4 research outputs found
Characterization of Underwater Stability of Superhydrophobic Surfaces Using Quartz Crystal Microresonators
We
synthesized porous aluminum oxide nanostructures directly on
a quartz crystal microresonator and investigated the properties of
superhydrophobic surfaces, including the surface wettability, water
permeation, and underwater superhydrophobic stability. After increasing
the pore diameter to 80 nm (AAO80), a gold film was deposited onto
the AAO80 membrane, and the pore entrance size was reduced to 30 nm
(AAO30). The surfaces of the AAO80 and AAO30 were made to be hydrophobic
through chemical modification by incubation with octadecanethiol (ODT)
or octadecyltrichlorosilane (OTS), which produced three different
types of superhydrophobic surfaces on quartz microresonators: OTS-modified
AAO80 (OTS-AAO80), ODT-modified AAO30 (ODT-AAO30), and ODT–OTS-modified
AAO30 (TS-AAO30). The loading of a water droplet onto a microresonator
or the immersion of a resonator into water induced changes in the
resonance frequency that corresponded to the water permeation into
the nanopores. TS-AAO30 exhibited the best performance, with a low
degree of water permeation, and a high stability. These features were
attributed to the presence of sealed air pockets and the narrow pore
entrance diameter
Hybrid Copper–Silver Conductive Tracks for Enhanced Oxidation Resistance under Flash Light Sintering
We
developed a simple method to prepare hybrid copper–silver conductive
tracks under flash light sintering. The developed metal nanoparticle-based
ink is convenient because its preparation process is free of any tedious
washing steps. The inks were composed of commercially available copper
nanoparticles which were mixed with formic acid, silver nitrate, and
diethylene glycol. The role of formic acid is to remove the native
copper oxide layer on the surface of the copper nanoparticles. In
this way, it facilitates the formation of a silver outer shell on
the surface of the copper nanoparticles through a galvanic replacement.
In the presence of formic acid, the copper nanoparticles formed copper
formate, which was present in the unsintered tracks. However, under
illumination by a xenon flash light, the copper formate was then converted
to copper. Moreover, the resistance of the copper-only films increased
by 6 orders of magnitude when oxidized at high temperatures (∼220
°C). However, addition of silver nitrate to the inks suppressed
the oxidation of the hybrid copper–silver films, and the resistance
changes in these inks at high temperatures were greatly reduced. In
addition, the hybrid inks proved to be advantageous for use in electrical
circuits as they demonstrated a stable electrical conductivity after
exposure to ambient air at 180 °C
Magnetorheological Elastomer Films with Tunable Wetting and Adhesion Properties
We fabricated magnetorheological
elastomer (MRE) films consisting of polydimethylÂsiloxane and
various concentrations of fluorinated carbonyl iron particles. The
application of a magnetic field to the MRE film induced changes in
the surface morphology due to the alignment of the iron particles
along the magnetic field lines. At low concentrations of iron particles
and low magnetic field intensities, needle-like microstructures predominated.
These structures formed more mountain-like microstructures as the
concentration of iron particles or the magnetic field intensity increased.
The surface roughness increased the water contact angle from 100°
to 160° and decreased the sliding angle from 180° to 10°.
The wettability and adhesion properties changed substantially within
a few seconds simply upon application of a magnetic field. Cyclical
measurements revealed that the transition was completely reversible
Hybrid Copper–Silver–Graphene Nanoplatelet Conductive Inks on PDMS for Oxidation Resistance Under Intensive Pulsed Light
A simple,
low-cost, and reliable process of production for conductive tracks
and their transfer to polyÂ(dimethylsiloxane) (PDMS) substrate has
been proposed. Flexible electrodes were fabricated using conductive nanoparticulates under intensive
pulsed light, which were then transferred on to a PDMS substrate via
a pouring, curing, and peeling process. The combination of copper–silver
nitrate–graphene nanoplatelets (GnPs) provided multiple benefits
to the conductive tracks, such as oxidation resistance and increased
durability on PDMS. The addition of silver nitrate reduced the speed
of oxidation during the curing process of PDMS in the presence of
heat and air. The addition of GnPs then increased the stability of
conductive tracks on PDMS, whereas the films without GnPs were not
conductive on PDMS due to mechanical cracks. The copper–silver–GnP
electrodes on PDMS were successfully demonstrated as flexible electrodes
and reveal the enhancement of oxidation resistance during thermal
oxidation for Joule heater application