Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “mechanical stability”

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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

A capillary-based microfluidic device enables primary high-throughput room-temperature crystallographic screening

A novel capillary-based microfluidic strategy to accelerate the process of small-molecule-compound screening by room-temperature X-ray crystallography using protein crystals is reported. The ultra-thin microfluidic devices are composed of a UV-curable polymer, patterned by cleanroom photolithography, and have nine capillary channels per chip. The chip was designed for ease of sample manipulation, sample stability and minimal X-ray background. 3D-printed frames and cassettes conforming to SBS standards are used to house the capillary chips, providing additional mechanical stability and compatibility with automated liquid- and sample-handling robotics. These devices enable an innovative in situ crystal-soaking screening workflow, akin to high-throughput compound screening, such that quantitative electron density maps sufficient to determine weak binding events are efficiently obtained. This work paves the way for adopting a room-temperature microfluidics-based sample delivery method at synchrotron sources to facilitate high-throughput protein-crystallography-based screening of compounds at high concentration with the aim of discovering novel binding events in an automated manner.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Strain dependent electronic and optical responses of penta-BCN monolayer

We report here, structural, dynamic, and mechanical stability in pentagonal boron carbon nitride (p-BCN) monolayer, a new member of direct bandgap two-dimensional (2D) semiconductor. The identified visible range bandgap with excellent mechanical strength allows it to be a promising candidate material in optoelectronics, nanomechanics, and optomechanical sensors. By employing density functional theory (DFT), we reveal a unique geometrical reconstruction with rigidity in B–N and C–N bond lengths with applied strain. These quasi-sp 3 hybridized short and strong covalent bonding and unique geometry support the monolayer to possess extraordinary mechanical response. The desired bandgap is manipulated by loading the biaxial strain. Most importantly, our predictions on p-BCN show excellent optical response such as good static dielectric constant and refractive index, strong optical absorption (up to 1.08 x 10 5 cm -1 in VR and 7.01 x 10 cm -1 in UV) with small energy loss and reflectance both appearing in visible and ultraviolet regions (UV). The desired optical response along with the blue and red shift is demonstrated by tailoring with tensile and compressive strain. The predicted strong optical anisotropy provides it’s application in polarized photodetection.

36 MATERIALS SCIENCE↗
DOE OSTI2023

A prediction of the thermodynamic, thermophysical, and mechanical properties of CrTaO 4 from first principles

It is reported that the self-forming CrTaO 4 oxide scale can protect refractory high-entropy alloys from oxidation, superior to Cr 2 O 3 . In this paper, the phase stability, mechanical, and thermal properties of three polymorphous phases of CrTaO 4 are systematically investigated from first-principles density functional theory calculations. The mechanical properties predicted using the strain–energy methods indicated that all three phases are mechanically stable. The temperature dependence of elastic constants and polycrystalline moduli of three phases demonstrated the thermal softening as temperature increase. The Helmholtz-free energies as a function of volume and temperature are derived from phonon dispersions within the quasi-harmonic approximation at six strained volumes. The calculated apparent bulk coefficients of thermal expansion of these three phases are evaluated, the highest value approximately 13.4× 10 –6 K –1 within a temperature range of 500–2000 K for the rutile I4 1 md phase. The lattice thermal conductivity calculated by the Debye–Callaway model suggested that the rutile type I4 1 md phase has the lowest value of approximately 2.1 W/m/K at 1800 K. The other two phases, C2/m and P2/c, exhibit higher values due to relatively lower Grüneisen parameters and larger phonon velocities. The melting point of CrTaO 4 is predicted to be between 1975 and 2449 K using ab initio molecular dynamics simulations. Finally, this work provides a comprehensive theoretical understanding of the thermodynamic, mechanical, and thermal properties for the new material CrTaO 4 and serves as an example of a viable computational design strategy for improved oxidation resistance of refractory alloys at high temperatures.

