• PDF / 1,605,471 Bytes
• 9 Pages / 612 x 792 pts (letter) Page_size
• 6 Downloads / 288 Views

DOWNLOAD

REPORT

---

Welcome

MATERIALS RESEARCH

Comments

Help

Synthesis and characterization of rutile TiO2 nanowhiskers G.L. Li and G.H. Wang National Laboratory of Solid State Microstructures, Center for Advanced Studies of Science and Technology of Nanjing University, Nanjing 210093, China and Laboratory of Atomic Imaging of Solids, Institute of Metal Research, Academia Sinica, Shenyang 110015, China

J.M. Hong Modern Analysis Center, Nanjing University, Nanjing 210093, China (Received 21 September 1998; accepted 10 May 1999)

Rutile TiO2 nanowhiskers have been synthesized by annealing a precursor powder in which NaCl and Ti(OH)4 particles were homogeneously mixed. The precursor powder was prepared by mixing three kinds of inverse microemulsions (␮E) containing TiCl4 aqueous solution, ammonia, and NaCl aqueous solution, respectively, followed by washing with acetone. Annealing temperature and packing density of Ti(OH)4 in the precursor powder influenced the formation of rutile nanowhiskers. The optimum temperature was 750 °C. TiO2 nanowhiskers obtained by annealing a precursor powder in which the molar ratio of sodium to titanium was 400 at 750 °C for 2 h had diameters of 10–50 nm and lengths of several micrometers. They were straight rods with square cross sections, and the side surfaces were composed of four equivalent {110} planes.

I. INTRODUCTION 1,2

Nanomaterials have been widely used in chemistry because of their large surface-to-volume ratio. Surface structures and states influence the properties of these materials. Nanomaterials are frequently used in the form of powders or loose compacts consisting of small particles of sizes on nanometer scale. Typically the particle surface is composed of several well-defined crystal planes.3,4 It is difficult to predict the contribution of each plane to the properties. Over the past several years, a variety of methods have been developed for the synthesis of nanorods, such as carbon nanotube confined chemical reactions5,6 and vapor-liquid-solid (VLS), 7–9 solution-liquid-solid (SLS),10 and template-based synthetic approaches.11–13 Semiconductor6–11 and metal nanowires11–13 are the most extensively studied for their potential applications in semiconductor and electronic technologies. A few works on the preparation of carbide nanorods5 might also find technologic applications in nanostructured composite materials. Because of its unusual structure, the surface chemistry and physics of a whisker are different from that of a spheroidal particle. Therefore material composed of whiskers will have novel properties. Titania is an important transition metal oxide, widely used as catalyst support,14 semiconductor photocatalyst,15 and gas16 and humidity sensor.17,18 TiO2 whiskers are normally synthe3346

http://journals.cambridge.org

J. Mater. Res., Vol. 14, No. 8, Aug 1999 Downloaded: 02 Jun 2014

sized using alkali titanate whiskers as precursor material.19,20 They can also be prepared by heating Sn-doped TiO2 precursor powder21 or by chemical vapor deposition method.22 In this work, we hav