Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “GeAs”

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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Synthesis, Crystal Growth, and Transport Properties of van der Waals Tetrel Pnictide GeAs 2

Here, bulk GeAs 2 was synthesized utilizing a vapor transport reaction with iodine. Thermal stability tests under dynamic conditions show that GeAs 2 decomposes below 700 K, in contrast to the reported congruent melting at 1029 K measured at saturated As vapor pressure. GeAs 2 is a p-type narrow bandgap (~0.4 eV) semiconductor. From a thermoelectric standpoint, GeAs 2 outperforms previous computational predictions in thermopower and thermal conductivity. Yet, electrical resistivity is significantly higher than predicted values, resulting in the low overall thermoelectric figure of merit. Aliovalent doping strategies for GeAs 2 should be developed to achieve reasonable thermoelectric performance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on GeAs by Materials Project

GeAs is Hittorf-derived structured and crystallizes in the monoclinic C2/m space group. The structure is one-dimensional and consists of two GeAs ribbons oriented in the (0, 1, 0) direction. there are three inequivalent Ge3+ sites. In the first Ge3+ site, Ge3+ is bonded in a trigonal non-coplanar geometry to three As3- atoms. There are one shorter (2.48 Å) and two longer (2.49 Å) Ge–As bond lengths. In the second Ge3+ site, Ge3+ is bonded in a trigonal non-coplanar geometry to three As3- atoms. There are one shorter (2.49 Å) and two longer (2.50 Å) Ge–As bond lengths. In the third Ge3+ site, Ge3+ is bonded in a trigonal non-coplanar geometry to three As3- atoms. There are two shorter (2.50 Å) and one longer (2.52 Å) Ge–As bond lengths. There are three inequivalent As3- sites. In the first As3- site, As3- is bonded in a distorted T-shaped geometry to three Ge3+ atoms. In the second As3- site, As3- is bonded in a distorted T-shaped geometry to three Ge3+ atoms. In the third As3- site, As3- is bonded in a distorted T-shaped geometry to three Ge3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(GeAs)2 by Materials Project

Ba(GeAs)2 crystallizes in the tetragonal P4_2mc space group. The structure is three-dimensional. there are two inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a body-centered cubic geometry to eight equivalent As3- atoms. There are four shorter (3.54 Å) and four longer (3.61 Å) Ba–As bond lengths. In the second Ba2+ site, Ba2+ is bonded in a body-centered cubic geometry to eight equivalent As3- atoms. There are four shorter (3.42 Å) and four longer (3.49 Å) Ba–As bond lengths. There are two inequivalent Ge2+ sites. In the first Ge2+ site, Ge2+ is bonded in a water-like geometry to two equivalent As3- atoms. Both Ge–As bond lengths are 2.46 Å. In the second Ge2+ site, Ge2+ is bonded in a bent 120 degrees geometry to two equivalent As3- atoms. Both Ge–As bond lengths are 2.46 Å. As3- is bonded in a 6-coordinate geometry to four Ba2+ and two Ge2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on GeAs by Materials Project

GeAs is Halite, Rock Salt structured and crystallizes in the tetragonal I4mm space group. The structure is three-dimensional. Ge3+ is bonded to five equivalent As3- atoms to form a mixture of corner and edge-sharing GeAs5 square pyramids. There are one shorter (2.53 Å) and four longer (2.69 Å) Ge–As bond lengths. As3- is bonded to five equivalent Ge3+ atoms to form a mixture of corner and edge-sharing AsGe5 square pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb(GeAs)3 by Materials Project

