Pool boiling of Novec 7300 and self-rewetting fluids on electrically-assisted supersonically solution-blown, copper-plated nanofibers.

Pool boiling of Novec 7300 fluid and self-rewetting water–heptanol mixtures on bare copper surface and a copper surface coated with copper-plated nanofibers is studied experimentally. The experimental data revealed a significant increase in the heat removal rate up to the critical heat flux (CHF) on the copper-plated nanofiber surfaces in comparison with bare copper surfaces. Also, the critical heat flux increases on the copper-plated nanofiber surface, albeit it is reached at a lower surface superheat in comparison with bare copper surface. Prolong boiling in water facilitates oxidation of the layer of copper-plated nanofibers, and diminishes its roughness, albeit does not affect the heat transfer rate

Ion-specific effects in foams

We present a critical review on ion-specific effects in foams in the presence of added salts. We show the theoretical basis developed for understanding experimental data in systems with ionic surfactants, as well as the nascent approaches to modelling the much more difficult systems with non-ionic surfactants, starting with the most recent models of the air-water interface. Even in the case of ionic surfactant systems, we show methods for improving the theoretical understanding and apply them forto interpretation of surprising experimental results we have obtained on ion-specific effects in these systems. our own. We report unexpectedly strong ion-specific effects of counter-ions on the stability and the rate of drainage of planar foam films from solutions of 0.5 mM Sodium dodecyl sulfate (SDS) as a function of concentration of a series of inorganic salts (MCl, M=Li, Na, K). We found that the counter-ions can either stabilize the foam films (up to a critical concentration) or destabilize them beyond it. The ordering for destabilization is in the same order as the Hofmeister series, while for stabilization it is the reverse Therefore, the strongest foam stabilizer (K+), becomes the strongest foam destabilizer at and beyond its critical concetration, and vice versa. Though the critical concentration is different for different salts, by calculating the critical surfactant adsorption level one could simplify the analysis, with all the critical concentrations occuring at the same surfactant adbsorption level. Beyond this level, the foam lifetime decreases and films suddenly start draining faster, which may indicate salt-induced surfactant precipitation. Alternatively, formation of pre-micellar structures may result in slower equilibration and fewer surfactant molecules at the surface, thus leading to unstable foams and films

Thermally driven self-healing using copper nanofiber heater

Nano-textured transparent heaters made of copper nanofibers (CuNFs) are used to facilitate accelerated self-healing of bromobutyl rubber (BIIR). The heater and BIIR layer are separately deposited on each side of a transparent flexible polyethylene terephthalate (PET) substrate. A pre-notched crack on the BIIR layer was bridged due to heating facilitated by CuNFs. In the corrosion test, a cracked BIIR layer covered a steel substrate. An accelerated self-healing of the crack due to the transparent copper nanofiber heater facilitated an anti-corrosion protective effect of the BIIR layer. © 2017 Author(s)

Self-Healing Nanotextured Vascular-like Materials: Mode i Crack Propagation

Here, we investigate crack propagation initiated from an initial notch in a self-healing material. The crack propagation in the core-shell nanofiber mats formed by coelectrospinning and the composites reinforced by them is in focus. All samples are observed from the crack initiation until complete failure. Due to the short-time experiments done on purpose, the resin and cure released from the cores of the core-shell nanofibers could not achieve a complete curing and stop crack growth, especially given the fact that no heating was used. The aim is to elucidate their effect on the rate of crack propagation. The crack propagation speed in polyacrylonitrile (PAN)-resin-cure nanofiber mats (with PAN being the polymer in the shell) was remarkably lower than that in the corresponding monolithic PAN nanofiber mat, down to 10%. The nanofiber mats were also encased in polydimethylsiloxane (PDMS) matrix to form composites. The crack shape and propagation in the composite samples were studied experimentally and analyzed theoretically, and the theoretical results revealed agreement with the experimental data. © 2017 American Chemical Society

Nano-textured Copper Oxide Nanofibers for Efficient Air Cooling.

Ever decreasing of microelectronics devices is challenged by overheating and demands an increase in heat removal rate. Herein, we fabricated highly efficient heat-removal coatings comprised of copper oxide-plated polymer nanofiber layers (thorny devil nanofibers) with high surface-to-volume ratio, which facilitate heat removal from the underlying hot surfaces. The electroplating time and voltage were optimized to form fiber layers with maximal heat removal rate. The copper oxide nanofibers with the thorny devil morphology yielded a superior cooling rate compared to the pure copper nanofibers with the smooth surface morphology. This superior cooling performance is attributed to the enhanced surface area of the thorny devil nanofibers. These nanofibers were characterized with scanning electron microscopy, X-ray diffraction, atomic force microscopy, and a thermographic camera

Silver-decorated and palladium-coated copper-electroplated fibers derived from electrospun polymer nanofibers

Here we introduce novel methods of forming silver (Ag) and palladium (Pd) fibers. The Ag and Pd fibers are fabricated by the combination of electrospinning, electroplating, and ion-exchange techniques. Their properties are characterized by scanning electron microscope with energy dispersive X-ray spectroscopy, sheet resistance meter, UV–Vis spectrophotometer, and X-ray photoelectron spectroscope. These non-woven metal fibers are free-standing and film-shaped with high electrical conductivity, as well as flexibility. Such properties are attractive for future applications of these materials in various electrochemical processes. © 2017 Elsevier B.V

Polyacrylonitrile nanofibers with added zeolitic imidazolate frameworks (ZIF-7) to enhance mechanical and thermal stability

Zeolitic imidazolate framework 7/polyacrylonitrile (ZIF-7/PAN) nanofiber mat of high porosity and surface area can be used as a flexible fibrous filtration membrane that is subjected to various modes of mechanical loading resulting in stresses and strains. Therefore, the stress-strain relation of ZIF-7/PAN nanofiber mats in the elastic and plastic regimes of deformation is of significant importance for numerous practical applications, including hydrogen storage, carbon dioxide capture, and molecular sensing. Here, we demonstrated the fabrication of ZIF-7/PAN nanofiber mats via electrospinning and report their mechanical properties measured in tensile tests covering the elastic and plastic domains. The effect of the mat fabrication temperature on the mechanical properties is elucidated. We showed the superior mechanical strength and thermal stability of the compound ZIF-7/PAN nanofiber mats in comparison with that of pure PAN nanofiber mats. Material characterization including scanning electron microscope, energy-dispersive X-ray spectroscopy, tensile tests, differential scanning calorimetry, and Fourier transform infrared spectroscopy revealed the enhanced chemical bonds of the ZIF-7/PAN complex

Theoretical, numerical, and experimental investigation of pressure rise due to deflagration in confined spaces

Estimating pressure rise due to deflagration in a fully or partially confined space is of practical importance in safety design of a petrochemical plant. Herein, we have developed a new theoretical model to predict the pressure rise due to deflagration in both fully and partially confined spaces. First, the theoretical model was compared and validated against experimental data from the closed-space experiments with hydrogen, methane, propane, and ethane. The theory predicted accurate pressure rises near the stoichiometric regime for all fuel types; outside the stoichiometric regime, especially, for rich mixtures of hydrocarbons with air, the theory over-predicted pressure rise since it does not account for soot formation and the associated energy losses by radiation. Experimental investigation of propane and hydrogen deflagration was conducted in a partially confined space and the theory-based predictions agreed with the data up to 5%. Parametric numerical study was performed to investigate the effect of the initial pressure and temperature of gaseous fuels on pressure rise. (C) 2017 Elsevier Masson SAS. All rights reserved