• 한국세라믹학회지
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• 제30권5호
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• pp.347-356
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• 1993

In joining alumina ceramics to metal by using Mo-Mn metallizing process the effects of metallizing thickness, temperature, and the composition of paste on the bond strength and the microstructure of joining interface were investigated. The bond strength variation in the range of metallizing temperature, 1350~155$0^{\circ}C$ was more than 150MPa above 145$0^{\circ}C$ and the optimum metallizing thickness was 30${\mu}{\textrm}{m}$. The optimum contents of Mn in Mo-Mn paste was 5% due to the bond strength decrease with the increase of addition. The effect of SiO2 addition in paste on bond strength was saturated around 200MPa. It was also observed that as the particle size of Mo decreased, the joinning with higher bond strength was shown in spite of low metallizing temperature.

• 한국세라믹학회지
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• 제32권6호
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• pp.653-658
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• 1995

Directional effect of applied pressure during sintering on the microstructure and fracture toughness of the heat-treated silicon nitride ceramics has been investigated. The specimens with a composition of 92Si3N4-8Y2O3(in wt%) were sintered at 172$0^{\circ}C$ by a hot press (HP ) and a hot isostatic press (HIP) and heat-treated for grain growth at 1800~20$0^{\circ}C$. The fracture toughness of the HP samples increased with the grain size while the fracture toughness of the HIP treated samples remained the same even though the grain growth occurred. This discrepancy was explained by a bimodal grain size distribution and large aspect ratio of the HPed samples and a monomodal grain size distributjion and samll aspect ratio of the HIP treated samples.

• 제어로봇시스템학회논문지
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• 제14권4호
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• pp.361-364
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• 2008

Tips of probe card were fabricated using MEMS technology. P-type silicon wafer with $SiO_2$ layer was used as a substrate for fabricating the probe card. Ni-Cr and Au used as seed layer for electroplating Ni were deposited on the silicon wafer. Line patterns for probing devices were formed on silicon wafer by electroplating Ni through mold which formed by MEMS technology. Bridge structure was formed by wet-etching the silicon substrate. AZ-1512 photoresist was used for protection layer of back side and DNB-H100PL-40 photoresist was used for patterning of the front side. The mold with the thickness of $60{\mu}m$ was also formed using THB-120N photoresist and probe tip with thickness of $50{\mu}m$ was fabricated by electroplating process.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1998년도 제28회 추계학술대회
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• pp.38-48
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• 1998

To apply the high chromium white cast irons for sliding parts of construction equipments, the wear characteristics of these alloys which have three kinds of microstructure(hypoeutectic, near-eutectic, hypereutectic) were investigated by dry sand/rubber wheel tester. Also, the effect of heat treatment was investigated for the same alloys. As result of the test, heat treatment have no effect on the wear characteristics. And, hypereutectic composition alloy has the highest wear resistance against SiO$_2$. Also after test, cracking was observed in eutectic and primary carbides of all materials tested. This phenomenon was important factor in the wear resistance.

• The Korean Journal of Ceramics
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• 제4권4호
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• pp.363-367
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• 1998

Alumina/mica and spinel/mica composites were fabricated by sintering of compacts containing 20 mass% fluoromica ($KMg_3AlSi_3O-{10}F_2$) glass and alumina or spinel. In both composites, mica precipitated as plate-like crystals at temperatures lower than $1300^{\circ}C$ and melted at $1300^{\circ}C$ to $1400^{\circ}C$. In alumina/mica composites, alumina and glass reacted to produce spinel, and the densification progressed by the solution-precipitation of alumina. Consequently, the glass composition changed and the mica did not precipitate at temperatures higher than $1400^{\circ}C$. However, mica precipitated after a reheating process. In spinel/mica composites, the glass composition did not change. After the mica phase melted, it recrystallized during slow cooling. The relative density reached the maximum at $1500^{\circ}C$ for alumina/mica and at $1300^{\circ}C$ spinel/mica composites, and decreased at further high temperatures.

• 보존과학회지
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• 제30권4호
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• pp.335-343
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• 2014

현재까지 분석된 백제지역 출토 철기 유물의 금속미세조직과 비금속개재물 분석 자료들을 한강, 금강, 영산강 유역권으로 분류하여 조업 온도를 추정하고 제강 및 열처리 기술을 지역적 시대별 특성을 조사하였다. 세 지역 모두 시대에 관계없이 고체저온환원으로 괴련철이나 해면철이 주 제철 방법으로 판단된다. 비금속개재물의 산화물 삼원상태도로 재해석한 결과 로내 온도는 $1,100{\sim}1,300^{\circ}C$ 정도에서 조업하였던 것으로 추정된다. 철광석은 자철광석이 주원료이며, $TiO_2$가 높은 것들은 사철을 사용하였던 것으로 보인다. $CaO/SiO_2$의 비율이 0.4 이상인 유물들은 석회질의 융제를 인위적으로 넣었던 것으로 판단된다. 제강은 저탄소강을 단야로에서 숯으로 가열할 때 나오는 CO, $CO_2$ gas로 침탄시키는 고체 침탄강임을 알 수 있었다. 또한 의도적으로 필요 부분의 강도를 높이는 침탄작업과 담금질을 하였던 것으로 보아 3세기에는 백제지역의 철기제작자들은 열처리 기술을 인지하고 있었다.

