Thermally sprayed Zn2TiO4 heating coatings with adaptive electrothermal properties

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In the preliminary works an alternative to metallic heating layers was developed in thermally sprayed semiconducting heating layers on titanium dioxide base and their operability was demonstrated. As advantages are to be called the more homogeneous heat distribution on the component surface and the low amount of workload involved by full-flat coating. The limitation of the operating temperature on 300 °C is the most essential disadvantage. With an overstepping it comes to oxidation and irreversible increase of the electrical resistance what amounts to a destruction of the heating layer. With zinc titanate (Zn2TiO4) a better temperature stability should be achieved and therefore a new generation in thermally sprayed heating layer systems be created. With the help of the properties and ranges of application of Zn2TiO4 the temperature stability was demonstrated. An application as a thermal spray coating is known up to now only in the lab graduation and needs intensive development work. The planned use of suspension and precursor is justified by their advantages concerning a thick and homogeneous coating micro structure.An essential advantage which should be examined is the specific modification of the electric-thermal coating properties by donors. The comprehensive development works of the appli-cants with suspension spraying (development of: feeder technology, injectors, suspensions and coatings) form the base of new Zn2TiO4-heating layers to whose electric-thermal properties can be modified by donors straight.It is necessary for the development works to win a scientific funded base for the understanding of the interaction. This concerns in the first step to examine the development of suspen-sion and precursor and in the second step the coating development around the influence of the spray processes and in the third step to analyze and to understand the influencing of donors on the resultant coating properties. It is a matter the following hypotheses to clear up:A) Coatings from Zn2TiO4 can be produced of suspension and precursor by thermal spraying.B) Coatings from Zn2TiO4 are thermally more stable than TiOx or TiO2 / 20Cr2O3.C) Doping from MnO and NiO influence the electric-thermal properties of Zn2TiO4-heating layers (e.g. resistivity and thermal behavior).D) By the use of precursors the donors can be produced in a mixing crystal in the layer. E) By the denser coating structure to be expected with the S-HVOF can with the suspension spraying better electrical properties are achieved than with the S-APS. This material-scientific-technological base is to be compiled the object of the applied research project. In the later course of the project a substitution of MnO-or NiO-donors is possible to prove the set goal of a longtime stable, adaptable heating layer.