Research

We develop machine-learning interatomic potentials (MLIPs) and apply them to follow how preceramic polymers turn into ceramics. Our Si–C–O–H and Si–C–N–H potentials simulate pyrolysis up to 2,500 K and predict diffusion, thermal expansion and fracture of the resulting ceramics.

Polymer-derived ceramics often contain nanometre-sized domains of “free” carbon that control stiffness, conductivity and the Raman spectrum. We compute how composition, density and carbon morphology set the elastic moduli, how Raman bands change with flake size, and how strongly graphene adheres to the embedding host matrix.

Density functional theory calculations help us to predict which phases appear at extreme pressure and temperature. We computed nitrogen-rich phase diagrams for various metal–nitrogen systems, recently predicted a new spinel-type Al₄C₃ to appear above 7 GPa, and work with partners who make new materials in high-pressure experiments.

We follow the conversion of gels and polymers to ceramics with thermogravimetry, mass spectrometry and IR spectroscopy. One porous SiCO gel proved hyper-reactive by picking up trace oxygen from 99.999% argon, with a whopping 4% mass gain. Moreover, semiquantitative TG-MS lets us reconstruct a gel’s composition from the gases it releases.

The solvent and the cross-linker decide how pores form in polymer-derived SiCO aerogels. We synthesize polymethylhydrosiloxane gels and, together with Micromeritics, developed differential hysteresis scanning of gas sorption to map how the pores are connected.

Hafnium- and zirconium-based ceramics withstand temperatures above 2,000 °C and are candidates for hypersonic flight. Cross-linking the commercial precursor SHP-199 with TEOS, we make HfSiCO monoliths and fibers with 92% ceramic yield that remain intact up to 1,600 °C.