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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on BN by Materials Project

BN is Boron Nitride-like structured and crystallizes in the monoclinic Cc space group. The structure is three-dimensional. there are two inequivalent B3+ sites. In the first B3+ site, B3+ is bonded in a trigonal planar geometry to three N3- atoms. There is two shorter (1.45 Å) and one longer (1.47 Å) B–N bond length. In the second B3+ site, B3+ is bonded in a trigonal planar geometry to three N3- atoms. There are a spread of B–N bond distances ranging from 1.44–1.49 Å. There are two inequivalent N3- sites. In the first N3- site, N3- is bonded in a trigonal planar geometry to three B3+ atoms. In the second N3- site, N3- is bonded in a trigonal planar geometry to three B3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BN by Materials Project

BN is Boron Nitride-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is two-dimensional and consists of two BN sheets oriented in the (0, 0, 1) direction. B3+ is bonded in a trigonal planar geometry to three equivalent N3- atoms. All B–N bond lengths are 1.45 Å. N3- is bonded in a trigonal planar geometry to three equivalent B3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaC64 by Materials Project

NaC64 is Boron Nitride-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is two-dimensional and consists of two natrium molecules and sixteen C sheets oriented in the (0, 0, 1) direction. In each C sheet, C+0.02- is bonded in a trigonal planar geometry to three equivalent C+0.02- atoms. There is one shorter (1.42 Å) and two longer (1.43 Å) C–C bond length.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BN by Materials Project

BN is Boron Nitride-like structured and crystallizes in the hexagonal P-6m2 space group. The structure is two-dimensional and consists of two BN sheets oriented in the (0, 0, 1) direction. B3+ is bonded in a trigonal planar geometry to three equivalent N3- atoms. All B–N bond lengths are 1.45 Å. N3- is bonded in a trigonal planar geometry to three equivalent B3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BN by Materials Project

BN is Boron Nitride-like structured and crystallizes in the hexagonal P6_3mc space group. The structure is two-dimensional and consists of two BN sheets oriented in the (0, 0, 1) direction. B3+ is bonded in a trigonal planar geometry to three equivalent N3- atoms. All B–N bond lengths are 1.45 Å. N3- is bonded in a trigonal planar geometry to three equivalent B3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BN by Materials Project

BN is Boron Nitride-like structured and crystallizes in the orthorhombic Fmm2 space group. The structure is two-dimensional and consists of two BN sheets oriented in the (0, 0, 1) direction. B3+ is bonded in a trigonal planar geometry to three equivalent N3- atoms. All B–N bond lengths are 1.45 Å. N3- is bonded in a trigonal planar geometry to three equivalent B3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on GaN by Materials Project

GaN is Boron Nitride-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is two-dimensional and consists of two GaN sheets oriented in the (0, 0, 1) direction. Ga3+ is bonded in a trigonal planar geometry to three equivalent N3- atoms. All Ga–N bond lengths are 1.85 Å. N3- is bonded in a trigonal planar geometry to three equivalent Ga3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CdS by Materials Project

CdS is Boron Nitride-like structured and crystallizes in the trigonal P3m1 space group. The structure is two-dimensional and consists of one CdS sheet oriented in the (0, 0, 1) direction. Cd2+ is bonded in a trigonal planar geometry to three equivalent S2- atoms. All Cd–S bond lengths are 2.46 Å. S2- is bonded in a trigonal planar geometry to three equivalent Cd2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BrO by Materials Project

BrO is Boron Nitride-like structured and crystallizes in the trigonal R3m space group. The structure is two-dimensional and consists of three BrO sheets oriented in the (0, 0, 1) direction. O is bonded in a trigonal planar geometry to three equivalent Br atoms. All O–Br bond lengths are 2.20 Å. Br is bonded in a trigonal planar geometry to three equivalent O atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BC by Materials Project

BC1 is Boron Nitride-like structured and crystallizes in the hexagonal P-6m2 space group. The structure is two-dimensional and consists of one BC1 sheet oriented in the (0, 0, 1) direction. B3+ is bonded in a trigonal planar geometry to three equivalent C3- atoms. All B–C bond lengths are 1.55 Å. C3- is bonded in a trigonal planar geometry to three equivalent B3+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRS1997

Computational Modeling in Structural Materials Processing

High temperature materials such as silicon carbide, a variety of nitrides, and ceramic matrix composites find use in aerospace, automotive, machine tool industries and in high speed civil transport applications. Chemical vapor deposition (CVD) is widely used in processing such structural materials. Variations of CVD include deposition on substrates, coating of fibers, inside cavities and on complex objects, and infiltration within preforms called chemical vapor infiltration (CVI). Our current knowledge of the process mechanisms, ability to optimize processes, and scale-up for large scale manufacturing is limited. In this regard, computational modeling of the processes is valuable since a validated model can be used as a design tool. The effort is similar to traditional chemically reacting flow modeling with emphasis on multicomponent diffusion, thermal diffusion, large sets of homogeneous reactions, and surface chemistry. In the case of CVI, models for pore infiltration are needed. In the present talk, examples of SiC nitride, and Boron deposition from the author's past work will be used to illustrate the utility of computational process modeling.

