Geopolymers and Geopolymer-Derived Composites

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Abstract

Geopolymers are aluminosilicate inorganic polymers, cured at ambient temperatures from a liquid precursor. The strained nature of the 5-coordination aluminum cation polyhedra is identified as the reason why metakaolin-based geopolymer ceramics are made from solution, rather than with high temperature diffusion. The microstructure of alkali based geopolymers is nanoporous and nanoparticulate. This enables carbothermal reduction and carbothermal nitridation under flowing argon or nitrogen, in the presence of excess carbon to produce nanoparticles of silicon carbide (SiC), silicon nitride (Si3N4) or SiAlON from geopolymers. Crystallized geopolymer composites have been developed having tailorable thermal expansion coefficients. Intrinsic mechanical properties as well as those of geopolymer composites are summarized for composites containing both ceramic, polymeric as well as biological reinforcements. Amorphous glass frit-containing geopolymer composites undergo amorphous self-healing upon heating above the melting point of the glass. Amorphous self-healed geopolymer (ASH-G) refers to composites below ~950°C where the geopolymer is still amorphous, while ASH-C denotes amorphous self-healed ceramic where the geopolymer matrix has crystallized.

Original languageEnglish (US)
Title of host publicationEncyclopedia of Materials
Subtitle of host publicationTechnical Ceramics and Glasses
EditorsMichael Pomeroy
PublisherElsevier
Pages424-438
Number of pages15
Volume1
ISBN (Electronic)9780128222331
ISBN (Print)9780128185421
DOIs
StatePublished - May 24 2021

Keywords

  • Alkali activated cements
  • Alumino-disilicate phosphates
  • Amorphous self-healed ceramic
  • Amorphous self-healed geopolymer
  • Basalt fiber reinforcement
  • Ceramic or biological reinforcements
  • Compressive strength
  • Flexural strength
  • Geopolymer-derived silicon carbide, silicon nitride, SiAlONs
  • Geopolymers and geopolymer composites
  • Mechanical properties
  • Nanoporous nanoparticulate microstructure
  • Synchrotron X-ray diffraction
  • Tailorable thermal expansions
  • Tensile strength

ASJC Scopus subject areas

  • General Engineering
  • General Materials Science

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