ENHANCED POLYVINYLIDENE FLUORIDE (PVDF) COMPOSITE WITH NEODYMIUM (ND) DOPED LEAD ZIRCONATE TITANATE (PZT) FILLER

Abstract

The present invention discloses a 0-3 piezoelectric ceramic-polymer composite material ideal for use as flexible sensor and actuator applications, and suitable to thrive in harsh conditions. The said piezoelectric composite of 0-3 connectivity comprises, a ferroelectric polymer matrix layer consisting of polyvinylidene fluoride (PVDF) or copolymers thereof; and a piezoelectric ceramic particle filler uniformly dispersed within said matrix layer comprising neodymium (Nd) doped lead zirconatetitanate (PZT) in a varying mole percentage ranging from 0 to 12 mole%.

Specification

Description:FIELD OF INVENTION:
[001] The present invention generally relates to the field of piezoelectric composites. More particularly, the present invention relates to a piezoelectric ceramic-polymer composite material ideal for use as flexible sensor and actuator applications, andsuitable to thrive in harsh conditions.

BACKGROUND AND PRIOR ART:
[002] Piezoelectric composite materials are engineered materials composed of an active and passive material to exhibit electromechanical properties that has widespread application across various industries. These composite materials comprise a matrix material and a reinforcing element to achieve specific performance characteristics. The said matrix material is selected from a polymer, metal, ceramic, or hybrid thereof, to act as a cohesive binder to surround and support the reinforcements. The said reinforcements is dispersed within the matrix and may include fibers (e.g., carbon, glass, aramid) or particles (e.g., ceramics, metals.

[003] These materials have a wide range of applications, including structural health monitoring, damage detection, vibration testing, microphone technology, and tactile sensors. Despite their widespread use, researchers have faced challenges in optimizing their performance, particularly in achieving comparable piezoelectric and ferroelectric properties to standalone piezoelectric ceramics.

[004] The ongoing efforts by researchers to enhance the piezoelectric and ferroelectric properties of these composites indicate a concerted push towards innovation and improvement in this field. This suggests that while the initial development of these composites marked a significant advancement, there is still room for further progress and refinement. Researchers are likely exploring various avenues such as refining manufacturing processes, investigating new composite formulations, and exploring novel materials and techniques to overcome existing limitations and enhance the performance of these materials.

[005] CN106495559A discloses a 0-3 type composite piezoelectric device and method, comprising ceramic phase piezoelectric and piezopolymer, wherein said ceramic phase piezoelectric material surface is coated by Graphene powder to increase the electrical conductivity.

[006] Existing composite materials may incorporate both piezoelectric ceramics and polymers to achieve desired properties. However, achieving uniform dispersion of ceramic particles within the polymer matrix and optimizing the interface between the phases can be challenging, leading to variations in performance and reliability.

[007] Thus, there is a need to address the drawbacks such as difficulty in achieving uniform dispersion, interface compatibility issues, potential performance inconsistencies in piezoelectric composites.

[008] The present invention thus discloses an improved piezoelectric composite that combines the advantages of both ceramics and polymers in a composite material, to enhance the ferroelectric, piezoelectric, and mechanical properties of the material and ensure enhanced suitability for sensors, actuators and energy harvesting devices.

SUMMARY OF THE INVENTION:
[009] It is an object of the present invention to enhance the ferroelectric, piezoelectric, and mechanical properties of the composite material.

[010] It is another object of the present invention to improve performance and provide flexibility, shapeability, and enhanced durability, by incorporating piezoelectric ceramic particles into a flexible polymer matrix.

[011] It is another object of the present invention to provide a piezoelectric composite for use in flexible sensor and actuator applications and in harsh conditions.

[012] It is yet another object of the present invention to incorporate Nd-doped PZT into the composite, to enhance itsferroelectric and piezoelectric properties and overall performance of the composite.

[013] Accordingly, the present invention provides a piezoelectric composite of 0-3 connectivity comprising, a ferroelectric polymer matrix layer consisting of polyvinylidene fluoride (PVDF) or copolymers thereof; and a piezoelectric ceramic particle filler (PNZT) uniformly dispersed within said matrix layer, comprising neodymium (Nd) doped lead zirconatetitanate (PZT).

[014] In an aspect, since the filler PNZT is dispersed in PVDF Solution, so the connectivity of filler is taken as zero and 3 for PVDF solution.

