| Since the advent of the Fe-based amorphous,it has become a research hotspot due to the low cost,excellent magnetic,mechanical and corrosion resistance properties.At present,the preparation and researches of Fe-based amorphous are mainly concentrated on ribbon,filament and bulk Fe-based amorphous,whereas relatively few researches focus on the properties and applications of micro-nano Fe-based amorphous.Therefore,strengthening the preparation of various types of micro-nano Fe-based amorphous,developing the excellent properties and expanding the application field of micro-nano Fe-based amorphous,and carrying out interdisciplinary research on Fe-based amorphous and other scientific research fields,are of great significance.First,Fe78Si9B13 ribbon amorphous particles,Fe78Si9B13 spraying amorphous and Fe3O4 particles were prepared by ball milling method,atomization method and chemical coprecipitation method,respectively.The three kinds of particles were dispersed in silicone oil after surface modified by oleic acid to prepare the silicone oil-based magnetic fluids,respectively.Fe78Si9B13 ribbon maintains amorphous structure after being milled for 24 h and 84 h.Fe78Si9B13 spraying particles are regular spheres.With the milling time increasing(after being milled for 24 h,60 h and 84 h),the disorder degree of the atomic arrangement increases and the amorphous characteristic of the particle enhances.After being milled for 84 h,the saturation magnetization of Fe78Si9B13 spraying amorphous particles and Fe78Si9B13 ribbon amorphous particles are 167.01 emu g-1 and 169.48 emu g-1,respectively,which is about 4 times that of as prepared Fe3O4 particles.Meanwhile,the amorphous particles have excellent soft magnetic properties.The saturation magnetization of magnetic fluids with Fe78Si9B13 amorphous particles is also approximately 4 times that of the magnetic fluids with Fe3O4 particles due to the high saturation magnetization of amorphous particles.Researches on viscosity-temperature properties of magnetic fluids show that when applied magnetic strength is 1100 Gs,the viscosity of magnetic fluids with Fe78Si9B13 amorphous particles is about 3.6 to 3.3 times that of magnetic fluids with Fe3O4 particles.Researches on magnetorheological properties of magnetic fluids indicate that the shear viscosity decreases with increasing shear rate,which is called shear thinning behavior.The yield stress of magnetic fluids obtained by linear extrapolation method indicates that the yield stress of magnetic fluids with Fe78Si9B13 amorphous particles is about a hundred times higher that of magnetic fluids with Fe3O4 particles.For example,the yield stresses of magnetic fluids with Fe78Si9B13 and Fe3O4 particles are 4.85 kPa and 36 Pa at 250 kA m-1,respectively.When under an applied magnetic field,the suspended particles will be polarized and the dipole-dipole interaction between particles causes the formation of linear chains,which are parallel to applied magnetic field.With the magnetic strength increasing,the force between particles becomes stronger.Under the same magnetic strength,Fe78Si9B13 amorphous particles are more easily magnetized than Fe3O4 particles.The chain-like structures of magnetic fluids with Fe78Si9B13 particles are more difficult to break than Fe3O4 particles,which can produce greater shearing force,torque and braking force.Second,FeB amorphous particles with mean diameter about 190 nm were obtained by chemical reduction method.The FeB amorphous particles were dispersed in liquid Ga85.8In14.2 alloys after surface modified by SiO2 to prepare the metal-based magnetic fluids.The onset and end temperature of the two stages crystallization deduced from DSC curves provide a basis for the selection of the annealing temperature of FeB and FeB@SiO2 amorphous particles.After annealing at 350?,the FeB particles remain amorphous,demonstrating the occurrence of structural relaxation without phase transition during the annealing process.After annealing at 450? for 30 minutes,a-Fe phase precipitates.After further annealing at 500? for 30 minutes,the intensity of crystalline peaks of a-Fe phase enhances.The structural changes of FeB@SiO2 amorphous particles have the similar variance law with FeB amorphous particles in various annealing temperatures.The saturation magnetization of FeB and FeB@SiO2 amorphous particles is 131.5 emu g-1 and 106.9 emu g-1,respectively.The saturation magnetization of FeB amorphous particles is approximately 2 times that of the saturation magnetization of Fe3O4 particles.The saturation magnetization of FeB@SiO2 amorphous particles is about 81.3%of the saturation magnetization of FeB amorphous particles due to the coating of the non-magnetic SiO2.After annealing at 450?,the saturation magnetization of FeB particles increases due to the structural relaxation and the precipitation of a-Fe phase.After annealing at 500?,the saturation magnetization of FeB particles decreases due to the increasing of element B concentrated in a-Fe phase and the appearance of intermetallic compounds.The viscosity-temperature properties and magnetoviscous properties of the magnetic fluids are researched.The apparent viscosity of magnetic fluids changes rapidly and is the quadratic function of magnetic strength within the scope of the test.The curves of the increasing stage of magnetic field coincide well with the decreasing stage of magnetic field,manifesting that the magnetic fluids have excellent stability.At low magnetic strength(below 477 Gs),the apparent viscosity of magnetic fluids varies little with temperature.At high magnetic strength(higher than 477 Gs),the apparent viscosity changes a little with temperature when the temperature is lower than 300?,whereas the viscosity decreases obviously with increasing temperature when temperature increases over 300?.Ga85.8In14.2-based magnetic fluids with FeB@SiO2 amorphous particles exhibit excellent high temperature performances,which have potential applications in heat conduction,electrical conduction and high temperature applications.In this work,amorphous particles and liquid Ga85.gIn14.2 alloys are applied in preparing magnetic fluids,putting forward a new thought for preparing magnetic fluids.Finally,hollow porous iron-borate particles(HP-FeBO-Ps)as anode for lithium-ion batteries(LIBs)were synthesized by removing AI atoms from FeAIBO amorphous with NaOH solution.HP-FeBO-Ps have large specific surface area and amorphous characteristics.HP-FeBO-Ps as anode for LIBs show excellent electrochemical performance,high Coulombic efficiency and ultralong cycle life.HP-FeBO-Ps anode delivers outstanding reversible capacity of 1170 mAh g-1 after 360 cycles at 100 mA g-1 and 1160 mAh g-1 after 750 cycles at 200 mA g-1.The reversible capacity of HP-FeBO-Ps anode is about 1107,961,863,779 and 694 mAh g-1 at 200,500,1000,1500 and 3000 mA g-1,respectively.Even though the current density is amplified 15-fold,the capacity retention at 3000 mA g-1 is 62.7%of the capacity at 200 mA g-1.And when current density is reduced back to 500 and 200 mA g-1,the capacity can almost recover to the original value.The reversible capacity of HP-FeBO-Ps anode can still remain about 600 mAh g-1 even after 3500 cycles at 2000 mA g-1.HP-FeBO-Ps anode has higher reversible capacity and longer cycle life than that of the reported iron-based oxides anodes.The special hollow porous structure of amorphous iron-borate particles attribute to the excellent electrochemical performance,offering efficient electron transport and Li+ diffusion paths and buffering the volume change and structural strains during the discharge-charge processes.The large specific surface area of HP-FeBO-Ps anode composed by extremely tiny size particles can facilitate good contact between anode and electrolyte and provide more reaction sites.Hollow porous spherical architecture can provide structural support,which effectively prevents aggregation of particles and buffers the volume change,then protects the anode from pulverization.What's more,the amorphous characteristics of HP-FeBO-Ps can accelerate Li+ diffusion and reaction kinetics,and can relax volume change during the discharge-charge processes. |
PDF Full Text Request