Flash Surface-Engineered Floating Proppants with Decoupled Density and Strength.

Lightweight particulate materials with high mechanical robustness are widely desired yet remain difficult to produce through scalable processing. This challenge is particularly evident for hydraulic fracturing proppants, where low density favors suspension and long-distance transport, whereas high crush resistance is required to preserve fracture conductivity under elevated closure stresses. Here, a flash surface-engineering strategy is reported to convert waste-derived cenospheres into lightweight, mechanically reinforced particles through ultrafast electrothermal processing. Transient flash heating induces spatially confined carbothermal conversion, forming a conformal silicon carbide (SiC)-reinforced shell while preserving the hollow architecture. Incorporation of a polymer-assisted carbon precursor promotes uniform interfacial contact and continuous SiC shell growth under flash conditions. The resulting particles exhibit a ∼55% decrease in crush ratio, from 19.5% to 8.8% at 27.6 MPa, while retaining transport and packed-bed flow characteristics comparable to those of conventional sand-based proppants. The transient and diffusion-limited reaction confines reinforcement to the particle surface without bulk densification, thereby mitigating the conventional trade-off between low density and mechanical robustness. Together, these results demonstrate that surface-confined SiC conversion can mechanically reinforce waste-derived hollow particles while retaining their low density and application-relevant transport characteristics.