Dielectric response of alkali aluminosilicate hydrate and silico alumino phosphate network present in metakaolin–graphene oxide geopolymer: A comparative study

• Published in: Inorganic chemistry communications 2024-03, Vol.161, p.112036, Article 112036
• Main Authors: Karuppaiyan, Janani, Jeyalakshmi, R.
• Format: Article
• Language: English
• Subjects: Dielectric properties; Graphene oxide; Metakaolin geopolymer; Raman spectroscopy; TEM
• ISSN: 1387-7003; 1879-0259
• DOI: 10.1016/j.inoche.2024.112036

[Display omitted] •Structural investigation of GO-reinforced alkali and acid metakaolin composite reported by MASNMR.•Al-rich gel in Si-Q4 (3Al) in formed in G-MA than in control MA.•Structural variations influence the dielectric properties of the composites.•Relatively low dielectric constant is observed in MP due to H+ ion transfer.•Conductivity is decreased by the addition of GO in both MA and MP. Metakaolin-based geopolymeric composites are regarded as potentially useful materials for a number of applications because of the strength of networks present in them. In the present study, the binding network of aluminosilicate hydrate or silico alumino phosphate network of metakaolin is activated using sodium silicate (MA) and phosphoric acid (MP), respectively, and reinforced with an optimised dose of graphene oxide (GO) for dielectric applications. The sheet-like structure of graphene oxide present in the network was confirmed by transmission electron microscopic (TEM) analysis and the selected area diffraction (SAD) pattern showed relatively diffuse scattering spots. The alignment in the growth of N-A-S-H and S-A-P gels with fibrillar products at various points on the GO surface was observed in scanning electron microscopic (SEM) images. The reinforcement with GO improves the compressive strength of both types of geopolymers (G-MA, G-MP) by 20 % compared to that of control specimens (MA, MP). This could be due to the acceleration of the reaction with a higher amount of N-A-S-H gel in MA and a synergistic formation of silicoalumino phosphate and aluminium phosphate in MP. GO intercalation was confirmed from the intense peaks of D band of GO at 1300–1450 cm−1 in the Raman spectrum in MA and MP as well as different Q1–4Si environments pertaining to the geopolymeric network. The impedance spectroscopy was used to investigate electrochemical properties like static high-frequency dielectric permittivity, suppressed electrical conductivity, reduced loss tangent, increased resistivity and modulus. Dielectric constant (K) calculated for was found to be in the order G-MP