[015] Further, the composition ratio, microstructure, crystallinity, and phase distribution of the composite material according to the present invention, enhance the piezoelectric and ferroelectric properties of saidpiezoelectric composite material.

BRIEF DESCRIPTION OF DRAWINGS:
[016] The figures below show an exemplary embodiment:
Figure 1: Depicts the Composite of PVDF-PNZT
Figure 2: Depicts the XRD patterns of PVDF(1-X ) - ( X )PNZT samples with x = 0.00 - 0.12 mole%. No impurities were observed along with the PVDF and PNZT phase for co-substituted samples up to x = 0 - 12 mole%. PNZT phase are prominent with increase in PNZT concentration in the sample. The distinct peaks corresponding to the planes (100) & (120) around 21.93o, 55.19o corresponds rhombohedral phase. Tetragonal phase observed at 31.03o,38.34o ,44.59o and 50.07o diffraction peak corresponds to (110),(111),(002)and (200)plane respectively. The crystallite size has been calculated using the Scherrer's formula. The crystallite size are 22.05nm, 20.07 nm, 21.13 nm, 21.64 nm, 21.85 nm and 22.12nm for 2,4,6,8,10 and 12 mole% respectively. The lattice parameter increases with the increase in PNZT concentration more than 6 mole% in the sample. The maximum lattice strain is at 6 mole% of PNZT in the composite.
Figure 3: Depicts the SEM of (1-x) PVDF -(x) PNZT,(a)x = 0mole%,(b)x = 4mole% , (c) x = 6mole%,(d)x = 8mole% (e) x = 10mole% (f)x =12mole%. The surface morphology of PVDF-PNZT piezocomposite prepared in 0-3 connectivity has been studied for various composition i.e.(1-x)PVDF-(x)PNZT , x = 2,4,6,8,10 and 12 mole% by SEM is shown in figure 3.The micrograph shows PNZT particle are dispersed uniformly in the PVDF matrix. As shown in the figure the surface shows clear grain and grain boundaries. The size of the grains decease with increase in PNZT concentration in the composite up to 6 mole% then increases. The minimum grain size is obtained for 6 mole% of PNZT in the composite. The size of the grains are in μm range, where as size of the crystallite is nm range. This is due to the sample is polycrystalline in nature.
Figure 4: Depicts FTIR spectra of (1-x) PVDF -(x) PNZT,(a)x = 2mole%, (b)x=4mole% ,(c) x=6mole%,(d)x=8mole% (e) x=10mole% (f)x=12mole%. The absorption curve of the Fourier Transform Infrared Spectroscopy (FTIR) of (1-x) PVDF - ( x )PNZT system with x = 2-12 mole% samples for 650-1600 cm-1 wave number range is shown in figure 4 . Due to relative intensity of PNZT peaks as compared to the peaks of PVDF only some intense peaks of PVDF phase has been observed. The perovskite phase of PZT has been attributed by the vibration modes around at 660cm -1. The vibrational band around at 781cm-1, 820cm-1 observed due to γ phase. The vibration bands correspond to α phase is obtained around at 871 cm−1. The β phase is obtained at 1049cm-1and 1260 cm-1. The band at 1260cm-1 corresponds to the CH2 bending vibration. The β phase content is found to be enhanced with the PNZT addition in the composite.
Figure 5: Depicts the Raman spectra of (1-x) PVDF - (x) PNZT,(a) x = 2mole%,(b) x = 4mole% ,(c) x = 6mole%,(d) x = 8mole% (e) x =10mole% and (f) x=12mole%. The Raman spectra of PVDF-PNZT composite for x= 2-12 mole% composition for 100-1500 cm-1 wave number range is shown in figure 5.The peak in the Raman spectra observed at 173cm-1,233cm-1and 334cm-1 correspond to PZT phase. The Raman spectra at 417 cm-1,666cm-1,750cm-1 and 1037cm-1 corresponds to α phase of PVDF. The peaks at 288cm-1,523cm-1,863cm-1, 1147cm-1 and 1290cm-1 in Raman spectra corresponds to β phase. The phase at 816 cm-1 correspond γ phase of PVDF. The Raman peak at 910cm-1 and 1422cm-1 α, β and γ phase of PVDF composite. Raman spectra also show the enhanced β phase as observed in XRD and FTIR.
Figure 6: Depicts the P-E loop of (1-x) PVDF -(x) PNZT,(a)x = 2mole%,(b)x = 4mole% , (c) x= 6mole%,(d)x = 8mole% (e) x = 10mole% (f) x =12mole% (Ferroelectric studies)
Figure7: Depicts the Polarization and coercive field of (1-x) PVDF -(x) PNZT with x = 2-12 mole%. Polarization verses electric field of (1-x) PVDF -(x) PNZT of x =2-12 mole% is shown in figure 7. .Obtained remnant polarization and coercieve field of different mole% of PNZT in the composite is shown in figure 7. With the increase in the applied field the polarization increases which is shown in the figure.Maximum remnant polarization and coercieve field is obtained for 6mole% of PNZT in the composite. Structural analysis of the composite with different mole% shows that the polar phase represented by β is enhanced for 6mole% PNZT in the composite.
Figure8: Depicts the Variation of Piezoelectric co-efficient with Applied force of (1-x) PVDF -(x) PNZT,(a)x = 2mole%,(b)x=4mole% ,(c) x=6mole%,(d)x=8mole% (e) x=10mole% (f)x=12mole%. Variation of linear piezoelectric co-efficient (d33) with applied force for (1-x) PVDF -(x) PNZT, x = 2 -12 mole% is shown in figure8. Here 5% instrumental error was included. The applied force generates pressure in the materials. The pressure generates charge in the piezoelectric material. With increase in applied force the piezoelectric co-efficient increases in respect of composition. Maximum piezoelectric co-efficient is obtained for 6 mole% of PNZT in the composite. This composition shows enhanced β phase obtained from the structural analysis. So this composition with enriched β phase shows enhanced piezoelectric properties as compared to other composition [182].The piezoelectric co-efficient is 51 at 245 pC/ N.
Figure 9: Storage Modulus verses temperature of (1-x)PVDF-(x) PNZT, x =0,6 and12 mole%. Stored energy and loss modulus represent the elastic portion and energy dissipation in a viscoelastic material. Storage modulus of (1-x)PVDF- (x) PNZT, x = 2,6 and 12 mole% is shown in figure 9.Non linear decrease of storage modulus with increase in temperature of the pure PVDF as well as the composite.The storage modulus increases with the increase in PNZT concentration in the sample.Maximum storage modulus was obtained for 6mole% of PNZT in the composite.So the maximum elastic properties was obtained for this composition (Dynamical Mechanical Analysis).
Figure 10: Loss Modulus verses temperature of(1-x)PVDF-(x) PNZT, x = 0 -12 mole%. Loss modulus of (1-x)PVDF-(x) PNZT, x = 2,6 and 12 mole% is shown in figure 10. Maximum loss modulus was also decreased by the raise in temperature of the sample.The energy dissipation as heat also decrease by the raise in temperature of the sample. Minimum dissipation was obtained for 6 mole% of PNZT in the composite.

