46 research outputs found
Non-isothermal drop impact and evaporation on polymer nanofiber mats
The work describes the experimental and theoretical investigation of water drop impact onto electrospun polymer nanofiber mats deposited on heated stainless-steel foils. The measurements encompass water spreading over and inside the mat, as well as the corresponding thermal field. The results show that the presence of polymer nanofiber mats prevents receding motion of drops after their complete spreading and promotes the moisture spreading inside the mat over a large area of the heater, which facilitates a tenfold enhancement of heat removal as the latent heat of drop evaporation
The inverse-Leidenfrost phenomenon on nanofiber mats on hot surfaces
The Leidenfrost effect is a technically and industrially important phenomenon that severely restricts heat removal from high-heat-flux surfaces. A simple remedy to the Leidenfrost effect is provided by polymer nanofiber mats created and deposited by electrospinning on stainless steel surfaces. The influence of nanofiber mats on hydrodynamics and cooling efficiency of single drop impact onto hot surfaces has been investigated experimentally. The evolution of the drops has been recorded by a high-speed complimentary metal-oxide
semiconductor camera, whereas the cooling temperature was measured by a thermocouple. A remarkable phenomenon was discovered: a mat of polymer nanofibers electrospun onto a heater surface can completely
suppress the Leidenfrost effect, thereby increasing the rate of heat removal from the surface to the liquid drops significantly. The “inverse-Leidenfrost” effect is described qualitatively and quantitatively, providing clear physical reasons for the observed behavior
Enantioselective Silylation of Aliphatic C−H Bonds for the Synthesis of Silicon‐Stereogenic Dihydrobenzosiloles
Enantioselective Silylation of Aliphatic C−H Bonds for the Synthesis of Silicon‐Stereogenic Dihydrobenzosiloles
Catalytic Enantioselective Synthesis of Silicon-Stereogenic Alkoxysilanes and Siloxanes
Regioselective Bromination of Fused Heterocyclic <i>N</i>‑Oxides
A mild method for the regioselective C2-bromination of fused azine <i>N</i>-oxides is presented, employing tosic anhydride as the activator and tetra-<i>n</i>-butylammonium bromide as the nucleophilic bromide source. The C2-brominated compounds are produced in moderate to excellent yields and with excellent regioselectivity in most cases. The potential extension of this method to other halogens, effecting C2-chlorination with Ts<sub>2</sub>O/TBACl is also presented. Finally, this method could be incorporated into a viable one-pot oxidation/bromination process, using methyltrioxorhenium/urea hydropgen peroxide as the oxidant