Research Of The Preparation And Physical Property Of CoFe₂O₄-p-MgFe₂O₄ Mixed Ionic Ferrofluids

The CoFe2O4 ferrimagnetic nano-particles and p-MgFe2O4 paramagnetic nano-particles are produced by chemical co-precipitation technology. Then the ferrofluids which have different volume fraction will be synthesized. The CoFe2O4—p-MgFe2O4 binary ferrofluids can be obtained by mixing two types of ferrofluids with a certain percentage and different volume fraction.Through the characterization of magnetic nano-particles for XRD analysis, better CoFe2O4 nano-particle crystallization, while p-MgFe2O4 poor crystallization of nano-particles, but both have similar spherical particle shape.。The results show that two particles have to meet the lognormal distribution by TEM and particle size analysis and the average size of nano-particles CoFe2O4 was 12.76 nm while p-MgFe2O4 average size is 5.58 nm. The atomic ratio of Co and Fe is 1:2 of CoFe2O4 nano-particles, which also is the atomic ratio of samples in experiment. While the atomic ratio of Mg and Fe of p-MgFe2O4 nano-particles is 9:91 instead of experiment samples's atomic ratio 1:2. That may be a part of Mg2+ have been clean out by ion shape with liquor because of no deposition.It can be obtain some phenomena by measuring nano-particles and magnetic properties of magnetic fluids by VSM. It was found that the Coercivity and remanence of CoFe2O4 nano-particles is very small, and CoFe2O4 magnetization is much larger than p-MgFe2O4 magnetization. The p-MgFe2O4 nano-particles are paramagnetic, and no coercivity and remanence. The CoFe2O4 magnetic properties were paramagnetic, and increase along with the increase of volume fraction. The result also show that the magnetization of binary ferrofluids can not simply equal to sum of single magnetic fluid magnetization. Without external magnetic field, some particles could self-assemble into aggregates of closed ring-like structure which have no contribution to the magnetization for the CoFe2O4 ferofluids. In magnetization process of the binary ferrofluids, the closed ring-like structure could partially break. Base on the interaction between two dipoles, it can be judged that there is no magnetic interaction between the CoFe2O4 magnetic system and p-MgFe2O4 magnetic system. Therefor the magnetization behavior of binary ferrofluids can be analysized based on single magnetic fluids.The transmission rate of light though single magnetic fluids and binary ferrofluids under field is measured. The results show that changes of light transmission of CoFe2O4 ferrofluids change with the changes of external field and volume fraction. While the light transmission of MgFe2O4 fluids were not change with the changes of external field and volume fraction. The property of binary ferrofluids were similar to CoFe2O4 fluids under modulation of p-MgFe2O4 nano-particles. Analyzed and discussed the microstructure of magnetic fluids though experiment phenomena. Then research magnetic fluids chain's structure and movement under field.