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3. Crystallization under wetting/non-wetting conditions 35 3.4 Results We have studied the drying of a 1 M (molal [mole/kg]) sodium sulfate solution droplet for both non-wetting and wetting surfaces at temperatures of 8.7 ◦ C and 6 ◦ C, respectively, and a relative humidity (RH) of 0 %. A total of 40 experiments were performed, of which 95 % showed the crystallization behavior that will be discussed below. The signal to noise (S/N) ratio of the NMR experiments was about 35. Initially, the sample holders were filled with a 300 µl droplet of a 1 M sodium sulfate solution at an initial temperature of 40 ◦ C. Next, using the temperature control system the droplet was rapidly cooled from the initial temperature to the aimed temperature of the experiment. After this aimed temperature was reached an air flow of 0 % RH was applied over the surface of the droplet. From that moment on, simultaneous NMR measurements of the water and sodium concentration were performed together with timelapse microscopy of the droplet. Non-wetting: Non-wetting conditions were created by using Polymethylmethacrylaat (PMMA). A drying experiment was performed at a temperature of 8.7 ◦ C and a RH of 0 %. In figure 3.3 the measured water content, sodium content, and the concentration of sodium sulfate solution in the droplet are given as function of time. The corresponding images of the droplet at various times are shown in figure 3.4. 4 3 2 1 0 0 10000 20000 30000 40000 50000 60000 t [s] Fig. 3.3: Normalized sodium content, normalized water content, and concentration measured during drying at 8.7 ◦ C of a 300 µl droplet having an initial Na 2 SO 4 concentration of 1 M for a non-wetting surface, i.e., a PMMA sample holder. The dashed lines result from a free cubic spline interpolation and are shown as guides to the eye.
3. Crystallization under wetting/non-wetting conditions 36 A thermocouple B droplet-surface interface 14 mm droplet LED illumination moon-shaped droplet C D initial heptahydrate crystal formed heptahydrate crystal E dehydrating heptahydrate dehydration front F thenardite heptahydrate covered with thernadite forming anhydrous thernadite thernadite covering heptahydrate Fig. 3.4: Time-lapse microscopy of the drying at 8.7 ◦ C of a 300 µl droplet of a 1 M sodium sulfate solution on a non-wetting PPMA sample holder, corresponding to the data plotted in Fig. 3.3. These figures show that as soon as the drying has started, the water content decreases and a receding liquid/air interface is observed, reflecting the non-wetting conditions. As the sodium content remains constant, the concentration increases gradually and for some time no crystallization is observed.
Page 2 and 3: Sodium sulfate heptahydrate in weat
Page 4: To my family
Page 8 and 9: CONTENTS 1. Introduction . . . . .
Page 10 and 11: 1. INTRODUCTION 1.1 Introduction Sa
Page 12 and 13: 1. Introduction 11 This phenomenon
Page 14 and 15: 1. Introduction 13 1 2 initial mass
Page 16 and 17: 1. Introduction 15 However, our pre
Page 18 and 19: 2. SINGLE CRYSTAL GROWTH OF SODIUM
Page 20 and 21: 2. Single crystal growth of sodium
Page 32 and 33: 3. CRYSTALLIZATION UNDER WETTING/NO
Page 34 and 35: 3. Crystallization under wetting/no
Page 44 and 45: 4. NUCLEATION ON MINERAL SUBSTRATES
Page 46 and 47: 4. Nucleation on mineral substrates
Page 52 and 53: 5. SODIUM SULFATE HEPTAHYDRATE FORM
Page 54 and 55: 5. Sodium sulfate heptahydrate form
Page 62 and 63: 6. CRYSTALLIZATION OF SODIUM SULFAT
Page 64 and 65: 6. Crystallization of sodium sulfat
Page 72 and 73: M 6. Crystallization of sodium sulf
Page 74 and 75: 7. THERMODYNAMIC AND POROMECHANIC C
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7. Thermodynamic and poromechanic c
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8. NMR COMBINED WITH ACCELERATED WE
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8. NMR combined with accelerated we
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∆ 8. NMR combined with accelerate
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9. CONCLUSIONS AND OUTLOOK This cha
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9. Conclusions and Outlook 107 Soft
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APPENDIX: CALCULATION OF SALT CRYST
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Appendix: Calculation of salt cryst
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Bibliography 113 [15] L.M. Luquer,
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Bibliography 115 [47] D. Rosenblatt
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Bibliography 117 [78] H.P. Huinink,
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LIST OF PUBLICATIONS Published: •
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ACKNOWLEDGMENT This thesis would no
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CURRICULUM VITAE Tamerlan Saidov wa
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