Synthesis And Properties Of ?"-Fe₁₆N₂ Nanoparticles Obtained By Low Temperature Nitridation Reaction

Due to its giant saturation magnetization,moderate magnetic anisotropy and other physical connotations,?"-Fe₁₆N₂ has great potential in magnetic recording and magnetic sensor materials,which has seen rapidly increasing levels of attention in academia over the past years.In this paper,we took nano Fe₃O₄ powder as raw material,synthesis of nano?"-Fe₁₆N₂ powder by low temperature nitridation in a tube furnace.Then discuss the preparation process of the?"-Fe₁₆N₂ phase,including parameters of hydrogen reduction and ammonia nitrigen and its magnetic property were studied,so the optimum synthesis conditions were firmed.After that,the preparation technology of SiO₂ coating with?"-Fe₁₆N₂ was then studied,also the magnetic properties and stability of?"-Fe₁₆N₂ phase were discussed.Specific research contents and conclusions are shown as following:?1?First of all,through changing the parameters in the experiment to prepare a higher purity?"phase by low temperature nitridation.The optimum preparation conditions were as follows:the particle size of Fe₃O₄ is 20 nm,and the Fe₃O₄ powders were reduced at 400?for about 4 hours to form?-Fe under a hydrogen gas.The reaction gas is changed to ammonia gas at 170?nitriding for 16 h to obtain?"-Fe₁₆N₂ phase,which is about 59.8 wt.%,and its coercivity is above 750 Oe,saturation magnetization of?"-Fe₁₆N₂ phase is about 207 emu/g.?2?Second,using the effect of temperature on magnetic properties and draw the M-T curve through the VSM test,the magnetization will change at the phase decomposition temperature.The sudden discontinuous change in magnetization at around 250?can be explained as being due to the decomposition of?"-Fe₁₆N₂.The as-prepared sample was placed in the tube furnace under Ar atmosphere and heated under the specific temperature range.Draw conclusions based on XRD and VSM analysis:the?"-Fe₁₆N₂ nanoparticles are stable up to 225?,and it almost decomposes into?-Fe and??-Fe₄N under 250?.?3?Last,using St?ber method,the raw material of nano Fe₃O₄ coated with a layer of protective layer of SiO₂,and the prepared samples were further tested by low temperature nitridation reaction.So,the optimum preparation conditions could be obtained by changing the parameters in the experiment.High purity and well-distributed?"-Fe₁₆N₂ powder can be obtained when the results in the experiment are TEOS 0.01 ml,NH₄OH 1 ml,stirring temperature 30?,hydrogen reduction at400?for 4 h,and nitridation at 170?for 12 h.The yield of the?"-Fe₁₆N₂ was about 80.6 wt.%and exhibited saturation magnetization of about 138.223 emu/g at room temperature.