TW201332171A - Method for fabricating piezoelectric composite material and piezoelectric power generating device - Google Patents

Abstract

The invention relates to a method for fabricating piezoelectric composite material comprising steps of mixing a piezoelectric ceramic powder, an adhesive, a cross-linking agent, a lubricant and a plasticizer to form a slurry; extruding the slurry to form a piezoelectric ceramic green fiber; sintering the piezoelectric ceramic green fiber to form the piezoelectric ceramic fiber; arranging the piezoelectric ceramic fiber in a mold according to a predetermined volumetric content; and adding a polymer into the mode to form a polymer matrix of piezoelectric composite material. A piezoelectric power generating device including a piezoelectric power generating element made of the piezoelectric composite material is also provided.

Description

Piezoelectric composite process and piezoelectric power generation device

The present invention relates to piezoelectric composites, and more particularly to the fabrication of piezoelectric composites.

Traditional piezoelectric materials are mostly block types, their texture is hard and brittle, and the electromechanical conversion output is limited, which limits the development and application of piezoelectric materials. Piezoelectric composite materials combine the excellent piezoelectric properties of piezoelectric ceramics with the flexibility of polymers, which can greatly improve their piezoelectricity and mechanical properties, and further expand the application of piezoelectric materials.

Common methods for the manufacture of piezoelectric composite materials include laser cutting-filling, injection molding, demolding, and alignment casting. The laser cutting-filling method uses laser light to cut a plurality of lateral grooves on the piezoelectric ceramic block, and then uses the laser light to cut a plurality of longitudinal grooves intersecting the lateral grooves on the piezoelectric ceramic block to form A plurality of piezoelectric ceramic columns are then filled with a polymer in the trench to form a piezoelectric composite. Compared with the traditional cutting-filling method using a diamond cutter, this method has the advantages of high precision, no contact and easy operation. However, the disadvantage is the high cost of the equipment, and the thermal effects of the laser tend to cause the ceramic material to rupture and affect the structure and properties of the material.

The injection molding method uses a syringe having a plurality of tubular discharge ports to form an array of piezoelectric ceramic columns on a piezoelectric ceramic plate, followed by sintering, and then filling the array with a polymer to form a piezoelectric composite. This method has the advantages of flexible size control of the size, distribution and volume content of the piezoelectric ceramic column. However, the disadvantage is that the construction of the syringe is complicated and the length of the piezoelectric ceramic column is limited.

The demolding method uses a mold having a plurality of columnar cavities on which a piezoelectric ceramic column array is demolded, followed by sintering, and then the polymer is filled in the array to form a piezoelectric composite. The advantage of this method is that the mold is simple to manufacture and inexpensive. However, the disadvantage is that when the diameter of the piezoelectric ceramic column is less than 100 μm, the thermal stress during sintering tends to collapse the piezoelectric ceramic column array.

The alignment casting method first manufactures piezoelectric ceramic fibers, and then arranges the piezoelectric ceramic fibers in a predetermined volume content, and places them into a mold; and deposits an adhesive such as epoxy resin into the mold, and demolds after solidification to form 1-3 type piezoelectric composite material. The arrangement casting method has simple process, easy control of fiber volume content and low porosity, and is suitable for high-performance sensors, drivers and the like.

At present, in the manufacture of piezoelectric ceramic fibers, for example, a sol-gel method, a colloidal suspension spinning method (VSSP), and an extrusion molding method are common methods. The extrusion molding method uniformly mixes the piezoelectric ceramic powder with the binder and the aqueous solution of the crosslinking agent to form a polymer colloid. Next, the polymer colloid is extruded by an extruder to form a ceramic fiber green body. Then, a drying and sintering step is performed to form a piezoelectric ceramic fiber. Although this method is simple in process, low in cost, and does not cause environmental pollution, it has disadvantages such as difficulty in extrusion and poor plasticity of fibers.

In addition, the 1-3 type piezoelectric composite material is a two-phase piezoelectric composite material formed by a one-dimensionally connected piezoelectric ceramic fiber phase and arranged in parallel in a three-dimensionally connected polymer matrix phase. Increasing the size of the piezoelectric generating element can increase the amount of power generation. There is still a demand in the market for piezoelectric power generation elements having high power generation and long-term vibration without cracking the surface.

