Pulsed Laser Deposited Zeolite Coatings on Femtosecond Laser-Nanostructured Steel Meshes for Durable Superhydrophilic/Oleophobic Functionalities.

Ultrafast laser structuring has proven to alter the wettability performance of surfaces drastically due to controlled modification of the surface roughness and energy. Surface alteration can be achieved also by coating the surfaces with functional materials with enhanced durability. On this line, robust and tunable surface wettability performance can be achieved by the synergic effects of ultrafast laser structuring and coating. In this work, femtosecond laser-structured stainless steel (SS-100) meshes were used to host the growth of NaAlSi2O6-H2O zeolite films. Contact angle measurements were carried on pristine SS-100 meshes, zeolite-coated SS-100 meshes, laser-structured SS-100 meshes, and zeolite-coated laser-structured SS-100 meshes. Enhanced hydrophilic behavior was observed in the zeolite-coated SS-100 meshes (contact angle 72°) and in laser-structured SS-100 meshes (contact angle 41°). On the other hand, superior durable hydrophilic behavior was observed for the zeolite-coated laser-structured SS-100 meshes (contact angle 14°) over an extended period and reusability. In addition, the zeolite-coated laser-structured SS-100 meshes were subjected to oil-water separation tests and revealed augmented effectuation for oil-water separation.

Magnetic, electrical and mechanical properties of Fe40Mn40Co10Cr10 high entropy alloy.

A prototypical, single-phase, and non-equiatomic high entropy alloy Fe40Mn40Co10Cr10 has been mechanically deformed at room and cryogenic temperatures. Plastic deformation was accommodated via crystallographic slip at room temperature while transformation induced plasticity (TRIP) has been observed in samples deformed at 77 K. The stress-induced martensitic transformation occurred from face-centered cubic (FCC) to hexagonal close-packed (HCP) structures. A detailed electron backscatter diffraction analysis was utilized to detect phase change and evaluate the evolution of the HCP phase volume fraction as a function of plastic strain. Physical properties of undeformed and deformed samples were measured to elucidate the effect of deformation-induced phase transitions on the magnetic and electrical properties of Fe40Mn40Co10Cr10 alloy. Relatively small magnetic moments along with non-saturating magnetic field dependencies suggest that the ground state in the considered material is ferrimagnetic ordering with coexisting antiferromagnetic phase. The temperature evolution of the coercive fields has been revealed for all samples. The magnitudes of the coercive fields place the considered system into the semi-hard magnetic alloys category. The temperature dependence of the zero-field cooled (ZFC) and field cooled (FC) magnetization was measured for all samples in the low field regime and the origin of irreversibility in ZFC/FC curves was discussed. Besides, the temperature dependence of the resistivity in all samples was measured and the possible conduction mechanisms were discussed.

Microwave conductivity of sorted CNT assemblies.

Recent progress with tailored growth and post-process sorting enables carbon nanotube (CNT) assemblies with predominantly metallic or semi-conducting concentrations. Cryogenic and microwave measurements performed here show transport dimensionality and overall order increasing with increasing metallic concentration, even in atmospheric doping conditions. By 120 GHz, the conductivity of predominantly semi-conducting assemblies grew to 400% its DC value at an increasing growth rate, while other concentrations a growth rate that tapered off. A generalized Drude model fits to the different frequency dependent behaviors and yields useful quality control parameters such as plasma frequency, mean free path, and degree of localization. As one of the first demonstrations of waveguides fabricated from this material, sorted CNTs from both as-made and post-process sources were inserted into sections of practical micro-strip. With both sources, sorted CNT micro-strip increasingly outperformed the unsorted with increasing frequency-- illustrating that sorted CNT assemblies will be important for high frequency applications.

Supercurrent enhancement in Bloch domain walls.

Conventional spin-singlet Cooper pairs convert into spin-triplet pairs in ferromagnetic Josephson junctions in which the superconductor/ferromagnet interfaces (S/F) are magnetically inhomogeneous. Although much of the theoretical work describing this triplet proximity effect has considered ideal junctions with magnetic domain walls (DW) at the interfaces, in practice it is not easily possible to isolate a DW and propagate a supercurrent through it. The rare-earth magnet Gd can form a field-tuneable in-plane Bloch DW if grown between non-co-linearly aligned ferromagnets. Here we report supercurrents through magnetic Ni-Gd-Ni nanopillars: by field annealing at room temperature, we are able to modify the low temperature DW-state in Gd and this result has a striking effect on the junction supercurrent at 4.2 K. We argue that this result can only be explained in terms of the interconversion of triplet and singlet pairs, the efficiency of which depends on the magnetic helicity of the structure.