Narrow Results

In this paper, a simple method for synthesizing SiO_x nanowires and nanocoils is presented. Si substrates with an oxide layer were placed in a tube furnace exposed to temperatures ranging from 900°C to 1200°C for a few hours under a mixture of flowing Ar and H₂ gas maintained at ambient pressure. Nanowires were grown from the surface when the furnace temperature was above 1000°C and a high yield could be achieved at 1100°C. SiO_x nanocoils have also been observed and the sample treated at 1000°C had the highest concentration of them. TEM images show that the nanowires and the nanocoils have an amorphous structure and analysis of EDX spectra (obtained in the TEM) shows that x varies from 1.2 to 2.0. The mechanism of growth is discussed.

Zn was firstly used to improve wear resistance of a TA7 (Ti–5Al–2.5Sn) titanium alloy surface by mean of a laser alloying (LA) technique. The synthesis of the hard coating on a TA7 titanium alloy by LA of Co–Ti–Cr–TiB₂–Zn–CeO₂ pre-placed powders was investigated by means of scanning electron microscope (SEM), X-ray diffraction (XRD) and high resolution transmission electron microscope (HRTEM). Experimental results indicated lot of the nanocrystals, such as Ti–B/CoZn₁₃ and the amorphous phases were produced in such LA coating. The nucleation and growth of the amorphous phases were retarded by the nanocrystals in a certain extent during the crystallization process of the amorphous phases. Compared with a TA7 alloy substrate, an improvement of the wear resistance was obtained for such LA composite coating.