Piezomagnetic Properties of Fe-based Amorphous Alloy Film and Its Force-sensitive Sensor

Author:Chen Jie

Supervisor:zhu zheng hou


Degree Year:2019





Piezomagnetic force-sensitive film sensor is a new type of sensor in recent years.Fe-based amorphous films are becoming the research hotspot and trends of this type of sensors because of their good physical and chemical properties.For example,the excellent soft magnetic properties.It is of great significance and practical value to study their piezomagnetic properties for the development of high-performance piezomagnetic sensors.In this paper,based on the Fe-based amorphous alloy thin films,we make a comprehensive summarized of the piezomagnetic testing methods and the structures of force-sensitive sensors.On this basis,piezomagnetic properties and environmental stability of Fe-based amorphous alloy thin films are systematically studied by a self-developed piezomagnetic testing system.First,a layer of chemical conversion film was prepared on the surface of amorphous alloy,which effectively solved the packaging problem of amorphous alloy film as the sensitive element of force sensor.Then we demonstrate the chip structure and packaging technology of piezomagnetic force sensor.Finally,the feasibility of this testing method in fatigue detection are preliminarily verified.(1)Based on the open measuring device of piezomagnetic characteristics,a closed testing system was developed,which solved the problem that the testing system is easily disturbed by external environment and improved the sensitivity of the testing system.The distance of the test system affected by the external electromagnetic field was reduced from the original 15 mm to 2 mm.In addition,based on the inductive magnetic compression test method,a direct measurement method that can intuitively and accurately reflect the change of the piezomagnetic properties of the film is developed.(2)The annealing treatment process has a significant influence on the piezomagnetic properties of the Fe-based amorphous alloy film.The optimum annealing temperatures of Fe78Si13B9,Fe73.5CulNb3Si13.5B9 and Fe71.5Cu1Nb3Si13.5B9V2three amorphous alloy films are 400°C,550°C and 300°C,respectively.The SIMax of the corresponding films are 0.5907%,1.2998%and 0.1833%,respectively.Under the same annealing process and test conditions,Fe73.5CulNb3Si13.5B9 film has more excellent magnetic properties.The Fe-based film is sensitive to small stresses,and the stress sensitivity interval of the film is 01.5 kPa.(3)The inductance of Fe73.5Cu1Nb3Si13.5B9 amorphous alloy thin films in the pressure band of 00.6kPa increases significantly with the increase of the compressive stress on the thin films.In other words,it has"positive piezomagnetic effect".When the compressive stressσis 0.6 kPa,the SI value is 5.5%.The ambient temperature has a significant effect on the sensitivity of the piezomagnetic effect.The pressure magnetic effect and sensitivity stability are best in the range of 2030°C.(4)The piezomagnetic effect of the film is related to the resultant directionθof the tensile stress and the compressive stress.When the resultant force direction is the tensile stress along the film direction,the film exhibits a positive piezomagnetic effect,otherwise it exhibits a negative piezomagnetic effect.After the annealing of Fe73.5Cu1Nb3Si13.5B9 amorphous alloy film,the stress state of the film changes,and the characteristics of the piezomagnetic effect also change significantly.When the annealing temperature is larger than 350°C,the type of piezomagnetic effect of the film changes from“positive piezomagnetic effect”to“negative piezomagnetic effect”.(5)An endogenous conversion film with a smooth surface and uniform surface and main components Cu0.86Fe2.14O4 and(Cu0.18Fe0.82)Cu0.82Fe1.18O4 was successfully prepared on the surface of Fe71.5Cu1Nb3Si13.5B9V2 amorphous alloy film by conversion reaction.Correspondingly,the film thickness is reduced by about 68μm.The optimum reaction time for surface treatment is 15 minutes.The film after surface treatment has good wettability with macromolecule resin and is easy to be encapsulated by epoxy resin.(6)The influence of the chip structure and packaging process of the sensor on its test performance was studied.In the range of loading stress between 03 kPa,the sensors of each structural chip have good stress sensitivity and exhibit a positive piezomagnetic effect.When the test frequency is 1 kHz,the magnetic pressure performance of the single-layer structure chip sensor is optimal.The SIMaxax characterization value is 1.696%,and the sensitivity KMaxax is 3.106.When the test frequency is 10 kHz,the magnetic field effect value of the three-layer structure chip sensor is the largest.(7)Composite materials prepared by amorphous alloy flakes and carbon fibers have good force-sensitive characteristics.The piezomagnetic characteristics of the composite material have a distinct monotonic correlation with the applied tensile stress,and the compression magnetic property exhibit high stability.The K---t curve of the material can visually reflect the sudden change of the internal stress of the material.Sensitive patches made from this composite material can reflect the failure of the material to some extent.