Rb(GeAs)3 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Rb1+ is bonded in a 6-coordinate geometry to six As3- atoms. There are a spread of Rb–As bond distances ranging from 3.46–3.93 Å. There are three inequivalent Ge+2.67+ sites. In the first Ge+2.67+ site, Ge+2.67+ is bonded to four As3- atoms to form corner-sharing GeAs4 tetrahedra. There are a spread of Ge–As bond distances ranging from 2.45–2.50 Å. In the second Ge+2.67+ site, Ge+2.67+ is bonded in a distorted trigonal non-coplanar geometry to three As3- atoms. There are one shorter (2.52 Å) and two longer (2.53 Å) Ge–As bond lengths. In the third Ge+2.67+ site, Ge+2.67+ is bonded in a water-like geometry to two equivalent As3- atoms. Both Ge–As bond lengths are 2.56 Å. There are three inequivalent As3- sites. In the first As3- site, As3- is bonded to three equivalent Rb1+ and three Ge+2.67+ atoms to form distorted AsRb3Ge3 octahedra that share corners with two equivalent AsRb2Ge3 square pyramids, edges with four equivalent AsRb3Ge3 octahedra, and edges with three equivalent AsRb2Ge3 square pyramids. In the second As3- site, As3- is bonded to two equivalent Rb1+ and three Ge+2.67+ atoms to form distorted AsRb2Ge3 square pyramids that share corners with two equivalent AsRb3Ge3 octahedra, edges with three equivalent AsRb3Ge3 octahedra, and edges with two equivalent AsRb2Ge3 square pyramids. The corner-sharing octahedral tilt angles are 18°. In the third As3- site, As3- is bonded in a rectangular see-saw-like geometry to one Rb1+ and three Ge+2.67+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K(GeAs)3 by Materials Project

KGe3As3 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. K1+ is bonded in a 6-coordinate geometry to six As3- atoms. There are a spread of K–As bond distances ranging from 3.34–3.74 Å. There are three inequivalent Ge+2.67+ sites. In the first Ge+2.67+ site, Ge+2.67+ is bonded to four As3- atoms to form corner-sharing GeAs4 tetrahedra. There are a spread of Ge–As bond distances ranging from 2.45–2.50 Å. In the second Ge+2.67+ site, Ge+2.67+ is bonded in a distorted trigonal non-coplanar geometry to three As3- atoms. All Ge–As bond lengths are 2.52 Å. In the third Ge+2.67+ site, Ge+2.67+ is bonded in a water-like geometry to two equivalent As3- atoms. Both Ge–As bond lengths are 2.57 Å. There are three inequivalent As3- sites. In the first As3- site, As3- is bonded to three equivalent K1+ and three Ge+2.67+ atoms to form distorted AsK3Ge3 octahedra that share corners with two equivalent AsK2Ge3 square pyramids, edges with four equivalent AsK3Ge3 octahedra, and edges with three equivalent AsK2Ge3 square pyramids. In the second As3- site, As3- is bonded to two equivalent K1+ and three Ge+2.67+ atoms to form distorted AsK2Ge3 square pyramids that share corners with two equivalent AsK3Ge3 octahedra, edges with three equivalent AsK3Ge3 octahedra, and edges with two equivalent AsK2Ge3 square pyramids. The corner-sharing octahedral tilt angles are 19°. In the third As3- site, As3- is bonded in a rectangular see-saw-like geometry to one K1+ and three Ge+2.67+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRS2018

Flame Tube Testing of a GEA TAPS Injector: Effects of Fuel Staging on Combustor Fuel Spray Patterns, Flow Structure, and Speciation

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.

GE TAPS↗
DOE OSTI2023

Northward propagation of the Gulf of Elat-Aqaba constrained by cosmogenic burial ages and magnetostratigraphy of onshore sediments

The Gulf of Elat-Aqaba (GEA), located in the southern part of the Dead Sea Transform (DST), is one of the most active segments of the Dead Sea fault system. Yet, some fundamental details concerning its evolution in space and time are still not fully understood. To better constrain the tectonic history of this region, we study a succession of alluvial, lacustrine, and fluvial deposits in the north-western edge of the GEA, which belong to the Quaternary Eilot and Garof Fms. The Eilot Fm. represents low-energy shallow freshwater bodies and sabkhas, which predate the development of the deep part of the basin. Later, in response to the subsidence of the basin, the Garof Fm. was deposited in alluvial fans that built up following the increase in the depositional energy. Cosmogenic burial ages combined with magnetostratigraphy show that these Fms. were deposited as early as 3.03 Ma and as late as 1.65 Ma, depending on the applied age model. Considering the present depth of the northern GEA, this age indicates a maximum subsidence rate of the head of the GEA of ~1.98mm/yr. We suggest that faults along the onshore margin of the deep basin were active during the deposition of the Garof Fm. and subsequently became inactive, while the faulting activity migrated toward the center of the basin. In conclusion, closed Holocene basins north of the present seashore, such as the Elat and Evrona playas, which may represent a modern analogue to the Plio-Pleistocene morphology, raise the possibility that the GEA head is still propagating northward.

