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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 1,693 records · Page 94
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Chemical and petrographic characterization of amorphous silicate material in cometary GEMS

Amorphous silicate material (ASM) is found in the matrix of GEMS (glass with embedded metal and sulfides) in chondritic porous interplanetary dust particles (CP-IDPs) and in the matrices of primitive chondritic meteorites. It either formed by irradiation of crystalline precursors in the interstellar medium or by non-equilibrium condensation in the solar nebula. However, the origins of ASM in IDPs and chondrites and their possible relationship are still not well constrained. Here we performed a petrographic and chemical characterization of ASM in five CP-IDPs by Transmission Electron Microscopy (TEM)techniques. We also analyzed carbon and nitrogen isotopic compositions of organic matter by Nano SIMS to constrain the pristine character of analyzed IDPs. ASM in IDPs is depleted in all major element/Si ratios with respect to the solar value. Compared to bulk GEMS analyses, the ASM contains less Fe, because nanophase inclusions of Fe-Ni-metal and FeS are mostly excluded by our approach. In contrast, ASM in meteorites has higher-than-solar Fe/Si ratios, maybe due to aqueous alteration on the meteorite parent bodies. Chemical composition of GEMS ASM indicates a non-equilibrium condensation origin. Silicone oil contamination of particles during collection is excluded, because GEMS collected in dry polyurethane show similar compositions. Magnetite rims around GEMS in our IDP samples indicate heating of some particles during atmospheric entry. However, preserved 15N and13C isotopic anomalies in organic matter around GEMS and in IDP matrix link the IDPs to a cold environment and overall validate their primitiveness.

Birgit Schulz↗
NASA NTRS2023

Thermomechanical Property Prediction of Amorphous and Crystal PEKK via Molecular Dynamics

Traditionally, advanced aerospace composites have been manufactured using thermoset resins. However, recently, thermoplastics have been investigated for use in the manufacturing of composite materials due to their unique manufacturing characteristics. Thermoplastic resins can be reshaped and formed, along with the added benefit of being recyclable, which thermoset resin cannot. Thermoplastic materials undergo a crystallization process during manufacturing which affects the percent crystallinity of the material. The crystallization needs to be understood better to maximize the potential of thermoplastic resins. PEKK is a thermoplastic material with good chemical, thermal, and mechanical loading resistance. PEKK is also a material NASA is interested in for developing new bonded joint technology. The crystalline microstructure of PEKK is at the micrometer length scale, and it is of interest to model the effects of the crystallinity structure on PEKK’s bulk properties. Molecular dynamics (MD) is a simulation tool that allows for property-structure relationships between atomistic structure and nanometer-length portions of a material. This makes MD a useful tool for developing the structure-property relationship of PEKK. However, the micrometer length scale of PEKK’s crystal structure is too large for MD. Thus, a hybrid approach to modeling PEKK’s microstructure is proposed in this work where MD models are built of both the amorphous and crystalline phases of PEKK. The engineering material properties can be obtained using MD at the nanometer length scale. A micromechanics approach can then generate the micrometer length scale of the crystallinity and the effective properties can be homogenized. The objective of this paper is to show the MD model workflow and the MD-predicted properties of PEKK. The properties can then be homogenized with different crystalline percentages to build design graphs that can be used to tailor PEKK for specific composite applications.

poly ether ketone ketone↗
NASA NTRS2022

29P/Schwassmann–Wachmann 1: A Rosetta Stone for Amorphous Water Ice and CO↔CO 2 Conversion in Centaurs and Comets?

Centaur 29P/Schwassmann–Wachmann 1 (SW1) is a highly active object orbiting in the transitional "Gateway" region between the Centaur and Jupiter-family comet (JFC) regions. SW1 is unique among the Centaurs in that it experiences quasi-regular major outbursts and produces CO emission continuously; however, the source of the CO is unclear. We argue that, due to its very large size (∼32 km radius), SW1 is likely still responding, via amorphous water ice (AWI) conversion to crystalline water ice (CWI), to the "sudden" change in its external thermal environment produced by its Myrs-long dynamical migration from the Kuiper Belt to its current location at the inner edge of the Centaur region. It is this conversion process that is the source of the abundant CO and dust released from the object during its quiescent and outburst phases. If correct, these arguments have a number of important predictions testable via remote sensing and in situ spacecraft characterization, including the quick release on Myr timescales of CO from AWI conversion for any few kilometer-scale scattered disk Kuiper Belt Objects transiting into the inner system; that to date SW1 has only converted between 50% and 65% of its nuclear AWI to CWI; that volume changes on AWI conversion could have caused subsidence and cave-ins, but not significant mass wasting or crater loss; that SW1's coma should contain abundant amounts of CWI+CO 2 "dust" particles; and that when SW1 transits into the inner system within the next 10,000 yr, it will be a very different kind of JFC.

