Evaluation of the densification mechanism during realisation of dense ceramic layers at room temperature via the Aerosol Deposition Method

• Applicant: Professor Dr. Kyle Grant Webber, since 7/2015
• Subject Area: Coating and Surface Technology ; Synthesis and Properties of Functional Materials
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 266855577

Ceramic layers are often applied for improving various functions of workpieces (protection against wear, reducing friction, etc, and are also part of complex components of the multilayer technology, e.g. in microelectronics. The main disadvantage during the fabrication of dense ceramic layers is the necessity to sinter them at high temperatures. This impedes the combination with other material classes (metals and polymers). One method to fabricate dense ceramic layers at room temperature is the Aerosol Deposition method, which was developed by Jun Akedo in the 1990s. During Aerosol Deposition an aerosol is generated by passing a gas flow through loose powder. The aerosol is then accelerated towards a substrate and forms a dense layer during impact of the particles. Such layers have been fabricated from various ceramic materials. However, the densification mechanism has not been clarified sufficiently yet. Thus, in this project the layer formation during Aerosol Deposition and thereby the underlying densification mechanisms shall be analysed and clarified to finally achieve new layer qualities and composites at low fabrication temperatures. For this, after the installation of the Aerosol Deposition method, dense ceramic layers shall be fabricated at room temperature, initially. During this step a special focus will be set at the aerosol itself and its properties. After evaluation of suitable processing parameters for the aerosol generation and the successful layer formation the densification mechanism shall be investigated. For this, a working hypothesis of the densification mechanism was proposed: Following the densification mechanisms of other techniques that do not incorporate sintering, like Cold Gas Spraying and Shock Compaction, it is supposed that the densification during Aerosol Deposition is based on a combination of breaking and reorganisation of particles during impact - intensified by the impact of following particles -, a local transition of part of the kinetic to thermal energy at the particle surface (local melting of the outermost surface), and finally, a plastic deformation of the ceramic particles. To prove this hypothesis, systematic evaluation of the influence of various processing parameters, characterisation especially of the interfaces and the analysis of the microstructure at different layer forming stages shall be carried out. Clarification of the densification mechanism is important to be able to influence and even tailor the layer properties during deposition. This would set the basis for applying the Aerosol Deposition method to functional multilayer structures and turn the Aerosol Deposition method to a promising future technology.

• DFG Programme: Research Grants
• Major Instrumentation: Aerosol-Deposition-Anlage
• Instrumentation Group: 2180 Maschinen für Oberflächenbehandlung (Elektropolieren, Galvanisieren, Lackieren, Sandstrahlen)
• Ehemalige Antragstellerin: Dr.-Ing. Ulrike Deisinger, until 7/2015