• 대한기계학회논문집B
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• 제25권11호
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• pp.1483-1491
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• 2001

Enhancement of pulsed-laser ablation by an artificially deposited liquid film is presented. Measurements of ablation rate, ablation threshold, and surface topography arc performed. Correlation between material ablation and photoacoustic effect is examined by the optical beam deflection method. The dependence of ablation rate on liquid-film thickness and chemical composition is also examined. The results indicate that photomechanical effect in the phase explosion of liquid is responsible for the enhanced ablation. The low critical temperature of liquid induces explosive vaporization with localized photoacoustic excitation in the superheat limit and increases the ablation efficiency. Experiments were carried out utilizing a Q-swiched Nd:YAG laser at near-threshold laser fluences with negligible plasma effect (up to ∼100 MW/cm$^2$).

• 한국결정성장학회지
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• 제22권3호
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• pp.134-138
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• 2012

Recently the preparation magnetic nanoparticles by a pulsed laser ablation in liquid has gained much attention because it is easy to control experimental parameters. Iron oxide magnetic nanoparticles have been prepared by a pulsed laser ablation of ${\alpha}-Fe_2O_3$ target in ethanol at different magnitude of laser energy of 1, 20, 40 and 80 mJ/pulse. It revealed that particle size increases with increasing laser energy. It could be concluded that 40 mJ/pulse is an optimum laser energy for the preparation of iron oxide nanoparticles with uniform size distribution. The nanoparticles are homogeneously dispersed in ethanol and their stability maintained for several months.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 추계학술발표대회
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• pp.6.2-6.2
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• 2009

Nanostructured materials arecurrently receiving much attention because of their unique structural andphysical properties. Research has been stimulated by the envisagedapplications for this new class of materials in electronics, optics, catalysisand magnetic storage since the properties derived from nanometer-scalematerials are not present in either isolated molecules or micrometer-scalesolids. This study presents the experimental results derived fromthe various functional materials processed in nano-scale using pulsed laserablation, since those materials exhibit new physical phenomena caused by thereduction dimensionality. This presentation consists of three mainparts to consider in pulsed laser ablation (PLA) technique; first nanocrystallinefilms, second, nanocolloidal particles in liquid, and third, nanocoating fororganic/inorganic hybridization. Firstly, nanocrystalline films weresynthesized by pulsed laser deposition at various Ar gas pressures withoutsubstrate heating and/or post annealing treatments. From the controlof processng parameters, nanocystalline films of complex oxides and non-oxidematerials have been successfully fabricated. The excellentcapability of pulsed laser ablation for reactive deposition and its ability totransfer the original stoichiometry of the bulk target to the deposited filmsmakes it suitable for the fabrication of various functionalmaterials. Then, pulsed laser ablation in liquid has attracted muchattention as a new technique to prepare nanocolloidal particles. Inthis work, we represent a novel synthetic approach to directly producehighly-dispersed fluorescent colloidal nanoparticles using the PLA from ceramicbulk target in liquid phase without any surfactant. Furthermore, novel methodbased on simultaneous motion tracking of several individual nanoparticles isproposed for the convenient determination of nanoparticle sizedistributions. Finally, we report that the GaAs nanocrystals issynthesized successfully on the surface of PMMA (polymethylmethacrylate)microspheres by modified PLD technique using a particle fluidizationunit. The characteristics of the laser deposited GaAs nanocrytalswere then investigated. It should be noted that this is the first successfultrial to apply the PLD process nanocrystals on spherical polymermatrices. The present process is found to be a promising method fororganic/inorganic hybridization.

• 한국결정성장학회지
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• 제24권5호
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• pp.219-223
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• 2014

Pulsed laser ablation in liquid medium was successfully employed to synthesize hydroxyapatite colloidal nanoparticles. The crystalline phase, particle morphology, size distribution and microstructure of the hydroxyapatite nanoparticles were investigated in detail. The obtained hydroxyapatite nanoparticles had spherical shape with sizes ranging from 5 to 20 nm. The laser ablation and the nanoparticle forming process were discussed with explosive ejection mechanism by investigating change of surface morphology on target. The analytical results of XPS, FT-IR and Raman spectroscopy confirms that the stoichiometry and bonding properties of the hydroxyapatite nanoparticles are in good agreement with reported bulk hydroxyapatite materials.

• 한국산업융합학회 논문집
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• 제22권3호
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• pp.243-250
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• 2019

The nanosecond laser assisted ablation have been investigated. The biocompatable polymer PMMA was employed as the target material and the two distinctive surface conditions were test. The first surface condition is a dry surface for which the target surface is exposed to air and the second surface condition is the wet surface for which the target surface is covered with dehydrated water. The ablation volume, the laser induced acoustic wave, the laser induced plasma were investigated for both wet and dry condition. The nanosecond laser pulse ablatied more on the wet surface compared to the dry surface. The enhanced ablation of wet surface is attributed to the confined acoustic wave and the laser-induced plasma in the liquid layer.

