JP3968430B2 - Lead zirconate titanate fiber, smart board using lead zirconate titanate fiber, and actuator and sensor using smart board - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lead zirconate titanate (hereinafter referred to as “PZT”) fiber that can be used in structures such as buildings, automobiles, ships, and aircraft, a smart board using the PZT fiber, an actuator using the smart board, and With regard to sensors, in particular, PZT fiber, smart board using PZT fiber, and smart that can prevent fatigue destruction due to vibration of the above structure, prevent unstable vibration, improve the reliability of the structure by improving riding comfort and reduce maintenance costs The present invention relates to an actuator and a sensor using a board.
[0002]
[Prior art]
In recent years, research and development of smart boards that combine sensors, actuators, and structures have attracted attention from industry as the final form of structural materials. Among them, the piezoelectric material has two effects, a positive piezoelectric effect that converts mechanical input into electrical output, and a reverse piezoelectric effect that converts electrical input into mechanical output. Research to embed the structure into the structure is being carried out vigorously. Research into embedding a piezoelectric material in a fiber shape into a composite material has been conducted domestically and overseas mainly in the US MIT and has already been used for skis and tennis rackets.
[0003]
[Problems to be solved by the invention]
However, conventionally used ceramic fibers require a comb-shaped electrode to be driven, and are expensive. Also, those using PZT-based piezoelectric materials have the problem of being hard and easy to break, which is a characteristic characteristic of ceramics. There is a problem that the material using the polymer piezoelectric material is not easily broken, but the performance itself is inferior to that of the PZT type piezoelectric material.
[0004]
An object of the present invention is to solve the above problems by combining PZT ceramics with high piezoelectric effect, heat-resistant metal wires such as titanium wire and platinum, and conductive composite materials.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present inventors have made extensive studies and have come to achieve the present invention.
That is, the present invention is an invention shown below.
(1) A lead zirconate titanate fiber formed by coating or laminating a lead zirconate titanate crystal on the surface of a metal wire as a core wire.
(2) The lead zirconate titanate fiber according to (1), wherein the metal wire is a titanium wire.
(3) The lead zirconate titanate fiber according to (1), wherein the metal wire is a heat-resistant metal wire, and the heat-resistant metal wire is made of platinum, stainless steel, or nickel.
(4) The lead zirconate titanate fiber according to any one of (1) to (3), wherein the surface of the metal wire is coated with a lead zirconate titanate crystal by a hydrothermal synthesis method.
(5) The lead zirconate titanate fiber according to any one of (1) to (3), wherein the surface of the metal wire is coated with a lead zirconate titanate crystal layer by an extrusion molding method.
(6) A smart board formed by embedding the lead zirconate titanate fiber according to any one of (1) to (5) in a conductive composite material layer.
(7) The smart board according to (6), wherein the conductive composite material layer is made of carbon fiber reinforced plastic.
(8) An actuator using a smart board, wherein a voltage is applied between the lead zirconate titanate fiber and the conductive composite material layer of the smart board according to (6) or (7) .
(9) A sensor using a smart board, characterized in that a voltage detector is connected to, for example, one end of the smart board described in (6) or (7).
(10) A method of using the smart board according to (6) or (7) as an actuator or a sensor, wherein a voltage is applied between the lead zirconate titanate fiber and the conductive composite material layer. Way .
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
In the embodiment of the present invention, a PZT crystal film having an extremely large piezoelectric effect is produced on the surface of a metal wire by a hydrothermal synthesis method. The fact that PZT polycrystalline films can be formed directly on Ti substrates using hydrothermal synthesis was reported by Oba et al. Of Tokyo Institute of Technology in 1991 (JJAP (Japan Society of Applied Physics), "Preparation of Lead Zirconate Titanate Thin Film by Hydrothermal method "vol. 31, No. 9B Sep 1991 pp. 2174-2177), and is used for tactile sensors and vibration-type gyro sensors.
