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김지홍,김보라,임지선 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.12
This study aimed to optimize the molecular weight range of coating pitch to enhance the electrochemical performance of graphite-based anodes used in lithium-ion batteries by understanding the characteristics of the coating pitch. The coating pitch was divided into four fractions based on its solubility in hexane, acetone, toluene, and n-methyl-2-pyrrolidone (NMP). These four fractions were estimated based on the thickness and homogeneity of the coated surfaces. The lighter fractions of pitch, such as hexane and acetone, assisted in forming a homogeneous surface by decreasing the viscosity during carbonization. Heavy fractions, such as toluene and NMP, were the main components of the coating. They improved the rate performance of the anode by forming an isotropic layer, which increased the number of lithium-ion intercalation sites. However, thick surfaces increased the charge-transfer resistance because of the increased diffusion path lengths of lithium ions. The pitch molecular weight fractions of 128–768, 768–1152, and 1,152–1,480 m/z should be controlled to 70–84.49, 11.20–18.21, and 3.35–5.15%, respectively. Furthermore, the results of this study can be applied to optimize the coating properties for other anode materials, such as silicon, at a controllable pitch coating thickness according to the molecular weight.
Microtribology of Alumina Particles on Metal-coated Surfaces
K. B. Paul,Karmen B. Tzalikian 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.2
The friction of alumina micro-size particles with radii between 0.5 and 30 µm on Co, Cr and Au - coated Si(100) surfaces is presented and analyzed in terms of classical mechanical and unconventional components relevant to these scales. Friction parameters related to the rolling and the sliding friction (K1 and y0), the van der Walls forces (K2) and the depth of electromagnetic penetration (t) are estimated from the experimental results. The development of the friction parameters when the surfaces are coated is described and discussed. The measurements are based on optical observation of the motion of a single micro-particle on a surface under ambient conditions. The motion is initiated by using a mechanical vibration with a micrometer amplitude at frequencies in the acoustic range. The long-range van der Waals forces and the short-range adhesive forces are found to become dominant with contributions of up to 80% for particle sizes below 7 µm and 9 µm for the coated and the bare surfaces, respectively.
박판 강재의 고속 심 용접성에 미치는 Sn 도금의 영향
김기철,이목영 대한용접접합학회 1998 대한용접·접합학회지 Vol.16 No.5
High speed wire seam weldability of tin coated thin gage sheet steels was investigated. Thickness and coating weight ranges of the test materials were 0.21~0.35mm and 1.1/1.1~2.8/11.2g/$m^2$, respectively. Test results indicated that the surface roughness value, Rz decreased as increasing the coating weight. The Rz was thought to be one of the important factors to influence the optimum welding condition range, $\triangle$Q. The $\triangle$Q showed close relationship with welding conditions such as welding pressure and travel speed. Higher welding pressure widened the $\triangle$Q while higher travel speed reduced the $\triangle$Q value. Results also demonstrated that tin coating weight should be optimized based on the weldability or the serviceability after welding. At th HAZ of sheet materials with thinner coating layer, tin depleted zone was produced since molten film of the coating material on the base metal agglomerated by the surface tension, which could result in reducing the corrosion resistance of the HAZ in the service environment.
