• Steel and Composite Structures
• /
• 제49권4호
• /
• pp.361-380
• /
• 2023

A size dependent bending behavior of piezoelectrical flexoelectric layered perforated functionally graded (FG) composite nanobeam rested on an elastic foundation is investigated analytically. The composite beam is composed of regularly cutout FG core and two piezoelectric face sheets. The material characteristics is graded through the core thickness by power law function. Regular squared cutout perforation pattern is considered and closed forms of the equivalent stiffness parameters are derived. The modified nonlocal strain gradient elasticity theory is employed to incorporate the microstructure as well as nonlocality effects into governing equations. The Winkler as well as the Pasternak elastic foundation models are employed to simulate the substrate medium. The Hamiltonian approach is adopted to derive the governing equilibrium equation including piezoelectric and flexoelectric effects. Analytical solution methodology is developed to derive closed forms for the size dependent electromechanical as well as mechanical bending profiles. The model is verified by comparing the obtained results with the available corresponding results in the literature. To demonstrate the applicability of the developed procedure, parametric studies are performed to explore influences of gradation index, elastic medium parameters, flexoelectric and piezoelectric parameters, geometrical and peroration parameters, and material parameters on the size dependent bending behavior of piezoelectrically layered PFG nanobeams. Results obtained revealed the significant effects both the flexoelectric and piezoelectric parameters on the bending behavior of the piezoelectric composite nanobeams. These parameters could be controlled to improve the size dependent electromechanical as well as mechanical behaviors. The obtained results and the developed procedure are helpful for design and manufacturing of MEMS and NEMS.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2000년도 하계학술대회 논문집
• /
• pp.877-880
• /
• 2000

The length extensional vibration mode of a piezoelectric ceramic substrate is used in fabricating the ultra-small size resonators and filters. In general, the three side ratios of the substrate effect the resonant characteristics of the resonator using its length extensional vibration. In this paper, their relationships are studied. We know that changing the ratio of its length to its width makes possible to change the resonant frequency of the width vibration without degrading the length extensional vibration.

• Coupled systems mechanics
• /
• 제12권4호
• /
• pp.337-364
• /
• 2023

The Rayleigh wave propagation is considered in the structure of the functionally graded piezoelectric material (FGPM) layer over the elastic substrate. The elastic substrate loosely bonds the layer through a corrugated interface, whereas its upper boundary is also corrugated but stress-free. Additionally, the solutions for the FGPM layer and substrate are derived using the fundamental variable separable approach to convert the partial differential equation to an ordinary differential equation. The results with boundary conditions lead to dispersion relations for the electrically open and electrically short cases in the determinant form. The outcomes have been numerically analyzed using a specific model. The findings were presented in the form of graphs, which were created using Mathematica 7. Graphs are plotted for variations in wavenumber and phase velocity. The outcomes may help measure interface defects and design Surface Acoustic Wave (SAW) devices.

• 한국재료학회지
• /
• 제29권6호
• /
• pp.371-377
• /
• 2019

A flexible piezoelectric energy harvester(f-PEH) that converts tiny mechanical and vibrational energy resources into electric signals without any restraints is drawing attention as a self-powered source to operate flexible electronic systems. In particular, the nanocomposites-based f-PEHs fabricated by a simple and low-cost spin-coating method show a mechanically stable and high output performance compared to only piezoelectric polymers or perovskite thin films. Here, the non-piezoelectric polymer matrix of the nanocomposite-based f-PEH is replaced by a P(VDF-TrFE) piezoelectric polymer to improve the output performance generated from the f-PEH. The piezoelectric hybrid nanocomposite is produced by distributing the perovskite PZT nanoparticles inside the piezoelectric elastomer; subsequently, the piezoelectric hybrid material is spin-coated onto a thin metal substrate to achieve a nanocomposite-based f-PEH. A fabricated energy device after a two-step poling process shows a maximum output voltage of 9.4 V and a current of 160 nA under repeated mechanical bending. Finite element analysis(FEA) simulation results support the experimental results.

