Improvement of the high-temperature oxidation resistance of Zr alloy cladding by surface modification with aluminium-containing ternary carbide coatings

Alumina-forming MAX phase ternary carbides are being considered as protective coatings on zirconium alloys as occident tolerant fuel (ATF) cladding because of their resistivity against high-temperature steam oxidation during occident scenarios. This study attempted to synthesize three types of Al-containing MAX phase carbides (Ti2AlC, Cr2AlC and Zr2AlC) as coatings on Zircaloy-4 substrates via deposition of elemental nanoscale multilayer thin films using magnetron sputtering, and subsequent thermal annealing in argon. Formation of Ti2AlC and Cr2AlC MAX hases was confirmed after annealing at 800°C and 550°C, respectively, while growth of Zr(Al)C carbide rather than Zr2AlC AX phase was observed in the Zr-C-Al system. Oxidation of the three coated samples at 1000°C in steam for 1 hour evealed no protective effect of the Ti2AlC and Zr(Al)C coatings with significant spallation and cracking. The Cr2AlC oatings possess superior oxidation resistance and self-healing capability with a thin and dense α-Al2O3 layer growth on the surface, which shows good promise as a candidate for coated ATF claddings

Parameterization invariance and shape equations of elastic axisymmetric vesicles

The issue of different parameterizations of the axisymmetric vesicle shape addressed by Hu Jian-Guo and Ou-Yang Zhong-Can [ Phys.Rev. E {\bf 47} (1993) 461 ] is reassesed, especially as it transpires through the corresponding Euler - Lagrange equations of the associated elastic energy functional. It is argued that for regular, smooth contours of vesicles with spherical topology, different parameterizations of the surface are equivalent and that the corresponding Euler - Lagrange equations are in essence the same. If, however, one allows for discontinuous (higher) derivatives of the contour line at the pole, the differently parameterized Euler - Lagrange equations cease to be equivalent and describe different physical problems. It nevertheless appears to be true that the elastic energy corresponding to smooth contours remains a global minimum.Comment: 10 pages, latex, one figure include