Papers by Author: Ralf Riedel

Abstract: The ultra-high pressure and temperature synthesis of spinel silicon nitride and germanium nitride on the one hand as well as the successful synthesis of tin nitride at ambient pressure on the other hand have caused an enormous impact on both basic science and technological development of advanced nitrides. Aim and scope of the research in this field is to synthesize novel nitrides for structural and functional applications. High presssure nitrides may combine ultra-high hardness with high thermal stability in terms of decomposition in different environments and are expected to show interesting optoelectronic properties. Here, the state of the art and the progress in the field of novel advanced nitrides and related materials synthesized reproducibly under high pressure are reviewed.

Abstract: Metal particles were embedded in a silicon carbonitride (SiCN) matrix, derived from the commercially available polysilazane Ceraset®. Metal powders, such as Fe, Mn, Co, Ni, were mixed and milled with pre-cross-linked polysilazane and subsequent pyrolysis. The metals act as active fillers to increase the density of composite. The phases and microstructures of metal/ceramic composites were studied using XRD, SEM and EDS. The magnetic property was measured with Magnetic Property Measurement System at –196oC and 27oC. The results show that there were two main domains in composites, one was metal-rich domain and another was metal-poor domain. The reaction compound between metal and matrix had great effect on the magnetic properties of composites, filled with different metals.

Abstract: The metal elements, such as Fe, Mn, Co, Ni, Ni-Mn, Co-Mn and Fe-Mn, were mixed and milled with pre-cross-linked polysilazane Ceraset® and subsequent pyrolysis. The metals act as active fillers to increase the density of composite. The phases and microstructures of metal/ceramic composites were studied using XRD, SEM and EDS, and the magnetic property was measured with Magnetic Property Measurement System at –196oC. The results show that there are two main domains in composites, one is metal-rich domain and another is metal-poor domain. The density of composite is larger than that of polymer-derived SiCN ceramic, but the hardness varies little. The compound generated by the reaction between metal and matrix has great effect on the magnetic properties of composites, which are filled with different metals.