Preparation Of FePt Nanoparticles By Water-soluble Salt Isolation

FePt nanoparticles are widely used in magnetic recording materials and catalysis due to their high magnetic anisotropy and excellent chemical stability.The chemically ordered L1₀phase FePt nanoparticles have ultra-high magnetocrystalline anisotropy and extremely small superparamagnetic critical size,which is the first choice for next-generation ultra-high density recording media.Therefore,FePt,especially L1₀ phase FePt nanoparticles preparation technology has become the focus of research in this field in recent years.The preparation of L1₀-phase FePt needs to be annealed at a high temperature of more than 700°C,and it is easy to sinter and grow the nanoparticles,which has also become a technical bottleneck for the preparation of small-diameter and highly dispersed L1₀-FePt nanoparticles.In this paper,the FePt nanoparticles are prepared by the impregnation method using water-soluble salt particles as a sacrificial carrier.The use of water-soluble salts as a separation phase suppresses the sintering and growth of FePt nanoparticles at high temperature,which is conducive to the preparation of fine and narrowly distributed particles L1₀-FePt nanoparticles.In this paper,Fe(NO₃)₃ and Fe(acac)₃ were used as iron sources to prepare an impregnating solution with H₂PtCl₆.The proportion of FePt raw materials,solvent type,impregnating solution concentration,surfactant and other factors on the size appearance and magnetic properties,and explored the catalytic properties of carbon-containing FePt materials.The main conclusions are as follows:Using Fe(NO₃)₃ and H₂PtCl₆ as raw materials,n-butanol as a solvent,sodium chloride as a separating phase and sacrificial carrier,L1₀-FePt nanoparticles were synthesized directly at750?.The study found:The phase composition of FePt nanoparticles is related to the ratio of raw materials.When the molar ratio of Fe(NO₃)₃ and H₂PtCl₆ is 2:1,a pure L1₀-FePt phase can be obtained;FePt nanoparticle size decreases with decreasing concentration of impregnating solution;Adding CTAB and oleic acid can reduce the size of FePt nanoparticles and improve the uniformity,and the particle size can reach 6.4nm and 6.9nm respectively;The smaller the FePt nanoparticle size,the smaller the coercive force.Using Fe(acac)₃ and H₂PtCl₆ raw materials,isopropanol as the solvent,and sodium chloride as the sacrificial carrier,L1₀-FePt nanoparticles with an average particle size of about6.4 nm,excellent uniformity and dispersibility were prepared.Research shows:When the molar ratio of Fe(acac)₃ and H₂PtCl₆ is 3:1,L1₀-FePt nanoparticles with Fe and Pt atomic ratio of 1:1 can be prepared;Acetone,ethanol,isopropanol and n-butanol as solvents have little effect on particle size;The higher the concentration of the impregnating solution,the larger the FePt nanoparticles prepared;SDBS additives have significantly improved the size and crystallinity of nanoparticles;The coercive force of L1₀-FePt nanoparticles with an average particle size of6.9nm can reach 587.83Oe.In this paper,the FePt@C material was prepared by one-step impregnation of water-soluble salts,and its effect on the electrocatalytic oxidation of methanol was studied.Research shows:After the introduction of ethyl cellulose,FePt@C material can be synthesized in situ,and the FePt nanoparticles have a small size and good dispersion on the carbon matrix;Properly increasing the proportion of iron can effectively enhance the electrocatalytic activity of methanol;The iron-platinum ratio of Fe_5.7Pt_4.3 has the best catalytic activity and the best durability.