Synthetic slag samples of the CaO-SiO2-MgO-A1203-Cr203 system were obtained to clarify the effect of FeO on the formation of spinel phases and Cr distribution. X-ray diffraction （XRD） and scanning electron microsco...Synthetic slag samples of the CaO-SiO2-MgO-A1203-Cr203 system were obtained to clarify the effect of FeO on the formation of spinel phases and Cr distribution. X-ray diffraction （XRD） and scanning electron microscopy （SEM） equipped with energy-dispersive spectroscopy （EDS）, as well as the thermodynamic software FactSage 6.2, were used for sample characterization. The results show that the addition of FeO can decrease the viscosity of molten slag and the precipitation temperatures of melilite and merwinite. The solidus temperature significantly decreases from 1400 to 1250℃ with the increase of FeO content from 0wt% to 6wt%. The addition of FeO could enhance the content of Cr in spinel phases and reduce the content of Cr in soluble minerals, such as merwinite, melilite, and dicalcium silicate. Hence, the addition of FeO is conducive to decreasing Cr leaching.展开更多
We present the temperature-dependent susceptibility and specific heat measurement of spinel ZnV204. The structural transition with orbital ordering and the antiferromagnetic transition with spin ordering were observed...We present the temperature-dependent susceptibility and specific heat measurement of spinel ZnV204. The structural transition with orbital ordering and the antiferromagnetic transition with spin ordering were observed at 50 K and 37 K, respectively. By analysis of the hysteresis behavior between the specific heat curves obtained in warming and cooling processes, the structural transition was confirmed to be the first-order transition, while the antiferromagnetic transition was found to be of the second-order type. At the structural transition, the latent heat and entropy change were calculated from the excess specific heat, and the derivative of pressure with respect to temperature was obtained using the Clausius--Clapayron equation. At the magnetic transition, the width of the critical fluctuation region was obtained to be about 0.5 K by comparing with Gaussian fluctuations. In the critical region, the critical behavior was analyzed by using renormalization-group theory. The critical amplitude ratio A＋/A- = 1.46, which deviates from the 3D Heisenburg model; while the critical exponent a is -0.011, which is close to the 3D XY model. We proposed that these abnormal critical behaviors can be attributed to strong spin-orbital coupling accompanied with the antiferromagnetic transition. Moreover, in the low temperature range （2-5 K）, the Fermi energy, the density of states near the Fermi surface, and the low limit of Debye temperature were estimated to be 2.42 eV, 2.48 eV-1, and 240 K, respectively.展开更多
The introduction of spinel phase to form the layered-spinel structure(LSS)is an effective way to improve the electrochemical performance of Li-and Mn-rich layered oxides(LMR).But is this structure universal for all LM...The introduction of spinel phase to form the layered-spinel structure(LSS)is an effective way to improve the electrochemical performance of Li-and Mn-rich layered oxides(LMR).But is this structure universal for all LMR systems?In this work,different Mn/Ni ratio systems with the LSS are discussed in detail.It is found that,high discharge capacity(200.8 mA h g^(-1) at 1C rate;1C=250 mA h g^(-1))as well as high capacity-retention(94%at 1C rate after 100 cycles)can be achieved by forming the LSS for low-Ni system(Mn/Ni=5.0).However,the capacity retention decreases severely in the high-Ni system(Mn/Ni=3.5,2.6).For example,when the ratio of Mn/Ni is 3.5,the capacity-retention of the layered-spinel sample was only 65.8%,compared to the 83%of the original LMR sample.The Ex-situ XRD,XPS,and HRTEM results demonstrate that the introduction of spinel phase in high-Ni system accelerates the transition and collapse of the crystal structure.This work provides guidance for optimizing the proportions of elements and the design of structures for the LMR.展开更多
Mg-Al spinel is synthesized by using industrial waste-residue and basic magnesium carbonate in the aluminum factory as the main raw materials. The influence of V2O5 and Fe2O3 mineralizers on the structure, cell parame...Mg-Al spinel is synthesized by using industrial waste-residue and basic magnesium carbonate in the aluminum factory as the main raw materials. The influence of V2O5 and Fe2O3 mineralizers on the structure, cell parameters and microscopic morphology of synthesized Mg-Al spinel has been discussed. The Mg-Al spinel is characterized by using XRD, SEM and relevant analytical software, such as Philips plus, Rietveld quantification and so on. The experimental results show that certain amounts of V2O5 and Fe2O3 are beneficial to the formation of Mg-Al spinel, and the optimum addition of V2O5 and Fe2O3 is respectively 2wt% and 3wt%. V2O5 has few effects on cell parameters of Mg-Al spinel; but Fe2O3 can form solid solution with Mg-Al spinel in which Mg-Fe spinel can also dissolve to form continuous solid solution. Therefore, with the increase of Fe2O3 content, the cell parameters of Mg-Al approximately present linear increase.展开更多