36 MATERIALS SCIENCE↗
NASA NTRS1971

Improved reflective coating for integrating spheres

Inorganic salts or oxide material is transparent in single-crystal form, has high refractive index, smooth cleavage, and chemical stability, is stable to radiations of interest, partially soluble and easily dispersed in liquid for spraying, and readily dried /cured/ with reasonable cohesion and adhesion, and has good mechanical stability.

Stuart, J. W.↗
DOE OSTI2020

The genetic architecture of biomechanical traits in sorghum

Sorghum bicolor (L.) Moench is the fifth most commonly grown cereal crop worldwide with unrivaled drought tolerance compared with other cereal crops. Drought and heat tolerance and high biomass yield potential make sorghum a promising bioenergy crop. However, stem lodging is a significant problem that results in substantial yield losses. Stem biomechanical traits influence the mechanical stability of crops and breeding for desirable biomechanical traits may result in improved lodging resistance. In this study, we report the identification of quantitative trait loci (QTL) for stem mechanical and morphological traits in three recombinant inbred line (RIL; populations from Tx623/Rio, Tx623/Della, and Tx631/Della) crosses between elite grain and sweet sorghum parents. The genetic architecture of stem biomechanical traits in the three RIL populations is multigenic and pleiotropic. Additionally, eight QTL affecting mechanical and morphological traits were detected; two main effects of these QTL were consistently found in all populations and colocated with previously identified dwarfing genes Dw1 and Dw3. These results indicate that dwarfing genes affect the mechanical properties of sorghum stems and their lodging resistance, while also having demonstrable effects on stem morphology. The identification of these QTL provides new opportunities for improving stem lodging resistance via genomics-assisted breeding.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2026

Computational simulation of asymmetric phase transformation in cracked Li₇La₃Zr₂O₁₂: Variant selection and chemo-mechanical implications

Coupling between microcracks and phase transformation in ion-conducting ceramics can jointly affect mechanical responses and ion transport. In this work we investigate the cubic-to-tetragonal phase transformation in Li₇La₃Zr₂O₁₂ in the presence of a microcrack under hydrostatic loading and quantify its implications for crack-tip stress concentration and Li-ion transport using phase-field and molecular dynamics simulations. The phase transformation exhibits a strong asymmetry between hydrostatic tension and compression. Under tension, the crack edge nucleates one tetragonal variant that amplifies the crack-tip stress intensity and promotes crack opening. Under compression, the crack tip nucleates a different tetragonal variant that enhances the stress-induced crack-closure tendency. Effective Li diffusivity analysis shows faster transport degradation under compression due to accelerated transformation kinetics, exposing a trade-off between mechanical stability and ionic conductivity. These results highlight the intertwined nature of cracking, phase transformation, and ionic transport in ion-conducting oxides and provide mechanistic insights into chemo-mechanical degradation of solid electrolytes.

36 MATERIALS SCIENCE↗
DOE OSTI2025

In-situ polymerized and crosslinked electrolytes with interchangeable Li/Na transport for battery applications

The next generation of batteries requires electrolytes with high conductivity, mechanical stability, good adhesion with electrodes, wide electrochemical windows, and scalability. The present study introduces a concept of doped quasi single-ion conducting copolymers based on methacrylate-(trifluoromethanesulfonyl)imide (TFSI) and vinyl ethylene carbonate which at room temperature are mechanically robust and display ionic conductivities of ~0.1 mS/cm. These electrolytes can be polymerized/crosslinked in-situ, making them easily implementable in current battery manufacturing technologies. They also allow for switching between Li + and Na + transport using simple chemistry procedures. To demonstrate their potential for battery applications, the newly developed Li conductors have been tested in symmetric cells, exhibiting overall impedance below 350 Ohm and plating/stripping stability up to 1 mA/cm 2 . Moreover, lithium metal batteries incorporating this electrolyte and high-voltage Lithium Nickel Manganese Cobalt Oxide (NMC) cathodes show good capacity retention (~79%) during charging and discharging for 80 cycles at C/10 rate and a Coulombic efficiency close to 100% in the entire measurement range. The compositional, mechanical and electrochemical versatility of these electrolytes opens new venues for the design of polymer-based batteries capable of fast charging and extended cycle life, aligning with the current global green energy storage strategies.