• 한국결정성장학회지
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• 제24권3호
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• pp.111-119
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• 2014

A novel pulsed laser ablation process in liquid was investigated to prepare scheelite-type ceramic [calcium tungstate ($CaWO_4$) and calcium molybdate ($CaMoO_4$)] nanocolloidal particles. The crystalline phase, particle morphology, particle size distribution, absorbance and optical band-gap were investigated. Stable colloidal suspensions consisting of well-dispersed $CaWO_4$ and $CaMoO_4$ nanoparticles with narrow size distribution could be obtained without any surfactant. Particle tracking analysis using optical microscope combined with image analysis was applied for a fast determination of particle size distribution in the prepared nanocolloidal suspensions. The mean nanoparticle size of $CaWO_4$ and $CaMoO_4$ colloidal nanoparticles were 16 nm and 30 nm, with the standard deviations of 2.1 and 5.2 nm, respectively. The optical absorption edges showed blue-shifted values about 60~70 nm than those of reported in bulk crystals. And also, the estimated optical energy band-gaps of $CaWO_4$ and $CaMoO_4$ colloidal particles were 5.2 and 4.7 eV. The observed band-gap widening and blue-shift of the optical absorbance could be ascribed to the quantum confinement effect due to the very small size of the $CaWO_4$ and $CaMoO_4$ nanocolloidal particles prepared by pulsed laser ablation in liquid.

• Bulletin of the Korean Chemical Society
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• 제34권12호
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• pp.3909-3911
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• 2013

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

• 전기화학회지
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• 제15권4호
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• pp.236-241
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• 2012

일반적으로 그라파이트는 높은 결정성으로 인해 나노입자상으로 제조하기 어려우며 특히 표면에 친수성을 부여하기가 쉽지 않은 재료로 알려져 왔다. 본 연구에서는 박막 증착에 널리 활용되어 오던 펄스 레이저 어블레이션 기법을 액상에 적용하여 친수성이 부여된 그라파이트 나노입자를 합성하였다. 타겟으로는 그라파이트 로드를 사용하였으며 레이저 출력을 조절하며 액상에서 어블레이션을 실시한 결과 매우 높은 분산 안정성을 갖는 친수성 그라파이트 나노입자를 합성할 수 있었다. FT-IR 분석결과 합성된 친수성 그라파이트 나노입자는 카르복시기 및 카르보닐기 등이 나노입자의 형성과 동시에 표면에 도입된 것이 밝혀졌으며 이는 제타 포텐셜로도 확인할 수 있었다. 최종적으로 Polyethyleneglycol(PEG)과 컴포지트하여 아세톤 센서에 적용한 결과 기존의 카본 블랙 대비 우수한 감도를 나타내었다.

• 한국결정성장학회지
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• 제32권2호
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• pp.77-82
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• 2022

고효율의 수전해 촉매는 낮은 전압에서 빠른 속도로 산화반응이 가능하기에 반응 활성이 높은 촉매설계 및 제조 공정이 필요하다. 현재 귀금속 촉매가 산소 발생 반응 성능에 있어서 우수한 특성을 보여주고 있지만 높은 가격과 낮은 반응성에 의한 효율 한계성으로 인해 상용화에 큰 어려움을 겪고 있다. 최근 귀금속 촉매를 대체하기 위해 저비용/고효율 수전해 촉매 개발연구가 활발하게 진행되고 있는데, 본 연구에서는 가격적인 측면에서 부담이 적고 산소활성 반응이 뛰어난 니켈 금속과 전기전도성이 뛰어난 multi walled carbon nanotube(MWCNT)를 이용하고 pulsed laser ablation in Liquid(PLAL) 공정을 적용하여 MWCNT 구조내에 Ni 을 성공적으로 dopping하여 Ni-MWCNT 촉매를 제작하고자 하였다. High resolution-transmission electron microscopy(HR-TEM) 분석 및 X-ray photoelectron spectroscopy(XPS) 분석을 통하여 개발된 수전해 촉매의 구조 및 화학적 조성을 확인하였으며, 촉매 산소발생반응 평가는 선형 주사 전위법(Linear sweep voltammetry; LSV) 과전압 특성, 타펠 기울기(Tafel slope), 전기화학 임피던스 분광법(Electrochemical impedance spectroscopy; EIS), 순환 전압 전류법(Cyclic voltammetry; CV) 및 Chronoamperometry(CA) 측정법으로 진행하였다.