• 한국재료학회지
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• 제20권4호
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• pp.194-198
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• 2010

Cubic boron nitride (c-BN) is a promising material for use in many potential applications because of its outstanding physical properties such as high thermal stability, high abrasive wear resistance, and super hardness. Even though 316L austenitic stainless steel (STS) has poor wear resistance causing it to be toxic in the body due to wear and material chips, 316L STS has been used for implant biomaterials in orthopedics due to its good corrosion resistance and mechanical properties. Therefore, in the present study, c-BN films with a $B_4C$ layer were applied to a 316L STS specimen in order to improve its wear resistance. The deposition of the c-BN films was performed using an r.f. (13.56 MHz) magnetron sputtering system with a $B_4C$ target. The coating layers were characterized using XPS and SEM, and the mechanical properties were investigated using a nanoindenter. The friction coefficient of the c-BN coated 316L STS steel was obtained using a pin-on-disk according to the ASTM G163-99. The thickness of the obtained c-BN and $B_4C$ were about 220 nm and 630 nm, respectively. The high resolution XPS spectra analysis of B1s and N1s revealed that the c-BN film was mainly composed of $sp^3$ BN bonds. The hardness and elastic modulus of the c-BN measured by the nanoindenter were 46.8 GPa and 345.7 GPa, respectively. The friction coefficient of the c-BN coated 316L STS was decreased from 3.5 to 1.6. The wear property of the c-BN coated 316L STS was enhanced by a factor of two.

• 한국가스학회지
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• 제5권1호
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• pp.52-59
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• 2001

LP가스 용접 용기의 가스 누출사고에 대한 통계적 분석을 통하여 사고 발생에 영향을 미치는 주된 요인을 조사하였다. 그 결과 대부분의 가스 누출은 용접부 국부부식에 따른 핀홀에 의한 누출이 가장 큰 비중을 차지하고 있다. 따라서, 본 논문에서는 2부구조 용기에서의 열처리조건의 문제점과 3부구조 용기의 T부위 터짐 현상에 의한 대책안을 제시하였다. 나아가, LP 가스 용기의 용접부 및 모재부에 대하여 산성비와 해수 분위기에서의 부식속도를 전기화학적 부식실험을 통하여 측정하였다. 또한, LP가스 용기의 제조공정중 분체도장 공정에 의한 도장막의 부착성 및 결함을 주사전자현미경을 통하여 분석하고 최적의 도장 두께를 제시하였다.

• 한국안광학회지
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• 제3권1호
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• pp.217-222
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• 1998

$SiO_2-TiO_2-AgO$ 코팅박막을 졸-겔법으로 현미경용 슬라이드 유리판과 씰리콘 기판에 제조하였다. 이 박막의 열처리온도는 $500^{\circ}C$가 적절하였으며 5회 반복코팅한 박막의 두께는 310nm였다. AgO가 10mol% 첨가된 박막의 표면은 균일한 구조를 보였으나 첨가량이 많아질수록 박막의 표면에 pin hole과 AgO의 석출에 기인한 cluster를 보였다. 열처리온도의 증가에 따라 IR흡수의 정도가 점차 감소하였고, AgO 첨가량의 증가에 따라 반사율은 점차 감소하였으며 색상은 light yellow에서 무채색 쪽으로 점차 전이하였다.

• Progress in Superconductivity
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• 제9권1호
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• pp.102-106
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• 2007

YBCO films have been synthesized using a spray pyrolysis method. We used nitrates of Y, Ba, Cu as precursors. Deposition was made on $LaAlO_3$ (100) single crystal substrate by spraying the mist of aqueous precursor solution generated by a concentric nozzle. The distance between concentric nozzle and substrate was 15 cm. C-axis oriented films were obtained at deposition temperature of $740{\sim}800^{\circ}C$ and working pressure of 20 Torr. Oxygen partial pressure was 3 Torr and substrate was transported with the speed ranging from 0.23 cm/min to 0.7 cm/min by reel to reel. Scanning electron microscope (SEM) and X-ray diffraction (XRD) observation revealed that films are smooth and highly textured with (001) planes parallel to substrate. Highest critical current density (Jc) was $1.38\;MA/cm^2$ at 77K and self-field for the film with a thickness of $0.5\;{\mu}m$ prepared at a substrate temperature of $780^{\circ}C$ and $PO_2\;=3\;Torr$. The effect of temperature on the microstructure and YBCO phase formation will be discussed.

• 분석과학
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• 제7권3호
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• pp.371-378
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• 1994

이 갈바니식 산소센서의 산소농도 측정범위는 0.0~20.0%이었다. 산소환원 전극으로 금 또는 은을 이용하여 산소농도 변화에 따른 재현성 있는 응답시간 및 감도를 얻었다. 산화전극으로는 Pb-Sn-Ca 합금을 이용하였다. 산소 선택 투과막은 소수성이며 다공성 물질인 테플론을 이용하여 두께 변화에 따른 온도($10{\sim}50^{\circ}C$) 및 습도(R. H 0~99%)에 미치는 영향을 연구하였다. 전해질은 아세트산납 완충 용액을 이용하여 출력전압을 증가시켰으며, 센서의 수명을 길게 하였다.

