MESOPOROUS Na2Ti3O7 NANOTUBE-CONSTRUCTED MATERIALS WITH HIERARCHICAL ARCHITECTURE: SYNTHESIS AND PROPERTIES

Abstract

Recently, design of hierarchical materials with remarkable and unusual properties, useful for practical applications, has become more and more meaningful in nanosciences and nanoengineering. This report presents a method of fabricating Na2Ti3O7-based materials with hierarchical two-level (micro/nano) architecture. The products are microparticles constructed of thin-walled nanotubes having an outer diameter of 6–9 nm, wall thickness of 2–3 nm, and length of several hundred nanometers. The synthesis was carried in hydrothermal conditions at 130 °C for 36 h in a highly alkaline medium (10M NaOH aqueous solution). The obtained hierarchical materials exhibit surface roughness and porosity (specific surface area of 314 m2/g and pore volume of 0.54 cm3/g are achieved) with a narrow pore-size distribution in the mesopore range (average pore diameter is around 5.7 nm). Phase formation of products has been studied as a function of calcination temperature. It was found that Na2Ti3O7-based materials is obtained for calcination conditions of near 350 °C. Higher temperatures (more than 500 °C) favored anatase TiO2 formation. There are no significant changes were detected in morphology and texture of products calcined at 350 °C. An electrical conductivity of over 10–3 S/cm at room temperature was registered for materials. Besides, it is increased for three times after thermal treatment at 350 °C. The results suggest that obtained hierarchical nanotube-constructed porous Na2Ti3O7 microparticles can be involved for various industrial uses, including next generation electrochemical power sources.