Thesis
Investigating mechanisms of laser induced nucleation
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2018
- Thesis identifier
- T18135
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- This thesis describes work investigating the mechanism of non-photochemical laser induced nucleation in aqueous glycine and urea solutions. Nucleation is the first step of the crystallisation process, the second being crystal growth. Crystallisation is an important process used by many industries including chemicals, food and pharmaceuticals. It can also be used as a way of installing a set of particulate solid properties onto the compound which can be beneficial for production and use. Uncontrolled nucleation can lead to unwanted crystal forms or uncontrolled particles size distributions which can cause wasted time and money in production. Nonphotochemical laser induced nucleation offers the possibility of controlling when and where the nucleation occurs. However, the mechanism is not understood which would need to be addressed before it could be considered a viable tool. An experimental set up was used for irradiation and monitoring to measure induction time. With this set up it was demonstrated that by increasing supersaturation and laser power you could increase the probability of laser induced nucleation. With the monitoring set up it was shown that two simultaneous nucleation mechanisms are present: the first fast laser induced nucleation and the second slower spontaneous nucleation. Through the use of a biexponential function it was possible to identify the proportion of laser induced samples undergoing laser induced nucleation and a characteristic time which could be used to calculate the respective nucleation rate. Nano-filtration was shown to suppress laser induced nucleation. Through a series of dynamic light scattering and irradiation experiments it was shown that even when solute clusters were present in solution after nano-filtration with larger pore size, laser induced nucleation was suppressed. Thus, it is possible to exclude any mechanistic theory that solely involves the presence of solute clusters. Subsequent experiments found that the source of a necessary initiator was in the solvent (deionised water). Treatment of the deionised water by rotary-evaporation, distillation, and reflux increased the proportion of samples undergoing laser induced nucleation, which will considered the nucleation efficiency. It was found that this increase was also achieved by degassing the deionised water, which suggests that the processing of the deionised water was improving the distribution of initiators particles as nothing is being added and only gas is being removed. It was found that different sources of water have different effects on laser induced nucleation and the greater treatment resulted in greater proportion of samples undergoing laser induced nucleation. Polymorphism is an important aspect of crystallisation, and laser induced nucleation has shown an influence on glycine polymorphism. It was demonstrated that a consistent 60:40 alpha:gamma polymorphism split is achieved when using linear polarized laser light. This was shown in deionised water, HPLC grade water, and the residue and distillate of distilled deionised water, which all had different proportion of samples undergoing laser induced nucleation. This suggests that the polymorphic influence is an independent aspect of the mechanism from the amount of initiators present.
- Advisor / supervisor
- Sefcik, Jan
- Resource Type
- DOI
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