In this hydrothermal synthesis method, lead nitrate, zirconium chloride oxide, and titanium tetrachloride are mixed in a potassium hydroxide solution (usually an aqueous solution) and placed in a pressure vessel together with a titanium substrate on which a film is formed. By maintaining the pressure vessel at a high temperature and high pressure, Pb ²⁺ , Zr ⁴⁺ and Ti ⁴⁺ ions in the solution react with the titanium substrate, and grow as a PZT polycrystalline film on the substrate surface. The ratio of Pb, Zr and Ti of the PZT polycrystalline thin film to be produced can be controlled by the ratio of ion concentration in the aqueous solution. Moreover, the film thickness of the polycrystalline film produced by repeating this reaction can be controlled.
In the hydrothermal synthesis method, for example, a titanium substrate to be formed into a solution obtained by synthesizing lead nitrate, zirconium chloride oxide, titanium tetrachloride and potassium hydroxide is put into a reaction. Each material is ionized in an aqueous solution, and a PZT crystal grows on the surface of the Ti substrate by the following reaction formula (1).
^{Pb 2+ + (1-x)} Zr 4+ + xTi 4+ + 6OH - →
Pb (Zr _1-x Ti _x ) O ₃ + 3H ₂ O …… (1)
Here, the value of x is 0 <x <1, but when x = 0.48, the PZT ceramic exhibits extremely high piezoelectricity.
PZT-based piezoelectric materials have extremely high piezoelectricity when the mixing ratio of Pb, Zr, and Ti is 1: 0.52: 0.48, respectively.
The film-forming reaction has two steps: a nucleation reaction and a crystal growth reaction. In the nucleation reaction, titanium is supplied from a titanium substrate, so a titanium wire is added to a mixed solution of lead nitrate, chlorinated zirconium oxide, and potassium hydroxide. In an autoclave, the film-forming reaction is usually performed at 180 ° C. to 120 ° C. for 24 hours to 48 hours. Thereafter, in the crystal growth process, lead nitrate, zirconium chloride oxide, titanium tetrachloride and potassium hydroxide are mixed so that the molar concentration of Pb, Zr, and Ti becomes a predetermined ratio so as to obtain the target compound of formula (1). The titanium wire after the nucleation process is added, and the reaction is carried out in an autoclave at 140 to 100 ° C. for 24 to 48 hours. By repeating this crystal growth process, an arbitrary PZT film thickness can be obtained. The value of x can be controlled by the blending ratio of Pb: Zr: Ti of the solution added therein.
Advantages of producing PZT polycrystalline thin film by hydrothermal synthesis method are as follows: (1) A film can be formed on a three-dimensional structure for film formation in aqueous solution. (2) A thick film is obtained by repeating the growth process. (3) Polarization treatment is not required (natural polarization) (4) PZT thin film can be produced at a low temperature of about 150 ° C, so thermal stress generated during production compared to other methods It can reduce the influence of.
[0007]
In addition to the above hydrothermal synthesis method, an extrusion molding method can also be used as a method for producing a fiber having a metal wire surface coated with a PZT crystal layer. That is, a PZT fiber molded body containing a metal core is first prepared by co-extruding a PZT powder with a binder and water and kneaded together with a platinum fine wire from a nozzle attached to an extrusion molding machine, This is a method of forming a fiber coated with a PZT crystal by drying and heating at 400 ° C. to 600 ° C., followed by a binder removal process, followed by sintering at a high temperature of 1100 ° C. to 1200 ° C.
Here, the Pb, Zr and Ti sources may be solutions of lead nitrate, zirconium chloride oxide and titanium tetrachloride, respectively. However, these conditions can be changed depending on the purpose of application such as actuator use, sensor use, etc., and also depending on the preparation temperature, sample size, solution volume, and the like.
