• Progress in Superconductivity
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• 제13권2호
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• pp.133-138
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• 2011

To reduce the processing cost of the single grain REBCO (RE: Rare-earth elements) bulk superconductors, a cost-effective process should be developed. One possible way of developing the cost-effective process is the use of low-cost precursor powders. In this study, the single grain YBCO superconductors were fabricated using a home made powder. $YBa_2Cu_3O_{7-y}$ (Y123) powders were synthesized at $850-900^{\circ}C$ in air by the powder calcination method with repeated crushing and heat treatment steps. The processing parameters for the fabrication of single grain Y123 bulk superconductors, $T_{max}$ (maximum temperature), $T_p$ (peritectic temperature) and a cooling rate through $T_p$ were optimized. To enhance the flux pinning capacity of the single grain Y123 samples, $Y_2BaCuO_5$ (Y211) particles were dispersed in the Y123 matrix by adding $Y_2O_3$ powder to the calcined Y123 powder. Applying the optimized processing condition, the single grain Y123 superconductors with $T_c=91\;K$ and $J_c=1.5{\times}10^4\;A/cm^2$ at 2 T were successfully fabricated using a home made powder. The levitation forces and trapped magnetic field at 77 K measured using a Nd-B-Fe permanent magnet of 5300 G were 47 N and 3000 G, respectively, which are comparable to those obtained for the samples fabricated using a commercial grade Y123 powders.

• 한국초전도ㆍ저온공학회논문지
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• 제7권1호
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• pp.5-8
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• 2005

MOD Process using metal acetates or trifluoroacetates has been considered to be a strong candidate for a low cost fabrication process for coated conductor with high $J_e$. Recently, an economical MOI) process has been developed for coated conductor with high $J_c$ using low cost starting materials such as YBCO powders. YBCO thin films prepared by single coating on LAO substrate with this modified oxide-precursor solution gives transport $I_c$ of 100A/cm-w and the $J_c$ value of $2.9MA/cm^{2}$ (77K, Self-field). The YBCO coated conductor prepared by single coating with $CeO_2/IBAD-YSZ/SS$ tape gives transport $I_c$ of 50A/cm-w in 2cm. Characterization with XRD, SEM shows that the YBCO layers were epitaxially grown and exhibit well-developed dense micro-structures. This newly developed oxide-precursor based MOD process will provide a low cost route to coated conductor with high $J_c$.

• Progress in Superconductivity
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• 제6권2호
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• pp.142-145
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• 2005

YBCO coated conductors have been fabricated with a newly developed oxide-precursor-based MOD process. The precursor solution was synthesized with low cost YBCO powders as starting materials and YBCO coated conductors have been deposited on IBAD substrate ($CeO_2$/IBAD-YSZ/SS). YBCO coated conductor prepared by dip coating shows transport $I_c$ of 15A/cm-w at 77 K. Microstructural and crystallographic analyses indicate that YBCO layer was grown in epitaxy with substrate and exhibited well-developed dense microstructure. Also discussed are processing and analysis of YBCO coated conductor by slot-die web coating method. It was shown that this oxide-based MOD process provides a low cost route to coated conductor with high $J_c$.

• 한국결정성장학회지
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• 제30권4호
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• pp.143-149
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• 2020

전복패각을 Ca원으로 이용하여 바이오 소재로 중요한 인산칼슘(calcium phosphates)들을 침전법을 통해 합성하였다. 전복패각에서 유래한 수산화칼슘(Ca(OH)₂)을 칼슘 공급원(전구체)으로 사용하였다. 수용액상에서 수산화칼슘과 인산(H₃PO₄)을 반응시켜 침전반응을 유도하여 인산칼슘화합물로의 합성을 유도하였다. 초기 전구체 Ca/P 비율을 1.50, 1.59 및 1.67로 조절하였으며 이 조성변화와 침전물에 대한 열처리가 분말 및 소결체의 물성에 미치는 영향에 대해 조사하였다. 초기 전구체 Ca/P 비율을 조절함으로써 소결체 상합성의 조절이 가능하였고, 1150℃에서 소결한 소결체에서(hydroxyapatite(HAp), β-tricalcium phosphate(β-TCP) 및 HAp와 β-TCP가 혼합된 2상 인산칼슘(BCP, HA/β-TCP))들이 합성되었다. 이러한 결과는 저비용, 고가용성을 가지는 경제적인 출발물질로부터 고부가가치 인산칼슘을 합성할 수 있는 가능성을 보여주었다.