| At present,most of the sensor applications in the market are discrete,and can not be used in some harsh environments.Temperature and pressure are the two attributes that most need real-time monitoring in the production process of the manufacturing industry.In order to respond to the"made in China 2025"and meet the needs of China's intelligent manufacturing industry,this paper prepares a thermal resistance/piezoresistance metal film integrating sensing and protection functions and a composite protective multi-layer coating,which is prepared on the surface of the substrate,so that it can meet the requirements of wear resistance while meeting the in-situ test temperature or pressure.The main research contents and conclusions of this paper are as follows:(1)W/AlTiN thermal resistance film and composite protective coating was prepared.the preparation process was optimized,and its thermal resistance and surface mechanical properties were studied.Firstly,the W thermal resistance film(temperature sensing film)is prepared on the insulating substrate by magnetron sputtering,and then the AlN insulating layer and AlTiN wear-resistant protective coating are magnetron sputtered on its surface,The effects of different deposition temperatures(200?to 400?)and different AlTiN coating thickness(270 nm to 1.6?m)on the structure and mechanical properties of AlTiN coating and its mechanism were studied,and to explore its effect on the thermal resistance of W films.The changes of thermal resistance and surface mechanical properties of annealed multilayer samples were studied.The thermal resistance of W films can be improved by doping an appropriate amount ofTiin W,Changing the ion source auxiliary current(0 to 8 A)during the deposition of WTi films(6.8 at.%Ti,93.2 at.%W),and the effects of ion source assisted deposition current on its structure and thermal resistance were studied.Increase the thickness of WTi film(from 400 nm to 870 nm),and study the changes of thermal resistance of WTi film with different thickness.Finally,the AlTiN coating was deposited on the surface of WTi film by arc deposition.The changes of thermal resistance of samples before and after deposition of AlTiN coating were compared,and the mechanical properties of multilayer structure were studied.(2)W/AlTiN thermal resistance film and composite protective coating was prepared.When the deposition temperature of AlTiN coating reaches 400?,there will be a small amount of body centered cubic?-W turn into face centered cubic?-W.However,it has little effect on the TCR(resistance temperature coefficient)of W film,which is reduced by 0.06×10-3/?.When the thickness of AlTiN coating is greater than 900 nm,the TCR of W film decreases significantly from 1.17×10-3/?down to 0.90×10-3/?,the thermal resistance decreases because the thickness of AlTiN coating increases,the residual compressive stress of AlTiN increases,the phonon vibration intensifies and the electron transmission is blocked in the W lattice under pressure.Therefore,the sensitivity of temperature rise resistance changes decreases,resulting in the decline of thermal resistance.The thermal resistance of annealed W films can be further improved due to the release of residual stress(1.32×10-3/?at 300?).The relationship between resistance and temperature before annealing tends to be linear,with a linear correlation of more than 98%,while it is exponentially correlated after annealing,and more consistent results can be obtained by repeated temperature resistance relationship tests,indicating that it has good thermal loading cycle stability.The deposition temperature of AlTiN coating has the greatest influence on the mechanical properties of multilayer structure.The lower the deposition temperature of AlTiN coating,the better the mechanical properties.When the deposition temperature of AlTiN coating is 200?,the hardness is 21.6±2.6 GPa and the elastic modulus is 165±5 GPa.When the thickness of WTi film(6.8 at.%Ti,93.2 at.%w)is 400 nm,the TCR value is 1.84×10-3/?.In this thesis,the effect of ion source assisted deposition on the thermal resistance of WTi films is studied.The results show that increasing the ion source assisted deposition current will reduce the deposition rate and TCR value of WTi films.When the ion source assisted deposition current is 8 A,the deposition rate of WTi films will be reduced from 8.8 nm/min(0 a)to 6.7 nm/min,and the TCR value will be reduced to 0.77×10-3/??If the thickness of WTi film is increased to 870 nm,the TCR value increases to 1.92×10-3/?,increasing the thickness of WTi film will reduce the bulk resistance by about 0.12?.After the AlN insulating layer was prepared on the surface of WTI film,it was deposited by arc evaporation again for 1.2?m thickness of AlTiN coating,the thickness of WTi film is reduced to 700 nm,and its TCR value is reduced to 1.79×10-3/?due to residual compressive stress.The hardness and elastic modulus of AlTiN coating reached 29.4±4.0 GPa and 387±50 GPa respectively.