M.H.Khedr
材料科学技术（英）
CO2 is a major component of the greenhouse gases, which causes the global warming. To reduce CO2 gas, high activity nanosized Ni+2 substituted Fe2TiO5 samples were synthesized by conventional ceramic method. The effect of the composition of the synthesized ferrite on the H2-reduction and CO2-catalytic decomposition was investigated. Fe2TiO5 (iron titanate) phase that has a nanocrystallite size of ~80 nm is formed as a result of heating Fe2O3 and TiO2 while the addition of NiO leads to the formation of new phases (~80 nm) NiTiO3 and NiFe2O4, but the mixed solid of NiO and Fe2O3 results in the formation of NiFe2O4 only. Samples with Ni+2=0 shows the lowest reduction extent (20%); as the extent of Ni+2 increases, the extent of reduction increases. The increase in the reduction percent is attributed to the presence of NiTiO3 and NiFe2O4 phases, which are more reducible phases than Fe2TiO5. The CO2 decomposition reactions were monitored by thermogravimetric analysis (TGA) experiments. The oxidation of the H2-reduced Ni+2 substituted Fe2TiO5 at 500℃ was investigated. As Ni+2 increases, the rate of reoxidation increases. Samples with the highest reduction extents gave the highest reoxidation extent, which is attributed to the highly porous nature and deficiency in oxygen due to the presence of metallic Fe, Ni and/or FeNi alloy. X-ray diffraction (XRD) and transmission electron microscopy (TEM) of oxidized samples show also the presence of carbon in the sample containing Ni+2>0, which appears in the form of nanotubes (25 nm).
关键词:
Nanocrystallite
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M.H.Khedr
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A.A.Farghali
材料科学技术（英）
Copper ferrite, CuFe2O4, one of the important ferrites due to its interesting electrical, magnetic and structural properties, is obtained by a novel self flash combustion of a homogeneous mixture of one mole copper acetate monohydrate, Cu(CH3COO)2•H2O, and two moles of iron (III) acetate basic, Fe(CHCOO)2•OH. Nanocrystalite (89 nm) copper ferrite (less than 100%) is obtained at lower temperatures, whereas 100% copper ferrite is obtained after calcination at 1000℃. Thermal analysis (TG and DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), photo microscopy, magnetic and porosity measurements have been carried out for the specimens obtained after calcinations at 700, 800, 900 and 1000℃ to characterize the conversion efficiency of the powder precursors to copper ferrite. It was found that increasing temperature leads to great improvement in the magnetic properties. By increasing calcination temperature from 700～1000℃ saturation magnetic flux density (Bs) increased from 17.8 to 40.8 emu/g, while remnant magnetic flux density (Br) increased from 10.1 to 17.11 emu/g.
关键词:
Copper ferrite
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