Synthesis of Gd2Zr2O7 Coatings Using the Novel Reactive PS-PVD Process

Ceramic topcoats of thermal barrier coatings (TBCs) make it possible to increase the working temperature of the hot sections of jet engines. Yttria-stabilized zirconia oxide (YSZ) is usually used to protect the turbine blades and vanes against high temperature and oxidation. It is necessary to develop new materials which can operate at higher temperatures in a highly oxidizing gas atmosphere. Re2Zr2O7-type pyrochlores are promising YSZ replacements. Usually, they are produced by mixing pure oxides in the calcination process at higher temperatures. In a recent article, the new concept of pyrochlore synthesis during the deposition process was presented. The new technology, called reactive plasma spray physical vapor deposition (reactive PS-PVD), was developed and a Gd2Zr2O7 (GZO) coating was achieved. The reactive PS-PVD process allowed for the use of a mixture of untreated ZrO2 and Gd2O3 powders as reactants, instead of the commercially available gadolinium zirconate powders used in other types of processes. The results of microstructure observations revealed a columnar microstructure in the produced ceramic layer. The phase composition indicated the presence of gadolinium zirconate. Thermal analysis showed a decrease in the thermal conductivity in the range of 700 to 1200 °C of the produced layers, as compared to the layer made of the currently used conventional YSZ.

Reactive Plasma Spray

Thermal spraying is a well-known coating technology with many variations in spraying techniques, feedstock materials and substrate materials. These unique variations increased its industrial applicability in different fields, including aerospace, automotive, chemical process, corrosion protection, and medical applications. However, one of the main limitations of thermal spray is the difficulty of depositing several nitride ceramics directly using conventional techniques. This is due to the decomposition of nitride particles under high temperature without a stable melting phase. This chapter presents reactive plasma spraying (RPS) technology as a promising solution for the in situ fabrication of several nitride ceramic coatings. The main attractive prospects of RPS for fabricating nitride coatings are specifically highlighted. Successful development of various high-temperature nitride coatings, such as AlN, Fe4N and Si3N4, are presented. Process optimization, the relationship between reaction and process parameters and the influence on coatings formation are comprehensively discussed.

Structure and Performance of Ti/TiN/PbO2 Electrodes with Plasma-Sprayed TiN Interlayer

TiN coating as an interlayer in Ti/TiN/PbO2 electrode and PbO2 catalytic layer were fabricated by reactive plasma spray and electro-deposition, respectively. It is shown that because of good effect of the TiN interlayer, the Ti/TiN/PbO2 electrode exhibits a higher oxygen evolution potential and much improved accelerated life compared with the Ti/PbO2 electrode.

Structure and Properties of Ti/TiN/Sb-SnO2 Electrodes with Plasma Sprayed TiN Interlayer

In this paper, TiN coating as an interlayer was fabricated on Ti substrate by reactive plasma spray. Ti/TiN/Sb-SnO2 electrodes were prepared by SOL-GEL method and the influence of the TiN interlayer on the structure, oxygen evolution potential and service life of the electrodes was studied. It was shown that the surface of the Ti/TiN/Sb-SnO2 electrodes is more homogeneous and the oxygen evolution potential and accelerated life are both higher than those of the Ti/Sb-SnO2 electrodes.

Study of Reactive Plasma Sprayed TiN Electrocatalytic Carrier Coatings

In this paper TiN coating as an interlayer was fabricated on Q235 steel substrate by reactive plasma spray method and its microstructure and influences on the performance of the Fe/TiN/PO2 electrode were investigated. It is shown that the TiN coating has a rough surface and layered cross-section structure. The coating consists of main TiN phase and a small quantity of Ti oxides. After heat-treated below 550°C the TiN coating is greatly densified due to the increase of Ti oxides, and however the electric resistance of the Fe/TiN samples is still lower than that of the Ti substrate. For the Fe/TiN/PbO2 electrode a rougher surface and more micropores were observed in the active PbO2 coating than on the surface of the Ti/PbO2 electrode. Due to the presence of the TiN interlayer the Fe/TiN/PbO2 electrode shows an accelerated life of 180h under the test condition, which is much longer than 28min of the Ti/PbO2 electrode.