Silica

Setzer, Constanze; Essche, Gonda van; Pryor, Neil

doi:10.1002/9783527618286.ch23a

Cited by 9 publications

(3 citation statements)

References 84 publications

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“…Stabilization prevents particles from condensing with other particles, but it does not preclude continued condensation between particles and monomeric silicate species. The formation of a uniform pore structure in aluminosilicate particles through sol−gel chemistry is also commonly observed . The particle size can then be easily modified by changing the reaction temperature, curing time, and silicate ratio, as has also been observed in fly-ash-based geopolymer gels.…”

Section: Resultsmentioning

confidence: 86%

Effect of Curing Temperature and Silicate Concentration on Fly-Ash-Based Geopolymerization

Sindhunata

Deventer

Lukey

et al. 2006

Ind. Eng. Chem. Res.

308

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The development of the pore structure of geopolymers synthesized from class F fly ash was studied using electron microscopy and porosimetry. Fly-ash-based geopolymer can be classified as a mesoporous aluminosilicate material, with a Si/Al composition varying from 1.51 to 2.24. The Si/Al composition and pore structure of fly-ash-based geopolymer vary depending on the curing temperature and the silicate ratio of the activating solutions (SiO2/M2O, M = Na or K). A higher Si/Al ratio and finer pores are obtained in geopolymers synthesized at higher temperature and silicate ratios. Elevating the curing temperature increases the extent and rate of reaction, shown through an increase in mesopore volume, surface area, and an accelerated setting time. The kinetics appears to be temperature-controlled only before the material is hardened. Very high silicate ratios (SiO2/M2O ≥ 2.0) are also believed to slow the reactions. The pore structure of K-based geopolymer is more susceptible to change in temperature than that of Na-based geopolymer.

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Section: Resultsmentioning

confidence: 86%

Effect of Curing Temperature and Silicate Concentration on Fly-Ash-Based Geopolymerization

Sindhunata

Deventer

Lukey

et al. 2006

Ind. Eng. Chem. Res.

308

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“…The BET surface area ( S BET ) of 483 m 2 /g, to the best of our knowledge, is one of the largest reported so far for chalcogenide gels. When compared on a per mole basis, the silica equivalence is 810 m 2 /g which is comparable to porous silica prepared by wet methods …”

mentioning

confidence: 84%

Ion-Exchangeable Cobalt Polysulfide Chalcogel

Shafaei‐Fallah

Rothenberger

et al. 2011

J. Am. Chem. Soc.

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“…In the synthesis of aluminosilicate gels and glasses, the porosity and other physicochemical properties can be tailored by immersing wet gels in various alkaline solutions, − salt solutions, , and organic solvents. , Regarding the use of alkaline solutions, it is found that the alteration of pore structure in wet or dry silica gels is largely dependent on the immersion time, concentration, and pH. ,− A longer immersion time results in an increase in pore size and decrease in specific surface area by eliminating narrower pores. , Aging or washing at a near-neutral pH results in a porous gel with a higher pore volume and lower surface area than at lower pH. The alteration of pore structure in porous silica gels follows an Ostwald ripening mechanism .…”

Section: Introductionmentioning

confidence: 99%

Structural Evolution of Fly Ash Based Geopolymers in Alkaline Environments

Sindhunata

Provis

Lukey

et al. 2008

Ind. Eng. Chem. Res.

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The effects of immersion in alkaline solutions on the gel structure and pore network of fly ash based geopolymers are investigated. Immersion in carbonate or hydroxide solutions of up to pH 14 results in very little leaching of framework components (Si or Al) from the geopolymer gel, and a largely unchanged mesoporous gel structure. Higher concentrations, up to 8 M NaOH, cause more damage to the gel framework as species are leached into solution and the pore network collapses. Crystallization of small quantities of zeolites from the initially X-ray amorphous gel is also observed. The zeolitic products formed are in general the same products that are observed in geopolymers cured at elevated temperatures for extended periods of time, suggesting that the reactions taking place during alkaline immersion are to some extent a continuation of the initial geopolymerization process.

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Silica

Cited by 9 publications

References 84 publications

Effect of Curing Temperature and Silicate Concentration on Fly-Ash-Based Geopolymerization

Effect of Curing Temperature and Silicate Concentration on Fly-Ash-Based Geopolymerization

Ion-Exchangeable Cobalt Polysulfide Chalcogel

Structural Evolution of Fly Ash Based Geopolymers in Alkaline Environments

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