Study On Preparation And Properties Of Co Ferrites

Cobalt ferrite has a large magneto-optical Kerr effect in the visible region so that it overcomes the shortcomings of small Kerr rotation angle and less antioxidant capacity, which amorphous rare earth-transition metal of commercial magneto-optical storage materials in the current market has in the short wavelength region. In addition, the cobalt ferrite with a moderate saturation magnetization field and the larger coercivity become very competitive next-generation high-density magneto-optical recording materials. However, at present the current research focus is how to enhance its coercivity further while proper saturation magnetization of cobalt ferrite is maintained, in order to obtain magneto-optical read-write characteristics suitable for high density information storage levels.In this study, cobalt ferrite as magnetic materials of high magnetic properties is prepared by low-heating solid-state sol-gel method and low-heating solid-state self-propagating combustion method respectively. This paper studies the appropriate process conditions of improved coupled preparation method to prepare cobalt ferrite, and the effect mechanism of different process conditions on the crystal structure and properties of the product is discussed. At the same time by means of TG-DSC, XRD, SEM and VSM technical means, the preparation of cobalt ferrite is tracked and detected, and its microstructure, morphology and magnetic properties are characterized further into preliminarily understanding the relationship between their microstructures and magnetic properties of the products.The study results show that: preparation process has a great influence on the structure and magnetic properties of the product. Under the experimental conditions, the optimum conditions of cobalt ferrite prepared by low-heating solid-state sol-gel method are cobalt-iron ratio 1:2, citric acid ratio 3, calcination temperature 700℃, calcination time 2h. The optimum conditions of cobalt ferrite prepared by low-heating solid-state self-propagating combustion method are cobalt-iron ratio 1:2, citric acid ratio 2, calcination temperature 600℃, calcination time 1h. Under optimum conditions, the two preparation methods can obtain uniform size (about 40nm), single-phase pure, nano-crystalline cobalt ferrite of high crystallinity and improve its magnetic properties to a greater extent to make it more suitable for magnetic optical recording. With the increase of cobalt content, the degree of crystallization of the product increases gradually, so the particle size decreases. With the increase of citric acid, the film, which is formed due to the adsorption growing on the liquid-solid interface of reactants during the reaction, plays a certain role in impeding ultrafine grains contacting and the accumulation process and generats repulsive force between particles. Therefore, it can inhibit the formation of aggregates and reduce the grain size of the product. With the increase of ethylene glycol, it fixes the position of cobalt and iron ions in the polymer more durably and the pressure of the decomposition gases will promote the polymerization reaction, resulting in the particle size of products ultra small and uniform. Crystal size of the products obtained directly affects their magnetic properties. Comparatively speaking, with the increase of citric acid coercivity of the product is increased significantly. However, the addition of ethylene glycol can effectively reduce soft agglomeration of particles to refine the grain, which significantly increases the squareness ratio of the product and improves its overall magnetic properties but to some extent inhibits the increase of coercivity. This paper provides some useful basic data for the preparation of high-performance cobalt ferrite magnetic materials, which has good theoretical and substantial applications.In this paper, the innovation is that the preparations of cobalt ferrite are studied by low-heating solid-state sol-gel method and low-heating solid-state self-propagating combustion method respectively for the first time and that optimum conditions have been found out further into preliminarily understanding the effect mechanisms of different process conditions on the crystal structure, generation process and magnetic properties of the product. The impact of ethylene glycol as the dispersant on performances of the product is explored. And it is found out that with the increase of ethylene glycol, it fixes the position of cobalt and iron ions in the polymer more durably and the pressure of the decomposition gases will promote the polymerization reaction and effectively reduce soft agglomeration of particles, resulting in the particle size of products ultra small and uniform, which significantly increases the squareness ratio of the product and improves its overall magnetic properties.