Geopolymers structure

Geopolymers Structures, processing, properties and industrial applications... 

FTIR-Attenuated Total Reflectance (FTIR-ATR) spectroscopy was used to analyze networking of the geopolymer structure. Ground samples were placed onto the ATR silicon crystal and clamped to obtain good contact. The IR spectra were recorded using an Nexus 670 FT-IR Thermo Nicolet spectrometer with DTGS detector and Smart 7 MIRacle ATR (Thermo Nicolet) adapter with Si plate.. 

Taylor, J., Young, C., Parkes, R., Eglinton,T., and Douglas, A. (1984). Structural relationships in protokerogens and other geopolymers from oxic and anoxic sediments. Org. Geochem. 6,279-286. 

Other sulfur-selective chemical degradation techniques (work in progress) will probably yield additional information to further resolve remaining questions with respect to structure, origin and thermal behaviour of these sulfur-rich geopolymers. 

The resin fractions of organic sulfur-rich bitumens are for a substantial part composed of monomers with linear, isoprenoid, steroid, hopanoid and carotenoid carbon skeletons connected to each other by (poly)sulfide linkages. These structural units may contain additional intramolecular sulfur linkages. This sulfur-rich geopolymer is also formed by sulfur incorporation into functionalised lipids in an intermolecular fashion during early diagenesis. 

Figure 5.25. Changes in the NMR spectrum of metakaolinite on the room temperature formation of sodium polysialate geopolymer and its subsequent service at high temperatures. Note the immediate conversion to tetrahedral A1 upon room-temperature polymerisation, and the thermal stability of the tetrahedral A1 in the geopolymer framework structure. The 13 ppm resonance at 1300°C arises from a small amount of corundum (a-Al203). Based in part on Barbosa et al. (2000).

Na MAS NMR has also been used to study the structure and sodium environment in amorphous sodium aluminosilicate geopolymers, showing that the charge-balancing Na" " is present in a highly hydrated form (Barbosa et al. 2000). When the geopolymer is heated to > 1200°C, the sodium ions lose their hydration water, as evidenced by a shift in the position of the Na resonance from- 5.5 ppm to — 19 ppm, but the amorphous nature of the material is retained. 

Geopolymers are useful inorganic aluminosilicate framework compounds which form and harden at room temperature. Both the aluminium and silicon atoms in their structure occupy tetrahedral sites, with charge balance achieved by the presence of hydrated monovalent ions. NMR has been used to study the changes occurring when a potassium sialate geopolymer is heated to high temperatures. The cog positions... 

Hydrolysis revealed numerous anthropogenic compounds that can be attributed to different technical applications or widespread domestic usages. Within the group of plasticizers the phthalates, which are well-known and ubiquiteous pollutants, were most abundant. Also the plasticizers tributylphosphate and 2,4,4-trimcthylpcntane-l,3-dioldi-/.vo-butyrate occurred in minor concentrations mainly in sample Tl. Due to their molecular structures a non-covalent association of these compounds to the geopolymers has to be assumed. 

Almendros, G., Dorado, J., Gonzales-Vila, F. J., and Martin, F., Pyrolysis of carbohydrate-derived macromolecules It s potential in monitoring the carbohydrate structure of geopolymers, J. Anal. Appl. 

The silica fume offered active Si02 which was profitable for geopolymer production. So the addition of silica fume also improved the mechanical properties of mortars and made structure much denser. But the amount of that should be considered because of its high cost. 

Figure 1 Detailed schematic (left) and idealized three-dimensional (right) structure of geopolymers (sodium ions and water molecules are displayed in balls representation).

Figure 2 Graphical representation of the proposed typical building units and idealized framework structures of the resulting geopolymers [3].

The aluminum atom in this coordination is negatively charged and charge compensated by cations from the alkaline activation solution, such as Na, K, or by artificially introduced cations such as Li ", Ca, Ba ", NH4, or H30 [9,10]. According to the original nomenclature [3], the amorphous to semicrystaUine structure of geopolymers further consists of poly(sialate) (-Si-O-Al-O- PS), poly(sialate-siloxo) (-Si-O-Al-O-Si-0- PSS), and poly(sialate-disiloxo) (-Si-O-Al-O-Si-O-Si-O- PSDS) building blocks (Fig. 2). 

Rational design and optimal synthesis of aluminosilicate systems with controlled physicochemical properties (sorption, separation and/or catalytic activity, etc.) require profound knowledge of the framework structure, consisting of extra-framework cations and surface structural defects [46,47]. However, the comprehensive description of the amorphous and semicrystalline structures of geopolymers is inherently nontrivial therefore, advanced techniques of structural and physicochemical analysis must be applied in combination with the traditional approaches. 

Although much has been done in terms of the structural elucidation of final geopolymers, the details of the geopolymerization reaction, and their impact on the rheology of the reaction paste remain uncertain. In the recent literature, the rheological properties of a geopolymeric paste made with... 

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