• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.24-24
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• 2007

Aerosol deposition(AD) method is a emerging technology for the room temperature deposition of the dielectric thin films with high quality. In this study, $Al_2O_3$ thin films were deposited by aerosol deposition method directly from raw powders. To get uniform and smooth film surface, Process parameters such as gas consumption rate, nozzle-substrate distance and vibration speed were optimized. From XRD results, $Al_2O_3$ thin films have the same crystal structures with starting powders. $Al_2O_3$ thin films also showed dense microstructure. Electrical properties of the thin films were also investigated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.667-670
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• 2000

The electrochemical characterization was conducted by the addition of chemically synthesized polyaniline on LiCoO$_2$electrode. From the results of XRD and SEM, the phase transition and microstructure were not found. Initial electrochemical characteristics of LiCoO$_2$electrode for lithium secondary battery were evaluated through the charge/discharge within the range of 4.3 V to 3.0 V versus Li/Li$^{+}$. Discharge capacity of LiCoO$_2$electrode without addition of Polyaniline were 160.21 mAh/g. But after addition of polyaniline, lower discharge capacities 25.7 mAh/g was found.d.

• Korean Journal of Materials Research
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• v.6 no.11
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• pp.1090-1098
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• 1996

개조한 가스 금속 아아크 용접공정을 이용하여 SiC/AI 금속기 복합재료를 제조하고 그 특성을 조사하였다. AI 모재위에 강화입자의 크기와 부피분율을 변화하여 다양한 SiC/AI 복합재료층을 제조하였고, 만들어진 복합재료층의 특성은 미세조직관찰과 미소경도시험을 통하여 이루어졌다. 복합재료층의 두께는 약 7-8mm로 측정되었고 균일한 강화입자의 분포도를 얻을 수 있었다. 분산입자의 부피분률은 Ar가스의 유량에 의하여 조절하였고 분산입자의 부피분률이 증가하고 크기가 작아짐에 따라 기지의 수지상 응고조직은 더욱 미세화되었다. 복합재료의 부피경도는 분산입자의 부피분률이 감소함에 따라 낮아졌으나 입자 크기에는 크게 변화가 없는 것으로 나타났다.

• Journal of the Korean Physical Society
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• v.73 no.12
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• pp.1867-1872
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• 2018

This study proposes a route for surface modification for p-type cobalt oxide-based gas sensors. We deposit a thin layer of Ni on the Co oxide film by sputtering process and annealed at $350^{\circ}C$ for 15 min in air, which changes a typical sputtered film surface into one interlaced with a high density of hemispherical nanoparticles. Our in-depth materials characterization using transmission electron microscopy discloses that the microstructure evolution is the result of an extensive inter-diffusion of Co and Ni, and that the nanoparticles are nickel oxide dissolving some Co. Sensor performance measurement unfolds that the surface modification results in a significant sensitivity enhancement, nearly 200% increase for toluene (at $250^{\circ}C$) and CO (at $200^{\circ}C$) gases in comparison with the undoped samples.

• Korean Journal of Metals and Materials
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• v.50 no.12
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• pp.867-871
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• 2012

The microstructure and texture of TiN coatings on a Ni-based super-alloy were characterized by the automated version of electron backscatter diffraction (EBSD), EBSD techniques were used to investigate the very fine TiN grain shape and crystal orientation. This study confirmed that EBSD techniques provide a very useful tool for characterization of coating materials. The TiN grains had a special texture, a {001}-fiber texture in the coating layer. It was also found that, in severe environments, the coating performance of equiaxial and randomly oriented TiN is superior to that with columnar structures.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.5
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• pp.239-245
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• 2022

The purpose of this study is to evaluate the degree of microstructural change of materials using ultrasonic nonlinear parameters. For microstructure change, isothermal heat-treated ferritic 2.25Cr steel and low-cycle fatigue-damage copper alloy were prepared. The variation in ultrasonic nonlinearity was analyzed and evaluated through changes in hardness, ductile-brittle transition temperature, electron microscopy, and X-ray diffraction tests. Ultrasonic nonlinearity of 2.25Cr steel increased rapidly during the first 1,000 hours of deterioration and then gradually increased thereafter. The variation in non-linear parameters was shown to be coarsening of carbides and an increase in the volume fraction of stable M6C carbides during heat treatment. Due to the low-cycle fatigue deformation of oxygen-free copper, the dislocation that causes lattice deformation developed in the material, distorting the propagating ultrasonic waves, and causing an increase in the ultrasonic nonlinear parameters.