Kim,Kug Chan,Park,Seon Young,Lee,Kang Suk,Kim,In Gyu 대한방사선 방어학회 1997 방사선방어학회지 Vol.22 No.2
수놈 흰쥐를 1.0, 2.0, 3.0, 5.0 및 7.0 Gy 선량으로 전신 조사하였으며 조사 후 48, 72. 96시간과 216시간 경과 후 혈액을 체취하였다. 혈액내 ceruloplasmin을 측정하여 선량반응곡선을 완성하기 위하여 항원고정 방식의 경쟁적 효소면역측정법을 사용하였다. Ceruloplasmin 의 정제는 turpentine을 주사한 수놈 흰쥐의 혈액을 사용하였다. Ceruloplasmin의 흡착효율은 50mM carbonate/bicarbonate. pH 9.6보다 10mM Tris-HCl, 150 mM sodium chloride, pH 7.4에서 더 효과적이었으며 정량을 위한 적정한 ceruloplasmin의 흡착범위는 well 당 70∼140 ng이었다. Ceruloplasmin은 피폭 후 72∼96시간에서 최대농도를 보였으며 피폭 후 96시간에서 최대값을 지니는 선량반응관계를 보였다. Ceruloplasmin은 피폭 후 216시간에서도 피폭이전의 농도로 회복되지 않았다. 0.1 Gy로 피폭된 경우에도 ceruloplasmin의 농도는 피폭 후 72∼96시간에서 최대로 증가하였으며 단백질의 농도는 대조군과 유의성 있는 변화를 관찰할 수 있었다. Ceruloplasmin은 방사선피폭 후 변화하는 중요한 급성반응물질중 하나로 밝혀졌으며 방사선방호를 위한 유전자 발현 및 조절에 관한 연구가 필요하다. Adult male rats were exposed to a whole body with a single dose of 1.0, 2.0, 3.0, 5.0, and 7.0 Gy. The animals were sacrificed 48, 72, 96 and 216 hours following exposure. A competitive enzyme linked immunosorbent assay(ELISA) with antigen immobilized on the solid phase has been developed to measure ceruloplasmin in rat serum and complete dose response curves. Ceruloplsmin was purified from the plasma of turpentine treated male rats. Coating of ceruloplamin had more effectiveness in 10 mM Tris-HCl, 150 mM sodium chloride, pH 7.4 than in 50mM carbonate/bicarbonate buffer, pH 9.6. The coating range for ceruloplasmin was 70-140 ng/well. Levels of ceruloplasmin increased to maximum on the 72-96 hours after irradiation. Slope of between response and dose was greatest value 96 hours following irradiation. Normal ceruloplasmin levels were not recorded 216 hours following exposure. In 0.1 Gy irradiated group, levels of ceruloplasmin also increased to maximun on the 72~96 hours following irradiation. The concentration of this protein remained significantly different from control value, 196 hours after exposure. Ceruloplasmin was identified as one of the major acute phase protein following irradiation and further studies about gene expression and regulation would be necessary for radiation protection.
용접 조건이 소형 용기용 Sn 도금 강재의 와이어 심 용접성에 미치는 영향
김기철,이기호,이목영 대한용접접합학회 1997 대한용접·접합학회지 Vol.15 No.5
Effect of welding parameters such as current, speed and electrode pressure on the weld quality of tin coated steels for small containers was discussed in this paper. Welding was performed with low frequency wire seam welding system which was loaded with 1.5mm in diameter copper wire electrode. The welding parameters were monitored at the position close to the welding spot so as to minimize the instrumentation error, and the signals were stored into a digital data acquisition system before analysis. Results showed that critical current for sufficient nugget size increased as the base material thickness increased, while the width of the optimum welding range was reduced. The acceptable welding condition derived from this study was found to be effective within the thickness range of $\pm$10% of the nominal (0.25mm) thickness. Tin coating layer was proved not to affect seriously on the weld quality, i.e. strength and formability, since consumable wire electrode was used in this process. Test results also demonstrated that the welding current was thought to be the most effective parameter to form an acceptable weld, while welding speed or electrode pressure exerted less effect on the nugget formation. However, these two parameters played an important role because the former was related to the nugget overlap interval, and the latter, to the formation of expulsion during welding.
김원호,지창욱 대한용접접합학회 2022 대한용접·접합학회지 Vol.40 No.2
As environmental regulations have been tightened around the world, domestic and foreign automobile industries are increasing the proportion of hydrogen and electric automotive components using lightweight materials to reduce exhaust gas emissions and improve fuel efficiency. In particular, hot-stamped boron steel is being used as an alter- native material for frame weight reduction due to thickness reduction, excellent workability, and good elongation. However, surface coating is essential to prevent surface decarburization phenomena and oxidation scale formation between hot stamping processes of boron steel. The coating layer causes many problems in the weldability such as a narrow weldable current range and deterioration of mechanical properties during resistance welding. Therefore, in this study, we introduce research performed to improve the weldability of Al-Si coated hot-stamped boron steel in terms of the material and process.