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Experimental and Theoretical Investigations on the Effect of Magnetic Field on the Growth of Co3O4 Nanoparticles

Author: WangMingZuo
Tutor: ChenQianWang
School: University of Science and Technology of China
Course: Materials Physics and Chemistry
Keywords: Magnetic field induced by the hydrothermal synthesis method Cobalt tetroxide Nanoparticles Surface energy
CLC: TB383.1
Type: Master's thesis
Year: 2010
Downloads: 130
Quote: 1
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Abstract


With the continuous development of nanotechnology, nanomaterials people in recent years are no longer stuck in its simple preparation. Nano-material due to its reduction in size and increase of surface area, and its performance largely by its surface rather than determined by the nature of the body which requires us the material to a controlled synthesis, that do nanomaterials size controllable, controlled morphology, etc.. Currently used based surfactant nanomaterial synthesis method also has its limitations, such as the mechanism of action is unclear, in the solution too much interference factors. Magnetic field induced hydrothermal synthesis of law in regard to the traditional method has its unique advantages, such as simple reaction system, environmental pollution and so on. In this field at home and abroad has been made in a series of encouraging results, but these studies are mainly in experiments on magnetic field why can affect the growth process of the material and its physical properties, people do not have a reasonable explanation, and This is precisely we want this to continue to promote the go must understand and figure out this problem also helps us in a stronger magnetic field in the future research. In addition, the magnetic field induced synthesis of materials intended also limited to ferromagnetic or ferrimagnetic material. Therefore the magnetic field induced by material synthesis both theoretically and experimentally are also worthy of us to explore further. Room temperature paramagnetic tetroxide three cobalt study focuses on theoretical and experimental two aspects of study magnetic field in the material growth process material morphology affect the paper intends to adopt, to be able to find the mechanism of the magnetic field and its further promotion to induce the synthesis of the magnetic field on the other materials. The main results of the paper can be summarized as follows: 1. Successful use of the magnetic field induced by the hydrothermal synthesis method controlled synthesis of Co 3 O 4 nanoparticles. We succeeded in finding a simple, non-surfactant system to synthesize Co 3 O 4 nano-particles, and observed the external magnetic field during the synthesis of the final product the impact. Study found, without applying external magnetic field are prepared Co 3 O 4 nanoparticles irregular polyhedron imposed external magnetic field are prepared Co O 4 nanoparticles is the cube of the rules. By adjusting the other parameters of the reaction system, such as solvent ratio and the amounts of reactants, we have successfully synthesized the particle size ranging from 8 nm to 120 nm nano cube, and found that the induction of the magnetic field for different particle size The nano-particles are present. This also shows that the particles in the initial stages of its growth has been presented cube appearance (100) plane reveal rather late in its growth is simply the process of the cube grew. Successfully validated theoretically the magnetic field can change the material different crystal planes of the crystal surface this proposition. We use a software based on the calculation of the density functional theory (VASP) to calculate the surface of different crystal faces. Through the establishment of a model having different magnetic structures, we have studied in detail before and after applying a magnetic field (100) and (111) plane lattice energy change. We found that an external magnetic field is not applied, the (100) plane and the (111) plane surface respectively to 1.849 J / m 2 , from about 1.64 J / m 2 ; while After the external magnetic field is applied, the surface of the two faces of respectively to 1.326 J / m 2 , from about 1.44 J / m 2 . The outer under the influence of the magnetic field, (100) lower surface energy than the (111) surface of fast, and replace the (111) surface crystal plane to the lowest surface. According to the crystal growth thermodynamic theory, the lowest energy surface in the crystals of the final morphology show Thus in the applied magnetic field, the lowest energy (100) plane will be revealed out, thereby nano-particles shows the appearance of the cube, this also with our experiments results reached a very good agreement. When the external magnetic field does not exist, the (111) plane and the (100) plane may be present competitive growth of the relationship, so that the nano-particles showed irregular polyhedral shape. To sum up, in this paper, we verified from experimental and theoretical magnetic field can change the material different crystal planes of the crystal surface this proposition. Based on this proposition, we can make extensive use of the magnetic field to regulate the growth process of the material. Magnetic field induced by the hydrothermal synthesis method as a simple, do not use the method of surfactant, has a very broad application prospects. Our findings not only contribute to further understanding of the interaction between the magnetic field and the material, and other work in this area, such as a very important guiding significance in the synthesis of molecular magnets.

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