PLASMA SPUTTERED OXIDE FILMS ON HYBRID CAPTIVE DEVICE FOR REUSABLE TPS FOR RE-ENTRY SYSTEMS

摘要

A reusable Thermal protection system has to satisfy several specific requirements. One of the most critical is the control of the oxidation of the materials during the re-entry step. This result may be reached through a proper balance between bulk materials with good mechanical properties and coatings with good thermal barrier properties. Carbon composites (SiC) are nowadays the most suitable candidates as they have both good thermal resistance and good thermal stability which preserve the mechanical properties at high temperatures. However a further improvement is needed: the development of a coating which allows to optimize both the oxidation protection and the substrate adhesion. Plasma sputtered oxide films of valve-metals (Ta, Nb, Zr, Ti) deposited on hybrid captive device are proposed in this study as a possible solution to the above-mentioned specifications. The exposed experimental findings refer to ZrO_2 nanostructured thin films deposited in a RF (13.56MHz) magnetron sputtering reactor, starting from Zr targets (purity 99,99%) in plasma fed with Ar and O_2 in different experimental conditions. After the deposition, some specimens were submitted to annealing performed for 5 min in air at different temperatures in the range 600-900 °C in order to increase grain growth. Chemical and morphological characterization of deposited film was carried out by means of a Field Emission Scanning Electron Microscopy (Supra40 Zeiss Microscope) equipped with an Energy Disperse Spectrometer. In addition on Carbon/Carbon composite samples, as received and coated, dilatometric characterizations have been performed.