• Bulletin of the Korean Chemical Society
• /
• 제33권6호
• /
• pp.1925-1928
• /
• 2012

Adsorption of alkali metals (Li, Na, and K) on the surface of magnesium oxide nanotubes (MgONTs) with different diameters was investigated using density functional theory. According to the obtained results, the most stable adsorption site was found to be atop the oxygen atom of the tube surface with adsorption energies in the range of -0.25 to -0.74 eV. HOMO-LUMO gap ($E_g$) of the tubes dramatically decreases upon the adsorption of the alkali metals, resulting in enhancement of their electrical conductivity enhancement. The order of $E_g$ decrement caused by the metal adsorption is as follows: K > Na > Li. The results suggest that the MgONTs were transformed from semi-insulator to semiconductor upon the alkali metal adsorption. Increasing the tube diameter, the HOMO/LUMO gap of the pristine tube is enhanced and adsorption energies of the alkali metals are decreased.

• Structural Engineering and Mechanics
• /
• 제58권4호
• /
• pp.677-687
• /
• 2016

On the basis of the energy approach it is reported a development of the yield function and the constitutive equations for the orthotropic material with consideration of the crystal lattice constants and parameters of the crystallographic texture for the general stress state. For practical use in sheet metal forming analysis it is considered different loading scenarios: plane stress and plane strain states. Using the proposed yield function, the influence of single ideal components on the shape of yield surface was analyzed. The six texture components investigated here were cube, Goss, copper, brass, S and rotated cube, as these components are typically observed in rolled sheets from FCC alloys.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.43-44
• /
• 2006

The production method of micro sacrificial plastic mold insert metal injection molding, namely ${\mu}-SPiMIM$ process has been proposed to solve specific problems involving the miniaturization of MIM. Two types of sacrificial plastic molds (SP-mold) with fine structures were used: 1) PMMA resist, 2) PMMA mold injected into Ni-electroform, which is a typical LIGA (${\underline{L}}ithographie-{\underline{G}}alvanoformung-{\underline{A}}bformung$) process. Stainless steel 316L feedstock was injection-molded into the SP-molds with multi-pillar structures. This study focused on the effects of metal particle size and processing conditions on the shrinkage, transcription and surface roughness of sintered parts.

• 센서학회지
• /
• 제29권6호
• /
• pp.369-373
• /
• 2020

A hydrogen sensor was fabricated by utilizing a bundle of metal oxide nanostructures whose growth positions were selectively controlled by utilizing graphene, which is a carbon of atomic-unit thickness. To verify the reducing ability of graphene, it was confirmed that the multi-composition metal oxide V₂O₅ was converted into VO₂ on the graphene surface. Because of the role of graphene as a reducing catalyst, it was confirmed that ZnO and MoO₃ nanostructures were grown at high density only on the graphene surface. The fabricated gas sensor showed excellent sensitivity.

• 한국표면공학회지
• /
• 제26권6호
• /
• pp.327-333
• /
• 1993

The effect of heat treatment on the adhesion between Cu-18wt% Cr film and polyimide has been studied by using T-peel test, AES, and XRD. Cu-18wt% Cr alloy and pure Cu films were sputter deposited onto pol-yimide. Cu was electroplated before and after heat treatment at $400^{\circ}C$ for 0.5 hr and 2 hrs respectively. The adhesion of metal film onto polyimide was considerably good before heat treatment, but heat treatment re-duced the peel adhesion strength in all specimens. The reduction in adhesion in adhesion strength values in the specimens which were plated after heat treatment was mainly due to Cr-O rich pahse formed in the metal/polyimide in-terface. In the specimens which were heat treated after plating, the enhanced ductility in the metal films con-tributes the peel adhesion strength by increasing the amount of deformation in metal strips.

• Advances in nano research
• /
• 제6권4호
• /
• pp.357-375
• /
• 2018

Two dimensional (2D) atomic layered nanomaterials exhibit some of the most striking phenomena in modern materials research and hold promise for a wide range of applications including energy and biomedical technologies. Graphene has received much attention for having extremely high surface area to mass ratio and excellent electric conductivity. Graphene has also been shown to maximize the activity of surface-assembled metal nanoparticle catalysts due to its unique characteristics of enhancing mass transport of reactants to catalysts. This paper specifically investigates the strategy of pre-formed nanoparticle self-assembly used for the formation of various metal nanoparticles supported on graphene families such as graphene, graphene oxide, and reduced graphene oxide and aims at understanding the interactions between ligand-capped metal nanoparticles and 2D nanomaterials. By varying the functional groups on the ligands between alkyl, aromatic, amine, and alcohol groups, different interactions such as van der Waals, ${\pi}-{\pi}$ stacking, dipole-dipole, and hydrogen bonding are formed as the 2D hybrids produced.

