• 한국화재소방학회논문지
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• 제18권4호
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• pp.57-63
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• 2004

본 연구에서는 저압용 누전차단기 접속단자에서의 접촉압력에 따른 발열특성을 조사하고 차단기 단자와 전선에 접촉 불량이 발생했을 때의 전압, 전류파형과 산화물 증식 등을 분석하였다. 차단기 단자와 전선에 접촉압력이 가해지지 않았을 때는 접촉저항증가로 열이 발생하고 금속표면에 산화 막이 형성되었다. 이때 단자 외부 절연물의 온도는 접촉 불량에 의해 급격하게 상승하며 단자내부에서 미세한 불꽃과 연속적인 방전음이 발생하였다. 단자내부도체와 접속전선 접촉면에서 기계적 진동에 의한 접촉 불량이 발생했을 때, 접촉면에서 산화물이 증식되고 발열온도는 869℃이상으로 상승하여 전기재해의 위험이 높음을 알 수 있었다.

• 한국세라믹학회지
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• 제33권5호
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• pp.572-582
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• 1996

전류밀도, 70mA/cm2와 전류인가시간, 5초, 10초 조건의 양극반응으로 다공성 실리콘을 제작하여 800~110$0^{\circ}C$에서 열산화시킨 후 AI 전극을 증착시켜 만든 MOS(Metal Oxide Semiconductor) 구조의 C-V(Capacilance-Voltage) 특성을 조사하였다. 800, 90$0^{\circ}C$의 저온과 20~30분 이내의 단시간 산화에서는 산화막의 유전상수가 보통의 열산화막보다 크게 나타나고, 산화온도가 110$0^{\circ}C$의 고온과 60분 이상의 장시간 산화의 경우에는 3.9에 근접한 값을 갖는다. 이는 다공성 실리콘 산화막내에 존재하는 산화되지 않은 silicon들에 의한 효과와 표면적 증가에 의한 정전용량의 증가 효과가 복합적으로 작용하는 것이 그 원인이라 생각된다.

• 한국재료학회지
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• 제9권8호
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• pp.854-857
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• 1999

Fe-Se-Te계(FeSe(sub)1-xTe(sub)x, x=0.2, 0.5, 0.8)의 특성을 X-선 회절법 및 Mossbauer 분광법에 의해 조사하였다. 결정구조는 세 시료 모두 주된 tetragonal PbO 구조와 hexagonal NiAs 구조가 일부 혼합된 형태를 보였으며 x=0.5의 경우 tetragonal 구조의 격자상수 값은 a=3.795$\AA$, c=5.896$\AA$ 이며 c/a=1.55로 나타났다. 다양한 온도변화에 의해 측정된 Mossbauer 스펙트럼은 전체 시료 모두 초미세 자기구조를 갖지 않는 강한 이중선(doublet)이 관측되었다. 조성 및 온도변화에 대해 뚜렷한 선형(line shape)의 변화는 관측되지 않았으나 결합상태에 약간의 변화를 보였다. 이성질체 이동(isomer shift)값과 사중극자 분열(quadrupole splitting)값 및 온도의존성을 분석한 결과 Fe는 low spin이 +2가 상태로 존재하며 강한 공유 결합상태임을 알 수 있었다. x=0.8의 경우 이성질체 이동값의 온도변화는 제2차 도플러 효과(second order Doppler effect)의 영향인 것으로 나타났다.

• 한국자기학회지
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• 제8권5호
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• pp.282-287
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• 1998

유리 기판위에 dc magnetron sputtering 방법으로 제작한Fe(50 $\AA$)/[Co(17 $\AA$)/Cu(24 $\AA$)]20 다층박막에 관하여 자기저항비의 기저층, 자성층, 비자성층의 증착률 및 열처리 의존성을 살펴보았다. 낮은 base 압력 중에서의 막의 증착은 Co/Cu 계면의 산화를 억제하여 자기저항비를 장가시켰다. 극대 자기저항비를 얻기위해 요구되는 증착률은 Fe는 1$\AA$)/s 이상, Cu는 2.8 $\AA$)/s 이었으며 Co는 증착률이 2 $\AA$/s 보다 높은 경우에 평탄한 자구형성을 이루어 자기적 향비가 높아지는 경향을 보였다. 40$0^{\circ}C$까지의 시료에 대한 역처리는 다층박막의 주기성을 유지한채 더 큰 결정립을 형성시켜 반강자성적으로 결합한 막의 부분이 증가함으로써 자기저항비를 증가시켰다.

