• Journal of Surface Science and Engineering
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• v.34 no.2
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• pp.161-168
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• 2001

A Thermal Barrier Coating (TBC) can play an important role in protecting parts from harmful environments at high temperatures such as oxidation, corrosion, and wear in order to improve the efficiency of aircraft engines by lowering the surface temperature of the turbine blade. The TBC can increase the life span of the product and improve the operating properties. Therefore, in this study the mechanical and thermal properties of the TBC such as oxidation, fatigue and shock at high temperatures were evaluated. A samples of a bond coat (CoNiCrAlY) produced by the High Velocity Oxygen Fuel (HVOF) and Low Pressure Plasma Spray (LPPS) method were used. The thickness of the HVOF coating layer was approximately $450\mu\textrm{m}$ to 500$\mu\textrm{m}$ and the hardness number of the coating layer was between 350Hv and 400Hv. The thickness of the LPPS coating was about 350$\mu\textrm{m}$ to 400$\mu\textrm{m}$ and the hardness number of the coating was about 370Hv to 420Hv. The X-ray diffraction analysis showed that CoNiCrAlY coating layer of the HVOF and LPPS was composed of the $\beta$and ${\gamma}$phase. After the high temperature oxidation test, the oxide scale with about l0$\mu\textrm{m}$ to 20$\mu\textrm{m}$ thickness appeared at the coating surface on the Al-depleted zone was observed under the oxide scale layer.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1175-1178
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• 2005

Nanosize cobalt aluminate($CoAl_2O_4$) power as filter layer was coated to improve the color purityand contrast performances on inner face of CRT panel. We simulated color properties by measuring the transmittance and thickness of the coated filter layer. Contrast performance could be improved and color gamut was also changed because of the selective light absorption of filter layer at $580{\sim}605\;nm$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.6
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• pp.269-275
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• 2005

Ni/Ni-aluminide/Ti/Ti-aluminide laminate composite, considered as a functionally gradient material, was manufactured by thin foil hot press technique. Thick intermetallic layers of NiAl and $TiAl_3$ were formed by a self-propagating high-temperature synthesis (SHS) reaction, and thin continuous taters of $Ni_3Al$ and TiAl were formed by a solid-state diffusion. Fracture resistance with loading along the crack arrester direction is higher than crack divider direction due to the interruption of crack growth in metal layers. The $Ni_3Al$ and NiAl intermetallic layer showed cleavage and intergranular fracture behavior, respectively, while the fracture mode of $TiAl_3$ layer was found to be an intragranular cleavage. The debonding between metal and intermetallic layer and the pores were observed in the Ni/Ni-aluminide layers, resulting in the lower fracture resistance. With the results of acoustic emission (AE) source characterization the real time of failure and the effect of AE to crack growth could be monitored.

• Journal of the Korean Vacuum Society
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• v.15 no.3
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• pp.280-286
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• 2006

A distributed Bragg reflector (DBR) for the application of $1.3{\mu}m$ vertical cavity surface emitting laser (VCSEL) has grown by digital-alloy AlGaAs layer using the molecular beam epitaxy (MBE) method. The measured reflection spectra of the digital-alloy AlGaAs/GaAs DBR have uniformity in 0.35% over the 1/4 of 3-inch wafer. Furthermore, the TEM image showed that the composition and the thickness of the digital-alloy AlGaAs layer in AlGaAs/GaAs DBR was not affected by the temperature distribution over the wafer whole surface. Therefore, the digital-alloy AlGaAs/GaAs DBR can be used to get higher yield of VCSEL with the active medium of InAs quantum dots whose gain is inhomogeneously broadened.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.689-689
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• 2013

Atomic layer deposition (ALD)에 의한 알루미늄 산화 막(Al2O3)은 고효율 결정질 실리콘 태양전지를 위한 우수한 표면 패시베이션 특성을 제공한다. 알루미늄 산화막는 고정적인 음전하를 가지고 있기 때문에 p-형 실리콘 태양 전지 후면은 전계에 의한 우수한 패시베이션 효과를 형성한다. 그러나, ALD 방식으로 증착된 알루미늄 산화막은 매우 긴 공정 시간을 필요로 하기 때문에 기존의 실리콘 태양 전지 공정에 적용하기가 어렵다. 본 논문에서는 알루미늄 산화막 형성에서 공정 시간을 줄이기 위해 Plasma assisted atomic layer deposition (PA-ALD) 방식을 적용했다. PA-ALD 기술은 trimethylaluminum (TMA)과 O2를 사용하여 기판 표면에 알루미늄 산화막을 증착하는 것으로 ALD 방식과 유사하지만, O2 플라즈마를 사용함으로써 증착 속도를 향상시킬 수 있다. 이는 좋은 패시베이션 특성을 가지는 알루미늄 산화막을 실리콘 태양전지양산 공정에 적용할 수 있는 가능성을 제시한다. PA-ALD 방식에 의한 알루미늄 산화막의 패시베이션 특성을 최적화하기 위해서 증착 후 열처리 조건에 대한 연구도 수행하였다. 막증착률이 1.1${\AA}$/cycle인 Al2O3층의 두께 변화에 따른 특성을 최적화하기 위해 공정 온도를 $250^{\circ}C$ 고정하고, 열처리 온도와 시간을 가변하였으며 유효 반송자수명을 측정하여 알루미늄 산화막의 패시베이션 특성을 확인했다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.251-254
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• 2012

