Yi Fan

Phonon characteristics and photoluminescence of bamboo structured silicon-doped boron nitride multiwall nanotubes

Bamboo structured silicon-doped boron nitride multiwall nanotubes are synthesized via catalyst-assisted pyrolysis of a boron-containing polymeric precursor. The nanotubes are characterized using transmission electron microscopy, x-ray diffraction, Raman, and Fourier-transformed infrared spectroscope. The results suggest that the Si dopants cause significant changes in the structure and phonon characteristics of the nanotubes as compared to pure boron nitride nanotubes. A broad photoluminescence band ranging between 500 and 800nm is observed from the nanotubes, which is attributed to Si dopants. Study on temperature dependence of emission intensity suggests that the thermal activation energy of the nonradiative recombination process is 35meV.

Oxygen diffusion through Al-doped amorphous SiO2

Oxygen (O) diffusion through pure and aluminum (Al)-doped amorphous silica is investigated by using secondary ion mass spectrometry to profile the diffusion of an18O tracer. The oxides are formed by the thermal oxidation of polymer-derived SiCN and SiAlCN ceramics. The authors demonstrate that a small amount of Al dopant can significantly inhibit both the interstitial and network diffusion of O. The activation energy of O network diffusion for Al-doped silica is two times higher than that for pure silica. The results are discussed in terms of the modification of Al doping on the network structure of the otherwise pure silica.

Ultraviolet irradiation-induced photoluminescence degradation in γ-alumina nanoparticles

The photoluminescence (PL) behavior of γ-Al2O3 nanopowder is studied. Two emission peaks at 343 and 378nm and a broadband ranging between 400 and 600nm are observed. The peaks are attributed to F+ center, while the broadband is attributed to impurities. It is found that irradiating the sample with intense ultraviolet (UV) light can cause significant decrease in the intensity of the two peaks, but has no effect on the broadband. A simple model is proposed to explain the kinetics of UV irradiation-induced PL degradation.