Transformation of boron nitride from cubic to hexagonal under 1-atm helium
Not Available
36 MATERIALS SCIENCE↗
Engineering topics
Worsley, M. A.
Publications and source records attributed to Worsley, M. A..
Replication Data for: Toward digitally controlled catalyst architectures: Hierarchical nanoporous gold via 3D printing
The data underlying this published work have been made publicly available in this repository as part of the IMASC Data Management Plan. This work was supported as part of the Integrated Mesoscale Architectures for Sustainable Catalysis (IMASC), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # DE-SC0012573.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Chlorine-free, monolithic lanthanide series rare earth oxide aerogels via epoxide-assisted sol-gel method
Synthesis of chlorine-free, rare earth oxide aerogels from the lanthanide series was achieved using a modified epoxide-assisted sol-gel method. An ethanolic solution of the hydrated metal nitrate, propylene oxide, and ammonium carbonate was found to gel upon heating to 333 K. Critical point drying of the wet gel in CO 2 yielded monolithic aerogels. Most of the aerogels were amorphous as-prepared, but became nano-crystalline after calcination at 923 K in air. The aerogels had high surface areas (up to 150 m 2 /g), low densities (40–225 mg/cm 3 ), and were photoluminescent.
Rietveld refinement↗
Hydrogen Crystallization in Low-Density Aerogels
Crystallization of liquids confined in disordered low-density nanoporous scaffolds is poorly understood. Here in this work, we use relaxation calorimetry to study the liquid–solid phase transition of H 2 in a series of silica and carbon (nanotube- and graphene-based) aerogels with porosities ≳94%. Results show that freezing temperatures of H 2 inside all the aerogels studied are depressed but do not follow predictions of the Gibbs–Thomson theory based on average pore diameters measured by conventional gas sorption techniques. Instead, we find that, for each material family investigated, the depression of average freezing temperatures scales linearly with the ratio of the internal surface area (measured by gas sorption) and the total pore volume derived from the density of aerogel monoliths. The slope of such linear dependences is, however, different for silica and carbon aerogels, which we attribute to microporosity of carbons and the presence of macropores in silica aerogels. In conclusion, our results have important implications for the analysis of pore size distributions of low-density nanoporous materials and for controlling crystallization of fuel layers in targets for thermonuclear fusion energy applications.
08 HYDROGEN↗
Liquid–solid phase transition of hydrogen and deuterium in silica aerogel
Behavior of hydrogen isotopes confined in disordered low-density nanoporous solids remains essentially unknown. Here, we use relaxation calorimetry to study freezing and melting of H 2 and D 2 in an ~85%-porous base-catalyzed silica aerogel. In this work, we find that liquid–solid transition temperatures of both isotopes inside the aerogel are depressed. The phase transition takes place over a wide temperature range of ~4 K and non-trivially depends on the liquid filling fraction, reflecting the broad pore size distribution in the aerogel. Undercooling is observed for both H 2 and D 2 confined inside the aerogel monolith. Lastly, results for H 2 and D 2 are extrapolated to tritium-containing hydrogens with the quantum law of corresponding states.
36 MATERIALS SCIENCE↗
Optimizing supercapacitor electrode density: achieving the energy of organic electrolytes with the power of aqueous electrolytes
The value of electrode density is often overlooked in the pursuit of impressive supercapacitor metrics. Low-density electrodes deliver the best performance in terms of gravimetric energy and power densities when only the mass of the electrodes is considered. However, energy and power values with respect to the total system mass (electrode + electrolyte) or volume are more meaningful for practical application. Low-density electrodes are impractical due to both large mass contributions by the electrolyte and large system volumes. In this work, we use highly compressible graphene aerogel electrodes (up to 87.5% volumetric compression) to systematically characterize the effects of electrode density on energy and power metrics. The results reveal that electrode density is similar to electrode thickness in that both parameters have a squared effect on power. Accounting for the aqueous electrolyte's mass lowered the gravimetric energy and power by almost an order of magnitude for 0.144 g cm –3 dense carbon electrodes but only by a factor of 1.5 when the electrode density was increased to 1.15 g cm –3 through compression. The high-density electrodes achieve 8 W h kg –1 , 70 000 W kg –1 , and 144 F cm –3 in a symmetric electrode setup after factoring in the aqueous electrolyte's mass. Therefore, in the pursuit of high energy per mass, it can be just as effective to lower the system's mass with smaller electrolyte fractions as it is to use electrolytes with larger voltage ranges. High electrode densities allow aqueous electrolyte supercapacitors to attain energy densities per the system mass comparable to those of commercially-available organic electrolyte supercapacitors while maintaining 10–100× greater power.
25 ENERGY STORAGE↗
Robust nanoporous alumina monoliths by atomic layer deposition on low-density carbon-nanotube scaffolds
Abstract not provided
36 MATERIALS SCIENCE↗
Nanoporous Cu-C composites based on carbon-nanotube aerogels
Current synthesis methods of nanoporous Cu–C composites offer limited control of the material composition, structure, and properties, particularly for large Cu loadings of ≳20 wt%. Here, we describe two related approaches to realize novel nanoporous Cu–C composites based on the templating of recently developed carbon-nanotube aerogels (CNT-CAs). Our first approach involves the trapping of Cu nanoparticles while CNT-CAs undergo gelation. This method yields nanofoams with relatively high densities of ≳65 mg cm -3 for Cu loadings of ≳10 wt%. Our second approach overcomes this limitation by filling the pores of undoped CNT-CA monoliths with an aqueous solution of CuSO 4 followed by (i) freeze-drying to remove water and (ii) thermal decomposition of CuSO 4 . With this approach, we demonstrate Cu–C composites with a C matrix density of -25 mg cm -3 and Cu loadings of up to 70 wt%. These versatile methods could be extended to fabricate other nanoporous metal–carbon composite materials geared for specific applications.
Charnvanichborikarn, S.↗
Fusion Application Targets
Complex target structures are necessary to take full advantage of the unique laboratory environment created by inertial confinement fusion experiments. For example, uses-ofignition targets that contain a thin layer of a low density nanoporous material inside a spherical ablator shell allow placing dopants in direct contact with the DT fuel. The ideal foam for this application is a low-density hydrocarbon foam that is strong enough to survive wetting with cryogenic hydrogen, and low enough in density (density less than ~30 mg/cc) to not reduce the yield of the target. Here, we discuss the fabrication foamlined uses-of-ignition targets, and the development of low-density foams that can be used for this application.
36 MATERIALS SCIENCE↗