Piezoelectric fiber, preparation method thereof and piezoelectric sensor

Abstract

The invention relates to the field of piezoelectric fibers, and discloses a piezoelectric fiber and a preparation method thereof, and a piezoelectric sensor, the piezoelectric fiber comprises a conductive fiber core, a piezoelectric layer and an electrode layer, the outer surface of the conductive fiber core is alternately coated with the piezoelectric layer and the electrode layer, the innermost layer coating the outer surface of the conductive fiber core is the piezoelectric layer, and the electrode layer is the piezoelectric layer. The piezoelectric layer is arranged on the outer layer of the conductive fiber core, the electrode layer is arranged on the outermost layer far away from the conductive fiber core, the number of the piezoelectric layer and the number of the electrode layer are both at least one, the surface roughness of the conductive fiber core is smaller than 500 nm, the piezoelectric fiber can improve the conversion efficiency of mechanical signals and electric signals to a high degree, and the signal detection and collection sensitivity of the piezoelectric fiber is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of piezoelectric fibers, and in particular to a piezoelectric fiber and a preparation method thereof, and a piezoelectric sensor. Background Art

[0002] In the preparation process of piezoelectric fibers, since piezoelectric materials are in a filamentary structure, the filamentary piezoelectric materials are usually stacked or woven into a sheet of piezoelectric layers in an orderly or disordered manner, and then the electrode layers are printed on both sides of the piezoelectric layer. However, only part of the piezoelectric material in the piezoelectric fiber with this structure can directly contact the electrode layer, making it difficult to efficiently transmit the deformation signal of the piezoelectric layer to the electrode layer, thereby reducing the conversion efficiency of mechanical signals and electrical signals, and affecting the sensitivity of the piezoelectric fiber to signal detection and collection. Summary of the invention

[0003] The embodiment of the present invention discloses a piezoelectric fiber and a preparation method thereof, and a piezoelectric sensor. The piezoelectric fiber can improve the conversion efficiency of mechanical signals and electrical signals to a high degree, and improve the sensitivity of signal detection and collection of the piezoelectric fiber.

[0004] In the first aspect, an embodiment of the present application discloses a piezoelectric fiber, comprising: a conductive fiber core, a piezoelectric layer and an electrode layer alternately coated on the outer surface of the conductive fiber core, wherein the innermost layer coated on the outer surface of the conductive fiber core is the piezoelectric layer, and the outermost layer away from the conductive fiber core is the electrode layer, the number of layers of the piezoelectric layer and the electrode layer are at least one, and the surface roughness of the conductive fiber core is less than 500nm.

[0005] Furthermore, the ratio of the surface roughness of the conductive fiber core to the diameter of the conductive fiber core is less than 0.1.

[0006] Further, the ratio of the thickness of any piezoelectric layer to the diameter of the conductive fiber core is 0.05 to 0.15; and / or,

[0007] The diameter of the conductive fiber core is 0.05 mm to 1 mm.

[0008] Furthermore, the structure of the conductive fiber core includes a conductive inner core and a coupling agent layer coated on the outer surface of the conductive inner core.

[0009] Furthermore, the structure of the conductive fiber core includes a conductive inner core and a coupling agent layer coated on the outer surface of the conductive inner core.

[0010] Further, the material of the conductive inner core includes metal fiber or carbon fiber; and / or,

[0011] The piezoelectric material of the piezoelectric layer includes at least one of piezoelectric ceramics and piezoelectric polymers; and / or,

[0012] The electrode material of the electrode layer includes at least one of silver and 3,4-ethylenedioxythiophene monomer; and / or,

[0013] The coupling material of the coupling agent layer includes at least one of methacrylate and methoxysilane; and / or,

[0014] The thickness of the coupling agent layer is 50nm to 1000nm.

[0015] In a second aspect, an embodiment of the present application discloses a method for preparing the piezoelectric fiber according to the first aspect, the preparation method comprising the following steps:

[0016] Alternately coating the outer surface of the conductive fiber core with piezoelectric material and electrode material in sequence to form the piezoelectric layer and the electrode layer;

[0017] The innermost layer coated on the outer surface of the conductive fiber core is the piezoelectric layer, and the outermost layer away from the conductive fiber core is the electrode layer.

[0018] Furthermore, before the step of alternately coating the outer surface of the conductive fiber core with piezoelectric material, the preparation method further comprises: cleaning the conductive inner core, coating the outer surface of the conductive inner core with coupling material to form a coupling agent layer.

[0019] Furthermore, the solid content of the coupling material is 6% to 12%, and the viscosity of the coupling material is 1 mPa.s to 500 mPa.s.

[0020] Furthermore, the step of alternately coating the outer surface of the conductive fiber core with piezoelectric material in sequence comprises:

[0021] Mixing the piezoelectric material with a solvent to form a slurry, placing the conductive fiber core in the slurry to coat the outer surface of the conductive fiber core with the piezoelectric material;

[0022] The viscosity of the slurry is 800 mpa.s to 1500 mpa.s, and the immersion speed of the conductive fiber core in the slurry is 300 mm / min to 1500 mm / min.

