• Proceedings of the Materials Research Society of Korea Conference
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• 2002.05a
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• pp.48-48
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• 2002

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.1
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• pp.96-101
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• 2000

Ceramic, PCD and CBN tools are available for the difficult-to-cut-materials such as hardened carbon tool steel, stainless steel, Inconel 718 and etc.. Ceramic toolsare likely to be chipped and abruptly broken before the appearance of normal wear in turning. Ther2efore ceramic tools are suitable for continuous cut in turning not for intermittent in milling. In this study, TiN/TiCN multi-layer coated ceramic tools were found to restrain the chipping, breaking and early fracture and to increase the critical cutting speed owing to TiN/TiCN multi-layer coating in Arc Ion Plating of PVD method.

• Tribology and Lubricants
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• v.6 no.1
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• pp.116-125
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• 1990

An experimental programme was established to determine the wear behaviour of TiN coatings of thickness 1 $\mu$m and 3 $\mu$m. by PECVD with the variation of applied load, sliding velocity and sliding distance. It was shown that oxidation of transferred metal as sliding speed increased formed oxide film so that it contributed in decreasing the wear rate. With the roller-on-disc tribometer employed, the wear rate of the roller specimen was decreased with the increase in sliding distance due to the reduction in effective contact pressure. Finally, the severe cracks concentrated at the trailing edge of contact surface were explained in terms of high tensile stress prevailing at the trailing edge of the contact and were identified as a dominant wear mechanism as well as the strong local welding between coating layer and the counter surface, leading to the debonding of the coating layer.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.8
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• pp.54-61
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• 2010

In this research KP-4, one of the plastic mold steels, was coated with the AlTiN from one layer to four layers by the PVD method in the $\Phi$ cemented carbide ball end mill. Coated KP-4 was processed with various conditions. For example, slope of $15^{\circ}$, $30^{\circ}$ and $45^{\circ}$ the spindle rotation speed was changed from 10,000rpm to 16,000rpm, the tool feeding speed was changed from 1,300mm/min to 1,700mm/min, the depth of cut was also changed from 0.3mm to 0.9mm, and etc. Cutting component force according to the coating layer number, surface roughness, and the wear of tool were studied.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.4
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• pp.161-166
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• 2013

AlN buffer layers have been used for the growth of GaN layers on Si substrates. However, the doping of high concentration of carriers into AlN layers is still not easy, therefore it may cause the increase of series resistance when it is used for the electrical or optical devices. In this work, to improve such a problem, the growth of GaN layers on Si substrates were performed using metal buffer layers instead of AlN buffer layer. We tried combinations of Ti, Al, Cr and Au as metal buffer layers for the growth of GaN on Si substrates. Surface morphology was measured by optical microscope and scanning electron microscope (SEM), and optical properties and crystalline quality were measured by photoluminescence (PL) and X-ray diffractometer (XRD), respectively. Electrical resistances for both cases of AlN and metal buffer layer were compared by current-voltage (I-V) measurement.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.300-300
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• 2012

본 연구에서는 음극 아크 방전을 이용하여 빗각 증착으로 단층 또는 다층 구조를 갖는 TiN 코팅층을 제작하여 미세구조 변화가 코팅층 물성에 미치는 영향을 확인하였다. TiN 박막은 아크 소스에 장착된 99.5%의 Ti 타겟을 사용하여 아르곤과 질소 가스의 혼합가스 분위기에서 기판으로 사용된 스테인레스 강판 위에 코팅하였다. 기판과 타겟 간의 거리는 30 cm이며, 기판은 알코올과 아세톤으로 초음파 세척을 실시한 후 진공챔버에 장착하고 ${\sim}10^{-6}$Torr가지 진공배기를 실시하였다. 진공챔버가 기본 압력까지 배기되면 아르곤 가스를 주입하고 아크 소스에 약 70A의 전류를 인가하여 아크를 발생시키고 기판 홀더에 약 -400 V의 직류전압을 인가하여 약 5분간 청정을 실시 하였다. 기판의 청정이 끝나면 기판에 인가된 전압을 차단하고 질소 가스를 진공챔버에 주입하여 TiN을 코팅하였다. 빗각 증착을 위한 기판의 회전각은 $45^{\circ}$와 $-45^{\circ}$이며, TiN 박막의 총 두께는 약 $3{\mu}m$로 동일하게 유지하였다. 빗각 증착으로 TiN을 코팅하면 기울어진 주상정 구조를 갖는 박막이 제조되는 것을 확인할 수 있었다. 빗각 증착을 실시하는 중에 기판 홀더에 약 -100 V의 전압을 인가하면 빗각 효과가 사라지며 기판에 수직한 주상정이 성장한다는 사실을 확인하였다. $45^{\circ}$의 빗각으로 코팅한 단층 TiN 박막은 $0^{\circ}$로 코팅한 박막보다 경도가 감소하는 경향을 보였으나 $45^{\circ}$와 $-45^{\circ}$로 번갈아 코팅한 다층 TiN 박막은 zigzag 구조가 관찰되었으며 $0^{\circ}$로 코팅한 단층 TiN 박막보다 경도가 증가하는 경향을 보였다. 빗각으로 zigzag 구조의 다층 TiN 박막을 코팅하는 공정에서 최상층이 코팅될 때 기판 홀더에 전압을 인가해서 기판에 수직한 코팅층을 형성하면 가장 높은 경도 증가를 보였다. 본 연구에서 얻어진 결과를 이용하여 다양한 형태의 박막 구조 제어가 가능하고 이러한 미세구조 제어를 통해서 박막의 물성도 제어가 가능할 것으로 판단된다.

