Carbon nanotubes and nanohorns in geopolymers: A study on chemical, physical and mechanical properties

This study investigates the effects of carbon nanomaterials (CN), specifically nanohorns (CNHs) and nanotubes (MWCNTs), on geopolymer carbon nanocomposites (GCN). The research investigates 0.2%, 0.5% and 1.0% of CN and two curing conditions to understand their impact on the microstructure, morphology, and performance of GCN. Analytical techniques such as MIP, TGA-DTA, FTIR, Raman, SEM, and EDX are utilized to analyze the nanoadditives in alkali-silicate suspensions, fresh and hardened GCN. Ultrasonication is important for achieving better dispersion of MWCNTs, while CNH disperses more easily. Both MWCNTs and CNHs enhance flexural strength by up to around 58% and 44%, respectively, and reduce crack formation compared to the pristine geopolymer. Hydrothermal curing, despite leading to higher porosity, improves flexural strength due to increased geopolymerisation. The formation of a cross-polymerized network with oxo bonds and the release of water during the process contribute to increased strength and porosity, respectively.