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1.
BATOO K M KUMAR S PRAKASH R ALIMUDDIN SONG JI CHUNG H JEONG H KOO B H LEE C G 《中南工业大学学报(英文版)》2010,17(6):1129-1132
The effect of non-magnetic Al3+ ion doping on the magnetic properties of MnFe2−2x
Al2x
O4 (0≼x≼0.4) spinel ferrites was studied using M?ssbauer spectroscopy measurements at room temperature. From the M?ssbauer study,
it is observed that the resolved hyperfine sextets are due to the distribution of Fe ions on the two sublattices of the spinel
ferrites. The value of the isomer shift obtained from the fitting of the M?ssbauer spectra indicates that Fe ions are in +3
state. A paramagnetic doublet is observed at degree of inversion x=0.4, superimposed on the hyperfine sextets, indicating that the super-exchange interaction A–B decreases due to the dilution
of sublattice by Al3+ ions. The hyperfine magnetic field decreases at both interstitial sites of tetrahedral (A) and octahedral (B) with the increase
in Al concentration. 相似文献
3.
《中南大学学报(英文版)》2010,(6)
The effect of non-magnetic Al3+ ion doping on the magnetic properties of MnFe2-2xAl2xO4(0≤x≤0.4) spinel ferrites was studied using Mssbauer spectroscopy measurements at room temperature.From the Mssbauer study,it is observed that the resolved hyperfine sextets are due to the distribution of Fe ions on the two sublattices of the spinel ferrites.The value of the isomer shift obtained from the fitting of the Mssbauer spectra indicates that Fe ions are in +3 state.A paramagnetic doublet is observed at degree of inversion x=0.4,superimposed on the hyperfine sextets,indicating that the super-exchange interaction A-B decreases due to the dilution of sublattice by Al3+ ions.The hyperfine magnetic field decreases at both interstitial sites of tetrahedral(A) and octahedral(B) with the increase in Al concentration. 相似文献
4.
KUMAR S BATOO K M PRAKASH R CHOI H K KOO B H SONG JI CHUNG H JEONG H LEE C G 《中南工业大学学报(英文版)》2010,17(6):1133-1138
The complex impedance spectroscopy and surface morphology of Mn1+x
Fe2−2x
Ti
x
O4 (0⩽x⩽0.5) system, prepared using a conventional solid state reaction technique, were investigated. The impedance spectroscopy
measurements were carried out at room temperature in the frequency range of 42–5 MHz. The electrical processes in the samples
were modeled in the form of an equivalent circuit made up of a combination of two parallel RC circuits attributed to grain
and grain boundaries. The DC conductivity obtained by extrapolation of AC data using impedance spectroscopy and four-probe
method increases at 10% doping of Ti ions. The energy-dispersive X-ray (EDX) pattern confirmed the homogeneous mixing of the
Mn, Fe, Ti and O atoms in pure and doped ferrite samples. 相似文献
5.
《中南大学学报(英文版)》2010,(6)
The mixed spinel ferrite system Mg0.95Mn0.05Fe2-2xTi2xO4(0≤x≤0.7) was synthesized by the conventional solid-state reaction technique.The effect of Ti4+ doping was studied by using the Mssbauer spectroscopy measurements at room temperature.From the analysis of the Mssbauer spectra,it is observed that s-electron density,electric field gradient(EFG),quadrupole coupling constant(QCC) and the net hyperfine magnetic fields acting on the M-ssbauer nuclei-FeA3+ and FeB3+ change with the increase of Ti4+ doping in Mg0.95Mn0.05Fe2O4.The hyperfine magnetic field decreases with the increase of Ti4+ doping. 相似文献
6.
Let A be a real matrix or a sign pattern of order n. N_ (A) denotes the number of negative entries in A. In 1972 R DeMarr and A Steger conjectured: If A is a real matrix of order n such that A^2≤0, then N- (A^2)≤( n - 1)^2 1. Now the conjecture is proved to be true when A is reducible or a matrix of order n≤3 and some sufficient conditions for N- (A^2)≤(n - 1)^2 1 are given. It is also proved that N_ (A^2)≤n^2 -4n 5 when A is a reducible combinatorially symmetric sign pattern such that A^2≤0, and the extreme sign patterns are characterized. 相似文献
7.
8.
9.
《中南大学学报(英文版)》2010,(6)
The complex impedance spectroscopy and surface morphology of Mn1+xFe2-2xTixO4(0≤x≤0.5) system,prepared using a conventional solid state reaction technique,were investigated.The impedance spectroscopy measurements were carried out at room temperature in the frequency range of 42-5 MHz.The electrical processes in the samples were modeled in the form of an equivalent circuit made up of a combination of two parallel RC circuits attributed to grain and grain boundaries.The DC conductivity obtained by extrapolation of AC data using impedance spectroscopy and four-probe method increases at 10% doping of Ti ions.The energy-dispersive X-ray(EDX) pattern confirmed the homogeneous mixing of the Mn,Fe,Ti and O atoms in pure and doped ferrite samples. 相似文献
10.
