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TiO2 nanobelts (NBs) have received much attention due to their chemical stability, nontoxicity, special one-dimension morphology and also have found many applications. However, extensively employed hydrothermal processes are time-consuming. In this work, a microwave-assisted hydrothermal (MAH) method is for the first time reported for the rapid fabrication of TiO2 NBs. TiO2 NBs with widths of 25–200 nm and lengths up to tens micrometers can be successfully fabricated by adjusting the concentration of NaOH solution, reaction time and reaction temperatures. By MAH method, the reaction time can be greatly shortened to 4 h under microwave irradiation compared to 1–3 days reported in literature. Bi-crystalline structures with monoclinic TiO2(B) and tetragonal anatase can be tuned by simply adjusting thermal treatment temperatures. The evolution of different crystalline structures from starting H2Ti3O7 to crystalline TiO2 phases with increasing calcination temperatures was analyzed by different techniques. The photocatalytic activity results reveal that bi-crystalline structures with TiO2(B)/anatase phases (optimal B:A ratio of 66:34) are advantageous to enhance the photocatalytic performance of TiO2 NBs in photo-decomposing Rhodamine B molecules in water under UV irradiation.

In this paper, we study the mathematical model of electron beam focusing system where a>0,b⩾0 are constants, find conditions for the existence of positive π-periodic solution of the above equation by using analytical method and comparison theory, and prove the existence of positive π-periodic solution by the continuously dependent theory of initial value problem. Copyright © 2004 John Wiley & Sons, Ltd.

A new method is used to directly grow carbon nanotube (CNT) junctions with two different structures through a continuous chemical vapor deposition (CVD) process. CH 4 /B 2 H 6 /H 2 and CH 4 /H 2 source gases were used as the feeding gas, respectively. By switching between different source gases in the CVD process, the junctions composed of boron-doped and pure CNTs were prepared. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were used to evaluate the structure and composition of such junctions. The results show that each junction is having a bamboo boron-doped CNT at one side and a hollow CNT at another side, and the two different structures are connected with each other successfully.