• 대한의생명과학회지
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• 제14권2호
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• pp.105-113
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• 2008

The objective of this study was to evaluate the influence of surface modifications on the bonding characteristics and cytotoxicity of specific titanium porcelain bonded to milling titanium and cast titanium. Milling titanium and cast titanium samples were divided into 8 test groups. These groups are as follow: i) sandblasted with particles of different size of $220{\mu}m\;and\;50{\mu}m$, ii) different sequences of sandblasting treatment and etching treatment, iii) etched with different etching solutions, and iv) preheated or not. The surface characteristics of specimens were characterized by the test of mean roughness of surface and SEM. The bond strength of titanium-ceramic systems was measured by using three-point bending test and SEM. The results show that the mean roughness of surface of sample sandblasted with $220{\mu}m$ aluminum oxide increased and bond strength were higher than sample sandblasted with $50{\mu}m$ aluminum oxide. The mean roughness of surface decreased, but the bond strength increased when the samples sandblasted with $220{\mu}m$ aluminum oxide were preheated. The sample sandblasted with $220{\mu}m$ aluminum oxide after oxidized with occupational corrosive agent I (50% NaOH, 10% $CuSO_4{\cdot}5H_2O$) and II (35% $HNO_3$, 5% HF) showed higher bond strength than sample oxidized with 30% $HNO_3$ after sandblasted with $220{\mu}m$ aluminum oxide. Group NaCuNF220SP (milling Ti: 35.3985 MPa, casting Ti: 37.2306 MPa) which was treated with occupational corrosive agent I (50% NaOH, 10% $CuSO_4{\cdot}5H_2O$) and II (35% $HNO_3$, 5% HF), followed by sandblasting with $220{\mu}m$ aluminum oxide and preheating at $750^{\circ}C$ for 1 hour showed the highest bond strength and significant differences (P<0.05). The method for modifying surface of titanium showed excellent stability of cells.

• 한국환경과학회지
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• 제26권5호
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• pp.563-572
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• 2017

The Electrocoagulation-Flotation (ECF) process has great potential in wastewater treatment. ECF technology is effective in the removal of colloidal particles, oil-water emulsion, organic pollutants such as microalgae, and heavy metals. Numerous studies have been conducted on ECF; however, many of them used a conventional plate-type aluminum anode. In this study, we determined the effect of changing operational parameters such as power supply time, applied current, NaCl concentration, and pH on the turbidity removal efficiency of kaoline. We also determined the effects of different electrolyte types (NaCl, $MgSO_4$, $CaCl_2$, $Na_2SO_4$, and tap water), as well as the differences caused by using a plate-type and mesh-type aluminum anode, on the turbidity removal efficiency. The results showed that the optimal values of ECF time, applied current, NaCl concentration, and pH were 5 min, 0.35 A, 0.4 g/L NaCl in distilled water, and pH 7, respectively. The results also revealed that the turbidity removal efficiency of kaoline in different electrolytes decreased in the following sequence, given the same conductivity: tap water > $CaCl_2$ > $MgSO_4$ > NaCl > $Na_2SO_4$. The turbidity removal efficiency of the mesh-type aluminum anode was significantly greater than the plate-type aluminum anode.

• 한국분말재료학회지
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• 제14권2호
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• pp.123-126
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• 2007

In this work, the dispersion behavior of $Y_2O_3$ particles in binary aluminum (Al)-copper (Cu) cast alloy was investigated with respect to Cu contents of 20 (hypoeutertic), 33 (eutectic) and 40 (hypereutectic) wt.%. In cases of hypo and hypereutectic compositions, SEM images revealed that the primary Al and ${\theta}$ phases were grown up at the beginning, respectively, and thereafter the eutectic phase was solidified. In addition, it was found that some of $Y_2O_3$ particles can be dispersed into the primary Al phase, but none of them are is observed inside the primary 6 phase. This different dispersion behavior of $Y_2O_3$ particles is probably due to the difference in the val- ues of specific gravity between $Y_2O_3$ particles and primary phases. At eutectic composition, $Y_2O_3$ particles were well dispersed in the matrix since there is few primary phases acting as an impediment site for particle dispersion during solidification. Based on the experimental results, it is concluded that $Y_2O_3$ particles are mostly dispersed into the eutectic phase in binary Al-Cu alloy system.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.318-318
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• 2012

