Abstract: The high-rate sensitivity of nanostructured metallic materials demonstrated in the recent literature is related to the predominance of thermally activated deformation mechanisms favoured by a large density of internal interfaces. Here we report time-resolved high-resolution electron transmission microscopy creep tests on thin nanograined films using on-chip nanomechanical testing. Tests are performed on ​palladium, which exhibited unexpectedly large creep rates at room temperature. Despite the small 30-nm grain size, relaxation is found to be mediated by dislocation mechanisms. The dislocations interact with the growth nanotwins present in the grains, leading to a loss of coherency of twin boundaries. The density of stored dislocations first increases with applied deformation, and then decreases with time to drive additional deformation while no grain boundary mechanism is observed. This fast relaxation constitutes a key issue in the development of various micro- and nanotechnologies such as ​palladium membranes for hydrogen applications.

Abstract: A wide range of rules, algorithms, and models are available to design an effective pump and treat remediation system. Often, one refers to the effectiveness of the developed pump and treat system to demonstrate how valuable the use of a groundwater model can be. An economic valuation of the groundwater model is usually missing. This study provides a framework that puts the discussion concerning the use of groundwater models in an economic perspective. It is not only demonstrated that a more effective pump and treat system can be designed using a groundwater model, but also the economic implications of using a groundwater model are calculated. A set of economic decision rules is applied to determine the economic value of a groundwater model. It is shown that investing in a groundwater model can be economically worthwhile. The remediation time is reduced, remediation costs are saved and the property can be sold more early. These benefits outweigh the costs of developing a groundwater model, and hence a positive net benefit (NB) is determined.

Abstract: In 1999, phytoremediation was applied at the site of a Belgian car factory to contain two BTEX plumes. This case study evaluates the cost effectiveness of phytoremediation compared to other remediation options, applying a tailored approach for economic evaluation. Generally, when phytoremediation is addressed as being cost effective, the cost effectiveness is only determined on an average basis. This study however, demonstrates that an incremental analysis may provide a more nuanced conclusion. When the cost effectiveness is calculated on an average basis, in this particular case, the no containment strategy (natural attenuation) has the lowest cost per unit mass removed and hence, should be preferred. However, when the cost effectiveness is determined incrementally, no containment should only be preferred if the value of removing an extra gram of contaminant mass is lower than 320. Otherwise, a permeable reactive barrier should be adopted. A similar analysis is provided for the effect determined on the basis of remediation time. Phytoremediation is preferred compared to no containment if reaching the objective one year earlier is worth 7 000.

Abstract: This paper discusses the nucleation behaviour of the CoSi to CoSi2 transformation from cobalt silicide thin films grown by deposition at elevated substrate temperatures ranging from 375 °C to 600 °C. A combination of channelling, real-time Rutherford backscattering spectrometry, real-time x-ray diffraction, and transmission electron microscopy was used to investigate the effect of the deposition temperature on the subsequent formation temperature of CoSi2, its growth behaviour, and the epitaxial quality of the CoSi2 thus formed. The temperature at which deposition took place was observed to exert a significant and systematic influence on both the formation temperature of CoSi2 and its growth mechanism. CoSi films grown at the lowest temperatures were found to increase the CoSi2 nucleation temperature above that of CoSi2 grown by conventional solid phase reaction, whereas the higher deposition temperatures reduced the nucleation temperature significantly. In addition, a systematic change in growth mechanism of the subsequent CoSi2 growth occurs as a function of deposition temperature. First, the CoSi2 growth rate from films grown at the lower reactive deposition temperatures is substantially lower than that grown at higher reactive deposition temperatures, even though the onset of growth occurs at a higher temperature, Second, for deposition temperatures below 450 °C, the growth appears columnar, indicating nucleation controlled growth. Elevated deposition temperatures, on the other hand, render the CoSi2 formation process layer-by-layer which indicates enhanced nucleation of the CoSi2 and diffusion controlled growth. Our results further indicate that this observed trend is most likely related to stress and changes in microstructure introduced during reactive deposition of the CoSi film. The deposition temperature therefore provides a handle to tune the CoSi2 growth mechanism.

Abstract: A robust and expedient gas quenching method is developed for the solution deposition of hybrid perovskite thin films. The method offers a reliable standard practice for the fabrication of a non-exhaustive variety of perovskites exhibiting excellent film morphology and commensurate high performance in both regular and inverted structured solar cell architectures.

Abstract: We have used scanning Hall probe and local Hall magnetometry measurements to map flux profiles in superconducting Bi2Sr2CaCu2O8+δ disks whose diameters span the crossover between the bulk and mesoscopic vortex regimes. The behaviour of large disks (greater-or-equal, slanted20 μm diameter) is well described by analytic models that assume a continuous distribution of flux in the sample. Small disks (less-than-or-equals, slant10 μm diameter), on the other hand, exhibit clear signatures of the underlying discrete vortex structure as well as competition between triangular Abrikosov ordering and the formation of shell structures driven by interactions with circulating edge currents. At low fields we are able to directly observe the characteristic mesoscopic compression of vortex clusters which is linked to oscillations in the diameter of the vortex dome in increasing magnetic fields. At higher fields, where single vortex resolution is lost, we are still able to track configurational changes in the vortex patterns, since competing vortex orders impose unmistakable signatures on local magnetisation curves. Our observations are in excellent agreement with molecular-dynamics numerical simulations which lead us to a natural definition of the lengthscale for the crossover between discrete and continuum behaviour in our system.

Abstract: The magnetic properties of a superconducting disk change dramatically when its dimensions become mesoscopic. Unlike large disks, where the screening currents induced by an applied magnetic field are strong enough to force vortices to accumulate in a 'puddle' at the centre, in a mesoscopic disk the interaction between one of these vortices and the edge currents can be comparable to the intervortex repulsion, resulting in a destruction of the ordered triangular vortex lattice structure at the centre. Vortices instead form clusters which adopt polygonal and shell-like structures which exhibit magic number states similar to those of charged particles in a confining potential, and electrons in artificial atoms. We have fabricated mesoscopic high temperature superconducting Bi2Sr2CaCu2O8+δ disks and investigated their magnetic properties using magneto-optical imaging (MOI) and high resolution scanning Hall probe microscopy (SHPM). The temperature dependence of the vortex penetration field measured using MOI is in excellent agreement with models of the thermal excitation of pancake vortices over edge barriers. The growth of the central vortex puddle has been directly imaged using SHPM and magic vortex numbers showing higher stability have been correlated with abrupt jumps in the measured local magnetisation curves.