Steffen Dudczig

Carbon Containing Castables and More

In terms of this work formulations of carbon bonded castables based on new binder approaches and nanoadditions will be demonstrated. The new binder system allows the manufacturing of water based magnesia carbon castables with the same properties and chemistry of pressed magnesia carbon bricks. This binder can be also applied in oxide castables offering them high refractoriness and workability during processing. According to the workability nano-additions improve significantly the spreading diameter of carbon castables and as a result their flowability.

Thermal Shock and Thermo-Mechanical Behavior of Carbon-Reduced and Carbon-Free Refractories

The thermal shock behaviour of novel carbon-reduced refractories with maximum grain size of 1 mm was investigated. A wedge splitting test for small specimen geometries (max. 40 × 40 × 20 mm 3 ) was successfully implemented with different loading configurations to determine “work of fracture” and thermal shock parameters. Additionally, heating-up thermal shock tests were performed with an electron beam facility. The addition of 2.5 wt% ZrO 2 and TiO 2 to Al 2 O 3 refractories appears to improve their thermal shock resistance due to microstructural changes that reduce brittleness and inhibit critical crack growth. However, a phase transition of ZrO 2 affects the properties at elevated temperature. For another pure alumina refractory, no geometry-independent value for the work of fracture could be obtained for the sample geometry used, which is probably related to the formation of a large interaction zone of the fracture surfaces. Al 2 O 3 -C materials with addition of semi-conductive Si and nanoparticles revealed a strong effect of the pressing direction on the work of fracture. However, the thermal shock parameter R’’’’ was hardly affected by the different additives. Furthermore, thermal shock tests using the electron beam facility JUDITH 1 did not indicate any significant differences in the damage pattern of the different Al 2 O 3 -C materials.

Influence of the Microstructure on the Fracture Behavior of Carbon Bonded Alumina

Carbon bonded alumina (Al2O3-C) in various compositions are developed for the production of open cell filters, which are used for melt metal filtration processes [. The Small Punch Test (SPT) is used to determine the mechanical properties of such materials. Previous investigations showed two different types of fracture behavior [2,, which can be distinguished by typical features of the load deflection curves of the SPT. This paper clarifies this behavior by examining the fracture surfaces using scanning electron microscopy (SEM).