Figure 11 : Depicts the DMA Curves of tan 𝛅 verses temperature of (1-x)PVDF -(x) PNZT, x =0 -12 mole%. Mechanical loss factor which is the ratio of loss moduls to storage modulus of the sample. Mechanical loss factor(tanδ) of (1-x)PVDF-(x) PNZT, x = 2,6 and 12 mole% is shown in figure 11. Pure PVDF shows two peak. The peak around at 100oC in pure PVDF is decreased with increase in PNZT in the composite. 6mole% of PNZT shows minium loss factor tan𝛅.
Figure 12: 2D AFM images (1-X) PVDF-(X) PNZT for x = 0, 6 and 12 mole% is shown in (a),(c),(e) and 3D AFM images (1-X) PVDF-(X) PNZT for x = 0, 6 and 12 mole% is shown in (b),(d) and (f). Atomic force microscopy is used to study the topographic image of PVDF-PNZT composite. Figure 12(a),(c) and (e) represents the 2D figure of x= 0,6 and 12 mole%. The grains size is nm for 0mole%, where as the grain size of 6 and 12 mole% are in µm range. The roughness of the surface is calculated from scan area of 2500 sqμm. The average roughness of the surface (Ra) for 0, 6 and 12 mole% of PNZT in the composite was 0.21, 2.00 and 1.01μm. Increase in PNZT concentration increase and then decrease the roughness composite. Anti-fouling performance increases where as efficient filtration of the surface was decreased. So it decreases the hydrophicity of the membrane surface. It leads to increase the fouling properties with no development of permeate flux.

