Synthesis, Characterization And Applications Of Magnetic Composite Nano-materials

As a broad used basic functional materials,the application of magnetic nano-materials have penetrated into every aspects of national economy and national defense science and technology. The particle size and structure determine the final properties of the magnetic nano-materials. Therefore, it is believed that the synthesis of magnetic nano-materials with novel structure and unique properties play a significant role in expanding its application. In this work, magnetic nano composties based on Fe₃O₄ have been synthesized. The details are as the follows:1. Firstly, we briefly introduced the importance and general trend of magnetic nano-materials. Secondly, the basic properties of magnetic nano-materials were introduced. Thirdly, we provided an overview of the application and the synthesis of magnetic nano-materials. Finally, a brief introduction of magnetic nanocomposites was summarized.2. A Fe₃O₄/Ag composite, with high efficiency in the degradation of Rhodamine B was synthesized through a simple sonochemical method. A formation mechanism was proposed and discussed. This sonochemical method is attractive since it eliminated the use of any reductants, which is necessary to transform the Ag+ to the Ag0. In comparison to high temperature or high pressure experimental processes, this method is mild, inexpensive, green and efficient. The M-H hysteresis loop of these Fe₃O₄/Ag composite microspheres indicates that the composite microspheres exhibit superparamagnetic characteristics at room temperature. Furthermore, these composites can be recycled six times by magnetic separation without major loss of activity.3. Fe₃O₄-TiO₂ photocatalyst was synthesized by a novel sonochemical method. This method is attractive since it eliminated a high-temperature heat treatment required in conventional sol-gel method, which is important in transforming amorphous titanium dioxide into a photoactive crystalline phase. In comparison to other methods, the developed method is simple, mild, green and efficient. The M-H hysteresis loop for Fe₃O₄-TiO₂ indicates that the hybrid catalysts show superparamagnetic characteristics at room temperature. Photocatalytic activity studies confirm the as-prepared nano composites have high photocatalytic ability toward the photodegradation of Rhodamine B solution. Furthermore, the photodecomposition rate decreases only slightly after six cycles of the photocatalysis experiment.4. This chapter reports the fabrication of a novel rattle-type nanocatalysts system possessing a well-defined core of hierarchical nickel silicate (NS) protected superparamagnetic Fe₃O₄ nanocrystals and a layer of uniform Ag nanoparticles on the outer shell by a multi-step approach and their applications as magnetically recoverable catalysts for the degradation of tetranitro-phenol. As a result, the multifunctional well-designed microspheres showed high performance in the reduction of tetranitro-phenol and the rate of the catalytic reaction can be controlled by changing the concentration of nanocatalysts. In particular, there was no visible decrease in the catalytic activity of the reused catalysts even after being recycled 8 times (average 99.9 %), from which it can be deduced that Fe₃O₄@NS partices are very suitable as catalysts support for catalysts separation and redispersion.