In this paper, the output characteristics of GaN-based LED considering quantum well structure are analyzed. The basic structure of the LED consists of active region of GaN barrier and InGaN quantum well between AlGaN EBL(Electron Blocking Layer) and AlGaN HBL(Hole Blocking Layer) on GaN buffer layer. The output power, internal quantum efficiency characteristics of LED active region considering thickness of quantum well, number of quantum well and doping of barrier are analyzed using ISE-TCAD.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.286-286
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• 2010

The lack of homogeneously sized single-walled carbon nanotubes (SWNTs) hinders their many applications because properties of SWNTs, in particular electrical conduction, are highly dependent on the diameter and chirality. Therefore, the preferential growth of SWNTs with predetermined diameters is an ultimate objective for applications of SWNTs-based nanoelectronics. It has been previously emphasized that a catalyst size is the one crucial factor to determine the CNTs diameter in chemical vapor deposition (CVD) process, giving rise to several attempts to obtain size-controllable catalyst by diverse methods, such as solid supported catalyst, metal-containing molecular nanoclusters, and nanostructured catalytic layer. In this work, diameter-controlled CNTs were synthesized using a nanostructured catalytic layer consisting of Fe/Al2O3/Si substrate. The CNTs diameter was controlled by structural modification of Al2O3 supporting layer, because Al2O3 supporting layer can affect agglomeration phenomenon induced by heat-driven surface diffusion of Fe catalytic nanoparticles at growth temperature.

• Transactions of Materials Processing
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• v.7 no.5
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• pp.465-473
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• 1998

The effect of alloying elements of Ag-Cu-Zr-X brazing alloy on the microstructure and the bond strength of $Al_2O_3/Ni-Cr$ brazed steel joint was investigated. The reaction layer, $ZrO_2$ (a=5.146 ${\AA}$ , b=5.213 ${\AA}$ , c=5.311 ${\AA}$ )was formed at the interface of $Al_2O_3/Ni-Cr$ steel joint by the redox reaction between alumina and Zr. The addition of An and Al to the Ag-Cu-Zr brazing alloy gave rise to changes in the thickness of the reaction product layer and the morphology of the brazement. Sn caused the segregation of Zr was decreased b Al the $ZrO_2$ layer formed at the Ag-Cu-Zr-Al alloy was thinner than that of $ZrO_2$ formed at the Ag-Cu-Zr-An alloy. The fracture shear strength was strongly dependent on the microstructure of the brazement. Brazing with Ag-Cu-Zr-Sn alloy resulted in a better bond strength than with Ag-Cu-Zr or Ag-Cu-Zr-Al alloy.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.93-93
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• 2009

실리콘 태양전지의 효율 향상을 위한 노력의 일환으로 결정질 실리콘 웨이퍼 표면passivation 물질 중 Atomic Layer Deposition (ALD)을 이용하여 증착한 $Al_2O_3$ 박막에 대한 관심이 증가하고 있다. 본 연구에서는 $Al_2O_3$ 박막의 증착 전 실리콘 웨이퍼의 산화막 두께에 따른 passivation 효과에 대해서 연구하였다. 실리콘 산화막은 $HNO_3$ 용액을 사용하여 화학적으로 생성시켰으며 $HNO_3$ 용액과의 반응 시간을 조절하여 실리콘 산화막의 두께를 조절하였다. 실리콘 산화막 생성 후 ALD로 $Al_2O_3$ 박막을 증착하였으며 증착 후 $N_2$ 분위기에서 annealing 하였다. Annealing 후 passivation 효과는 Quasi-Steady-State Photo Conductance를 사용하여 minority carrier의 lifetime을 측정하였다. Capacitance-Voltage measurement, Transmission Electron Microscopy, Ellipsometry를 사용하여 실리콘 산화막의 두께에 따른 $Al_2O_3$ 박막의 passivation 효과를 분석하였다.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.245-251
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• 2004

This paper is studied on the effect of TiAlN coated Ball End Mill and MQL(Minimum Quantity Lubrication) cutting condition on cutting characteristic of high hardness steels. KP4 steels[HRC32] and STD11[HRC60] heat treated steels were used as the workpiece and WC-Co ball end mill and single and multi layer TiAlN coated ball end mill were utilized in the cutting tests. MQL device was used to spray botanical oil coolant. Result showed that TiAlN coated ball end mill were increased the cutting length than WC-Co ball end mill in the cutting speed[$245{\sim}320m/min$] about $2.3{\sim}5.7$ times for KP4 steels and about $2.5{\sim}4.3$ times far STD11 heat treated steels. The multi layer TiAlN coated ball end mill is good for KP4 steels than single layer coated.