Showing papers by "Yue Wu published in 1998"
TL;DR: In this paper, single-walled carbon nanotubes (SWNTs) were reacted with HNO 3 solution, and an expansion of the inter-nanotube spacing and increase in the amount of hydrogen in the material were observed by X-ray diffraction and proton NMR measurements after the SWNTs were immersed into the HNO3 solution for less than 2 hours.
167 citations
TL;DR: In this article, NMR was used for the first time to detect slow atomic motion in metallic glasses, specifically, Be motion in Zr-Ti-Cu-Ni-Be bulk metallic glasses.
Abstract: Nuclear magnetic resonance is used for the first time to detect slow atomic motion in metallic glasses, specifically, Be motion in Zr-Ti-Cu-Ni-Be bulk metallic glasses. The observations are not consistent with the vacancy-assisted and interstitial diffusion mechanisms and favor the spread-out free volume fluctuation mechanism for Be diffusion. Comparison with the results of Be diffusion measured by elastic backscattering the NMR results also indicates that the energy barriers for short- and long-range Be motion are the same.
69 citations
TL;DR: In this paper, a-Si:H films were prepared by glow discharge CVD with pure or H-diluted silane as well as by hot-wire CVD, and the Si-H bond absorption and its light-soaking-induced changes were studied by IR and differential IR absorption spectroscopes.
Abstract: Device-quality a-Si:H films were prepared by glow discharge CVD with pure or H-diluted silane as well as by hot-wire CVD. The hydrogen content was varied from similar to 2 to 15 at. %. The Si-H bond absorption and its light-soaking-induced changes were studied by IR and differential IR absorption spectroscopes. The results indicate that the more stable sample exhibits an increase of the absorption at wave number similar to 2000 cm(-1), and the less stable one exhibits a decrease at similar to 2040 cm(-1) and an increase at similar to 1880 cm(-1).
3 citations
TL;DR: In this article, a nuclear magnetic resonance (NMR) study of slow atomic motions in Zr-Ti-Cu-Ni-Be bulk metallic glasses was performed, and the authors provided direct experimental evidences that exclude vacancy-assisted and interstitial diffusion mechanisms for Be motions in these systems.
Abstract: We report a nuclear magnetic resonance (NMR) study of slow atomic motions in Zr-Ti-Cu- Ni-Be bulk metallic glasses. The employed 9 Be spin alignment echo technique is able to probe Be motions with jump rate below 0.1 Hz. It was found that the Be motion is spatially homogeneous. The jump rate follows a perfect Arrhenius temperature dependence. The measured activation enthalpy of 1.2 eV is nearly identical to that obtained by Be diffusivity measurement using elastic backscattering (EBS); this indicates that energy barriers are the same for short and long range Be motions. The present work provides direct experimental evidences that exclude vacancy-assisted and interstitial diffusion mechanisms for Be motions in these systems. The result is interpreted in terms of the spread-out free volume fluctuation mechanism.
3 citations