In the extrusion molding method, a platinum fine wire is used as the core metal wire. However, in order not to impair the characteristics of PZT, it is most desirable to use platinum. In addition to platinum, a material that does not react strongly with PZT or oxidize and lose its properties as a metal when sintering a PZT fiber molded body at 1100 ° C. to 1200 ° C. can be substituted. Examples of such materials include stainless steel, nickel, titanium, etc., but it is necessary to devise a technique that suppresses the reaction with PZT as much as possible.
The binder can be selected from, for example, methylcellulose, tragacanth rubber, and polyvinyl alcohol. This binder is usually mixed in an amount of 10% by mass or less, preferably 8% by mass or less, based on the PZT powder. Moreover, about 1 mass% of glycerin etc. are normally added as a plasticizer, and about 5-20 mass% of water is added. For example, 15 mL of water is added to 100 g of PZT powder. In addition, it is also possible to use a thermoplastic polymer using a phthalic acid-based polymer as a binder.
[0008]
(Embodiment 1)
In Embodiment 1 of the present invention, lead nitrate, zirconium chloride oxide, and titanium tetrachloride are mixed in an aqueous potassium hydroxide solution and placed in a pressure vessel together with titanium wire 1 for film formation. By maintaining, the Pb ²⁺ , Zr ⁴⁺ , Ti ⁴⁺ ions in the solution react with the titanium wire 1 to grow a PZT polycrystalline film 2 on the surface of the titanium wire 1 to produce a PZT fiber.
[0009]
Specifically, lead nitrate 1.0 mol / L, zirconium chloride oxide 1.7 mol / L, titanium tetrachloride 3.11 mol / L are prepared. At the time of nucleation, lead nitrate 7 mL, zirconium chloride oxide 2 mL and potassium hydroxide 8 mol / L Is mixed with 12 mL and reacted at 150 ° C. for 48 hours. After that, until the growth time, lead nitrate 7.27mL, zirconium chloride 1.85mL, titanium tetrachloride 0.89mL and potassium hydroxide 4mol / L are mixed with 12mL and reacted at 120 ° C for 48 hours. The pressure in the autoclave is the vapor pressure at each temperature. It is about 0.4 MPa at 150 ° C and about 0.1 MPa at 120 ° C.
FIG. 1 shows a scanning electron microscope photograph of the surface of a PZT fiber produced by the hydrothermal synthesis method, and FIG. 2 shows a cross section of the PZT fiber produced by the hydrothermal synthesis method. As can be seen from the photograph of the surface of the PZT fiber in FIG. 1, a PZT crystal of 5 to 10 μm is laminated and grown on the surface of the titanium wire 1. Further, as shown in the photograph of the cross section of the PZT fiber in FIG. 2, a PZT thin film 2 having a thickness of about 20 μm is formed on the surface of a titanium wire 1 having a diameter of 150 μm. Thus, by using a film formation method based on a hydrothermal synthesis method, a PZT crystal film of about 20 μm is formed in a wire shape, which is difficult with conventional film formation methods such as sputtering, screen press, and sol-gel method. Can do.
[0010]
(Embodiment 2)
The second embodiment of the present invention shows a smart board having the function of a sensor or actuator obtained by embedding the PZT fiber produced in the first embodiment in a composite material.
That is, as shown in FIG. 3, PZT fibers 3, 3,... Are embedded in the surface of six layers of carbon fiber reinforced plastic (CFRP). At this time, carbon fibers of carbon fiber reinforced plastic are used so that two unidirectional prepregs 4 and 5 are alternately orthogonal to each other, and the embedded PZT fiber 3 and the prepreg 4 are aligned so that the composite material is embedded. The impact on is reduced. Since PZT ceramics have a high Curie point of 350 ° C., they are hardly affected by hot pressing used when molding a composite material, and can be embedded at the time of molding.
