Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Ge”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ge(SF6)2 by Materials Project

GeF6(SF3)2 crystallizes in the orthorhombic Pnnm space group. The structure is zero-dimensional and consists of two GeF6 clusters and four SF3 clusters. In each GeF6 cluster, Ge4+ is bonded in an octahedral geometry to six F1- atoms. There is two shorter (1.83 Å) and four longer (1.84 Å) Ge–F bond length. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one Ge4+ atom. In the second F1- site, F1- is bonded in a single-bond geometry to one Ge4+ atom. In each SF3 cluster, S4+ is bonded in a 3-coordinate geometry to three F1- atoms. There is one shorter (1.56 Å) and two longer (1.57 Å) S–F bond length. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one S4+ atom. In the second F1- site, F1- is bonded in a single-bond geometry to one S4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ge(PbS2)2 by Materials Project

Pb2GeS4 crystallizes in the tetragonal I-42d space group. The structure is three-dimensional. there are four inequivalent Pb2+ sites. In the first Pb2+ site, Pb2+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of Pb–S bond distances ranging from 2.87–3.59 Å. In the second Pb2+ site, Pb2+ is bonded in a 4-coordinate geometry to four S2- atoms. There are two shorter (2.84 Å) and two longer (2.94 Å) Pb–S bond lengths. In the third Pb2+ site, Pb2+ is bonded to six S2- atoms to form distorted PbS6 pentagonal pyramids that share corners with two equivalent GeS4 tetrahedra and edges with two equivalent GeS4 tetrahedra. There are a spread of Pb–S bond distances ranging from 2.98–3.13 Å. In the fourth Pb2+ site, Pb2+ is bonded in a 4-coordinate geometry to eight S2- atoms. There are a spread of Pb–S bond distances ranging from 2.86–3.58 Å. Ge4+ is bonded to four S2- atoms to form GeS4 tetrahedra that share a cornercorner with one PbS6 pentagonal pyramid and an edgeedge with one PbS6 pentagonal pyramid. There are a spread of Ge–S bond distances ranging from 2.23–2.27 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a distorted single-bond geometry to three Pb2+ and one Ge4+ atom. In the second S2- site, S2- is bonded in a 1-coordinate geometry to three Pb2+ and one Ge4+ atom. In the third S2- site, S2- is bonded in a 1-coordinate geometry to three Pb2+ and one Ge4+ atom. In the fourth S2- site, S2- is bonded in a 1-coordinate geometry to four Pb2+ and one Ge4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ge(PbS2)2 by Materials Project

Pb2GeS4 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Pb2+ sites. In the first Pb2+ site, Pb2+ is bonded in a 6-coordinate geometry to six S2- atoms. There are a spread of Pb–S bond distances ranging from 2.82–3.55 Å. In the second Pb2+ site, Pb2+ is bonded to seven S2- atoms to form distorted PbS7 pentagonal bipyramids that share corners with four equivalent PbS7 pentagonal bipyramids, a cornercorner with one GeS4 tetrahedra, an edgeedge with one PbS7 pentagonal bipyramid, and edges with three equivalent GeS4 tetrahedra. There are a spread of Pb–S bond distances ranging from 2.85–3.49 Å. Ge4+ is bonded to four S2- atoms to form GeS4 tetrahedra that share a cornercorner with one PbS7 pentagonal bipyramid and edges with three equivalent PbS7 pentagonal bipyramids. There are a spread of Ge–S bond distances ranging from 2.22–2.25 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a 1-coordinate geometry to four Pb2+ and one Ge4+ atom. In the second S2- site, S2- is bonded in a 1-coordinate geometry to three Pb2+ and one Ge4+ atom. In the third S2- site, S2- is bonded in a 1-coordinate geometry to three Pb2+ and one Ge4+ atom. In the fourth S2- site, S2- is bonded in a distorted single-bond geometry to three Pb2+ and one Ge4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ge(C6F5)4 by Materials Project

