Spontaneous scrolling of kaolinite nanosheets into halloysite nanotubes in an aqueous suspension in the presence of GeO2
White, Rachel D, Bavykin, Dmitry V. and Walsh, Frank C. (2012) Spontaneous scrolling of kaolinite nanosheets into halloysite nanotubes in an aqueous suspension in the presence of GeO2. The Journal of Physical Chemistry C, 116, 8824-8833. (doi:10.1021/jp300068t).
Despite the natural occurrence of aluminosilicate nanotubes as mineral halloysite, suitable hydrothermal methods for their preparation are still undeveloped due to their lower thermodynamic stability under hydrothermal conditions. The effect of addition of GeO2 to the reaction mixture of SiO2 and Al(OH)3 on the distribution of the morphologies of nanostructured aluminosilicates obtained under hydrothermal treatment at pH 2 and 220 ºC has been systematically studied. It was found that the formation of multilayered nanotubes of halloysite (Al2Si2O5(OH)4) occurs at 0.2 Ge/(Si+Ge) molar fraction after 7 days of hydrothermal treatment. The as-obtained halloysite nanotubes are characterized by a high degree of crystallinity, a multilayered (25-40 layers) wall structure and a typical inner diameter of 5-15 nm. A further increase in Ge/(Si+Ge) molar fraction to 0.5 results in precipitation of single walled nanotubes analogous to germanium-containing imogolite (Al2SixGe1-xO3(OH)4, x ~ 0.65) characterized with an average inner diameter of 0.9-1.2 nm. At a lower molar ratio (0.05, 0.1) partially curved, multilayer nanosheets of kaolinite are produced. The complete analysis of structure and morphology of all products was performed using TEM, EDX, SAED, FTIR and nitrogen adsorption. The mechanism governing the precipitation of Al2Si2O5(OH)4 nanotubes in the presence of Ge(IV) is discussed.
|Keywords:||halloysite, hydrothermal synthesis, germanium oxide|
|Subjects:||Q Science > QD Chemistry
T Technology > TP Chemical technology
|Divisions:||Faculty of Engineering and the Environment > Engineering Sciences
Faculty of Engineering and the Environment > Engineering Sciences > Engineering Materials Surface Engineering
|Date Deposited:||26 Apr 2012 14:37|
|Last Modified:||28 Feb 2014 17:00|
The hydrothermal route to metal oxide nanotubes: synthesis and energy conversion application. A First Grant Proposal
Funded by: EPSRC (EP/F044445/1 - £303,406)
Led by: Dmitry V. Bavykin
15 September 2008 to 14 September 2010
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