[0023] Furthermore, in the slurry, the particle size of the piezoelectric material is less than 1 μm.

[0024] Furthermore, when the piezoelectric material is a piezoelectric ceramic, the solid content of the slurry is 60% to 80%;

[0025] Alternatively, when the piezoelectric material is a piezoelectric polymer, the solid content of the slurry is 5% to 20%;

[0026] Alternatively, when the piezoelectric material is a piezoelectric polymer and a ceramic material, the mass content of the piezoelectric polymer in the slurry is 5% to 20%, and the mass content of the piezoelectric ceramic in the slurry is 60% to 80%.

[0027] Furthermore, after the step of alternately coating the outer surface of the conductive fiber core with piezoelectric materials in sequence and before the step of coating the electrode material, the preparation method further comprises: performing a crystallization polarization treatment on the piezoelectric material:

[0028] Alternatively, after the step of coating the electrode material, the preparation method further comprises: performing a crystal polarization treatment on the piezoelectric material.

[0029] Furthermore, in the step of performing crystal polarization treatment on the piezoelectric material, the rotation period during polarization is 6 to 10 cycles, and the process time is 5 minutes to 16 minutes.

[0030] In a third aspect, an embodiment of the present application discloses a piezoelectric sensor, which includes the piezoelectric fiber described in the first aspect, or is prepared by the preparation method described in the second aspect.

[0031] Compared with the prior art, the beneficial effects of this application are:

[0032] An embodiment of the present application provides a piezoelectric fiber, which includes: a conductive fiber core, a piezoelectric layer and an electrode layer alternately coated on the outer surface of the conductive fiber core, wherein the innermost layer coated on the outer surface of the conductive fiber core is the piezoelectric layer, and the outermost layer away from the conductive fiber core is the electrode layer, and the surface roughness of the conductive fiber core is set to be less than 500nm, indicating that the outer surface of the conductive fiber core is relatively smooth, thereby reducing the difficulty of coating the piezoelectric layer, so that the piezoelectric layer can be evenly coated on the outer surface of the conductive fiber core, so that the stress distribution at the contact interface between the piezoelectric layer and the conductive fiber core is uniform and stable, which helps to improve the mechanical stability of the piezoelectric fiber, and has a higher conversion rate between electrical signals and mechanical signals, thereby improving the sensitivity of signal detection and collection of the piezoelectric fiber.

[0033] Furthermore, since the electrode layer is directly coated on the outer surface of the piezoelectric layer, each region of the piezoelectric layer can directly contact the electrode layer, so the electrical signal of the piezoelectric layer can be fully transmitted to the electrode layer, thereby helping to improve the conversion rate of electrical signals and mechanical signals, and improving the sensitivity of signal detection and collection of piezoelectric fibers. In addition, the structure of the present application can be used to alternately prepare multiple layers of piezoelectric layers and multiple layers of electrode layers, and any layer of piezoelectric layer can directly contact its adjacent electrode layer, further ensuring the performance of the multi-layer structure.

[0034] In summary, the piezoelectric fiber provided in the present application controls the roughness of the conductive fiber core to promote the uniformity of the piezoelectric layer coating. In addition, since the contact area between the piezoelectric layer and the electrode layer is large, the conversion efficiency of mechanical signals and electrical signals can be improved to a great extent, thereby improving the sensitivity of signal detection and collection of the piezoelectric fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 is a schematic diagram of the structure of a piezoelectric fiber when the number of layers provided in an embodiment of the present application is one layer;

[0037] Figure 2 is a schematic diagram of the structure of a piezoelectric fiber when the number of layers provided in an embodiment of the present application is two;

[0038] Figure 3 is a process flow chart for preparing piezoelectric fibers provided in an embodiment of the present application;

[0039] Figure 4 is a schematic diagram of the structure of the conductive fiber before impregnation provided in an embodiment of the present application;

[0040] Figure 5 is a process flow chart of conductive fiber impregnation provided in an embodiment of the present application;

[0041] Figure 6 It is a schematic diagram of the structure of the conductive fiber after impregnation provided in an embodiment of the present application.

[0042] Icons: 1. Conductive fiber core; 11. Conductive inner core; 12. Coupling agent layer; 2. Piezoelectric layer; 21. First piezoelectric layer; 22. Second piezoelectric layer; 3. Electrode layer; 31. First electrode layer; 32. Second electrode layer; 4. Immersion tank; 41 tank head; 42. Tank tail. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] In the present invention, the directions or positional relationships indicated by the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like are based on the directions or positional relationships shown in the drawings. These terms are mainly used to better describe the present invention and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific direction, or to be constructed and operated in a specific direction.

[0045] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those skilled in the art, the specific meanings of these terms in the present invention can be understood according to specific circumstances.

[0046] In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise specified, "plurality" means two or more.

[0047] The technical solution provided by the present invention will be further described below in conjunction with embodiments and drawings.