• 한국결정성장학회지
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• 제8권2호
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• pp.249-254
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• 1998

GaN계 재료의 습식 화학식각 특성과 광 화학 및 전기 화학 및 전기 화학 습식식각 특성을 연구하였다. n형 GaN는 상온에서 NaOH 수용액에 식각되었으며 식각두께는 식각시간에 선형적으로 증가하였다. 또 광 조사 및 전기 화학을 가할 경우 식각율은 수배로 증가하였으며, 식각율은 $1{\times}10^{19};cm^{-3}$의 전자농도를 갖는 시료에서 광 조사시 최대 164${\AA}$/min을 얻었다. n-GaN의 식각율은 GaN의 전자농도에 크게 의존하는 특성을 나타내었으며 이러한 식각과정을 논의하였다. $SiO_2$ 박막으로 덮여진 100${\mu}m{\times}100{\mu}m$ 모양의 옆 식각면은 방향성을 갖지 않고 수직하였으며, 넓은 면적에서 매우 평탄하였다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2017년도 춘계학술대회 논문집
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• pp.149-149
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• 2017

Aluminum alloys have poor corrosion resistance compared to the pure aluminum due to the additive elements. Thus, anodizing technology artificially generating thick oxide films are widely applied nowadays in order to improve corrosion resistance. Anodizing is one of the surface modification techniques, which is commercially applicable to a large surface at a low price. However, most studies up to now have focused on its commercialization with hardly any research on the assessment and improvement of the physical characteristics of the anodized films. Therefore, this study aims to select the optimum temperature of sulfuric electrolyte to perform excellent corrosion resistance in the harsh marine environment through electrochemical experiment in the seawater upon generating porous films by variating the temperatures of sulfuric electrolyte. To fabricate uniform porous film of 5083 aluminum alloy, we conducted electro-polishing under the 25 V at $5^{\circ}C$ condition for three minutes using mixed solution of ethanol (95 %) and perchloric (70 %) acid with volume ratio of 4:1. Afterward, the first step surface modification was performed using sulfuric acid as an electrolyte where the electrolyte concentration was maintained at 10 vol.% by using a jacketed beaker. For anode, 5083 aluminum alloy with thickness of 5 mm and size of $2cm{\times}2cm$ was used, while platinum electrode was used for cathode. The distance between the two was maintained at 3 cm. Anodic polarization test was performed at scan rate of 2 mV/s up to +3.0 V vs open circuit potential in natural seawater. Surface morphology was compared using 3D analysis microscope to observe the damage behavior. As a result, the case of surface modification showed a significantly lower corrosion current density than that without modification, indicating excellent corrosion resistance.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.562-562
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• 2012

Recently, graphene and graphene-based materials such as graphene oxide (GO) or reduced graphene oxide (R-GO) draws a great attention for electronic devices due to their structures of one atomic layer of carbon hexagon that have excellent mechanical, electrical, thermal, optical properties and very high specific surface area that can be high potential for chemical functionalization. R-GO is a promising candidate because it can be prepared with low-cost from solution process by chemical oxidation and exfoliation using strong acids and oxidants to produce graphene oxide (GO) and its subsequent reduction. R-GO has been used as semiconductor or conductor materials as well as sensing layer for bio-molecules or ions. In this work, reduced graphene oxide field-effect transistor (R-GO FET) has been fabricated with ITO extended gate structure that has sensing area on ITO extended gate part. R-GO FET device was encapsulated by tetratetracontane (TTC) layer using thermal evaporation. A thermal annealing process was carried out at $140^{\circ}C$ for 4 hours in the same thermal vacuum chamber to remove defects in R-GO film before deposition of TTC at $50^{\circ}C$ with thickness of 200 nm. As a result of this process, R-GO FET device has a very high stability and durability for months to serve as a transducer for sensing applications.

• 한국재료학회지
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• 제13권9호
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• pp.613-618
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• 2003

The magnetic heating effect of $SiO_2$coated $ \Upsilon-Fe_2$$O_3$nanocomposite particle due to magnetic relaxational loss of superparamagnetic regime was investigated by measuring the generated heat from nanocomposite particles in alternative applied magnetic fields. The commercial $ \Upsilon-Fe_2$$O_3$nanoparticles were coated by SiO$_2$in water solution with TEOS and the synthesized nanocomposite powders and its magnetic properties were characterized and compared with the raw$ \Upsilon-Fe_2$$O_3$nanoparticles. The 10∼30 nm sized $ \Upsilon-Fe_2$$O_3$. nanoparticles were coated by 5 nm thickness of amorphous $SiO_2$film. The nanocomposite particle has very low Mr and Hc value showing superparamagnetic behavior The magnetic heating effect of nanocomposite particle on surface coating phase of $SiO_2$was discussed in terms of superparamagnetic behaviors of each particles, and their potential for hyperthermia application was evaluated.

• 폴리머
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• 제27권6호
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• pp.549-554
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• 2003

톨루엔, 자일렌 등 유기 용매에 녹는 에머랄딘 염 형태의 폴리아닐린-도데실벤젠술폰산 (PANI-DBSA) 이 한 단계 마이셀 유화 중합법에 의해 제조되었다. 유기 양성자산으로 DBSA가 사용되었으며, DBSA와 아닐린 단량체의 비율이 1.5:1의 중합 조건에서 용해도 및 전기적 특성이 가장 우수하였고, 이때 제조한 PANI-DBSA의 톨루엔에서 용해도는 8 wt% 정도이다. 이들은 유리 또는 플라스틱 필름 기판 위에 도포되어 필름 형상으로 얻어지며, 폴리우레탄 또는 폴리스티렌 등과도 쉽게 혼합되었다. 5 S/cm 이상의 전기 전도도와 500 nm 이하의 필름두께에서 70% 이상의 가시광선 투과도를 보이며, 필름의 표면상태가 수용액에서의 유화 중합법에 의해 제조되는 PANl-DBSA보다 매우 균일함을 AEM을 통해 관찰하였다. 반응생성물의 대부분은 톨루엔 용매에 용해되었지만 용해되지 않은 일부 PANI-DBSA은 50-400 nm크기의 입자로 유기 용매에 분산되어 있음이 확인되었고 이들 입자의 결정상태를 XRD를 통해 관찰하였다.