Nanokomposite für die Herstellung oxidischer Matrices keramischer Faserverbundwerkstoffe

Nanocomposites for the preparation of oxide/oxide ceramic matrix composites Ceramic suspensions for the fabrication of ceramic matrix composites are usually produced from submicron powders. Taking the electrophoretic infiltration of Nextel? 720‐ and Nextel? 650‐ fabrics as an example, it is shown that the use of nanopowders and nanocomposites can be advantageous for the preparation of matrices, too. Coinfiltration of submicron α‐alumina and a second nanoscale phase (zirconia) allows the preparation of a (α‐alumina + zirconia) structural composit matrix. Functional nanocomposites of alumina and silica facilitate the formation and densification of mullite at temperatures below the the maximum temperature for short‐term heat treatment of the reinforcement fibre.     

Elektrophoretische Abscheidung zur Herstellung von faserverstärkten Keramik‐ und Glasmatrix‐Verbundwerkstoffen — Eine Übersicht

In this paper, we review the application of the electrophoretic deposition (EPD) technique in the fabrication of fibre reinforced composites, with particular emphasis on composites with glass and ceramic matrices containing metallic or ceramic fibre fabric reinforcement. The review covers research published in the last 10 years. EPD has been used to infiltrate preforms with tight fibre weave architectures using different nano‐sized ceramic particles, including silica and boehmite sols, as well as dual‐component sols of mullite composition. The principles of the EPD technique are briefly explained and various factors affecting the EPD behaviour of ceramic sols and their optimisation to obtain high infiltration of the fibre preforms are considered. Overall, the analysis of the published data and our own results demonstrate that EPD, being simple and inexpensive, provides an attractive alternative for ceramic infiltration and coating of fiber fabrics, even if they exhibit tight fibre weave architectures.     

Potentialunterstützte Herstellung von Metall‐Keramik‐Verbundschichten

Potential assisted fabrication of metal‐ceramic composite coatings A possibility to produce uniform metal‐ceramic composite coatings with a high content of ceramic particles up to 60 vol.% will be presented in this study. This method includes a combination of electrophoretic deposition and electrolytic deposition by several steps. A yttria‐stabilized zirconia coating (Tosoh TZ‐8Y) was first electrophoretically deposited on a ferritic steel plate and then sintered by 1100 °C to an open porous layer. In the next step nickel was electrodeposited into the pores of the layer. By a final annealing step it was possible to improve the bonding of the composit coating on the substrate by diffusion of the metal components.     

Herstellung und komplexe Charakterisierung von Metall‐Keramik‐Verbundschichten

Formation and characterization of metal‐ceramic coatings The influence of the formation process and used materials of metal‐ceramic coatings on the structural properties of the deposited layers were investigated and optimized to increase the mechanical properties. There the deposition of the metal‐ceramic‐layers occurred by a combination of electrophoretic and galvanic deposition with siloxane as bonding compound. Layers with a high ceramic content were successfully created. As ceramic components commercial silicon carbide and silicon nitride were used. Nickel and Copper respectively were applied as metal component to fill the porous ceramic structure with the aim to increase the strength of the layers, where nevertheless a pre nickel‐plating or pre cupper plating of the steel substrate X6Cr17 before ceramic component deposition had to be done to increase the adhesion of the layers. The layer characterization was made by optical microscopy and scanning and transmission electron microscopy, where especially the bonding of the single particles by the siloxane was in evidence.     

Aufreinigung von Nano- und Submikronpartikeln durch präparative Gelelektrophorese

The preparative gel electrophoresis enables the separation of nano- and submicron particles based on different electrophoretic mobilities. In this contribution, we show that a fractionation not only by particle size is possible, but also by surface charge/chemistry and morphology. Whilst this method, in analogy to its application in biotechnology, is yet restricted to small quantities, possibilities for an increase of the particle throughput as well as for a continuous separation are shown.