Meyyappan, Meyya↗
NASA NTRS2019

Failure of Nd:YVO4 Amplifier Crystals

Brittle single crystals are used in NASA applications ranging from lenses to centrally heated laser slabs. Despite standard procedures to design such components, unexpected failures occasionally occur. The ICEsat-2 (Ices,Cloud, and Elevation satellite-2) employs Yttrium orthovanadate single crystals in laser amplifiers and oscillators. Although the systems are currently flying and successfully operating, some unexpected crystal fractures occurred just prior to flight. The failures were traced to poor crystal quality along with time-dependent chemical reaction within the system assembly that increased stress beyond expectations and promoted both fast fracture and stress corrosion. This presentation will discuss failure analysis of the crystals and the chemical reactions that promoted failures, along with corrective actions taken to reduce likelihood of fracture over the three-year mission. Re-designed lasers were stored for 12 months and operated for a total of 1,000 hours without signs of degradation.

Design↗
NASA NTRSDate not supplied

Thermally Conductive Insulation for High Power Density Electric Machines

In the mid 2000’s NASA challenged the aeronautics industry to identify the routes for achieving ambitious improvements in fuel burn, emission, and noise reductions. These so-called “N+3” studies were exploring broad changes three commercial aircraft generations, or nominally 30 years, in the future. Many intriguing propulsion-airframe integrated solutions were proposed and pursued, which incorporated technologies such as high-aspect-ratio wings, boundary-layer ingestion, and hybrid electric powertrains. This talk summarizes the approaches and achievements from the Hybrid Gas-Electric Propulsion Concept Technical Challenge that concluded in 2019. The balanced portfolio of concepts studies anchored with practical technology development demonstrated that electrified aircraft propulsion is an aircraft revolution whose time has come. Advanced materials will play a key role with enabling the increase in operating efficiencies and lifetime of these high power-dense electric machines. Progress made in materials development as part of NASA’s Advanced Air Transport Technology project will also be discussed.

electrical insulation↗
NASA NTRSDate not supplied

Potential of Materials to Impact Megawatt-Scale Electric Machines

High specific power density, megawatt-scale electric machines (motors and generators) are needed to enable megawatt-scale electric aircraft propulsion systems for single isle aircraft. Thermally insulating electrical insulation materials in the stator windings limits the ability to thermally manage the heat produced in these machines. Polymer-ceramic composites along with novel processing techniques offer viable options to improve the thermal conductivity of the electrical insulation system. This paper outlines current National Aeronautics and Space Administration’s Glenn Research Center efforts of developing several polymer-ceramic systems and processing techniques as they relate to electric machine insulation (including potting). There is also analysis of how these factors relate to machine performance.

electric macnhine↗
NASA NTRSDate not supplied

Toughening of Boron Carbide Composites by Hierarchical Microstructuring

Due to a unique combination of properties including high hardness, low density, chemical and thermal stability, semi-conductivity, and high neutron absorption, boron carbide (B4C) is a potential candidate for various applications involving extreme environment. However, B4C’s current application is limited because of its low fracture toughness. In this study, a hierarchical microstructure design with features including TiB2 grains and graphite platelets was used to toughen B4C by simultaneously utilizing multiple toughening mechanisms including crack deflection, bridging, and micro-crack toughening. Using field-assisted sintering technology (FAST), B4C composites with dense and hierarchical microstructure were fabricated. Previously, the fracture toughness of fabricated B4C composites was measured at micro-scale using micro-indentation to have up to 56% improvement. In this work, the B4C composites’ fracture toughness was characterized at macro-scale using four-point bending methods and compared with previous results obtained at micro-scale. Micromechanics modeling of fracture behaviors for B4C-TiB2 composites was also performed to evaluate the contributions from experimentally observed toughening mechanisms. From four-point bending tests, B4C composites reinforced with both TiB2 grains (~15 vol%) and graphite platelets (~8.7 vol%) exhibited the highest fracture toughness enhancement from 2.38 to 3.65 MPa∙m^(1/2). The measured values were lower than those obtained using micro-indentation but maintained the general trends. The discrepancy between the indentation and four-point bending test results originated from the complex deformation behaviors triggered by the high contact load during indentation tests. Through micromechanics modeling, introduced thermal residual stress due to thermal expansion mismatch between B4C and TiB2, and weak interphases at B4C-TiB2 boundaries were identified as the main causes for experimentally observed toughness enhancement. These results proved the effectiveness of hierarchical microstructure designs for B4C toughening and can provide reference for the future design of B4C composites with optimized microstructures for further fracture toughness enhancement.

composites↗