Nanocomposites and nanomaterials

Influence of vacuum annealing on the dispersion of thin double niobium-nickel films deposited onto oxide ceramic materials
Gab I.I.1, Stetsyuk T.V.1, Fesenko O.M.2, Shakhnin D.B.3
1 Frantsevich Institute for Materials Science Problems of NAS of Ukraine, 
3 Krzhyzhanovskogo st., Kyiv, 03142, Ukraine.
E-mail: gab@ipms.kiev.ua
2 Transfer Technology Department, Institute of Physics of the NAS of Ukraine. Prospect Nauki, 46, Kyiv-03039, Ukraine. 
3 University "Ukraine", 23 L’vivska st., Kyiv, 03115, Ukraine. 

In modern technology there is a need for the production of permanent vacuum-tight precision ceramic joints with an ultra-thin seam. Such joints can be made by brazing or pressure welding of metallized ceramic parts. This purpose can be achieved by application onto ceramic surfaces of double metal films, one part of which is 100 – 200 nm thickness and consists of an adhesion-active metal (e.g. Ti, Nb etc.), and the other layer is slightly thicker (1 – 3 microns) and serves as a solder (e.g. Cu, Ni etc.) ensuring joining of metallized ceramic materials during brazing or pressure welding with a fine brazed seam  (2 – 4 microns thickness).
In this work, specimens were used made of leucosapphire, alumina and dioxide-zirconium ceramics and metallized with a 150 nm niobium nanofilm and then atop, by a 1,5 – micron nickel film serving as a soldering metal for ceramic samples joining. 
Since, during the joining process, the samples can be heated to a temperature up to 1000 °C or even more, it would be well to study the behavior of such double films during annealing. In this work, we have studied the behavior of the double niobiunm-nickel film deposited onto the oxide samples mentioned above during their annealing in a vacuum at temperatures up to 1000 °C with different exposition time at each temperature (from 5 up to 20 minutes). It was found that the initial solid films on all oxide samples undergo only a slight change during their annealing up to 1000 °C. However, after the annealing at 1100 °C, these films begin to disperse rather quickly and after 20 min annealing at 1200 °C they were separated onto fragments which covered about 75% of the samples surface.
According to our study results kinetic curves of the investigated thin double metallic films decomposition have been built, using which one can determine the basic process parameters (temperature and exposition time at this temperature) for brazing or pressure welding of ceramic materials.