Dissertation > Mathematical sciences and chemical > Crystallography > Crystal defects

The Effect of Ultrasound on the Chiral Symmetry Breaking of NaClO3 during Crystallization

Author WangJing
Tutor LiHong
School Tianjin University
Course Materials Physics and Chemistry
Keywords ultrasound crystallization sodium chlorate optical rotation chiral symmetry breaking
Type Master's thesis
Year 2008
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NaClO3 crystal is a sort of inorganic material. It belongs to the cubic chiral space group P213 and its crystal lattice parameters are a=b=c=0.657584 nm, Z=4.It has L and D enantiomers.The chiral symmetry breaking (CSB) during crystallization of NaClO3 has long intrigued many scientists of Physics, Chemistry and Biology. It is well known that ultrasound has special effect on crystallization. However, the combination of ultrasound and CSB is rarely mentioned. In the thesis the effect of ultrasound on the CSB of NaClO3 is mainly studied. The microscopic mechanisms of CSB is presented, and the experimental results are explained further by the recycled competition—autocatalysis. The main content and experimental results are as follow:In Chapter 1, the research background and the knowledge of ultrasound and crystallizations are introduced. The research background actualities of CSB of NaClO3 are reviewed in detail. Then the research objective is put forward.In Chapter 2, the theory and measurement of optical rotation are described. The microstructure, appearance and solubility of NaClO3 crystal are presented. These are necessary for the further study.In Chapter 3, the effect of ultrasound on the crystallization of NaClO3 aqueous solution has been systematically investigated, mainly from the aspects of metastable zone width, induction time and crystal size. The results of experiments with ultrasonics indicate that, compared with those stirred, the metastable zone width decreases by 5 to 7 degrees in centigrade, the induction times lower down by 2 to 6 times, and the crystal sizes become smaller. The results are analyzed by thermodynamic theory.In Chapter 4, the effect of ultrasound on the CSB during crystallization of NaClO3 has been investigated systematically and compared with those unstirred and stirred. Three cases are investigated, one is that during induction time of samples, ultrasound is added for several times but the solutions don’t crystallize. The results indicate that the CSB isn’t obvious. The other is that during cooling crystallization of NaClO3, ultrasound is added until seeing crystals in the solutions. The results present CSB clearly. Last, the processes are investigated and the results show that the CSB becomes more and more clearly along with the time of insonation. But the CEE values don’t become unit. According to the current CSB mechanisms and ultrasound special characteristics, several hypothesises are brought forward. The effect of ultrasound may be explained further by nonlinear autocatalytic dynamic of secondary nucleation and recycled competition.

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