• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.333-333
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• 2010

압전형 에너지 하베스팅 소자는 외부에서 버려지는 기계적 진동 혹은 타격과 관련된 에너지로부터 전기 에너지를 획득할 수 있다는 잇점이 있다. 그러나 현재 이 방식으로부터 획득될 수 있는 에너지는 매우 작다는 단점이 있다. 이러한 문제들을 해결하기 위하여 본 연구에서는 두 가지 형태의 압전 소재를 제작하였다. 에너지 하베스팅 소자용 고효율 압전 세라믹와 결정배향된 세라믹을 제작하고 이에 대한 성능을 조사하였다. 결정 배향된 세리믹에서는 1 N의 외부 충격조건에서 소재가 100 V, 1 mW의 전력을 발생하였다.

• JSTS:Journal of Semiconductor Technology and Science
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• v.6 no.3
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• pp.125-130
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• 2006

The optical gain and the luminescence of a ZnO quantum well with MgZnO barriers is studied theoretically. We calculated the non-Markovian optical gain and the luminescence for the strained-layer wurtzite quantum well taking into account of the excitonic effects. It is predicted that both optical gain and luminescence are enhanced for the ZnO quantum well when compared with those of InGaN-AlGaN quantum well structure due to the significant reduction of the piezoelectric effects in the ZnO-MgZnO systems.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.560-565
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• 2001

Recently, machining process monitoring technique based on AE(acoustic emission) signal is used widely and becomes very important technique in machining process for improving the efficiency and the confidence of the systems. In this study, we fabricated a cheap acoustic emission sensor and monitoring system and estimated the properties of them through comparing with commercial AE sensor systems. In addition, we evaluated the performance of the fabricated sensor in polishing process. Futhermore, we are scheduled to develop the multi-point polishing process monitoring system through fabrication of the more AE sensors and complement of the monitoring system.

• Journal of Magnetics
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• v.20 no.3
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• pp.252-257
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• 2015

This paper investigates the concept and implementation of an energy harvesting device using a ferrofluid sloshing movement to generate an electromotive force (EMF). Ferrofluids are often applied to energy harvesting devices because they have both magnetic properties and fluidity, and they behave similarly to a soft ferromagnetic substance. In addition, a ferrofluid can change its shape freely and generate an EMF from small vibrations. The existing energy harvesting techniques, for example those using piezoelectric and thermoelectric devices, generate minimal electric power, as low as a few micro-watts. Through flow analysis of ferrofluids and examination of the magnetic circuit characteristics of the resultant electromagnetic system, an energy harvester model based on an electromagnetic field generated by a ferrofluid is developed and proposed. The feasibility of the proposed scheme is demonstrated and its EMF characteristics are discussed based on experimental data.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2009.03a
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• pp.118-119
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• 2009

As the rapid development of the electronics, the demand for portable electronics and wireless sensors is growing faster, also with the increased needs of one material which can power it automatically, and then power the electrical devices. The piezoelectric effect of the PVDF material can be used for this. So in this paper, PVDF multilayer films were made for this aim. Make the PVDF / DMAc solution in the 10% concentration; use the spin coater technique to make films with the optimum process parameters: the spin rate is 1260rpm; the spin time is 70s; the dry temperature is 100$^{\circ}C$; the dry time is 30mins. And also, for obtaining the higher $\beta$-phase crystallinity, put the Ca(NH3)2.4H2O into the PVDF / DMAc solution system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.687-694
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• 1997

The anisotropy and shape of distributed piezopolymer actuator have advantages over isotropic piezo ceramic materials, since these features of PVDF can be utilized as another design variable in control application. This study is interested in the reduction of sound transmission through elastic plate into interior space by using the PVDF actuator. The plate-cavity system is adopted as a test problem. The vibration of composite plate and the sound fields through plate are analyzed by using the coupled finite element and boundary element method. Some numerical simulations are performed on sound transmission through elastic plates. To investigate the effects of anisotropy and shape of distributed piezopolymer actuator, various kinds of distributed PVDF actuators are applied in sound control simulation for isotropic and anisotropic plates. The PVDF actuators applied are different from each other in their shapes and laminate angles. The results of control simulation show that the control effectiveness of distributed PYDF actuator can be enhanced by using the coupling between shape of actuator and vibration modes of structure and the anisotropy of piezoelectric properties of PVDF.

• Analytical Science and Technology
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• v.6 no.2
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• pp.231-238
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• 1993

The thermal behavior of binder in multi-layer actuator has an effect on the properties of actuator. Binder burn-out process and thermal degradation mechanism of PNN-PZT/Acrylic binder were analyzed by FTIR, DSC, TGA. Binder was burnt out by two step. In oxygen atomsphere, thermal degradation was activated and final residue was minimized to 5%.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.2
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• pp.103-106
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• 2000

ZnO is a wide-bandgap II-IV semiconductor and has a variety of potnetial applications. ZnO exhibits good piezoelectric, photoelectric and optical properties, and is a good candidate for an electroluminescence device. ZnO films have been deposited on (001) sapphire by PLD technique. Nd:YAG pulsed laser was operated at a wavelength of $\lambda=355nm$. The ZnO films were deposited at oxygen pressures from base to 500 mTorr. The substrate temperatures was increased from $200^{\circ}C\; to\;700^{\circ}C$ films showed strong UV emission by increasing the partial oxygen pressure. We have investigated the relationship between partial oxygen pressure and the intensity of UV emission.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.40-43
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• 1996

Substrates of SAW filter are mainly single crystal such as LiNbO$_3$, LiTaO$_3$. However, fabrication of crystal is difficult and cost is very high. In this study, crystal was substituted for piezoelectric ceramics which has simple fabrication process. The same SAW filter mask was photolithographed on crystal(LiNbO$_3$) substrate and ceramic(PZT4, PZT5A and PZT8) substrate in order to compare experimental value with theoretical value. The difference of center frequency was only 3.7%. PZT8 showed good bandwidth properties. It is considered that PZT8 has higher mechanical quality factor and propagation velocity than PZT4, PTT5A.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1427-1429
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• 1997

In this study, piezoelectric transducer were designed and manufactured using PZT-5A which have relatively high electromechanical coefficient. A epoxy is a good material as matching and backing layers. The envelope was reduced 60% as using matching layer and 76% as using matching and backing layer. NDT was successfully carried out for aluminum test pieces. Distance error and resolution of PZT-5A probe were improved as increasing frequency. Envelope was effectively reduced by backing layer but sensitiveness was poor.