Microstructure and pore structure of one-part geopolymer incorporating electrolytic copper powder and graphene oxide

This study investigates the effect of electrolytic copper powder (ECP) and graphene oxide (GO) on geopolymerisation and microstructural characterisation of one-part alkali-activated material (AAM), which strongly correlates to its thermal-mechanical performance. Various analytical techniques were employed to evaluate the chemical modifications, reaction kinetics, microstructure and pore structure induced by these additives, including X-ray diffraction (XRD), fourier transform infrared (FTIR), isothermal calorimetry, scanning electron microscopy coupling with energy dispersive spectroscopy (SEM/EDS), nitrogen adsorption-desorption (NAD) and nuclear magnetic resonance (NMR). The result findings show that the dissolved Cu 2+ ions affect Al–O linkages at Al IV sites in the geopolymer framework. The presence of ECP and GO also reduce the physically-bound water within intralayer and promote the development of highly-crosslinked gel networks characterised by Q 4 (3Al) sites. ECP in forms of dissolved ions exhibits the adsorption mechanism onto C-(N)-A-S-H gels, while the remaining ECP particles with coral-like shape serve as micro-aggregate filling in the pores. The incorporation of ECP and GO accelerates the geopolymerisation with further gel formation and densification (reduced both total porosity and pore size). Both forms of ECP significantly enhance the thermal conductivity of the geopolymer, and this effect is further amplified by GO inclusion due to higher densification. Overall, the effect of ECP and GO significantly enhances the thermal and mechanical properties of one-part AAM, making them a promising approach for advanced materials such as thermal energy storage (TES) materials. • ECP can serve as micro-aggregate, thus boost the thermal conductivity of geopolymer. • ECP induces more pore refinement rather than a reduction in total porosity of geopolymer. • ECP and GO accelerates the geopolymerisation, densification and Si/Al molar ratio. • Dissolved Cu 2+ ions adsorb onto C-(N)-A-S-H gels and affect Al–O linkages at Al IV sites. • ECP and GO reduce the intralayer water and promote the crosslinked gel at Q 4 (3Al) sites.