F. L. Toma, L. M. Berger, C. C. Stahr, S. Langner, T. Naumann, Fraunhofer Institute for Material and Beam Technology, Dresden, Germany
In the last years suspension/solution thermal spraying gained an increasing interest for the preparation of finely- or nano-structured sprayed ceramic coatings with promising properties for environmental and other applications. Alumina and titania belong to the materials intensively studied by this new technique of suspension spraying.
This contribution is structured in two parts. In the first a “state of art” of suspension-spraying of alumina and titanium oxide coatings and their properties is described. Focus is made on the electrical properties for Al2O3 deposits and photocatalytic performances of the TiO2 coatings. The microstructures and properties are compared with coatings prepared by conventional spraying from powders. In the second part new experimental results for suspension-sprayed Al2O3 and TiO2 coatings are given. The influence of working parameters (such as spraying conditions, suspension properties, injection mode of the liquid) on the characteristics of the deposits was investigated. In the case of Al2O3 focus was made to retain a high ratio of the initial a-phase, due to its improved properties, e.g. electrical, compared with transitional alumina oxides, usually found for coatings prepared from powders. For TiO2 coatings, the working parameters were chosen in such a way to preserve the photocatalytic active phase, i.e. anatase. The results allow to affirm the potential of the suspension thermal spraying for advanced functional ceramic materials.
Summary: Suspension/solution thermal spraying gained an increasing interest for the preparation of finely- or nano-structured sprayed ceramic coatings with promising properties for environmental and other applications. Alumina and titania belong to the materials intensively studied by this new technique of suspension spraying.
This contribution is structured in two parts. In the first a “state of art” of suspension-spraying of alumina and titanium oxide coatings and their properties is described. Focus is made on the electrical properties for Al2O3 deposits and photocatalytic performances of the TiO2 coatings. The microstructures and properties are compared with coatings prepared by conventional spraying from powders. In the second part new experimental results for suspension-sprayed Al2O3 and TiO2 coatings are given. The influence of working parameters on the characteristics of the deposits was investigated. In the case of Al2O3 focus was made to retain a high ratio of the initial alpha-phase, due to its improved properties, e.g. electrical, compared with transitional alumina oxides, usually found for coatings prepared from powders. For TiO2 coatings, the parameters were chosen in such a way to preserve the photocatalytic active anatase phase. The results allow to affirm the potential of the suspension thermal spraying for advanced functional ceramic materials.
