The microstructural evolution and mechanical properties of Al-18 Si-4 Cu-0.5 Mg alloy modified by the addition of La-Ce rare earth elements through OM,SEM,EPMA and tensile tests were investigated.The results of OM and...The microstructural evolution and mechanical properties of Al-18 Si-4 Cu-0.5 Mg alloy modified by the addition of La-Ce rare earth elements through OM,SEM,EPMA and tensile tests were investigated.The results of OM and SEM analyses indicated that primary Si particles were significantly refined from coarse block-like and irregular polygonal shapes into fine flaky shapes,while eutectic Si particles were modified from coarse and needle-like into fine and rod-or coral-like shapes with increase of La-Ce addition.The alloy exhibited the minimum primary Si particle size and the best mechanical properties with the addition of 0.3 wt.%La-Ce.The average particle size decreased from 61 to 28 μm,the ultimate tensile strength increased from 222 to 242 MPa and the elongation increased from 3.2% to 6.3%.In addition,modification mechanisms and fracture modes were explored by the means of SEM and EPMA.展开更多
The piezoelectric, dielectric, and ferroelectric properties of the （LiCe） co-substituted calcium bismuth niobate （CaBi2Nb209, CBNO） are investigated. The piezoelectric properties of CBNO ceramics are significantly...The piezoelectric, dielectric, and ferroelectric properties of the （LiCe） co-substituted calcium bismuth niobate （CaBi2Nb209, CBNO） are investigated. The piezoelectric properties of CBNO ceramics are significantly enhanced and the dielectric loss tan 5 decreased. This makes poling using （LiCe） co-substitution easier. The ceramics （where represents A-site Ca2＋ vacancies, possess a pure layered structure phase and no other phases can be found. The Cao.ss（LiCe）0.04[]0.04Bi2Nb209 ceramics possess optimal piezoelectric properties, with piezoelectric coefficient （d33） and Curie temperature （Tc） found to be 13.3 pC/N and 960 ℃ respectively. The dielectric and piezoelectric properties of the （LiCe） co-substituted CBNO ceramics exhibit very stable temperature behaviours. This demonstrates that the CBNO ceramics are a promising candidate for ultrahigh temperature applications.展开更多
The piezoelectric,dielectric,and ferroelectric properties of the(LiCe) co-substituted calcium bismuth niobate(CaBi2Nb2O9,CBNO) are investigated.The piezoelectric properties of CBNO ceramics are significantly enhanced ...The piezoelectric,dielectric,and ferroelectric properties of the(LiCe) co-substituted calcium bismuth niobate(CaBi2Nb2O9,CBNO) are investigated.The piezoelectric properties of CBNO ceramics are significantly enhanced and the dielectric loss tan δ decreased.This makes poling using(LiCe) co-substitution easier.The ceramics(where represents A-site Ca2+ vacancies,possess a pure layered structure phase and no other phases can be found.The Ca0.88(LiCe)0.04 0.04Bi2Nb2O9 ceramics possess optimal piezoelectric properties,with piezoelectric coefficient(d 33) and Curie temperature(TC) found to be 13.3 pC/N and 960 C,respectively.The dielectric and piezoelectric properties of the(LiCe) co-substituted CBNO ceramics exhibit very stable temperature behaviours.This demonstrates that the CBNO ceramics are a promising candidate for ultrahigh temperature applications.展开更多
Phase evolution and magnetic properties of (Nd_o.95La_0.05)9.5-11Febal.M_2B10.5. where M=Cr, Ti, Nb, V, Mo, Zr, Hf, Ta, Mn or W, melt spun ribbons have been investigated. Almost all the alloy ribbons. except for(Nd_0....Phase evolution and magnetic properties of (Nd_o.95La_0.05)9.5-11Febal.M_2B10.5. where M=Cr, Ti, Nb, V, Mo, Zr, Hf, Ta, Mn or W, melt spun ribbons have been investigated. Almost all the alloy ribbons. except for(Nd_0.95La_0.05)_9.5Fe_78M_2B_10.5(M=Mo and Mn),consist merely two magnetic phases, namely α-Fe and R_2Fe_14B, which display a better combination of _iH_c and magnetic energy product. Remanence (Br) and coercivity (i_H_c) values in the range of 8.0 to 9.1 kG and 9.5 to 18.9 kOe. respectively, can be achieved. Among compositions studied, the Ti and W-substitutions were found to be most effective in increasing the Br and i_H_c, respectively. For a fixed refractory metal substitution, namely, M=C_r, Ti or Nb, an increase in the total rare earth concentration resulted in nanocomposites of small grain sizes and a high volume fraction of the R_2Fe_14B phase, leading to an increase in the magnetic properties.展开更多
Co-substituted Ni-Zn ferrite was prepared by a chemical codeposition. The electromagnetic properties, zero reflection conditions and simulated reflection losses of the samples were investigated. As a result, it is fou...Co-substituted Ni-Zn ferrite was prepared by a chemical codeposition. The electromagnetic properties, zero reflection conditions and simulated reflection losses of the samples were investigated. As a result, it is found that with Co contents rising, the saturation magnetization (Ms) shows a tendency of decrease, while coercivity (Hc) varies clearly. In addition, Ni-Zn ferrite with different cobalt content can meet zero reflection conditions. And the reflection loss calculation indicates that with the increase of cobalt contents, the reflection loss peak moves to high frequenc; moreover, to increase Co content more than 0.15, and the absorption intensity as well as the absorbing band of microwave absorber are enhanced obviously.展开更多
