Study On Preparation Nanocomposite Two Phase Permanent Magnet

Nano-composite permanent magnet is a new type of rare-earth permanentmagnetic material developed recently. This magnet consists ofmagnetically hard phase and magnetically soft phase coupling in nanometerand posses the potential for high coercive force and high remanence aswell as excellent magnetic properties. Up to now , many ways such as meltspun mechanical alloying(MA) and hydrogenation disproportionationdesorption recombination(HDDR) was used to obtain the magnets, whereasthe magnetic properties can not reach the theoretically predicationcalculation. So diffusion sintering process was proposed and used toproduce Nd2Fe14B/ -Fe two phases permanent magnet. The nano-particleNd ,acicular Fe powder produced by reducing the FeOOH and Fe3B powder madeby mechanical alloying(MA) sintered under some conditions. At same time,the Rietveld method was(X- Ray Diffraction) used to calculate the phaseproportion of the a-Fe and Nd2Fe14B in the samples.First, we prepared the acicular nano- Fe powder and Fe3B powder for thefurther sintering experiment. The results showed that 1) The Nd Fe nano-powders were made by using hydrogen arc plasma method, the averageparticle size about 20nm, and then the powders were coated by AlPO4in orderto prevent from oxidation. 2)the optimal conditions of acicular nano Fepowder prepared by thermal treatment process is : dehydration at 450 and H2 reducing at 350 .the acicular Fe nanoparticles with an averageparticle diameter about 0.1 m and axial ratio 10:1 were made sizedistribution is homogeneous. 3)the better way prepared Fe3B powder byusing MA is that the ratio of ball to raw is 10:1 and milled for 30h inalcohol.In this experiment , size distribution homogeneous Fe3B powderswith a range of 1-10 祄 can be obt ai ned and t o met f ol l owi ng experi ment . - II -ABSTRACT Based on above mention step, the Nd2Fe14B phase has been formed bythe diffusion sintering in micrometer scale and to confirm that this kindof technology can be used to prepare nano-composite permanent magnet;Nd2Fe14B phase was formed through diffusion sintering process, and thecontent of Nd2Fe14phase calculated by Rietveld method at 950 is higherthan at other temperatures , Hc1=4484.2Oe.Both traditional sinteringprocess and spark plasma sintering (SPS) were used to perform furtherexperiment. The result showed that the density of the samples preparedby SPS is larger than the traditional sintered one, and the Nd2Fe14B phasewas formed in nanometer scale too, but magnetic properties are not idealyet. We will have to go on researching it and make some improvements.