Foam concrete nanocomposites synergistic integration of ultrasonically exfoliated two-dimensional vermiculite nanoplatelets and expanded vermiculite: Mechanical and thermal performance optimisation

This study developed a novel two-dimensional nanoplatelet filler (thickness ≪ diameter in morphology), which significantly improved the mechanical performance of foam concrete. Expanded vermiculite (EV), characterized as a lightweight thermal insulator with porous three-dimensional multilayers microstructure, was exfoliated into two-dimensional vermiculite-based nanoplatelets (NV) filler. A scalable ultrasonic exfoliation methodology was proposed for the preparation of the NV filler by adopting ultrasound as the delamination force and water as the liquid phase. NV filler for the first time was introduced into foam concrete as nano-reinforcement. In this study, the ultrasonication times of 15 min, 30 min, 60 min, and 90 min were studied to determine the optimal delamination effectiveness. The scanning electron images and transmission electron microscopy identified that 60 min sonication effectively produced well-delaminated NV with a smooth surface and reduced wrinkling. The compressive strength, thermal conductivity, infra thermal observation, porosity, and microstructural morphology were systematically investigated on the nanocomposites containing different fractions of NV filler (0.5 % and 1 % under 15min–90min sonication, respectively), EV (10%–20 %) and various NV/EV combined proportions. The nanocomposite containing 1 %/90min of NV fillers exhibited the most significant enhancement in compressive strength by 27.6 %, corresponding to the improved microstructure and porosity. Of all co-existence NV/EV-derived nanocomposites, the sample containing 1 %/60min NV and 50 % EV suggested the lowest thermal conductivity of 0.304 W/(m K).