A series of nominal compositions MgAl_(2-x)(Li_(1/3)Ti_(2/3))_(x)O_(4)(x=0,0.04,0.08,0.12,0.16,and 0.20)ceramics were successfully prepared via the conventional solid-state reaction route.The phase compositions,micros...A series of nominal compositions MgAl_(2-x)(Li_(1/3)Ti_(2/3))_(x)O_(4)(x=0,0.04,0.08,0.12,0.16,and 0.20)ceramics were successfully prepared via the conventional solid-state reaction route.The phase compositions,microstructures,and microwave dielectric properties were investigated.The results of x-ray diffraction(XRD)and scanning electron microscopy(SEM)showed that a single phase of MgAl_(2-x)(Li_(1/3)Ti_(2/3))_(x)O_(4)ceramics with a spinel structure was obtained at x≤0.12,whereas the second phase of MgTi_(2)O_(5)appeared when x>0.12.The cell parameters were obtained by XRD refinement.As the x values increased,the unit cell volume kept expanding.This phenomenon could be attributed to the partial substitution of(Li_(1/3)Ti_(2/3))^(3+)for Al^(3+).Results showed that(Li_(1/3)Ti_(2/3))^(3+)doping into MgAl_(2)O_(4)spinel ceramics effectively reduced the sintering temperature and improved the quality factor(Q_f)values.Good microwave dielectric properties were achieved for a sample at x=0.20 sintering at 1500℃in air for 4 h:dielectric constantε_(r)=8.78,temperature coefficient of resonant frequencyτ_(f)=-85 ppm/℃,and Q_(f)=62300 GHz.The Q_(f)value of the x=0.20 sample was about 2 times higher than that of pure MgAl_(2)O_(4)ceramics(31600 GHz).Thus,MgAl_(2-x)(Li_(1/3)Ti_(2/3))_(x)O_(4)ceramics with excellent microwave dielectric properties can be applied to 5G communications.展开更多
Alkali and alkaline ion substitutions enhance the electrochemical properties of P2 sodium layered oxide,while the effect on electrochemical property enhancement of alkali and alkaline ions co-substitution is still unc...Alkali and alkaline ion substitutions enhance the electrochemical properties of P2 sodium layered oxide,while the effect on electrochemical property enhancement of alkali and alkaline ions co-substitution is still unclear.In this work,the structural and electrochemical properties of the Li alkali and Mg alkaline ions co-substituted P2 layered oxide Na_(0.67)(Li_(0.5)Mg_(0.5))_(0.1)(Ni_(0.33)Mn_(0.67))_(0.9)O_(2)are investigated in detail.Compared to the pristine and single-ion substituted materials,the co-substituted material shows an enhanced cycling performance with a reversible ca-pacity of 127 mAh/g and a capacity retention of 75%over 100 cycles at 0.5C.Galvanostatic intermittent titration technique(GITT)and cyclic voltammetry(CV)results show that the Li and Mg synergistically improve the ion diffusion.Moreover,the structure stability is also improved by the Li and Mg co-substitution that is clarified by operando X-ray diffraction(XRD)measurements.These results explain the origin of the enhanced electrochemical properties of the Li/Mg co-substituted P2 layered oxides for sodium ion batteries.展开更多
A Co-Mg co-substituted LiNi0.87Co0.10Mg0.03O2 cathode material was prepared by a co-precipitation method. The prepared LiNi0.87Co0.10Mg0.03O2 exhibits excellent electrochemical properties, such as initial discharge ca...A Co-Mg co-substituted LiNi0.87Co0.10Mg0.03O2 cathode material was prepared by a co-precipitation method. The prepared LiNi0.87Co0.10Mg0.03O2 exhibits excellent electrochemical properties, such as initial discharge capacities of 202.6 mA.h/g and 190.5 mA.h/g at 0.2C and 1C rate, respectively, in operating voltage range of 3.0-4.3 V （versus Li^＋/Li）. The capacity retentions are 96.1% and 93.4% at 0.2C and 1C, respectively, after 50 cycles. Moreover, the cycle performance of the sample was investigated in a 053048-type square Li ion battery. This type of battery can keep 81.7% of initial capacity after 500 charge-discharge cycles at 1C rate, which is close to that of commercial LiCoO2 battery. Therefore, the as-prepared material is capable of such high energy applications as portable product power.展开更多
基金Project(51274245) supported by the National Natural Science Foundation of China
文摘The microstructural evolution and mechanical properties of Al-18 Si-4 Cu-0.5 Mg alloy modified by the addition of La-Ce rare earth elements through OM,SEM,EPMA and tensile tests were investigated.The results of OM and SEM analyses indicated that primary Si particles were significantly refined from coarse block-like and irregular polygonal shapes into fine flaky shapes,while eutectic Si particles were modified from coarse and needle-like into fine and rod-or coral-like shapes with increase of La-Ce addition.The alloy exhibited the minimum primary Si particle size and the best mechanical properties with the addition of 0.3 wt.%La-Ce.The average particle size decreased from 61 to 28 μm,the ultimate tensile strength increased from 222 to 242 MPa and the elongation increased from 3.2% to 6.3%.In addition,modification mechanisms and fracture modes were explored by the means of SEM and EPMA.
