Talc for Cordierite Ceramics
Finntalc is often used in automotive exhaust catalytic converters. These contain honeycomb cordierite ceramic bodies. The active catalyst, usually a platinum compound, uses the ceramic body as a substrate. Manufacturing of cordierite honeycomb structures aims for high porosity (surface area) yet mechanical strength of thin walls, with a minimum heat expansion coefficient. This is decisive for resistance to temperature changes and fractures. Honeycomb ceramics require highly specialised talc grades that meet a unique combination of requirements. Please contact our technical support for more information.
Heat Expansion Coefficient
Automotive catalytic converters constantly heat up and cool down as the engine starts and stops. This requires cordierite ceramics with the greatest possible resistance to temperature changes and a low heat expansion coefficient. This in turn demands talc with a high purity and low CaO content. Finntalc products are closely monitored and flotation-purified.
For catalytic converters, cordierite with high porosity offers a higher surface area, resulting in improved performance. Best results are achieved with platy, low surface area talcs with an optimized particle size distribution (PSD). In the optimal sintering process, the particles must not be too coarse (i.e. the sieving residue should be very low). The maximum particle size must be lower than the wall thickness of the honeycomb structure (< 45 μm).