29Si and 27Al MAS NMR spectroscopy of mullite

Merwin, Lawrence H.; Sebald, Angelika; Rager, H.; Schneider, Hartmut

doi:10.1007/bf00199043

Cited by 98 publications

(56 citation statements)

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“…It should be noted that the resonance at 31 ppm, assigned here predominantly to Al(V), is also within the region in which resonances due to highly distorted Al(IV) within aluminium tetrahedra triclusters in mullite have been observed, which also exhibit a resonance at approximately 3 ppm due to Al(VI) [50]. The broad peak at approximately 3 ppm in the spectra of samples A and B suggests the presence of mullite-like structures within these samples [49], and consequently the peak at 31 ppm is likely due to a contribution of resonances from both Al(V) and highly-distorted Al(IV) species.…”

Section: Postprint Of a Paper Published Insupporting

confidence: 51%

Synthesis of stoichiometrically controlled reactive aluminosilicate and calcium-aluminosilicate powders

et al. 2016

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Section: Postprint Of a Paper Published Insupporting

confidence: 51%

Synthesis of stoichiometrically controlled reactive aluminosilicate and calcium-aluminosilicate powders

et al. 2016

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“…3b) even with 19F decoupling is clearly less than that, which could be due to the presence of other F-containing species. However, incomplete efficiency of 19F decoupling and other effects (MERWIN et al, 1991) could just as we11 account for this observation. Therefore, no quantitative analysis of the 27Al spectra is attempted in this paper.…”

Section: Resultsmentioning

confidence: 86%

Fluorine in silicate glasses: A multinuclear nuclear magnetic resonance study

Schaller

Dingwell

Keppler

et al. 1992

Geochimica et Cosmochimica Acta

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151

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Abstract-Anhydrous nepheline, jadeite, and albite glasses doped with F as well as hydrous F-containing haplogranitic glasses were investigated using "F combined rotation and multiple-pulse spectroscopy; 19F + 29Si cross-polarization/magic angle spinning (MAS); and high-power r9F decoupled 29Si, 23Na, and 27A1 MAS nuclear magnetic resonance methods. Fluorine preferentially coordinates with Al to form octahedral AIF:-complexes in all glasses studied. In addition, F anions bridging two Al cations, units containing octahedral Al coordinated by both 0 and F, or tetrahedral Al-F complexes might be present. The presence of Si-F bonds cannot be entirely ruled out but appears unlikely on the basis of the 19F + 29Si CP/MAS spectra. There is no evidence for any significant coordination of F with alkalis in the glasses studied. 23Na spectra are identical for the samples and their F-free equivalents and the spectra do not change upon decoupling of 19F. The speciation of F in the hydrous and anhydrous glasses appears to be very similar. Over the range of F contents studied (up to 5 wt.%), there seems to be hardly any dependence of F speciation on the concentration of F in the samples. The spectroscopic results explain the decrease of the viscosity of silicate melts with increasing F content by removal of Al from bridging AlO,-units due to complexing with F, which causes depolymerization of the melt. The same mechanism can account for the shift of the eutectic point in the haplogranite system to more feldspar-rich compositions with increasing F content, and for the peraluminous composition of most F-rich granites. Liquid immiscibility in F-rich granitic melts might be caused by formation of (Na,K),AlF, units in the melt with little or no interaction with the silicate component.The presence of F in granitic melts might increase the solubility of high field strength cations by making nonbridging 0 atoms available which form complexes with these cations. INTRODLJCPIONFLUORINE IS ONE OF THE MOST important volatile components of natural magmas, both in mantle-derived melts (e.g., lamproites) and in highly fractionated granitic magmas. Concentrations of several wt.% are reported in high-fluorine rhyolites (CONGDON and NASH, 1988) and in ongonites ( KOVALENKO, 1973). Similar to water, the presence of F strongly reduces the viscosity of silicate melts ( DINGWELL et al., 1985;DINGWELL, 1989) and increases diffusion coefficients ( DINGWELL, 1985). Even small amounts of F in the order of 1 wt.% will therefore significantly change the transport properties, mobility, and eruption behavior of such magmas. The correlation between high concentrations of certain trace elements (Sn, Zr, Nb, Ta, U, Th, etc.) and high F contents in granites and granitic pegmatites (STEMPROK, 1982) has stimulated the investigation of phase equilibria in F-containing granitic systems. MANNING ( 198 1) has shown that F strongly lowers both solidus and liquidus temperatures in the haplogranite system and causes a shift of the eutectic point towards more feldspar-rich...