基金Project supported by the National Natural Science Foundation of China （Grant Nos. 50632030 and 10804130） and the Shaanxi Provincial Natural Science Foundation, China （Grant No. 2011JM6012）.
文摘The piezoelectric, dielectric, and ferroelectric properties of the （LiCe） co-substituted calcium bismuth niobate （CaBi2Nb209, CBNO） are investigated. The piezoelectric properties of CBNO ceramics are significantly enhanced and the dielectric loss tan 5 decreased. This makes poling using （LiCe） co-substitution easier. The ceramics （where represents A-site Ca2＋ vacancies, possess a pure layered structure phase and no other phases can be found. The Cao.ss（LiCe）0.04[]0.04Bi2Nb209 ceramics possess optimal piezoelectric properties, with piezoelectric coefficient （d33） and Curie temperature （Tc） found to be 13.3 pC/N and 960 ℃ respectively. The dielectric and piezoelectric properties of the （LiCe） co-substituted CBNO ceramics exhibit very stable temperature behaviours. This demonstrates that the CBNO ceramics are a promising candidate for ultrahigh temperature applications.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 50632030 and 10804130)the Shaanxi Provincial Natural Science Foundation,China (Grant No. 2011JM6012)
文摘The piezoelectric,dielectric,and ferroelectric properties of the(LiCe) co-substituted calcium bismuth niobate(CaBi2Nb2O9,CBNO) are investigated.The piezoelectric properties of CBNO ceramics are significantly enhanced and the dielectric loss tan δ decreased.This makes poling using(LiCe) co-substitution easier.The ceramics(where represents A-site Ca2+ vacancies,possess a pure layered structure phase and no other phases can be found.The Ca0.88(LiCe)0.04 0.04Bi2Nb2O9 ceramics possess optimal piezoelectric properties,with piezoelectric coefficient(d 33) and Curie temperature(TC) found to be 13.3 pC/N and 960 C,respectively.The dielectric and piezoelectric properties of the(LiCe) co-substituted CBNO ceramics exhibit very stable temperature behaviours.This demonstrates that the CBNO ceramics are a promising candidate for ultrahigh temperature applications.
基金National Science Council, Taiwan! under grant !No. NSC-87-2112-M194-005.
文摘Phase evolution and magnetic properties of (Nd_o.95La_0.05)9.5-11Febal.M_2B10.5. where M=Cr, Ti, Nb, V, Mo, Zr, Hf, Ta, Mn or W, melt spun ribbons have been investigated. Almost all the alloy ribbons. except for(Nd_0.95La_0.05)_9.5Fe_78M_2B_10.5(M=Mo and Mn),consist merely two magnetic phases, namely α-Fe and R_2Fe_14B, which display a better combination of _iH_c and magnetic energy product. Remanence (Br) and coercivity (i_H_c) values in the range of 8.0 to 9.1 kG and 9.5 to 18.9 kOe. respectively, can be achieved. Among compositions studied, the Ti and W-substitutions were found to be most effective in increasing the Br and i_H_c, respectively. For a fixed refractory metal substitution, namely, M=C_r, Ti or Nb, an increase in the total rare earth concentration resulted in nanocomposites of small grain sizes and a high volume fraction of the R_2Fe_14B phase, leading to an increase in the magnetic properties.
