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A review on the joining of SiC for high‑temperature applications
Dang‑Hyok Yoon,Ivar E. Reimanis 한국세라믹학회 2020 한국세라믹학회지 Vol.57 No.3
A review on the joining of SiC is given in response to the interest surge on this material for a number of applications. Because the engineering design for the majority of applications requires complicated shapes, there has been a strong demand for the development of reliable joining techniques for SiC, especially for high-temperature applications. However, the joining of SiC-based materials is inherently difficult because of the high degree of covalent bonding in SiC and the low self-diffusivity. This review discusses basic mechanisms and properties of the SiC joining techniques developed to date; they are divided into eight different categories. In addition, critical assessment is given for each technique in the context of high-temperature application (≥ 1000 °C). Finally, comments are provided for the use of these techniques in advanced nuclear reactors where stringent irradiation stability under neutron irradiation as well as hermeticity and joint strength are required.
BaTiO3 properties and powder characteristics for ceramic capacitors
Dang-Hyok Yoon,BurtrandI.Lee 한양대학교 세라믹연구소 2002 Journal of Ceramic Processing Research Vol.3 No.2
Barium titanate (BaTiO3) is one of the most widely used ceramic raw materials in the electro-ceramic industry, especially in multi-layer ceramic capacitors (MLCCs). In this paper recent information on basic dielectric properties, the effect of particle size on phase transition, and powder characteristics resulting from various synthetic methods of producing BaTiO3, including the hydrothermal method are reviewed.
Fitriani, Pipit,Yoon, Dang-Hyok,Sharma, Amit Siddharth Elsevier 2017 CERAMICS INTERNATIONAL Vol.43 No.16
<P><B>Abstract</B></P> <P>This study examined the effects of post-sintering heat treatment on enhancing the toughness of SiC<SUB>f</SUB>/SiC composites. Commercially available Tyranno<SUP>®</SUP> SiC fabrics with contiguous dual ‘PyC (inner)-SiC (outer)’ coatings deposited on the SiC fibers were infiltrated with a SiC + 10wt% Al<SUB>2</SUB>O<SUB>3</SUB>-Y<SUB>2</SUB>O<SUB>3</SUB> slurry by electrophoretic deposition. SiC green tapes were stacked between the slurry-infiltrated fabrics to control the matrix volume fraction. Densification of approximately 94% ρ<SUB>theo</SUB> was achieved by hot pressing at 1750°C, 20MPa for 2h in an Ar atmosphere. Sintered composites were then subjected to isothermal annealing treatment at 1100, 1250, 1350, and 1750°C for 5h in Ar. The correlation between the flexural behavior and microstructure was explained in terms of the in situ-toughened matrix, phase evolution in the sintering additive, role of dual interphases and observed fracture mechanisms. Extensive fractography analysis revealed interfacial debonding at the hybrid interfaces and matrix cracking as the key fracture modes, which were responsible for the toughening behavior in the annealed SiC<SUB>f</SUB>/SiC composites.</P>
Fitriani, Pipit,Yoon, Dang-Hyok Elsevier 2018 CERAMICS INTERNATIONAL Vol.44 No.18
<P><B>Abstract</B></P> <P>This study examined the joining of SiC fiber-reinforced SiC matrix composites (SiC<SUB>f</SUB>/SiC) using a Ti<SUB>3</SUB>AlC<SUB>2</SUB> MAX phase filler and the possibility of eliminating the joining layer via solid-state diffusion upon the decomposition of Ti<SUB>3</SUB>AlC<SUB>2</SUB>. The base SiC<SUB>f</SUB>/SiC was fabricated by electrophoretic deposition (EPD) combined with hot pressing after adding a 10 wt% Al<SUB>2</SUB>O<SUB>3</SUB>-Y<SUB>2</SUB>O<SUB>3</SUB> sintering additive. Two types of base SiC<SUB>f</SUB>/SiC with a density of 93% and 96% were prepared by hot pressing at 1750 °C without and with SiC tape insertion, respectively, followed by joining at 1700 or 1900 °C for 5 h under 3.5 MPa in an Ar atmosphere. The SiC<SUB>f</SUB>/SiC with tape insertion showed feasible elimination of the joining layer after joining at 1900 °C, whereas the composite joined at 1700 °C revealed the presence of a joining filler due to incomplete decomposition of the Ti<SUB>3</SUB>AlC<SUB>2</SUB> filler. All samples showed fracturing at the joining interface during the flexural test, showing a joining strength of 180–255 MPa depending on the preparation conditions. The properties of the SiC<SUB>f</SUB>/SiC joints were explained by the surface roughness, microstructure, and phase evolution upon decomposition of the Ti<SUB>3</SUB>AlC<SUB>2</SUB> filler.</P>
Sintering additives for SiC based on the reactivity: A review
Raju, Kati,Yoon, Dang-Hyok Elsevier 2016 CERAMICS INTERNATIONAL Vol.42 No.16