Ge(C)4(CF)20 crystallizes in the tetragonal I4_1/a space group. The structure is zero-dimensional and consists of eighty fluoromethane molecules, four germanium molecules, and sixteen methane molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ge(NF3)2 by Materials Project

N2GeF6 is Calaverite structured and crystallizes in the monoclinic C2/m space group. The structure is zero-dimensional and consists of four ammonia molecules and two GeF6 clusters. In each GeF6 cluster, Ge4+ is bonded in an octahedral geometry to six F1- atoms. All Ge–F bond lengths are 1.83 Å. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one Ge4+ atom. In the second F1- site, F1- is bonded in a single-bond geometry to one Ge4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ge(NF3)2 by Materials Project

N2GeF6 crystallizes in the orthorhombic Cmc2_1 space group. The structure is zero-dimensional and consists of eight ammonia molecules and four GeF6 clusters. In each GeF6 cluster, Ge4+ is bonded in an octahedral geometry to six F1- atoms. There are a spread of Ge–F bond distances ranging from 1.81–1.84 Å. There are four inequivalent F1- sites. In the first F1- site, F1- is bonded in a single-bond geometry to one Ge4+ atom. In the second F1- site, F1- is bonded in a single-bond geometry to one Ge4+ atom. In the third F1- site, F1- is bonded in a single-bond geometry to one Ge4+ atom. In the fourth F1- site, F1- is bonded in a single-bond geometry to one Ge4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ge(NF3)2 by Materials Project

N2GeF6 is Fluorite structured and crystallizes in the cubic Fm-3m space group. The structure is zero-dimensional and consists of eight ammonia molecules and four GeF6 clusters. In each GeF6 cluster, Ge4+ is bonded in an octahedral geometry to six equivalent F1- atoms. All Ge–F bond lengths are 1.83 Å. F1- is bonded in a single-bond geometry to one Ge4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Successive magnetic orderings in the Ising spin chain magnet DyNi 5 Ge 3

In this report, we investigated a new rare-earth-based one-dimensional Ising spin chain magnet DyNi 5 Ge 3 by means of magnetization, specific heat, and powder neutron diffraction measurements. Due to the crystalline electrical field splitting, the magnetic Dy ions share an Ising-like ground doublet state. Owning to the local point symmetry, these Ising moments form into two canted magnetic sublattices, which were further confirmed by the angle-dependent magnetization measurement. In zero fields, two successive antiferromagnetic phase transitions were found at temperatures T N1 =6K and T N2 =5K, respectively. Only part of the moments are statically ordered in this intermediate state between T N1 and T N2 . Powder neutron diffraction experiments at different temperatures were performed as well. Further, an incommensurate magnetic propagation vector of k m =(0.5,0.4,0.5) was identified. The refined spin configurations through the irreducible representation analysis confirmed that these Ising spins are canted in the crystal ab plane.

36 MATERIALS SCIENCE↗
NASA NTRS2018

Optical Characterization of Fuel Injection in a Flame Tube Combustor Using a GE TAPS Injector Configuration

This paper presents results in which we compare fuel staging and its effect on fuel spray pattern, velocity and speciation during combustion for several inlet conditions using a GE TAPS injector configuration. Planar laser-induced fluorescence (PLIF), particle image velocimetry (PIV) and phase Doppler interferometry (PDI) were used to investigate spray patterns and velocity. The 2D PIV provides slices in the flow of axial-vertical or axial horizontal velocity components. With 3D PDI, we obtained 3 components of velocity, and fuel drop sizes. Chemiluminescence imaging and spontaneous Raman scattering (SRS) were used to investigate flame structure, species location and relative species concentration. Phase Doppler and PIV data were acquired using scatter from fuel droplets; therefore, those data were obtained only at the pilot-only test points. Raman measurements were acquired only at 10/90 split points to avoid droplets.

optical diagnostics↗
DOE OSTI2023

Direct Observation of Magnetic Bubble Lattices and Magnetoelastic Effects in van der Waals Cr 2 Ge 2 Te 6

