Fabrication For Magnetic Powder Materials With Nanosize And Magnetic Fluids

In this article, the preparation of magnetic fluids was the center of investigation. According to the makeup of the magnetic fluids, for which the process of preparation was done as follow, first, the fabrication of magnetic powders with nanosize about 10nm; second, the disposal for the surface of magnetic powders; finally, the preparation of magnetic fluids.Firstly, magnetic powders with small nanosize were fabricated. According to abundant research in experiment, a better method, phase transformation at low temperature, was found using for the synthesis of magnetic powders with small nanosize about 10nm. By means of the control for the order of temperature-raising in the process of synthesis, pre-temperature-raising method was of more superiority in the preparation of magnetic powders with small nanosize about 10nm. And a series of magnetic powders with nanocrystalline structure was synthesized. In addition, in the process of the samples fabricated, a little of matter with Zn2+ ion was added in order to make Zn2+ ions enter the interspace of tetrahedron for the samples with spinel structure. Through the super-exchange reciprocity among the different ions in the spinel, the magnetization of the samples prepared could be raised in large degree. So samples of magnetic powders with nanosize about 10nm were chosen suitable for the preparation of magnetic fluid. Secondly, the disposal for the surface of magnetic powders, which met the requirements of the preparation of the magnetic fluids, was done so as to reduce the surface energy of the magnetic particles, and thus to prevent two magnetic particles from approaching which might lead to congregation and sedimentation of particles in carried liquids. The effects of the disposal for the surface of magnetic powders were evaluated by UV spectra apparatus,researching the impacts about vales of pH, temperature, time and compound surfactants on the effects of the disposal for the particle surface. So the best conditions on the effects of coating for particle surface were achieved. Finally, magnetic particles, which were coated best, were dispersed uniformly in the carried liquids by means of transition liquids, and thus magnetic liquids were formed. In the experiment, DOP was used for carried liquids. Because its freezing point and boiling point were at -50℃ and 384℃ respectively, so it can endure both a certain lower temperature and higher temperature, with a wide range of temperature application. In the paper, investigation was done in the impacts about transition liquids and temperature on the stability of magnetic fluids as well as the relation between liquid-solid ratios and viscosity of magnetic fluids. The results of experiment indicated that temperature had better be controlled properly in the preparation of magnetic fluids, of which, otherwise, the stability may be influenced if the temperature is much higher. And the viscosity of magnetic fluids increases with the increase of quantity of particles in the carried liquids.Each step in the preparation of magnetic fluids was investigated in more detail, with characterization and analysis done accordingly, and some more valuable data were obtained. Especially, meaningful quest was done in the aspects of preparation for magnetic particles with nanosize and evaluation for their surface coating effects.