Refractory products or “refractories” are a large family of materials whose compositions range from from pure oxide to complex mixtures containing carbide (SiC), silicon metal and graphite. Material analysis of refractories is preferably done by means of X-ray fluorescence analysis (XRF)
Fire-restistant ceramics are used for the manufacturing of high-temperature reactors. In the industrial sector, they are used e.g. in foundries and steel mills. To private users, the good old tiled stove is certainly known. The material’s extraordinary high requirements can only be fulfilled if the elementary composition is exactly correct. Therefore, the raw materials are systematically analysed and the concentration of the relevant elements is identified. With X-ray fluorescence analysis, this task can be carried out fast and reliably every day.
Material analysis of refractories
Oxide products are analyzed in general in a high temperature fusion treatment. This process belongs to our routine tests.
For more complex compositions containing so-called platinum poisons such as graphite, SiC, or silicon, the metallic materials can be melted only after complete oxidation. Thus, the components such as silicon remain only as silicon oxide. A distinction of the different chemical bonds is no longer possible and requires further analyzation.
Material analysis of refractories at terrachem
At terrachem we decided to go new ways. The material should be analyzed without substantial chemical changes.
- The free carbon content is determined by means of thermogravimetry.
- The carbon-free sample is pressed without pressing aids.
- By means of X-ray Fluorescence Analysis (XRF) all elements are determined. The carbon is converted to SiC.
- SIO2 is directly analyzed by regarding characteristic peaks.
- The total silicon minus the proportions of SiC and SiO2 determines the proportion of Si-metal. In order to hedge, the Si-metal can be analyzed using a diffractometer or by regarding the formation of hydrogen.
- A final plausibility check can be made by regarding all parameters which should sum up to 100%.
Furthermore, the measured and the calculated amount of oxygen should be equal.
This way of material analysis of refractories can be used in order to measure the purity of SiC. Using this method it is possible to directly determine the SiO2 proportion. The subsequent plausibility check is carried out as mentioned above.