Self-diffusion in α-Al₂O₃I. Aluminium diffusion in single crystals

Mass-Transfer Mechanism of Alumina Ceramics under Oxygen Potential Gradients at High Temperatures

“…15,16) In this case, the appropriate tracer 26 Al has a very low specific activity and an extremely long half-life of 7:2 Â 10 5 years, making it very difficult to perform radiotracer diffusion experiments. Nychka et al, 10) then, deduced the aluminum grain boundary flux through an Al 2 O 3 scale during oxidation of alumina forming alloys by measuring the scale thickness, which consisted of double layers, such as equiaxial grains produced by outward diffusion of aluminum and underlying columnar grains developed by inward diffusion of oxygen.…”

“…Messaoudi et al had reported that the oxygen grain boundary diffusion coefficients are determined from the transport through the growing Al 2 O 3 scale. 13) This is done by oxidizing the alumina forming alloys in an 16 O 2 atmosphere, further oxidizing them in 18 O 2 and then determining the 18 O distribution in the -Al 2 O 3 scale using SIMS. The oxygen grain boundary diffusion coefficients determined by this procedure are larger than those determined from extrapolated diffusion data for polycrystalline -Al 2 O 3 annealed in a homogeneous environment without any oxygen potential gradients.…”

Silver diffusion in commercial QE22 magnesium alloy with Saffil fiber reinforcement

“…As can be seen in Table 1, the values of D eff are greater than those of D v , except at 728 K. If we suppose that volume diffusion in alumina in general is much slower [16] than in QE22, it may be concluded that the difference between D eff and D v is due to the fast diffusion along interface Saffil/matrix. Belova and Murch [17] have proposed the following relation between the effective diffusivity D eff in two phases and interphase boundary diffusivity D i …”

Control of Polymorphism and Mass-Transfer in Al2O3 Scale Formed by Oxidation of Alumina-Forming Alloys

“…Thus, oxygen grain boundary diffusivity in polycrystalline alumina under oxygen potential gradients is apparently different from that in a homogeneous environment. On the other hand, there has been only two reports of aluminum lattice diffusion coefficients determined using SIMS (Paladino et al, 1962, Le Gall et al, 1994. In this case, the appropriate tracer, 26 Al, has a very low specific activity and an extremely long half-life of 7.2×10 5 years, making it very difficult to perform radiotracer diffusion experiments.…”