• Bulletin of the Korean Chemical Society
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• 제34권1호
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• pp.279-282
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• 2013

• Bulletin of the Korean Chemical Society
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• 제34권5호
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• pp.1361-1365
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• 2013

The smallest ketenimine and hydrogen cyanide N-methylide ($CH_2CNH$ and $CH_2NCH$) are provided from the argon/acetonitrile matrix samples exposed to radiation from laser ablation of transition-metals. New infrared bands are observed in addition to better determination of the vibrational characteristics for the previously reported bands, and the $^{13}C$ substituted isotopomers ($^{13}{CH_2}^{13}CNH$ and $^{13}CH_2N^{13}CH$) are also generated. Density functional frequency calculations and the D and $^{13}C$ isotopic shifts substantiate the vibrational assignments. $CH_2CNH$ is probably produced through single-step conversion of $CH_3CN$, whereas $CH_2NCH$ through two-step conversion via 2H-azirine. Inter-conversions between these two products evidently do not occur during photolysis and annealing.

• Bulletin of the Korean Chemical Society
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• 제20권12호
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• pp.1501-1505
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• 1999

Expansion dynamics of C$^{+}$ ions ejected from 355-nm laser ablation of graphite target in vacuum has been investigated by pulsed-field time-of-flight (TOF) mass spectrometry. A strong nonlinear dependence of the amount of desorbed C$^{+}$ ions on laser fluence is interpreted by the mechanism that C$^{+}$ ions are produced directly from the graphite via conversion of the multiphoton energy into thermal energy. The temporal evolution of C$^{+}$ ions was measured by varying the delay time of the ion repelling pulse with respect to the laser irradiation, which provides significant information on the ablated plume characterization. The TOF distributions of ablated ions showed a bimodal shape and could be fitted by shifted Maxwell-Boltzmann distributions. The velocity of the fast component increases with the delay time, whereas the slow component (< 500 m/s) exhibits a constant velocity. Also studied were the effects of the laser fluence on the energetics of C$^{+}$ ions.

• 한국항공우주학회지
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• 제41권8호
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• pp.597-604
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• 2013

본 논문에서는 열분해 및 삭마 환경의 복합재 구조물에 대한 열기계적 연계 해석을 수행하였다. 열분해 과정의 재료 밀도 감소, 기공 가스 확산, 흡열 반응 에너지와 삭마 과정에서의 표면 침식 효과 등을 고려하였다. 상용 유한요소 코드에 교차 연계 알고리듬을 적용하여 완전 연계된 열 해석 및 구조 해석 인터페이스를 구성하였다. 수치 실험을 통해서 탄소/페놀릭 복합재료의 기본적인 열분해 및 삭마 특성을 분석하였다. 특히, 화학적 및 기계적 삭마에 영향을 미치는 주요 인자에 따른 표면 침식량 등을 비교하였다. 또한, 열분해 과정의 수축 또는 팽창 변형도가 재료의 열기계적 거동에 미치는 영향도 검토하였다.

• 한국기계가공학회지
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• 제19권10호
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• pp.105-110
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• 2020

Radioactive Oxides are formed on the surface of the primary equipment in a nuclear power plant. In order to remove the oxide film that is formed on the surfaces of the equipment, chemical and physical decontamination technologies are used. The disadvantage of traditional technologies is that they produce secondary radioactive wastes. Therefore, in this study, the short-pulsed laser eco-friendly technology was used in order to reduce production of the secondary radioactive wastes. They were also used to minimize the damages that were caused on the base material and to remove the contaminated oxide film. The study was carried out using a Stainless steel 304 specimen that was coated with nickel-ferrite particles. Further, the laser source was selected with two different wavelengths. Furthermore, the depth of the coating layer was analyzed using a 3D laser microscope by changing the laser ablation conditions. Based on the analysis, the optimal conditions of ablation were determined using a 1064nm short-pulsed laser ablation technique in order to remove the radioactively contaminated oxide film from the irradiated stainless steel surface.

