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The current method for piezocomposite production is the dice-and-fill technique, which consists in cutting two sets of grooves in a block of piezoceramic at right angles each other, then a polymer is cast into these grooves and the solid ceramic base is ground off. Polishing and poling are the following steps in order to achieve the final thickness and properties. This method is expensive, time consuming and size limited.

As an alternative for the dice-and-fill technique, continuos green fibers obtained by the modified viscous-suspension-spinning process, can be bundled into a cottonball-like shape, then burned and sintered. The sintered bundle impregnated with epoxy resin can be sliced into discs and then polarized. Recent results have yielded 1-3 type composites with excellent piezoelectric properties.

On the other hand, an innovative process has been developed for Sr 2 (Nb 0.5 Ta 0.5 ) 2 O 7 /PVDF composites, in this new fabrication method, appropriate amounts of oxides are mixed, pressed and sintered. The porous resulting material is subsequently infiltrated with PVDF solution and then poled. This new method for composites preparation is simple and offers a lead-free alternative smart material.

Another kind of piezocomposites can be achieved by spinning films of piezoceramic onto metal alloys, such as TiNi. The resulting materials is a hybrid composite that can utilize the different active and adaptive properties of the individual bulk materials. Due to the shape memory nature of TiNi, a possible application for this new heterostructures could be smart active damping of mechanical vibrations. DC sputtering and spin coating are the techniques necessary for the smart thin film TiNi/piezoelectric heterostructures fabrication. However, eventhough the films had a fine grain structure and high mechanical qualities, the ferroelectric properties were poor compared to literature values.

In the future, the properties of piezocomposites will be tailored, by varying the ceramic, the polymer and their relative proportions. Adjustments in the material properties will lead to fulfillment of the requirements for a particular device. [link] shows a comparison among piezoelectric ceramics, polymers and composites parameters where Z is the impedance, ε t 33 is the dielectrical constant, and ρ is the density.

Parameter ranges for piezoelectric ceramics, polymers and composites.
Material parameter Piezoceramics Piezopolymers Piezocomposites
k t (%) 45 - 55 20 - 30 60 - 75
Z (10 6 Rayls) 20 - 30 1.5 - 4 4 - 20
ε t 33 0 200 - 5000 ~10 50 - 2500
tan γ (%) <1 1.5 - 5 <1
Q m 10 - 1000 5 - 10 2 - 50
ρ (10 3 kg/m 3 ) 5.5 - 8 1 - 2 2 - 5

Piezoelectric coatings.

Many potential applications exist which require film thickness of 1 to 30 μm. Some examples of these macroscopic devices include ultrasonic high frequency transducers, fiber optic modulators and for self controlled vibrational damping systems.

ZnO and PZT have been used for piezoelectric fiber optic phase modulators fabrication. The piezoelectric materials have been sputter deposited using dc magnetron source and multimagnetron sputtering systems. Coatings of 6 µm thick of ZnO and 0.5 µm of PZT are possible to achieve using these systems. However, thickness variation of approximately 15% occurs between the center and the end of ZnO coatings, results on affected modulation performance. Although PZT coatings achieved by sputtering posses uniformity and do not exhibit cracking, the PZT is only partially crystallized and it is actually a composite structure consisting of crystalline and amorphous material, diminishing the piezoelectric properties.

Sol-gel technique for thick PZT films have been developed. It is now possible to fabricate PZT sol-gel films of up to 60 µm. The electrical and piezoelectrical properties of the thick films reported are comparable with ceramic PZT.

Piezoelectric polymer coatings for high-frequency fiber-optic modulators have been also investigated. Commercial vinylidene fluoride and tetrafluoroethylene copolymer has been used. The advantage of using polymer coatings is that the polymer jacket (coating) can be easily obtained by melt extrusion on a single-mode fiber. Thus, uniformity is easily achieved and surface roughness is not present. Furthermore, if annealing of the polymer is made prior poling, a high degree of crystallinity is enhanced, leading to better piezoelectric properties.

Bibliography

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Questions & Answers

Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
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what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
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Professor
what is the stm
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Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
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What is meant by 'nano scale'?
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What is STMs full form?
LITNING
scanning tunneling microscope
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Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
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what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
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if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
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analytical skills graphene is prepared to kill any type viruses .
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what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
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yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
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why?
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what school?
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biomolecules are e building blocks of every organics and inorganic materials.
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anyone know any internet site where one can find nanotechnology papers?
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research.net
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Introduction about quantum dots in nanotechnology
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what does nano mean?
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nano basically means 10^(-9). nanometer is a unit to measure length.
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Source:  OpenStax, Chemistry of electronic materials. OpenStax CNX. Aug 09, 2011 Download for free at http://cnx.org/content/col10719/1.9
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