58 GEOSCIENCES↗
NASA NTRS1997

Error Analysis System for Spacecraft Navigation Using the Global Positioning System (GPS)

The Flight Dynamics Division (FDD) at the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC) is currently developing improved space-navigation filtering algorithms to use the Global Positioning System (GPS) for autonomous real-time onboard orbit determination. In connection with a GPS technology demonstration on the Small Satellite Technology Initiative (SSTI)/Lewis spacecraft, FDD analysts and programmers have teamed with the GSFC Guidance, Navigation, and Control Branch to develop the GPS Enhanced Orbit Determination Experiment (GEODE) system. The GEODE system consists of a Kalman filter operating as a navigation tool for estimating the position, velocity, and additional states required to accurately navigate the orbiting Lewis spacecraft by using astrodynamic modeling and GPS measurements from the receiver. A parallel effort at the FDD is the development of a GPS Error Analysis System (GEAS) that will be used to analyze and improve navigation filtering algorithms during development phases and during in-flight calibration. For GEAS, the Kalman filter theory is extended to estimate the errors in position, velocity, and other error states of interest. The estimation of errors in physical variables at regular intervals will allow the time, cause, and effect of navigation system weaknesses to be identified. In addition, by modeling a sufficient set of navigation system errors, a system failure that causes an observed error anomaly can be traced and accounted for. The GEAS software is formulated using Object Oriented Design (OOD) techniques implemented in the C++ programming language on a Sun SPARC workstation. The Phase 1 of this effort is the development of a basic system to be used to evaluate navigation algorithms implemented in the GEODE system. This paper presents the GEAS mathematical methodology, systems and operations concepts, and software design and implementation. Results from the use of the basic system to evaluate navigation algorithms implemented on GEODE are also discussed. In addition, recommendations for generalization of GEAS functions and for new techniques to optimize the accuracy and control of the GPS autonomous onboard navigation are presented.

Truong, S. H.↗
DOE OSTI2020

Materials Data on GeAs3 by Materials Project

GeAs(As)2 crystallizes in the tetragonal I4/mmm space group. The structure is two-dimensional and consists of two As sheets oriented in the (0, 0, 1) direction and two GeAs sheets oriented in the (0, 0, 1) direction. In each As sheet, As+1.33- is bonded in a square co-planar geometry to four equivalent As+1.33- atoms. All As–As bond lengths are 2.70 Å. In each GeAs sheet, Ge4+ is bonded in a square co-planar geometry to four equivalent As+1.33- atoms. All Ge–As bond lengths are 2.70 Å. As+1.33- is bonded in a square co-planar geometry to four equivalent Ge4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on GeAs3 by Materials Project

GeAs(As)2 crystallizes in the trigonal R3m space group. The structure is two-dimensional and consists of three As sheets oriented in the (0, 0, 1) direction and three GeAs sheets oriented in the (0, 0, 1) direction. In each As sheet, there are two inequivalent As+1.33- sites. In the first As+1.33- site, As+1.33- is bonded in a distorted T-shaped geometry to three equivalent As+1.33- atoms. All As–As bond lengths are 2.56 Å. In the second As+1.33- site, As+1.33- is bonded in a 3-coordinate geometry to three equivalent As+1.33- atoms. In each GeAs sheet, Ge4+ is bonded in a 3-coordinate geometry to three equivalent As+1.33- atoms. All Ge–As bond lengths are 2.48 Å. As+1.33- is bonded in a distorted trigonal non-coplanar geometry to three equivalent Ge4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Advancing a toolkit of diverse futures approaches for global environmental assessments