DETAILED DESCRIPTION OF THE INVENTION:
[017] The present invention will now be described in detail with reference to optional and preferred embodiments so that various aspects of the invention will be more clearly understood, however, should not be construed to limit the scope of the invention. The following embodiments clearly and completely describes various technical features and advantageous of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. The examples used herein are intended merely to facilitate an understanding of the ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

[018] The present invention relates to an improved polyvinylidene fluoride (PVDF) composite configured to enhance the piezoelectric and ferroelectric properties, while maintaining mechanical integrity and flexibility. The present invention provides a polyvinylidene fluoride (PVDF) composite matrix, with neodymium (Nd) doped lead zirconatetitanate (PZT) filler, to enhance its ferroelectric, piezoelectric, mechanical properties and overall performance of the composite.

[019] Further, the doping with Nd improves the coercive field and other key properties, making it suitable for harsh condition applications.

[020] In a preferred embodiment according to the present invention, a piezoelectric composite of 0-3 connectivity comprises, A ferroelectric polymer matrix layer consisting of polyvinylidene fluoride (PVDF) or copolymers thereof; and a piezoelectric ceramic particle filler uniformly dispersed within said matrix layer consisting of neodymium (Nd) doped lead zirconatetitanate (PZT).

[021] In a same preferred embodiment according to the present invention, said neodymium (Nd) doped lead zirconatetitanate (PZT) is dispersed within said polyvinylidene fluoride (PVDF) matrix layer, in a varying mole percentage ranging from 0 to 12 mole%, to achieve the desired balance of properties, such as enhanced piezoelectric coefficient, remnant polarization, coercive field , and mechanical strength.

[022] In a same preferred embodiment according to the present invention, said piezoelectric ceramic filler layer concentration varies from 0 to 12 mole% across different composite samples.

[023] In a same preferred embodiment according to the present invention, said piezoelectric ceramic particle filler has a crystallite size ranging from 20-22nm, for optimizing piezoelectric performance, ferrolectric properties, and mechanical strength for applications in sensors, actuators, and energy harvesting devices.



[024] In a same preferred embodiment according to the present invention, said composite has an average surface roughness (Ra) ranging from 0.21 to 1.01μm, for optimizing electrical contact, mechanical stability, and performance across sensors, actuators, transducers, and energy harvesting devices.

[025] In a same preferred embodiment according to the present invention, said composite may comprise additives or modifiers, to further enhance specific properties or address performance limitations or improve the interface between the PVDF matrix and PZT filler.

[026] In a same preferred embodiment according to the present invention said composite may optionally comprise a coupling agent configured to enhance the interface between said ferroelectric polymer matrix layer and piezoelectric ceramic filler layer.

[027] To increase the performance of composite materials, the present invention optionally comprises the coupling agent such as KH-560, which has the chemical formula C9H20O5Si.KH-560 hydrolyses to create silanolgroups, which can then react with inorganic compounds to make siloxanes. The functional groups on the opposite end of the molecule can form bonds with organic molecules.

[028] In a same preferred embodiment according to the present invention, said composite may be fabricated into thin films, sheets, fibres or moulded components.

[029] In a preferred embodiment the present invention disclose the preparation of piezoelectric composite of 0-3 connectivity comprising ,

(i) Synthesizing the PVDF-PNZT composite by solvent cast process wherein PVDF is dissolved in DMF (diemthyl formamide) at a temperature in the range of 45-60°C with stirring and followed by sonication at same temperature to obtain a thoroughly dispersed solution of PVDF-PNZT; and Casting the prepared solution.

[030] In a same preferred embodiment according to the present invention,said composite is prepared by mixing PVDF with 0 to 12 mole% concentration of the Nd-doped PZT filler.

[031] In a same preferred embodiment according to the present invention,wherein at least one processing parameter selected from group consisting of temperature, pressure, and shear rate is adjusted to control the microstructure and properties of the composite.

[032] In an exemplary embodiment according to the present invention, said PNZT material exhibits a maximum energy density of 0.92067 J/cm3 for 6 mole % of PNZT at an applied electric filed strength of 200kV/cm.

[033] In an exemplary embodiment according to the present invention, said PNZT ceramic material exhibits an efficiency of 68% when containing 6 mole% of PNZT at an applied electric filed strength of 200kV/cm.

