Solute segregation

S. Coriell, R. Boisvert, R. Rehm, R. Sekerka. Lateral solute segregation during unidirectional solidification of a binary alloy with a curved solid-liquid interface. J Cryst Growth 54 167, 1981. 

Nitric acid Cr II 5 N H2SO4 -1- 0-5 N Boiling with solution 1. Mass loss per unit (a) Redox potential Solute segregation to... 

These measures of solute segregation are closely related to the spatial and temporal patterns of the flow in the melt. Most of the theories that will be discussed are appropriate for laminar convection of varying strength and spatial structure. Intense laminar convection is rarely seen in the low-Prandtl-number melts typical of semiconductor materials. Instead, nonlinear flow transitions usually lead to time-periodic and chaotic fluctuations in the velocity and temperature fields and induce melting and accelerated crystal growth on the typically short time scale (order of 1 s) of the fluctuations. 

Solute segregation with bulk convection is given rigorously by solving the two-dimensional solute balance equation [for a two-dimensional velocity... 

Several groups (84-86) have extended the similarity analysis of Burton et al. (73) to the case in which an axial magnetic field is imposed on the melt with sufficient strength such that Ha >> 1 and N 1. With these limits, a closed-form asymptotic expression describes the variation in the flow field across the thin 0(Ha 1/2) Hartmann layer adjacent to the disk. Axial solute segregation across this layer was analyzed by assuming that the melt outside of the Hartmann layers is well mixed. The effective segregation coefficient approaches 1 when the field strength is increased, as expected for any mechanism that damps convection near the crystal. 

The flows and the consequent solute segregation caused by thermo-solutal convection in nondilute alloys is only beginning to be explored by experimental and computational analyses. Recent results are discussed by Brown (5). 

First, the role of system design on the details of convection and solute segregation in industrial-scale crystal growth systems has not been adequately studied. This deficiency is mostly because numerical simulations of the three-dimensional, weakly turbulent convection present in these systems are at the very limit of what is computationally feasible today. New developments in computational power may lift this limitation. Also, the extensive use of applied magnetic fields to control the intensity of the convection actually makes the calculations much more feasible. 

Although typically whiggish, Smith s historical survey is extremely rich and useful because it emphasizes the interplay between various academic disciplines and the longstanding practical tradition of metallurgists. The quotation above points out at the two fundamental notions - structure and properties - of modem metallurgy which are also the basis of the conceptual framework of modern materials science. The earliest notions on metallic structures - polycrystallinity, solid solutions, segregation, diffusion, deformation - were not elaborated by theoreticians but rather by practitioners. [7]... 

Subramanian S. V. Haworth C. W. Kirkwood D. H., Growth morphology and solute segregation in the solidification of some iron alloys. JISI, 206 (1968), 1027-1032... 

Considering the fact that the calculations strictly apply to a cylindrical joint configuration and monolithic ceramics rather than anisotropic materials such as composites, and the fact that chemical interactions and solute segregation will irrevocably and unpredictably modulate the joint properties, the calculated strain energy values are probably reasonable. 

Two incompatible polymers repeal each other so that the mixture of the two cannot form a pure solution. Segregation occurs and a more or less regular structure... 

Jaccard, C. (1966). Solute segregation at the curved surface of a growing crystal (steady state). Phys. kondens. Materie 4, 349-54. [119] Jaccard, C. (1967). Electrical conductivity of the surface layer of ice. In Physics of Snow and Ice (ed. H. Oura), pp. 173-9. Japan Institute of Low Temperature Science, Hokkaido Univ. [243]... 

Kingery, W. D. (1974). Plausible concepts necessary and sufficient for interpretation of ceramic grain-boundary phenomena I, Grain boundary characteristics, structure and electrostatic potential II, Solute segregation, grain-boundary diffusion and general discussion. Journal of the American Ceramic Society, 57, 1-8 and 74-83. 

Both of these segregation phenomena can contribute to solute segregation that occurs over a longer distance from the boundary than expected from pure equilibrium considerations. Indeed, many measured segregation solute profiles near boundaries extend into grains at a greater distance than expected from equilibrium vacancy consideration. If such segregation affects corrosion tendencies, then IGC can occur. 

---