65 research outputs found
Highly Conductive Graphene/Ag Hybrid Fibers for Flexible Fiber-Type Transistors
Mechanically robust, flexible, and electrically conductive textiles are highly suitable for use in wearable electronic applications. In this study, highly conductive and flexible graphene/Ag hybrid fibers were prepared and used as electrodes for planar and fiber-type transistors. The graphene/Ag hybrid fibers were fabricated by the wet-spinning/drawing of giant graphene oxide and subsequent functionalization with Ag nanoparticles. The graphene/Ag hybrid fibers exhibited record-high electrical conductivity of up to 15,800 S cm(-1). As the graphene/Ag hybrid fibers can be easily cut and placed onto flexible substrates by simply gluing or stitching, ion gel-gated planar transistors were fabricated by using the hybrid fibers as source, drain, and gate electrodes. Finally, fibertype transistors were constructed by embedding the graphene/Ag hybrid fiber electrodes onto conventional polyurethane monofilaments, which exhibited excellent flexibility (highly bendable and rollable properties), high electrical performance (mu(h) = 15.6 cm(2) V-1 s(-1), I-on/I-off > 10(4)), and outstanding device performance stability (stable after 1,000 cycles of bending tests and being exposed for 30 days to ambient conditions). We believe that our simple methods for the fabrication of graphene/Ag hybrid fiber electrodes for use in fiber-type transistors can potentially be applied to the development all-organic wearable devices.111912Ysciescopu
Microphysical characteristics of frozen droplet aggregates from deep convective clouds
During the 2012 Deep Convective Clouds and Chemistry
(DC3) experiment the National Science Foundation/National Center for
Atmospheric Research Gulfstream V (GV) aircraft sampled the upper anvils of
two storms that developed in eastern Colorado on 6 June 2012. A cloud
particle imager (CPI) mounted on the GV aircraft recorded images of ice
crystals at altitudes of 12.0 to 12.4 km and temperatures (T) from −61 to −55 ∘C.
A total of 22 393 CPI crystal images were analyzed, all with maximum
dimension (Dmax)<433 µm and with an average Dmax of
80.7±45.4 µm. The occurrence of well-defined pristine crystals
(e.g., columns and plates) was less than 0.04 % by number. Single frozen
droplets and frozen droplet aggregates (FDAs) were the dominant habits with
fractions of 73.0 % (by number) and 46.3 % (by projected area),
respectively. The relative frequency of occurrence of single frozen droplets
and FDAs depended on temperature and position within the anvil cloud.
A new algorithm that uses the circle Hough transform technique was developed
to automatically identify the number, size, and relative position of element
frozen droplets within FDAs. Of the FDAs, 42.0 % had two element frozen
droplets with an average of 4.7±5.0 element frozen droplets. The
frequency of occurrence gradually decreased with the number of element frozen
droplets. Based on the number, size, and relative position of the element
frozen droplets within the FDAs, possible three-dimensional (3-D)
realizations of FDAs were generated and characterized by two different shape
parameters, the aggregation index (AI) and the fractal dimension (Df),
that describe 3-D shapes and link to scattering properties with an
assumption of spherical shape of element frozen droplets. The AI of FDAs
decreased with an increase in the number of element frozen droplets, with
larger FDAs with more element frozen droplets having more compact shapes.
The Df of FDAs was about 1.20–1.43 smaller than that of black carbon
(BC) aggregates (1.53–1.85) determined in previous studies. Such a smaller
Df of FDAs indicates that FDAs have more linear chain-like branched
shapes than the compact shapes of BC aggregates. Determined morphological
characteristics of FDAs along with the proposed reconstructed 3-D
representations of FDAs in this study have important implications for
improving the calculations of the microphysical (e.g., fall velocity) and radiative
(e.g., asymmetry parameter) properties of ice crystals in upper anvil
clouds.</p
- …