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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Rapid and efficient hydrogen clathrate hydrate formation in confined nanospace

Clathrate hydrates are crystalline solids characterized by their ability to accommodate large quantities of guest molecules. Although CH 4 and CO 2 are the traditional guests found in natural systems, incorporating smaller molecules (e.g., H 2 ) is challenging due to the need to apply higher pressures to stabilize the hydrogen-bonded network. Another critical limitation of hydrates is the slow nucleation and growth kinetics. Here, we show that specially designed activated carbon materials can surpass these obstacles by acting as nanoreactors promoting the nucleation and growth of H 2 hydrates. The confinement effects in the inner cavities promote the massive growth of hydrogen hydrates at moderate temperatures, using pure water, with extremely fast kinetics and much lower pressures than the bulk system.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Grazing-incidence diffraction reveals cellulose and pectin organization in hydrated plant primary cell wall

Abstract The primary cell wall is highly hydrated in its native state, yet many structural studies have been conducted on dried samples. Here, we use grazing-incidence wide-angle X-ray scattering (GIWAXS) with a humidity chamber, which enhances scattering and the signal-to-noise ratio while keeping outer onion epidermal peels hydrated, to examine cell wall properties. GIWAXS of hydrated and dried onion reveals that the cellulose ( $$110/1\overline{1}0$$ 110 / 1 1 ¯ 0 ) lattice spacing decreases slightly upon drying, while the (200) lattice parameters are unchanged. Additionally, the ( $$110/1\overline{1}0$$ 110 / 1 1 ¯ 0 ) diffraction intensity increases relative to (200). Density functional theory models of hydrated and dry cellulose microfibrils corroborate changes in crystalline properties upon drying. GIWAXS also reveals a peak that we attribute to pectin chain aggregation. We speculate that dehydration perturbs the hydrogen bonding network within cellulose crystals and collapses the pectin network without affecting the lateral distribution of pectin chain aggregates.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Implications of high-pressure oxygen hydrates on radiolytic oxygen in Jovian icy moons

Various icy moons, such as Europa and Ganymede, have thin oxygen atmospheres and exhibit spectral features attributed to oxygen held in their surface ices. The oxygen forms from the radiolysis of water. The interiors of these bodies are subject to high pressures and it is not known how deep into icy moons oxygen-bearing ices can penetrate, or the structures formed by the oxygen–water system at high pressure. Here, we show that oxygen hydrates are stable to 2.6 GPa, allowing them to penetrate deep into icy moons, both above and below proposed sub-surface liquid-water oceans. Similarities between oxygen and hydrogen hydrates indicate potentially enhanced recombination rates, transforming them back into water and offering a resolution to the discrepancy between predicted and measured radiolysis rates. In addition to the low-pressure CS-II clathrate, our results find three high-pressure phases in the oxygen–water system: an ST clathrate, a C 0 hydrate, and a filled ice isomorphous with methane hydrate III. This shows a vast storage potential for molecular oxygen in icy moons and indicates that Europa could still be absorbing oxygen into its crustal ice.

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

Interfacial solvation and slow transport of hydrated excess protons in non-ionic reverse micelles

This work employs molecular dynamics simulations to investigate the solvation and transport properties of hydrated excess protons (with a hydronium-like core structure) in non-ionic Igepal CO-520 reverse micelles of various sizes in a non-polar solvent. Multiscale Reactive Molecular Dynamics (MS-RMD) simulations were used to describe vehicular and hopping diffusion during the proton transport process. As detailed herein, an excess proton shows a marked tendency to localize in the interfacial region of micellar water pools. Slow proton transport was observed which becomes faster with increasing micellar size. Further analysis reveals that the slow diffusion of an excess proton is a combined result of slow water diffusion and the low proton hopping rate. This study also confirms that a low proton hopping rate in reverse micelles stems from the interfacial solvation of hydrated excess protons and the immobilization of interfacial water. The low water density in the interfacial region makes it difficult to form a complete hydrogen bond network near the hydrated excess proton, and therefore locks in the orientation of hydrated proton cations. The immobilization of the interfacial water also slows the relaxation of the overall hydrogen bond network.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

The shard test and nanoporomechanics reverse classical paradigm of cement hydration being contractive

Le Chatelier in 1887 and Powers in 1947 demonstrated that the volume of nanoscale C-S-H (calcium silicate hydrate) particles formed during hydration is smaller than the combined volume of the reactants—the anhydrous Portland cement and water. Hydration has thus been considered as contractive. An experiment shows that the opposite is true above the nanoscale. The porous skeleton of cement paste expands as the growing C-S-H particles push each other apart, similar to crystal growth pressure. This is significant for high-performance concretes (HPC) with low water-cement ratios (w/c ≤ 0.4), where chemical self-desiccation lowers pore relative humidity by 40%, compared to just 1% in traditional concretes (w/c ≈ 0.5). Standard American Society for Testing and Materials (ASTM) C1608 tests, using 10 mm thick water-immersed specimens, show large shrinkage because the half-time of water ingress is many decades, unable to offset shrinkage-causing self-desiccation. The present experiment, using a laser microscopy-topography technique, proves the opposite—expansion, evidenced by measuring the length changes of water-immersed HPC shards 0.5 mm thick in which the diffusion halftime, only about one hour, allows continuous resaturation of pores, canceling self-desiccation. The faster diffusion (halftime of one hour) enables continuous pore resaturation, preventing shrinkage. When sealed with paraffin oil, the shards self-desiccate and shrink. These findings align with studies since 2015, showing that models excluding hydration expansion cannot fit test data across various specimen sizes and sealing conditions. The results suggest that standardized ASTM tests for the so-called chemical shrinkage in modern concretes with very low water-cement ratios are misleading and need revision.