Via the solid phase reaction, Mg-Al spinel has been synthesized by using industrial waste slag from aluminum factory, basic magnesium carbonate and a little amount of clay as the main raw materials. The influences of ...Via the solid phase reaction, Mg-Al spinel has been synthesized by using industrial waste slag from aluminum factory, basic magnesium carbonate and a little amount of clay as the main raw materials. The influences of Cr2O3 mineralizer on crystalline structure, micro-morphology and properties of synthesized Mg-Al spinel are discussed. The synthesized product was characterized by using XRD and SEM, and the relative contents of each crystalline phase are calculated by relevant analytical software such as Philips plus, Rietveld quantification and so on. The experimental results show that a certain amount of Cr2O3 is helpful to the formation of Mg-Al spinel, and when the addition of Cr2O3 is 2.0%, Mg-Al spinel in the system exists in the form of solid solution （Mg0.68A10.32）（A10.84Mg0.16）2O4 whose content is the highest reaching 91%. Then the corresponding indexes of each property are as follows： water absorption 3.0%, apparent porosity 9.8%, bulk density 3.36 g·cm^3, and flexural strength 83.32 MPa. Therefore, we can confirm that the optimum addition of Cr2O3 mineralizer is 2.0%.展开更多
Three groups of cylinder specimens(φ10 mm×10 mm)with 20%,30%and 40%(by mass,the same hereinafter)of ZrO2,were prepared using analytically pure MgO,Al2O3 and ZrO2 powders as the starting materials.The specimens w...Three groups of cylinder specimens(φ10 mm×10 mm)with 20%,30%and 40%(by mass,the same hereinafter)of ZrO2,were prepared using analytically pure MgO,Al2O3 and ZrO2 powders as the starting materials.The specimens were fired at 1600℃for 5 h,1700℃for 0 h and 1800℃for 7 h,respectively.The microstructure of the MgO-MgAl2O4-ZrO2 subsystem was studied by FESEM.The results show that(1)in the temperature range of 1600-1700℃,solid phase reactions happen in the MgO-MgAl2O4-ZrO2 subsystem,leaving three phases:periclase,spinel and ZrO2(solid dissolving with Mg2+)co-existing;spinellization affects the densification;(2)the specimen with 40%ZrO2 fired at 1800℃has heterogeneous melting microstructure;some areas form typical ternary eutectic MgO-MgAl2O4-ZrO2 with composition of MgO 35.2%-37.2%,Al2O324.2%-26.6%,and ZrO237.2%-39.8%.展开更多
基金the Chinese Scholarship Council for financial support
文摘Synthetic slag samples of the CaO-SiO2-MgO-A1203-Cr203 system were obtained to clarify the effect of FeO on the formation of spinel phases and Cr distribution. X-ray diffraction （XRD） and scanning electron microscopy （SEM） equipped with energy-dispersive spectroscopy （EDS）, as well as the thermodynamic software FactSage 6.2, were used for sample characterization. The results show that the addition of FeO can decrease the viscosity of molten slag and the precipitation temperatures of melilite and merwinite. The solidus temperature significantly decreases from 1400 to 1250℃ with the increase of FeO content from 0wt% to 6wt%. The addition of FeO could enhance the content of Cr in spinel phases and reduce the content of Cr in soluble minerals, such as merwinite, melilite, and dicalcium silicate. Hence, the addition of FeO is conducive to decreasing Cr leaching.
基金supported by the National Basic Research Program of China(Grant No.2012CB821404)the National Natural Science Foundation of China(Grant Nos.51172166 and 61106005)+1 种基金the National Science Fund for Talent Training in Basic Science,China(Grant No.J1210061)the Doctoral Fund of Ministry of Education of China(Grant No.20110141110007)
文摘We present the temperature-dependent susceptibility and specific heat measurement of spinel ZnV204. The structural transition with orbital ordering and the antiferromagnetic transition with spin ordering were observed at 50 K and 37 K, respectively. By analysis of the hysteresis behavior between the specific heat curves obtained in warming and cooling processes, the structural transition was confirmed to be the first-order transition, while the antiferromagnetic transition was found to be of the second-order type. At the structural transition, the latent heat and entropy change were calculated from the excess specific heat, and the derivative of pressure with respect to temperature was obtained using the Clausius--Clapayron equation. At the magnetic transition, the width of the critical fluctuation region was obtained to be about 0.5 K by comparing with Gaussian fluctuations. In the critical region, the critical behavior was analyzed by using renormalization-group theory. The critical amplitude ratio A＋/A- = 1.46, which deviates from the 3D Heisenburg model; while the critical exponent a is -0.011, which is close to the 3D XY model. We proposed that these abnormal critical behaviors can be attributed to strong spin-orbital coupling accompanied with the antiferromagnetic transition. Moreover, in the low temperature range （2-5 K）, the Fermi energy, the density of states near the Fermi surface, and the low limit of Debye temperature were estimated to be 2.42 eV, 2.48 eV-1, and 240 K, respectively.