In view of the above, the present inventors have made great efforts to improve and solve the above-mentioned shortcomings, and have finally made a proposal to rationally and effectively improve the above-mentioned defects.

An object of the present invention is to provide a process for piezoelectric composite material, which can smoothly extrude a piezoelectric ceramic fiber, and the plasticity of the extruded piezoelectric ceramic fiber is good; and the piezoelectric composite made by the process of the invention When the material is used to manufacture a piezoelectric power generation element, it has a high power generation amount and does not crack after long-term vibration.

Another object of the present invention is to provide a piezoelectric power generator comprising a piezoelectric power generating element made of the above piezoelectric composite material.

In order to achieve the above object, the present invention is a method for preparing a piezoelectric ceramic fiber, the method comprising the steps of: mixing a piezoelectric ceramic powder, a binder, a crosslinking agent, a lubricant, and a plasticizer to form a slurry; The slurry is subjected to an extrusion molding step to form a piezoelectric ceramic fiber green embryo; the piezoelectric ceramic fiber green embryo is subjected to a sintering step to form a piezoelectric ceramic fiber; and the piezoelectric ceramic fiber is arranged according to a predetermined volume content Into the mold; and the adhesive is poured into the mold to form a piezoelectric composite.

Furthermore, the present invention is a piezoelectric power generating apparatus comprising: a support table; a metal plate having first and second surfaces opposite to each other, one end of the metal plate being fixed on the support table; and at least one piezoelectric generating element adjacent On the first surface and/or the second surface of the metal plate, the piezoelectric generating element is made of the above piezoelectric composite material.

Compared with the prior art, the process of the present invention mainly utilizes the addition of a lubricant and a plasticizer, can be smoothly extruded, and the plasticity of the extruded fiber is good, and the ratio of the two phases in the piezoelectric composite material is adjusted. A piezoelectric generating element having a high power generation amount and having no surface crack after long-term vibration is used for use in a piezoelectric power generator. The invention has the advantages of simple process, low cost and no environmental pollution, and can be applied to the manufacture of thin and long piezoelectric generating elements.

The detailed description and technical content of the present invention are set forth in the accompanying drawings.

Referring to the first drawing, the first drawing shows a schematic flow chart of the process of the piezoelectric composite material in a preferred embodiment of the present invention. In this embodiment, a piezoelectric ceramic fiber is produced by an extrusion molding method and a piezoelectric composite material is produced by an alignment casting method. First, please refer to step 100 in the first figure, using a mixer to uniformly mix 70% by weight to 95% by weight of piezoelectric ceramic powder, 3.5 to 20% by weight of a binder, 0.5 to 5% by weight of an aqueous solution of a crosslinking agent, 0.5 to 2.5 wt% of the lubricant and 0.5 to 2.5 wt% of the plasticizer to form a slurry.

The piezoelectric ceramic powder may have the chemical formula ABO ₃ . In the chemical formula ABO ₃ , A may be lead, lanthanum, strontium, potassium or lithium, and B may be titanium, zirconium, manganese, cobalt, niobium, iron, zinc, magnesium. , yttrium, tin, nickel or tungsten. The piezoelectric ceramic powder suitable for the present embodiment may have a size of 0.1 to 1.0 μm and a weight percentage of 70 to 95% by weight.

Suitable binders may be methylcelluloses such as methylcellulose, hydroxypropylmethylcellulose; polyvinyl alcohols such as polyvinyl alcohol, polyvinyl acetate; or polyacrylates. The weight percentage of the binder may range from 3.5 to 20% by weight.

