• Transactions of Materials Processing
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• v.13 no.3
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• pp.242-247
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• 2004

Literature review on reliability test method for developing high performance optical/thermofluidic components. Since the miniaturization by the conventional mechanical process is limited to milli-structure, i.e. $10^{-3}m$, new technology for fabricating of mechanical components is needed to match cost, reliability, and integrability criteria of micro-structure. Although numbers of various researches on MEMS/MOEMS devices and components, including material characterization, design and optimization, system validation, etc., the lack of standards and specifications make the researches and developments difficult. For that reason, this paper is intended to propose the methods of reliability test for measuring the mechanical property of optical/ thermofluidic components.

• Journal of the Korean Ceramic Society
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• v.54 no.6
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• pp.470-477
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• 2017

Ceramic processing to fabricate 3D complex ceramic structures is crucial for structural, energy, environmental, and biomedical applications. A unique process is ceramic stereolithography, which builds ceramic green objects from CAD files from many thin liquid layers of powder in monomer, which are solidified by polymerization with a UV laser, thereby "writing" the design for each slice. This approach directly writes layers in liquid ceramic suspension and allows one to fabricate ceramic parts and products having more accurate, complex geometries and smooth surfaces. In this paper, both UV curable materials and processes are presented. We focus on the basic material principles associated with free radical polymerization and rheological behavior, cure depth and broadening of cured lines, scattering at ceramic interface and their corresponding simulation. The immediate potentials for ceramic AM to change industry fabrication are also highlighted.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1852-1854
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• 2003

In manufacturing processes, various and suitable pulse shapes are required for the purpose of material processing. In order to make various pulse shapes with variable pulse length and high duty cycle, We have fabricated the power supply consisting 6 SCRs and the Pulse Forming Network(PFN) with the precise delay time control. So our control system has three switching circuits, 3 mesh PFN, and simmer circuit. In addition, we have designed and fabricated the PIC one-chip microprocessor(16F877) to control the delay time of sequential switching.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.10
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• pp.4392-4397
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• 2012

In this study, we used the commercial package (Unigraphics) to construct a junction box cable car when laser plastic parts have been processed using urethane resin(TSR-755) as a starting mold material. After construction, we carried out the filing, packing, cooling, and deforming analyzation using Injection Molding Analysis (Simpoe-Mold) to determine the gate positioning and automatic cooling cycle through the examination. The results show that inserting into the injection mold after processing ceramic has reduced the time of thermal conductivity of molding and cooling; and quick selection of gates and cooling lines could possibly cause an improvement of productivity.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.4
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• pp.569-577
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• 2018

In this paper, with the aid of information which is included within data, preprocessing algorithm-based black plastic classifier is designed. The slope and area of spectrum obtained by using laser induced breakdown spectroscopy(LIBS) are analyzed for each material and its ensuing information is applied as the input data of the proposed classifier. The slope is represented by the rate of change of wavelength and intensity. Also, the area is calculated by the wavelength of the spectrum peak where the material property of chemical elements such as carbon and hydrogen appears. Using informations such as slope and area, input data of the proposed classifier is constructed. In the preprocessing part of the classifier, Principal Component Analysis(PCA) and fuzzy transform are used for dimensional reduction from high dimensional input variables to low dimensional input variables. Characteristic analysis of the materials as well as the processing speed of the classifier is improved. In the condition part, FCM clustering is applied and linear function is used as connection weight in the conclusion part. By means of Particle Swarm Optimization(PSO), parameters such as the number of clusters, fuzzification coefficient and the number of input variables are optimized. To demonstrate the superiority of classification performance, classification rate is compared by using WEKA 3.8 data mining software which contains various classifiers such as Naivebayes, SVM and Multilayer perceptron.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.790-793
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• 2000

We have fabricated good quality superconducting YBa$_2$Cu$_3$$O_{7-x}$(YBCO) thin films on Hastelloy(Ni-Cr-Mo alloys) metallic substrates with CeO$_2$and BaTiO$_3$buffer layers in-situ by pulsed laser deposition in a multi-target processing chamber. YBCO film with CeO$_2$ single buffer layer shows T$_{c}$ of 71.64 K and the grain size less than 0.1 ${\mu}{\textrm}{m}$. When BaTiO$_3$is used as a single buffer layer, the grain size of YBCO is observed to be larger than that of YBCO/CeO$_2$by 200 times and the transition temperature of the film is enhanced to be about 84 K. CeO$_2$/BaTiO$_3$double buffer layer has been adopted to enhance the superconducting properties, which results in the enhancement of the critical temperature and the critical current density to be about 85 K and 8.4 $\times$ 10$^4$ A/cm$^2$ at 77 K, respectively mainly due to the enlargement of the grain size of YBCO film.ilm.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.11
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• pp.959-962
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• 2000

