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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 343 records · Page 19

Effect of Epitaxial-Structure Design and Growth Parameters on the Characteristics of Metamorphic Lasers of the 1.46-μm Optical Range Based on Quantum Dots Grown on GaAs Substrates

The characteristics of lasers of the 1.44–1.46-μm optical range grown on GaAs substrates using a metamorphic buffer are studied. The active region of the laser contains 10 rows of InAs/In{sub 0.4}Ga{sub 0.6}As/In{sub 0.2}Ga{sub 0.8}As quantum dots. It is shown that the use of special selective high-temperature annealing along with the application of short-period In{sub 0.2}Ga{sub 0.8}As/In{sub 0.2}Al{sub 0.3}Ga{sub 0.5}As short-period superlattices makes it possible to substantially decrease the density of threading dislocations in the active region. A threshold current density of 1300 A cm{sup –2}, external differential quantum efficiency of 38%, and maximal pulsed-mode output power of 13 W are attained for a laser with a broad area 3 mm in length.

36 MATERIALS SCIENCE↗

Improved Structural Design and CO 2 Capture of Porous Hydroxy-Rich Polymeric Organic Frameworks

Polymeric organic frameworks (POFs) are tunable and robust porous materials with potential applications for gas capture, catalysis, and separations technologies. A series of new porous POFs have been synthesized from the reaction of phloroglucinol or resorcinol derivatives with aryl aldehyde precursors. The monomers have various molecular shapes including linear, bent, trigonal, and tetrahedral geometries. Depending on the size and geometric matching of the monomers, the polymers are dominantly microporous with some mesoporous character or they are non-porous. In addition to standard spectroscopic and surface characterization, the materials were screened as adsorbents for carbon dioxide capture at low pressure (0-1 bar). The best performing material (POF 1D) has a CO 2 capture capacity of 9.0 wt. % (2.04 mmol g -1 ) at 298 K and 1 bar which is comparable to other polymeric organic frameworks. Isosteric heats of adsorption for POF 1A, POF 2A, and POF 2B were found to be dependent on the weight percent of CO 2 adsorbed: this suggests there are both chemisorptive and physisorptive components of CO 2 capture by the POFs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