• 대한환경공학회지
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• 제37권7호
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• pp.412-417
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• 2015

본 연구는 하수처리장에서 발생하는 하수슬러지 소각재와 Geobond를 이용한 응용 블록의 개발을 위하여 수행하였다. 실험은 무소성 공정으로 진행하였으며, Sewage Sludge Ash (SSA)를 Geobond(무기바인더)와 특수시멘트인 초조강 시멘트 마이크로 시멘트, 모래 등의 바인더를 혼합한 각각의 페이스트 시편을 성형 후 건조 및 양생과정을 거친 시편을 단기 압축강도를 측정한 후 28일 장기 양생한 결과 압축 강도가 64.6 MPa로 발현하였다. 이는 KS기준치 22.54 MPa ($229.7kg/cm^2$)을 훨씬 상회하는 고강도의 압축강도를 나타내었다. 하수슬러지 소각재(SSA) 첨가율은 각 바인더 별 약 10~40%까지 혼합 가능한 것으로 나타났다. 따라서 SSA를 무기바인더인 Geobond와 특수시멘트(HESPC, MC)의 대체 물질로의 사용이 가능함을 입증하였다.

• 대한환경공학회지
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• 제36권12호
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• pp.843-850
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• 2014

본 연구는 국내 하수처리장에서 발생하는 감량화/안정화된 소각재를 무기바인더로 재이용하기 위하여 수행하였다. 실험은 무소성 공정으로 진행하였으며, Sewage Sludge Ash를 시멘트, Geobond 등의 바인더와 모래를 혼합하여 페이스트 시편과 몰탈 시편으로 성형하였다. 성형 후 양생과정을 거친 시편을 압축강도를 측정한 결과 KS 기준치 22.54 Mpa ($229.7kg/cm^2$)을 상회하고, 하수슬러지 소각재(SSA) 첨가율은 약 10~40%까지 가능한 것으로 나타나 개발하고자 한 하수슬러지 소각재를 무기바인더인 시멘트, Geobond의 대체 물질로 재활용이 가능함을 입증하였다.

• 대한금속재료학회지
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• 제48권4호
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• pp.347-352
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• 2010

This study reports a novel method off abricating highly sensitive hydrogen gas sensors based on PdO thin films. The PdO thin films with a thickness of 40 nm were deposited on Si substrates under Ar and $O_2$ ambient conditions using a reactive de magnetron sputtering system. Considerable changes in the resistance of the palladium oxide thin films were observed when they were initially exposed to hydrogen gas, as a result of the reduction process. The sensitivity of the PdO thin films was found to be as high as 90%. After the thin films were exposed to hydrogen gas, the nano-sized cracks were discovered to have formed on the surface of the PdO thin films. These types of nano-cracks that formed on the deoxidized PdO thin films are known to play a key role incausing a four-fold reduction of the response time of the absorption process. The results of this study demonstrate that deoxidized PdO thin films can be applied for use in the creation of high-sensitivity hydrogen sensors.

• 한국결정학회:학술대회논문집
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• 한국결정학회 2002년도 정기총회 및 추계학술연구발표회
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• pp.19-19
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• 2002

Perovskite-type titanate dielectrics have attracted much attention in memory devices such as DRAMs or FeRAMs due to their high dielectric constants. However, low volatility of the Ba, Sr, Pb or Zr precursors with only thd ligands has limitations in obtaining high quality thin films by liquid source metal organic chemical vapor deposition (LS-MOCVD) processes. To improve the volatility of these precursors, many attempts have been made such as adding polyether ligands to satisfy the coordinative saturation. We report the synthesis of new precursors Ba(thd)₂(tmeea) and Sr(thd)₂(tmeea), where tmeea = tris[2-(2-methoxyethoxy)ethyl]amino, and LS-MOCVD of barium strontium titanate (BSTO) thin films using these precursors. Due to increased basicity of amines compared with ethers, it is expected that the nitrogen-donor ligand will make a strong bond to a metal than an analogous oxygen-donor ligand, consequently improving the volatility and thermal behavior of these precursors. Thin films of BSTO were grown on Pt(111)/SiO₂/Si(100) substrates by LS-MOCVD using a cocktail source consisting of the conventional Ti precursor Ti(thd)₂(O/sup i/Pr), and these new Ba and Sr precursors. As-grown films were characterized by XPS, SEM, XRD, XRF, and C-V and I-V measurements. BSTO films grown at 420℃ were stoichiometric barium strontium titanate with very smooth surface morphology and their dielectric constants were found to be as targe as 450. Dependence of the composition, microstructure and the electrical properties of the BSTO films on the growth temperature, annealing temperature, working pressure, and the composition of the cocktail source will be discussed.