Biphasic 0.8BaTiO3/0.2Ni(1-x)CoxFe2O4 nanopowders by in situ sol-gel synthesis
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Nanopowders of the 0.8BaTiO3/0.2Ni(1-x)CoxFe2O4 (x=0, 0.25, 0.5, 0.75, and 1) were synthesized by the in situ sol-gel method using poly(acrylic acid) (PAA1800) as a chelating agent. The synthesis developed using PAA1800 ensured the simultaneous crystallization of two phases. The results provided a reliable method for producing biphasic nanopowders in all the compositions of Co-Ni-ferrite with an average particle size of less than 50 nm with a potential application in lead-free magnetoelectric particulate composites. The XRD results indicated the formation of only BaTiO3 and Ni(1-x)CoxFe2O4 phases, verifying that there was no interdiffusion between the perovskite BaTiO3 and spinel Co-NiFe2O4 phases during the crystallization phase. A detailed analysis of the crystalline structures was conducted to quantify the phases using the Rietveld method, and thus ensure the success of the in situ sol-gel synthesis.Keywords:
Rietveld Refinement
Atmospheric temperature range
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The latest publications regarding the development of technology to control inclusion compositions focusing on MgO·Al2O3 spinel inclusions were summarized in this review article. The problems caused by spinel inclusions, which affect practice as well as products were shown. The formation mechanism of MgO·Al2O3 spinel inclusions is secondly explained thermodynamically from the view points of chemistries of molten steels and slag compositions. Furthermore, crystallization behaviour of spinel was introduced. Countermeasures conducted in practices and laboratories were shown along with some problems still left that should be solved in the future.
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Reflection loss
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Nanostructured spinel LiMn1.5Ni0.5O4, layered Li1.5Mn0.75Ni0.25O2.5 and layered-spinel hybrid particles have been successfully synthesized by hydrothermal methods. It is found that the nanostructured hybrid cathode contains both spinel and layered components, which could be expressed as Li1.13Mn0.75Ni0.25O2.32. Diffraction-contrast bright-field (BF) and dark-field (DF) images illustrate that the hybrid cathode has well dispersed spinel component. Electrochemical measurements reveal that the first-cycle efficiency of the layered-spinel hybrid cathode is greatly improved (up to 90%) compared with that of the layered material (71%) by integrating spinel component. Our investigation demonstrates that the spinel containing hybrid material delivers a high capacity of 240 mAh g–1 with good cycling stability between 2.0 and 4.8 V at a current rate of 0.1 C.
Hydrothermal Synthesis
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Ni2+ substituted spinel ferrites with formula CdxNi1-xFe2O4 were prepared by microwave Sol-gel method. The XRD analysis of the synthesized ferrite confirms the formation of cubic spinel structure of ferrite. Rietveld refined XRD patterns revealed the cubic spinel phase with Fd-3m space group. The oxygen position and the cation distribution are determined by means of Rietveld analysis, indicating the existence of mixed ferrites in each sample. The magnetic properties of all ferrites were studied by using a vibration sample magnetometer. The fast synthesis of spinel ferrites is yielded due to use of the microwave sintering technique.
Rietveld Refinement
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In this paper,by taking the fused magnesia,fused magnesium aluminate spinel and fused spinel with TiO2 as raw materials,we studied the effect of adding 15% magnesium aluminate spinel or spinel with TiO2 on the performance of magnesia material respectively.The results indicate that after adding 15% magnesium aluminate spinel or spinel with TiO2 in magnesia material,the sintering character and penetration resistance of samples improved,but the bend strength and corrosion resistance of samples decreased.At the same time,the magnesia material adding spinel with TiO2 has better performance than the magnesia material adding magnesium aluminate spinel.
Aluminate
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Synthesis of the positive active materials of spinel LiMn2O4 via sol-gel methods for lithium ion batteries and their future de- velopment were summarized. Sol-gel methods have outstanding advantages in preparing the materials, and great progress has been made in the research work. However, the systematic and thorough study is still lacking, which results in the diffculty to put the technique into industry. The future research work in this field is considered as the follows: fundamental studying of the sol-gel processes, modifying spinel LiMn2O4 by dopants, synthesizing nanocrystalline powders and thin films of spinel LiMn2O4 synthesi- zing spinel LiMn2O4 at lower temperature, optimizing the sol-gel processes, lowering the costs and realizing industrialization.
Nanocrystalline material
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Effect of spinel kinds on the properties of alumina—spinel castables was investigated. The results showed that the addition of various kinds of spinels has an effect on the physical and mechanical properties of these refractory castables. The reason is that the A l 2 O 3 ‐rich spinel precipitated A l 2 O 3 and M g O ‐rich spinel solid solution and formed secondary spinel. In addition, stable spinel in castables during heat treatment process was found to be more effective for enhancing cold and hot strength.
Refractory (planetary science)
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LiCoxMn2-xO4 - coated spinel LiMn2O4 was prepared by soft chemistry process, then the LiCoxMn2-xO4 - coated spinel LiMn2O4 and the uncoated spinel LiMn2O4 were characterized by methods of cyclic voltammetry, constant current charge - discharge and potential decay. Ther results showed that the initial capacity of LiCoxMn2-xO4 -coated spinel LiMn2O4 was lower than that of uncoated spinel LiMn2O4 After 50 cycles, the capacity loss of uncoated spinel LiMn2O4 was 56. 2% of initial, while that of LiCoxMn2-xO4 -coated spinel LiMn2O4 was 33. 5%, and LiCoxMn2-xO4 - coated spinel LiMn2O4 had better chemical stability than uncoated spinel LiMn2O4. Better cyclic stability of LiCoxMn2-xO4- coated spinel LiMn2O4 may be attributed to the surface layer LiCoxMn2-xO4, which reduces the LiMn2O4 dissolution into electrolyte.
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