Study On Bonded Rare Earth Nanocomposite Magnetic Material

The nanocomposite Nd2Fe14B/α-Fe magnet is a new kind of magnetic material developed since the end of 1980s.This magnet consists of two phases, magnetically hard Nd2Fe14B and soft a-Fe. The rotation of magnetic moments in the a-Fe Phase is controlled by Nd2Fe14B Phase through exchange coupling effect, which gives this magnet high remanence.Melt - spun NdFeB magnetic powders and their bonded magnets were prepared with the optimization of compositions andpreparation techniques. Effects of heat treatment, melt-spunning to NdFeB magnetic powders and magnet were studied. The influence of coupling agent, binders, formation process and the size of NdFeB powder on NdFeB bonded magnet has been systematically studied too.The bonded magnet from rapid quenched NdFeB has been produced, and the influence of the technique factors such as coupling agent, coupling process, powder particle size, binder, solidification process, formation process on its properties has been analysised by means of SEM, magnetic properties analysis, compressive strength measurement, etc.It showed that, magnetic properties of NdFeB increased after the addition of alloy elements with appropriate amount. Different melt-spun speed and different heat treatment could result in different magnetic properties of NdFeB magnets. When the melt-spun speed reached 23 m/s~26m/s, heat treatment temperature was 690℃ and time was 30 minutes, the magnetic properties of magnet alloy got the best.The effects of preparation techniques to properties of bonded NdFeB magnets have been studied too. These techniques included bonding solvent, solidifying solvent, solidifying techniques, magnet density and magnetic powder granularity.Solid epoxy resin with the low epoxy value is better than liquid epoxy resin to the magnetic performance, and the content is 2%-3%wt will do good to improve the magnetic characteristics of the bonded NdFeB magnet. So if compound the epoxy resin and the magnetic powder binders as the new binder, the result of the test is greatly better than the former test.It has shown that if the combination with higher magnetic and mechanic properties of the bonded magnet is wanted, titanate coupling agent is more proper than silane coupling agent , at the same time ,the result show that the particle size and distribution of rapidly quenched NdFeB magnetic powder affect obviously on the magnetic property of the bonded NdFeB magnets. From the analysis of the relationship between different particle size and the magnetic properties, the proportion of the particle size with 100 and200 is 3:2,can get the better results.It has shown that the combination with higher magnetic and mechanic properties of the bonded magnet is presented on the basis of proper curing process temperature, 120℃ to 150℃ , and the curing agent is proper mold press, 500~600MPa, keeping press time is 18~20 seconds.At last, some suggestions for further research for NdFeB magnets were given.