| Summary: | 碩士 === 東海大學 === 化學工程學系 === 94 === The iron oxides nano-particles were prepared by using the coprecipitation with various Fe2+/Fe3+ ratios, the kinds and concentrations of surfactants. Then, the iron oxides@Au nano-particles were prepared by the reduction of Au3+ on the iron oxides. The grain size, particle size, surface morphology, compositions of iron oxides and iron oxides@Au nano-particles were analyzed by XRD, AEM, FE-SEM, oxidation/reduction titration, and AAS, respectively. The magnetic properties of iron oxides were measured by SQUID. The magneto-caloric effect of the iron oxides and iron oxides@Au nanoparticles were also investigated in this thesis.
The particle sizes of iron oxides with non-uniform morphology and size distribution decreased by the decrease in the molar ratio of Fe2+/Fe3+. The average particle sizes of iron oxides were obtained to be 26, 17, and 15 nm for Fe2+/Fe3+ ratio of 2M/1M, 1M/2M, and 1M/2.5M, respectively. The morphology and particle size was affected by surfactant at a relative lower concentration of Fe2+ and Fe3+. The particle size of iron oxides decreased from 17 to 13 nm with increasing the concentration of SB12 (N-dodecyl-N,N-dimethyl-3-ammonio-1-propane-sulfonate) surfactant from 1.656 to 6.62 mM for preparing iron oxides at the Fe2+/Fe3+ ratio of 0.5M/0.25M. The saturation magnetization of iron oxides decreased with decreasing the particle size. The particle sizes of iron oxides@Au prepared in the aqueous solution were obtained to be 11-30, 12-30 and 15-40 nm for the iron oxides/Au molar ratios of 1/1, 1/2 and 1/3, respectively. The saturation magnetization of iron oxides@Au was lower than that of iron oxides.
The increase in the temperature was increased with the strength and frequency of applied magnetic field, and the amount of magnetic material in the magneto-caloric effect analysis. The saturation magnetization and the increase in the temperature in the magneto-caloric analysis were found to be 68.5, 49.68 and 16.11 emu g-1 , and 1.1, 0.85 and 0.6 oC for the iron oxides prepared at the Fe2+/Fe3+ ration of 1M/2M, 1M/2.5M, 1M/3M, respectively. The increase in the temperature of iron oxides@Au nano-paritcles in the magneto-caloric analysis decreased with increasing Au precursor for preparation due to the decrease in the saturation magnetization and the magnetic hysteresis area.
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