[0048] Piezoelectric fibers have a significant piezoelectric effect, which can convert mechanical signals into electrical signals or vice versa. In addition, piezoelectric fibers are also resistant to high temperatures, resistant to oxidation, and have good flexibility, which makes them have broad application prospects in the fields of piezoelectric sensors and piezoelectric actuators.

[0049] Among them, when the piezoelectric fiber is made by electrospinning, the piezoelectric material is formed into a filament under high voltage and then collected by a winding mechanism, and a crystal polarization treatment is performed at the same time to obtain a filament structure, and the filament structure is stacked or woven into a lamellar structure in an orderly or disordered manner, and then the electrode layer is printed on both sides of the lamellar structure. However, in this method, since the lamellar structure is formed by stacking or weaving multiple filamentary structures, only part of the lamellar structure can directly contact the electrode layer, making it difficult to efficiently transmit the deformation signal of the piezoelectric layer to the electrode layer, thereby reducing the conversion efficiency of mechanical signals and electrical signals, and affecting the sensitivity of the piezoelectric fiber to signal detection and collection.

[0050] Based on the above problems, the embodiments of the present application provide a piezoelectric fiber and a preparation method thereof, and a piezoelectric sensor, which can improve the conversion efficiency of mechanical signals and electrical signals to a high degree and improve the sensitivity of signal detection and collection.

[0051] In a first aspect, the present application provides a piezoelectric fiber, such as Figure 1 and Figure 2 As shown, the piezoelectric fiber includes: a conductive fiber core 1, piezoelectric layers 2 and electrode layers 3 alternately coated on the outer surface of the conductive fiber core 1, wherein the innermost layer coated on the outer surface of the conductive fiber core 1 is the piezoelectric layer 2, and the outermost layer away from the conductive fiber core is the electrode layer 3, the number of layers of the piezoelectric layer 2 and the electrode layer 3 are at least one, and the surface roughness of the conductive fiber core is less than 500nm.

[0052] Furthermore, the present application may adopt a contact measuring instrument, using a probe to achieve direct contact with the surface of the sample to be measured, thereby testing the surface roughness of the conductive fiber core, or adopt an atomic force microscope, using the interaction force between the needle trace and the atoms on the surface of the sample to be measured to measure the surface roughness of the conductive fiber core.

[0053] The number of alternating layers of the piezoelectric layer 2 and the electrode layer 3 is one layer, see the back Figure 1 At this time, the innermost layer coated on the outer surface of the conductive fiber core 1 is the piezoelectric layer 2, and the outermost layer is the electrode layer 3; when the number of alternating layers of the piezoelectric layer 2 and the electrode layer 3 is two, refer to the back Figure 2 , the outer surface of the conductive fiber core 1 is coated with the first piezoelectric layer 21, the first electrode layer 31, the second piezoelectric layer 22 and the second electrode layer 32 in sequence, that is, any piezoelectric layer 2 is provided with its corresponding electrode layer 3, wherein the innermost layer coated on the outer surface of the conductive fiber core 1 is the piezoelectric layer 2, which refers to the first piezoelectric layer 21 directly in contact with the outer surface of the conductive fiber core 1; the outermost layer away from the conductive fiber core 1 is the electrode layer 3, which refers to the second electrode layer 32 coated on the outermost second piezoelectric layer 22 of the guiding fiber core 1. It can be understood that the number of alternating coatings of the piezoelectric layer 2 and the electrode layer 3 can also be three, four or more layers.

[0054] In addition, the piezoelectric material of the piezoelectric layer 2 includes at least one of piezoelectric ceramics and piezoelectric polymers, and the electrode material of the electrode layer 3 includes at least one of silver and 3,4-ethylenedioxythiophene monomers.

[0055] The piezoelectric fiber provided in the present application includes: a conductive fiber core 1, a piezoelectric layer 2 and an electrode layer 3 alternately coated on the outer surface of the conductive fiber core 1, and the surface roughness of the conductive fiber core 1 is less than 500nm, indicating that the outer surface of the conductive fiber core 1 has small defects and is relatively smooth, which reduces the difficulty of coating the piezoelectric layer 2 and helps to evenly coat the piezoelectric layer 2 on the conductive fiber core 1, so that the contact area between the piezoelectric layer 2 and the conductive fiber core 1 is larger, the stress distribution is more uniform, and the bonding stability is better, thereby helping to improve the mechanical stability of the piezoelectric fiber, and helping to increase its detection sensitivity and improve the conversion rate of mechanical signals and electrical signals.

[0056] Furthermore, since the outer surface of any piezoelectric layer 2 is coated with an electrode layer 3, the contact area between the electrode layer 3 and the piezoelectric layer 2 is relatively large, and the signal acquired by the piezoelectric layer 2 can be effectively transmitted to the electrode layer 3, thereby further improving the conversion rate of the electrical signal and mechanical signal of the piezoelectric fiber, and improving the sensitivity of the signal detection and collection of the piezoelectric fiber. In addition, since the structure of the present application can prepare multiple layers of piezoelectric layers 2 and electrode layers 3, and any layer of the piezoelectric layer 2 can directly contact the electrode layer 3, the performance of the piezoelectric fiber with a multilayer structure is further improved.

