA·g^(−1).Ex situ X-ray diffraction reveals the electrochemical reaction mechanism of HEOs(CoNiZnFeMnLi)_(3)O_(4),and the amorphous phase and the large amount of oxygen vacancies were obtained after the initial discharge process,which are responsible for the excellent cycle and rate performance.This research puts forward fresh insights for the development of advanced energy storage materials for high-performance batteries.
基金This study is supported by the Ministry of Education and Science of Ukraine under the Young Scientists Program(0117U007189)R.GOLOVCHAK acknowledges the U.S.National Science Foundation(Grant No.DMR-1725188)for the acquisition of PAL spectrometerJ.CEBULSKI acknowledges support from the SAIA for partial support of this research within the National Scholarship Program of the Slovak Republic.
文摘Mn2+and the trivalent europium(Eu3+)-doped MgGa2O4 ceramics are characterized using a multi-experimental approach.The formation of spinel-structured ceramics is ascertained from X-ray diffraction(XRD)analysis.Morphology investigations with transmission electron microscopy(TEM)show irregularly shaped grains and grain boundaries with a homogeneous distribution of Eu3+ions.The inability of Eu activator to penetrate the bulk of ceramic grains is inferred from positron annihilation lifetime spectroscopy data.The Eu doping is shown to enhance the positron trapping rate due to the occupancy of vacancy-type defects at ceramic grains by Eu3+ions.Both Mn2+and Eu3+doped samples show a broad multi-color luminescence in 350–650 nm range under 240 nm and 270–300 nm excitations.Blue emission is concluded to originate from host defects,whereas green emission and narrow lines in the red region of the spectrum are attributed to Mn2+and Eu3+ions,respectively.High asymmetry around Eu3+ions can be concluded from the photoluminescence and positron annihilation lifetime spectra analysis.
基金supported financially by the National Natural Science Foundation of China(Grant No.21707063)the National Key R&D Program of China(Grant No.2018YFC1902904)the Natural Science Foundation of Guangdong Province in China(No.2019A15150-11836)。
文摘Chromium slag usually contains various heavy metals,making its safe treatment difficult.Glassceramic sintering has been applied to resolve this issue and emerged as an effective method for metal immobilization by incorporating heavy metals into stable crystal structures.Currently,there is limited knowledge about the reaction pathways adopted by multiple heavy metals and the co-stabilization functions of the crystal structure.To study the Cu/Cr co-stabilization mechanisms during thermal treatment,a simulated system was prepared using a mixture with a molar ratio of Al_(2)O_(3):Fe_(2)O_(3):Cr_(2)O_(3):CuO=1:1:1:3.The samples were sintered at temperatures 600–1300℃ followed by intensive analysis of phase constitutions and microstructure development.A spinel phase(CuFe_(x)Al_(y)Cr_(2–x–y)O_(4))started to generate at 700℃ and the incorporation of Cu/Cr into the spinel largely complete at 900℃,although the spinel peak intensity continued increasing slightly at temperatures above 900℃.Fe_(2)O_(3)/Cr_(2)O_(3) was more easily incorporated into the spinel at lower temperatures,while more Al_(2)O_(3) was gradually incorporated into the spinel at higher temperatures.Additionally,sintered sample microstructures became more condensed and smoother with increased sintering temperature.Cu/Cr leachability substantially decreased after Cu/Cr incorporation into the spinel phase at elevated temperatures.At 600℃,the leached ratios for Cu and Cr were 6.28%and 0.65%,respectively.When sintering temperature was increased to 1300℃,the leached ratios for all metal components in the system were below 0.2%.This study proposes a sustainable method for managing Cu/Cr co-exist slag at reasonable temperatures.
