Crystal morphology impurities impact

Sensitivity Impure HNF shows a value of impact sensitivity of <1 Nm while pure or recrystallized HNF of the same batch exhibits an improvement to the level of >15 Nm. Some researchers have reported friction sensitivity of 25 N. However, the data on impact and friction sensitivity reported by various groups suggest that sensitivity depends not only on purity but also on particle size, shape of crystals and the type of contaminants. There is a lot of variation in the data reported by various investigators and it appears that this variation is attributed to differences in purity, particle size and morphology of HNF synthesized by different groups [84]. 

The ability to model the impact of impurities on the structure of a crystalline system is crucial it enables the impact of both solvents and impurities quantified. Both in terms of the overall morphology and where the interactions are likely to occur, thus providing a better understanding of the process chemistry of a system. Two principal techniques exist for simulating the effect of solvents/sorbates on the surface of a crystal Monte Carlo and Molecular Dynamics and Minimization. 

Impurity(ies) can have a profound effect on the growth rate and, in this case, on the approach to equilibrium solubility. As in many cases due to experimental time constraints, the actual cause of the improvement was not clearly established. A very effective method of determining the impact of impur-ity(ies) from the process in question is to recrystallize the compound from a pure solvent(s) and from its own mother liquor and compare crystal size, growth rate, and morphology. 

The physical and chemical properties of magnesium oxide are primarily governed by the source of the precursor, that is, derived from magnesite or precipitated from brine or seawater. Other important factors include time and temperature of calcination and the presence of trace impurities. Electron microscope studies have revealed that the precursor particle morphology has a large impact on the morphology of the final MgO particle. It has been shown that when brucite and magnesite crystals are thermally decomposed at low temperatures, pseudomorphs of a size and shape similar to the parent crystal are formed. 

The impact of solvent on product quality should be given early consideration in process development efforts since it can have a significant effect on crystal size, morphology, and purity. A poor initial choice of solvent may thermodynamically limit the effectiveness of the separation, irrespective of all other factors, including crystallizer design and cost. In Section 3.5.1, the thermodynamic considerations for minimizing impurity incorporation are outlined based on solvent selection. 

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