XidongWang JinlanCui XinleiGe ShiliZheng MeiZhang YiZhang 《北京科技大学学报(英文版)》2004,11(6):500-504
Phase diagrams of complex multi-component aqueous chromium salt system are the important theoretical bases for increasing the recovery ratio of chromium and reducing the poisonous waste in the chromate production process. Phase equilibrium of multi-component system has been calculated from the limited known data with thermodynamic models. The phase equilibriums of KOH-K2CrO4-H2O, KOH-KAlO2-H2O, NaOH-Na2CrO4-H2O and NaOH-NaAlO2-H2O systems were calculated with thermodynamic models. The solubilities of Cr and Al was measured in the systems at different temperatures. The results were compared with experimental data and they are consistent with each other. It shows that the lower concentration of KOH (or NaOH) is favorable for thecrystallization of KAlO2 (or NaAlO2) and higher concentration of KOH (or NaOH) is favorable for the crystallization of K2CrO4(Na2CrO4). Therefore, K2CrO4 (or Na2CrO4) can be separated from KAlO2 (or NaAlO2) with controlling the KOH concentration in solutions of KOH-K2CrO4-KAlO2-H2O or NaOH-Na2CrO4-NaAlO2-H2O systems. 相似文献
11.
12.
The thermal decomposition of Leightonite, K2Ca2Cu (SO4)4·2H2O, was studied by thermal gravimetric analysis(TGA), differential thermal analysis(DTA), X-ray diffraction(XRD), etc.The results show that the Leightonite is dehydrated around 170 ℃ to 390 ℃ and transformed to be new intermediate (K-Cu-SO4) sulphate salt with bright-green color. Moreover, the chemical structure changes during the thernal decomposition process was describled in detail. And the as-resulting phases are demonstrated to be K2Ca2(SO4)3, K2SO4, CaSO4,and Cu2O. 相似文献
13.
王锦华 《武汉理工大学学报(材料科学英文版)》2008,23(5):683-686
The thermal decomposition of Leightonite, K2Ca2Cu(SO4)4·2H2O, was studied by thermal gravimetric analysis(TGA), differential thermal analysis(DTA), X-ray diffraction(XRD), etc. The results show that the Leightonite is dehydrated around 170 ℃ to 390 ℃ and transformed to be new intermediate (K-Cu-SO4) sulphate salt with bright-green color. Moreover, the chemical structure changes during the thernal decomposition process was describled in detail. And the as-resulting phases are demonstrated to be K2Ca2(SO4)3, K2SO4, CaSO4 ,and Cu2O. 相似文献
14.
Xidong Wang Jinlan Cui Xinlei Ge Shili Zheng Mei Zhang and Yi Zhang Metallurgical Ecological Engineering School University of Science Technology Beijing Beijing China Institute of Process Engineering Chinese Academy of Sciences Beijing China 《北京科技大学学报(英文版)》2004,11(6)
Phase diagrams of complex multi-component aqueous chromium salt system are the important theoretical bases for increasing the recovery ratio of chromium and reducing the poisonous waste in the chromate production process. Phase equilibrium of multi-component system has been calculated from the limited known data with thermodynamic models. The phase equilibriums of KOH-K2CrO4-H2O, KOH-KAlO2-H2O, NaOH-Na2CrO4-H2O and NaOH-NaAlO2-H2O systems were calculated with thermodynamic models. The solubilities of Cr and Al was measured in the systems at different temperatures. The results were compared with experimental data and they are consistent with each other. It shows that the lower concentration of KOH (or NaOH) is favorable for the crystallization of KAlO2 (or NaAlO2) and higher concentration of KOH (or NaOH) is favorable for the crystallization of K2CrO4 (Na2CrO4). Therefore, K2CrO4 (or Na2CrO4) can be separated from KAlO2 (or NaAlO2) with controlling the KOH concentration in solutions of KOH-K2CrO4-KAlO2-H2 相似文献
15.
