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Cho, Seungchan,Okayasu, Rin,Kikuchi, Keiko,Choi, Moonhee,Park, Jehong,Jo, Ilguk,Lee, Sang-Bok,Kwon, Hansang,Kim, Yangdo,Miyazaki, Takamichi,Kawasaki, Akira Elsevier 2019 Scripta materialia Vol.159 No.-
<P><B>Abstract</B></P> <P>We successfully fabricated a controllable intragranular pore containing hydroxyapatite (HA) by the combination of an electric current assisted sintering and pre-heat treatment process. The microstructure and mechanical properties of the sintered HA bulk with and without intragranular pores were investigated in this study. Fully densified HA fabricated by the combination of an electric assisted sintering and pre-heat treatment process showed extremely superior mechanical properties. Meanwhile, hierarchically structured porous HA consisting of nanosized intragranular pores without macropores in the grain boundary showed dramatically decreased elastic modulus by different fracture mechanism compared with fully densified HA.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Cho, Seungchan,Kikuchi, Keiko,Kawasaki, Akira,Kwon, Hansang,Kim, Yangdo IOP Pub 2012 Nanotechnology Vol.23 No.31
<P>Multi-walled carbon nanotube (MWCNT) reinforced copper (Cu) matrix composites, which exhibit chromium (Cr) carbide nanostructures at the MWCNT/Cu interface, were prepared through a carbide formation using CuCr alloy powder. The fully densified and oriented MWCNTs dispersed throughout the composites were prepared using spark plasma sintering (SPS) followed by hot extrusion. The tensile strengths of the MWCNT/CuCr composites increased with increasing MWCNTs content, while the tensile strength of MWCNT/Cu composite decreased from that of monolithic Cu. The enhanced tensile strength of the MWCNT/CuCr composites is a result of possible load-transfer mechanisms of the interfacial Cr carbide nanostructures. The multi-wall failure of MWCNTs observed in the fracture surface of the MWCNT/CuCr composites indicates an improvement in the load-bearing capacity of the MWCNTs. This result shows that the Cr carbide nanostructures effectively transferred the tensile load to the MWCNTs during fracture through carbide nanostructure formation in the MWCNT/Cu composite. </P>
Cho, Seungchan,Jo, Ilguk,Lee, Yeong-Hwan,Yoo, Yeon Woo,Byon, Eungsun,Lee, Sang-Kwan,Lee, Sang-Bok Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.448 No.-
<P><B>Abstract</B></P> <P>Oxidation resistance of TiC–SKD11 composite has been improved through SiC/TiB<SUB>2</SUB> based hybrid coating by a simple air spray process and subsequent transition to dense and stable phases in oxidation environment. As a result of the oxidation test at 700 °C for up to 50 h, the coated TiC–SKD11 composite exhibited excellent oxidation resistance characteristics compared with the uncoated TiC–SKD11 composite, and also compared to SUS431 and 17-4PH. The formation of a thermally stable, volume-expanded SiO<SUB>2</SUB> and TiO<SUB>2</SUB> coating layer with the aid of B<SUB>2</SUB>O<SUB>3</SUB> by phase transition of TiB<SUB>2</SUB>/SiC based hybrid coating under oxidation atmosphere is the origin of the improved anti-oxidation ability of the TiC–SKD11 composite.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A SiC/TiB<SUB>2</SUB> based hybrid coating layer was successfully deposited on the surface of TiC–SKD11 composite by simple air spray process. </LI> <LI> The anti-oxidation ability was found to be much better than that of the uncoated TiC–SKD11 composite, as well as better than those of SUS431 and 17-4PH. </LI> <LI> The formation of SiO<SUB>2</SUB> and TiO<SUB>2</SUB> layer with the aid of B<SUB>2</SUB>O<SUB>3</SUB> by phase transition of SiC/TiB<SUB>2</SUB> based hybrid coating is the origin of the improved anti-oxidation ability of the TiC–SKD11 composite. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Cho, Seungchan,Lee, Yeong-Hwan,Ko, Sungmin,Park, Hyeonjae,Lee, Donghyun,Shin, Sangmin,Jo, Ilguk,Kim, Yangdo,Lee, Sang-Bok,Lee, Sang-Kwan Elsevier 2020 JOURNAL OF ALLOYS AND COMPOUNDS Vol.817 No.-
<P><B>Abstract</B></P> <P>High-temperature compressive strengths of titanium carbide (TiC) reinforced stainless steel composites fabricated by liquid pressing infiltration process were investigated at various temperatures. Effect of TiC on compressive strength of SUS431 was found to increase with increasing testing temperature. TiC reinforcement successfully suppressed softening of SUS431 matrix, resulting in about 5 times higher strength than that of SUS431 at 1050 °C. The novel SUS431 composites reinforced with uniformly dispersed, high volume fraction TiC show great promise for applications in high-temperature environments.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Fabrication of lightweight, high strength TiC–SUS431 composites using a novel infiltration process. </LI> <LI> Improvements in high-temperature compressive strengths of about 2.6–5.1 times compared to those of the SUS431 alloy. </LI> <LI> TiC cleavage fracture with no interfacial debonding between TiC and the steel matrix. </LI> <LI> Increased ductility of the composite at about 1050 °C. </LI> <LI> 54% higher compressive strength than that of Rene95 superalloy at 1050 °C. </LI> </UL> </P>
용융가압함침 공정으로 제조한 TiC-SKD11 복합재료의 미세조직 및 내마모 특성
조승찬 ( Seungchan Cho ),조일국 ( Ilguk Jo ),이상관 ( Sang-kwan Lee ),이상복 ( Sang-bok Lee ) 한국복합재료학회 2017 Composites research Vol.30 No.3
본 연구에서는 용융가압함침 공정을 통해 고체적율의 TiC 입자가 균일 분산된 SKD11 금속복합재료를 제조하고, 미제조직, 기계적 특성 및 내마모 특성에 대해 분석하였다. 약 60 vol%의 TiC가 균일하게 분산된 TiC-SKD11 복합재료를 제조함으로써 SKD11 대비 약 24% 경량화에 성공하였고 경도 및 압축항복강도는 증가하였다. 내마모 시험 결과 복합소재의 우수한 내마모 특성을 확인하였으며, 이는 높은 경도를 가지는 TiC 입자가 SKD11 기지와 강한 계면 결합력을 가지면서 높은 체적율로 존재함으로 인한 분산강화 효과와 TiC에 의한 SKD11의 산화 억제가 원인으로 판단된다. Titanium carbide (TiC) reinforced SKD11 matrix composites were successfully fabricated by a novel liquid pressing infiltration process. Microstructure, mechanical properties, and wear characteristics of the fabricated 60 vol% TiC-SKD11 composite are analyzed. The composite exhibits superior mechanical properties, such as hardness and compressive strength with 24% lower density as compared with SKD11. Improved wear resistance of the TiC-SKD11 composite originates from uniformly reinforced TiC having strong interfacial bonding strength between TiC/ SKD11 interface.
