Glass Ceramics & Composites

  SEM image of a glass ceramic Copyright: GHI

Glass ceramics are used in many fields of application in our daily lives due to their highly adjustable material properties. Among other things, the coefficient of thermal expansion, the strength and the optical properties can be controlled by the formation of one or more crystalline phases. The properties of the glass-ceramic depend on the properties and the proportion of the crystalline phase in the glass-ceramic.

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Intrinsic Functionalized Glass Ceramics

Glass sample placed inside of a plate capacitor Copyright: GHI Glass sample placed inside of a plate capacitor with schematic drawing of diffusion channels.

The crystallization of glass enables to adjust material properties such as the thermal expansion coefficient, strength or optical properties. Changes in the properties depend on the individual properties and proportion of the crystalline phase in the glass ceramic. Through the establishment of chemical gradients or the alignment of crystals by means of an electric field before or during the crystallization process, anisotropic properties should be induced in the material, allowing the glass ceramic to be functionalized. In the field of basic research, a new understanding of ion diffusion in glasses and glass-ceramics as well as crystallization should be obtained. In addition, the results should be used to produce glass ceramics with specific properties such as high strength, a defined coefficient of thermal expansion and defined surfaces.

 

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Laser Processing of Glasses and Glass Ceramics

Surface image of a sample Copyright: GHI Laser-scanning image of a sample

Glass can be machined by many different methods. A new type of method is the processing of glass using laser techniques. Depending on the choice of the laser source, laser parameterization and the selected glass compositions, different applications can be realized. By the adjustment and selection of the optimal material-laser interactions, various machining processes such as laser drilling and cutting, laser soldering, laser welding, laser polishing or complex 3D machining processes can be achieved. Thus, the fields of application are very widespread. Currently, the department is focusing on the ablative laser processing of dental glass ceramics in order to reduce the expensive tool wear of existing CAD-CAM systems. A further research project deals with the polishing of glasses and glass ceramics in order to reduce the surface roughness by means of optical finishing.