Papers by Kimberly Cook-chennault
Polymers
Polymer-ceramic nanocomposite piezoelectric and dielectric films are of interest because of their... more Polymer-ceramic nanocomposite piezoelectric and dielectric films are of interest because of their possible application to advanced embedded energy storage devices for printed wired electrical boards. The incompatibility of the two constituent materials; hydrophilic ceramic filler, and hydrophobic epoxy limit the filler concentration, and thus, their piezoelectric properties. This work aims to understand the role of surfactant concentration in establishing meaningful interfacial layers between the epoxy and ceramic filler particles by observing particle surface morphology, piezoelectric strain coefficients, and resistivity spectra. A comprehensive study of nanocomposites, comprising non-treated and surface treated barium titanate (BTO), embedded within an epoxy matrix, was performed. The surface treatments were performed with two types of coupling agents: Ethanol and 3-glycidyloxypropyltrimethoxysilan. The observations of particle agglomeration, piezoelectric strain coefficients, and...
Novel three-phase piezoelectric composites that comprised lead zirconate titanate (PZT), aluminiu... more Novel three-phase piezoelectric composites that comprised lead zirconate titanate (PZT), aluminium and Portland cement were fabricated at a low poling voltage of 0 . 6 kV/mm and temperature of 1608C. Aluminium and PZT particles were distributed in a Portland cement matrix, and the dielectric constant, tan ä and strain coefficients were experimentally investigated as a function of inclusion volume fraction. The three-phase piezoelectric composites were found to possess higher piezoelectric strain coefficients, d 33 , than their two-phase counterparts (PZT and Portland cement composites). The highest value of d 33 observed for the three-phase composite was 8 . 1 pC/N for volume fractions of 0 . 7 and 0 . 2 for PZT and aluminium respectively, which was 164% of the value observed for the two-phase composite, at the same PZT volume fraction. An analytical model was used to predict values for the effective dielectric constant of the three-phase composites, and these values compared reasonably well to the empirical data. An investigation of sample degradation as a function of time was performed. Samples showed the highest degree of reduced dielectric performance occurred within two days of data capture, and minimal subsequent reduction in performance after 300 days. Electrical properties of the composites are influenced by the oxidation of aluminium by the alkaline constituents in the cement matrix, distribution of PZT and aluminium within the matrix, particle agglomeration, inclusion size, contact resistance between particles, and air voids. The increased dielectric and piezoelectric strain coefficients, demonstrate that these types of materials may be useful in applications such as structural health monitoring and energy harvesting.
Journal of Engineering Materials and Technology
Two-phase PZT-epoxy piezoelectric composites and three phase PZT-epoxy-Al composites were fabrica... more Two-phase PZT-epoxy piezoelectric composites and three phase PZT-epoxy-Al composites were fabricated using a poling voltage of 0.2 kV=mm. The influence of aluminum inclusion size (nano and micron) and (lead zirconate titanate) PZT volume fraction on the dielectric properties of the three phase PZT-epoxy-aluminum composites were experimentally investigated. In general, dielectric and piezoelectric properties of the PZTepoxy matrix were improved with the addition of aluminum particles. Composites that were comprised of micron scale aluminum inclusions demonstrated higher piezoelectric d 33 -strain-coefficients, and higher dielectric loss compared to composites that were comprised of nanosize aluminum inclusions. Specifically, composites comprised of micron sized aluminum particles and PZT volume fractions of 20%, 30%, and 40% had dielectric constants equal to 405.7, 661.4, and 727.8 (pC=N), respectively, while composites comprised of nanosize aluminum particles with the same PZT volume fractions, had dielectric constants equal to 233.28, 568.81, and 657.41 (pC=N), respectively. The electromechanical properties of the composites are influenced by several factors: inclusion agglomeration, contact resistance between particles, and air voids. These composites may be useful for several applications: structural health monitoring, energy harvesting, and acoustic liners.
Science of Advanced Materials
Three-phase, PZT(PbZr0.52Ti0.48O3)-Epoxy- Multi-walled Carbon-Nanotube (MWCNT) flexible films hav... more Three-phase, PZT(PbZr0.52Ti0.48O3)-Epoxy- Multi-walled Carbon-Nanotube (MWCNT) flexible films have been prepared via a combination solvent and spin coating technique. The composite materials were spin coated onto flexible stainless steel substrate, and either graphene or graphene - PMMA films were grown by a chemical vapor deposition process on the other side of the films. The thicknesses of the films were ~ 200 μm. The volume fraction of the MWCNTs was varied from 1% to 6%, while the PZT volume fraction was held constant at 30%. The strain coefficient and capacitance were measured as a function of the MWCNT volume fraction, and were subsequently used to determine the effective dielectric constant of the composite. Samples that incorporated graphene electrodes had higher effective dielectric constants than samples that incorporated graphene-PMMA electrodes and those with no top electrode. For example, the maximum values of effective dielectric constant for the composite films were ~...