용융가압함침공정을 이용한 세라믹 입자 강화 철강복합재료의 제조성 검증
조승찬 ( Seungchan Cho ),이영환 ( Yeong-hwan Lee ),고성민 ( Seongmin Ko ),박현재 ( Hyeon Jae Park ),이동현 ( Donghyun Lee ),신상민 ( Sangmin Shin ),조일국 ( Ilguk Jo ),이상관 ( Sang-kwan Lee ),이상복 ( Sang-bok Lee ) 한국복합재료학회 2018 Composites research Vol.31 No.4
본 연구에서는 용융가압함침 공정을 이용하여 TiC, TiB<sub>2</sub>, Al<sub>2</sub>O<sub>3</sub> 세라믹 입자가 분산된 SUS431 금속복합재료를 제조하고 미세조직을 분석하여 세라믹 입자에 따른 제조성에 대해 검토하였다. 젖음성이 나쁜 Al<sub>2</sub>O<sub>3</sub>의 경우 내부에 결함이 다수 존재함을 알 수 있었으며, TiB<sub>2</sub> 및 TiC 입자 강화 복합재의 경우 상대적으로 결함이 적고 강화재가 균일 분산되었음을 확인하였다. 특히, TiC-SUS431 복합재료의 경우 TiC와 Fe계 기지합금의 우수한 젖음성 및 용융가압함침공정 적용으로 우수한 계면 특성을 가지며 결함이 적고 균일한 미세조직을 가지는 것을 확인하였다. Various ceramic particulate such as TiC, TiB<sub>2</sub>, Al<sub>2</sub>O<sub>3</sub> reinforced SUS431 matrix composites were successfully fabricated by a novel liquid pressing infiltration process. Microstructures of the SUS431 composite were analyzed to determine manufacturability of composites. Al<sub>2</sub>O<sub>3</sub>-SUS431 composite had lots of defects due to poor wettability between the Al<sub>2</sub>O<sub>3</sub> and steel matrix. On the other hand, TiC was uniformly dispersed in the SUS431 matrix than TiB2 and Al<sub>2</sub>O<sub>3</sub> due to good wettability and interfacial properties.
Kim Jandi,Seo Ji Hye,Lee Sang Heun,Cho Myunghee,Kwak Hun,Cheon Ran Sae,Cho Seungchan,Cho Sung Beom,Kim Minkee,Lee Yoon-Seok,김양도,Choi Moonhee 한국세라믹학회 2024 한국세라믹학회지 Vol.61 No.3
In this study, by replacing the B-site element in BaTiO 3 , a ferroelectric material, with an element with a larger ionic radius, a ferroelectric material with high permittivity at room temperature was synthesized. The powders were prepared by solid-state reaction to perform lattice substitution with Zr 4+ (0.72 Å), which has a larger ionic radius than Ti 4+ (0.605 Å). To perform effective solid-state reaction and better understand the correlation between variables, this study introduced a design of experiment (DOE) based on the orthogonal array (OA) method included in the PIAno software. By substituting 0.222 mol of Zr, which has a large ionic radius, the crystal structure was deformed through an effective diffuse phase transition (DPT), and this resulted in the largest improvement in permittivity at room temperature. In addition, the powder, which underwent solid-state reaction at 1300 °C, formed the densest structure during sintering, which established the conditions for realizing the best dielectric properties. These results can be utilized as a key material for improving the properties of passive devices used in high-voltage industrial systems in societies undergoing the fourth industrial revolution.
Versatile Multilayer Transparent Electrodes for ITO-Free and Flexible Organic Solar Cells
Seungchan Han,Sooyeon Lim,Hoyeon Kim,Hyunsu Cho,Seunghyup Yoo IEEE 2010 IEEE journal of selected topics in quantum electro Vol.16 No.6
<P>Multilayer transparent electrodes based on a dielectric-metal-dielectric structure are explored as an effective alternative to indium tin oxide (ITO) electrodes that can lead to ITO-free or highly flexible organic photovoltaic (OPV) cells with a performance comparable to conventional cells. The role of each layer in multilayer electrodes is discussed with an emphasis on the potential role of inner dielectric layer as a buffer layer, and the optimization strategy considering the overall optical structure is provided. Experimental results showing the OPV performance under dynamic flexibility test are also provided as a function of the number of bending cycles.</P>