[034] In an exemplary embodiment according to the present invention, said PNZT material exhibits a piezoelectric co-efficient of 51 at 245 pC/N for 6 mole% of PNZT at an applied electric filed strength of 200kV/cm.

[035] In an exemplary embodiment according to the present invention, said PNZT material exhibits a maximum storage modulus and minimum mechanical loss factor for 6 mole% of PNZT in the composite.

[036] The structural and electrical and mechanical properties of (1-x) PVDF-(x) PNZT with x = 0 -12 mole% composite has been studied. Perovskite phase is observed with slight shift in the peak position by doping. The peaks corresponds to their respective planes. α, β. γ phase of PVDF in the composite which are also observed in the XRD pattern. The least crystallite size and grain size was obtained for 6 mole% of PNZT in the composite. Maximum β fraction was obtained for 6 mole% of PNZT in the composite. Remnant polarization and coercive filed was maximum for 6 mole% of PNZT in the composite. Maximum energy density up to 0.92067 and efficiency of 68% for 6 mole% of PNZT in the composite was observed at 200kV/cm of applied electric field. The piezoelectric co-efficient of 51 at 245 pC/ N for 6 mole% of PNZT in the composite was obtained. Maximum Storage Modulus and minimum mechanical loss factor was obtained for 6 mole% of PNZT in the composite

[037] The advantages of the present invention are:
 Piezoelectric Properties: Generate electric charge from mechanical stress, suitable for use in various sensing and actuation applications, including structural health monitoring, damage detection, vibration testing, and tactile sensing.
 Flexibility and Versatility :It is flexible and can be shaped or molded into various forms, making them suitable for integration into complex structures and wearable devices. These composites can also conform to curved surfaces or irregular shapes.
 Enhanced Durability: The polymer matrix provides mechanical reinforcement and protection to the piezoelectric ceramic particles, increasing overall durability compared to standalone ceramics.
 Tailored Properties: Composition and processing parameters can be adjusted to customize performance characteristics such as sensitivity, response time, and operational temperature range.
 Multi functionality: Exhibit additional desirable characteristics such as dielectric behaviour, thermal stability, and chemical resistance.
 Cost-Effectiveness: These composites provide cost advantages over traditional piezoelectric materials, when considering factors such as material waste reduction, processing efficiency, and scalability, depending on the specific application and manufacturing processes employed.

[038] The foregoing descriptions are merely specific embodiments of the present invention, but are not intended to limit the protection scope of the present invention. Any variation or replacement readily figured out by a person skilled in the art within the technical scope disclosed in the present invention shall fall within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

, Claims:
1. A piezoelectric composite of 0-3 connectivity comprising, A ferroelectric polymer matrix layer consisting of polyvinylidene fluoride (PVDF) or copolymers thereof; and a piezoelectric ceramic particle filler uniformly dispersed within said matrix layer consisting of neodymium (Nd) doped lead zirconate titanate (PZT).

2. The composite as claimed in claim 1, wherein said neodymium (Nd) doped lead zirconatetitanate (PZT) is dispersed within said polyvinylidene fluoride (PVDF) matrix layer, in a varying mole percentage ranging from 0 to 12 mole%.

3. The composite as claimed in claim 1, wherein said piezoelectric ceramic filler layer concentration is 0,2,4,6,8,10 and 12 mole%.

4. The composite as claimed in claim 1, wherein said piezoelectric ceramic particle filler has a crystallite size ranging from 20-22nm.

5. The composite as claimed in claim 1, wherein said composite has an average surface roughness (Ra) ranging from 0.21 to 1.01μm.

6. The composite as claimed in claim 1, wherein said composite may comprise additives or modifiers.

7. The composite as claimed in claim 1, wherein said composite may be fabricated into thin films, sheets, fibres or moulded components.

8. A process for the preparation of piezoelectric composite of 0-3 connectivity comprising a) synthesizing the PVDF-PNZT composite by solvent cast process wherein PVDF is dissolved in DMF (diemthyl formamide) at a temperature in the range of 45-60°C with stirring and followed by sonication at same temperature to obtain a thoroughly dispersed solution of PVDF-PNZT; and b) casting the prepared solution.

9. The process as claimed in claim 10, wherein said composite is prepared by mixing PVDF with 0 to 12 mole% concentration of the Nd-doped PZT filler.

10. Use of the composite as claimed in any one of the preceding claims in various sensing and actuation applications

Documents