Influence of hydrogenation on the microstructure and crystallization of Zr-Cu-Ni-Al-Y metallic glass

Zr-Cu-Ni-Al-Y metallic glass was electrochemically charged with hydrogen. The hydrogen content in the hydrogenated specimen was derived from the shift of scattering maxima of the X-ray diffraction (XRD) spectra. The microstructures of the untreated Zr-Cu-Ni-Al-Y metallic glass and the hydrogenated specimen have been studied using conventional transmission electron microscopy, high-resolution transmission electron microscopy and energy-dispersive X-ray spectrometry as well as XRD. The untreated Zr-Cu-Ni-Al-Y specimen was found to be almost totally amorphous with a trace amount of yttrium oxide. The addition of the rare-earth element yttrium is beneficial for decreasing the oxygen content in the matrix. Some nanosized precipitates have been found in the hydrogenated specimens. The crystallization of the precipitates was found to consist of two stages. The Zr(Cu, Ni, Al, Y) precipitates segregate in the first stage, while the formation of crystalline ZrH₂ dominates the second stage. The size, amount and distribution of the nanocrystals are mainly related to the charging current and time.     

Indications of bulk property changes from surface ion implantation

In the majority of cases, the effects of ion implantation are confined close to the implant zone but, potentially, the resultant distortions and chemical modifications could catalyse relaxations extending into the bulk substrate. Such possibilities are rarely considered but the present data suggest that high dose ion implantation of ZnO has induced bulk changes. Surface implants with Cu and Tb strongly modified the low temperature bulk thermoluminescence properties generated by X-ray irradiation. Suggestions are proposed for the possible mechanisms for bulk relaxations and structural characteristics, which may indicate where such instability may occur in other lattice structures.     

Concurrent formation of two different type precipitation-free zones during the initial stage of homogenization

Transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy were used to study the microstructure evolution of Al–Cu–Mg alloy during the initial stage of homogenization. It was found that two types of precipitation-free zones (PFZs) can form concurrently: one near grain boundaries and the other at the grain centres. Depth profile analyses of solute concentrations and dislocation-loop distributions strongly suggested that the formations of the two type of PFZs are different, due solely and exclusively to solute and vacancy depletion, respectively. A mechanism model was proposed to explain the concurrent formation of the two different type of PFZs during the initial stage of homogenization.     

Relaxation dynamics of stretched polymer chains traced by shear induced Shish‐Kebab structure

We have developed a morphologic method to investigate the relaxation processing of the stretched polymer chains in melts, in which an atomic force microscope probe was used to shear the surface of an isotactic polypropylene melt to obtain the isolated shish‐kebab structure. We present the results of the time dependence of length of the isolated shish‐kebab structure and the stress dependence of the kebab density along the direction of shish in this paper. Our results demonstrate that the shear‐oriented polymer melts show the relaxation dynamics of worm‐like chain where the length deficit of the isolated shish‐kebab structure is scaled with the relaxation time as a power of 1/3. The melting behavior of shish‐kebab structure was also investigated. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 907–914     

A modified procedure for synthesis of the side chain of ceftazidime-activated thioester

A modified procedure for synthesis of the side chain of ceftazidime-activated thioester has been established. This key intermediate of ceftazidime was obtained by a more eco-friendly process than conventional methods, and the yield was much higher (up to 92.4 %). It was found that different organic bases (triethylamine or pyridine) used in this reaction had different effects. The reaction conditions were also optimized to make the route more competitive and suitable for large-scale industrial production.     

Synthesis of 5-Thio-D- Galactopyranose

5-Thio-D-galactopyranose has been synthesized from diacetone galactofuranose in nine steps and 13.4% overall yield. The key step involved a successful conversion of furanosyl 5,6-epoxide with an L-altrose configuration into the corresponding 5,6-thiirane D-galactose derivative, which was hydrolyzed to the target compound.     

Dye sensitized solar cells prepared by flames stabilized on a rotating surface

A previously developed flame synthesis method was applied to the preparation of mesoporous titania films for application in dye sensitized solar cells (DSSC). The method combines the synthesis of narrowly sized, ultrafine metal oxide particles with controllable chemical and phase purity and the deposition of these particles into a uniform, porous thin film in a single step. The current work used a series of ethylene–oxygen–argon flames to produce DSSC anode films of wide ranging properties. The performance of the solar cells prepared with these anode films was studied at the fundamental level with respect to variations of the titania crystal phase purity and content resulting from changes primarily from flame stoichiometry changes. Based on the basic relationship established among flame synthesis condition-material property-cell performance, a highly efficient DSSC was designed, which shows photocurrent densities better than some of the best performing cells reported to date. Additional studies have focused on a demonstration of the suitability of the flame process in engineering TiO₂ films structurally and chemically with the potential of further improved DSSC efficiency.     

Extended breakdown of Simpleman approximation

In this letter, we solve three-dimensional time-dependent Newton equations for atoms interacting with a ten-cycle elliptically polarized laser pulse. The ionized electron momentum distributions show a tilt angle between the distribution density peak and the main polarization axis. The tilt angle’s behavior changes with an increasing laser intensity. We show that this behavior change is directly related to the release time of the electron from the atom.