Influence of Yttrium on the Thermal Stability of Ti-Al-N Thin Films

Ti(1-x)Al(x)N coated tools are commonly used in high-speed machining, where the cutting edge of an end-mill or insert is exposed to temperatures up to 1100 degrees C. Here, we investigate the effect of Yttrium addition on the thermal stability of Ti(1-x)Al(x)N coatings. Reactive DC magnetron sputtering of powder metallurgically prepared Ti(0.50)Al(0.50), Ti(0.49)Al(0.49)Y(0.02), and Ti(0.46)Al(0.46)Y(0.08) targets result in the formation of single-phase cubic (c) Ti(0.45)Al(0.55)N, binary cubic/wurtzite c/w-Ti(0.41)Al(0.57)Y(0.02)N and singe-phase w-Ti(0.38)Al(0.54)Y(0.08)N coatings. Using pulsed DC reactive magnetron sputtering for the Ti(0.49)Al(0.49)Y(0.02) target allows preparing single-phase c-Ti(0.46)Al(0.52)Y(0.02)N coatings. By employing thermal analyses in combination with X-ray diffraction and transmission electron microscopy investigations of as deposited and annealed (in He atmosphere) samples, we revealed that Y effectively retards the decomposition of the Ti(1-x-y)Al(x)Y(y)N solid-solution to higher temperatures and promotes the precipitation of c-TiN, c-YN, and w-AlN. Due to their different microstructure and morphology already in the as deposited state, the hardness of the coatings decreases from similar to 35 to 22 GPa with increasing Y-content and increasing wurtzite phase fraction. Highest peak hardness of similar to 38 GPa is obtained for the Y-free c-Ti(0.45)Al(0.55)N coating after annealing at T(a) = 950 degrees C, due to spinodal decomposition. After annealing above 1000 degrees C the highest hardness is obtained for the 2 mol % YN containing c-Ti(0.46)Al(0.52)Y(0.02)N coating with similar to 29 and 28 GPa for T(a) = 1150 and 1200 degrees C, respectively

Notes on Amandinea Petermannii Comb.nov. (Physciaceae) from Antarctica

The new combination Amandinea petermannii (Hue) Matzer, Mayrh. & Scheidegger; is proposed. The taxonomy, morphology, anatomy, chemistry, ecology and distribution of this lichen are discussed. Rinodina convoluta D. C. Lindsay is synonym of A. petermanni

Influence of tailored MLI for complex surface geometries on heat transfer

Complex, non-developable surfaces require a tailored multi-layer insulation (MLI) for lowest heat load. The most experiments showing the heat transfer through MLI are performed under quasi-ideal conditions determining the principle insulation quality. But the surface to be insulated in real cryostats implies feed-throughs and other non-developable surface parts. The thermal performance of MLI is degraded significantly at cutting points. To investigate this degrading effect a LN$_{2}$-filled cylinder with a diameter of 219 mm and a length of 1820 mm was insulated with MLI and the heat load was measured by means of calorimetry. In addition the heat load to an insulated cylinder with eighteen branches was measured. Both cylinders have the same surface of 1.37 m$^{2}$ for a comparison of the results. This article describes the experiments with different ways of tailoring the MLI for the cylinder with branches and discusses their results. It was shown that the cutting points at the branches have a significant degrading influence on the thermal performance of MLI