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Thin films of the recently discovered intermetallic superconducting compound YNi2B2C have been grown in situ using a magnetron sputtering technique. High quality, c-axis oriented, films were obtained on MgO substrates held at about 800 °C during the sputtering process. The best films showed maximum Tc=15.25 K (onset), a transition width of ≊0.3 K, a room-temperature resistivity of 53±3 μΩ cm, a residual resistivity ratio up to ≊5.4, a low-temperature critical current Jc≊105 A/cm2 and Bc2≥6 T. Superconducting films were also obtained on sapphire and LaAlO3 substrates.

We report comparative XPS (hν=1253.6 eV) core level (Zr 3d; C 1s; O 1s; Fe 2p; V 2p) results from two relevant gettering alloys: Zr2Fe and Zr57V36Fe7. The samples were studied as-received (after in-air fracturing of bulk ingots) and after different annealing treatments (up to 700 °C) performed in ultrahigh vacuum. With increasing temperature both alloys show a progressive dissolution of Zr oxides, an increase in the metallic character of the surface, the gradual loss of C based adsorbates, and a progressive increase in the surface Zr content and at the expense of the C concentration. At temperatures in the range 300–550 °C a fraction of the C atoms form metallic carbides. OH-based groups are depleted from the surface at low temperatures (200 °C), resulting in a sizable decrease of the near surface O content, while a nearly constant O concentration is found at intermediate and high temperatures. Only minor changes are observed for the near surface concentrations of Fe in Zr2Fe and Fe and V in Zr57V36Fe7 as a function of temperature. The two alloys show strong differences in the activation kinetics of these changes, with surface metallization being initiated at lower temperatures and proceeding faster in Zr57V36Fe7. Metallic carbides are found to almost completely dissolve in Zr57V36Fe7 at 600–700 °C, while they are retained even at high temperatures in Zr2Fe. The kinetic differences determined via XPS are consistent with the differences in gettering behavior of Zr2Fe and Zr57V36Fe7.

Polyurethane foam is the preferred insulator material in a wide range of appliances such as refrigerators and freezers. The recent phase out of CFC-11 has however decreased its insulation performance due to the need to adopt environmentally more benign blowing agents, such as HCFCs and hydrocarbons, all having higher gas thermal conductivity. This represents a serious drawback since specific regulations to reduce the energy consumption in refrigerators have been issued in recent years, and even more demanding reductions are under debate and expected to be applied worldwide by the turn of the century. In response to these requirements, Vacuum Insulated Panels (VIPs) technology has been studied and developed. Suitable components, filler, bag and a getter to maintain the necessary vacuum, have to be selected to ensure the high super-insulation properties which can be exhibited by VIPs. Among various core materials for VIPs, open cell foams present specific advantages in terms of performance, weight, processability and cost. In the present paper, the recent developments in the VIP technology are reviewed and discussed focusing the attention on the open cell polyurethane. The various gas sources deteriorating the vacuum during the panel life have been experimentally determined and evaluated by means of outgassing, permeation and gas analysis measurements on VIP components and finished devices. A suitable getter system able to cope with the gas load and to ensure vacuum performance and reliability is also described.

The near-surface atomic composition and the character of chemical bond in two nonevaporable gettering alloys have been investigated via core level (Zr 3d, Fe 2p, V 2p, O 1s, C 1s) photoemission. The samples have been measured in UHV after in-air fracturing and various annealing steps (up to 850 °C). For T>400 °C a progressive and sizeable decrease of the near surface C content along with an increase in the Zr concentration is observed in both alloys. An annealing induced Zr enrichment at the surface is found, the metallic atomic concentrations being significantly far from the nominal bulk stoichiometry. The annealing induces a strong evolution in the chemical bonds, the metallic species being completely oxidized in in-air fractured samples while a metallic character progressively emerges at increasing temperatures. Surface metallization proceeds faster in Zr2Fe than in the V-containing getter.