• Journal of Electrochemical Science and Technology
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• 제13권3호
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• pp.390-397
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• 2022

The use of microwaves as the energy source for synthesis and sintering of ceramics offers substantial advantages compared to conventional gas-fired and electric resistance furnaces. Benefits include much shorter processing times and reaching the sintering temperature more quickly, resulting in superior final product quality. Most oxide ceramics poorly interact with microwave irradiation at low temperatures; thus, a more complex setup including a susceptor is needed, which makes the whole process very complicated. This investigation pursued a new approach, which enabled us to use microwave irradiation directly in poorly coupled oxides. In many solid-state electrochemical devices, the support is either metal or can be reduced to metal. Metal powders in the support can act as an internal susceptor and heat the entire cell. Then sufficient interaction of microwave irradiation and ceramic material can occur as the sample temperature increases. This microwave heating and exothermic reaction of oxidation of the support can sinter the ceramic very efficiently without any external susceptor. In this study, yttria stabilized zirconia (YSZ) and a Ni-YSZ cermet support were used as an example. The cermet was used as the support, and a YSZ electrolyte was coated and sintered directly using microwave irradiation without the use of any susceptor. The results were compared to a similar cell prepared using a conventional electric furnace. The leakage test and full cell power measurement results revealed a fully leak-free electrolyte. Scanning electron microscopy and density measurements show that microwave sintered samples have lower open porosity in the electrode support than conventional heat treatment. This technique offers an efficient way to directly use microwave irradiation to sinter thin film ceramics without a susceptor.

• 공업화학
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• 제19권2호
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• pp.157-160
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• 2008

탄화수소 계열의 연료로부터 고순도의 수소를 생산하는 것은 연료전지의 효율적인 운전과 밀접하다. 일반적으로 대부분의 탄화수소 연료에서 수소를 생산하는 과정은 수소, 일산화탄소, 이산화탄소와 수증기 혼합물이 생성되는 개질 과정 및 일산화탄소를 저감하는 전이반응과 선택적 산화반응 과정으로 구성되어 있다. 전이반응은 일산화탄소를 이산화탄소로 전환하는 동시에 수소가 생성되는 고온 전이와 저온전이로 구성된 두 단계의 촉매전환 공정이다. 일반적으로 개질기에서 생성된 개질 가스는 고온전이 반응기를 거쳐 일산화탄소 농도를 3~5%까지 저감한다. 본 연구에서는 고온전이 반응기를 설계 및 제작하여 일산화탄소 농도를 2~4%까지 저감하였다. 고온전이 반응에서 철이 첨가한 촉매(G-3C)를 사용하여 부분산화 개질에서 생성된 일산화탄소를 이산화탄소로 전환하였다. 그리고 고온전이 영향인자인 수증기 주입량, 개질 가스 조성, 반응온도, 개질 가스 주입량변화에 대한 연구를 진행하였다.

• 한국수산과학회지
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• 제18권5호
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• pp.409-416
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• 1985

In previous paper (Lee et al., 1983) processing method of sardine meat "surimi" was described as a part of the wort to develop new types of ready-to-cook food materials with dark fleshed fishes. As the other part of the work, processing of low salt mackerel fillet was investigated, in this paper, in which fresh mackerel was filleted, salted in brine or with dry salt for an adequate time until the expected salt concentration reached, washed, air dried (3 m/sec, 15 to $20^{\circ}C$), and finally packed individually in K-flex film bag by vacuum or $N_2$ gas substitution. Salting time and salt concentration of brine was decided by the salt level penetrated into the fillet. As the final salt level was fixed to 4 to $5\%$, salting for 20 hours with $10\%$ dry salt or in $15\%$ brine at $5^{\circ}C$ was enough to get that level of salt. If the final salt level was set 5 to $6\%$, salting for 20-24 hours with $15\%$ dry salt or in $20\%$ brine was adequate. Salt penetration, however, was not much influenced by salting method and temperature. Changes in VBN and salt soluble protein occurred more rapidly in cases of salting with dry salt at $20^{\circ}C$ than salted in brine at $5^{\circ}C$, although it was not significant in the period of 20 to 24 hours. Oxidation of lipid and histamine formation during salting at $20^{\circ}C$ could not be neglected if it was delayed loger than 25 hours. Insolubilizing the salt soluble proteins during the storage of salted fillet occurred rapidly regardless of storage temperature. Browning and histamine formation, however, was depended on temperature and packing condition. In case of air pack, deterioration by browning and rancid was deeply developed but not the case for the packs by vacuum or $N_2$ gas substitution. The shelf-life of the salted mackerel fillet based on panel scores of brown color and rancidity, appeared 21 days for the air packed, and more than 30 days for vacunm or $N_2$ gas packed fillet at $20^{\circ}C$.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 추계학술발표대회
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• pp.23.1-23.1
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• 2009

