펄스 전류를 이용한 nanocrystalline 아연 도금 강판 제조 및 특성 = (A) study on the synthesis and characteristics of pulse-plated nanocrystalline Zn coated sheet

다국어 초록 (Multilingual Abstract)

Recently, great research effort is underway in the areas of production and characterization of nanocrystalline materials. However the major hindrance in the industrial application of nanocrystalls is still the availability of these materials.
In this thesis, the pulse plating technique was used to produce nanocrystalline Zn deposits from a chloride-based and sulfate-based electrolyte. The influence of the pulse plating variables, namely, pulse on time, off-time and peak current density on the grain size, surface morphology and preferred orientation of the deposits were studied. The effect of additives such as the buthyl-additives, USSP, etc were also investigated and X-ray diffraction was employed to determine the grain size. Furthermore, the properties such as the micro-hardness, phosphate performance and the corrosion behavior were evaluated and were compared with the conventional used Zn polycrystalline.
If a shorter pulse time and longer break time are used, the Zn deposits show a finer grain size. It is thought that this effect is due to the enhancement of the nucleation rate by the high pulse current density and the resulting high overvoltage. Increasing the off-time shifted the preferred orientation from the (002) to the (112) (101) texture. Increasing the on-time, the (110) texture was obtained.
The texture of the Zn deposits obtained from the chloride based bath containing the Buthyl-additives was independent of the peak current density. The grain size which reduced was obtained and ranged from 30nm to 50nm.
The results of salt spray test (JIS Z 2371) indicated that the corrosion resistance of nanocrystalline Zn coating was the same as that of the polycrystalline Zn coating. However the hardness of the nanocrystalline Zn coating layer was observed to increase to 130 ~ 150Hv,(regular Hall-Petch behavior) and the surface appearance of the nanocrystalline Zn coating layer was observed to have the brightest glossiness(G : 80 ~ 100), which has never been seen in the chloride based bath.

목차 (Table of Contents)

• 1. Introduction 1
• 2. Literature Review 5
• 2-1 Nanocrystalline Material 5
• 2-2 Pulse Plating 7
• 2-2-1 Background 7
• 2-2-2 Electrochemical Kinetics 12
• 2-2-3 Crystallization 13
• 2-2-4 Capacitance 14
• 2-2-5 Mass transport 19
• 2-3 Electrical appliance and Machinery 22
• 2-3-1 Inductance Connection 23
• 2-3-2 Class of Power supply 25
• 2-3-3 R L C Modeling on AC Power supply 30
• 2-3-4. Power Supply 34
• 3. Experimental 50
• 3-1 Plating experiment 50
• 3-2 Analysis of deposits & Evaluation of physical property 54
• 3-3 Phosphating treatment and Electropainting 55
• 3-4 Electrochemical measurement 58
• 4. Results & Discussion 59
• 4-1 Pulse power supplier 59
• 4-1-1 Measurement of the load impedance 63
• 4-2 Study strategy 79
• 4-3 Chloride-based bath 83
• 4-3-1 Influence of pulse plating parameters on deposit structure 85
• 4-3-2 Additives containing chloride based bath 97
• 4-3-2-1 USS-P containing bath 97
• 4-3-2-2 buthyl- additives containing bath 107
• 4-4 Sulfate-based bath 118
• 4-4-1 Influence of pulse plating parameters on deposit structure 120
• 4-4-2 Additives containing sulfate based bath 123
• 5. Conclusions 130
• 6. Reference 133
• 7.Appendices 139
• 7.1 Appendix A - Power Supply 시운전 결과 139
• 7.2 Appendix B – Scherrer Formula 145
• 8. Vitae 148