In the experiment in the second embodiment, as shown in FIG. 4, PZT fibers 3, 3,... Are placed on the upper surfaces of six layers of prepregs 4, 5, and pressure is applied from above and below in a temperature atmosphere of 150.degree. In addition, a cantilever structure 10 having a length of 70 mm, a width of 30 mm, and a thickness of 0.7 mm, in which PZT fibers 3, 3.
In this embodiment, since the smart board itself is used as an electrode, it is possible to use a conductive composite material (CFRP) or the like whose main component is carbon fiber.
The piezoelectric fiber is designed to be embedded in a composite material such as CFRP, so that the outer diameter is designed to be within one or two CFRP prepregs (preferably 150 μm to 300 μm). By using the same diameter as that of the optical fiber (the optical fiber is similarly embedded in the composite material to detect strain and the like, the diameter is about 150 μm), the range of use can be expanded. In the hydrothermal synthesis method, a PZT thin film is prepared by a chemical reaction, so that the PZT thickness is practically about 5 μm to 30 μm. In general, a fiber with a commercially available Ti wire diameter of about 50 μm to 200 μm (when Ti wire 150 μm is used) can be produced. Since very thin fibers can be made, PZT fibers embedded without compromising the mechanical strength of the composite layer are suitable for sensor applications. In one extrusion molding method, the PZT film is physically coated on the surface of a metal wire (for example, platinum wire) by an extruder, so that a PZT film having a thickness of 1 to 2 mm or more thicker than that of the hydrothermal synthesis method can be formed. it can. Therefore, the PZT fiber formed by the extrusion method can be used for an actuator.
[0011]
(Embodiment 3)
The third embodiment shows the use of the smart board created in the second embodiment for an actuator.
FIG. 5A shows an example in which the smart board is used as an actuator in the third embodiment, and FIG. 5B shows another example.
As shown in FIGS. 5A and 5B, the PZT fiber is embedded by applying a voltage between the titanium wire 1 of the PZT fiber 3 and the conductive composite material 9 made of carbon fiber reinforced plastic or the like. The portion 8 of the PZT crystal film is deformed by a negative voltage and contracted by a positive voltage. For example, if a positive voltage is applied, the portion 8 of the PZT crystal film in which the fiber is embedded is stretched and deformed as shown on the left in FIG. This deformation causes bending deformation in the composite material as shown on the right side of FIG.
In particular, in the present invention shown in FIG. 5 (a), the fiber can be used as a sensor or an actuator by using the inner metal wire as an electrode, so that all the embedded portions of the deeply embedded fiber can be used for sensors and actuators. is there.
In addition, as the electroconductive composite material 9, it is not restricted to what has a carbon fiber as a main component, If it is a composite material which has electroconductivity, it can be used.
[0012]
As shown in FIG. 7, in the verification experiment, the end of the cantilever structure 10 was fixed, a driving voltage (50 Vpp) was applied to the four embedded wires, and the vibration displacement generated at the tip was measured using a laser displacement meter. A structure having a sensor or actuator function is described, for example, in Aaron A. Bent, Nesbitt W. Hagood, and John P. Rodgers 'Anisotropic Actuation with Piezoelectric Fiber Composites', Proceedings of the DGLR Conference, Germany (1993). Things. FIG. 8 shows the relationship between drive frequency and vibration displacement. From the figure, it can be seen that there is a displacement of about 10 nm and the resonance occurs around 180 Hz. The vibration displacement can be controlled by changing the number of fibers to be embedded and the driving voltage.
[0013]
(Embodiment 4)
The fourth embodiment shows the use of the smart board created in the second embodiment as a sensor.
In addition to the inverse piezoelectric effect that generates strain when a voltage is applied, the piezoelectric material also has a positive piezoelectric effect that generates an electric charge when strain is applied. By utilizing this effect, it is possible to detect distortion applied to the smart board. An electromagnetic vibrator 11 is attached to the tip of the cantilever structure 10 created as shown in FIG. 9, and the cantilever structure 10 is forcibly vibrated. In particular, the electromagnetic vibrator 11 is attached to the tip of the cantilever structure with an adhesive. The voltage output from the piezoelectric fiber 3 due to the vibration was detected using the lock-in amplifier 12.
