Solute clusters precipitates

In aqueous solution, the mixture of solutions containing cadmium and sulfide ions induces a precipitation of CdS semiconductor. When adding a protecting polymer such as sodium hexainetaphosphate (HMP) in the solution, no precipitation is observed and a yellow solution remains optically clear, indicating the formation of CdS clusters. In reverse micelles, similar behavior of the latter is observed, as shown later. 

The activity of enzymes allows for rapid accumulation of insoluble ferric iron aqueous species in solutions where inorganic reactions would occur slowly or not at all. The reaction kinetics may impact the nature of nanoparticles produced (composition, structure, defect structure). However, it should be noted that the crystallization reaction itself is not enzyme mediated and the reaction often does not occur within or on the cell wall. Ferric iron ions diffuse out of the periplasm to form molecular clusters and/or nanoparticles in solution. The precipitation mechanisms probably differ only slightly from those involved in inorganic reactions. 

The line corresponds to the maximum value of the total concentration of cadmium ions in solution without precipitation of the hydroxide. If the experimental value is higher, then cadmium hydroxide clusters will be formed in the solution which can be converted into sulfide clusters (chapter 4). This must be taken into account in fixing the metal concentration in the CBD bath. It is possible to modify the solubility limit by changing the strength of the ligand or its concentration as also shown in figure 6. 

Application to RPV steels solute-enriched clusters, precipitates and grain boundary segregation... 

Van Ouytsel et demonstrated that IF measurements are sensitive to long- and short-range damage mechanisms and that the results are consistent with results obtained from impact, tensile and hardness testing. In particular, the decrease in the IF with irradiation in RPV steels can be related to observations of precipitation of solute clusters. 

In alloys and RPV steels with > 0.07wt%Cu, and irradiation temperatures > 200°C, Cu-enriched solute clusters form. At irradiation temperatures > 325 °C, these can grow to >4nm diameter, and probably transform to the equilibrium fee -Cu phase, but at the temperatures and fluence of interest most CECs in irradiated steels will be bcc." Radiation-induced point defects enhance the substitutional solute diffusion rate and enhance the rate of precipitation. In addition, nucleation of CECs appears to be easier in the presence of matrix defects. The nature of the matrix defects on which CECs nucleate is not clearThe relative importance of homogeneous and heterogeneous nucleation of CECs under irradiation is not agreed, although homogeneous nucleation will, naturally, become more likely as the Cu supersaturation increases. ... 

There are two main candidate models which describe the effect of the solute clusters on hardness. The modulus hardening model by Russell and Brown" has been successfully employed for many years to link microstructural and mechanical properties. It predicts very little effect of particle size on hardening at a given volume fraction of precipitates, when particle diameters are in the range 2-4 nm. A more modern model based... 

The precipitate hardening efficiency iOyp/fp) vs fp for solute cluster hardening within the IVAR database, compared with trends derived from the Russell-Brown (RB) and Bacon and Osetsky (B-O) models. o ,p, irradiation-induced yield stress increment associated with precipitation fp, volume fraction of precipitates fp, average precipitate radius derived from SANS measurements. 

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