基金supported by the National Natural Science Foundation of China (Grant Nos. U20A20145, 21805198, and 21878195)the Distinguished Young Foundation of Sichuan Province (No. 20JCQN0197)+2 种基金the Sichuan Science and Technology Project (No. 2019YFH0149)the Key R&D Project of Sichuan Provincial Department of Science and Technology (No. 2020YFG0471, No. 2020YFG0022)the Sichuan Province Science and Technology Achievement Transfer and Transformation Project (No 21ZHSF0111).
文摘The introduction of spinel phase to form the layered-spinel structure(LSS)is an effective way to improve the electrochemical performance of Li-and Mn-rich layered oxides(LMR).But is this structure universal for all LMR systems?In this work,different Mn/Ni ratio systems with the LSS are discussed in detail.It is found that,high discharge capacity(200.8 mA h g^(-1) at 1C rate;1C=250 mA h g^(-1))as well as high capacity-retention(94%at 1C rate after 100 cycles)can be achieved by forming the LSS for low-Ni system(Mn/Ni=5.0).However,the capacity retention decreases severely in the high-Ni system(Mn/Ni=3.5,2.6).For example,when the ratio of Mn/Ni is 3.5,the capacity-retention of the layered-spinel sample was only 65.8%,compared to the 83%of the original LMR sample.The Ex-situ XRD,XPS,and HRTEM results demonstrate that the introduction of spinel phase in high-Ni system accelerates the transition and collapse of the crystal structure.This work provides guidance for optimizing the proportions of elements and the design of structures for the LMR.
基金Supported by the Development and Reform Commission of Fujian Province and Talent Foundation of Fuzhou University
文摘Mg-Al spinel is synthesized by using industrial waste-residue and basic magnesium carbonate in the aluminum factory as the main raw materials. The influence of V2O5 and Fe2O3 mineralizers on the structure, cell parameters and microscopic morphology of synthesized Mg-Al spinel has been discussed. The Mg-Al spinel is characterized by using XRD, SEM and relevant analytical software, such as Philips plus, Rietveld quantification and so on. The experimental results show that certain amounts of V2O5 and Fe2O3 are beneficial to the formation of Mg-Al spinel, and the optimum addition of V2O5 and Fe2O3 is respectively 2wt% and 3wt%. V2O5 has few effects on cell parameters of Mg-Al spinel; but Fe2O3 can form solid solution with Mg-Al spinel in which Mg-Fe spinel can also dissolve to form continuous solid solution. Therefore, with the increase of Fe2O3 content, the cell parameters of Mg-Al approximately present linear increase.
基金Supported by the Natural Science Foundation of Fujian Province (No. T0750005)Science and Technology Developing Foundation of Fuzhou University (No. 2007-XQ-02)
文摘Via the solid phase reaction, Mg-Al spinel has been synthesized by using industrial waste slag from aluminum factory, basic magnesium carbonate and a little amount of clay as the main raw materials. The influences of Cr2O3 mineralizer on crystalline structure, micro-morphology and properties of synthesized Mg-Al spinel are discussed. The synthesized product was characterized by using XRD and SEM, and the relative contents of each crystalline phase are calculated by relevant analytical software such as Philips plus, Rietveld quantification and so on. The experimental results show that a certain amount of Cr2O3 is helpful to the formation of Mg-Al spinel, and when the addition of Cr2O3 is 2.0%, Mg-Al spinel in the system exists in the form of solid solution （Mg0.68A10.32）（A10.84Mg0.16）2O4 whose content is the highest reaching 91%. Then the corresponding indexes of each property are as follows： water absorption 3.0%, apparent porosity 9.8%, bulk density 3.36 g·cm^3, and flexural strength 83.32 MPa. Therefore, we can confirm that the optimum addition of Cr2O3 mineralizer is 2.0%.
基金The author would like to thank Fu Qiuhua,Zhang Wei and Fan Qingsong for their surport to this work.
文摘Three groups of cylinder specimens(φ10 mm×10 mm)with 20%,30%and 40%(by mass,the same hereinafter)of ZrO2,were prepared using analytically pure MgO,Al2O3 and ZrO2 powders as the starting materials.The specimens were fired at 1600℃for 5 h,1700℃for 0 h and 1800℃for 7 h,respectively.The microstructure of the MgO-MgAl2O4-ZrO2 subsystem was studied by FESEM.The results show that(1)in the temperature range of 1600-1700℃,solid phase reactions happen in the MgO-MgAl2O4-ZrO2 subsystem,leaving three phases:periclase,spinel and ZrO2(solid dissolving with Mg2+)co-existing;spinellization affects the densification;(2)the specimen with 40%ZrO2 fired at 1800℃has heterogeneous melting microstructure;some areas form typical ternary eutectic MgO-MgAl2O4-ZrO2 with composition of MgO 35.2%-37.2%,Al2O324.2%-26.6%,and ZrO237.2%-39.8%.