卢喜瑞 《武汉理工大学学报(材料科学英文版)》2014,29(1):1-4
Pyrochlore Gd2Zr2O7 are considered as an excellent candidate for treatment of radioactive waste forms, because of its superior physical, chemical and anti-irradiation properties. To investigate the phase and structure of pyrochlore Gd2Zr2O7 used for immobilizing Pu(Ⅲ), trivalent europium was used as the simulacrum for plutonium with trivalence. The compounds of stoichiometry Gd2-xEuxZr2O7(0.0x2.0) synthesized by high temperature solid state reaction method, were analyzed with the help of XRD and Rietveld structural refinement method. The results indicated that the phases of compounds continuously kept the phase of pyrochlore under our experimental condition. The linear relation between a andxwas discovered in the system of Gd2-xEuxZr2O7(0.0≤x≤2.0) at 1 773 K, which accorded with a=10.538 41+0.008 95 x, V=1 170.373 32+2.985 97 x. 相似文献
16.
HUANG Fulong SHAO Haicheng DAI Honglian HUANG Jian LI Shipu 《武汉理工大学学报(材料科学英文版)》2005,20(B12):195-197
CoFe2O4 nanoparticles that were synthesized by coprecipitation method were heat-treated at different temperature , and analyzed by XRD and TEM. The particle size and magnetic properties of CoFe2O4 nanoparticles also was tested. The results showed that the average sizes became large as the heat-treated temperature increased, the saturation magnetization and remanent magnetization increased with the heat-treated temperature too. 相似文献
17.
黄福龙 《武汉理工大学学报(材料科学英文版)》2005,20(Z1)
1Introduction Recently,spinelferritenanoparticleshavebeenin tensivelyinvestigatedandwidelyappliedintheinforma tionstoragesystem,ferrofluidtechnology,magnetocaloric refrigerationandmedicaldiagnosticsduetotheirremark ableelectricalandmagneticproperties[14].… 相似文献
18.
《武汉理工大学学报(材料科学英文版)》2020,(4)
A temperature stable Li_2Zn_(0.95)(Sr_xCa_(1-x))_(0.05)Ti_3O_8 (0≤x≤1) ceramics were fabricated using a conventional solid-state route sintered at 1100 ℃ for 4 h.The XRD results indicate that the main phase Li_2ZnTi_3O_8 and secondary phase including Sr_xCa_(1-x)TiO_3 (0≤x≤1) solid solution and TiO_2 co-exist in composite and form a stable composite system when the (Ca_xSr_(1-x)) (0≤x≤1) substitutes for Zn of Li_2ZnTi_3O_(8 )ceramic.As x is increased from 0 to 1,the relative permittivity (ε_r) increases from 26.65 to 27.12,and the quality factor (Q×f) increases from 63 300 to 66 600 GHz.With the increased of x,the temperature coefficient of resonant frequency (τ_f) increases from 0.27 to 8.23 ppm/℃,and then decreases to 3.51 ppm/℃.On the whole,the Li_2Zn_(0.95)(Sr_xCa_(1-x))_(0.05)Ti_3O_8 (0≤x≤1) ceramics show excellent comprehensive properties of middle ε_r=25-27,higher Q×f ≥ 60000 GHz and τ_f ≤±8.5 ppm/℃. 相似文献
19.
TIANBoran LIUJiachen ZHAOYuhong LIUMingzheng 《武汉理工大学学报(材料科学英文版)》2005,20(1):17-20
Green bodies of 25% CePO4/ZrO2 and ZrO2 ceramics were joined at 1450℃ for 120 min without applied pressure by using mixed powders slurries composed of CePO4 and ZrO2. The effects of CePO4/( CePO4 ZrO2 ) ratio of the adhesive on the bond strength of the joints were investigated. Maximum bond strength of 414 MPa was obtained by joining an adhesive with the ratio of 0. 5 Under the experimental conditions, the grain size of the particles grown in the joint was smaller than that in joined ceramics. The microstructure of the joint was more homogeneous than that of the matrix and without obvious crack, pores and other defects. 相似文献
20.
《武汉理工大学学报》2015,(3)
采用固相反应法制备了复相体系(1-x)SrZnP2O7-xSr2P2O7陶瓷,研究了该体系的相组成、晶体结构对微波介电性能的影响。研究结果表明,在比例系数x从0.2到0.8的范围内所获得的材料只含有SrZnP2O7和Sr2P2O7两种晶体相,并且当烧结温度合适时所有复相比例的材料均可获得较高的烧结密度。烧结温度的升高会使材料的相对密度和介电常数均有所上升;而随着x值的增大,体系中的Sr2P2O7相含量也逐渐升高,在同样的烧结温度下则伴随着品质因子Q×f值的下降和频率温度系数τf值的上升。在复合比x=0.6时,上述材料具有较优良的微波介电性能:ε=7.44,Q×f=10200GHz,τf=-28.6×10-6/℃。上述结果表明,复合Sr2P2O7相可以有效地使SrZnP2O7材料的负的频率温度系数τf值得到补偿。 相似文献