Global Environmental Assessments (GEAs) support national and international policy making for sustainable development. They rely on quantitative scenarios produced by Integrated Assessment Models (IAMs) to assess alternative futures. IAM-based scenarios can provide a coherent assessment framework that integrates different subsystems and their interactions. However, these top-down approaches have limited ability to represent key local dynamics, unexpected events, or the role of diverse actors. Other methods, including participatory scenarios, can help co-create narratives that emphasize diverse contents with clear links to existing decision-making. However, these bottom-up approaches provide only limited insight into global processes and are not constrained by measurable parameters. In our review, we identify four key challenges for current GEA scenarios: surprise, scale, diversity and imagination. We illustrate how these challenges can be overcome by combining top-down and bottom-up scenario approaches and conclude with a call to action for future research to take on this trans-disciplinary challenge.

Pereira, Laura M.↗
DOE OSTI2022

14 MeV Irradiation and Analysis of a 93% 239 Pu Target in Preparation for a F2019 FY22 Pu Campaign

In this work, we present the irradiation of a 93% 239 Pu with 14 MeV neutrons and subsequent analysis of the fission and activation products. The fully assembled target, a Pu metal bead encapsulated in Al, further encapsulated in welded stainless steel, was analyzed 22 times over more than 100 days using gamma emission analysis (GEA). Using the results from these analyses, R-values and fission yields for fission products were determined. To prepare for the FY22 Pu irradiation using the GODIVA critical assembly at NCERC, the irradiated Pu target was disassembled, dissolved, and separated using chemistry provided by LANL collaborators. This chemical separation was intended to remove the Pu from solution with little to no effect on the remaining elements. The chemistry was assessed to try to determine possible routes of fractionation of the sample and the fission products. The separation process used was successful for the bulk of the analyzed fission and activation products, as well as the added radiotracers. The final dissolved solution and separated fractions were analyzed by GEA looking at the remaining fission, activation and radiotracers and thermal ionization mass spectrometry analysis looking at the Pu isotopics.

14MeV↗
DOE OSTI2022

R-Value Measurements Performed on Actinide Targets Irradiated using the GODIVA IV Critical Assembly in FY22

The separation and characterization of two irradiated uranium targets, a depleted uranium (DU) and a highly enriched uranium (HEU) target as well as a plutonium (Pu) target, was conducted in April of 2022. The three targets were assembled at Los Alamos National Laboratory (LANL) and irradiated using the GODIVA critical assembly at the National Criticality Experiments Research Center (NCERC). Splits of the dissolved targets were received by Pacific Northwest National Laboratory (PNNL) after which the PNNL and LANL teams chemically separated the solutions using independent separation schemes and analyzed the separated fractions for short lived actinides and fission products. Chemical separations were traced with stable or radioactive tracers to allow for the determination of chemical yields, analyzing using either inductively coupled plasma optical emission spectroscopy (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS) or gamma emission analysis (GEA) depending on the nature of the tracer. The Pu target solution was traced with stable elements at LANL to follow elemental fractionation during a Pu removal step. Many analytical techniques were used by PNNL including kinetic phosphorescence analysis (KPA), ICP-OES, ICP-MS, GEA, and thermal ionization mass spectrometry (TIMS) depending on the analyte’s need.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS2007

Thermoelectric Devices Advance Thermal Management

Thermoelectric (TE) devices heat, cool, and generate electricity when a temperature differential is provided between the two module faces. In cooperation with NASA, Chico, California-based United States Thermoelectric Consortium Inc. (USTC) built a gas emissions analyzer (GEA) for combustion research. The GEA precipitated hydrocarbon particles, preventing contamination that would hinder precise rocket fuel analysis. The USTC research and design team uses patent-pending dimple, pin-fin, microchannel and microjet structures to develop and design heat dissipation devices on the mini-scale level, which not only guarantee high performance of products, but also scale device size from 1 centimeter to 10 centimeters. USTC continues to integrate the benefits of TE devices in its current line of thermal management solutions and has found the accessibility of NASA technical research to be a valuable, sustainable resource that has continued to positively influence its product design and manufacturing