Abstract Ferromagnetic van der Waals (vdW) materials are of large current interest for the fundamental study of low‐dimensional magnetism and for potential applications in multilayer heterostructures. Cr 2 Ge 2 Te 6 (CGT) is particularly exciting because it is a ferromagnetic semiconductor with tunable electronic and magnetic properties. Controlling the magnetic domain structure of CGT is a requirement for understanding its novel interface physics and for tuning behavior for potential devices. Herein, cryo‐Lorentz transmission electron microscopy is performed in the temperature range of 12–50K to directly image the magnetic domain structures in CGT. A rich phase diagram of domain structures including stripe domains, magnetic bubble lattices of mixed‐chirality, and topologically‐protected lattices of homochiral magnetic bubbles is observed. The types and chiralities of the bubbles can be controlled by topographical changes in the CGT flakes. Additionally, it is observed that in‐plane strain and magnetoelastic coupling can align and organize both bubble lattices and stripe domains. This study provides insights into creating and controlling complex magnetic domain structures for integration into multilayer heterostructures and for future studies of 2D magnetism.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Cathodoluminescence of Ultrathin Twisted Ge 1–x Sn x S van der Waals Nanoribbon Waveguides

Ultrathin van der Waals semiconductors have shown extraordinary optoelectronic and photonic properties. Propagating photonic modes make layered crystal waveguides attractive for photonic circuitry and for studying hybrid light-matter states. Accessing guided modes by conventional optics is challenging due to limited spatial resolution and poor out-of-plane far field coupling. Scanning near-field optical microscopy (SNOM) can overcome these issues and can characterize waveguide modes down to tens of nm resolution, albeit for planar samples or nanostructures with moderate height variations. Electron microscopy provides atomic-scale localization also for more complex geometries, and recent advances extended the accessible excitations from interband transitions to phonons. In this work, bottom-up synthesized layered semiconductor (Ge 1-x Sn x S) nanoribbons with axial twist and deep sub-wavelength thickness are demonstrated as a platform for realizing waveguide modes, and cathodoluminescence (CL) spectroscopy is introduced as a tool to characterize them. Combined experiments and simulations show the excitation of guided modes by the electron beam and their efficient detection via photons emitted in the ribbon plane, which enables measuring key properties such as the evanescent field into the vacuum cladding with nanometer resolution. The results identify van der Waals waveguides operating in the infrared and highlight an electron microscopy-based approach for probing complex-shaped nanophotonic structures.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Understanding the Reactivity of a Thin Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 Solid–State Electrolyte toward Metallic Lithium Anode

The thickness of solid-state electrolytes (SSEs) significantly affects the energy density and safety performance of all-solid-state lithium batteries. However, a sufficient understanding of the reactivity toward lithium metal of ultrathin SSEs (<100 μm) based on NASICON remains lacking. Herein, for the first time, a self-standing and ultrathin (70 μm) NASICON-type Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 (LAGP) electrolyte via a scalable solution process is developed, and X-ray photoelectron spectroscopy reveals that changes in LAGP at the metastable Li-LAGP interface during battery operation is temperature dependent. Severe germanium reduction and decrease in LAGP particle size are detected at the Li-LAGP interface at elevated temperature. As a result, oriented plating of lithium metal on its preferred (110) face occurs during in situ X-ray diffraction cycling.

25 ENERGY STORAGE↗
DOE OSTI2020

Vacancies and spin-phonon coupling in CrSi 0.8 Ge 0.1 Te 3

We report temperature-dependent Raman scattering and magnetization studies of van der Waals ferromagnetic compound CrSi 0.8 Ge 0.1 Te 3 . Magnetic susceptibility measurements revealed dominant ferromagnetic interactions below T C which shift to the lower values due to the presence of vacancies. A Raman active mode, additional to the ones predicted by symmetry in the parent compounds, has been observed. This A g symmetry mode most likely emerges as a consequence of the atomic vacancies on Si/Ge site. Presence of the strong spin–phonon coupling at temperature around 210 K is indicated by deviations from conventional phonon self-energy temperature dependence of all analysed modes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Electronic Properties of the Weyl Semimetals Co 2 MnX (X=Si, Ge, Sn)

