AFM을 이용한 Mica 위의 NaCl 결정화에 관한 연구

한성웅, 김종민*, 김우식**, 村松 宏*,장상목

동아대학교 화학공학과, 일본 세이코 연구소*, 경희대학교 화학공학과**

Crystallization of Sodium Chloride on Mica

in Water-methyl alcohol System.

Sung-Woong Han, Jong-Min Kim*, Woo-Sik Kim**, Hiroshi Muramatsu*, Sang-Mok Chang

Dept. of Chemical Engineering, Dong-A University, Seiko Instruments Inc*.

Dept. of Chemical Engineering, Kyoung-Hee University**

ABSTRACT

The face specific crystal growth rates of sodium chloride (NaCl) in aqueous solution have been determined under the influence of the concentration of methyl alcohol. Mica has been used in the controlled crystallization of NaCl. The difference in the crystallization efficiency for the different surfaces of bare mica, Mg2+ soaked mica is discussed.

The best of crystallization is found from the suface of bare mica for the same exprimental condition. Increasing the concentration of methyl alcohol, the particle size and amount of  NaCl was increased. From AFM images, it can be confirmed the difference of crystallization of NaCl.

INTRODUCTION

Since it has been found that the presence of additives or contaminants can influence the crystal habit significantly, the search for face specific growth inhibitors has become an interesting field for industrial crystal habit is not wanted, the more isometric growth forms are preferred. Therefore attempts are made to discover face specific additives which increase the crystal growth rate of the fastest growing directions[1].

Recently, a range of strategies has been explored to control nucleation and growth of crystals based on molecular recongnition at interfaces[2-4]. These methods include template-directed crystallization under compressed Langmuir monolayers[3,4], on self-assembled monolayers (SAMs) [5,6], on oriented polymer films[7,8], and in surfactant aggregates[2,9].

In this study we have been used the mica to confirm the difference in the crystallization efficiency for the different surfaces of bare mica, Mg2+ soaked mica is discussed.

The relation with the concentration of methyl alcohol and the particle size and amount of crystallization was also discussed with AFM images.

EXPERIMENTAL

Slide glass was obtained from Matsunami Glass Ltd. (thickness: 0.12-0.17 mm, width 2450 mm), washed with acetone and DDW. Mica of thickness 0.01 mm was purchased from HKK Inc., washed with acetone and deposited slide glass with an adhesive bond. In the cases of experiments with divalent cation-treated mica, the treatments were also performed before crystallization. Divalent cation-treated mica was prepared by dropping a 10□L portion of 1 mM MgCl2 aqueous solution and waiting for 10 min.

The mica soaked in 1M NaCl solution with 10%, 20%, 40% methyl alcohol respectively for 10 minutes.

After making NaCl crystal on the mica, washed with ethyl alcohol and blew with N2 gases.

RESULTS AND DISCUSSION

Figure 1 shows the NaCl crystals on the mica dropped a 10□l portion of 1mM MgCl2 solution in 1M NaCl solution with 10% methyl alcohol for 10 minutes. It can be confirmed that the NaCl crystals grew irregularly.

In this results, cation-treated mica has few interaction with NaCl crystals in the water-methlyl alcohol solution.

Figure 2 shows the NaCl crystals on the surface of bare mica in same conditions with figure 1. On Mg2+ soaked mica, NaCl particles growthed on the local areas. But the crystals grew up more regularly on the surface of bare mica than Mg2+ soaked mica.

Fig. 1. The NaCl crystals on Mg 2+ soaked mica in 1M NaCl solution with 10% methyl alcohol for 10 minutes.

In case of Mg2+ soaked mica, there is no heterogeneous crystallization except for homogeneous crystallization. So the crystals growthed locally and irregularly. But the case of bare mica, negative charge of the surface on bare mica has some interaction with Na+ ion in the NaCl solution.

Figure 3 shows the NaCl crystals on bare mica in 1M NaCl solution with 40% methyl alcohol for 10 minutes.

Fig. 2: The NaCl crystals on bare mica in 1M NaCl solution with 10% methyl alcohol for 10 minutes.

Fig. 3: The NaCl crystals on bare mica in 1M NaCl solution with 40% methyl alcohol for 10 minutes.

It can be shown in this figure increasing the concentration of methyl alcohol, the particle size and amount of  NaCl was increased remarkably.

We didn't show in this paper but we can also confirmed that the crystallization of NaCl on 3-aminopropyltriethoxysilane-coated mica and ethyltriethoxysilane-coated mica in water-methyl alcohol system.

CONCLUSIONS

Two kinds surface of mica have been investigated about their effect upon the crystallization of sodium chloride. The positively charged mica can not profoundly influence the crystallization. While the negative charged mica has some interaction with NaCl crystals in solution.

Increasing the concentration of methyl alcohol, the particle size and amount of  NaCl was increased.

ACKNOWLEDGMENTS

This work was supported (in part) by Dong-A University and the Korea Science and Engineering Foundation (KOSEF) through the CIIPMS at Dong-A University.

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