FIG. 10 shows the relationship between the drive frequency, the vibration displacement, and the output voltage from the fiber. The broken line indicates the vibration displacement forcibly vibrated using the electromagnetic vibrator 11. The solid line indicates the voltage output from one PZT fiber embedded at that time. It can be seen from the figure that the drive displacement and the output voltage are almost proportional.
[0014]
(Embodiment 5)
The fifth embodiment shows the application of an extrusion method as a method for producing a fiber in which a metal wire surface is coated with a PZT crystal layer. That is, a platinum fine wire (50 μm diameter), which is led from a wire guide 16 from a nozzle 13 attached to an extrusion molding machine (about 10 MPa) as shown in FIG. 15 and a nozzle outlet (200 μm diameter) 17 are simultaneously extruded to form a PZT fiber molded body 18 containing a metal core. Next, the PZT fiber molded body 18 was dried, debindered, and then sintered at a high temperature of 1100 ° C. to 1200 ° C. to produce a final product PZT fiber.
[0015]
(Embodiment 6)
In the sixth embodiment, a cantilever structure is created by the same method as in the second embodiment using the PZT fiber obtained in the fifth embodiment, and the actuator performance is verified by the same method as in the third embodiment. FIG. 12 shows the relationship between drive frequency and vibration displacement. From the figure, it can be seen that the background displacement is about 20 to 30 nm and the displacement at the resonance frequency of 220 Hz is about 5 μm. As can be seen from the results of the hydrothermal synthesis fiber shown in FIG. 8, the fiber displacement by the extrusion method is higher by one digit or more, and it can be said that the actuator performance is excellent. .
[0016]
(Embodiment 7)
In the seventh embodiment, a cantilever structure is created by the same method as in the second embodiment using the PZT fiber obtained in the fifth embodiment, and the sensor performance is verified by the same method as in the fourth embodiment. FIG. 13 shows the relationship between the drive frequency, the vibration displacement, and the output voltage from the fiber. The solid line shows the vibration displacement forcedly vibrated by the electromagnetic vibrator, and the broken line shows the voltage output from one PZT fiber embedded at that time. From the figure, it can be seen that the sensor signal is output corresponding to the drive displacement. As can be seen from the result of the hydrothermal synthesis method of FIG. 10, there is no significant difference in the sensor performance of the fiber by the extrusion method from that of the hydrothermal synthesis method.
[0017]
【The invention's effect】
According to the present invention, it is possible to provide a PZT fiber, a smart board using the PZT fiber, and an actuator and a sensor using the smart board. These are required to form a comb-shaped electrode, and are easy to break. By combining PZT ceramics with high piezoelectric effect, heat-resistant metal wires such as titanium wires or platinum wires, and conductive composite materials, they are excellent. Exhibits excellent performance.
The present invention has the following effects.
(1) The use of PZT ceramics with high piezoelectric effect as the fiber material and the use of a metal wire such as a titanium wire as the core wire in the fiber makes it possible to maintain the properties as a piezoelectric material while maintaining the characteristics inherent to ceramics. It is possible to solve the problem of breakage of the ceramic fiber due to the problem of being easily broken.
(2) Since the prepared PZT fiber is embedded in a conductive composite material such as CFRP, and the composite material itself is used as an electrical common ground, the electric power generated when a voltage is applied as an actuator and the voltage is detected as a sensor. Interference can be suppressed, and is not easily affected by external noise.
(3) Since a metal wire such as a titanium wire as a core material can be used not only as a reinforcing material for PZT ceramics but also as an electric signal line, it can be used as a sensor or an actuator simply by being embedded in a conductive fiber. There is no need to create a new tooth-like electrode.