Centaur 29P/Schwassmann–Wachmann 1(SW1)↗
DOE OSTI2011

Magnetic Structure and Diffracted Magneto-optics of Patterned Amorphous Multilayers

We present magneto-optical Kerr effect measurements of patterned arrays of Co{sub 68}Fe{sub 24}Zr{sub 8}/Al{sub 2}O{sub 3} amorphous multilayers. The multilayers were patterned in two dimensions into two different arrangements of circular and ellipsoidal islands. Magnetization loops were recorded in a longitudinal geometry using both the specularly reflected beam as well as diffracted beams scattered off the patterned films. The magnetization of the patterned structures is significantly different from the magnetization of a continuous multilayer owing to the lateral confinement of the pattern and the introduction of additional dipolar coupling between the layers at the edges of the islands. By investigating the magnetic response at the different diffraction orders from the two different configurations of islands we are able to observe the magnetization at different length scales and determine the magnetic response of the circular and ellipsoidal islands individually.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2011

Reaction of Formic Acid over Amorphous Manganese Oxide Catalytic Systems: An In Situ Study

The interaction of formic acid with amorphous manganese oxide (AMO) is investigated using in situ photoelectron and infrared spectroscopy techniques. Soft X-ray photoelectron spectroscopy (sXPS) and in situ FTIR illustrate two possible modes of formate bound species at the AMO surface. Two peaks in the IR region from 1340-1390 cm{sup -1} are indicative of formate species bound to the surface in a bidentate configuration. However, a 224 cm{sup -1} band gap between v{sub s}OCO and v{sub as}OCO suggests formate is bound in a bridging configuration. Temperature-programmed desorption studies confirm the formate bound species desorbs as carbon dioxide from the surface at multiple binding sites. At temperatures above 700 K, the presence of K{sup +} {hor_ellipsis} OC complex suggests the bound species interacts at vacant sites related to framework oxygen and cation mobility.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Selective alkane activation with single-site atoms on amorphous support

The present invention relates generally to catalysts and methods for use in olefin production. More particularly, the present invention relates to novel amorphously supported single-center, Lewis acid metal ions and use of the same as catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Amorphous titania/carbon composite electrode materials

An isolated salt comprising a compound of formula (H.sub.2X)(TiO(Y).sub.2) or a hydrate thereof, wherein X is 1,4-diazabicyclo[2.2.2]octane (DABCO), and Y is oxalate anion (C.sub.2O.sub.4.sup.-2), when heated in an oxygen-containing atmosphere at a temperature in the range of at least about 275.degree. C. to less than about 400.degree. C., decomposes to form an amorphous titania/carbon composite material comprising about 40 to about 50 percent by weight titania and about 50 to about 60 percent by weight of a carbonaceous material coating the titania. Heating the composite material at a temperature of about 400 to 500.degree. C. crystallizes the titania component to anatase. The titania materials of the invention are useful as components of the cathode or anode of a lithium or lithium ion electrochemical cell.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Amorphous titania/carbon composite electrode materials

An isolated salt comprising a compound of formula (H2X)(TiO(Y)2) or a hydrate thereof, wherein X is 1,4-diazabicyclo[2.2.2]octane (DABCO), and Y is oxalate anion (C2O4−2), when heated in an oxygen-containing atmosphere at a temperature in the range of at least about 275° C. to less than about 400° C., decomposes to form an amorphous titania/carbon composite material comprising about 40 to about 50 percent by weight titania and about 50 to about 60 percent by weight of a carbonaceous material coating the titania. Heating the composite material at a temperature of about 400 to 500° C. crystallizes the titania component to anatase. The titania materials of the invention are useful as components of the anode of a lithium or lithium ion electrochemical cell.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Atomic-scale factors that control the rate capability of nanostructured amorphous Si for high-energy-density batteries

Nanostructured Si is the most promising high-capacity anode material to substantially increase the energy density of Li-ion batteries. Among the remaining challenges is its low rate capability as compared to conventional materials. To understand better what controls the diffusion of Li in the amorphous Li-Si alloy, we use a novel machine-learning potential trained on more than 40,000 ab-initio calculations and nanosecond-scale molecular dynamics simulations, to visualize for the first time the delithiation of entire LiSi nanoparticles. Our results show that the Si host is not static but undergoes a dynamic rearrangement from isolated atoms, to chains, and clusters, with the Li diffusion strongly governed by this Si rearrangement. We find that the Li diffusivity is highest when Si segregates into clusters, so that Li diffusion proceeds via hopping between the Si clusters. The average size of Si clusters and the concentration range over which Si clustering occurs can thus function as design criteria for the development of rate-improved anodes based on modified Si.

Artrith, Nongnuch↗
DOE OSTI2023

Extreme synthesis of crystalline aerogel materials from amorphous aerogel precursors

In one embodiment, a composition of matter includes a crystalline porous structure having a density in a range from about 30 to about 50 mg/cm 3 . In another embodiment, a kit includes an amorphous, porous material, an inert pressure medium, a heating source, and a sample chamber configured to withstand an applied pressure of at least about 20 GPa. Other aspects and embodiments of the present invention will become apparent from the following detailed description, which, when taken in conjunction with the drawings, illustrate by way of example the principles of the invention.

Pauzauskie, Peter J.↗
DOE OSTI2017

Hydrogen enhances the radiation resistance of amorphous silicon oxycarbides

Here, we use first principles molecular dynamics to investigate unit displacement processes in amorphoussilicon oxycarbides (SiOC) and demonstrate that the introduction of hydrogen (H) into these materialsenhances their radiation resistance. Our simulations show that 100 eV knock-ons in H-free SiOC redistribute C through the formation of CeO and CeC bonds. H counteracts this trend by passivating dangling O bonds and preventing C from coming out of solution. This effect arises from the exceptionally high mobility of H, which leads to the saturation of radiation-induced O and C radicals even before the thermal-spike induced by a high-energy knock-on dies down. Our work suggests that fully hydrogenated SiOC is a promising radiation-resistant material for future nuclear energy applications.

08 HYDROGEN↗