Characterization of transitional alumina by solid-state magic angle spinning aluminium NMR

John, C. S.; Alma, N.C.M.; Hays, Gary R.

doi:10.1016/0166-9834(83)80106-7

Cited by 154 publications

(61 citation statements)

References 11 publications

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“…The 58.3 ppm resonance is comparable to the tetrahedral resonance at 57.3 ppm of the starting gel and is interpreted to be due to aluminum present in the amorphous phase. The sometimes observed additional resonance at 9.3 ppm (not shown) is assigned to corundum, a-AlzO3 (John et at., 1983), which has only octahedral aluminum in its structure. Due to the fact that aluminum has a quadrupolar nucleus, the AP v : AI w ratio is at low magnetic field less precise than the Si/AF v ratio based on 29Si NMR.…”

Section: Resultsmentioning

confidence: 99%

Solid-State Nuclear Magnetic Resonance Spectroscopy on Synthetic Ammonium/Aluminum-Saponites

Kloprogge

Breukelaar

Wilson

et al. 1994

Clays and clay miner.

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Abstract--Ammonium-saponite is hydrothermally grown at temperatures below 300~ from a gel with an overall composition corresponding to (NH4)o.6Mg3Alo.,Sia.4Ot0(OH)2. Using 27A1 and 29Si solid-state Magic Angle Spinning NMR techniques it is demonstrated that synthetic ammonium-saponites have a rather constant Si/A1 Iv ratio (~5.5) and an AFV/A1 vl ratio that varies between 1.5 and 3.8. The above ratios are independent of the synthesis temperature, although an increasing amount of Si, I'4, and, to a lesser extent, Al are incorporated in an amorphous phase with increasing temperature. 27A1 MAS-NMR is unable to differentiate between AI at octahedral and AP + at interlayer sites. CEC, XRD, and the inability to swell prove the Al v~ to be mainly on the interlayer sites. Based on the NH4-exchange capacity, X-ray fluorescence, 27A1 and 29Si MAS-NMR, it is possible to calculate a relatively accurate structural formula.

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Section: Resultsmentioning

confidence: 99%

Solid-State Nuclear Magnetic Resonance Spectroscopy on Synthetic Ammonium/Aluminum-Saponites

Kloprogge

Breukelaar

Wilson

et al. 1994

Clays and clay miner.

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“…~-A1203 is formed by calcination of the hydroxides (baye¡ gibbsite) and oxyhydroxide (boehmite) causing dehydroxylation and proceeds via va¡ intermediate aluminas [3,6,86,87]. Calcination produces changes in the structure mirrored in the fraction of Al(6) sites, with MAS NMR spectra giving 0.94 for A10(OH), 0.75 for y-A1203 and 1 for a-A1203 (Fig.…”

Section: The Ai-o-h Systemmentioning

confidence: 99%

“…Calcination produces changes in the structure mirrored in the fraction of Al(6) sites, with MAS NMR spectra giving 0.94 for A10(OH), 0.75 for y-A1203 and 1 for a-A1203 (Fig. lc) [3,86]. The transitional aluminas have close-packed oxygens in a spinel-like structure with aluminium and vacancies dist¡ over the interstifial octahedral and tetrahedral sites.…”

Section: The Ai-o-h Systemmentioning

confidence: 99%

Application of27Al NMR techniques to structure determination in solids

1993

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Abstraer. There have been great improvements in the quality of 27A1 NMR spectra from solids over the last decade. The impact of this technique on structure determination fora wide range of solids is briefly reviewed. Emphasis is placed on the effects arising from the presence of the quadrupolar interaction and strategies that allow unambiguous spectral interpretation. It is demonstrated that in addition to the chemical shift, the quadrupolar interaction itself can be a rich source of local information about solids. The insight obtalned from 27A1 NMR hato atomic level structure often contains surprises, such that previous models of structure and properties have to be reassessed.

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“…Chemical shift ranges for aluminium in different coordinations with oxygen (or hydroxyls) are typically −10 to 20 ppm for octahedrally coordinated aluminium (AlO 6 ), 30 to 40 ppm for pentahedrally coordinated aluminium (AlO 5 ) and 50 to 80 ppm for tetrahedrally coordinated aluminium (AlO 4 ) [16,17]. Several NMR studies explore the transition aluminas [17][18][19][20][21] but the technique has not yet been widely applied to SGAs. The co-existence of the different transition alumina phases and the influence of the second-order quadrupolar interaction cause spectral broadening; however the availability of higher magnetic fields allows some of these problems to be overcome [22].…”

Section: A More Complex Problem?mentioning

confidence: 99%

The nature and impacts of fines in smelter-grade alumina

Perander

Žujović

Kemp

et al. 2009

JOM

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Fines in smelter grade aluminas are recognised as a significant process problem in aluminium smelting. However the understanding of the nature of this fine material and how it impacts on the reduction process are less clearly understood. The combination of new analytical methods such as Variable Pressure Scanning Electron Microscopy and very high field Solid State NMR provide new insights into the spatial distribution of phases within aluminas, and suggest how such fine materials are generated, particularly during calcination in the alumina refinery.

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Characterization of transitional alumina by solid-state magic angle spinning aluminium NMR

Cited by 154 publications

References 11 publications

Solid-State Nuclear Magnetic Resonance Spectroscopy on Synthetic Ammonium/Aluminum-Saponites

Solid-State Nuclear Magnetic Resonance Spectroscopy on Synthetic Ammonium/Aluminum-Saponites

Application of27Al NMR techniques to structure determination in solids

The nature and impacts of fines in smelter-grade alumina

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