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Liu C.,Guangxi University | Liu C.,Guangxi Institute of Metallurgy | Wu X.,Guangxi University | Wu W.,Guangxi University | And 2 more authors.
Journal of Materials Science | Year: 2011

The precursor of nanocrystalline LiMnPO4 was obtained by solid-state reaction at low heat using Li2SO4•H 2O, MnSO4•H2O, and Na3PO 4•12H2O as raw materials, maintaining the mixture at 333 K for 4 h, and then washing the mixture with deionized water to remove soluble inorganic salts, and at last drying at 373 K. The nanocrystalline LiMnPO4 was obtained by calcining the precursor. The precursor and its calcined products were characterized using TG/DTA, FT-IR, and XRD. The data showed that the precursor dried at 373 K for 3 h was a compound with amorphous structure. However, when the precursor was calcined at 973 K for 2 h, highly crystallization LiMnPO4 with orthorhombic structure [space group Pmnb (62)] was obtained with a crystallite size of 38 nm. The mechanism and kinetics of the crystallization process of LiMnPO4 were studied using XRD technique, the results showed that activation energy of the crystallization process of LiMnPO4 was 103.30 kJ/mol, and the mechanism of crystallization process of LiMnPO4 is the random nucleation and growth of nuclei reaction. © 2010 Springer Science+Business Media, LLC. Source


Wu X.,Guangxi University | Wu W.,Guangxi University | Liu C.,Guangxi Institute of Metallurgy | Li S.,Guangxi University | And 2 more authors.
Chinese Journal of Chemistry | Year: 2010

The layered nanocrystalline sodium manganese phosphate was synthesized by low-heating solid state reaction using MnSO4 ·H2O and Na3PO4 ·12H2O as raw materials. The resulting sodium manganese phosphate and its calcined products were characterized using element analysis, thermogravimetry and differential thermal analyses (TG/DTA), Fourier transform IR (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-visible (UV-Vis) absorption spectroscopy, and magnetic susceptibility. The results showed that the product obtained at 70°C for 3 h, NaMnPO4 ·3H2O, was a layered compound, and its crystallite size and interlayer distance were 27 nm and 1.124 nm, respectively. The thermal process of NaMnPO4 ·3H2O between room temperature and 700°C experienced three steps, the dehydration of the one adsorption water at first, and then dehydration of the two crystal waters, at last crystallization of NaMnPO 4. Magnetic susceptibility measurements of NaMnPO4 · 3H2O from room temperature to 2.5 K point to ferrimagnetic ordering at TN-35 K. The NaMnPO4 ·3H2O was synthesized via a solid-state reaction at low-heating. The characterization results showed that NaMnPO4 ·3H2O was a layered compound, the d5 electrons in the Mn2+ ion were of high-spin state, and NaMnPO4 ·3H2O had ferrimagnetic properties. © 2010 SIOC, CAS, Shanghai & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Wu X.,Guangxi University | Wu W.,Guangxi University | Wu W.,Guangxi Colleges and Universities | Qin L.,Guangxi University | And 4 more authors.
Journal of Magnetism and Magnetic Materials | Year: 2015

La3+-doped Ni-Zn ferrites with a nominal composition of Ni0.5Zn0.5LaxFe2-xO4 (where x=0-0.3) are prepared by solid-state reaction at low temperatures. X-ray diffraction data shows that single phase Ni0.5Zn0.5Fe2O4 is obtained at 600°C, but all samples consist of the main spinel phase in combination of a small amount of a foreign LaFeO3 phase after doping. When the precursor is calcined at 900°C, the lattice constants of the ferrites initially increase after La3+ doping, but then become smaller with additional La3+ doping. The addition of La3+ results in a reduction of crystallite size. Magnetic measurement reveals that the specific saturation magnetization (Ms) of the as-prepared ferrites decreases with increasing La3+ substitution, while the coercivity (Hc) of Ni0.5Zn0.5LaxFe2-xO4 obtained above 800°C increases with increasing La3+ substitution. © 2014 Published by Elsevier B.V. Source


Huang J.,Guangxi University | Huang J.,Guangxi Institute of Metallurgy | Su P.,Guangxi Institute of Metallurgy | Wu W.,Guangxi University | And 2 more authors.
Journal of Superconductivity and Novel Magnetism | Year: 2012

Cu 0.5Mg 0.5Fe 2O 4 precursor was synthesized by solid-state reaction at low heat using CuSO4*5H2O, MgSO4*6H2O, FeSO4*7H2O, and Na2C2O4 as raw materials. The spinel Cu 0.5Mg 0.5Fe 2O 4 was obtained via calcining precursor above 300 °C in air. The precursor and its calcined products were characterized by thermogravimetry and differential scanning calorimetry (TG/DSC), Fourier transform FT-IR, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), and vibrating sample magnetometer (VSM). The result showed that Cu 0.5Mg 0.5Fe 2O 4 obtained at 600 °C had a saturation magnetization of 36.8 emu g-1. The thermal process of Cu 0.5Mg 0.5Fe 2O 4 precursor experienced two steps, which involved the dehydration of the five and a half crystal water molecules at first, and then decomposition of Cu0.5Mg0.5Fe2(C2O4)3 into crystalline Cu 0.5Mg 0.5Fe 2O 4 in air. Based on the Kissinger equation, the values of the activation energy associated with the thermal process of the precursor were determined to be 85 and 152 kJ mol-1 for the first and second thermal process steps, respectively. © Springer Science+Business Media, LLC 2012. Source


Huang J.,Guangxi University | Huang J.,Guangxi Institute of Metallurgy | Su P.,Guangxi Institute of Metallurgy | Wu W.,Guangxi University | And 3 more authors.
Journal of Thermal Analysis and Calorimetry | Year: 2013

The Bi2Fe2(C2O4) 5·5H2O was synthesized by solid-state reaction at low heat using Bi(NO3)3·5H2O, FeSO 4·7H2O, and Na2C2O 4 as raw materials. The nanocrystalline BiFeO3 was obtained by calcining Bi2Fe2(C2O 4)5·5H2O at 600 C in air. The precursor and its calcined products were characterized by thermogravimetry and differential scanning calorimetry, FT-IR, X-ray powder diffraction, and vibrating sample magnetometer. The data showed that highly crystallized BiFeO3 with hexagonal structure [space group R3c(161)] was obtained when the precursor was calcined at 600 C in air for 1.5 h. The thermal process of the precursor in air experienced five steps which involved, at first, the dehydration of an adsorption water molecule, then dehydration of four crystal water molecules, decomposition of FeC2O4 into Fe 2O3, decomposition of Bi2(C2O 4)3 into Bi2O3, and at last, reaction of Bi2O3 and Fe2O3 into hexagonal BiFeO3. Based on Starink equation, the values of the activation energies associated with the thermal process of Bi2Fe 2(C2O4)5·5H2O were determined. Besides, the most probable mechanism functions and thermodynamic functions (ΔS ≠, ΔH ≠, and ΔG ≠) of thermal processes of Bi2Fe2(C 2O4)5·5H2O were also determined. © 2012 Akadémiai Kiadó, Budapest, Hungary. Source

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