RESUMEN
Viscous droplet impact on nonwettable surfaces with complex geometry is of technological importance, but the fundamental understanding of the dynamics is not entirely understood yet. In this work, liquid drops with various viscosities and impact velocities were investigated, and their behavior was correlated with contact time upon impinging nonwettable flat and textured surfaces. It was shown that in the inertial-capillary regime, the contact time between the droplet and a flat surface is independent of impact velocity, whereas for the viscous-capillary regime, it increases with impact velocity. Drops impacting on nonwettable surfaces with single and multiple macroscopic ridges generally leave the surface at a reduced contact time, compared to flat surfaces. The incorporation of a single macrotexture results in a steplike reduction in the contact time because the impacting drop reaches the maximum spreading diameter, a condition that must happen when the capillary number is below unity.
RESUMEN
Hydrogen chloride (HCl) gas is a hazardous byproduct of industrial processes. Colorimetric approaches to facilitate portable and remote detection are especially desirable. We graft polyaniline to the surface of electrospun nylon nanofibers to minimize mass transfer. Using the resulting nanofibers, we demonstrate colorimetric detection of HCl at sub-ppm levels. We investigated the reusability of the fibers and observed a twofold increase in the limit of detection with multiple uses because of dedoping of the PANi indicated by elemental analysis. The limit of detection using visual detection was compared to spectrophotometric analysis. The ΔE from CIE LAB color space analysis via diffuse reflectance spectroscopy enhances the limit of detection by â¼fivefold when compared to visual detection. This analysis is a promising approach for remote detection using simple commercial digital cameras to achieve low limits of detection.
RESUMEN
Precise control over the magnetic properties of FeCo alloys is of scientific significance, due to their high Curie points and saturation magnetizations, and of broad interest for applications such as transformer cores, induction motors, switching devices, and hyperthermia. The magnetic properties of FexCo(1-x) alloy-based nanopowders prepared by polyol synthesis and their relationship with morphological features and the evolution of the microstructure were investigated using a design of experiments (DoE) approach. Proportionalities related to the magnetic properties, saturation magnetization (Ms) and coercivity (Hc), were identified where Ms â (110) crystallite size of FeCo (bcc) and Hc â particle diameter for the as-synthesized FexCo(1-x) nanopowders. Adjusting the reaction composition allows for control of the FeCo (bcc) (110) crystallite size from 20-45 nm represented by a response surface model. Morphological features of the as-synthesized nanopowders include particles interlinked as chains, and particles either in the form of cuboids or spheroids, all with diameters ranging from 75-175 nm. FexCo(1-x) alloy was confirmed by XRD in each nanopowder while few contained a combination of phases which include Co (fcc), or ferrite (CoFe2O4), or both. Depending on composition, particle dimension, and microstructure, the Ms ranged from 90-215 emu g-1 with Hc from 90-400 Oe for all nanopowders synthesized by the sub-reflux, isothermal condition (150 °C). Tailoring the magnetic properties of FexCo(1-x) alloy-based nanopowders is accomplished chemically by identifying and regulating significant reaction parameters and conditions.