Multiphase diffusion in the systems Fe-Sn and Si-Sn

We have investigated phase relations and diffusion phenomena in the Fe-Sn and Ni-Sn systems in the temperature ranges 300 to 600 C and 580 to 800 C, respectively. The homogeneity regions and stability ranges ofthe phases found by the diffusion couple technique were confirmed by the analysis of equilibrated alloys. In order to determine the mobility of each element in the various phases, marker experiments have been carried out. The intermetallic compounds formed by diffusion reveal a fibre texture with the fibre axis parallel to the diffusion direction

Growth of silicides in Ni-Si and Ni-SiC bulk diffusion couples

In this work, the integrated diffusion coefficient, D'-int' is used to describe the growth kinetics of silicides in Ni -Si and Ni-SiC diffusion couples. The integrated diffusion coefficients are determined from planar diffusion couple experiments for all intermetallic phases of the binary Ni-Si system between 1073 and 1173 K. For the growth of NisSi2 'an activation energy of 180 ± 30 kJjmol (1.9 ± 0.3 eV) was found. The position of the Kirkendall plane revealed that Ni is the only diffusing species in Ni3 Si and NisSi2. In NiSi2, Ni and Si are equally mobile. The activation energy for the interdiffusion in the Ni(Si) solid solution, measured between 1093 and 1423 K, is 250 ± 10 kJjmol (2.6 ± 0.1 eV) and is independent of the Si-concentration

The solid state reaction between Cu3P and silicon or germanium

The phase relations in low-phosphorus parts of the ternary systems Cu-Si-P and Cu-Ge-P have been determined for alloys annealed in evacuated capsules at 500°C. The reaction of Cu3P with silicon in diffusion couples that have been annealed in vacuum, is never faster than the reaction between copper and silicon. Cu3Si and phosphorus vapour are formed during the reaction. A peculiar morphology, that of isolated Cu3Si columns separated by large gaps, develops when the reaction is hindered. When a diffusion couple is annealed in a closed capsule, Cu3Si and presumably SiP are formed. The reaction between Cu3P and germanium takes place at a rate comparable with that of the copper-germanium reaction and leads to the formation of Cu3Ge and phosphorus vapour. Because of plastic deformation of Cu3Ge no peculiar morphology of the reaction layer was observed

Interacties tussen metaal en keramiek

Een beschrijving wordt gegeven van het onderzoeksprogramma metaalkeramiek interacties van het CTK binnen het kader van het IOP-TK. Het gebruik van breukmechanische methoden naast de gebruikelijke sterktemetingen wordt aanbevolen. Enkele eerste resultaten aan SiC-Ni en SiC-Fe laten zien dat er uitsluitend diffusie van Ni en Fe optreedt en niet zoals in de literatuur beschreven wederzijdse diffusie

Periodic formation of FeSi bands in diffusion couples Fe (15 wt.% Si) - Zn

During the reaction in Fe(15 wt.% Si)-Zn diffusion couples at temperatures between 623 and 723 K thin regularly spaced parallel bands containing very small FeSi precipitates are observed throughout the 6 and ~ reaction layers. The periodic nature of this effect is strongly reminiscent of the well-known Liesegang phenomenon. A detailed analysis of our results with respect to the principles underlying the Liesegang mechanism, however, shows that such a mechanism cannot explain the observed phenomenon in our case. A more probable explanation is found in the action of shear and tenSile stresses in the diffusion couple which lead to a periodic release ofthe continuously formed FeSi precipitates from the Fe(15 wt.% Si) substrate. Preliminary results obtained with substrates of varying thicknesses are strongly in favour of the latter explanation