[0057] In summary, the piezoelectric fiber provided in the present application controls the roughness of the conductive fiber core 1 so that the piezoelectric layer 2 is coated uniformly and has high stability in contact with the conductive fiber core 1, thereby improving the performance of the piezoelectric fiber. Furthermore, since the piezoelectric layer 2 is directly coated with the electrode layer 3, the contact area between the piezoelectric layer 2 and the electrode layer 3 is large, thereby further improving the conversion efficiency of the mechanical signal and electrical signal of the piezoelectric fiber and improving the sensitivity of the signal detection and collection of the piezoelectric fiber.

[0058] In addition, since the ratio of the surface roughness of the conductive fiber core of the present application to the diameter of the conductive fiber core is less than 0.1, it means that the surface smoothness of the conductive fiber core is relatively high and there are fewer defects and cracks, so it helps to avoid the short circuit phenomenon caused by the conductive fiber core penetrating the piezoelectric layer and directly contacting the electrode layer. Moreover, since the conductive fiber core has fewer defects, it has higher structural stability.

[0059] Furthermore, the ratio of the thickness of any piezoelectric layer to the diameter of the conductive fiber core is 0.05 to 0.15. When the thickness is controlled within the above range, the piezoelectric layer is more sensitive to external mechanical signals, which helps to improve the conversion efficiency of mechanical signals and electrical signals, and also helps to avoid excessive stress in the piezoelectric fiber, so that the piezoelectric fiber has better mechanical properties.

[0060] Among them, the diameter of the conductive fiber core is 0.05mm~1mm. When the diameter of the conductive fiber core is controlled within the above range, the piezoelectric fiber has good mechanical properties. And because the diameter of the conductive fiber core is much larger than its surface roughness, it further shows that the surface smoothness of the conductive fiber core is relatively high, which helps to improve the uniformity of the piezoelectric layer coating.

[0061] For further information, see Figure 1The structure of the conductive fiber core 1 includes a conductive inner core 11 and a coupling agent layer 12 coated on the outer surface of the conductive inner core 11. When the outer surface of the conductive inner core 11 is coated with the coupling agent layer 12, the coupling agent layer 12 can fill the surface defects and pores of the conductive inner core 11, so that the surface roughness of the conductive fiber core 1 finally prepared is less than 500nm, which is conducive to reducing the difficulty of coating the piezoelectric layer 2 and making the piezoelectric layer 2 and the conductive fiber core 1 have better adhesion. In addition, the coupling agent layer 12 can also serve as a bridge, and the piezoelectric layer 2 is coated on the outer side of the conductive fiber core 1 by chemical bonding, so that the connection between the conductive fiber core 1 and the piezoelectric layer 2 is more stable.

[0062] The material of the conductive inner core 11 includes metal fiber or carbon fiber; the coupling material of the coupling agent layer 12 includes at least one of methacrylate and methoxysilane, and the methacrylate includes polyacrylic acid. The functional groups in methacrylate and methoxysilane can react chemically or physically adsorb with the functional groups such as hydroxyl and amino in the piezoelectric material, thereby significantly increasing the bonding strength of the interface between the piezoelectric layer 2 and the conductive fiber core 1, thereby improving the mechanical properties of the piezoelectric fiber.

[0063] It should be noted that when the material of the coupling agent layer 12 is a polymer formed by methacrylates and methoxysilanes, the mass ratio of methacrylates and methoxysilanes is 1:1 to 1:4, which is more helpful to improve the bonding strength between the conductive fiber core 1 and the piezoelectric layer 2. Moreover, since methacrylates have good chemical corrosion resistance and methoxysilane has high heat resistance, this polymer is more helpful to reduce the impact of piezoelectric fibers on the environment, thereby improving the service life of the piezoelectric fibers to a greater extent.

[0064] In addition, since the thickness of the coupling agent layer 12 is 50nm~1000nm, the coupling agent layer 12 can be effectively coated on the outer surface of the conductive inner core 11, thereby ensuring that the roughness of the prepared conductive fiber core 1 is smaller, which is more conducive to the coating of the piezoelectric material and also helps to improve the chemical bonding ability of the piezoelectric layer 2 and the conductive fiber core 1, and improve the bonding strength of the interface between the piezoelectric layer 2 and the conductive fiber core 1.

[0065] The second aspect, such as Figure 3 As shown, the embodiment of the present application discloses a method for preparing a piezoelectric fiber, and the preparation method comprises the following steps:

[0066] The outer surface of the conductive fiber core 1 is alternately coated with piezoelectric material and electrode material to form a piezoelectric layer 2 and an electrode layer 3;

[0067] The innermost layer coated on the outer surface of the conductive fiber core 1 is the piezoelectric layer 2 , and the outermost layer away from the conductive fiber core 1 is the electrode layer 3 .

