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$MgB_2$ bulk의 미세구조와 임계전류밀도에 미치는 polyacrylic acid doping 효과
이승묵,황수민,이창민,주진호,김찬중,Lee, S.M.,Hwang, S.M.,Lee, C.M.,Joo, J.,Kim, C.J. 한국초전도학회 2010 Progress in superconductivity Vol.11 No.2
We fabricated the polyacrylic acid (PAA)-doped $MgB_2$ bulks and characterized their lattice parameters, actual C substitutions, microstructures, and critical properties. The boron (B) powder was mixed with PAA using N,N-dimethylformamide as solvent and then the solution was dried out at $200^{\circ}C$ and crushed. The C treated B powder and magnesium powder were mixed and compacted by uniaxial pressing at 500 MPa, followed by sintering at $900^{\circ}C$ for 1 h in high purity Ar atmosphere. We observed that the PAA doping increased the MgO amount but decreased the grain size, a-axis lattice constant, and critical temperature ($T_c$), which is indicative of the C substitution for B sites in $MgB_2$. In addition, the critical current density ($J_c$) at high magnetic field was significantly improved with increasing PAA addition: at 5 K and 6.6 T, the $J_c$ of 7 wt% PAA-doped sample was $6.39\;{\times}\;10^3\;A/cm^2$ which was approximately 6-fold higher than that of the pure sample ($1.04\;{\times}\;10^3\;A/cm^2$). This improvement was probably due to the C substitution and the refinement of grain size by PAA doping, suggesting that PAA is an effective dopant in improving $J_c$(B) performance of $MgB_2$.
김재형(J.H. Kim),신대용(D.Y. Shin),신동우(D.W. Shin),이정희(J.H. Lee),김찬중(C.J Kim) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.5
In case that there is no large test facility for the operation test of pressure relief valve in nuclear power plant, there is no experimental method to get the operation parameter such as the change of lift and thrust, the dead time, the stroke time, and flow capacity. In this study, the analysis of operation parameter was performed with the mathematical model. The mathematical model was made by combine computational fluid dynamics and multi-body dynamic, which leads to accurate mathematical model. This analysis result can be used in the functional qualification of pressure relief valve in nuclear power plant.