Noise-reduced electrodepostion is performed in an agarose gel medium containing CuSO4 solution. Instead of random fractal-like patterns usually seen in CuSO4 aqueous solution electrodeposition, the deposit shows a smore ordered morphology. The dendritic pattern with and evident main stem can be seen. Alternating tip splitting has been observed druing the dedritic growth. It is suggested that the suppression of convective noise near the growing interface is responsibel for the appearance of dendrites in this experiment. The alternating dendrite tip splitting is interpreted as the reslut of altenating accumuation adn depletion of imprutites in front of the growing interface.

A consecutive rotation of crystallographic orientation has been observed in lateral crystallization of NH4Cl on a glass substrate, which induces a periodic distribution of faceted and roughened regions on the surface of a crystallite aggregate. Experimental observation indicates that this phenomenon derives from the asymmetric surface energies at the growth front, which deform the nascent nucleus and tilt the crystallographic orientation in the nucleation-mediated layered growth. We suggest that this effect is significant for a class of lateral growth where nucleation plays a dominate role.

The morphology of iron electrodeposit is shown to relate closely to the pH of the electrolyte solution. Macroscopically, depending on the strength of the interbranch convection, which is associated with the concentration of H3O1 in the electrolyte, the deposit morphology varies from treelike pattern to meshlike pattern and dense-branching morphology. Microscopically the deposit is ramified and dense-branching at lower concentration of H3O1, while it becomes relatively smooth and stringy at higher H3O1 concentration. The symmetry of the convective vortices on the two sides of the growing tip is observed to decide the growth behavior of the tip. We suggest that H3O1 influences the pattern formation and pattern selection in the electrodeposition of iron from FeSO4 solution by either initiating interbranch convection or changing the effective interfacial energy of the deposit and the electrolyte.

The dynamic behavior of the concentration field in crystallization is investigated by considering the coupling of the bulk concentration field and interfacial kinetics. It is shown that the concentration field may become unstable for perturbations with certain wavelength. When instability occurs, the physical environment in front of the growing interface will fluctuate and the interfacial growth mode will be affected accordingly. We suggest that our analysis can be used to interpret some spatial-temporal instabilities observed in crystallization.

ELECTRODEPOSIT1ON of metals such as copper and zinc from solutions of their salts may give rise to ramified metal deposits which show a range of growth morphologies1-9. Our understanding of the factors that determine growth morphology is still very limited, in part because different morphologies may be observed even under similar growth conditions 4,5. It is thought9 that uncontrolled convective processes at the tips of the deposit branches may play a role in these discrepancies. Here we show that convective effects, which we can visualize directly, in the electrodeposition of iron from FeSO4 solution, can generate a mesh-like pattern, a morphology that has not been reported previously. Convection can be diminished by altering the pH, whereupon we see a transition to a dense branching morphology. Our results show that convective effects do indeed play an important part in determining pattern selection during electrodeposition.