Size distributions of nanoscopic holes in Ti/h-BN and Ti/B nanocomposites

作者：Cizek J^*; Prochazka I; Morozova O S; Borchers C; Pundt A

来源：Journal of Applied Physics, 2010, 107(4): 043509.

DOI：10.1063/1.3305790

• ball milling
• boron
• boron compounds
• crystal defects
• Doppler broadening
• hole density
• III-V semiconductors
• nanocomposites
• nanoparticles
• positron annihilation
• positronium
• titanium
• wide band gap semiconductors

Positron annihilation spectroscopy was employed for defect studies of "Ti"-based nanocomposites prepared by high-energy ball milling and consisting of Ti nanoparticles separated by hexagonal boron nitride (h-BN) or boron (B) additive. The size distribution of nanoscopic holes in nanocomposites was determined directly from measurement of ortho-positronium (Ps) lifetimes. Chemical environment of defects was characterized using coincidence Doppler broadening. It was found that size of nanoscopic holes is reduced with increasing milling time in H(2)/He atmosphere and also probability of Ps formation in holes decreases. At the same time the Ti content in the vicinity of holes increases. This can be explained by (i) increased intermixing of Ti particles with h-BN or B additive and by (ii) filling the nanoscopic holes with absorbed hydrogen. Analysis of obtained results showed that both these processes take place during milling of nanocomposites. In addition, it was found that the effect of filling the nanoscopic pores with hydrogen is enhanced in TiH(2) milled with h-BN or B in He atmosphere. Comparison of nanocomposites with h-BN and B additive showed that sufficiently long milling time leads to a similar size distribution of nanoscopic holes in Ti/h-BN and Ti/B, despite the fact that it differs substantially in the initial powders. However, density of nanoscopic holes in Ti/B is significantly lower than in Ti/h-BN nanocomposites.

• 出版日期2010-2-15