Browsing by Author "Chang, Harrison Hoon Seok"

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    Direct and converse magnetoelectic effect in laminate bonded Terfenol-D-PZT composites
    (Elsevier Science B.V., Amsterdam., 2007-09-20T00:00:00Z) Record, P. M.; Popov, C.; Fletcher, J.; Abraham, E.; Huang, Zhaorong; Chang, Harrison Hoon Seok; Whatmore, Roger W.
    Results from measurements of the direct and converse magnetoelectric (ME) effect on a three-layer, epoxy-bonded, laminate composite are presented. The laminae are a single transversely polarized piezoelectric elements (PZ29) sandwiched between two longitudinal-magnetic ally polarized magnetostrictive TD elements (Terfenol-D-TX GMM). The direct ME effect was determined by measuring laminate output with a Helmholtz-generated AC field (up to 7 Oe) in the range 50 Hz-100 kHz biased by a DC field (0-1000 Oe). Peak voltage output occurred at the sample's mechanical resonant frequency, its value depending on the strength and direction of the applied magnetic field. The peak output was 3061 mV at 3 Oe AC field and 1000 Oe bias, equivalent to 74.4 V cm(-1) Oe(-1). The peak output coefficient, however, was 93.6 V cm(-1) Oe(-1) at 0.1 Oe AC field and 1000 Oe DC bias. The reduction at higher drive amplitudes was attributed to increased Young's modulus of the TD phase. Anomalous peaks in the low frequency spectrum of sample's output are explained. The converse magnetoelectric effect was measured by recording the voltage induced in a solenoid encompassing the ME while exposed to a DC bias field and the PZ phase driven by a 10 VAC source. The peak output is shown to depend on the strength of the applied DC magnetic field and developed a maximum field of 15.4 Oe at the sample's mechanical resonant frequency. This equates to a converse magnetoelectric coefficient of 55 Oe cm kV (-1) (c) 2007 Elsevier B.V. All rights reserved.
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    Direct and converse magnetoelectric effect at resonant frequency in laminar piezoelectric-magnetostrictive composite.
    (Springer Science Business Media, 2008-02-01T00:00:00Z) Popov, C.; Chang, Harrison Hoon Seok; Record, P. M.; Abraham, E.; Whatmore, Roger W.; Huang, Zhaorong
    Laminar piezoelectric-magnetostrictive composites using piezoelectric lead zirconate titanate ceramics and the giant magnetostrictive rare-earth-iron alloy Terfenol-D were prepared by epoxy bonding. The direct and converse magnetoelectric (ME) effects at and off the mechanical resonant frequency were characterized and compared to the theoretical modelling. The mechanical resonant frequency of the composites depended on the sample orientation and the magnetic DC bias field. In the longitudinal configuration, the resonant frequency shifted down monotonically with the increasing bias field. When the sample was in the transverse configuration, the resonant frequency decreased with the increasing field at first. However, at higher bias, it shifted up with the increasing bias. A phenomenological model based on the à  E effect of magnetostrictive materials is proposed to explain the observed phenomena
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    Enhanced pyroelectric effect through product property and its applications
    (Cranfield University, 2009-10) Chang, Harrison Hoon Seok; Huang, Zhaorong
    Pyroelectric materials have the ability to generate electrical response when they experience a thermal stimulus. This has lead to their deployment in applications such as Infra-Red detectors/sensors, energy harvesting, and ferroelectric electron emission cathodes, among others. All the “Figures of merit” presented in the literature for assessing pyroelectric materials are proportional to the pyroelectric coefficient. Hence, enhancing this coefficient should improve the performance of the pyroelectric element in any application. This research has been conducted to find ways of enhancing the pyroelectric coefficient of a given material through product property in the secondary pyroelectric effect arising from thermal expansion coefficient mismatch. Analytical model for describing such enhancement in 2-2 connectivity laminate composites has been developed and simulated on Mathematics package Maple, while Finite Element Analysis package ANSYSR⃝ was used to perform thermo-structural analysis investigating the effect of bonding/interfacial layer on the strain transfer between the laminate layers. Indicators for judging the credentials of various pyroelectric materials in pyroelectric coefficient enhancement have been identified and evaluated for six different pyroelectric materials. These six pyroelectric materials were paired with six different non-pyroelectric materials to form thirty-six 2-2 connectivity laminate composites for the purpose of comparing pyroelectric coefficient enhancements, whereby various factors affecting the enhancement have been determined. Potential applications of this enhancement and what it may mean in terms of improvement in the outputs of these applications has been reviewed. In particular, two electrical boundary conditions, namely short and open circuit conditions, have been explored while the effects of thermal mass variation due to the introduction of non-pyroelectric layer have also been inspected. Experimental verification of pyroelectric coefficient enhancement under short circuit condition in Lead zirconate titanate/Stainless steel 2-2 connectivity laminate composites has been conducted with observed pyroelectric coefficient enhancements of more than 100 % while theoretical enhancements of up to 800 % is predicted in certain laminate composites of Lead zirconate titanate/Chlorinated polyvinyl chloride thermoplastic. Consideration of the open circuit condition pyroelectric coefficients and their enhancements revealed significant dissimilarities from their short circuit condition counterparts, prompting the need for more distinction to be made between the two than it has previously been thought. For instance, appraising employment