Using first-principles electronic structure calculations, iwe show that ferromagnetic Heusler compounds Co2MnX (X = Si, Ge, Sn) present nontrivial topological characteristics and belong to the category of Weyl semimetals. These materials exhibit two topologically interesting band crossings near the Fermi level. These band crossings have complex 3D geometries in the Brillouin zone and are characterized by nontrivial topology as Hopf links and chain-like nodal lines that are protected by the perpendicular mirror planes. The spin–orbit interaction split these nodal lines into several 0D Weyl band crossings. Unlike previously known topologically nontrivial Heusler materials, these majority spin band crossings lie in or very near to the bandgap of minority spin bands, potentially facilitating experimental observation.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Magnetic transitions and magnetocaloric effect of Gd 4 Nd 1 Si 2 Ge 2

In this work, crystal structure and magnetic properties of the quaternary Gd 4 Nd 1 Si 2 Ge 2 compound were investigated using synchrotron X-ray diffraction and magnetic measurements. The compound crystallized into an orthorhombic structure in the temperature range 200-300 K. In zero field cooling, the compound undergoes a spin reorientation following a ferromagnetic-like transition at 276 K. The spin reorientation is hinted at by nonlinear changes of lattice parameters but is suppressed in a high magnetic field of 6 T. Magnetic measurements revealed a magnetocaloric effect with a high relative cooling power. It is suggested that Nd substitution for Gd enlarges magnetic anisotropy and induces a canted spin structure.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Cubic to hexagonal tuning in Fe 2 Mn(Si 1– x Ge x ) Heusler alloys

Here, the competition between the stability of the cubic and hexagonal full Heusler alloys and the implications concerning their magnetic properties were systematically studied through the detailed structural and magnetic characterization of the Fe 2 Mn(Si 1– x Ge x ) system. This system was specifically chosen as the parent compositions are cubic ( x = 0) and hexagonal ( x = 1). It is found that the formation of hexagonal phases occurs for the x ≥ 0.6 samples, whereas its phase fraction monotonically increases with x until the pure hexagonal Fe 2 MnGe is formed. The change in structure results in high sensitiveness of both the saturation of magnetization ($M_S$) and Curie temperature ($T_C$) with x values, related to a strong magnetocrystalline anisotropy of the hexagonal phase. Both cubic and hexagonal magnetic features were qualitatively reproduced by Density Functional Theory (DFT) calculations. This work provides an experimental and theoretical foundation for further design of Heusler systems with controlled structures and magnetic properties.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Magnetization distribution in Cu 0.6 Mn 2.4 Ge 2 ferromagnet from polarized and non-polarized neutron powder diffraction aided by density-functional theory calculations

The crystal structure and magnetic properties of Cu 0.6 Mn 2.4 Ge 2 have been re-investigated by a combination of extensive magnetic measurements and neutron scattering experiments, aided by electronic structure calculations. The material is found to be a soft ferromagnet with the ordering temperature T C = 316 K. The magnetocaloric effect evaluated from field-dependent magnetization isotherms is equal to 1.2 J/(kg·K) and 2.5 J/(kg·K) under the maximum applied magnetic field of 2 T and 5 T, respectively. The compound crystallizes in the hexagonal space group P6 3 /mmc. A complex structural disorder necessitated testing of several disorder models against the results of non-polarized and polarized neutron scattering experiments and magnetization measurements. Simulations at the density-functional theory level were also performed to identify the most robust solution that properly described the data observed. The final magnetic structure model reveals non-equal magnetic moments on the Mn1 and Mn2 atoms (2.29(9) µ B and 2.7(1) µ B , respectively) and the presence of vacancies and minor Cu substitution defects in both Mn sites. The work demonstrates how the non-polarized and polarized neutron scattering methods can be combined with electronic structure calculations to establish the microscopic structure of magnetic materials with complex crystallographic disorder.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