| The development of the society need to high performance magnetic materials, multi-function direction,and nanometer magnetic material can have a better magnetic and no other function block nanometer magnetic materials.Face-centered cubic(FCT) phase FePt has grown with high magnetocrystalline anisotropy,super paramagnetic critical size for 2-4 nm,good chemical stability,and therefore can serve as.a good nanoscale magnetic materials.Nowadays,FePt nanoparticle preparation materials mainly divided into two broad categories:physical method preparation of FePt film and chemical synthesis of FePt nano particles.But the biggest problem with the preparation of FCT FePt nano-materials are materials reunion and sintering phenomena occur during annealing.To this end, there are two main strategies the physical preparation of nano FePt,one is by lowering the annealing temperature,such as by doping with Ag,Cu,Au,etc.and the other is to reduce the annealing time,such as fast annealing,the laser annealing and the like.Also FePt nano-film can grow in a strong magnetic field orientation and a suitable substrate.But physically prepared FePt ordered out is not high, less than 0.7.There are two main method of chemically synthesized FePt nanoparticles,one is the chemical synthesis of a face-centered tetragonal (FCC) phase nanoparticles and then salt bath annealing,and another is outside the FCC FePt nano-particles coated with a high melting point substance layer to prevent sintering and agglomeration during annealing,such as MgO,SiO2 etc.Advantages chemical synthesis FCT FePt particles are size,shape are well controlled, high order,may be greater than 0.8.But chemical preparation step FCT FePt slightly.This article was prepared for chemical synthesis FePt nanoparticles not more experimental steps,and synthesized nanoparticles also require high temperature annealing can lead to particle agglomeration, just direct preparation FCT phase FePt nanoparticle-step solid-phase sintering method:direct use of iron acetylacetonate and acetyl acetone platinum and sodium (or potassium) milling mixed,then direct calcination FCT preparation of FePt nanoparticles.Prepared by this method of FePt nanoparticles use VSM,XRD,TEM analysis were characterized by means of magnetic properties,crystal structure,morphology and structure.The main contents and results are as follows:1. By adjusting the molar amount of Fe,Pt precursor, when Fe,Pt elements in 1:3 and 3:1 coercivity prepared nanoparticles is low,XRD Characterization prepared and were FePt3 Fe3Pt;and found when the Fe,Pt ratio isl:1 prepared FePt nanoparticles have good magnetic properties,the particles are prepared FCT structure.2. Confirm Fe,Pt precursor ratio is 1:1, by adjusting the amount of NaCl, in contrast to the different proportions of NaCl and Fe,Pt precursor is prepared by mixing the FePt magnetic nanoparticles and morphology and structure analysis,shows that when NaCl and Fe,the ratio of Pt precursor is no greater than 2000:1,can be prepared FePt nanoparticles FCT structure,and with the decrease in the proportion of sodium chloride,the average particle size is gradually increased,the coercive force is gradually increase/when the molar ratio of sodium chloride and FePt at 300:1,the coercivity reaches 22KOe.3. Magnetic particles,the calcination temperature at 750?,the maximum magnetic contrast calcined at different temperatures when prepared,with the decrease of the calcination temperature,the coercive force is gradually decreased,the average particle size is decreased,and low when calcined at 400? still prepared FePt nanoparticles FCT phase,the coercive force 5KOe.In this paper one solid phase sintering method preparedFePt nanoparticles,without first chemical synthesis FCC phase FePt nanoparticles can be prepared directly FCT phase FePt nanoparticles;compared with core-shell structure (SiO2,MgO outside layer protection) salt can effectively prevent excessive sintering FePt grains grew FePt performance does not degrade or destroy FePt removal of the protective layer integrity. |
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