• Journal of Welding and Joining
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• v.26 no.4
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• pp.27-33
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• 2008

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.5
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• pp.492-497
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• 2006

The study on laser-ablation plasmas has been strongly interested in fundamental aspects of laser-solid interaction and consequent plasma generation. In particular, this plasma has been widely used for the deposition of thin solid films and applied to the semiconductors and insulators. In this paper, we developed and discussed the generation of carbon ablation plasmas emitted by laser radiation on a solid target, graphite. The progress of carbon plasmas by laser-ablation was simulated using Monte-Carlo particle model under the pressures of vacuum, 1 Pa, 10 Pa and 66 Pa. At the results, carbon particles with low energy were deposited on the substrate as the pressure becomes higher However, there was no difference of deposition distributions of carbon particles on the substrate regardless of the pressure.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.11
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• pp.832-840
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• 2008

Ablation occurs at irradiance beyond $10^9\;W/cm^2$ with nanosecond and short laser pulses focused onto any materials. Phenomenologically, the surface temperature is instantaneously heated past its vaporization temperature. Before the surface layer is able to vaporize, underlying material will reach its vaporization temperature. Temperature and pressure of the underlying material are raised beyond their critical values, causing the surface to explode. The pressure over the irradiated surface from the recoil of vaporized material can be as high as $10^5\;MPa$. The interaction of high power nanosecond laser with a thin metal in air has been investigated. The nanosecond pulse laser beam in atmosphere generates intensive explosions of the materials. The explosive ejection of materials make the surrounding gas compressed, which form a shock wave that travels at several thousand meters per second. To understand the laser ablation mechanism including the heating and ionization of the metal after lasing, the temporal evolution of shock waves is captured on an ICCD camera through laser flash shadowgraphy. The expansion of shock wave in atmosphere was found to agree with the Sedov's self-similar spherical blast wave solution.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.3
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• pp.56-61
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• 2010

Recently, UV pulse laser is widely used in micro machining of the research, development and industry field of IT, NT and BT products because the laser short wavelength provides not only micro drilling, micro cutting and micro grooving which has a very fine line width, but also high absorption coefficient which allows a lot of type of materials to be machined more easily. To analyze the dynamic deformation during a very short processing time, which is nearly about several tens nanoseconds, the commercial Finite Element Analysis (FEA) code, LS-DYNA 3D, was employed for the computitional simulation of the UV laser micro machining behavior for thin copper material in this paper. A finite element model considering high strain rate effect is especially suggested to investigate the micro phenomena which are only dominated by mechanically pressure impact in disregard of thermally heat transfer. From these computational results, some of dynamic deformation behaviors such as dent deformation shapes, strains and stresses distributions were observed and compared with previous experimental works. These will help us to understand micro interaction between UV laser beam and material.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.1
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• pp.98-105
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• 2008

In this paper, the system for monitoring process of aluminum laser welding was developed using the light signal emitted from the plasma which comes from interaction between material and laser. Photodiode for monitoring system was selected based on the spectrum analysis of light from plasma and keyhole. Behavior of plasma and keyhole was analyzed through the sensor signals. Value of sensor signal represented the light intensity and fluctuation of signal indicated the stability of plasma and keyhole. For the relation between welding condition and sensor signals, the input power and weld geometry greatly effected on the average of each sensor signals. Using the feature values of signals, estimation model for tensile strength of weld was formulated with neural network algorithm. Performance of this model was verified through coefficient of determination and average error rate.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.05a
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• pp.41-45
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• 2006

The study on laser-ablation plasmas has been strongly interested in fundamental aspects of laser-solid interaction and consequent plasma generation. In particular, this plasma has been widely used for the deposition of thin solid films and applied to the semiconductors and insulators. In this paper, we developed and discussed the generation of carbon ablation plasmas emitted by laser radiation on a solid target, graphite. The progress of carbon plasmas by laser-ablation was simulated using Monte-Carlo particle model under the pressures of vacuum, 1 Pa, 10 Pa and 66 Pa. At the results, carbon particles with low energy were deposited on the substrate as the pressure becomes higher. However, there was no difference of deposition distributions of carbon particles on the substrate regardless of the pressure.

• Medical Lasers
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• v.10 no.2
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• pp.76-81
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• 2021

Biological tissues and organs are composed of different arrays of cells, biochemical cues, and extracellular matrices arranged in a complex microarchitecture. Laser-Assisted Bioprinting (LAB) is an emerging and promising technology that is reproducible with high accuracy that can be used for fabricating complex bioengineered scaffolds that mimic tissues and organs. The LAB process allows researchers to print intricate structural scaffolds using cells and different biomaterials essential for facilitating cell-scaffold interaction and to induce tissue and organ regeneration which cannot be achieved in a traditional scaffold fabrication. This process can fabricate artificial cell niches or architecture without affecting cellular viability and material integrity. This review tackles the basic principles and key aspects of Laser-Assisted Bioprinting. Recent advances, limitations, and future perspectives are also discussed.

• Korean Journal of Metals and Materials
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• v.50 no.3
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• pp.191-200
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• 2012

The purpose of this paper is to review the state of laser processing technology using metal powders. In recent years, a series of research and development efforts have been undertaken worldwide to develop laser processing technologies to fabricate metal-based parts. Layered manufacturing by the laser melting process is gaining ground for use in manufacturing rapid prototypes (RP), tools (RT) and functional end products. Selective laser sintering / melting (SLS/SLM) is one of the most rapidly growing rapid prototyping techniques. This is mainly due to the processes's suitability for almost any materials, including polymers, metals, ceramics and many types of composites. The interaction between the laser beam and the powder material used in the laser melting process is one of the dominant phenomena defining feasibility and quality. In the case of SLS, the powder is not fully melted during laser scanning, therefore the SLS-processed parts are not fully dense and have relatively low strength. To overcome this disadvantage, SLM and laser cladding (LC) processes have been used to enable full melting of the powder. Further studies on the laser processing technology will be continued due to the many potential applications that the technology offers.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.3
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• pp.203-213
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• 2023

Owing to carbon materials' diverse functionalization and versatility, the design and synthesis of carbon-based three-dimensional porous structures have become important foundational research topics across various fields. Among the various methods for producing porous carbon structures, laser-induced graphene (LIG) has garnered attention because of its large surface area, controllable structure, excellent electrical conductivity, scalability, and eco-friendly synthesis process. In addition, recent research results have reported more novel functionalities by advancing further from the unique characteristics of LIG through functionalization or compounding of LIG, making it an attractive material for various applications in electronic devices, sensing, catalysis, and energy storage. This review aims to update the research trends in LIG and its functionalization, providing insights to inspire more interesting studies on functional LIG to expand its potential applications ultimately. Starting with the synthesis method and material characteristics of LIG, we introduce the functionalization of LIG, which is classified into surface modification, heteroatom doping, and hybridization based on the interaction mechanism. Finally, we summarize and discuss the prospects of LIG and its functionalization.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.5
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• pp.705-711
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• 2012

The purpose of this study is to develop the model to estimate the penetration rate of metal under a high power continuous wave laser irradiation. To estimate it, an empirical modeling is more practical when the penetration phenomena of metal by laser irradiation is too complex to be analyzed by the numerical simulation. When several methods published earlier were applied to our results, we found out that their methods were not appropriate as the model. Therefore, we suggested the new empirical method considering effective intensity as a key variable. As a result, we confirmed that the new method was effective to model the penetration rate of SUS304 metal and expected that it could be available to other metals.