The crosslinking agent can be an aqueous solution containing boric acid, borate, phosphate, citrate or aluminate. The borate may include sodium borate or potassium borate. Phosphates can include sodium phosphate, potassium phosphate or manganese phosphate. The citrate may include sodium citrate, potassium citrate or aluminum citrate. The aluminate may include sodium aluminate or potassium aluminate. The crosslinking agent may be an aqueous solution having a concentration of 0.005 to 0.05 M, and the weight percentage thereof is 0.5 to 5 wt%. When the cross-linking agent is dissolved in water, the charged alkaline hydroxide can form a three-dimensional network cross-linking with the binder, and at the same time, the ceramic powder bundle is coated therein to form a compact three-dimensional network after the spontaneous dehydration reaction. Composite structure.

A suitable lubricant may be glycerol or dipropylene glycol, which may range from 0.5 to 2.5% by weight. An appropriate amount of lubricant promotes extrusion and prevents the slurry from sticking to the inner walls and holes of the extruder used in subsequent steps.

The plasticizer may be selected from the group consisting of polyethylene glycol, 1,3 butanediol, 1,4 butanediol and phenyl alcohol. The weight percentage of the plasticizer is between 0.5 and 2.5% by weight. The right amount of plasticizer improves the plasticity of the extruded fiber to the desired specification.

Next, in step 102, the powder contained in the slurry is rolled into a fine powder by a three-roller. Next, step 104 is extrusion molded using an extruder to form a piezoelectric ceramic fiber green body of a desired specification. The extrusion pressure of extrusion can be between 1 and 50 kg/cm ² . Piezoelectric ceramic fiber embryos can range in diameter from 75 to 1,000 microns.

Next, in step 106, the fibrous green embryos are dried by a drying oven at a temperature of 80 to 120 ° C to remove water contained in the fibrous green embryos.

Next, in step 108, zirconium powder is coated on the surface of the dried fibrous green embryo to increase the surface abrasion resistance, and placed on an alumina substrate and placed in a crucible.

Next, in step 110, the fibrous green embryos placed in the crucible are sintered at a temperature of 1,000 to 1,300 ° C for 2 to 3 hours through a sintering furnace, and sintered to become piezoelectric ceramic fibers.

The piezoelectric ceramic fiber has been determined to have a diameter of about 250 μm, a length of 70 to 100 mm, a roundness error of 0.07+0.001 μm/1 mm, a true straightness error of 0.25 μm/100 mm, a sintered density of more than 99%, and a pressure. The electrical strain constant d _{33 is} greater than 600 pC/N.

Next, in step 112, the piezoelectric ceramic fibers are arranged in a volume of 35% to 85%, and placed in a mold. The higher the volume content of the piezoelectric ceramic fibers contained in the piezoelectric composite material, the higher the piezoelectric strain constant d ₃₃ is. Moreover, the periodic arrangement and non-periodic arrangement of piezoelectric ceramic fibers in the piezoelectric composite material also affect the thickness resonance mode of the piezoelectric element, and the non-periodic arrangement makes the thickness resonance mode simple without affecting other properties.

Next, in step 114, an adhesive is poured into the mold, vacuumed for 30 to 40 minutes, and cured at 160 to 180 ° C for 6 to 9 hours, and then demolded to form a 1-3 type piezoelectric composite material. A suitable adhesive can be an epoxy resin or an oxime resin. The epoxy resin adhesive is prepared by selecting an epoxy resin as a matrix and adding a curing agent to the matrix at a weight ratio of matrix:curing agent of 3:1. The curing agent may be maleic anhydride or hexahydroortho Phthalic anhydride, if necessary, may be added with a diluent such as dioctyl phthalate to dilute the epoxy resin, and the amount of the diluent is 1% by weight of the epoxy resin.

In order to test the performance of the piezoelectric composite, the piezoelectric composite was cut into 2 mm thick sheets, then smoothed, and covered with silver electrodes, placed in eucalyptus oil at 1.5 to 2.5 kV/mm, temperature 100 ° C, 15 The piezoelectric composite was polarized for ~25 minutes. The piezoelectric composite has a d ₃₃ greater than 300 pC/N.

