Nb Interlayer Research Articles

Electron transport and magnetic penetration depth in niobium-silicon multilayers

Thin niobium-silicon multilayers have been sputtered with niobium thicknesses less than the coherence length and silicon thicknesses that allow tunneling between layers. The multilayer structure has been confirmed by X-ray diffraction, and the films have been electrically characterized with respect to T/sub c/ and J/sub c/. For constant Nb thickness, both T/sub c/ and J/sub c/ increase with decreasing Si thickness, indicating increased coupling between the Nb layers. When a multilayer forms the barrier in a tunnel structure, the resulting I(V) characteristic resembles that for a series of single-barrier junctions, and further evidence of Nb interlayer coupling is observed. These multilayers have also been incorporated as the base in several tunnel structures in order to measure the multilayer penetration depth via the magnetic field dependence of I/sub c/. Preliminary results indicate that the theoretically predicted enhancement of penetration depth in a multilayer does occur. >

MAGNETOOPTIC MEASUREMENTS ON Gd/Nb/Gd SANDWICHES

Gd/Nb/Gd layered films were grown epitaxially in UHV by electron-beam evaporation on a 500-Å-thick Nb buffer layer (substrate: sapphire [Formula: see text]). The deposition temperature was 750° C for the Nb buffer layer and 300° C for the other films. The Gd films grow in (0001) and the Nb films in (110) orientation as determined by X-ray measurements. The magnetization curves of the Gd/Nb/Gd sandwiches (with a protective 50 Å Nb layer on top) were measured with the transverse magnetooptic Kerr-effect. The coercitive field of the sandwiches oscillates as a function of the Nb thickness indicative of an interaction between the two Gd films (thickness 100 Å) through the nonmagnetic Nb interlayer. These oscillations have a period of about 11 ± 2 Å (typical of the magnetic coupling through nonmagnetic transition-metal layers) and were observed for more than three periods in the Nb thickness range from 15 to 55 Å.

Microstructure of interface regions and mechanical properties of Ti/Al 2O 3 and Ti-alloy/Al 2O 3 joints for dental implants

Titanium and alumina are very well suited as constituents of dental metal/ceramic implants because of their excellent biocompatibility and their special chemical and mechanical properties which can be exploited to tailor composite implant structures. However, prior attempts to join pure titanium without any intermediate layer to alumina ceramic lead to unsatisfactory results mainly due to thermal expansion mismatch between both materials. Therefore we used recently developed Ti alloys containing 30% wt Ta or 40% wt Nb for manufacturing dental implants. Moreover, we studied two alternative methods to join pure titanium with alumina using intermediate layers to reduce internal stresses within the joint caused by thermal expansion mismatch. We examined the interface region of these joints by metallographic, mechanical, analytical, and electron microscopy methods. Additionally, a comparison of the properties of the hitherto investigated types of joints with a view of their applicability in dental implants is given. Promising results were obtained for Tilalumina joints with Nb interlayers. The studies are continuing.