From bulk to porous structures: Tailoring monoclinic SrAl₂Si₂O₈ ceramic by geopolymer precursor technique

Abstract

In this paper, monoclinic SrAl2Si2O8 ceramics with porous structures were prepared based on ion‐exchanged geopolymer precursor technique. Micron‐level pores with a homogeneous pore‐size distribution were introduced into the inorganic framework using foaming agents. The results demonstrated that the apparent density, pore‐size distribution and specific surface area of porous geopolymer precursors can be well‐engineered via tailoring the category and concentration of the foaming agent. After being treated at 900°C, hexagonal SrAl2Si2O8 first‐crystallized from the amorphous geopolymer matrix and then gradually converted into monoclinic SrAl2Si2O8 between 1100°C and 1200°C. The resulting monoclinic SrAl2Si2O8 ceramics maintained the porous structures during high‐temperature treatments and exhibited high porosity, specific surface area, and compressive strength. The aforementioned strategy not only achieves monoclinic SrAl2Si2O8 ceramics with well‐defined and robust microstructures, but also provides an alternative route to prepare other porous ceramics, with potential applications in fields of high‐temperature filters, adsorbents, and heterogeneous catalysis.

Geopolymers made using organic bases. Part I: Synthesis and atomic structure

“…It has also been observed that the new cations may not fully replace the original alkali cations 20,26 or that several cycles (typically 12+ hours each) may be needed to achieve complete exchange. [22][23][24] An alternative approach to ceramic synthesis by a castable route is the so-called "inorganic gel-casting method." [35][36][37][38][39][40] It is not a geopolymer-based process but is somewhat similar.…”

Open-cell mullite ceramic foams derived from porous geopolymer precursors with tailored porosity

“…On the other hand, nepheline [28][29][30], leucite [31][32][33], and pollucite [34,35] ceramics can be easily obtained from them after high-temperature sintering above 800 . Furthermore, alkaline metal ions can be ℃ replaced by other cations (e.g., strontium [36], ammonium [37], and copper [38]). Due to low cost and broad availability of the raw materials including solid waste, easy pore formation, high yield, and low shrinkage of the resulting materials [39,40], the method of converting geopolymers to ceramics has attracted increasing attention, especially for the porous ceramics, such as glass ceramic foams [41], porous SrAl 2 Si 2 O 8 ceramics [36], open-cell leucite ceramics [24], porous h-AlN/SiCbased ceramics [42], porous mullite [21], porous cordierite [43], and monoclinic-celsian ceramics [44].…”

Effect of high temperature on the mechanical properties of hierarchical porous cenosphere/geopolymer composite foams

“…Furthermore, foams with highly open cell structure are usually regarded as good candidates in adsorption and catalyst fields 12‐13 . Besides, porous SrAl 2 Si 2 O 8 can also be obtained based on ion‐exchanged geopolymer precursor technique 2 …”

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Geopolymer, a type of inorganic amorphous aluminosilicate polymer, is prepared by mixing aluminosilicate materials (such as fly ash, metakaolin, slag, etc) from alkaline activation reaction. [1][2][3][4] Recently, geopolymer foams have gained increasing interest since they exhibit low density, low CO 2 emissions, high mechanical strength and thermal stability, etc. Moreover, geopolymer shows good chemical resistance like ceramic foam.

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“…[12][13] Besides, porous SrAl 2 Si 2 O 8 can also be obtained based on ion-exchanged geopolymer precursor technique. 2 Generally, chemical or physical foaming approaches are used to generate porous components in geopolymers. [14][15] Recently, Cantarel et al 16 reported a type of geopolymer composite foam templated with hexadecane as organic dispersed phase.…”