文摘Co-substituted Ni-Zn ferrite was prepared by a chemical codeposition. The electromagnetic properties, zero reflection conditions and simulated reflection losses of the samples were investigated. As a result, it is found that with Co contents rising, the saturation magnetization (Ms) shows a tendency of decrease, while coercivity (Hc) varies clearly. In addition, Ni-Zn ferrite with different cobalt content can meet zero reflection conditions. And the reflection loss calculation indicates that with the increase of cobalt contents, the reflection loss peak moves to high frequenc; moreover, to increase Co content more than 0.15, and the absorption intensity as well as the absorbing band of microwave absorber are enhanced obviously.
基金the Chengdu University of Technology(Grant No.KYQD201907728)。
文摘A series of nominal compositions MgAl_(2-x)(Li_(1/3)Ti_(2/3))_(x)O_(4)(x=0,0.04,0.08,0.12,0.16,and 0.20)ceramics were successfully prepared via the conventional solid-state reaction route.The phase compositions,microstructures,and microwave dielectric properties were investigated.The results of x-ray diffraction(XRD)and scanning electron microscopy(SEM)showed that a single phase of MgAl_(2-x)(Li_(1/3)Ti_(2/3))_(x)O_(4)ceramics with a spinel structure was obtained at x≤0.12,whereas the second phase of MgTi_(2)O_(5)appeared when x>0.12.The cell parameters were obtained by XRD refinement.As the x values increased,the unit cell volume kept expanding.This phenomenon could be attributed to the partial substitution of(Li_(1/3)Ti_(2/3))^(3+)for Al^(3+).Results showed that(Li_(1/3)Ti_(2/3))^(3+)doping into MgAl_(2)O_(4)spinel ceramics effectively reduced the sintering temperature and improved the quality factor(Q_f)values.Good microwave dielectric properties were achieved for a sample at x=0.20 sintering at 1500℃in air for 4 h:dielectric constantε_(r)=8.78,temperature coefficient of resonant frequencyτ_(f)=-85 ppm/℃,and Q_(f)=62300 GHz.The Q_(f)value of the x=0.20 sample was about 2 times higher than that of pure MgAl_(2)O_(4)ceramics(31600 GHz).Thus,MgAl_(2-x)(Li_(1/3)Ti_(2/3))_(x)O_(4)ceramics with excellent microwave dielectric properties can be applied to 5G communications.
基金supported by Guangdong Basic and Applied Basic Research Foundation(2019A1515110897 and 2019B1515120028)supported by Ministry of Higher Education of Malaysia for the Fundamental Research Grant(FRGS/1/2018/STG02/UM/02/10)awarded to Woo Haw JiunnUniversity of Malaya research grant(GPF 038B-2018)
文摘Alkali and alkaline ion substitutions enhance the electrochemical properties of P2 sodium layered oxide,while the effect on electrochemical property enhancement of alkali and alkaline ions co-substitution is still unclear.In this work,the structural and electrochemical properties of the Li alkali and Mg alkaline ions co-substituted P2 layered oxide Na_(0.67)(Li_(0.5)Mg_(0.5))_(0.1)(Ni_(0.33)Mn_(0.67))_(0.9)O_(2)are investigated in detail.Compared to the pristine and single-ion substituted materials,the co-substituted material shows an enhanced cycling performance with a reversible ca-pacity of 127 mAh/g and a capacity retention of 75%over 100 cycles at 0.5C.Galvanostatic intermittent titration technique(GITT)and cyclic voltammetry(CV)results show that the Li and Mg synergistically improve the ion diffusion.Moreover,the structure stability is also improved by the Li and Mg co-substitution that is clarified by operando X-ray diffraction(XRD)measurements.These results explain the origin of the enhanced electrochemical properties of the Li/Mg co-substituted P2 layered oxides for sodium ion batteries.
基金Project(2010DFA72760)supported by US.China Collaboration on Cutting-edge Technology Development of Electric VehiclesProjects(50901009,51271029)supported by the National Natural Science Foundation of ChinaProject(12QNJJ013)supported by the Fundamental Research Funds for the Central Universities,China
文摘A Co-Mg co-substituted LiNi0.87Co0.10Mg0.03O2 cathode material was prepared by a co-precipitation method. The prepared LiNi0.87Co0.10Mg0.03O2 exhibits excellent electrochemical properties, such as initial discharge capacities of 202.6 mA.h/g and 190.5 mA.h/g at 0.2C and 1C rate, respectively, in operating voltage range of 3.0-4.3 V （versus Li^＋/Li）. The capacity retentions are 96.1% and 93.4% at 0.2C and 1C, respectively, after 50 cycles. Moreover, the cycle performance of the sample was investigated in a 053048-type square Li ion battery. This type of battery can keep 81.7% of initial capacity after 500 charge-discharge cycles at 1C rate, which is close to that of commercial LiCoO2 battery. Therefore, the as-prepared material is capable of such high energy applications as portable product power.
