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최용,이승희 한국폐기물자원순환학회 2019 한국폐기물자원순환학회지 Vol.36 No.8
Globally, mercury management at the national level in Korea (Republic of) has been required by ratifying to the MinamataConvention. In particular, it is necessary to identify the sources of mercury waste. Red stamping inks in Asian countries suchas China, Japan and Korea have been used to prove identification. However, there is a lack of information on mercury contentand hazardous characteristics of mercury in red stamping ink. To evaluate hazardous characteristics of mercury in red stampingink, leaching tests such as Korea Extraction Test (KET) and Toxicity Characteristic Leaching Procedure (TCLP) were carriedout as well as mercury content analysis. The mercury content in red stamp ink was estimated to be 0.664 mg/kg. The leachingconcentrations of mercury were detected to be 0.4 μg/L or less in KET and 2.1 μg/L or less in TCLP. From these results, itwas found that the leaching concentration of mercury in red stamping ink was satisfied with the regulatory level prescribedby KET and TCLP. Hence, the red stamping inks in Korea were generally verified to be non-hazardous wastes.
최용 대한금속·재료학회 2019 ELECTRONIC MATERIALS LETTERS Vol.15 No.1
Nano-sized ferrite powders less than 50 nm were prepared through combustion reaction followed by pulverizing and separatingthrough ultrasonic-wet magnetic classifi cation processes to study the electromagnetic properties of the nano-sizedferrites for developing an high performance electromagnetic interference fi lter. Neutron diff raction analysis of the ferritesprepared at 10 MPa of oxygen pressure shows that the fi nal phase is Ni 0.33 Zn 0.67 Fe 2 O 4 ( 2 = 1.48), which lattice parameteris 0.8412(2) nm. The residual magnetization, maximum magnetization, coercive force, susceptibility and Curie temperatureof Ni 0.33 Zn 0.67 Fe 2 O 4 particles are 0.88 Wb/m 2 kg, 7.749 Wb/m 2 kg, 1292 A/m, 0.068 m 3 /kg, and 413.93 K, respectively. Finally, the nano-sized ferrite particle less than 50 nm with more than 99% purity were obtained. The increasing frequencyreduced complex permeability which real value (μ r0 ) shows the maximum value at the less than 0.5 GHz. The dielectricconstants of the powders are ε r ′ = 5.7 and ε r ″ = 2.5. The nano-sized Ni 0.33 Zn 0.67 Fe 2 O 4 ferrite absorber works eff ectively inthe range of 3–5 GHz.
구리-니켈 다층 나노 도막 제조와 전자파 차폐 효과 평가
최용 대한금속·재료학회 2020 대한금속·재료학회지 Vol.58 No.9
Thin copper-nickel foil with multi-nano layers was prepared by pulse-electroforming to develop a high performance electromagnetic shielding material for electronic devices. The pulse electroforming conditions of the aqueous solution chemistry were selected based on the aqueous copper-nickel-sulfur phase diagram and an evaluation of the deposition rate using the finite element method based on the current distribution in front of a cathodic electrode. The thermodynamic stability diagram revealed that the coppernickel multi-nano layers could be formed at pH<4 and ΔE>1.0 V in a modified sulfide bath. The electro-formed copper-nickel multi-layer was well produced at the pulse plating conditions of –0.2VSHE, –0.5 mA/cm2, and 25 seconds for copper layer and –1.7 VSHE, –50 mA/cm2 and 80 seconds for nickel layer, which was composed of about 25 nm thick copper and about 30 nm thick nickel rich phases, respectively. The average deposition rate of the copper-nickel foil with multi-nano layers was estimated by the finite element method to be about 0.115 mm/sec, which was in good agreement with the real value of the thin multi-nano layered copper-nickel foil. The effectiveness of the electromagnetic shielding of the copper-nickel mesh with multi-nano layers was more than 30% higher than that of copper mesh in the frequency range of 8.2 and 12.5 GHz.
최용,백열,문병문,손동성 한국원자력학회 2017 Nuclear Engineering and Technology Vol.49 No.3
A dynamic nanoindentation method was applied to study an Fe-18 at.% Gd alloy as aneutron-absorbing material prepared by vacuum arc-melting and cast in a mold. The Fe-18at.% Gd cast alloy had a microstructure with matrix phases and an Fe-rich primarydendrite of Fe9Gd. Rietveld refinement of the X-ray spectra showed that the Fe-18 at.% Gdcast alloy consisted of 35.84 at.% Fe3Gd, 6.58 at.% Fe5Gd, 16.22 at.% Fe9Gd, 1.87 at.% Fe2Gd,and 39.49 at.% b-Fe17Gd2. The average nanohardness of the primary dendrite phase and thematrix phases were 8.7 GPa and 9.3 GPa, respectively. The fatigue limit of the matrix phasewas approximately 37% higher than that of the primary dendrite phase. The dynamicnanoindentation method is useful for identifying local phases and for analyzing localmechanical properties.