(3)CuMnNi/AlTiN piezoresistive film and composite protective coatingwas prepared,the preparation process was optimized,and its piezoresistive properties and surface mechanical properties were studied.The thickness of CuMnNi thin films prepared in this paper is 400 nm,which are prepared by magnetron sputtering.Firstly,the effect of substrate surface roughness on the piezoresistive properties of CuMnNi films was investigated.It is successively compared with the matrix with surface roughness Ra 3.2 and the matrix with surface roughness less than 10 nm.CuMnNi film was deposited on the substrate with surface roughness of Ra 3.2,and then AlN and AlTiN coatings were magnetron sputtered on the surface of CuMnNi film.The changes of piezoresistive coefficient of samples before and after deposition of AlTiN coating and the mechanical properties of multilayer samples after deposition of AlTiN coating were compared.Then,CuMnNi film was deposited on the substrate with surface roughness less than 10 nm,and then AlN was sputtered on the surface of CuMnNi film by magnetron sputtering.AlTiN coating was prepared by cathodic arc evaporation.The deposition bias voltage(0 to 200 V)and the thickness of AlTiN coating(400 nm to 1.5?m)were changed to study the changes of piezoresistive properties of samples under different bias voltages and different thicknesses of AlTiN coating.(4)CuMnNi/AlTiN piezoresistive film and composite protective coatingwas prepared.The results showed that the sample with high substrate surface roughness(Ra 3.2)had poor repeatability in piezoresistive performance test,and its piezoresistive coefficient was about 7×10-4/GPa,and for multiple CuMnNi/AlN/AlTiN multilayer samples with AlTiN thickness less than 650 nm,the piezoresistive coefficient is also about 7×10-4/GPa,indicating that when the thickness of the surface AlTiN wear-resistant protective coating does not exceed650 nm,the piezoresistive properties of CuMnNi are not affected.The mechanical property test results are as follows:the hardness is 15.2±3.0 GPa and the elastic modulus is 364±163 GPa.If CuMnNi film and CuMnNi/AlN/AlTiN multilayer are prepared on the substrate with low surface roughness(less than 10 nm),the results show that the piezoresistive test of CuMnNi film prepared on the mirror substrate has good repeatability and high piezoresistive coefficient,about 14.9×10-4/GPa,the higher the bias voltage,the better the interface bonding,the finer the grain of AlTiN coating and the smaller the grain boundary.For the sample with deposition bias of 0,the structure and thickness of CuMnNi film are greatly affected,and the piezoresistive coefficient is also low,only 9.2×10-4/GPa,samples with different deposition time of AlTiN coating also have the same law.The better the interface bonding,the smaller the influence on the thickness and structure of CuMnNi film,the higher the piezoresistive coefficient,and the highest piezoresistive coefficient is 13.6×10-4/GPa,the mechanical properties are also good,and the hardness and elastic modulus are 30.4±1.6GPa and 466±58 GPa respectively.(5)Water bath heating and experimental exploration of thermal/piezoresistance film and composite protective coating.Firstly,the thermal resistance film and composite protective coating are used for water bath heating test,and the temperatures of boiling alcohol and boiling deionized water are tested respectively.Then the error is calculated,and the error is about 5%.Then the scratch test and exploration test are carried out on the thermal/piezoresistance film and composite protective coating,and the change of resistance value is recorded in real time,so the change of instantaneous temperature and pressure is calculated.The results show that the instantaneous temperature change of contact point is greatly affected by the load change,from 0.53?under the initial 5 N load to 93.9?under15 N load,while the pressure change is less affected by load and rate,10 N The maximum average stress of scratch test at 10 mm/min is 0.09 GPa,and the maximum average pressure of scratch test at 15 N and 2.5 mm/min is 0.50 GPa.Combined with simulation,the test results at 10 N are close to the simulation results.Then,the linear reciprocating friction and wear exploration test is carried out for the thermal/piezoresistance film and composite protective coating.In order to prevent the coating from being damaged,a smaller load and frequency are selected to record and analyze the change of resistance value in the process of friction and wear.The results show that with the change of load and frequency,there is no obvious change of resistance value in the thermal resistance film and composite protective coating in a small range,indicating that in the process of friction and wear,There is no obvious temperature change on its surface,while the resistance value of piezoresistive film and composite protective coating samples changes back and forth,and its motion trajectory and friction coefficient change are also oscillatory,but the change of effective stress value is slightly larger than the simulation value,and the change of stress in simulation is small.The specific reasons need to be further explored and studied.(6)Based on the test equipment in the experiment,the actual test results and relevant theoretical formulas are used to calculate.The minimum range of measurable temperature of W thermal resistance film sample is 0.043?,the minimum range of measurable temperature of WTi thermal resistance film sample is 0.024?,and the temperature measurement range is from room temperature to 400?.The test pressure range of CuMnNi piezoresistive film is 0 to 2400 N.The maximum error in the measurement of thermal resistance or piezoresistive film is only about 5%. |
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