• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.175-175
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• 2016

Sn도금액은 강산에서는 $Sn^{2+}$, 강알칼리에서는 $Sn^{4+}$석출이 안정하다. 중성영역은 도금액에 $Sn^{2+}$침전을 방지하기 위하여 착화제가 필요하다. 기록에 남아 있는 가장 오래된 Sn도금은 1856년 Gore가 4가의 주석산염을 사용한 알칼리성용액이다. 그 후 50~60년 사이에 2가의 염화주석($SnCl_2$)과 KOH에 Cyan 등의 착화제를 첨가한 도금액이 발표되었다. 최초의 실용적인 알칼리주석용액은 1931년 Oplinger의 4가 주석산 염으로서, $CH_3COONa$를 완충제로 사용하였고, $Sn^{2+}$을 산화시키기 위하여 과산화물이나 과 붕산염을 첨가하였다. 알칼리성 Sn용액은 Natrium용액과 Kalium용액이 있지만, Kalium염이 용해성이 좋고, Sn농도를 높여 전류밀도를 높일 수 있다. 알칼리성용액은 도금속도가 산성용액의 1/2로 되고, 음극효율도 80~90% 정도 낮아, 두꺼운 피막이나 생산성을 중시하는 부품에는 적합하지 않다. 초기의 산성용액은 Sn의 정련목적으로 사용되었고, Pb정련에 사용된 Fluor규산용액에 Gelatine을 첨가하였다. Mathers는 Cresol산을 첨가하여 미량의 Cresol포화용액을 사용하여 고속으로 두껍게 석출시킬 수 있었다. 독일의 Schloetter도 다양한 방향족 술폰산으로써 반 광택피막을 실현하였다. 산성Sn도금액은 첨가제에 어떠한 유기화합물을 사용하는가는 도금장치나 석출상태로써 결정할 수 있다. Hothersall과 Bradshaw는 Cresol술폰산을 첨가하여 도금액 안정성 향상을 발견했다. Cresol술폰산은 $Sn^{2+}$의 안정제이며, Gelatine은 분산제기능을 한다. 붕 불화용액은 Sn농도를 높일 수 있고, $2{\sim}12A/dm^2$의 고 전류밀도의 도금이 가능하다. 1937년 Schloetter가 개발하여 미국의 제철회사에서 사용되었다. Sn-Ni도금은 Ni도금보다도 뛰어난 내식성이 있기 때문에 자전거, 자동차부품에 사용되고 있다. 실용도금액은 1951년 Parkinson이 발표한 HBF/HCL용액이다. $SnCl_2$산성용액에서 표준전위는 -0.136V인데 비하여, Ni이온의 표준전위는 -0.25V이다. HF용액에서는 불화물이온이 $Sn^{2+}$의 석출전위를 (-)방향으로 이동시켜서 합금석출이 가능하다. Sn-Co도금은 Cr도금의 색조에 가깝고, 장식목적으로 사용된다. Cr도금 대체용으로 사용된다. 내마모성이나 내식성은 Cr도금보다도 떨어지기 때문에 장식목적에 한정된다. 1953년 Parkinson은 Sn-Ni도금연구에서 동일한 용액조성으로부터 Co 30%를 석출시켰다. Sn-Zn도금은 방식도금으로서 자동차부품에 많이 사용되고 있다. Sn과 Zn의 표준전위는 서로 멀리 떨어져 있기 때문에 산성용액에서는 공석될 수 없다. 1980년대에 들면서, 방식Cd(Cadmium)도금의 독성 때문에 Sn-Zn도금을 재인식 하게 되었다. 1957년 Vaid 등이 No Cyan도금액을 발표했다. 그 후 러시아의 연구자가 안정한 도금액을 연구하였고, Srivastava와 Muckergee가 1976년에 종합하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.1
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• pp.21-28
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• 2000

