• The Korean Journal of Ceramics
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• 제1권3호
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• pp.137-142
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• 1995

Monodispersed $Al_2O_3-TiO_2$ Powder was prepared by metal-alkoxide hydrolsis. A homogeneous nucleation/growth occurred in the solutions containing ethanol, butanol and acetonitrile, and resulted in spherical, submicrometer-sized powder. The titania and the alumina crystals were formed at $800^{\circ}C$ and $1000^{\circ}C$, respectively. These crystala were subsequently reacted each other beyond $1320^{\circ}C$ and formed $Al_2TiO_5$. The relative densities of sintered bodies prepared with as-received powder were examined at the temperature range of 1300-$1500^{\circ}C$ and they were about 79% at $1300^{\circ}C$. The formation of aluminum titanata decreased the relative density at the temperature range of 1300-$1450^{\circ}C$, and at above $1450^{\circ}C$, the relative density started to increase again. It was observed that $\alpha-Al_2O_3$-doped aluminum titanate was more stable than pure aluminum titante at $1200^{\circ}C$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 춘계학술대회 논문집
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• pp.13-13
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• 2010

Piezoelectric sensors are extensively used to measure force because of their high sensitivity and low cost. however, the development of device with reduced size but with improved sensitivity is highly important. Low-temperature co-fired ceramic (LTCC) is one of promising materials for this application than a silicon substrate because it has very good electrical and mechanical properties as well as possibility of making various three dimensional (3D) structures. In this work, piezoelectric pressure sensors based on hybrid LTCC technology were presented. The LTCC diaphragms with thickness of $400\;{\mu}m$ were fabricated by laminating 12 green tapes which consist of alumina and glass particle in an organic binder. The piezoelectric sensing layer consists of PZT thin film deposited by RF magnetron sputtering method on between top and bottom Au electrodes. The PZT films deposited on LTCC diaphragms were successfully grown and were analyzed by using X-ray diffraction method (XRD) and field emission scanning electron microscope (FESEM).

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.204-204
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• 2010

A development of device with reduced size and improved sensitivity is highly impotant Pb(Zr,Ti)$O_3$ thin films are widely used both to make actuator and sensor due to their high sensitivity and low cost. In this study, the feasibility of a piezoelectric presssure sensors based on hybrid low-temperaute co-fired ceramic (LTCC) technology were presented. The LTCC diaphragms with thickness of $400\;{\mu}m$ were fabricated by laminating 4 green tapes which consist of alumina and glass particle in an organic binder. PZT thin films were successfully prepared on between top and bottom Au electrode with LTCC substrates using RF magnetron sputtering. In addition, The frequency response characteristics of the sensor under varing pressure has been analysed. by Network Analyser (HP-8722D). A frequency shift range has been obseved from 1.7GHz to 1.8GHz with a good linearity for applied pressure from 0 psi up to 25 psi.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.205-205
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• 2010

Recently, low temperature co-fired ceramic (LTCC) technology is widely used in sensors, actuators and microsystem fields because of its very good electrical and mechanical properties, high stability as well as possibility of making 3D micro structures. In this study, we investigated the effects of on $O_2$ annealing treatment on the electrical properties of Pb(ZrTi)$O_3$ (PZT) thin films deposited on LTCC substrate. The LTCC substrates with thickness of $400\;{\mu}m$ were fabricated by laminating 4 green tapes which consist of alumina and glass particle in an organic binder. The PZT thin films were deposited on Au / LTCC substrates by RF magnetron sputtering method. The change of the crystallization of the films were investigated under various atmosphere. The structural variation of the films were analyzed by using X-Ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) and secondary ion mass spectrometry (SIMS).

• 한국해양공학회지
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• 제23권5호
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• pp.32-38
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• 2009

Silicon nitride samples with aligned whisker seeds were prepared with different amounts of yttria and alumina as the sintering additives. Their sintering behaviors and the microstructural developments between $1850^{\circ}C$ and $2050^{\circ}C$ were examined. The sample with larger amount of the sintering additives showed faster densification and grain growth. Even though addition of the aligned whisker seeds slightly retarded densification of silicon nitride, it improved the flexural strength and the fracture toughness. Both the flexural strength and the fracture toughness of silicon nitride with the aligned whisker seeds were increased as the amount of the sintering additives was increased.