Polymer electrolytes↗
DOE OSTI2021

Stable, Ductile and Strong Ultrafine HT-9 Steels via Large Strain Machining

Beyond the current commercial materials, refining the grain size is among the proposed strategies to manufacture resilient materials for industrial applications demanding high resistance to severe environments. Here, large strain machining (LSM) was used to manufacture nanostructured HT-9 steel with enhanced thermal stability, mechanical properties, and ductility. Nanocrystalline HT-9 steels with different aspect rations are achieved. In-situ transmission electron microscopy annealing experiments demonstrated that the nanocrystalline grains have excellent thermal stability up to 700 °C with no additional elemental segregation on the grain boundaries other than the initial carbides, attributing the thermal stability of the LSM materials to the low dislocation densities and strains in the final microstructure. Nano-indentation and micro-tensile testing performed on the LSM material pre- and post-annealing demonstrated the possibility of tuning the material’s strength and ductility. The results expound on the possibility of manufacturing controlled nanocrystalline materials via a scalable and cost-effective method, albeit with additional fundamental understanding of the resultant morphology dependence on the LSM conditions.

36 MATERIALS SCIENCE↗
NASA NTRS1999

Haptic stabilization of posture: changes in arm proprioception and cutaneous feedback for different arm orientations

Postural sway during quiet stance is attenuated by actively maintained contact of the index finger with a stationary surface, even if the level of applied force (<1 N) cannot provide mechanical stabilization. In this situation, changes in force level at the fingertip lead changes in center of foot pressure by approximately 250 ms. These and related findings indicate that stimulation of the fingertip combined with proprioceptive information about the hand and arm can serve as an active sensor of body position relative to the point of contact. A geometric analysis of the relationship between hand and torso displacement during body sway led to the prediction that arm and hand proprioceptive and finger somatosensory information about body sway would be maximized with finger contact in the plane of body sway. Therefore, the most postural stabilization should be possible with such contact. To test this analysis, subjects touched a laterally versus anteriorly placed surface while in each of two stances: the heel-to-toe tandem Romberg stance that reduces medial-lateral stability and the heel-to-heel, toes-outward, knees-bent, "duck stance" that reduces fore-aft stability. Postural sway was always least with finger contact in the unstable plane: for the tandem stance, lateral fingertip contact was significantly more effective than frontal contact, and, for the duck stance, frontal contact was more effective than lateral fingertip contact. Force changes at the fingertip led changes in center of pressure of the feet by approximately 250 ms for both fingertip contact locations for both test stances. These results support the geometric analysis, which showed that 1) arm joint angles change by the largest amount when fingertip contact is maintained in the plane of greatest sway, and 2) the somatosensory cues at the fingertip provide both direction and amplitude information about sway when the finger is contacting a surface in the unstable plane.

Non-NASA Center↗
DOE OSTI2021

Fabrication of New PCM Hydrogel Composites

Salt hydrates are low-cost phase-change materials (PCMs) with excellent thermal energy storage capacities. However, they are limited by low thermal cycling stability due to incongruent melting-induced phase separation. This project will solve the long-standing issue of phase separation of salt hydrates by stabilizing salt particles in a charged polymer hydrogel network. The proposed approach uses combined physical and chemical stabilization mechanisms achieved by selecting a proper chemistry and molecular weight of the polymer matrix. In summary, we have identified several important formulations that show good energy storage capacity performance and good cycling stability. The thermal storage capacity can be further improved through further sample optimization. The thermal conductivities of the samples were low, but there are ways to improve it by adding a highly thermally conductive material with a high aspect ratio. The method of preparation is suitable for scale-up.