<P><B>Abstract</B></P> <P>Silicon carbide (SiC) is one of the most attractive materials for high temperature applications, being used in many areas, such as gas turbines, heat exchangers, and space shuttles, because of its excellent strength, oxidation resistance and chemical stability at high temperatures. Moreover, SiC and its composites are being considered as structural materials for advanced fission reactors and future fusion reactors owing to its additional low induced radioactivity under neutron irradiation conditions. On the other hand, pure SiC can only be densified by sintering at high temperatures and pressures because of its high covalent bonding nature and low self-diffusivity. Therefore, the addition of sintering additives is essential for enhancing the densification of SiC. This paper reviews the criteria for the selection of effective SiC sintering additives based on the Gibbs free energy to predict the reactivity between the sintering additive and SiC, particularly for liquid phase sintering at 1700–1900°C. The thermodynamic simulation was verified by offering the experimental results for various types of sintering additives, such as main group metals, metal oxides, and rare earth elements. This review suggests a guideline for the selection of sintering additives for SiC.</P>
Fabrication of Mullite-Bonded Porous SiC Using Ti<sub>3</sub>AlC<sub>2</sub> MAX Phase
Septiadi, Arifin,Yoon, Dang-Hyok The Korean Ceramic Society 2019 한국세라믹학회지 Vol.56 No.2
This study assessed the feasibility of a Ti<sub>3</sub>AlC<sub>2</sub> MAX phase as an Al-source for the formation of a mullite bond in the fabrication of porous SiC tubes with high strength. The as-received Ti<sub>3</sub>AlC<sub>2</sub> was partially oxidized at 1200℃ for 30 min before using to minimize the abrupt volume expansion caused by oxidation during sintering. Thermal treatment at 1100-1400℃ for 3 h in air led to the formation of Al<sub>2</sub>O<sub>3</sub> by the decomposition of Ti<sub>3</sub>AlC<sub>2</sub>, which reacted further with oxidation-derived SiO<sub>2</sub> on the SiC surface to form a mullite phase. The fabricated porous SiC tubes with a relative density of 48 - 62 % exhibited mechanical strengths of 80 - 200 MPa, which were much higher than those with the Al<sub>2</sub>O<sub>3</sub> filler material. The high mechanical strength of the Ti<sub>3</sub>AlC<sub>2</sub>-added porous SiC was explained by the rigid mullite neck formation along with the retained Ti<sub>3</sub>AlC<sub>2</sub> with good mechanical properties.
Optimization of Barium Titanate Slip for Tape Casting Using Design of Experiments
Kwon, Sung-Wook,Darsono, Nono,Yoon, Dang-Hyok The Korean Ceramic Society 2006 한국세라믹학회지 Vol.43 No.9
A full-factorial design of experiments with three input factors and two levels for each factor including center points was utilized for the preparation and characterization of twelve types of $BaTiO_3$ slips for tape casting. Ceramic powders with different particle sizes, different milling methods such as high energy milling and conventional ball milling, and two types of dispersant with different polymeric species were chosen as input factors in order to investigate their effects on slip and on green tape properties. Tape casting, a small rectangular-shaped K-square preparation, characterization and quantitative data analysis using statistical software were followed. Ceramic powder was the most significant among three input factors for the output responses of slip viscosity and green tape density, showing more favorable results with large particles than with very fine ones. In addition, high energy milling for only 30 min was more efficient than 24h of conventional ball milling in terms of powder dispersion and milling. The optimum condition based on the experimental results was a slip exposed to high energy milling with large ceramic particles along with a methylethyl acetate dispersant.
SiC<sub>f</sub>/SiC 복합체의 특성에 미치는 열간가압소결 조건의 영향
노비얀토 알피안,윤당혁,Noviyanto, Alfian,Yoon, Dang-Hyok 한국세라믹학회 2011 한국세라믹학회지 Vol.48 No.5
Continuous SiC fiber-reinforced SiC-matrix composites ($SiC_f$/SiC) had been fabricated by electrophoretic infiltration combined with ultrasonication. Nano-sized ${\beta}$-SiC added with 12 wt% of $Al_2O_3-Y_2O_3$ additive and Tyranno$^{TM}$-SA3 fabric were used as a matrix phase and fiber reinforcement, respectively. After hot pressing at 5 different conditions, the density, microstructure and mechanical properties of $SiC_f$/SiC were characterized. Hot pressing at relatively severe conditions, such as $1750^{\circ}C$ for 1 and 2 h, resulted in a brittle fracture behavior due to the strong fiber-matrix interface in spite of their high flexural strength. On the other hand, toughened $SiC_f$/SiC composite could be achieved by hot pressing at milder condition because of the formation of weak interface in spite of the decreased flexural strength. These results proposed the importance of weak fiber-matrix interface in the fabrication of ductile $SiC_f$/SiC composite.