• 전기학회논문지
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• 제56권8호
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• pp.1455-1460
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• 2007

This paper reports the piezoelectric microspeakers that are audible in open air with high quality piezoelectric AlN thin film deposited onto Mo/Ti electrode. This successful achievement, compared to the previous results, is followed by manipulating two material properties: the one is to use a compressively stressed silicon nitride film as a supporting diaphragm (even tensile stressed, around +20 MPa) and the another is to use high quality AlN thin film with compressive residual stress (less than -100 MPa). With these materials, the Sound Pressure Level (SPL) of the fabricated micro speakers shows more than 60 dB from 100 Hz to 15 kHz and the highest SPL is about 100 dB at 9.3 kHz with 20 Vpeak-to-peak sinusoidal input and with 10 mm distances from the fabricated micro speakers to the reference microphone (B&K Type 2669 & 4192L).

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.942-945
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• 2001

Pulse electrochemical micromachining offers significant improvements in dimensional accuracy as compared with conventional electrochemical machining. One primary issue in pulse electrochemical micromachining is to identify and control machining depth as well as interelectrode gap size. This paper presents an identification method for the machining depth by in-process analysis of machining current and interelectrode gap size. The inter electrode gap characteristics, including pulse current, effective volumetric electrochemical equivalent and electrolyte conductivity variations, are analysed based on the model and experiments.

• 전기학회논문지
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• 제57권7호
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• pp.1218-1222
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• 2008

We investigate the effect of rise time of a pulse bias voltage on atmospheric plasma generation. With the faster rise time of the pulse bias, the glow discharge appears to be more uniformly generated along the electrodes. I-V measurement confirms that higher loading power can be obtained using the faster rise time. A new understanding for atmospheric plasma generation at a micro-gap electrode is suggested.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1539_1540
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• 2009

본 논문에서는 Porous Au-Pt 전극을 기반으로 연료전극과 공기전극으로 구성된 초소형 메탄올 센서를 설계 및 제작하고 그 특성을 분석해 보았다. 제안된 Porous Au-Pt 전극은 Porous 구조의 금속을 만드는 방법 중 하나인 Templating기법을 적용하여 수백나노 크기의 Pore들을 가진 Porous Au 전극을 제작하였고 그 위에 수 나노 크기의 Pt particles을 전해 도금하여 제작되었다. 고분자 전해질막 층으로서 Nafion film은 전해 도금한 Porous Au-Pt 전극 사이에 삽입하고 hot Pressing 통하여 센서를 구성하였다. Porous Au-Pt 전극을 기반으로한 전기화학 메탄올 센서는 $0.25\;cm^2$ 의 작은 전극 면적에도 불구하고 넓은 온도 범위 ($20^{\circ}C-100^{\circ}C$) 에서 온도에 따른 뛰어난 선형성(Correlation coefficient = 0.986)을 보였으며, 특히, 일정온도 ($60^{\circ}C$)에서 메탄올 농도 0 M에서 2 M 까지의 전류응답 특성을 측정, 분석 결과 메탄올 농도에 따른 9.6 mA/$mM{\cdot}cm^2$ 의 민감도 및 10 초 이내의 응답시간 특성을 보였다.

• 한국재료학회지
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• 제17권6호
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• pp.313-317
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• 2007

In-situ micro-channeled multi tubular solid oxide fuel cell(SOFC) was fabricated using multi-pass extrusion process with out side diameter of 2.7 mm and active length of 5 mm that contained 61 individual cells. Cell materials used in this work were NiO-YSZ (50 : 50 vol.%), 8 mol% yttria-stabilized zirconia(8YSZ), $La_{0.8}Sr_{0.2}MnO_3(LSM)$ as anode, electrolyte, and cathode, respectively. The arrangement of each electrode and electrolyte layer in green bodies showed uniformity and integrity after extrusion and sintering. The XRD analysis confirmed that no reaction phases appeared and the microstructure of the electrolyte was fairly dense (relative density > 96%) after sintering.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.99-99
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• 2010