[0068] In addition, in order to further ensure that the surface roughness of the conductive fiber core 1 is small, before the step of alternately coating the outer surface of the conductive fiber core 1 with piezoelectric material, the preparation method also includes: cleaning the conductive inner core 11, coating the outer surface of the conductive inner core 11 with coupling material to form a coupling agent layer 12.

[0069] When cleaning the conductive inner core 11, a plasma cleaning method can be used. This method can effectively remove the oxide on the conductive inner core 11, and can improve the surface tension, surface energy, wettability, and adhesion of the conductive inner core 11, thereby helping to ensure the uniformity and tightness of the subsequent coating of the piezoelectric layer 2. In addition, the coupling agent layer 12 can be coated on the outer surface of the conductive inner core 11 by spraying or dipping. The present application does not limit the coating process as long as the purpose of the present application can be achieved.

[0070] Furthermore, the solid content of the coupling material is 6% to 12%, and the viscosity of the coupling material is 1 MPa.s to 500 MPa.s. When the solid content and viscosity of the coupling agent are controlled within the above range, the coupling agent layer can be effectively coated on the outer surface of the conductive inner core, and the defects and cracks on the surface of the conductive inner core can be effectively filled, so that the surface roughness of the guide fiber core is small and the thickness is appropriate, thereby ensuring the effectiveness and stability of the combination of the piezoelectric layer and the conductive fiber core, and can improve the performance of the piezoelectric fiber to a high degree.

[0071] In an optional embodiment, the step of alternately coating the outer surface of the conductive fiber core with piezoelectric material comprises:

[0072] Mixing a piezoelectric material with a solvent to form a slurry, placing a conductive fiber core in the slurry to coat the outer surface of the conductive fiber core with the piezoelectric material;

[0073] The viscosity of the slurry is 800mpa.s to 1500mpa.s, and the immersion speed of the conductive fiber core in the slurry is 300mm / min to 1500mm / min.

[0074] The present application controls the viscosity and speed of the slurry within the above ranges so that the piezoelectric material can be effectively attached to the conductive fiber core, thereby ensuring the uniformity of the piezoelectric layer coating and further improving the performance of the piezoelectric fiber.

[0075] And, if Figures 4 to 6As shown, they are schematic diagrams of the structures of the conductive fiber core 1 before, during and after impregnation, wherein before impregnation, the conductive fiber core 1 is not coated with the piezoelectric layer 2, and during impregnation, from the slot head 41 to the slot tail 42, the conductive fiber core 1 is gradually coated with the piezoelectric layer 2, and the closer to the slot tail 42, the higher the thickness of the piezoelectric layer 2 coating, and after impregnation, the coating process of the piezoelectric layer 2 is completed, and at this time the thickness of the piezoelectric layer 2 coating is relatively thick, that is, in the process of impregnating the conductive fiber core 1, the conductive fiber core is placed in the impregnation tank 4, and the conductive fiber core 1 is transferred from the slot head 41 of the impregnation tank 4 to the slot tail 42, the impregnation process is completed, wherein the impregnation speed refers to the average speed at which the conductive fiber core 1 is transferred from the slot head 41 of the impregnation tank 4 to the slot tail 42.

[0076] Furthermore, in the slurry, the particle size of the piezoelectric material is less than 1 μm. Since the particle size of the piezoelectric material in the slurry is small, it means that the solvent can effectively dissolve the piezoelectric material, making the fluidity of the slurry suitable, which is more conducive to forming a uniform coating during the coating process, reducing the difficulty of coating the piezoelectric material, thereby making the piezoelectric layer coated on the conductive fiber core more uniform and having higher coating quality.

[0077] Among them, when the piezoelectric material is piezoelectric ceramic, the solid content of the slurry is 60% to 80%; when the piezoelectric material is piezoelectric polymer, the solid content of the slurry is 5% to 20%; when the piezoelectric material is piezoelectric polymer and ceramic material, the mass content of the piezoelectric polymer in the slurry is 5% to 20%, and the mass content of the piezoelectric ceramic in the slurry is 60% to 80%.

[0078] According to the type of piezoelectric material, the solid content of the slurry is adjusted to ensure that the fluidity of the slurry is appropriate and the stability of the slurry is good, which helps to reduce the difficulty of coating and form a higher quality piezoelectric layer.

[0079] In a first optional embodiment, after the step of alternately coating the outer surface of the conductive fiber core with piezoelectric material in sequence and before the step of coating with electrode material, the preparation method further comprises: performing crystallization polarization treatment on the piezoelectric material.

[0080] Among them, when the number of piezoelectric layers and electrode layers is greater than or equal to two layers, a one-step polarization method can be adopted, that is, when the last layer of piezoelectric material is coated, the piezoelectric materials of all piezoelectric layers are subjected to a one-time crystallization polarization treatment, and then the last electrode layer is prepared on the outer surface of the piezoelectric layer; or, a layer-by-layer crystallization polarization method is adopted, that is, when any layer of piezoelectric material is coated, the piezoelectric material is subjected to crystallization polarization treatment, and then the corresponding electrode layer is prepared on the outer surface of the piezoelectric layer.