A graphene layer is most important materials in resent year to enhance the electrical properties of semiconductor device due to high mobility, flexibility, strong mechanical resistance and transparency[1,2]. The resistance switching memory with the graphene layer have been reported for next generation nonvolatile memory device[3,4]. Also, the graphene layer is able to improve the electrical properties of memory device because of the high mobility and current density. In this study, the resistance switching memory device with metal-oxide nano-particles embedded in polyimide layer on the graphene mono-layer were fabricated. At first, the graphene layer was deposited $SiO_2$/Si substrate by using chemical vapor deposition. Then, a biphenyl-tetracarboxylic dianhydride-phenylene diamine poly-amic-acid was spin coated on the deposited metal layer on the graphene mono-layer. Then the samples were cured at $400^{\circ}C$ for 1 hour in $N_2$ atmosphere after drying at $135^{\circ}C$ for 30 min through rapid thermal annealing. The deposition of aluminum layer with thickness of 200 nm was done by a thermal evaporator. The electrical properties of device were measured at room temperature using an HP4156a precision semiconductor parameter analyzer and an Agilent 81101A pulse generator. We will discuss the switching mechanism of memory device with metal-oxide nano-particles on the graphene mono-layer.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1999년도 유체기계 연구개발 발표회 논문집
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• pp.301-308
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• 1999

The present study investigates numerically particle laden flow through compressor cascades and a rocket nozzle. Engines are affected by various particles which are suspending in the atmosphere. Especially in the case of aircraft aviating in volcanic, industrial and desert region including many particles, each components of engine system are damaged severely. That damage modes are erosion of compressor blading and rotor path components, partial or total blockage of cooling passage and engine control system degradation. Numerical prediction and experimental data, erosion rates are predicted for two materials - ceramic, soft metal - on compressor blade surface. Aluminum oxide ($Al_2O_3$) Particles included in solid rocket propelant make ablative the rocket motor nozzle and imped the expansion processes of propulsion. By the definition of particle deposition efficiency, characteristics of particles impaction are considered quantitatively Stoke number is defined over the various particle sizes and particle trajectories are treated by Lagrangian approach. Particle stability is considered by definition of Weber number in rocket nozzle and particle breakup and evaporation is simulated in a rocket nozzle.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권6호
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• pp.246-252
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• 2002

This paper describes the acoustic emission measurement method to diagnose GIS for particles. We measured and analyzed the signals of acoustic waves using acoustic two types sensors with 125KHz and 50KHz resonant frequency respectively when the particles were dropped on the surfaces of circular plates and inside of GlS tanks. We found that the difference between peak outputs of two sensors depended on the types and materials of particles and the conditions of dropping position. These results showed that the outputs of 125KHz sensor were higher than those of 50KHz sensor in circular plate and 362㎸ GIS tank made of steel and vice versa in circular plate and 800㎸ GIS tank made of aluminum. The ratios outputs of 125KHz sensor to those of 50KHz sensor were 1.4 - 2.37 in 800㎸ GIS tank and were 0.5 - 1.0 in 362㎸ GIS tank. Therefore we knew that adaption of two types acoustic sensors which had different resonant frequencies as a very useful method in diagnosis of GIS.

• 대한금속재료학회지
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• 제48권3호
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• pp.248-255
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• 2010

The effect of various alloying elements and melt treatment on the microstructural control of Al-Sn metallic bearing alloy was investigated. The thickness of tin film crystallized around primary aluminum decreased with the addition of 5% Cu in Al-Sn alloy, with tin particles being reduced in size by intervening the Ostwald ripening. With the addition of Si in Al-10%Sn alloy, the tin particles were crystallized with eutectic silicon, resulting in uniform distribution of tin particles. With the addition of Cu and Si in Al-Sn alloy, both the tensile strength and yield strength increased, with the increasing rate of yield strength being less than that of tensile strength. Although the Al-10%Sn-7%Si alloy has similar tensile strength compared with Al-10%Sn-5%Cu, the former showed superior abrasion resistance, resulting from preventing the tin particles from movement to the abrasion surface.

