Use of confinement and additives to control inorganic crystallization

This thesis describes the investigation of the three minerals, calcium sulfate, calcium phosphate and calcium carbonate under two bio-inspired methods, additives and confinement. The first experiment in Chapter 3 investigated the precipitation pathway of calcium sulfate above and under the solubility levels. Two metastable phases were obtained at ambient condition, hemihydrate and amorphous calcium sulfate (ACS), that first revealed hemihydrate can be found in room temperature and the existence of ACS. The transformation of ACS to the most stable phase, gypsum via hemihydrate was also proved under the titration and Cryo-TEM at undersaturated solution. Chapter 4 deals with the investigation of calcium sulfate grown in the presence of additives. These additives which have the profound inhibition effect provide another evidence of the existence of hemihydrate and ACS in the ambient conditions. Neglected before in literature, the morphology change of gypsum and hemihydrate also provide an aggregation-based transformation from hemihydrate to gypsum. Similar results were obtained growing calcium carbonate in confinement allowing formation of amorphous calcium carbonate. The results in Chapter 5 also demonstrated that confinement plays a significant role in the formation not only of the amorphous phase, but also the metastable phase, hemihydrate. Results were obtained in the absence and presence of the additives that lead to stabilize hemihydrate and ACS for more than 24 hours. Precipitation of calcium phosphate in confinement in the absence and presence of the additives used the same method as mentioned in the previous chapter. Similar results were obtained and again demonstrated that confinement and additives play a more significant role in bone formation. The last chapter investigated the crystallization pathway of calcium carbonate under UV-Vis at 2-10 mM concentration solutions with/without additives. The in-situ experiment in Chapter 7 provides a simple method to investigate the influence of concentrations of calcium carbonate solution and additives. Amorphous calcium carbonate nanoparticles were formed at early stage which transformed to stable calcite with time