• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.332-335
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• 2007

The superplastic forming (SPF) has been widely used in the automotive and aerospace industry because it has great advantages to produce very light and strong components. Finite element method (FEM) is used to model the process of superplastic forming/diffusion bonding (SPF/DB), to predict the pressure-time curve and to analyze the process parameter. In this study, process design of SPF/DB is carried out a 3-sheet sandwich part. SPF/DB process with pressure control was analyzed by using finite element method. For obtaining proper shape, step-by-step pressurization is proposed. The first step of SPD/DB process is obtained by applying of pressure in patches. From the next step it applied pressure to all regions (between inner sheets, between inner and face sheets). By using the proposed pressurization scheme, deficit in part shape is found to be eliminated.

• Bulletin of the Korean Chemical Society
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• 제34권6호
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• pp.1814-1822
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• 2013

By using density functional theory calculations, we have performed a systemic study on the electronic structures and topological properties of interactions between N-butylpyridinium nitrate ($[BPY]^+[NO_3]^-$) and thiophene (TS), benzothiophene (BT), dibenzothiophene (DBT), naphthalene (NAP). The most stable structure of $[BPY]^+[NO_3]^-$ ion pair indicates that hydrogen bonding interactions between oxygen atoms on $[NO_3]^-$ anion and C2-H2 on pyridinium ring play a dominating role in the formation of ion pair. The occurrence of hydrogen bonding, ${\pi}{\cdots}$H-C, and ${\pi}{\cdots}{\pi}$ interactions between $[BPY]^+[NO_3]^-$ and TS, BT, DBT, NAP has been corroborated at the molecular level. But hydrogen bonding and ${\pi}{\cdots}{\pi}$ interactions between $[BPY]^+[NO_3]^-$ and NAP are weak in terms of structural properties and NBO, AIM analyses. DBT is prior to adsorption on N-butylpyridinium nitrate ionic liquid.

• 비파괴검사학회지
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• 제16권2호
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• pp.79-85
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• 1996

복합 재료의 single-lap 및 double-strap adhesive bonding joint 시험편에서 피로 및 인장시험시 방출되는 AE 신호의 분석에 의한 피로 수명 예측 및 파괴 과정의 감시에 대한 연구를 수행하였다. Bonding 시험편의 피로시험시 AE event의 발생양상은 피로에 의해 축적된 elastic strain energy의 방출과 관계되며, peak amplitude가 높고 event duration이 긴 event의 발생 영역과 peak amplitude가 낮고 event duration이 짧으나 많은 event가 발생되는 영역으로 나눌 수 있었다. 그리고 두 영역 사이의 경계 cycle은 피로 수명의 70-80% 근방에 존재하였으며, 이를 이용한다면 피로 수명의 예측이 가능하리라 판단된다.

• 한국광학회지
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• 제7권1호
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• pp.72-76
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• 1996

Metallic glass 1605SC, 2826MB 두 재질에 대해 세 가지 본딩 구조를 가지는 광섬유 자왜변환기를 구성하여 구조에 따른 여러가지 자왜응답특성을 측정해 보았다. 측정결과 두 재질 모두에서 양끝 본딩이 경우 가장 좋은 자왜응답특성을 보였다. 2605SC의 경우 양끝 본딩구조를 가진 자왜변환기의 유효자왜상수 $C_{eff}$, saturation magnetostriction .lambda.$_{s}$ , 최소감지자계 $H_{min}$은 각각 1.2*$10^{-5}$O $e^{-2}$ , 7.4*$10^{-4}$ , 1.6*$10^{-7}$ Oe/.root.Hz로 측정되었고, 2826MB재질의 경우 양끝 본딩구조에서의 유효자왜상수 $C_{eff}$, saturation magnetostriction .lambda.$_{s}$ 는 각각 7.6*$10^{-6}$ O $e^{-2}$ , 3.4*$10^{-4}$ 로 측정되었다.되었다.

• 한국표면공학회지
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• 제29권2호
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• pp.93-99
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• 1996

In this work BN thin films were deposited on Si substrate by R. F. sputtering method at $200^{\circ}C$ and in Ar + $N_2$ mixed gas atmosphere. In order to investigate the effect of ion bombardment on substrate for c-BN bonding, substrate bias voltage was applied. The optimum substrate bias voltage for c-BN bonding was determined by FTIR analysis on specimens which were deposited with various bias voltages. Then BN thin film was deposited with this optimum condition and its phase, morphology, chemical composition, and refractive index were compared with those of BN film which was deposited without bias voltage. FTIR results showed that BN films deposited with substrate bias voltage were composed of mixed phases of c-BN and h-BN, while those deposited without bias voltage were h-BN only. When pure Ar gas was used for sputtering gas, BN films were delaminated easily from substrate in air, while when 10% $N_2$ gas was added to the sputtering gas, although c-BN specific infrared peak was reduced, delamination did not occur. GXRD and TEM results showed that BN films were amorphous phases regardless of substrate bias voltage, and AES results showed that the chemical compositions of B/N were about 1.7~1.8. The refractive index of BN film deposited with bias voltage was higher than that without bias voltage. The reason is believed to be the existence of c-BN bonding in BN film and the higher density of film that deposited with the substrate bias voltage.