• Journal of Electrical Engineering and Technology
• /
• 제5권4호
• /
• pp.640-645
• /
• 2010

This paper describes the power generating property of hydrothermally grown ZnO nanorods on a flexible polyethersulfone (PES) substrate. The piezoelectric currents generated by the ZnO nanorods were measured when bending the ZnO nanorod by using I-AFM, and the measured piezoelectric currents ranged from 60 to 100 pA. When the PtIr coated tip bends a ZnO nanorod, piezoelectrical asymmetric potential is created on the nanorod surface. The Schottky barrier at the ZnO-metal interface accumulates elecntrons and then release very quickly generating the currents when the tip moves from tensile to compressed part of ZnO nanorod. These ZnO nanorods were grown almost vertically with the length of 300-500 nm and the diameter of 30-60 nm on the Ag/Ti/PES substrate at $90^{\circ}C$ for 6 hours by hydrothermal method. The metal-semiconductor interface property was evaluated by using a HP 4145B Semiconductor Parameter Analyzer and the piezoelectric effect of the ZnO nanorods were evaluated by using an I-AFM. From the measured I-V characteristics, it was observed that ZnO-Ag and ZnO-Au metal-semiconductor interfaces showed an ohmic and a Schottky contact characteristics, respectively. ANSYS finite element simulation was performed in order to understand the power generation mechanism of the ZnO nanorods under applied external stress theoretically.

• Advances in materials Research
• /
• 제8권3호
• /
• pp.237-257
• /
• 2019

The present article researches large-amplitude thermal free vibration characteristics of nonlocal two-phase piezo-magnetic nano-size beams having geometric imperfections by considering piezoelectric reinforcement scheme. The piezoelectric reinforcement can cause an enhanced vibration behavior of smart nanobeams under magnetic field. All previous studies on vibrations of piezoelectric-magnetic nano-size beams ignore the influences of geometric imperfections which are crucial since a nanobeam is not always ideal or perfect. Nonlinear governing equations of a smart nanobeam are derived based on classical beam theory and an analytical trend is provided to obtain nonlinear vibration frequency. This research shows that changing the volume fraction of piezoelectric phase in the material has a great influence on vibration behavior of smart nanobeam under electric and magnetic fields. Also, it can be seen that nonlinear vibration behaviors of smart nanobeam is dependent on the magnitude of exerted electric voltage, magnetic imperfection amplitude and substrate constants.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2004년도 추계학술대회 논문집
• /
• pp.447-449
• /
• 2004

The purpose of this study is measured surface acoustic wave(SAW) characteristics to confirm utilization possibility as SAW sensor using new Pb(Mg$_{1}$3/Nb$_{2}$3/) $O_3$-PbTiO$_3$ (PMN-PT) piezoelectric substrate. We have tried to see if the material can be practically available as a new surface acoustic wave (SAW) biosensor to detect protein. The experimental results clarified that the frequency filtering of the central frequency of the PMN-PT substrate is a superior result to that of the LiTaO$_3$ (LT) substrate, but the result was not completely satisfactory. We know there is a problem in the design of inter-digital transducer (IDT) pattern. The waves transferred through the input terminal forms SAW which is sure to be transferred to the direction of the output terminal and the backward direction of the input terminal. This reflected wave is reiterated with SAW, which is transferred to the output direction, and so the frequency filtering gives a not good result. The electromechanical coupling coefficient of the PMN-PT substrate is excellent, and we can use it as a SAW sensor, in the near future, provided that there will be a new IDT design to increase the frequency filtering.