Source record↗
NASA NTRS2026

Hybrid Thermally Efficient Core (HyTEC) Phase 1 3-Stage Compressor Rig Final Report - Unlimited Rights

The HyTEC Phase 1 3-Stage Compressor Rig project was conducted to mature and validate front-stage aerodynamic technologies in support of HyTEC Phase 2 and GEA’s Compact Core compressor. Building on the prior ERA Phase 2 Baseline Rig, GEA and NASA collaborated on the design and testing of the HyTEC rig, incorporating advanced technologies such as increased radius ratio, higher aerodynamic loading, and advanced casing treatment. The HyTEC test campaign leveraged similar design and instrumentation philosophy, test execution approach, and the same facility (NASA W-7) to enable clear comparison with the legacy ERA rig results. The HyTEC rig was designed to deliver benefits in efficiency, tip loading, operability, and aeromechanics, with success measured against defined TPMs that were anchored to the ERA baseline rig data.

Axial Compressors↗
DOE OSTI2020

A Scalable Method for Thickness and Lateral Engineering of 2D Materials

The physical properties of two-dimensional (2D) materials depend strongly on the number of layers. Hence, methods for controlling their thickness with atomic layer precision are highly desirable, yet still too rare, and demonstrated for only a limited number of 2D materials. Here we present a simple and scalable method for the continuous layer-by-layer thinning that works for a large class of 2D materials, notably layered germanium pnictides and chalcogenides. It is based on a simple oxidation/etching process, which selectively occurs on the topmost layers. Through a combination of atomic force microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and X-ray diffraction experiments we demonstrate the thinning method on germanium arsenide (GeAs), germanium sulfide (GeS) and germanium disulfide (GeS 2 ). We use first-principles simulation to provide insights into the oxidation mechanism. Our strategy, which could be applied to other classes of 2D materials upon proper choice of the oxidation/etching reagent, could pave the way for the realization of 2D material-based devices, such as electronic or optoelectronic ones, where a precise control over the number of layers (hence over the material’s physical properties) is needed. We also show that when used in combination with lithography, our method can be used to make precise patterns in the 2D materials.

2D materials↗
DOE OSTI2021

Chapter 2: Global Value Chain and Manufacturing Analysis on Geothermal Power Plant Turbines

The global geothermal power market has shown significant growth since the last decade and is expected to reach a total installed capacity of 18.4 gigawatts electric (GWe) by the end of 2021 (GEA, 2016). The global geothermal power plant turbine market is dominated by a small number of manufacturers. Between 2005 and 2015, 82% of the geothermal steam turbines were manufactured in Japan, and 74% of the geothermal binary cycle turboexpanders were manufactured in Israel. During this period, the United States played an important role in the global trade flow of fully assembled turbine units and turbine parts, with a high volume of imports and exports. Another significant growth area was in Italian turbine/turboexpander manufacturers, who have increased their market share in the last couple of years. One other important change in the manufacturing market was in Turkey, where the bonus on feed-in-tariff (FIT) for domestic hardware components boosted the national manufacturing sector between 2010 and 2020. When planning geothermal power projects, developers customize their power plant size to fit the available geothermal resource capacity. The turbine is designed and sized to optimize the efficiency and utilization of resource and revenue production. The rest of the power plant components such as heat exchangers (HX), water-cooled cooling towers (WCCT), or air-cooled condensers (ACC) are then chosen to complement the turbine size and design. These one-off manufacturing custom design turbines have relatively higher manufacturing set-up costs, longer lead times, and higher capital costs than the standard design turbines manufactured in larger volumes. However, turbines produced in standard increments and in larger manufacturing volumes could result in lower costs per turbine, but potentially lower efficiency. Based on pipeline projects and resource assessments, there is significant potential value in creating standard turbine sizes that could offer an economic advantage, as is done for modular microturbines.

40 EE - Geothermal Technologies Office (EE-4G)↗