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“…Although the 27 Al MAS NMR spectra of the activated SFCC specimens are dominated by the resonance associated with Al(IV), a small resonance centered between 2 and 3 ppm is also observed in the spectra. This resonance corresponds to small amounts of Al(VI) from the residual mullite phase (34), identified in the XRD after the activation (Fig. 3).…”

Section: 4mentioning

confidence: 95%

Synthesis of geopolymer from spent FCC: Effect of SiO<sub>2</sub>/Al<sub>2</sub>O<3 and Na2O/SiO2 molar ratios

Trochez¹,

Gutiérrez²,

Rivera³

et al. 2015

Mater. construcc.

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This paper assesses the feasibility of using a spent fluid catalytic cracking catalyst (SFCC) as precursor for the production of geopolymers. The mechanical and structural characterization of alkaliactivated SFCC binders formulated with different overall (activator + solid precursor) SiO 2 /Al 2 O 3 and Na 2 O/ SiO 2 molar ratios are reported. Formation of an aluminosilicate 'geopolymer' gel is observed under all conditions of activation used, along with formation of zeolites. Increased SiO 2 /Al 2 O 3 induces the formation of geopolymers with reduced mechanical strength, for all the Na 2 O/SiO 2 ratios assessed, which is associated with excess silicate species supplied by the activator. This is least significant at increased alkalinity conditions (higher Na 2 O/SiO 2 ratios), as larger extents of reaction of the spent catalyst are achieved. SiO 2 /Al 2 O 3 and Na 2 O/SiO 2 ratios of 2.4 and 0.25, respectively, promote the highest compressive strength (67 MPa). This study elucidates the great potential of using SFCC as precursor to produce sustainable ceramic-like materials via alkali-activation. RESUMEN: Sintesis de geopolimero basado en un catalizador gastado de craqueo catalitico (FCC): Efecto de las relaciones molares SiO 2 /Al2O 3 y Na 2 O/SiO 2 . Este artículo estudia la factibilidad de usar un catalizador gastado del proceso de craqueo (SFCC) para la producción de geopolímeros. Se evalúan las características mecánicas y estructurales de los geopolímeros producidos con diferentes relaciones molares (activador + precursor solido) de SiO 2 /Al 2 O 3 y Na 2 O/SiO 2 . La formación de un gel geopolimérico de tipo aluminosilicato se observa a las diferentes condiciones evaluadas, así como la formación de zeolitas. Un incremento en la relación SiO 2 /Al 2 O 3 genera geopolímeros de baja resistencia mecánica, a las diferentes relaciones molares Na 2 O/SiO 2 evaluadas, como consecuencia del exceso de especies silicato provenientes del activador. Este efecto es menos significativo al incrementar las condiciones de alcalinidad (mayores relaciones Na 2 O/SiO 2 ), ya que un mayor grado de reacción del catalizador gastado es alcanzado. Las relaciones SiO 2 /Al 2 O 3 y Na 2 O/SiO 2 de 2.4 and 0.25, respectivamente, promueven la mayor Resistencia a la compresión (67 MPa). Este estudio muestra el gran potencial de uso del SFCC como precursor en materiales cerámicos obtenidos por activación alcalina.

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29Si and 27Al MAS NMR spectroscopy of mullite

Cited by 98 publications

References 15 publications

Synthesis of stoichiometrically controlled reactive aluminosilicate and calcium-aluminosilicate powders

Synthesis of stoichiometrically controlled reactive aluminosilicate and calcium-aluminosilicate powders

Fluorine in silicate glasses: A multinuclear nuclear magnetic resonance study

Synthesis of geopolymer from spent FCC: Effect of SiO<sub>2</sub>/Al<sub>2</sub>O<3 and Na2O/SiO2 molar ratios

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