We have fabricated good quality superconducting YBa$_2$Cu$_3$$O_{7-x}$(YBCO) thin films on Hastelloy(Ni-Cr-Mo alloys) metallic substrates with CeO$_2$and BaTiO$_3$buffer layers in-situ by pulsed laser deposition in a multi-target processing chamber. YBCO film with CeO$_2$single buffer layer shows T$_{c}$ of 71.64 K and the grain size less than 0.1${\mu}{\textrm}{m}$. When BaTiO$_3$ is used as a single buffer layer, the grain size of YBCO is observed to be larger than that of YBCO/CeO$_2$by 200 times and the transition temperature of the film is enhanced to be about 84 K. CeO$_2$/BaTiO$_3$double buffer layer has been adopted to enhance the superconducting properties, which results in the enhancement of the critical temperature and the critical current density to be about 85 K and 8.4$\times$10$^4$ A/$\textrm{cm}^2$ at 77 K, respectively mainly due to the enlargement of the grain size of YBCO film.ilm.

• Transactions of Materials Processing
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• v.28 no.5
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• pp.239-246
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• 2019

Various surface texturing techniques have been studied because of the effective applicability of micro or nano scale surface patterns. Particularly, the most promising types of patterns include the hierarchical patterns, which consists of micro/nano structures. Different processes such as MEMS, laser machining, micro cutting and micro grinding have been applied in the production of hierarchical patterns on various material surfaces. This study demonstrates the process of hot imprinting to induce the hierarchical patterns on the Al alloy surfaces. Wire electrical discharge machining (WEDM) process was used to imprint molds with micro scale sinusoidal pattern. In addition, the sinusoidal pattern with rough surface morphology was obtained as a result of the discharge craters. Consequently, the hierarchical patterns consisting of the sinusoidal pattern and the discharge craters were prepared on the imprinting mold surface. Hot imprinting process for the Al plates was conducted on the prepared mold, and the replication performance was analyzed. As a result, it was confirmed that the hierarchical patterns of the mold were effectively duplicated on the surface of Al plate.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.203-206
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• 2004

For the realization of PRAM, $Ge_2Sb_2Te_5$ (GST) has been employed for the phase transition between the crystal and amorphous states by electrical joule heating. Although there has been a vast amount of results concerning the GST in material aspect for the laser-induced optical storage disc applications, the process-related issues of GST for the PRAM applications have not been reported. In this work, the etching behaviors of GST were investigated when the processing conditions were varied in the high-density helicon plasma. The etching parameters of RF main power, RF bias power, and chamber pressure were fixed at 600 W, 150 W, and 5 mTorr, respectively. For the etching processes, gas mixtures of $Ar/Cl_2$, $Ar/CF_4$, and $Ar/CHF_3$ were employed, in which the etching rates and etching selectivities of GST thin film in given gas mixtures were evaluated. From obtained results, it is found that we can arbitrarily design the etching process according to given cell structures and material combinations for PRAM cell fabrications.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.280-284
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• 2004

Multicrystalline silicon wafers were textured in an alkaline bath, basically using sodium hydroxide and in acidic bath, using mainly hydrofluoric acid (HF), nitric acid $(HNO_3)$ and de-ionized water (DIW). Some wafers were also acid polished for the comparative study. Comparison of average reflectance of the samples treated with the new recipe of acidic solution showed average diffuse reflectance less than even 5 percent in the optimized condition. Solar cells were thus fabricated with the samples following the main steps such as phosphorus doping for emitter layer formation, silicon nitride deposition for anti-reflection coating by plasma enhanced chemical vapor deposition (PECVD) and front surface passivation, screen printing metallization, co-firing in rapid thermal processing (RTP) Furnace and laser edge isolation and confirmed >14 % conversion efficiency from the best textured samples. This isotropic texturing approach can be instrumental to achieve high efficiency in mass production using relatively low cost silicon wafers as starting material.