• 반도체디스플레이기술학회지
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• 제21권4호
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• pp.6-13
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• 2022

The electrostatic phenomenon seriously issued in extreme ultraviolet semiconductor cleaning was studied in junction with molecular dynamic aspect. It was understood that two lone pairs of electrons in water molecule were subtly different each other in molecular orbital symmetry, existed as two states of large energy difference, and became basis for water clustering through hydron bonds. It was deduced that when hydrogen bond formed by lone pair of higher energy state was broken, two types of [H₂O]⁺ and [H₂O]^- ions would be instantaneously generated, or that lone pair of higher energy state experiencing reactions such as friction with Teflon surface could cause electrostatic generation. It was specifically observed that, in case of electrolyzed cathode water, negative electrostatic charges by electrons were overlapped with negative oxidation reduction potentials without mutual reaction. Therefore, it seemed that negative electrostatic development could be minimized in cathode water by mutual repulsion of electrons and [OH]^- ions, which would be providing excellences on extreme ultraviolet cleaning and electrostatic control as well.

• Bulletin of the Korean Chemical Society
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• 제34권2호
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• pp.609-614
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• 2013

Extended H$\ddot{u}$ckel tight-binding band structure calculations are used to address the chemical bonding and elastic properties of $Zr_2AC$ (A=Al, Si, P, and S). Elastic properties are interpreted by analyzing the density of states and the crystal orbital overlap population for the respective phases. Our results show that the bulk modulus of these ternary compounds is determined by the strength of Zr-A bonds.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 춘계학술대회 논문집
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• pp.497-502
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• 1998

To understand the effect of surface roughness on silicon wafer bonding, a continuum mechanical model is presented. This model is based on Obreimoff's experiment and the contact theory of rough surfaces. The surface energy of silicon was calculated to be much reduced than the theoretical value. Problems are discussed concerning surface film effects and the assumption of constant asperity radius and statistical distribution function.

• Bulletin of the Korean Chemical Society
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• 제29권10호
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• pp.1951-1959
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• 2008

Pentamer cluster of azodicarbonamide (ADA) based on the crystalline structure was investigated for the equilibrium structure, the stabilization energies, and the vibrational properties at various levels of the density functional theory. Stretching force constants of N${\cdot}{\cdot}{\cdot}$H or O${\cdot}{\cdot}{\cdot}$H, and angle-bending force constants of N-H${\cdot}{\cdot}{\cdot}$N or N-H${\cdot}{\cdot}{\cdot}$O for intermolecular hydrogen bonds in the pentamer cluster were obtained in 0.2-0.5 mdyn/$\AA$ and 1.6-2.0 mdyn$\AA$, respectively. The geometry of central ADA molecule fully hydrogen bonded with other four molecules shows good coincidence to the crystalline structure except the bond distances of N-H. Calculated Raman and infrared spectra of central ADA molecule in cluster represent well the experimental spectra of ADA obtained in the solid state compared to a single molecule. Detailed structural and vibrational properties of central ADA molecule in the pentamer cluster are presented.

• 센서학회지
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• 제3권2호
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• pp.74-80
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• 1994

Silicon direct bonding 기술은 잔류 응력이 없고, 안정한 특성을 가진 센서의 제작과 silicon-on-insulator 소자의 제조에 널리 이용되고 있다. SDB의 공정 절차는 크게 실리콘 웨이퍼의 수산화 공정 과정과 wet oxidation fumace에서 고온의 열처리 공정 과정을 거치게 된다. 수산화 공정을 행한 후, Fourier transformation-infrared spectroscopy를 사용하여 실리콘 웨이퍼 표면을 분석하여 보면, 실리콘 웨이퍼의 표면에서는 수산화기가 생성됨을 알 수 있다. 실험 결과, $H_{2}O_{2}\;:\; H_{2}SO_{4}$ 용액을 사용한 친수성 용액 처리의 경우에 있어서는 수산화기가 3474 $cm^{-1}$ 주위의 넓은 영역에서 관찰되었다. 그러나, diluted HF 용액의 경우에 있어서는 수산화기가 관찰되지 않았다. 접합된 실리콘웨이퍼를 tetramethylammonium hydroxide 식각 용액을 사용하여 식각 공정을 수행하였다. 식각 공정은 자동 식각 중지가 수행되었으며, 식각된 표면은 평탄하고 균일하였다. 그러므로, 이러한 SDB 기술은 우수한 특성을 가진 압력, 유속, 가속도 센서 등과 같은 센서의 제작 및 센서 응용 분야에 이용될 수 있을 것이다.