Next, please refer to the second drawing, which is a schematic view of the piezoelectric power generating device of the first embodiment of the present invention. The piezoelectric power generator 20 of the present invention includes a support base 22, a metal plate 24, and a piezoelectric generating element 26. The metal plate 24 has a first surface 241 and a second surface 242 opposite to each other. One end 24a of the metal plate 24 is fixed on the support table 22; the piezoelectric generating element 26 is adjacent to the first surface 241 of the metal plate 24, and is pressed. The electric power generating element 26 is made of the above piezoelectric composite material, and the piezoelectric generating element 26 has a plate shape and may have a length of 3 to 10 cm, preferably 10 cm, and a thickness of 30 to 3 mm. Further, the mass block 30 may be placed on the first surface 241 of the other end 24b of the metal plate 24 to increase the vibration of the piezoelectric generating element 26. The mass 30 can have a mass of 0.5 to 10 grams.

Next, please refer to the third drawing, which is a schematic view of a piezoelectric power generating apparatus according to a second embodiment of the present invention. The piezoelectric power generator 20 of the present invention includes a support base 22, a metal plate 24, and piezoelectric generator elements 26 and 28. The piezoelectric generating element 26 is adjacent to the first surface 241 of the metal plate 24, and the piezoelectric generating element 28 is adjacent to the second surface 242 of the metal plate 24. The piezoelectric generating elements 26 and 28 are made of the piezoelectric composite material described above. The piezoelectric generating elements 26 and 28 are plate-shaped and may have a length of 3 to 10 cm, preferably 10 cm, and a thickness of 30 to 3 mm. Further, the mass 30 is placed on the first surface 241 of the other end 24b of the metal plate 24 to increase the vibration of the piezoelectric generating elements 26, 28.

Next, please refer to the fourth drawing, which is a schematic view of a piezoelectric power generating apparatus according to a third embodiment of the present invention. The piezoelectric power generator 20 of the present invention includes a support base 22, a metal plate 24, and a piezoelectric generating element 26. The metal plate 24 has a first surface 241 and a second surface 242 opposite to each other, and one end 24a of the metal plate 24 is fixed to the support table 22. The piezoelectric generating element 26 is adjacent to the first surface 241 of the metal plate 24, and the piezoelectric generating element 26 is made of the above piezoelectric composite material. The piezoelectric generating element 26 has a plate shape and can be 3 to 10 cm in length. Preferably, it is 10 cm and the thickness can be 30 micrometers to 3 millimeters. The two masses 30, 32 are placed on the first surface 241 and the second surface 242 of the other end 24b of the metal plate 24, respectively, to increase the vibration of the piezoelectric generating element 26.

Next, please refer to FIG. 5, which is a schematic view of a piezoelectric power generator according to a fourth embodiment of the present invention. The piezoelectric power generator 20 of the present invention includes a support base 22, a metal plate 24, and piezoelectric generator elements 26 and 28. The metal plate 24 has a first surface 241 and a second surface 242 opposite to each other, and one end 24a of the metal plate 24 is fixed to the support table 22. The piezoelectric generating element 26 is adjacent to the first surface 241 of the metal plate 24, and the piezoelectric generating element 28 is adjacent to the second surface 242 of the metal plate 24. The piezoelectric generating elements 26 and 28 are made of the piezoelectric composite material described above. The piezoelectric generating elements 26 and 28 are plate-shaped and may have a length of 3 to 10 cm, preferably 10 cm, and a thickness of 30 to 3 mm. The two masses 30, 32 are placed on the first surface 241 and the second surface 242 of the other end 24b of the metal plate 24, respectively, to increase the vibration of the piezoelectric generating elements 26, 28.

The above is only the preferred embodiment of the present invention, and is not intended to limit the scope of the invention, and other equivalent variations of the patent spirit of the present invention are all within the scope of the invention.

100~114. . . step

20. . . Piezoelectric generator

twenty two. . . Support table

twenty four. . . Metal plate

24a. . . One end of a metal plate

24b. . . One end of a metal plate

26. . . Piezoelectric generating element

28. . . Piezoelectric generating element

30. . . Mass block

32. . . Mass block

241. . . First surface

242. . . Second surface

The first figure is a flow chart showing the process of a piezoelectric composite material in a preferred embodiment of the present invention.

The second drawing shows a schematic view of a piezoelectric power generator of a first embodiment of the present invention.