ZnO is of great interest for various technological applications ranging from optoelectronics to chemical sensors because of its superior emission, electronic, and chemical properties. In addition, vertically well-aligned ZnO nanorods on large areas with good optical and structural properties are of special interest for the fabrication of electronic and optical nanodevices. To date, several approaches have been proposed for the growth of one-dimensional (1D) ZnO nanostructunres. Several groups have been reported the MOCVD growth of ZnO nanorods with no metal catalysts at $400^{\circ}C$, and fabricated a well-aligned ZnO nanorod array on a PLD prepared ZnO film by using a catalyst-free method. It has been suggested that the synthesis of ZnO nanowires using a template-less/surfactant-free aqueous method. However, despite being a well-established and cost-effective method of thin film deposition, the use of magnetrons puttering to grow ZnO nanorods has not been reported yet. Additionally,magnetron sputtering has the dvantage of producing highly oriented ZnO film sat a relatively low process temperature. Currently, more effort has been concentrated on the synthesis of 1D ZnO nanostructures doped with various metal elements (Al, In, Ga, etc.) to obtain nanostructures with high quality,improved emission properties, and high conductance in functional oxide semiconductors. Among these dopants, Ga-doped ZnO has demonstrated substantial advantages over Al-doped ZnO, including greater resistant to oxidation. Since the covalent bond length of Ga-O ($1.92\;{\AA}$) is nearly equal to that of Zn-O ($1.97\;{\AA}$), high electron mobility and low electrical resistivity are also expected in the Ga-doped ZnO. In this article, we report the successful growth of Ga-doped ZnO nanorods on c-Sapphire substrate without metal catalysts by magnetrons puttering and our investigations of their structural, optical, and field emission properties.

• 한국분말재료학회지
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• 제11권4호
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• pp.308-313
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• 2004

An experimental study on the combustion of superfine aluminum powders (average particle diameter, a$_{s}$: ∼0.1 ${\mu}{\textrm}{m}$) in air is reported. The formation of aluminum nitride during the combustion of aluminum in air and the influence of the combustion scenario on the structures and compositions of the final products are in the focus of this study. The experiments were conducted in an air (pressure: 1 atm). Superfine aluminum powders were produced by the wire electrical explosion method. Such superfine aluminum powder is stable in air but once ignited it can burn in a self-sustaining way due to its low bulk: density (∼0.1 g/㎤) and a low thermal conductivity. During combustion, the temperature and radiation were measured and the actual burning process was recorded by a video camera. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and chemical analysis were performed on the both initial powders and final products. It was found that the powders, ignited by local heating, burned in a two-stage self-propagating regime. The products of the first stage consisted of unreacted aluminum (-70 mass %) and amorphous oxides with traces of AlN. After the second stage the AlN content exceeded 50 mass % and the residual Al content decreased to ∼10 mass %. A qualitative discussion is given on the kinetic limitation for AlN oxidation due to rapid condensation and encapsulation of gaseous AlN.N.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.358-361
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• 2002

Self-aligned MOSFETS using a polysilicon gate are widely fabricated in silicon technology. The polysilicon layer acts as a mask for the source and drain implants and does as gate electrode in the final product. However, the usage of polysilicon gate as a self-aligned mask is restricted in fabricating SiC MOSFETS since the following processes such as dopant activation, ohmic contacts are done at the very high temperature to attack the stability of the polysilicon layer. A metal instead of polysilicon can be used as a gate material and even can be used for ohmic contact to source region of SiC MOSFETS, which may reduce the number of the fabrication processes. Co-formation process of metal-source/drain ohmic contact and gate has been examined in the 4H-SiC based vertical power MOSFET At low bias region (<20V), increment of leakage current after RTA was detected. However, the amount of leakage current increment was less than a few tens of ph. The interface trap densities calculated from high-low frequency C-V curves do not show any difference between w/ RTA and w/o RTA. From the C-V characteristic curves, equivalent oxide thickness was calculated. The calculated thickness was 55 and 62nm for w/o RTA and w/ RTA, respectively. During the annealing, oxidation and silicidation of Ni can be occurred. Even though refractory nature of Ni, 950$^{\circ}C$ is high enough to oxidize it. Ni reacts with silicon and oxygen from SiO$_2$ 1ayer and form Ni-silicide and Ni-oxide, respectively. These extra layers result in the change of capacitance of whole oxide layer and the leakage current