Tuning heterogeneous ion-radiation damage by composition in NixFe1-x binary single crystals.

Radiation-induced heterogeneous damage is the single largest source of failures seen in structural components in nuclear power reactors. Single crystal materials without grain boundaries, show considerable promise for overcoming this problem. In this work, such heterogeneous damage was further overcome in NixFe1-x single crystal alloys via a simple strategy of fine-tuning the composition. [001] NixFe1-x (x = 0, 0.38 and 0.62 at%) single crystals prepared using the Bridgman method were irradiated over a wide fluence range (4 × 1013 to 4 × 1015 ions per cm2). The irradiation-induced defect evolution was studied using Rutherford backscattering/channeling spectrometry, Monte Carlo simulations, transmission electron microscopy and nanoindentation. The results indicate an increased radiation tolerance of Ni0.38Fe0.62 compared to pure Ni and Ni0.62Fe0.38. The structural analysis performed by transmission electron microscopy revealed that defects tend to agglomerate at one place in Ni and Ni0.62Fe0.38, while in Ni0.38Fe0.62 no defect accumulation zone (characteristic damage peak) has been captured either at low or high fluence. Moreover, we found that the hardness change with the increase of Fe content is due to different arrangements of Fe atoms in the crystal structure, which influences the obtained mechanical properties of NixFe1-x in the pristine state and after ion implantation.

The operational window of carbon nanotube electrical wires treated with strong acids and oxidants.

Conventional metal wires suffer from a significant degradation or complete failure in their electrical performance, when subjected to harsh oxidizing environments, however wires constructed from Carbon Nanotubes (CNTs) have been found to actually improve in their electrical performance when subjected to these environments. These opposing reactions may provide new and interesting applications for CNT wires. Yet, before attempting to move to any real-world harsh environment applications, for the CNT wires, it is essential that this area of their operation be thoroughly examined. To investigate this, CNT wires were treated with multiple combinations of the strongest acids and halogens. The wires were then subjected to conductivity measurements, current carrying capacity tests, as well as Raman, microscopy and thermogravimetric analysis to enable the identification of both the limits of oxidative conductivity boosting and the onset of physical damage to the wires. These experiments have led to two main conclusions. Firstly, that CNT wires may operate effectively in harsh oxidizing environments where metal wires would easily fail and secondly, that the highest conductivity increase of the CNT wires can be achieved through a process of annealing, acetone and HCl purification followed by either H2O2 and HClO4 or Br2 treatment.

SEM and Raman analysis of graphene on SiC(0001).

Graphene grown by a sublimation technique was studied by Scanning Electron Microscopy (SEM) and micro-Raman spectroscopy. The measurement area of a sample was marked and investigated using both systems, as a result of which SEM images were directly compared with Raman maps. In this work we show that a correlative analysis of Energy Selective Backscattered electrons detector (EsB), In-Lens figures and Raman maps of shape and intensity of the 2D band is adequate to determine graphene layer thickness with the precision of SEM and reliability of Raman spectroscopy.

Metabolic correlates of selection for swim stress-induced analgesia in laboratory mice.

The upper limits of metabolic rates and the links between maximal and resting metabolic rates in vertebrates have recently received a lot of attention, mainly due to their possible relationship to the evolution of endothermy. We measured peak metabolic rates during 3 min swimming in 20 degrees C water (Vo2swim), maximal metabolic rate (Vo2max) in -2.5 degrees C Helox, and basal metabolic rate (BMR) in two lines of mice selected for high (HA) and low (LA) swim stress-induced analgesia (SSIA). We found that exercise combined with heat loss used for producing SSIA also acted as a selection agent, resulting in a 15% HA/LA line difference in Vo2swim. Core body temperature of HA mice (characterized by lower Vo2swim) was also on average 3.2 degrees C lower than that of LA mice. Furthermore, Vo2max of HA mice was lower than that of LA mice by 8% and accompanied by larger hypothermia. Thus mice with exceptionally high (or low) Vo2max tended to have exceptionally high (or low) Vo2swim, resulting in a positive correlation between Vo2swim and Vo2max. All these suggest that selection for SSIA produced genetically correlated responses in both Vo2swim and Vo2max. However, we did not observe HA/LA differences in BMR. Hence, changes in resting and maximum metabolic rates are not necessarily correlated. We hypothesize that the lack of such a correlation was partially due to the modulation of metabolic responses by SSIA.