Papers by Keyword: SiSiC

Abstract: This paper focuses on an iterative algorithm for setting and attaining particle packing densities by means of different concentrations of a matrix material. The mechanical properties of a product, such as fracture toughness, bending strength and thermal conductivity are directly dependent on the amount of matrix material present. A tape cast friction layer was developed, in order to investigate the dependence of the parameters of the RRSB distribution on concentration of matrix material. The results verify the calculation method of a solid mixture and show a linear dependence of the RRSB particle-parameter n on the concentration of matrix material (SiC-content).

Abstract: In recent years, the need for Silicon carbide (SiC) ceramic arises due to several industrial applications. However, the cost of machining such components is very high. Electrical discharge machining (EDM) serves as the most viable machining technique. In this study, optimum setting of sinking-EDM parameters and mathematical model of siliconized silicon carbide (SiSiC) using aluminum powder mixed dielectric fluid has been developed. Analysis of variance shows that, material removal rate (MRR) increases with high discharge current and low servo voltage, whereas tool wear ratio (TWR) and surface roughness (Ra) decreases with low current and pulse-on time. The effects of design parameters on the machining characteristics were investigated using fractional factorial (resolution V) technique. Confirmatory test was then carried out to validate the models developed.

Abstract: The presented paper shows results from the mechanical design of lightweight mirrors for space applications, where demand for maximum weight loss goes together with demands for sufficient strength, shape accuracy, and surface quality of optical surfaces. The paper illustrates the material properties of different materials, which are often used for manufacturing precise optics. It compares three materials – e.g. optical glass such as NFS-15, optical ceramic such as Zerodur, and Silicon-infiltrated sintered Silicon Carbide – from the point of view of suitability for machining and their mechanical and thermal properties. It also shows the possibility of mass reduction by using different geometries of lightweight structure. Paper shows the results of numerical simulations of specified load-cases and comparison of different lightweight structures and different materials with respect to their strength and stiffness.

Abstract: The Solar-Institute Jülich (SIJ) has initiated the construction of the first and only German solar tower power plant and is now involved in the accompanying research. The power plant for experimental and demonstration purposes in the town of Jülich started supplying electric energy in the beginning of 2008. The central receiver plant features as central innovation an open volumetric receiver, consisting of porous ceramic elements that simultaneously absorb the concentrated sunlight and transfer the heat to ambient air passing through the pores so that an average temperature of 680°C is reached. The subsequent steam cycle generates up to 1.5 MWe. A main field of research at the SIJ is the optimization of the absorber structures. To analyze the capability of new absorber specimens a special test facility was developed and set up in the laboratory. A high-performance near-infrared radiator offers for single test samples a variable and repeatable beam with a power of up to 320 kW/m² peak. The temperatures achieved on the absorber surface can reach more than 1000°C. To suck ambient air through the open absorber - like on the tower - it is mounted on a special blower system. An overview about the test facility and some recent results will be presented.