Although commercial PIV systems have been widely used for the non-intrusive velocity field measurement of fluid flows, they are still under development and have considerable room for improvement. In this study, a single-frame double-exposure PIV system using a high-resolution CCD camera was developed. A pulsed Nd:Yag laser and high-resolution CCD camera were synchronized by a home-made control circuit. In order to resolve the directional ambiguity problem encountered in the single-frame PIV technique, the second particle image was genuinely shifted in the CCD sensor array during the time interval dt. The velocity vector field was determined by calculating the displacement vector at each interrogation window using cross-correlation with 50% overlapping. In order to check the effect of spatial resolution of CCD camera on the accuracy of PIV velocity field measurement, the developed PIV system with three different resolution modes of the CCD camera (512 ${\times}$ 512, lK ${\times}$ IK, 2K ${\times}$ 2K) was applied to a turbulent flow which simulate the Zn plating process of a steel strip. The experimental model consists of a snout and a moving belt. Aluminum flakes about $1{\mu}m$ diameter were used as scattering particles for the liquid flow in the zinc pot and the gas flow above the zinc surface was seeded with atomized olive oil with an average diameter of 1-$3{\mu}m$. Velocity field measurements were carried out at the strip speed $V_s$=1.0 m/s. The 2K ${\times}$ 2K high-resolution PIV technique was significantly superior compared to the smaller pixel resolution PIV system. For the cases of 512 ${\times}$ 512 and 1K ${\times}$ 1K pixel resolution PIV system, it was difficult to get accurate flow structure of viscous flow near the wall and small vortex structure in the region of large velocity gradient.

• Analytical Science and Technology
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• v.11 no.4
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• pp.297-304
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• 1998

The three analysis methods, EPA method 3050, the method offered by Ministry of Environment in Korea, and modified method corrected in this laboratory, were studied to investigate the effect of matrix on the analysis of inorganic priority pollutants. 7 inorganic priority pollutants(Ni, Cr, Cu, Zn, Pb, Cd, Hg) were spiked to the plating, leather, paper, electric, and dye sludges. Mean recovery of the elements except Hg was 95.5% when the procedure of EPA method was applied. However, recovery by the two other extraction methods showed 11.1% and 27.7%, respectively. Digestions were done by MDS (microwave digestion system) and $HNO_3+HClO_4$ methods. To study organic and inorganic matrix effect, samples were made by adding triethanol amine as a organic matrix and $FeCl_3{\cdot}6H_2O$+$AlCl_3{\cdot}6H_2O$ as a inorganic matrix, respectively. The extracts were analyzed by AAS and HG-AAS. Mean recovery of the elements by the $HNO_3+HClO_4$ procedure, except Hg, gave better result than that of the MDS method. Mean recovery of elements was decreased when organic and inorganic matrices were added in the sludge samples. The procedure of MDS and $HNO_3+HClO_4$ digestion gave higher recoveries than that of direct analysis. In general, the results of the studies showed a significant matrix effect on the inorganic priority pollutants analysis in sludges.

• Clean Technology
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• v.8 no.2
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• pp.85-92
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• 2002

Red mud is generated as a by-product during the production of aluminum hydroxide from bauxite ore. In this study the red mud coagulants were prepared by reacting 100 ml of 5 M $H_2SO_4$ solution with 10g of red mud at $85^{\circ}C$ or by reacting 100ml of 9M HCl solution with 10g of red mud at $25^{\circ}C$. The prepared red mud coagulants were tested for their coagulation performance of pollutants in the municipal and industrial wastewater. In addition, the coagulation performance was compared with that of a commercially available coagulant ($FeCl_3$). As a result, the red mud coagulants were found to have a good removal efficiency of pollutants in the municipal wastewater (turbidity, phosphate phosphorus) and in the plating wastewater (turbidity, $Pb^{2+}$, $Cd^{2+}$, $Cu^{2+}$, $Zn^{2+}$, $Cr^{3+}$). In the experiment to remove COD in the petrochemical wastewater, the COD removal efficiency by the red mud coagulants was a little poor, but it was better than that by $FeCl_3$.