Here, we accompany experiments with molecular dynamics simulations to investigate crystallization of an anti-tuberculosis drug, isoniazid, in different solvents. However, the role played by solvents in affecting crystal morphology remains elusive. In solution crystallization, solvent has a profound effect on controlling crystal morphology. An outstanding photocatalytic RhB degradation performance is therefore observed for 60-C 3N 4 with ~ 35-fold higher pseudo-first reaction rate constant than the bulk g-C 3N 4 control group sample. Under 60 rpm agitation during the synthesis, the 60-C 3N 4 exhibits remarkably larger specific surface area, stronger photo-oxidation capability, reduced bandgap and suppressed electron-hole recombination comparing with the control group g-C 3N 4 synthesised via conventional thermal polycondensation method. The optimal synthesis condition for Cl-doped g-C 3N 4 is associated with a moderate agitation rate of 60 rpm (60-C 3N 4). Due to the different effects of Cl int and Cl sub on the electronic/molecular structure of g-C 3N 4, the photocatalytic activity of g-C 3N 4 can only be optimised by balancing the concentration of Cl int and Cl sub dopants. It is found that both the molecular and electronic structure of the prepared g-C 3N 4 correlates strongly with the atomic ratio of interstitial to substitutional Cl dopants (Cl int/Cl sub), which is determined by the agitation rate during the solvothermal synthesis. However if one desires to avoid inclusion formation in the transition from dissolution to growth, it is advantageous to grow in the absence of convection so that the transition from dissolution to growth may be made gradual.Ĭl doped g-C 3N 4 with controllable doping site is synthesised for the first time via an agitation-assisted solvothermal method. In order to avoid this condition, either crystals must be grown very slowly or well-controlled vigorous convection must be used. Faceted growth can become unstable when step trains decelerate, which occurs when steps begin in regions of high supersaturation and move to regions of low supersaturation. High quality crystals can be grown from solutions because step propagation is faster than step generation, as manifested by the presence of facets. Constitutional supercooling is always present in solution growth, but does not prevent growth without interface breakdown. The operational challenge in crystal growth from solutions is to maximize the growth rate without trapping the solution as inclusions in the crystal. With convection, the mass transport rate is not proportional to the diffusion coefficient and the heat transfer rate is not proportional to the thermal conductivity. There is no unstirred layer near the surface of the crystal. It is also important to note that the stagnant film model for heat and mass transfer in the presence of convection is a fiction and can lead to erroneous predictions. This convective contribution has the effect of increasing the growth rate beyond that predicted by Fick's first law, especially when the solubility is large. The flux of a solute into the surface of the crystal equals the growth rate, and includes a contribution caused by the movement of the solution toward the crystal surface. If the component is charged, its movement is also strongly influenced by an electric field, which may be generated by the diffusion process itself. It is possible for a component to move from a region where its concentration is low to a region where its concentration is high. In multicomponent systems the flux of a component depends on the concentration gradients of all the other constituents. the mass transfer flux is not necessarily equal to the product of a concentration gradient and a diffusion coefficient. It is important to realize that the simple form of Fick's first law is often not valid in crystal growth from solutions, i.e. Except in liquid metals, heat transfer in liquids is also strongly enhanced by convection. Similarly, convection can be caused by a variety of driving forces a pressure gradient, mechanical forces, buoyancy, electric fields, and even the growth of the crystal itself. In solutions, mass transfer is strongly enhanced by convection the motion of the solution carries material with it. Mass transfer arises primarily from concentration gradients, but can also be caused by a temperature gradient (Soret effect), an electric field, acceleration of gravity, etc. These prosesses strongly influence growth rate, crystal morphology, and defect formation. Transport phenomena are normally taken to include fluid motion (convection), heat transfer and mass transfer. This is a review of the role of transport phenomena in crystal growth from solution.
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