Compressive strength as a screening tool for quality control of tubular honeycomb ceramic filters

Strength-based screening is proposed to complement the filtration-based screening for the quality control of tubular honeycomb ceramic filters. It is first shown how compressive failure loads can be measured, converted to failure strengths, and analysed with Weibull plots, and then this method is applied to industrial SiC filters at their four stages of the production chain demonstrating that toughness, not porosity or dominant pore size, determines the strength of these filters. Specifically, it was found that the green supports are the weakest (∼10.5 MPa strength) because they are simple compacts of particles weakly bound by only a dehydrated polymer. The sintered supports are much stronger (∼68.3 MPa strength) because they have developed a cohesive macroporous skeleton with inter-particle necks. Unexpectedly, the membrane-coated supports are weaker (∼56.7 MPa strength) than the sintered supports because the membrane sintering cycle embrittles the inter-particle necks, which dominates over the strengthening compressive stresses (∼16 MPa) introduced by the membrane layer. Lastly, the commercial filters finally put on the market are the strongest (∼122.3 MPa strength) because their oxidation cycle increases the cohesion of the macroporous skeleton. To conclude, the usefulness of the strength-based screening for the quality control of tubular ceramic filters is discussed.