Irradiation-Hardening Model of TiZrHfNbMo0.1 Refractory High-Entropy Alloys.

In order to find more excellent structural materials resistant to radiation damage, high-entropy alloys (HEAs) have been developed due to their characteristics of limited point defect diffusion such as lattice distortion and slow diffusion. Specially, refractory high-entropy alloys (RHEAs) that can adapt to a high-temperature environment are badly needed. In this study, TiZrHfNbMo0.1 RHEAs are selected for irradiation and nanoindentation experiments. We combined the mechanistic model for the depth-dependent hardness of ion-irradiated metals and the introduction of the scale factor f to modify the irradiation-hardening model in order to better describe the nanoindentation indentation process in the irradiated layer. Finally, it can be found that, with the increase in irradiation dose, a more serious lattice distortion caused by a higher defect density limits the expansion of the plastic zone.

Hydrogen storage capacity characterization of carbon nanotubes by a microgravimetrical approach.

An accurate gravimetric apparatus based on a contactless magnetic suspension microbalance was developed. This unit was used to measure the hydrogen storage capacity for a variety of carbon nanotubes (CNTs) at room temperature and hydrogen pressures up to 11.5 MPa. The results show that regardless of their synthesis methods, purities, and nanostructures all investigated CNT products possess relatively low hydrogen storage capacities (<0.2 wt %). For comparison, the adsorption characteristics of theses samples were also measured at a pressure of 0.1 MPa and liquid nitrogen temperature (approximately 77 K) by a conventional volumetric approach. The methodological aspects related to the accuracy of the hydrogen uptake measurements are also discussed.

Band-filling of solution-synthesized CdS nanowires.

The band edge optical characterization of solution-synthesized CdS nanowires (NWs) is described. Investigated wires are made through a solution-liquid-solid approach that entails the use of low-melting bimetallic catalyst particles to seed NW growth. Resulting diameters are approximately 14 nm, and lengths exceed 1 microm. Ensemble diameter distributions are approximately 13%, with corresponding intrawire diameter variations of approximately 5%. High-resolution transmission electron micrographs show that the wires are highly crystalline and have the wurtzite structure with growth along at least two directions: [0001] and [1010]. Band edge emission is observed with estimated quantum yields between approximately 0.05% and 1%. Complementary photoluminescence excitation spectra show structure consistent with the linear absorption. Carrier cooling dynamics are subsequently examined through ensemble lifetime and transient differential absorption measurements. The former reveals unexpectedly long band edge decays that extend beyond tens of nanoseconds. The latter indicates rapid intraband carrier cooling on time scales of 300-400 fs. Subsequent recovery at the band edge contains significant Auger contributions at high intensities which are usurped by other, possibly surface-related, carrier relaxation pathways at lower intensities. Furthermore, an unusual intensity-dependent transient broadening is seen, connected with these long decays. The effect likely stems from band-filling on the basis of an analysis of observed spectral shifts and line widths.