Mechanisms of Structural Reordering During Thermal Transformation of Aluminogermanate Imogolite Nanotubes

Abstract

Metal oxide aluminosilicate and aluminogermanate nanotubes, called imogolite nanotubes, are custom made nanotubes with controlled diameter, morphology and organization. These nanotubes undergo major structural changes at high temperatures. Here, we report a complete analysis of the structural transformation of single and double-walled aluminogermanate nanotubes, organized or not in bundles, up to 800 • C. Complementary X-ray scattering and spectroscopy experiments were performed. The evolution of both Al and Ge atoms coordination during the transformation process was studied in-situ. Quantitative analysis of X-ray absorption spectra reveals that the dehydroxylation of nanotubes leads to intermediate stages of 'metaimogolite', which differ in the coordination of the aluminium atoms. A mechanism explaining the major structural reorganization is proposed based on atomic jump processes.

Controllable One-Dimensional Growth of Metal–Organic Frameworks Based on Uncarved Halloysite Nanotubes as High-Efficiency Solar-Fenton Catalysts

“…Halloysite nanotubes (HNTs, Al 2 Si 2 O 5 (OH) 4 · n H 2 O) are natural clay minerals with a typical 1D nanotube structure, which have a length and outer diameters of about 300–800 and 50–70 nm, respectively. , The external tube surface of HNTs is mainly composed of Si–OH groups while the inner lumen surface composition is Al–OH. As a consequence of this, the inner surface is positively charged because of the protonation of Al–OH groups, and the Si–OH groups cause an excess of negative charges on the outer surface . Therefore, the active surface of HNTs without any modification is very conducive to bonding with MOFs via coordination reactions of metal ions from MOFs.…”

“…As a consequence of this, the inner surface is positively charged because of the protonation of Al−OH groups, and the Si−OH groups cause an excess of negative charges on the outer surface. 44 Therefore, the active surface of HNTs without any modification is very conducive to bonding with MOFs via coordination reactions of metal ions from MOFs. Besides, HNTs are low-cost, environment-friendly, and easily available.…”

Ti-modified imogolite nanotubes: highly photoactive nanoreactors for H2 production

“…The first two samples (x = 0 and 0.2) present a large absorption band located at 1571 eV, characteristic of aluminum in octahedral configuration. [33] With increasing [Ti]/([Ge]+[Ti]) ratio, a lower energy resonance appears at 1567 eV that is related to the spectral feature of boehmite, which contains Al sites in only one distorted octahedral configuration compared to imogolite nanotubes. [34] The formation of boehmite phase is progressive, depending on the doping ratio as demonstrated by linear combination fitting of XANES spectra (inset in Figure 2c) using pure Ge-DWINT (x = 0) and the sample prepared at x = 1 that contain only boehmite as Al species.…”

Compressibility and Structural Transformations of Aluminogermanate Imogolite Nanotubes under Hydrostatic Pressure

“…Prior to measurements under pressure, INT powders were dried in an oven for 2 h at 200 °C in order to remove all water molecules within the structure according to previous thermogravimetric analyses. ,, …”

“…Prior to measurements under pressure, INT powders were dried in an oven for 2 h at 200 °C in order to remove all water molecules within the structure according to previous thermogravimetric analyses. 31,35,37 Pressure Measurements. A diamond anvil cell (DAC), equipped with a 1 mm culet diamond, was used to apply pressure.…”