(4) Piezoelectric fibers can be easily embedded in the process of molding carbon-based composite materials into structures such as buildings, automobiles, ships, and aircraft, and the embedded fibers can be used without sensors or other devices without the need to form other electrodes. It can be used for an actuator. As a result, it is possible to improve the reliability of the structure and reduce the maintenance cost by detecting the vibration of the structure and canceling the vibration, thereby preventing fatigue failure, preventing unstable vibration, and improving riding comfort.
(5) The PZT fiber produced by the extrusion molding method is excellent in actuator performance because of high fiber displacement.
[Brief description of the drawings]
FIG. 1 is a scanning electron micrograph of the surface of a PZT fiber according to Embodiment 1 of the present invention produced by a hydrothermal synthesis method.
FIG. 2 is a scanning electron micrograph of a cross section of a PZT fiber according to Embodiment 1 of the present invention produced by a hydrothermal synthesis method.
FIG. 3 is a perspective view showing a method for manufacturing a smart board according to Embodiment 2 of the present invention.
FIG. 4 is a perspective view showing a structure of a smart board according to Embodiment 2 of the present invention.
FIGS. 5 (a) and 5 (b) are explanatory diagrams for use as actuators according to Embodiment 3 of the present invention. FIG.
FIG. 6 is an explanatory view showing a state in which a composite material is deformed by deformation of a PZT fiber when used as an actuator according to Embodiment 3 of the present invention.
FIG. 7 is an explanatory diagram when used as an actuator according to a third embodiment of the present invention.
FIG. 8 is a result of a demonstration experiment when used as an actuator according to Embodiment 3 of the present invention.
FIG. 9 is an explanatory diagram when used as a sensor according to a fourth embodiment of the present invention.
FIG. 10 is a result of a verification experiment when used as a sensor according to Embodiment 4 of the present invention.
FIG. 11 is an explanatory diagram for producing a PZT fiber by a nozzle attached to an extrusion molding machine according to a fifth embodiment of the present invention.
FIG. 12 is a result of a demonstration experiment when used as an actuator according to a sixth embodiment of the present invention.
FIG. 13 is a result of a verification experiment when used as a sensor according to Embodiment 7 of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Titanium wire 2 PZT thin film 3 PZT fiber 4, 5 Prepreg 8 Embedded PZT crystal film part 9 Conductive composite material 10 Cantilever structure 11 Electromagnetic exciter 12 Lock-in amplifier 13 Nozzle 14 Extruded from an extruder Coming PZT paste 15 Platinum wire 16 Wire guide 17 Fiber outlet 18 Finished molded product

Claims (10)

  A lead zirconate titanate fiber characterized in that it is formed by coating a lead zirconate titanate crystal on the surface of a metal wire.   The lead zirconate titanate fiber according to claim 1, wherein the metal wire is a titanium wire.   The lead zirconate titanate fiber according to claim 1, wherein the metal wire is a heat resistant metal wire, and the heat resistant metal wire is made of platinum, stainless steel, or nickel.   The lead zirconate titanate fiber according to any one of claims 1 to 3, wherein the surface of the metal wire is coated with lead zirconate titanate crystals by a hydrothermal synthesis method.   The lead zirconate titanate fiber according to any one of claims 1 to 3, wherein the surface of the metal wire is coated with a lead zirconate titanate crystal layer by an extrusion molding method.   A smart board comprising the lead zirconate titanate fiber according to any one of claims 1 to 5 embedded in a conductive composite material layer.   The smart board according to claim 6, wherein the conductive composite material layer is made of a carbon fiber reinforced plastic.   8. An actuator using a smart board, wherein a voltage is applied between the lead zirconate titanate fiber and the conductive composite material layer of the smart board according to claim 6 or 7.   A sensor using a smart board, comprising a voltage detector connected to the smart board according to claim 6. A method of using the smart board according to claim 6 or 7 as an actuator or a sensor, wherein a voltage is applied between the lead zirconate titanate fiber and the conductive composite material layer .

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