[0081] In a second optional embodiment, after the step of coating the electrode material, the preparation method further includes: performing crystallization polarization treatment on the piezoelectric material. In the crystallization polarization treatment process, when the number of piezoelectric layers and electrode layers is greater than or equal to two layers, a one-step polarization method can be adopted, that is, when the last layer of electrode material is coated, the piezoelectric materials of all piezoelectric layers are subjected to a one-time crystallization polarization treatment; or, a layer-by-layer crystallization polarization method is adopted, that is, when any layer of electrode material is coated, the piezoelectric material corresponding to the electrode layer is subjected to crystallization polarization treatment.

[0082] Among them, since there may be a breakdown phenomenon in the polarization process during the step of crystallization polarization of the piezoelectric material, which makes the intensity of the electric field too high, this process will have an adverse effect on the electrode layer. Therefore, performing crystallization polarization treatment before preparing the electrode layer can better avoid the adverse effect on the electrode layer during the crystallization polarization treatment, thereby improving the performance of the piezoelectric fiber to a high degree. In addition, the use of layer-by-layer crystallization polarization method is helpful to improve the effect of crystallization polarization of multilayer piezoelectric fibers, thereby improving the performance of the piezoelectric fibers to a high degree.

[0083] In addition, before the step of crystallization polarization treatment of the piezoelectric material, the piezoelectric material is heat treated to remove the solvent. When the piezoelectric material is a piezoelectric polymer, the heat treatment temperature is 4h to 10h; when the piezoelectric material is a piezoelectric ceramic and a piezoelectric polymer, or a piezoelectric ceramic, the heat treatment time is 4h to 10h, and the heat treatment is 100°C to 120°C. By controlling the temperature and time of the heat treatment, the solvent is volatilized, which is helpful for the subsequent crystallization polarization step and ensures the effectiveness of the crystallization polarization.

[0084] Moreover, since the ion source of corona polarization is unilateral, during the step of crystallization polarization treatment, the conductive fiber core is rotated around the axis, and the rotation period is set to 6 to 10 weeks, and the process time is 5 minutes to 16 minutes, so that the ions can fully act on different areas of the piezoelectric material, the polarization uniformity of the piezoelectric fiber is higher, and the polarization effect is better.

[0085] Furthermore, the preparation method of coating the electrode material on the outside of the piezoelectric material includes one of dipping, evaporation, and magnetron sputtering.

[0086] In a third aspect, an embodiment of the present application discloses a piezoelectric sensor, which includes the piezoelectric fiber of the first aspect, or is prepared by the preparation method of the second aspect.

[0087] The piezoelectric fiber and its preparation method, and the piezoelectric sensor of the embodiment of the present application are further described below in conjunction with more specific embodiments.

[0088] Embodiment 1:

[0089] The present application provides a piezoelectric fiber, in which the number of piezoelectric layers and electrode layers is one, the surface roughness of the conductive fiber core is 400nm, the ratio of the thickness of any piezoelectric layer to the diameter of the conductive fiber core is 0.1, and the structure of the conductive fiber core includes a conductive inner core and a coupling agent layer wrapped on the outer surface of the conductive inner core, the thickness of the coupling agent layer is 100nm, and the ratio of the surface roughness of the conductive fiber core to the diameter of the conductive fiber core is 0.004.

[0090] The method for preparing the piezoelectric fiber comprises the following steps:

[0091] Plasma cleaning is performed on a conductive inner core with a diameter of 0.1 mm, and a coupling material is coated on the outer surface of the conductive inner core to form a coupling agent layer to obtain a conductive fiber core, wherein the coupling material has a solid content of 10% and a viscosity of 260 mPa.s, and the coupling material includes polyacrylic acid and methoxysilane in a mass ratio of 1:2, and the conductive inner core is a metal core;

[0092] The piezoelectric material is mixed with a solvent to form a slurry, and the conductive fiber core is placed in the slurry to coat the outer surface of the conductive fiber core with the piezoelectric material, wherein the viscosity of the slurry is 1000 mpa.s, the impregnation speed is 700 mm / min, and the piezoelectric material is a composite material formed by a piezoelectric polymer with a mass content of 30% and a piezoelectric ceramic with a mass content of 70%;

[0093] Drying at 100 °C for 4 h to remove the solvent in the piezoelectric layer;

[0094] The piezoelectric material was subjected to crystallization polarization treatment, the conductive fiber core was partially grounded, and negative ions were adsorbed on the piezoelectric layer through the corona area of ​​the in-situ polarization device. At the same time, the conductive fiber core was rotated 7 times along the axis. The process time was 12 minutes.

[0095] The outer surface of the piezoelectric layer is coated with an electrode material to form an electrode layer.

[0096] Embodiment 2:

[0097] The only difference between this embodiment and the first embodiment is that the ratio of the thickness of the piezoelectric layer to the diameter of the conductive fiber core is 0.15.

[0098] Embodiment three:

[0099] The only difference between this embodiment and the first embodiment is that the number of layers of the piezoelectric layer and the electrode layer is three.