• Korean Journal of Materials Research
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• v.12 no.7
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• pp.560-567
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• 2002

Titanium (Ti) is a bioinert material and has lower elastic coefficient and better strength/volume property than other metals. Ferroelectric materials show alignment of positive and negative charges by poling treatment. This study was purposed to develop a new implant system by combining the advantages of Ti and ferroelectric property of $BaTiO_3$ (BTO). It was performed with the assumption that the $Ca^{2+ }$ ions would be easily attracted on negatively charged surface and the attracted cation might behave as nuclei for bone-like crystal growth in biological solutions. A ferroelectric BTO thin film on Ti was fabricated and the effect of poling treatment on the improvement of calcium phosphate (Ca-P) formation in biological solutions was evaluated. After immersion in Eagle’s minimum essential media (MEM) solution, NaCl was formed on Ti, and Ca-P layer containing NaCl was formed on Ti-O. Weak and sparse Ca-P layers were formed on BTO, while thick, homogeneous, and dense Ca-P layer was formed on negatively polarized BTO (N-BTO), which was confirmed by FE-SEM and EDX. In summary, these results demonstrate that poling the ferroelectric BTO surface negatively is effective for the formation of Ca-P layer in MEM solution, and that N-BTO coating on Ti could be used as a possible alternative method for enhancing the osseointegration of the implants.

• Journal of the Microelectronics and Packaging Society
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• v.4 no.2
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• pp.47-54
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• 1997

Pt/SiO2/Si을 기판으로 사용하고 RF 마그네트론 스퍼터링에 의한 (Ba, Sr)TiO3 (BST) 씨앗층을 약 10nm 정도의 두께로 입힌 다음 그 상부에 화학 기상증착법으로 BST를 증착하여 BST seed layer가 CVD BST 박막의 특성에 미치는 영향을 조사하였다. 또한 급 속열처리가 BST 박막과 커패시터의 특성에 미치는 영향도 조사하였다. Seed layer와 급속 열처리에 의해 박막의 결정성이 향상되었으며 이로인해 유전상수가 증가되었고 주파수에 대 한 유전특성도 개선되었다. Seed layer를 도입함으로써 BST 박막과 Pt 하부전극 사이의 계 면에 존재하고 있는 산소부족\ulcorner이 사라짐을 확인할수 있었으며 이로 인해 Pt/BST/Pt 커\ulcorner 시터의 누설전류가 감소하였다. 또한 급속 열처리에 의해 BST/Pt 계면에서 트랩된 전자의 농도가 감소함으로써 누설전류 특성이 개선됨을 알수 있었다. Seed layer 위에 증착된 CVD BST 박막의 유전상수는 증착온도가 증가함에 따라 증가하였으나 누설전류도 같이 증가하 였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.318-318
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• 2010

We present the effect of interlayers of polymer tandem solar cells on their photovoltaic performance. P-type and n-type interlayers are essential for the series-connection of the subcells and enable to form the tandem cell architecture by the solution processing. In this study, we use PEDOT:PSS, nanocrystalline $TiO_2$, and blends of semiconducting polymers and fullerene derivatives as a hole transporting layer, electron transporting layer, and photoactive layers, respectively. We show that photovoltaic performances of polymer tandem solar cells depending on various PEDOT:PSS layers with the different electric conductivity and the various $TiO_2$ layer thickness.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.2
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• pp.139-145
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• 2015

In this paper, the flexible piezoelectric nanocomposite generator(NCG) device based on $BaTiO_3$ nanostructures was fabricated via simple and low-cost spin coating method. The $BaTiO_3$ nanostructures synthesized by self-assembly reaction showed dendrite morphologies. To produce the piezoelectric nanocomposite(p-NC layer) which acts as an electric energy source in NCG device, the piezoelectric nanopowders($BaTiO_3$) were dispersed in polydimethylsiloxane(PDMS). Sequently, the p-NC layer was inserted in two dielectric layer of PDMS; these layers enabled the NCG device flexibility as well as durability prohibiting detachment(exfoliation) for significantly mechanical bending motions. The fabricated NCG device shows average maximum open circuit voltage of 6.2 V and average maximum current signals of 300 nA at 20 wt% composition of $BaTiO_3$ nanostructures in p-NC layer. Finally, the flexible energy harvester generates stable output signals at any rate of frequency which were used to operate LCD device without any external energy supply.