• 대한기계학회논문집A
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• 제27권12호
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• pp.2085-2091
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• 2003

An ultrasonic machining process has been known as efficient and economical means fer precision machining of glass or ceramic materials. However, because of its complexity, the mechanism of the machining process is still not well understood. Therefore, it is hard to optimize the process parameters effectively. The conventional ultrasonic machining which uses the abrasive slurry only, furthermore, is time-consuming and gives the relatively rough surface. In order to increase the material removal rate and improve the integrity of the machined surface, we have introduced the novel ultrasonic machining technique, Chemical-assisted UltraSonic Machining(CUSM). The desktop-style micro ultrasonic machine has been developed and the z-axis feed is controlled by the constant load control algorithm. To obtain the chemical effects, the low concentration HF(hydrofluoric acid) solution, which erodes glass, added to alumina slurry. Through various experiments and comparison with conventional results, the superiority of CUSM is verified. MRR increases over 200%, the surface roughness is improved and the machining load decreases dramatically.

• 마이크로전자및패키징학회지
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• 제5권1호
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• pp.19-30
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• 1998

Aluminium secondary butoxide(ASB)를 출발물질로 하여 졸-겔방법에 의해 소결거 동에 미치는 $\alpha$-Al2O3 seed의 첨가효과에 따른 알루미나의 저온소결 가능성과 알루미나의 상전이에 대하여 TEM, DTA, XRD, FT-IR등으로 고찰을 하였다. TEM 분석결과 초기 생 성물인 boehmite가 비정질에서 단결정질로 진행되어 가고 있음을 확인하였다. 그리고 DTA 분석결과 $\alpha$-Al2O3 seed의 첨가한 경우 seed의 함량이 증가함에 따라 상전이 온도는 점차 낮아졌으며 약 0.4wt%일 때 seed를 첨가하지 않은 시료의 전이온도(약 1126$^{\circ}C$)에 비하여 약 7$0^{\circ}C$ 저하된 약 1056$^{\circ}C$로나타났으며 그 이상의 seedcja가에 있어서는 전이온도에 크게 영향을 나타내지 않았다. 또한 XRD분석결과 $\alpha$-Al2O3 seed를 첨가하지 않은 경우 110$0^{\circ}C$이 상의 온도에서 $\alpha$상이 생성되었음을 알수 있었다. 또한 100$0^{\circ}C$이상의 온도에서 $\alpha$상이 생성 되었음을 나타내는 Al-O 흡수특성 피크가 400~1000cm-1 범위에서 나타내고 있는 것을 FT-IR 분석결과에서도 확인할수 있었다. 그리고 $\alpha$-Al2O3 seed를 약 0.4wt% 첨가시 900~ 95$0^{\circ}C$에서 $\alpha$상이 형성됨을 관찰할 수 있었다.

• 센서학회지
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• 제25권3호
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• pp.229-234
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• 2016

Self-powered neutron detector (SPND) is being widely used to monitor the reactor core of the nuclear power plants. The SPND contains a neutron-sensitive metallic emitter surrounded by a ceramic insulator. Currently, the vanadium (V) SPND has been being developed to be used in OPR1000 nuclear power plants. Some Monte Carlo simulations were accomplished to calculate the initial sensitivity of vanadium emitter material and alumina insulator with a cylindrical geometry. An MCNP code was used to simulate some factors (neutron self-shielding factor and beta escape probability from the emitter) and space charge effect of an insulator necessary to calculate the sensitivity of vanadium detector. The simulation results were compared with some theoretical and experimental values. The method presented here can be used to analyze the optimum design of the vanadium SPND and contribute to the development of TMI (Top-mount In-core Instrumentation) which might be used in the SMART and SMR.

• 센서학회지
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• 제19권2호
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• pp.149-154
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• 2010

Top of the alumina body which is made according to plan has been printed using a screen printer equipment in order to print an electrode pattern. The electrode is connected with the quartz crystal oscillator of the piezoelectricity method which has a piezoelectric characteristic. The pressure contact department has been experimented using three type of the teflon. The teflon is good for pressure delivery vector but it is bad restitution. So we devised the structure which inserts the metal in the teflon. Bottom of the module is connected with the signal processing department which is planned in advance and then has investigated to characteristic. Therefore we have got the best output-voltage and frequency characteristic follows in the pressure.

• 한국수소및신에너지학회논문집
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• 제24권6호
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• pp.467-471
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• 2013

In present work, optimized the manufacturing process of anode-supported tubular SOFCs cell and stack were studied. For this purpose, we first developed a high performance tubular SOFC cell, and then made electrical connection in series to get high voltage. The gas sealing was established by attaching single cells to alumina jig with ceramic bond. Through these process, we can obtain such high OVP as around 15V, which means that the electrical connection and gas sealing were optimized. Finally we developed a new tubular SOFC stack which shows a maximum power of 65W @ $800^{\circ}C$.