[0100] Embodiment 4:

[0101] The only difference between this embodiment and the first embodiment is that the surface of the conductive inner core is etched by chemical etching to obtain a conductive fiber core, and the conductive fiber core does not include a coupling agent layer.

[0102] Embodiment five:

[0103] The only difference between this embodiment and the first embodiment is that the thickness of the coupling agent layer is 500 nm.

[0104] Embodiment six:

[0105] The only difference between this embodiment and the first embodiment is that the thickness of the coupling agent layer is 50 nm.

[0106] Embodiment seven:

[0107] The only difference between this embodiment and the first embodiment is that, in the step of coating the outer surface of the conductive fiber core with a piezoelectric material layer, the viscosity of the slurry is 800 mPa.s.

[0108] Embodiment eight:

[0109] The only difference between this embodiment and the first embodiment is that in the step of coating the outer surface of the conductive fiber core with a piezoelectric material layer, the immersion speed is 300 mm / min.

[0110] Comparative Example 1:

[0111] The difference between this comparative example and Example 1 is that the piezoelectric fiber is prepared by an electrospinning process, and the specific preparation process is as follows:

[0112] The piezoelectric material is formed into a filament under high voltage, collected by a filament winding mechanism, and subjected to polarization treatment to obtain a filament structure;

[0113] Folding a single filamentous structure into a sheet-like structure;

[0114] Printed electrode layers are distributed on both sides of the sheet structure.

[0115] Comparative Example 2:

[0116] The difference between this comparative example and Example 1 is that the outer surface roughness of the conductive fiber core is 900 nm.

[0117] Test result 1:

[0118] The piezoelectric properties and mechanical properties of the piezoelectric fibers prepared in Examples 1 to 8 and Comparative Examples 1 to 2 were tested, and the test results are shown in Table 1 below.

[0119] Table 1 Piezoelectric properties and mechanical flexibility data of the embodiments and comparative examples

[0120] Serial number Voltage (mV) Bending times Embodiment 1 5190 13000 Embodiment 2 7001 18000 Embodiment 3 15580 12000 Embodiment 4 5146 8000 Embodiment 5 5090 16000 Embodiment 6 5280 12000 Embodiment 7 5010 13000 Embodiment 8 4632 13500 Comparative Example 1 2000 700 Comparative Example 2 3790 6000

[0121] Analysis of the data of Examples 1 to 8 and Comparative Examples 1 and 2 shows that the performance of the examples is better than that of Comparative Example 1. This is because the outer surface of the piezoelectric layer of the example is directly wrapped with the electrode layer, so the contact area between the piezoelectric layer and the electrode layer is larger, and the electrical signal of the piezoelectric layer can be fully transmitted to the electrode layer, which helps to improve the conversion rate of electrical signals and mechanical signals and improve the sensitivity of signal detection and collection of the piezoelectric fiber; the performance of the example is better than that of Comparative Example 2. This is because the surface roughness of the conductive fiber core of the example is within the scope of the present application, so it is more conducive to the coating of the piezoelectric layer, so that the bonding force between the piezoelectric layer and the conductive fiber core is good, and the coating uniformity is high, which helps to improve the mechanical properties and piezoelectric properties of the piezoelectric fiber.

[0122] Analysis of the data of Example 1 and Example 2 shows that the thickness of the piezoelectric layer and the diameter of the conductive fiber core of Example 1 and Example 2 are both in the range of 0.05 to 0.15, so the thickness of the piezoelectric layer covering the guide fiber core is appropriate, so that the piezoelectric layer is more sensitive to external mechanical signals and the stress of the piezoelectric fiber is appropriate, so that the prepared piezoelectric fiber has higher mechanical and piezoelectric properties.

[0123] Analysis of the data of Example 1 and Example 3 shows that the performance of Example 3 is better than that of Example 1. This is because Example 3 has more layers and is more sensitive to external signals, which helps to further improve the performance of the piezoelectric fiber.

[0124] Analysis of the data of Example 1, Example 4 to Example 6 shows that the bending resistance of Example 1, Example 5 and Example 6 is better than that of Example 4. This is because the conductive fiber cores of Example 1, Example 5 and Example 6 all contain a coupling agent layer, and the thickness of the coupling agent layer is in the range of 50nm to 1000nm. Therefore, the coupling agent layer can not only reduce the surface roughness of the conductive fiber core, so that the piezoelectric layer and the conductive fiber core have better adhesion, but also serve as a bridge. Through chemical bonding, the connection stability between the conductive fiber core and the piezoelectric layer is higher, which is more conducive to improving the mechanical flexibility of the piezoelectric fiber.

[0125] Analysis of the data of Example 1 and Example 7 shows that the performance of Example 1 is better than that of Example 7. This is because the viscosity of the slurry of Example 1 is greater than that of Example 7, which helps to reduce the difficulty of coating the piezoelectric material on the outer surface of the conductive fiber core, making the piezoelectric layer in Example 1 more uniformly coated on the conductive fiber core, and is more helpful to improve the performance of the piezoelectric fiber.

