High temperature composition-controlled spreading dynamics of volcanic melts

Volcanic ash ingestion during flight leads to the formation of molten aluminosilicate, which spreads over thermal barrier coatings (TBCs), infiltrates their microstructures, and accelerates chemical and mechanical degradation. Such deposits are commonly simulated using a glass generated from the melting of a 4 component mixture of CaO, MgO, Al₂O₃, and SiO₂, so-called “CMAS” for which there exists a large and growing literature. Here, natural volcanic glass beads were synthesized from seven representative volcanic ash compositions via aerodynamic levitation, providing compositionally tailored and morphology-standardized homogeneous analogs for systematic wetting studies. Their molten spreading behavior was investigated on inert platinum‑rhodium substrates to isolate intrinsic wettability dynamics. Four distinct spreading stages were identified, and a predictive viscous flow model was established linking spreading kinetics to the glass network structure. These results provide mechanistic insights into molten volcanic ash infiltration processes and offer predictive strategies for designing ash-resistant TBCs.