• 대한환경공학회지
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• 제37권2호
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• pp.92-98
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• 2015

알루미늄 호일 부식 실험을 이용하여 초음파 토양 세척 공정의 설계를 위한 기초 연구가 수행되었다. 36 kHz 초음파 발생 모듈이 하부에 장착된 대형 초음파 반응기에 파이렉스 재질의 소형 반응기를 위치시키고 글라스 비드 크기(1, 2, 4 mm), 파이렉스 반응기 내 글라스 비드 높이(5, 10, 15, 20 mm), 글라스 비드 위 물 높이(5, 10, 15, 20 mm) 등의 다양한 조건에서 실험을 진행하였다. 실험 결과, 글라스 비드의 입자 크기가 클수록, 글라스 비드 위 수위가 증가할수록 알루미늄 호일의 부식 정도가 크게 증가하였는데 이는 입자가 클수록 빈 공간이 많이 생겨 초음파 감쇠 현상이 덜 일어나게 되기 때문이며, 또한 수위가 증가할수록 동일한 에너지 유입 조건에서 초음파 캐비테이션 현상이 보다 활성화되기 때문으로 판단되었다. 그러나 글라스 비드를 지나면서 초음파 감쇠 현상이 심하게 일어나 알루미늄 호일의 부식 정도가 상대적으로 매우 약하게 확인되어 부식이 활발하게 일어나는 반응기 하부, 즉 심각한 초음파 감쇠 현상이 일어나지 않는 바닥 부분으로 입자들을 지속적으로 보낼 수 있는 기계적 교반 등의 방안이 제안되었다.

• 한국세라믹학회지
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• 제34권2호
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• pp.195-201
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• 1997

본 논문은 kaolinite(Al2O3.2SiO2.2H2O)-aluminum trihydroxide(Al(OH3) 혼합물을 소결전에 planetary ball mill을 사용하여 건식 중에서 혼합분쇄한 후, 이 혼합물을 사용하여 소결하는 동안에 mullite의 생성거동을 연구한 것이다. 혼합물의 입자크기 감소는 분쇄 초기에 현저하였으며, 분쇄기간이 증가함에 따라 미립자들이 응집하는 현상을 보였다. 혼합물의 결정구조는 planetary ball milling에 의한 혼합분쇄에 따라 쉽게 비정질화되었으며, 비정질화되는 정도는 분쇄시간이 증가함에 따라 증가하였다. Kaolinite의 초기 분순물로 존재했던 anatase를 제외한 mullite상만이 상대적으로 낮은 소결온도인 1523K에서 혼합분쇄한 혼합물의 소결체에서 나타났다. 한편, 분쇄하지 않은 혼합물의 소결체의 경우는 이 온도에서 mullite 상 이외에 corundum, cristobalite, Al-Si spinel상이 공존하는 형태로 나타났다. 따라서, 혼합분쇄처리는 출발원료의 미소 규모에 있어서 균일혼합 및 분산을 촉진시키며, 또한 결정구조변화에 따른 열분해온도의 변화일으켜, 상대적으로 낮은 온도에서 고순도의 mullite를 직접 생성하는데 효과적이였다.

• 한국수소및신에너지학회논문집
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• 제15권3호
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• pp.235-243
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• 2004

A number of potential applications of aluminum foams are being identified and renewed interest in these engineering materials is also reflected by several current research projects. One of the key issues for industrial exploitation of aluminum foams is the development of cost-effective manufacturing strategies facilitating, preferably, net shape production of foams with controlled porosity and cell size, and minimized structural imperfection. Especially, melt route to aluminum foam production based on the foaming agents offer attraction of low cost and the potential for good microstructure. The present paper is focused mainly on foaming agents of melt-foam aluminum such as $TiH_2$ or $TiH_2-Al$ mixture. For the purpose of economical manufacturing, we are proposed to hydrogen induced mechanical alloying (HIMA) process. Thermo-physical properties of particles synthesized are compared with conventional methods. Specimens synthesized are characterized by scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), thermo- gravimetry-differential scanning calorymetry (TG-DSC), pressure-composition-isotherm. (PCI).