• 분석과학
• /
• 제14권4호
• /
• pp.349-355
• /
• 2001

금속 염화물을 이용한 화학적 활성화 방법으로 페놀 수지로부터 미세기공과 증기공을 가지는 활성탄을 제조하였다. 본 연구에서 질소 흡착 데이터는 생성된 활성탄 표면의 물리적 성질을 특성화하는데 사용하였다. 표면 특성과 공동분포 분석 결과로부터, 페놀수지는 $962.3m^2/g$ 이상의 비표면적을 가지는 미세기공과 증기공을 가지는 활성탄을 생성함을 나타내었다. 이러한 동공구조를 가지는 활성탄은 금속 염화물($CdCl_2$, $CuCl_2$)의 양을 조절하여 만들어 졌으며, 동공의 발달은 금속염화물의 양이 증가함에 따라 증가함을 알 수 있었다. 열역학적인 DSC 데이터로부터, 첫 번째 발열반응의 엔탈피 변화 값(${\Delta}H$)은 금속염화물의 증가와 함께 증가하였다.

• 한국광학회지
• /
• 제17권4호
• /
• pp.371-380
• /
• 2006

금으로 된 금속선 광 도파로를 따라 속박되는 장거리 표면 플라즈몬을 이용하여 파장 가변 필터를 설계하고 제작하였다. 실리콘 기판 위에 제작된 금속선 도파로는 두 층의 열광학 폴리머 사이에 샌드위치 구조로 끼어 있도록 설계되었다. 도파로의 바로 윗면에는 유전체로 된 Bragg 회절격자가 적합한 주기로 제작되어, 중심 파장이 광통신 파장대 (1520$\sim$1570 nm)에 있으면서 높은 소광률($\sim$25 dB)을 갖는 파의 반사가 가능했고, 전체손실은 25 dB/cm 이하로 나타났다. 또한, 제작된 파장 가변 필터가 폴리머의 열-광학적 특성에 의해 파장가변 필터 소자로서의 응용이 가능함을 확인했으며, 금속선 광 도파로에 직접 연결된 전극 구조에 동시에 가해준 전류에 의해 파장이 가변 될 수 있음을 실험적으로 확인하였다.

• 비파괴검사학회지
• /
• 제35권1호
• /
• pp.52-60
• /
• 2015

원자력발전소에는 탄소강과 스테인리스강 용접을 위해 alloy600 용접재를 적용한 이종금속용접부가 다수 존재하며, 전 세계적으로 이종금속용접부에서 결함 발생 보고가 지속되고 있다. 주기적인 건전성 평가를 위해 이종금속용접부 초음파검사 일반절차서 (KPD-UT-10)를 적용하여 검사를 수행하고 있으며, 검사절차서에서는 탐촉자와 검사체 표면 사이의 간격을 최대 1/32"(0.8mm) 이내로 제한하고 있다. 국내의 일부 이종금속용접부는 테이퍼진 형상과 불규칙한 표면 형상을 가지고 있어, 가변형 위상배열초음파기술을 적용하여 검사 신뢰성을 높이고자 본 연구를 수행하였다. 연구 결과, 검사체 표면이 불규칙한 시편 내부의 인공결함에 대한 검출이 양호하였고, 이를 통해, 가변형 위상배열초음파기술의 현장 적용 가능성을 확인하였다.

• 마이크로전자및패키징학회지
• /
• 제8권1호
• /
• pp.53-59
• /
• 2001

Surfaces of PTFE and PVDF were modified by ion-assisted reaction (IAR) in which 1 keV $Ar^{+}$ ions were irradiated on the surface of the polymer with varying ion dose in an oxygen gas environment, and Cu, Pt, Al and Ag thin films were deposited on the modified polymers. Wettability of the modified polymers was largely improved by the formation of hydrophilic groups due to chemical reaction between polymer surface and the oxygen gas during IAR. The change in wettability in the modified polymers was also related to the change in surface morphology and roughness. Adhesion between metal films and polymers modified by IAR was significantly improved, so that no detachment was possible in the $Scotch^{TM}$ tape test. The increase of adhesion strength between the metal film and the modified PVDF was mainly attributed to the formation of hydrophilic groups, which interacted with the metal film. In the case of the modified PTFE, the enhanced adhesion to metal film could be explained by the change in surface morphology together with the formation of hydrophilic groups. The electrical properties of the metal films on the modified polymers were also investigated.