[0126] Analysis of the data of Example 1 and Example 8 shows that the performance of Example 1 is better than that of Example 8. This is because the impregnation speed of Example 1 is greater than that of Example 8. Therefore, Example 1 can effectively avoid the possibility of impurities entering the piezoelectric layer during the impregnation process and make the thickness of the piezoelectric layer appropriate, thereby improving the performance of the piezoelectric fiber to a greater extent.

[0127] The piezoelectric fiber and its preparation method, and the piezoelectric sensor disclosed in the embodiments of the present application are introduced in detail above. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the piezoelectric fiber and its preparation method, and the piezoelectric sensor: At the same time, for general technicians in this field, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A piezoelectric fiber, characterized in that: The piezoelectric fiber includes: a conductive fiber core, a piezoelectric layer and an electrode layer alternately coated on the outer surface of the conductive fiber core, wherein the innermost layer coated on the outer surface of the conductive fiber core is the piezoelectric layer, and the outermost layer away from the conductive fiber core is the electrode layer, the number of layers of the piezoelectric layer and the electrode layer are at least one, and the surface roughness of the conductive fiber core is less than 500nm.

2. The piezoelectric fiber according to claim 1, characterized in that The ratio of the surface roughness of the conductive fiber core to the diameter of the conductive fiber core is less than 0.

1.

3. The piezoelectric fiber according to claim 1, characterized in that: The ratio of the thickness of any piezoelectric layer to the diameter of the conductive fiber core is 0.05 to 0.15; and / or, The diameter of the conductive fiber core is 0.05 mm to 1 mm.

4. The piezoelectric fiber according to claim 1, characterized in that: The structure of the conductive fiber core comprises a conductive inner core and a coupling agent layer coated on the outer surface of the conductive inner core.

5. The piezoelectric fiber according to claim 4, characterized in that: The material of the conductive inner core includes metal fiber or carbon fiber; and / or, The piezoelectric material of the piezoelectric layer includes at least one of piezoelectric ceramics and piezoelectric polymers; and / or, The electrode material of the electrode layer includes at least one of silver and 3,4-ethylenedioxythiophene monomer; and / or, The coupling material of the coupling agent layer includes at least one of methacrylate and methoxysilane; and / or, The thickness of the coupling agent layer is 50nm to 1000nm.

6. A method for preparing a piezoelectric fiber according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: Alternately coating the outer surface of the conductive fiber core with piezoelectric material and electrode material in sequence to form the piezoelectric layer and the electrode layer; The innermost layer coated on the outer surface of the conductive fiber core is the piezoelectric layer, and the outermost layer away from the conductive fiber core is the electrode layer.

7. The preparation method according to claim 6, characterized in that: Before the step of alternately coating the outer surface of the conductive fiber core with piezoelectric material, the preparation method further comprises: cleaning the conductive inner core, coating the outer surface of the conductive inner core with coupling material to form a coupling agent layer.

8. The preparation method according to claim 7, characterized in that: The solid content of the coupling material is 6% to 12%, and the viscosity of the coupling material is 1 mpa.s to 500 mpa.s.

9. The preparation method according to claim 6, characterized in that: The step of alternately coating the outer surface of the conductive fiber core with piezoelectric material comprises: Mixing the piezoelectric material with a solvent to form a slurry, placing the conductive fiber core in the slurry to coat the outer surface of the conductive fiber core with the piezoelectric material; The viscosity of the slurry is 800 mpa.s to 1500 mpa.s, and the immersion speed of the conductive fiber core in the slurry is 300 mm / min to 1500 mm / min.

10. The preparation method according to claim 9, characterized in that: In the slurry, the particle size of the piezoelectric material is less than 1 μm.

11. The preparation method according to claim 9, characterized in that: When the piezoelectric material is a piezoelectric ceramic, the solid content of the slurry is 60% to 80%; Alternatively, when the piezoelectric material is a piezoelectric polymer, the solid content of the slurry is 5% to 20%; Alternatively, when the piezoelectric material is a piezoelectric polymer and a ceramic material, the mass content of the piezoelectric polymer in the slurry is 5% to 20%, and the mass content of the piezoelectric ceramic in the slurry is 60% to 80%.

12. The preparation method according to claim 6, characterized in that: After the step of alternately coating the outer surface of the conductive fiber core with piezoelectric materials in sequence and before the step of coating the electrode material, the preparation method further comprises: performing a crystal polarization treatment on the piezoelectric material: Alternatively, after the step of coating the electrode material, the preparation method further comprises: performing a crystal polarization treatment on the piezoelectric material.

13. The preparation method according to claim 12, characterized in that: In the step of performing crystal polarization treatment on the piezoelectric material, the rotation period during polarization is 6 to 10 cycles, and the process time is 5 minutes to 16 minutes.

14. A piezoelectric sensor, characterized in that: The piezoelectric sensor comprises the piezoelectric fiber according to any one of claims 1 to 5, or is prepared by the preparation method according to any one of claims 6 to 13.

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