Polymer nanocomposite has been attracting much attention as a new insulation material, since homogeneous dispersion of nm-sized inorganic fillers can improve various properties significantly. In this paper, various kinds of epoxy based nanocomposites were made and AC breakdown strength of Nano-TiO2 and micro-silica filler mixture of epoxy based composites were studied by sphere to sphere electrode. Moreover, nano- and micro-filler combinations were adopted as an approach toward practical application of nanocomposite insulation materials. Nano-TiO2 particle size is about 10nm and composites ratio was resin (100) : hardener (82) : accelerator (1.5). AC breakdown test was performed at room temperature (25 [$^{\circ}C$], 80 [$^{\circ}C$] and 100 [$^{\circ}C$] in the vicinity of Tg (90[$^{\circ}C$]). And thermal conductivity were measured by ASTM-D5470.

• 한국정밀공학회지
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• 제19권4호
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• pp.161-167
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• 2002

For the purpose of applying to micro-actuator, thermal properties and displacement of electrostrictive polyurethane(PU) elastomers have been measured. In order to understand an effect of PU component, crosslinking agent are controlled by 0.5 wt% and 1 wt%. DMPA and anther chain extenders were used. PU sample that chain extenders are DMPA is added NaOH for comprehension of effect of ionic groups. The deposited electrode sire on PU films is equal to acrylic holder size when the displacement was measured. Dynamic response according to frequency, displacement and recovery time according to PU thickness were measured. 1 wt% crosslinking agent contents PU samples have higher displacement and lower recovery time than 0.5 wt% crosslinking agent contents PU. If the PU thickness is increased, the actuating voltage for generating of same displacement is increased, too.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.467-468
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• 2006

In this work, we present the comparison between $d_{31}\;and\;d_{33}$ mode characterization using the PZT micro-actuator for large displacement. The PZT micro-actuator consisted of Si, PZT, and Pt layer on SOI wafer. The electrode shapes were laminated and interdigitated for $d_{31}\;and\;d_{33}$ mode, respectively. In order to characterize the actuation mode, we measured the displacement using laser interferometer. The maximum displacement of d31 mode was $12.2{\mu}m$ at 10V, the actuation characterization of d31 was better than that of d33 mode. We estimated that displacement of d33 mode would be larger than that of d31 above 30V.

• 한국생산제조학회지
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• 제20권2호
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• pp.180-186
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• 2011

This paper describes a micro electrical discharge machining (MEDM) technique that uses an insulated tool in combination with ultrasonic vibration to drill micro holes. As the machining depth becomes deeper, the dispersion of debris and circulation of the dielectric fluid are difficult to occur. Consequently, machining becomes unstable in the machining region and unnecessary electrochemical dissolution and secondary discharge sparking occur at the tool side face. To reduce the amount of unnecessary side machining, an insulated tool was used. Ultrasonic vibration was applied to the MEDM work fluid to better remove debris. Through these methods, a $1000\;{\mu}m$ thick stainless steel plate was machined by using a $73\;{\mu}m$ diameter electrode. The diameters of the hole entrance and exit were $96\;{\mu}m$ and $88\;{\mu}m$, respectively. It took only 351s to completely drill one hole.

• 한국생산제조학회지
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• 제19권3호
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• pp.370-375
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• 2010

본 연구에서는 전해가공을 이용해서 직경이 균일한 텅스텐 카바이드 미세축을 제작하는 실험을 수행하였다. 전해가공을 통해 미세축으로 사용 가능한 형상을 얻기 위한 최적의 가공 조건에 대해 고찰하였다 이 과정에서 미세축의 형상에 영향을 주는 여러 인자들을 적절하게 조절하여 최적의 형상을 얻을 수 있었다. 그리고 가공된 미세축을 이용하여 적절한 조건으로 2차, 3차 가공을 수행하여 초미세축을 가공할 수 있음을 보였다. 그리하여 실험 결과 직경 $30{\mu}m$, 길이 $500{\mu}m$의 텅스텐 카바이드 미세축을 제작하였다.