• 한국분말재료학회지
• /
• 제22권5호
• /
• pp.331-336
• /
• 2015

We report on the succesful fabrication of ZnO nanorod (NR)-based robust piezoelectric nanogenerators (PNGs) by using Cu foil substrate. The ZnO NRs are successfully grown on the Cu foil substrate by using all solution based method, a two step hydrothermal synthesis. The ZnO NRs are grown along c-axis well with an average diameter of 75~80 nm and length of $1{\sim}1.5{\mu}m$. The ZnO NRs showed abnormal photoluminescence specrta which is attributed from surface plasmon resonance assistant enhancement at specific wavelength. The PNGs on the SUS substrates show typical piezoelectric output performance which showing a frequency dependent voltage enhancement and polarity dependent charging and discharging characteristics. The output voltage range is 0.79~2.28 V with variation of input strain frequency of 1.8~3.9 Hz. The PNG on Cu foil shows reliable output performance even at the operation over 200 times without showing degradation of output voltage. The current output from the PNG is $0.7{\mu}A/cm^2$ which is a typical out-put range from the ZnO NR-based PNGs. These performance enhancement is attributed from the high flexibility, high electrical conductivity and excellent heat dissipation properties of the Cu foil as a substrate.

• 대한전자공학회논문지SD
• /
• 제42권1호
• /
• pp.9-17
• /
• 2005

공진주파수 스펙트럼법을 이용하여 ZnO 와 AIN 압전박막의 임피던스 특성 및 전기기계결합계수 특성에 대해 조사하였다. 압전박막의 두께가 얇을수록 전체적인 임피던스 응답 피크의 크기가 감소하였으며, 기판의 두께가 얇을수록 응답 피크의 모드 수가 감소하는 것이 관찰되었다. 입력 Kt² 값으로부터 평가된 Kt² 값을 통해 압전박막의 두께보다 기판의 두께 변화에 대한 영향이 더 큼을 알 수 있었고, 기판의 acoustic 임피던스에 의해서도 Kt² 값이 감소함을 알 수 있었다. 전극 효과가 첨가되면 임피던스 응답 피크의 크기가 감소하였으며, 전극의 acoustic 임피던스가 커짐에 따라 응답피크는 더 작아졌다. 공진주파수 스펙트럼법에서 전극은 질량부하로 고려되기 때문에 전극 효과가 첨가된 경우 Keff² 값은 증가하며, 전극의 acoustic 임피던스가 크면 그 효과는 더 커졌다. 공진주파수 스펙트럼법을 이용한 시뮬레이션을 통해 기판, 압전체, 전극으로 이루어진 composite 공진기의 특성 분석과 설계까지도 가능함을 알 수 있었다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 학술대회 논문집 전문대학교육위원
• /
• pp.35-39
• /
• 2001

The purpose of this paper is improvement the piezoelectric of Polyvinylidene fluoride(PVDF) organic thin films is fabricated by vapor deposition method. The piezoelectric of PVDF organic thin films attributed to dipole orientation in crystalline region. Also, the piezoelectric characteristic reduced that dipole moments orientation in crystalline region interfered with impurity carriers. Therefore, PVDF organic thin films fabricated with high substrate temperature condition for crystallinity improvement. The crystallinity of PVDF organic thin films fabricated by this condition increase from 47 to 67.8%. The ion density of PVDF organic thin films fabricated by substrate temperature variation from $30^{\circ}C$ to $105^{\circ}C$ decreased from $1.62{\times}10^{16}cm^3$ to $6.75{\times}10^{11}cm^3$ when temperature and frequency were $100^{\circ}C$, 10Hz, respectively. The $d_{33}$ and piezo-voltage coefficient of PVDF organic thin films increased from 20pPC/N to 33pC/N and $162.9{\times}10^{-3}V{\cdot}m/N$ to $283.2{\times}10^{-3}V{\cdot}m/N$, respectively. For the sake of the applications of piezoelectric sensor, we analyzed the output voltage characteristic as a function of the distance between an oscillator of 28kHz and PVDF organic thin film transducer. From this, we found that the output voltage is inversely proportional to the distance. At this time, the period was about $35.798{\mu}s$ and equal the oscillator frequency.