• Journal of Surface Science and Engineering
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• v.55 no.2
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• pp.77-83
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• 2022

Nanocrystalline MoN coatings were prepared by inductively coupled plasma magnetron sputtering (ICPMS) changing the plasma power from 0 W to 200 W. The properties of the coatings were analyzed by x-ray diffraction, field emission scanning electron microscopy, atomic force microscopy, nanoindentation tester and semiconductor characterization system. As the ICP power increases, the crystal structure of the MoN coatings changed from a mixed phase of γ-Mo₂N and α-Mo to a single phase γ-Mo₂N. MoN coatings deposited by ICPMS at 200 W showed the most compact microstructure with the highest nanoindentation hardness of 27.1 GPa. The electrical resistivity of the coatings decreased from 691.6 μΩ cm to 325.9 μΩ cm as the ICP power increased.

• Advances in nano research
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• v.13 no.5
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• pp.437-451
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• 2022

Synthesis approaches usually affect the physical and chemical properties of ferrites. This helps ferrite materials to design them for desired applications. Some of these methods are mechanical milling, ultrasonic method, micro-emulsion, co-precipitation, thermal decomposition, hydrothermal, microwave-assisted, sol-gel, etc. These methods are extensively reviewed by taking example of ZnFe₂O₄. These methods also affect the microstructure and local structure of ferrite which ultimately affect the physical and chemical properties of ferrites. Various spectroscopic techniques such as Raman spectroscopy, Fourier Transform Infrared spectroscopy, Ultra Violet-Visible spectroscopy, Mossbauer spectroscopy, extended x-ray absorption fine structure, and electron paramagnetic resonance are found helpful to reveal this information. Hence, the basic principle and the usefulness of these techniques to find out appropriate information in ZnFe₂O₄ nanoparticles is elaborated in this review.

• Journal of Powder Materials
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• v.31 no.4
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• pp.336-341
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• 2024

Molybdenum, valued for its high melting point and exceptional physical and chemical properties, is studied in diverse fields such as electronics, petrochemicals, and aviation. Among molybdenum oxides, molybdenum dioxide stands out for its higher electrical conductivity than other transition metal oxides due to its structural characteristics, exhibiting metallic properties. It is applied as pellets to gas sensors, semiconductors, and secondary batteries for its properties. Thus, research on molybdenum dioxide compaction and pressureless sintering is necessary, yet research on pressureless sintering is currently insufficient. This study synthesized MoO₃ powder via solution combustion synthesis and reduced it using the 3% hydrogen/argon gas mixture to investigate the effect of reduction temperature on the powder. Additionally, the reduced powder was compacted and subjected to pressureless sintering with temperature as a variable. The density and the microstructure of brown parts were analyzed and discussed.

• Journal of the Korean Ceramic Society
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• v.49 no.5
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• pp.438-441
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• 2012

Abalone shell is a high strength and light weighted ceramic composite material, which is composed of $CaCO_3$ platelet and protein. Microstructure of abalone shell has a matrix structure that is similar to the bricks and mortar. The technology inspired from nature which consumes low energy at low temperature is called bioinspired technology. In this study, to make high strength and light weighted ceramic composite materials using bioinspired technology, porous green body was prepared with $Al_2O_3$ platelet. PMMA was infiltrated into the porous green body, then warm pressed to eliminate pores present in the composite. The microstructure of the composite was observed with FESEM, and the mechanical/thermal properties were measured.