Energy and Environment Focus, 2013
ABSTRACT Three-phase, PZT(PbZr0.52Ti0.48O3)-Epoxy-Multi-walled Carbon-Nanotube (MWCNT) flexible f... more ABSTRACT Three-phase, PZT(PbZr0.52Ti0.48O3)-Epoxy-Multi-walled Carbon-Nanotube (MWCNT) flexible films have been prepared via a combination solvent and spin coating technique. The composite materials were spin coated onto flexible stainless steel substrate, and either graphene or graphene-PMMA films were grown by a chemical vapor deposition process on the other side of the films. The thicknesses of the films were 200 μm. The volume fraction of the MWCNTs was varied from 1% to 6%, while the PZT volume fraction was held constant at 30%. The strain coefficient and capacitance were measured as a function of the MWCNT volume fraction, and were subsequently used to determine the effective dielectric constant of the composite. Samples that incorporated graphene electrodes had higher effective dielectric constants than samples that incorporated graphene-PMMA electrodes and those with no top electrode. For example, the maximum values of effective dielectric constant for the composite films were ∼4353, ∼1945 and ∼61, for samples having graphene, graphene-PMMA and no electrode respectively. Similarly, composite films with graphene electrodes produced strain coefficients, e.g., d 33 and d 31 that were larger than their counterparts. Sample surface morphology and sample composition were observed using SEM and measured using Raman Spectroscopy respectively. Improved dielectric properties observed for samples with graphene coatings are due to graphene's high carrier mobility and ability to readily conform to the surface of the sample.
Smart Materials and Structures, 2008
Power consumption is forecast by the International Technology Roadmap of Semiconductors (ITRS) to... more Power consumption is forecast by the International Technology Roadmap of Semiconductors (ITRS) to pose long-term technical challenges for the semiconductor industry. The purpose of this paper is threefold: (1) to provide an overview of strategies for powering MEMS via non-regenerative and regenerative power supplies; (2) to review the fundamentals of piezoelectric energy harvesting, along with recent advancements, and (3) to discuss future trends and applications for piezoelectric energy harvesting technology. The paper concludes with a discussion of research needs that are critical for the enhancement of piezoelectric energy harvesting devices.
An analytical expression for prediction of the effective dielectric constant of a three phase 0-3... more An analytical expression for prediction of the effective dielectric constant of a three phase 0-3-0 ferroelectric composite is presented. The analytical results are verified with the experimental results from Nan et al. (2002, “Three-Phase Magnetoelectric Composite of Piezoelectric Ceramics, Rare-Earth Iron Alloys, and Polymer,” Appl. Phys. Lett., 81(20), p. 3831). The analytical model is extended to include the shape of a third phase inclusion to examine the influence of the shape (of the inclusion) on the effective dielectric constant of the composite. The dielectric constant increases as much as seven times when the aspect ratio of the conducting inclusion particle is increased from 1 (sphere) to 10 (spheroid). A comparison of the analytical predictions with the experimental values, which indicate that the increase in aspect ratio of the inclusions has a significant effect on the overall dielectric constant of the composite.
Journal of Electroceramics, 2013
Thick film two phase, 0-3 composite PZT-epoxy dome-shaped structures have been fabricated for the... more Thick film two phase, 0-3 composite PZT-epoxy dome-shaped structures have been fabricated for the first time using a modified solvent and spin coating technique, where a PZT and ethanol solution was dispersed in an epoxy matrix, combined with a hardener, spin coated onto stainless steel sheets, and poled at~2.2 kV/mm. The electro-mechanical performances of the films were investigated as a function of volume fraction of PZT. The volume fraction of PZT was varied from 0.1 to 0.7 and the piezoelectric coefficients d 31 and d 33 , and the capacitance, C, were measured, and used to calculate the effective dielectric constants. The values for d 33 , d 31 , C and dielectric constant were 1.06 pC/N, 0.74 pC/N, 6.0 pF and 76.1 respectively, at 70 % volume fraction of PZT. The surface topography and morphology were examined via AFM and SEM. The piezoelectric strain coefficients, capacitance and effective dielectric constant increased with increasing PZT content, in addition to the surface roughness. Agglomeration of PZT particles and surface crevices were observed on sample surfaces, which are most likely due to surface tension and air bubbles formed during the mixing process.
