Magnetic and luminescent properties of bifunctional composite Fe_(3)O_(4)@Y_(2)O_(2)S:Eu^(3+)

As a kind of non-destructive testing method,magnetic particle inspection is widely used in the fields of aviation and high-speed rail.The properties of magnetic fluorescent bifunctional composites,such as fluorescence intensity and magnetic properties,have increasing demands in magnetic particle inspection.Rare earth compounds offer potential as novel materials for fluorescent magnetic bifunctional composites due to their excellent optical properties and extremely narrow emission spectra.In this work,the rare earth fluorescent material Y_(2)O_(2)S:Eu^(3+) was synthesized by solid-state reaction method.Fe_(3)O_(4)nanoparticles prepared by hydrothermal method were uniformly coated on the Y_(2)O_(2)S:Eu^(3+) particles through physical adsorption of surfactants.The obtained Fe_(3)O_(4)@Y_(2)O_(2)S:Eu^(3+) exhibits dark red color under the ultraviolet light.In additio n,X-ray diffractio n,morphology,photoluminescence and hyste resis loop of Fe_(3)O_(4)@Y_(2)O_(2)S:Cu^(3+) were investigated.The luminescence mechanism of Y_(2)O_(2)S:Eu^(3+) is described in detail Fe_(3)O_(4)@Y_(2)O_(2)S:Cu^(3+) displays good paramagnetism and has a good controllability under a magnetic field.The magnetic particle inspection of Fe_(3)O_(4)@Y_(2)O_(2)S:Eu^(3+) was performed using a 4-pole electromagnet and a test piece shim.The magnetic fluorescent bifunctional composite presented in this work can be applied for non-destructive testing.

Research on Parameters Optimization of Rectangular Pole Teeth for Magnetic Fluid Seals

To optimize the magnetic fluid seal design,the single-factor method is usually used to study the e ect of the rectangular pole teeth structure parameters on the sealing capacity of the magnetic fluid seal by current research,and the design formula is obtained.However,the supporting data is too few to make the results universalizable.In this paper,to obtain a wider range of applicable design formulas,a large number of modeling and simulation experiments are conducted using the co-simulation analysis experimental method of MATLAB and COMSOL.The influence of structure parameters of rectangular pole teeth and the coupling e ects of the structure parameters on the sealing capacity of sealing devices has been studied under di erent lengths of pole piece(L_(p))and seal gap(L_(g)).The results explain the influences of tooth height(L_(h)),tooth width(L_(t)),groove width(Ls),and their coupling e ects on the theoretical sealing capacity of magnetic fluid seals,and more widely applicable design formulas for pole teeth structure parameters are given.The design formulas can help to obtain good design parameters directly or reduce the optimization range when the magnetic fluid seals need to be optimized to meet the miniaturization and lightweightrequirements of magnetic fluid sealing devices or improve the sealing capacity under the same seal size.