Alumina: discriminative analysis using 3D correlation of solid-state NMR parameters

Chandran, C. Vinod; Kirschhock, Christine; Radhakrishnan, Sambhu; Taulèlle, Francis; Martens, Johan A.; Breynaert, Eric

doi:10.1039/c8cs00321a

Cited by 107 publications

(125 citation statements)

References 150 publications

(273 reference statements)

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“…[24,30] The range of 27Al chemical shift for various Al‐O x is found to be between −20 to +90 ppm. Al(VI) fold coordination chemical shift in the range between −21 and +37 whereas tetra coordinated Al(IV) isotropic chemical shift in between +35 and +85 ppm . This implies that Al ion diffused from Al(VI) coordination to Al(IV) coordination replacing Si atom from Si‐O−Si covalent linkages at the precursor stage and contributed in the formation of novel geopolymeric precursor phase sodium aluminium oxide and sodium aluminium silicate.…”

Section: Resultssupporting

confidence: 91%

“…This result is in agreement with other reported 27Al spectra of geopolymers . 27Al isotropic chemical shifts in geopolymer are characteristically around 50–70 ppm and their accurate value often depends on number of Si neighbors in the second coordination sphere . Here it is to be noted that four coordination of Al shows crystallographic locations of the Al atom which is not dependent on other chemical forces denotes that Al atom is in tetra coordination with neighboring Si having BO and NBO moieties .…”

Section: Resultsmentioning

confidence: 99%

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Multinuclear MAS NMR Characterization of Fly‐Ash‐Based Advanced Sodium Aluminosilicate Geopolymer: Exploring Solid‐State Reactions

et al. 2020

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Advanced geopolymerization includes concept of just addition of water to ready mixture of dry precursor powder. For exploring the coordination environments of binary glass systems, this work presents multinuclear MAS NMR analysis of advanced geopolymer produced by solid state mechanochemical co-grinding of raw materials. The crystalline and amorphous phases of advanced geopolymer were already characterized with XRD in our previous study. This study focus on multinuclear (29Si, 27Al and 23Na) MAS NMR analysis for exploring the coordination environments of Si/Al/Na nuclei in advanced geopolymer. 29Si, 27Al and 23Na MAS NMR spectra of fly ash, advanced geopolymeric precursor material and advanced geopolymer are qualitatively estimated which enables an understanding of insertion of Al in silicate network ensuing solid state reactions during mechanochemical cogrinding process. By combining the NMR interpretations, it can be suitably said that mechanochemical co-grinding is a feasible way to induce local defects in amorphous Si/Al content which lead to variation in bond angles and variations in Si/Al constellations. Results may be very useful to understand framework connectivity, chemistry and behavior of advanced geopolymers produced by solid state route and the developed advanced geopolymer finds its potential application as "ready to use" cementitious material for large scale commercialization.

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Section: Resultssupporting

confidence: 91%

Section: Resultsmentioning

confidence: 99%

Multinuclear MAS NMR Characterization of Fly‐Ash‐Based Advanced Sodium Aluminosilicate Geopolymer: Exploring Solid‐State Reactions

et al. 2020

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“…In this respect, the complementary use of NMR is especially attractive as it provides an independent quantification of octahedral and tetrahedral sites,a nd av aluable information about the local bonding environment of Al due to the sensitivity of quadrupole nuclear magnetic moment of 27 Al. [22,23] Complementary use of NMR and XRD has been previously applied for quantification of 2D disorder in q-Al 2 O 3 when q-Al 2 O 3 is accommodated in acommon microstructure with d-Al 2 O 3 . [10] For q-Al 2 O 3 alone,t he analysis could be accomplished without the use of XRD since the amount of 2D disorder could be directly linked to the ratio of octahedral/ tetrahedral sites.H owever,i nd-Al 2 O 3 /q-Al 2 O 3 microstructure,the knowledge of volume fractions,asdetermined from XRD,i sr equired.…”

Section: Discussionmentioning

confidence: 99%

Quantification of High‐Temperature Transition Al₂O₃and Their Phase Transformations**

et al. 2020

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High temperature exposure of g-Al2O3 can lead to a series of polymorphic transformations, including the formation of d-Al2O3 and q-Al2O3. Quantification of the microstructure in the d/q-Al2O3 formation range represents a formidable challenge as both phases accommodate a high degree of structural disorder. In this work, we explore the use of XRD recursive stacking formalism for quantification of high temperature transition aluminas. We formulate the recursive stacking methodology for modelling of disorder in d-Al2O3 and twinning in q-Al2O3 and show that explicitly accounting for the disorder is necessary to reliably model the XRD patterns of high temperature transition alumina. In the second part, we use the recursive stacking approach to study phase transformation during high temperature (1050 ºC) treatment. We show that the two different intergrowth modes of d-Al2O3 have different transformation characteristics, and that a significant portion of d-Al2O3 is stabilized with q-Al2O3 even after prolonged high-temperature exposures. In discussions, we outline the limitation of the current XRD approach and discuss a possible multimodal XRD and NMR approach which can improve analysis of complex transition aluminas.

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“…Alumina has multiple phases, but in comparison to other alumina phases, the alpha phase is chemically inert and has a considerable hardness. It is also the most heat resistant phase, stable up to a temperature of 2051 • C; at higher temperatures it melts [9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Usability of Cr-Doped Alumina in Dosimetry

et al. 2019

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Dosimetry is a widespread material science field dealing with detection and quantification of ionizing radiation using electronic processes in materials. One of the main aspects that determines the performance of dosimeters is the type of defects the material contains. Crystalline lattice imperfections are formed around impurity ions, which may have a smaller or larger size, or different oxidation states compared to host ions. In this study, we show what effects Cr impurities have on the luminescent properties of alumina. Porous Al 2 O 3 : Cr microceramics synthesized using the sol-gel method showed a higher thermoluminescence response than a single crystal ruby. We have found that Cr 2 O 3 concentration of 0.2 wt% was optimal; it yielded the highest X-ray luminescence and thermostimulated luminescence readout of all studied additive concentrations added to alumina during synthesis. Our results show that Cr doped alumina could potentially be used as a promising new material for dosimetry of ionizing radiation.

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Alumina: discriminative analysis using 3D correlation of solid-state NMR parameters

Cited by 107 publications

References 150 publications

Multinuclear MAS NMR Characterization of Fly‐Ash‐Based Advanced Sodium Aluminosilicate Geopolymer: Exploring Solid‐State Reactions

Multinuclear MAS NMR Characterization of Fly‐Ash‐Based Advanced Sodium Aluminosilicate Geopolymer: Exploring Solid‐State Reactions

Quantification of High‐Temperature Transition Al₂O₃and Their Phase Transformations**

Usability of Cr-Doped Alumina in Dosimetry

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Alumina: discriminative analysis using 3D correlation of solid-state NMR parameters

Cited by 107 publications

References 150 publications

Multinuclear MAS NMR Characterization of Fly‐Ash‐Based Advanced Sodium Aluminosilicate Geopolymer: Exploring Solid‐State Reactions

Multinuclear MAS NMR Characterization of Fly‐Ash‐Based Advanced Sodium Aluminosilicate Geopolymer: Exploring Solid‐State Reactions

Quantification of High‐Temperature Transition Al2O3and Their Phase Transformations**

Usability of Cr-Doped Alumina in Dosimetry

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Quantification of High‐Temperature Transition Al₂O₃and Their Phase Transformations**