Although
high-entropy alloys have been intensively studied in the
past decade, there are still many requirements for manufacturing processes
and application directions to be proposed and developed, but most
techniques are focused on high-entropy bulk materials and surface
coatings. We fabricated high-entropy ceramic (HEC) nanomaterials using
simple pulsed laser irradiation scanning on mixed salt solutions (PLMS
method) under low-vacuum conditions. This method, allowing simple
operation, rapid manufacturing, and low cost, is capable of using
various metal salts as precursors and is also suitable for both flat
and complicated 3D substrates. In this work, we engineered this PLMS
method to fabricate high-entropy ceramic oxides containing four to
seven elements. To address the catalytic performance of these HEC
nanomaterials, we focused on CoCrFeNiAl high-entropy oxides applied
to the oxygen-evolution reaction (OER), which is considered a sluggish
process in water. We performed systematic material characterization
to solve the complicated structure of the CoCrFeNiAl HEC as a spinel
structure, AB2O4 (A, B = Co, Cr, Fe, Ni, or
Al). Atoms in A and B sites in the spinel structure can be replaced
with other elements; either divalent or trivalent metals can occupy
the spinel lattice using this PLMS process. We applied this PLMS method
to manufacture electrocatalytic CoCrFeNiAl HEC electrodes for the
OER reaction, which displayed state-of-the-art activity and stability.
By incorporating electron-accepting benzimidazole and electron-donating indolo [3,2-b]carbazole into one molecule, two novel donor-acceptor bipolar host materials, TICCBI and TICNBI, have been synthesized. The photophysical and electrochemical properties of the hybrids can be tuned through the different linkages (C-or N-connectivity) between the electronic donor and acceptor components. The promising physical properties of these two new compounds made them suitable for use as hosts doped with various Ir or Os-based phosphors for realizing highly efficient phosphorescent organic light emitting diodes (PhOLEDs). PhOLEDs using TICCBI and TICNBI as hosts incorporated with Irbased emitters such as green (PPy) 2 Ir(acac), yellow (Bt) 2 Ir(acac), and two new red emitters (35dmPh-6Fiq) 2 Ir(acac) (i3) and (4tBuPh-6Fiq) 2 Ir(acac) (i6) accomplished high external quantum efficiencies ranging from 14 to 16.2%. Nevertheless, the red PhOLED device incorporating TICNBI doped with the red emitter osmium(II) bis[3-(trifluoromethyl)-5-(4-tert-butylpyridyl)-1,2,4-triazolate] dimethylphenylphosphine [Os(bpftz) 2 (PPhMe 2 ) 2 ] achieved a maximum external quantum efficiency, current efficiency, and power efficiency of 22%, 28 cd A À1 , and 22.1 lm W À1 , respectively, with CIE coordinates of (0.65,0.35). The external quantum efficiency remained high (20%) as the brightness reached to 1000 cd m À2 , suggesting balanced charge fluxes within the emitting layer, rendering devices with limited efficiency roll-off.
We report the observation of thermal-induced optical guiding and bistability in a mid-IR cw, singly resonant optical parametric oscillator (SRO) at approximately 3.2 microm. The SRO employs a MgO:PPLN crystal as the gain medium and a 1-nm-linewidth Yb-fiber laser at 1.064 microm as the pump source. As soon as the pump power reaches the thermal guiding threshold at 16.5 W, the SRO shows a step increase in the parametric efficiency by a factor of 2.5. At 25 W pump power, the SRO generated 5.3 and 1.2 W at 1.58 and 3.23 microm, respectively, with single-longitudinal-mode performance for the 3.23 microm radiation.
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