25 ENERGY STORAGE↗
NASA NTRSDate not supplied

Understanding Thermal Stability in Zirconia-Based Aerogels

For lightweight, thermal insulation needs above 1000ºC, the high surface to volume ratios of ceramic-based aerogels are practically unparalleled. Yet realizing the full potential of aerogel-based thermal protection systems requires not only increased thermal stability, but also a broadened menu of stabilizing mechanisms. Here we will review our recent efforts to understand the impact of synthetic parameters and dopant chemistry on the evolution of zirconia-based ceramics. A broad parametric window for thermal stability is established, in which the more sensitive variable of composition has been probed. However, dopant chemistry is actually an aggregate for many closely related material parameters including surface energy, enthalpy of formation, each of which may contribute uniquely to aerogel destabilization. A truly predictive design framework for ceramic-based aerogels requires further decoupling of these underlying properties through systematic and comprehensive evaluation of thermodynamic properties.

aerogel↗
DOE OSTI2025

Ether Cleavage Decreases the Ion Exchange Capacity of Anion Exchange Membranes

Anion exchange membranes (AEMs) are integral to fuel cells and water electrolysis systems but suffer from poor durability under alkaline conditions. Ether cleavage is an important failure pathway of poly(arylene ether)-based AEMs that compromises both mechanical stability and ion transport. While this degradation pathway is often studied in terms of polymer fragmentation, the role of newly formed hydrophilic groups has been largely overlooked. Here, we show that polymer scission leads to reduced mechanical rigidity, while the introduction of hydrophilic groups partially mitigates this loss. Under alkaline conditions, phenoxide groups formed during ether cleavage neutralize the polymer cations, leading to a previously unreported loss of ion exchange capacity (IEC). This IEC loss mechanism exacerbates the reduction in ionic conductivity, emphasizing the severity of ether cleavage as a degradation pathway. Recognizing that ether cleavage introduces significant chemical changes beyond polymer fragmentation provides critical insights into its interplay with other degradation mechanisms, such as the direct reduction of cationic sites by E2 and S N 2, and provides molecular-level interpretations for the concurrent effects of polymer scission and increased hydrophilicity on membrane performance.

crystal cleavage↗
DOE OSTI2023

Preparation of Macroscopic Low-Density Gold Foams with Good Machinability

Uniform, macroscopic monoliths (ranging from a few millimeters to a centimeter) of low-density gold foams with ~95% porosity and ~10-μm-diameter pores were prepared by the casting of gold-coated polystyrene core-shell particles followed by the thermal removal of the polymer core. The Au foams were composed of unique hollow gold spheres and showed superior mechanical integrity and resilience compared to the foams we previously reported. Highly efficient seeding and electroless gold-plating methods in this study caused a significant morphological transition in the gold coatings from coarse particles to fine particles, and finally, to a continuous layer. A modified, scalable casting approach to form large uniform monoliths (up to ~1-cm diameter) and a gentle baking condition to minimize undesirable densification of the final foams enabled us to develop a simple, efficient synthetic route to nanostructured macroscopic low-density gold foams. To demonstrate the improved mechanical stability and machinability, a representative monolithic Au foam (~0.9 g/cm 3 ) was carefully cut into the hollow cylinder of gold foams by a series of machining and processing steps. Finally, we tried to understand the unique mechanical behaviors and properties of this gold foam by nanoindentation measurement.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2021