credentials of pyroelectric elements in applications such as pyroelectric X-ray generation, electron accelerator, and nuclear fusion should involve the use of open circuit pyroelectric coefficient rather than the short circuit one. The effects of thermal mass has also been considered using quantities termed “Figures of merit for efficiency”, comparing the laminate composite’s thermal-to-electrical conversion efficiency to that of stand alone pyroelectric material. Up to twenty fold increase in thermal-to-electrical conversion efficiency under short circuit condition has been predicted in laminate composites of Lead zirconate titanate/Chlorinated polyvinyl chloride thermoplastic, insinuating a potential for increased employment of Lead zirconate titanate in areas such as pyroelectric sensors and pyroelectric energy harvesting. Pyroelectric energy harvesting application has been examined in detail as a potential beneficiary of this enhancement, with various analysis tools for assessing pyroelectric energy harvesting performance of a given pyroelectric element presented and evaluated. A pyroelectric energy harvesting system was designed as a hypothetical application of pyroelectricity and pyroelectric coefficient enhanced 2-2 connectivity laminate composites. Theoretical analysis confirms that large improvement in pyroelectric energy harvesting performance can be expected in Lead zirconate titanate materials by converting them into 2-2 connectivity laminate composites. The use of newly defined “New electrothermal coupling factor for composites” (k2 N ew) for assessing credentials of particular pyroelectric element in pyroelectric energy harvesting application has been proposed and vindicated while the experimental samples from the pyroelectric coefficient enhancement study were demonstrated to show significant improvement in their pyroelectric energy harvesting performance via pyroelectric coefficient enhancement. The analysis techniques used in this dissertation provide a methodology for assessing the potentials of particular pyroelectric material and its 2-2 connectivity laminate composites for applications under both short and open circuit conditions.
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    Laminate composites with enhanced pyroelectric effects for energy harvesting
    (Institute of Physics, 2010-06-30T00:00:00Z) Chang, Harrison Hoon Seok; Huang, Zhaorong
    A pyroelectric coefficient enhanced 2-2 connectivity laminate composites' energy harvesting credentials have been assessed. The use of the electrothermal coupling factor for laminate composites (k(Lam)(2)) for such an assessment has been appraised while the experimental samples are evaluated to show a significant improvement in their performance via pyroelectric coefficient enhancement, demonstrative of their great potential in energy harvesting applications. A lead zirconate titanate and stainless steel laminate composite with an 88% pyroelectric coefficient enhancement is shown to increase its maximum power density, efficiency, and electrothermal coupling factor by 254%, while other material pairings have also been evaluated to exhibit great promise in this application owing to a large pyroelectric coefficient enhancement accompanied by a reduction in total thermal mass.
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    Pyroelectric effect enhancement through product property under open circuit condition
    (American Institute of Physics, 2009-07) Chang, Harrison Hoon Seok; Huang, Zhaorong
    An analytical model for the pyroelectric (PY) effect under open circuit condition and 2-2 connectivity laminates of various pairs of PY and nonpyroelectric (NP)/elastic materials has been developed. It is evident from our analysis that there indeed is a substantial dissimilarity between the PY coefficients and figure of merit for efficiency for various PY-NP pairs under short circuit and open circuit conditions. We believe this implies that there should be a greater distinction made between the PY coefficients under these two electrical conditions than previously thought. The indicators for various PY-NP material pairs that can be utilized to determine their PY coefficient enhancement potential under open circuit condition have been identified. The investigated PY materials are lead zirconate titanate (PZT-5H and PZT-5A), barium titanate, lithium tantalate, lithium niobate, and polyvinylidene fluoride (PVDF), while the NP materials are stainless steel, polytetrafluoroethylene (PTFE or Teflon), chlorinated polyvinyl chloride thermoplastic (CPVC), aluminum, zinc, and Invar 36. Extraordinarily large PY coefficient of 97×10-4 C m-2 K-1 at minimum thickness ratio Rmin is expected for PZT-5H-CPVC pair while PVDF-CPVC could show increase in the secondary PY coefficient of up to 350%. In addition, where the figure of merit for efficiency is concerned, for the same volume of the composite PZT-5A-PTFE pair it reaches 24, a 24-fold increase in efficiency at Rmin. Our analysis techniques should provide a methodological way for appraising the potentials of particular PY material and its 2-2 laminates for applications under open circuit condition such as PY X-ray generation, electron accelerator, and nuclear fusion.
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    Substantial pyroelectric effect enhancement in laminated composites
    (American Institute of Physics, 2008-04) Chang, Harrison Hoon Seok; Huang, Zhaorong
    A mathematical model has been developed to determine the pyroelectric coefficient (PY coef.) enhancement through secondary pyroelectric effect, utilizing a 2-2 connectivity of the pyroelectric lead zirconate titanate (PZT) and elastic laminate layers. Based on the prediction of this analysis, laminar stainless steel (St) PZT/St structures have been fabricated and more than 100% enhancement in PY coef. has been observed in these structures. Good agreement between the theoretical and experimental results was obtained by taking into account of the stain transfer loss at the St and PZT interface.