• JSTS:Journal of Semiconductor Technology and Science
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• 제4권3호
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• pp.217-221
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• 2004

[ $CO_2$ ]laser ablation rates for bulk 4H-SiC substrates and GaN/AIN/SiC templates in the range 229-870 ${\mu}m.min^{-1}$ were obtained for pulse energies of 7.5-30 mJ over diameters of 50·500 ${\mu}m$ with a Q-switched pulse width of ${\sim}30$ nsec and a pulse frequency of 8 Hz. The laser drilling produces much higher etch rates than conventional dry plasma etching (0.2 - 1.3 ${\mu}m/min$) making this an attractive maskless option for creating through-wafer via holes in SiC or GaN/AlN/SiC templates for power metal-semiconductor field effect transistor applications. The via entry can be tapered to facilitate subsequent metallization by control of the laser power and the total residual surface contamination can be minimized in a similar fashion and with a high gas throughput to avoid redeposition. The sidewall roughness is also comparable or better than conventional via holes created by plasma etching.

• 한국정밀공학회지
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• 제29권5호
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• pp.572-577
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• 2012

Recently porous polymer has widely been applied to packaging, heat isolation, and sound absorption in various fields from the electrics to the automobiles industry. A lot of micro porosities inside foamed polymer provide lower heat conduction and lighter weight than non-porous polymer, because they involve gas or air during foaming process. In this paper experimental approaches of the UV laser micro machining behavior for Expanded Polypropylene (EPP) foamed polymer materials, which have different expansion rates, were investigated. From these results, the ablation phenomena were finally observed that the ablation is depended upon stronger photo-chemical than photo-thermal effect. This study will also help us to understand interaction between UV laser beam and porous polymer.

• 한국재료학회지
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• 제30권5호
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• pp.262-266
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• 2020

In this paper, we investigated the effect of the passivation stack with Al₂O₃, hydrogenated silicon nitride (SiN_x:H) stack and Al₂O₃, silicon oxynitride (SiON_x) stack in the n type bifacial solar cell on monocrystalline silicon. SiNx:H and SiON_x films were deposited by plasma enhanced chemical vapor deposition on the Al₂O₃ thin film deposited by thermal atomic layer deposition. We focus on passivation properties of the two stack structure after laser ablation process in order to improve bifaciality of the cell. Our results showed SiN_x:H with Al₂O₃ stack is 10 mV higher in implied open circuit voltage and 60 ㎲ higher in minority carrier lifetime than SiON_x with Al₂O₃ stack at Ni silicide formation temperature for 1.8% open area ratio. This can be explained by hydrogen passivation at the Al₂O₃/Si interface and Al₂O₃ layer of laser damaged area during annealing.

• 한국레이저가공학회지
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• 제8권2호
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• pp.21-32
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• 2005

The excimer laser ablation of a polymer occurs by the excitation of chemical bonds to energy levels that are above the dissociation energy. In this process, however, fragmented debris is finally ejected explosively by the scission of bonds and accumulates on the material surface. In the present work, a process for eliminating surface debris contamination generated by the laser ablation of a polymer is developed. The proposed approach for removing surface debris utilizes an erasable ink pasted on a polymide. The ink pasted polyimide is ablated by KrF excimer laser. The surface debris ejected from the polyimide is then combined with the ink layer on the polymer. Finally, both the surface debris and the ink layer are removed using adhesive tape or alcohol solvent. The results suggest that the erasable ink method is a simple, low cost, and extremely effective debris eliminating process.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
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• pp.429-434
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• 2012

금속 연료로 사용되는 마이크로/나노 알루미늄 입자를 산화피막에 의한 점화 지연을 최소화 하는 점화 방법을 제시 하였다. 알루미늄 입자를 생성시킴과 동시에 가열하여 입자가 생성된 직후 산소와 접촉시 격렬한 산화 반응을 유도하여 점화를 시키는 방법이다. 1064 nm 파장의 Nd:YAG 펄스 레이저를 이용한 레이저 삭마(laser ablation)를 알루미늄 시편에 발생시켜 입자를 생성하였으며, 산란 기법(scattering method)을 이용하여 입자를 가시화하여 생성을 확인하였다. 10.6 ${\mu}m$ 파장의 $CO_2$ 연속 레이저를 사용하여 알루미늄 시편을 가열하고 생성된 입자의 점화 열원으로 사용하여 알루미늄 입자가 점화되고 연소되어 이동하는 궤적을 확인하였다.