LUVOIR-ECLIPS Closed-Loop Adaptive Optics Performance and Contrast Predictions

One of the primary science goals of the Large UV/Optical/Infrared Surveyor (LUVOIR) mission concept is to detect and characterize Earth-like exoplanets orbiting nearby stars with direct imaging. The success of its coronagraph instrument ECLIPS (Extreme Coronagraph for Living Planetary Systems) depends on the ability to stabilize the wavefront from a large segmented mirror such that optical path differences are limited to tens of picometers RMS during an exposure time of a few hours. In order to relax the constraints on the mechanical stability, ECLIPS will be equipped with a wavefront sensing and control (WS\&C) architecture to correct wavefront errors up to temporal frequencies $\gtrsim$1 Hz. These errors may be dominated by spacecraft structural dynamics exciting vibrations at the segmented primary mirror. In this work, we present detailed simulations of the WS\&C system within the ECLIPS instrument and the resulting contrast performance. This study assumes wavefront aberrations based on a finite element model of a simulated telescope with spacecraft structural dynamics. Wavefront residuals are then computed according to a model of the adaptive optics system that includes numerical propagation to simulate a realistic wavefront sensor and an analytical model of the temporal performance. An end-to-end numerical propagation model of ECLIPS is then used to estimate the residual starlight intensity distribution at the science detector. We show that the contrast performance depends strongly on the target star magnitude and the spatio-temporal distribution of wavefront errors from the telescope. In cases with significant vibration, we advocate for the use of laser metrology to mitigate high temporal frequency wavefront errors and increase the mission yield.

Sirbu, Dan↗
NASA NTRS2004

A Superfluid Clock

The performance of clocks is limited by the characteristics of the underlying oscillator. Both the quality factor of the oscillator and the signal-to-noise ratio for the resonator state measurement are important. A superfluid helium Helmholtz resonator operating at approx.100mK temperatures has the potential of maintaining frequency stability of 5x10(exp -15)/t(exp 1/2) on the time scale of a few months. The high dynamic range of lossless SQUID position displacement measurement, and low losses associated with the superfluid flow, combined with high mechanical stability of cryogenic assemblies, contribute to the projected stability. Low overall mass of the assembly allows for multiple stages of vibration isolation.

Penanen, Konstantin↗
DOE OSTI2021

Investigations of the stability of etched or platinized p-InP(100) photocathodes for solar-driven hydrogen evolution in acidic or alkaline aqueous electrolytes

Here, the stability of p-InP photocathodes performing the hydrogen-evolution reaction (HER) has been evaluated in contact with either 1.0 M H 2 SO 4 (aq) or 1.0 M KOH(aq), with a focus on identifying corrosion mechanisms. Stability for the solar-driven HER was evaluated using p-InP electrodes that were either etched or coated with an electrodeposited Pt catalyst (p-InP/Pt). Variables such as trace O 2 were systematically controlled during the measurements. Changes in surface characteristics after exposure to electrochemical conditions as well as electrode dissolution processes were monitored using X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma mass spectrometry (ICP-MS). In either H 2 SO 4 or KOH, etched p-InP photoelectrodes corroded cathodically under illumination, forming metallic In 0 at the electrode surface. In contrast, electrodeposition of Pt kinetically stabilized illuminated p-InP photocathodes in both H 2 SO 4 and KOH by inhibiting the cathodic corrosion pathway. Notably, when held at 0 V vs. the reversible hydrogen electrode (RHE) in 1.0 M H 2 SO 4 (aq), p-InP/Pt exhibited a stable current density (J) of ~–18 mA cm –2 for >285 h under simulated 1 Sun illumination. The long-term current density vs. potential (J–E) behavior at pH 0 and pH 14 of p-InP/Pt photocathodes correlated with changes in the surface chemistry as well as the dissolution of p-InP. In acidic media, the J–E behavior of p-InP/Pt photocathodes remained nearly constant with time, but the surface of a p-InP/Pt electrodes gradually turned P-rich via a slow and continuous leaching of In ions. In alkaline electrolyte, the surface of p-InP/Pt electrodes was passivated by formation of an InO x layer that exhibited negligible dissolution but led to a substantial degradation in the J–E characteristics. Consequently, changes in the catalytic kinetics and surface stoichiometry are both important considerations for determining the corrosion chemistry and the long-term operational stability of InP photoelectrodes.

14 SOLAR ENERGY↗