IR spectroscopic and catalytic characterization of the acidity of imogolite-based systems

Bonelli, Barbara; Bottero, I.; Ballarini, Nicola; Passeri, Sauro; Cavani, Fabrizio; Garrone, Edoardo

doi:10.1016/j.jcat.2009.03.003

Cited by 70 publications

(109 citation statements)

References 42 publications

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“…This structure gives rise to three kinds of pores (Ackerman et al 1993;Wilson et al 2002) shown in Scheme 1: (i) pores A are intra-tube pores, 1.0 nm in diameter, lined by silanols, the related A surface being very hydrophilic and able to interact with probes like H 2 O, NH 3 and CO (Bonelli et al 2009;2013); (ii) pores B, 0.3-0.4 nm wide, are those among the three aligned NTs within a bundle, hardly accessible even to small molecules, like water (Ackerman et al 1993;Wilson et al 2002); (iii) pores C are disordered slit (meso)pores among bundles, the surface of which may interact with larger molecules, like phenol (Bonelli et al 2009) and 1,3,5-triethylbenzene (Bonelli et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Al/Fe isomorphic substitution versus Fe2O3 clusters formation in Fe-doped aluminosilicate nanotubes (imogolite)

et al. 2015

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Textural, magnetic and spectroscopic properties are reported of Fe-doped aluminosilicate nanotubes (NTs) of the imogolite type, IMO, with nominal composition (OH) 3 Al 2-x Fe x O 3 SiOH (x = 0, 0.025, 0.050). Samples were obtained by either direct synthesis (Fe-0.025-IMO, Fe-0.050-IMO) or postsynthesis loading (Fe-L-IMO). The Fe content was either 1.4 wt% (both Fe-0.050-IMO and Fe-L-IMO) or 0.7 wt% (Fe-0.025-IMO). Textural properties were characterized by High-Resolution Transmission Electron Microscopy, X-ray diffraction and N 2 adsorption/ desorption isotherms at 77 K. The presence of different iron species was studied by magnetic moment measurements and three spectroscopies: Mössbauer, UV-Vis and electron paramagnetic resonance, respectively. Fe 3? /Al 3? isomorphic substitution (IS) at octahedral sites at the external surface of NTs is the main process occurring by direct synthesis at low Fe loadings, giving rise to the formation of isolated high-spin Fe 3? sites. Higher loadings give rise, besides IS, to the formation of Fe 2 O 3 clusters. IS occurs up to a limit of Al/Fe atomic ratio of ca. 60 (corresponding to x = 0.032). A fraction of the magnetism related to NCs is pinned by the surface anisotropy; also, clusters are magnetically interacting with each other. Post-synthesis loading leads to a system rather close to that obtained by direct synthesis, involving both IS and cluster formations. Slightly larger clusters than with direct synthesis samples, however, are formed. The

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Section: Introductionmentioning

confidence: 99%

Al/Fe isomorphic substitution versus Fe2O3 clusters formation in Fe-doped aluminosilicate nanotubes (imogolite)

et al. 2015

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“…Among the existing nanomaterials, only graphene possesses mechanical strength comparable to that of CNTs. 45,46 The external surface of CNTs generally requires modification before being incorporated into another material for the fabrication of composites; however, the hydroxyl groups on the outer surface of AlSiNTs make them amenable to aqueous-phase processing and compatible with soft hydrophilic materials, such as poly-(vinyl alcohol). Thus far, this has greatly limited their applicability in large-scale systems and devices.…”

Section: Introductionmentioning

confidence: 99%

Relationships among the structural topology, bond strength, and mechanical properties of single-walled aluminosilicate nanotubes

2015

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Carbon nanotubes (CNTs) are regarded as small but strong due to their nanoscale microstructure and high mechanical strength (Young's modulus exceeds 1000 GPa). A longstanding question has been whether there exist other nanotube materials with mechanical properties as good as those of CNTs. In this study, we investigated the mechanical properties of single-walled aluminosilicate nanotubes (AlSiNTs) using a multiscale computational method and then conducted a comparison with single-walled carbon nanotubes (SWCNTs). By comparing the potential energy estimated from molecular and macroscopic material mechanics, we were able to model the chemical bonds as beam elements for the nanoscale continuum modeling. This method allowed for simulated mechanical tests (tensile, bending, and torsion) with minimum computational resources for deducing their Young's modulus and shear modulus. The proposed approach also enabled the creation of hypothetical nanotubes to elucidate the relative contributions of bond strength and nanotube structural topology to overall nanotube mechanical strength. Our results indicated that it is the structural topology rather than bond strength that dominates the mechanical properties of the nanotubes. Finally, we investigated the relationship between the structural topology and the mechanical properties by analyzing the von Mises stress distribution in the nanotubes. The proposed methodology proved effective in rationalizing differences in the mechanical properties of AlSiNTs and SWCNTs. Furthermore, this approach could be applied to the exploration of new high-strength nanotube materials.

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“…Unlike CNTs, the diameter of AlSiNTs can be precisely controlled and monodispersed . The microporosity of AlSiNTs has attracted the attention of researchers for use in catalysis, molecular storage, molecular transport, and molecular separation . AlSiNTs have been developed to improve their electronic, optical, mechanical, and rheological characteristics .…”

Section: Figurementioning

confidence: 99%

Microwave‐Assisted Synthesis of Highly Monodispersed Single‐Walled Alunminosilicate Nanotubes

et al. 2016

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The synthesis of single‐walled aluminosilicate nanotubes (AlSiNTs) generally requires conductive heating over a period of 4 days. This paper outlines a novel microwave‐assisted method for the synthesis of AlSiNTs, which achieves yields on par with conventional methods in just 12 hours. The AlSiNTs obtained using the proposed method are much shorter (average length of 140 nm) than those synthesized in a reactor subjected to conductive heating in an oil bath (average length of 480 nm). The proposed synthesis method produces a product with highly monodispersed length distribution (100 – 200 nm), compared to those obtained from a conductively‐heated reactor (50 – 950 nm). We applied suspensions of the resulting AlSiNTs to produce thin films via spin coating. The thin films cast from microwaved AlSiNTs yielded a far smoother top surface with uniform surface morphology. This can be attributed to the shorter average length and the narrower length distribution of the AlSiNTs in the casting solution.

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IR spectroscopic and catalytic characterization of the acidity of imogolite-based systems

Cited by 70 publications

References 42 publications

Al/Fe isomorphic substitution versus Fe2O3 clusters formation in Fe-doped aluminosilicate nanotubes (imogolite)

Al/Fe isomorphic substitution versus Fe2O3 clusters formation in Fe-doped aluminosilicate nanotubes (imogolite)

Relationships among the structural topology, bond strength, and mechanical properties of single-walled aluminosilicate nanotubes

Microwave‐Assisted Synthesis of Highly Monodispersed Single‐Walled Alunminosilicate Nanotubes

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