The third diagram is a schematic view showing a piezoelectric power generator of a second embodiment of the present invention.

The fourth figure is a schematic view showing a piezoelectric power generator of a third embodiment of the present invention.

Fig. 5 is a schematic view showing a piezoelectric power generator of a fourth embodiment of the present invention.

100~114. . . step

Claims (20)

A process for piezoelectric composites, comprising the steps of:
(a) mixing a piezoelectric ceramic powder, a binder, a crosslinking agent, a lubricant, and a plasticizer to form a slurry;
(b) performing an extrusion molding step on the slurry to form a piezoelectric ceramic fiber green body;
(c) performing a sintering step on the piezoelectric ceramic fiber green body to form a piezoelectric ceramic fiber;
(d) arranging the piezoelectric ceramic fibers in a mold according to a predetermined volume content; and
(e) An adhesive is poured into the mold to form a piezoelectric composite. The process of claim 1, wherein the lubricant in the step (a) is glycerol or dipropylene glycol, and the weight percentage of the lubricant is between 0.5 and 2.5% by weight. The process of claim 1, wherein the plasticizer in the step (a) is selected from the group consisting of polyethylene glycol, 1,3 butanediol, 1,4 butanediol, and phenyl alcohol. The group of constituents has a weight percentage of the plasticizer of 0.5 to 2.5% by weight. The process of the piezoelectric composite material of claim 1, wherein the piezoelectric ceramic powder in the step (a) has a chemical formula ABO ₃ , and in the chemical formula ABO ₃ , A can be lead, lanthanum, lanthanum, lanthanum ( Strontium), potassium or lithium, B may be titanium, zirconium, manganese, cobalt, niobium, iron, zinc, magnesium, yttrium, tin, nickel or tungsten, the weight of the piezoelectric ceramic powder The percentage is between 70 and 95% by weight. The process of claim 1, wherein the piezoelectric ceramic powder in the step (a) has a size of 0.1 to 1.0 μm. The process of the piezoelectric composite of claim 1, wherein the binder in the step (a) is methylcellulose or hydroxypropylmethylcellulose, and the weight percentage of the binder is between 3.5 and 20% by weight. The process of claim 1, wherein the crosslinking agent in the step (a) is an aqueous solution containing boric acid, borate, phosphate, citrate or aluminate, and the crosslinking agent is in a concentration. An aqueous solution between 0.005 and 0.05M. The process of claim 4, wherein the weight percentage of the crosslinking agent in the step (a) is between 0.5 and 5% by weight. The process of claim 1, wherein the pressing pressure in the step (b) is between 1 and 50 kg/cm ² . The process of claim 1, wherein the piezoelectric ceramic fiber preform in the step (b) has a diameter of between 75 and 1,000 microns. The process of claim 1, wherein the sintering temperature in the step (c) is between 1,000 and 1,300 °C. The process of the piezoelectric composite material of claim 1, further comprising performing a drying step before the step (c), the temperature of the drying step being between 80 and 120 °C. The process of claim 1, wherein the volume fraction in the step (d) is from 35% to 85%. The process of claim 1, wherein the adhesive in the step (e) is an epoxy resin or an oxime resin. A piezoelectric power generating device comprising:
a support table;
a metal plate having a first surface and a second surface opposite to each other, one end of the metal plate being fixed on the support table; and at least one piezoelectric generating element adjacent to the first surface of the metal plate and/or On the second surface, the piezoelectric generating element is made of the piezoelectric composite material of claim 1. The piezoelectric power generator of claim 15, wherein the two piezoelectric generating elements are respectively adjacent to the first surface and the second surface of the metal plate. A piezoelectric power generator according to claim 15 or 16, further comprising a mass placed at the other end of the metal plate. The piezoelectric power generating device of claim 15 or 16, further comprising two masses respectively disposed on the first surface and the second surface of the other end of the metal plate. The piezoelectric power generator of claim 15, wherein the piezoelectric generating element is plate-shaped and has a length of 3 to 10 cm. The piezoelectric power generator of claim 15, wherein the piezoelectric generating element has a thickness of 30 μm to 3 mm.