High-temperature online damage diagnosis of brittle ceramics in the boiling crisis

The catastrophic strength degradation constrains online damage diagnosis of brittle ceramics in the boiling heat transfer process. Here we present a new avenue to capture the onset time of strength degradation with sparse temperature sensors. The Leidenfrost temperature at 357°C captured from surface heat flux marks as a directed percolation of multiple surface cracking. This reminisces a sudden transition from stable vapor layer in I boiling regime to vapor block in II boiling regime. It reverses the classical view that damage initiates from contacting the water at higher temperature ∼ 1000°C. The hoop of high tensile stress ascents from the edge of sample bottom, agreeing well with the upswing of quench front. This induces a rapidly growing surface macro-cracking for catastrophic strength degradation in the 1st boiling cycle. The destabilized vapor blanket at higher Leidenfrost temperature is confirmed by the transform of contact angle from 105° to 90° to 85° and changed crack patterns from surface macro-cracking to hierarchical inner network. This work guides us to develop an online prevention for mitigating catastrophic failure of brittle ceramics.