Composites Part A: Applied Science and Manufacturing, 2012
Three phase epoxy/piezoelectric/conductive filler composites were fabricated. The volume fraction... more Three phase epoxy/piezoelectric/conductive filler composites were fabricated. The volume fraction of the conductive filler, aluminum, was held constant at 20%, while the volume fraction of the piezoelectric material, PZT was varied from 0.10 to 0.70. Three sets of composites were examined, wherein, the size of the aluminum constituent was varied from micron in size (200 mesh) to nano -in size ($18 nm). Both sets of composites presented enhanced loss factor (tan d) and piezoelectric coefficient (d33) values for volume fractions of PZT above 0.30 volume fraction. Composites having micron size aluminum particles exhibited higher loss factor and strain coefficients than those that incorporated nano-size aluminum particles, which could be due to several factors: agglomeration, contact resistance between particles, and excess air voids in the samples.
Bulletin of Science, Technology & Society, 2008
Providing efficient and clean power is a challenge for devices that range from the micro to macro... more Providing efficient and clean power is a challenge for devices that range from the micro to macro in scale. Although there has been significant progress in the development of micro-, meso-, and macro-scale power supplies and technologies, realization of many devices is limited by the inability of power supplies to scale with the diminishing sizes of CMOS-based technology. Here, the authors provide an overview of piezoelectric energy harvesting technology along with a discussion of proof of concept devices, relevant governing equations, and figures of merit. They present two case studies: (a) energy capture from the operation of a novel shear and elastic modulus indentation device subjected to applied voltage and (b) energy capture from vibrating commercial bimorph piezoelectric structures mounted on household appliances. Lastly, areas of development needed for realization of commercial energy harvesting devices are suggested.
Advances in Cement Research, 2014
Novel three-phase piezoelectric composites that comprised lead zirconate titanate (PZT), aluminiu... more Novel three-phase piezoelectric composites that comprised lead zirconate titanate (PZT), aluminium and Portland cement were fabricated at a low poling voltage of 0 . 6 kV/mm and temperature of 1608C. Aluminium and PZT particles were distributed in a Portland cement matrix, and the dielectric constant, tan ä and strain coefficients were experimentally investigated as a function of inclusion volume fraction. The three-phase piezoelectric composites were found to possess higher piezoelectric strain coefficients, d 33 , than their two-phase counterparts (PZT and Portland cement composites). The highest value of d 33 observed for the three-phase composite was 8 . 1 pC/N for volume fractions of 0 . 7 and 0 . 2 for PZT and aluminium respectively, which was 164% of the value observed for the two-phase composite, at the same PZT volume fraction. An analytical model was used to predict values for the effective dielectric constant of the three-phase composites, and these values compared reasonably well to the empirical data. An investigation of sample degradation as a function of time was performed. Samples showed the highest degree of reduced dielectric performance occurred within two days of data capture, and minimal subsequent reduction in performance after 300 days. Electrical properties of the composites are influenced by the oxidation of aluminium by the alkaline constituents in the cement matrix, distribution of PZT and aluminium within the matrix, particle agglomeration, inclusion size, contact resistance between particles, and air voids. The increased dielectric and piezoelectric strain coefficients, demonstrate that these types of materials may be useful in applications such as structural health monitoring and energy harvesting.
Three-phase piezoelectric composites that were comprised of PZT, nano-sized aluminum (18 nm) and ... more Three-phase piezoelectric composites that were comprised of PZT, nano-sized aluminum (18 nm) and Portland cement were prepared via a normal mixing and spreading method. The volume fraction of Al was held constant at 0.02, while the volume fraction of PZT was varied from 0.10 to 0.70. The dielectric constant, tan (δ), and piezoelectric coefficient were experimentally investigated as a function of PZT volume fraction were found to possess higher dielectric constants, than their two-phase counterparts (PZT and Portland cement). A comprehensive age study of the piezoelectric and dielectric properties is presented, where significant reductions in material performance occurred within 2 days of sample preparation, and to a lesser degree after 400 days for piezoelectric properties. Properties of the composites are believed to be influenced by the oxidation of aluminum by the alkaline constituents in the cement matrix, distribution of fillers within the cement matrix and air voids.
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Papers by Kimberly Cook-chennault