Science & Technology - Other Topics↗
DOE OSTI2021

Characterization of Oil Well Cement Performance during Early Hydration under Simulated Borehole Conditions

Summary Experiments on oil well cement (OWC) slurries were performed using the newly developed laboratory-scale wellbore simulation chamber (WSC). The WSC can simulate hydrostatic pressure reduction in the cemented annulus and possible gas migration under representative conditions. Forensic analysis shows that pressurized fluids can result in porous cement and gas channeling during cement slurry gelation. The effects of different factors on slurry pore pressure were also studied, including formation permeability, initial overburden pressure (OBP) representing the depth of interest, wellbore temperature, water/cement (w/c) ratio, cement composition, and the use of a calcium chloride (CaCl2)-based accelerator. By analyzing the temperature history of hydrating cement using degree of hydration, the evolution of cement hydration was characterized for slurry designs cured at different hydration rates. This provides the opportunity to parameterize the slurry designs and other important factors associated with wellbore conditions.

Engineering↗
DOE OSTI2023

Methods and systems for redox flow battery electrolyte hydration

Methods and systems are provided for transporting and hydrating a redox flow battery system with a portable field hydration system. In one example, the redox flow battery system may be hydrated with the portable field hydration system in a dry state, in the absence of liquids. In this way, a redox flow battery system may be assembled and transported from a battery manufacturing facility to an end-use location off-site while the redox flow battery system is in the dry state, thereby reducing shipping costs, design complexities, as well as logistical and environmental concerns.

Song, Yang↗
DOE OSTI2021

Effect of temperature curing on properties and hydration of wollastonite blended magnesium potassium phosphate cements

K-struvite, the main hydrate of magnesium potassium phosphate (MKP) cements, dehydrates at ~50 °C, thus elevated temperatures at service conditions could affect cement properties and durability. In this study, properties and hydration of MKP cement without and with wollastonite were investigated at 20 and 50 °C. In hydrated pure MKP cement K-struvite decomposes progressively over time to MgKPO{sub 4}·H{sub 2}O at 50 °C, which leads to a strong reduction of solid volume and severe strength loss. The presence of wollastonite significantly slows down the decomposition rate of K-struvite, which is still observed after 393 days at 50 °C. K-struvite together with amorphous hydroxyapatite, M-(C)-S-H and CaK{sub 3}H(PO{sub 4}){sub 2} from the wollastonite reaction result in a cement with good short and long-term strength at both 20 and 50 °C.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Particle Size Optimization of Thermochemical Salt Hydrates for High Energy Density Thermal Storage

Thermal energy storage (TES) solutions offer opportunities to reduce energy consumption, greenhouse gas emissions, and cost. Specifically, they can help reduce the peak load and address the intermittency of renewable energy sources by time shifting the load, which are critical toward zero energy buildings. Thermochemical materials (TCMs) as a class of TES undergo a solid–gas reversible chemical reaction with water vapor to store and release energy with high storage capacities (600 kWh m −3 ) and negligible self‐discharge that makes them uniquely suited as compact, stand‐alone units for daily or seasonal storage. However, TCMs suffer from instabilities at the material (salt particles) and reactor level (packed beds of salt), resulting in poor multi‐cycle efficiency and high‐levelized cost of storage. In this study, a model is developed to predict the pulverization limit or R crit of various salt hydrates during thermal cycling. This is critical as it provides design rules to make mechanically stable TCM composites as well as enables the use of more energy‐efficient manufacturing process (solid‐state mixing) to make the composites. The model is experimentally validated on multiple TCM salt hydrates with different water content, and effect of R crit on hydration and dehydration kinetics is also investigated.

25 ENERGY STORAGE↗
DOE OSTI2021

Force field for calcium sulfate minerals to predict structural, hydration, and interfacial properties

Calcium sulfates such as anhydrite, hemihydrate, and gypsum find widespread use in building materials, implants, and tissue healing. We introduce a simple and compatible atomistic force field for all calcium sulfate phases that reproduces a wide range of experimental data including lattice parameters, surface, hydration, mechanical, and thermal properties in 1% to 5% accuracy relative to experiments. The performance is several times better than prior force fields and DFT methods, which lead to errors in structures and energies up to 100%. We explain (hkl) cleavage energies, the dynamics of (hkl) water interfaces, and new insights into molecular origins of crystal-facet specific hydration and solubility. Impressive agreement of computed and experimentally measured hydration energies is shown. The models add to the Interface force field (IFF) and are compatible with multiple force fields (CHARMM, AMBER, GROMOS, CVFF, PCFF, OPLS-AA) for property predictions of sulfate-containing materials from atoms to the large nanometer scale.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Inhibition mechanisms of steel slag on the early-age hydration of cement

