On the Entangled Growth of NaTaO₃ Cubes and Na₂Ti₃O₇ Wires in Sodium Hydroxide Solution

Abstract

The entangled growth of sodium titanate Na2Ti3O7 nanowires and sodium tantalate NaTaO3 cubes was investigated with electron microscopy, X-ray diffraction, and UV diffuse reflectance spectroscopy. Depending on the composition of the Ta2O5- and TiO2-particle-based powder mixtures, which served as educts, we observed different types of hybridization effects. These include the titanium-induced contraction of the NaTaO3 perovskite-type unit cell and the generation of electronic defect states in NaTaO3 that give rise to optical subbandgap transitions and tantalum-induced limitations of the Na2Ti3O7 nanowire growth. The transformation from Ta2O5 to NaTaO3 occurs through a dissolution-recrystallization process. A systematic analysis of the impact of different titanium sources on NaTaO3 dispersion and, thus, on the properties of the entangled nanostructures revealed that a perfect intermixture of cubes and nanowires can only be achieved when titanate nanosheets emerge during transformation as reaction intermediates and shield nucleation and growth of isolated NaTaO3 cubes. The here demonstrated approach can be highly instrumental for understanding the nucleation and growth of composite and entangled nanostructures in solution and--at the same time--provides an interesting new class of photoactive composite materials.

Size Effects in MgO Cube Dissolution

“…In the present case, we find an intensity ratio of I 001 / I 110 = 1.1. This rules out oriented crystal growth effects and is consistent with the entangled coexistence of different nanosheets …”

“…This rules out oriented crystal growth effects 42 and is consistent with the entangled coexistence of different nanosheets. 43 The reaction of MgO nanocubes and MgO cubes with water in the absence of convective motion was subjected to timedependent XRD measurements. Figure 5 plots the 2Θ region of the periclase (002) and brucite (011) reflections.…”

Thin water films and magnesium hydroxide fiber growth

“…This produces high energy materials which, as a result of H 2 O vapor exposure, undergo spontaneous room temperature conversion into magnesium oxychloride bers. Via the detailed exploration of the key process parameters with regard to the formation of magnesium oxychloride bers we can also demonstrate the great potential of MgO nanocubes as a model system for the elucidation of growth of anisotropic nanostructures, 29 the associated heterogeneous chemistry and, ultimately, the evolution of resulting microstructures. An important aspect relates to the localization of these transformation processes, i.e.…”

“…Earlier powder XRD and solid state 29 Si MAS NMR studies revealed that the LTA sample consists of MgO nanocubes that are covered with surface adsorbed chlorosiloxane species Si x -Cl y O z . 14 Despite their pronounced reactivity in the ambient, the chemical composition as well the nano-/microstructure of this metastable composite can be retained over weeks of storage in vacuum.…”