Steel slag inhibits the early-age hydration of cement. However, its mechanism is still unclear. In this paper, the early-age hydration kinetics and the evolution of the solid phases, aqueous species and microstructures in a cement-steel slag composite binder are investigated to explore how steel slag inhibits the early-age hydration of cement. Two novel phenomena are found: (1) steel slag slows the depletion of gypsum and reduces the formation of ettringite, and (2) steel slag significantly inhibits the precipitation of CH and CSH. The results show that the addition of steel slag increases the Ca concentration in the pore solution, reduces the supersaturation of the pore solution with respect to CH and inhibits the nucleation and growth of CSH. Based on the above results, the retardation mechanisms of steel slag on the initial setting of cement paste are explained.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Effect of polycarboxylate ether on the expansion of ye'elimite hydration in the presence of anhydrite

Polycarboxylate ether (PCE), a commonly used superplasticizer, is known to influence the morphology of ettringite during the early hydration of C{sub 3}A- and ye'elimite-containing cements. According to existing theories, such morphological changes may be crucial to the expansive behavior of these cements. This paper studied the expansion of ye'elimite-anhydrite pastes and found the use of PCE to reduce expansion after 4 days of curing. Hydration studies were conducted by calorimetry, X-ray diffractometry, scanning electron microscopy, mercury intrusion porosimetry, inductively coupled plasma–optical emission spectrometry, and X-ray microtomography. The results show that the influences of PCE on the morphology of ettringite and the hydration of ye'elimite were quite small after 2 days. Based on the crystal growth theory, the range of pores in which ettringite can grow was calculated to explain the observed expansive behaviors. The presence of ettringite nano-crystals in aluminum hydroxide was also revealed and considered as a possible expansion mechanism.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Electromagnetic wave absorption of multifunctional cementitious composites incorporating polyvinyl alcohol (PVA) fibers and fly ash: Effects of microstructure and hydration

Highlights: • The cementitious composite shows excellent wide-band electromagnetic wave absorption in a frequency range of 2–18 GHz. • The PVA fibers and the fly ash change the dielectric properties of the cementitious composite by Debye polarization. • The iron oxide of the cementitious binders contributes to the magnetic properties of the composites. • The impacts of the microstructure and the hydration of the cementitious composite on its microwave absorption are analyzed. This paper devises a novel method for the adjustment of the pore structure and the hydration of cement to improve the electromagnetic wave absorption of the cementitious composites incorporating polyvinyl alcohol (PVA) fibers and fly ash in a frequency range of 2–18 GHz. The underlying mechanism of the absorption is investigated to explore the possibility of the structural and functional integration of these composites. The electromagnetic parameters of the prepared cementitious composites and those of the raw materials are analyzed in a frequency range of 0.5–18 GHz. Moreover, the pore structure and the chemical environment of the cementitious composites are examined by mercury intrusion porosimetry (MIP), back-scattered electron detector (BSE), and X-ray photoelectron spectroscopy (XPS). The results indicate that the PVA fibers and the high-volume fly ash have a positive effect on electromagnetic wave absorption of the cementitious composites through the adjustment of their pore structure and hydration.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Effect of seawater as mixing water on the hydration behaviour of tricalcium aluminate

This study explored the mechanism of the effect of seawater on tricalcium aluminate (C{sub 3}A) hydration. The results showed that seawater retarded C{sub 3}A hydration and reduced the reaction degree of C{sub 3}A. The co-existence or ion pairing of Ca{sup 2+} and SO{sub 4}{sup 2−} onto the surface of C{sub 3}A poisoning the reactive sites is the main reason for this retardation. Besides, the precipitation of Mg(OH){sub 2} on the surface of C{sub 3}A would prolong the induction period for another 30 min and then consequently decrease the dissolution rate of C{sub 3}A hydration. Trace amounts of MgSO{sub 4}{sup 0} and Mg{sup 2+} present in the alkaline solution had little retardation effect. It was also found that Cl{sup −} would preferentially react with C{sub 3}A to form Friedel's salt, rather than forming hydroxy-AFm as that in the C{sub 3}A-deionized water paste. The direct formation of Friedel's salt resulted in an accumulation of Al{sup 3+} in solution, which would also hinder the subsequent dissolution of C{sub 3}A.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Continuous optical in-situ pH monitoring during early hydration of cementitious materials

A luminescent sensor technique for pH analyses has been tested in cementitious media. The optical sensors monitor in-situ pH every 5 s during early hydration reactions over a period of 100 h from initial fluid up to consolidated stage. The pH development was analysed in calcium aluminate, calcium sulfoaluminate and OPC/slag cements up to a pH level of 13.3 and directly correlated with the heat of hydration. Thus tracing the dissolution and formation processes of solid phases via pH sensor monitoring is possible. This measurement technique enables the recording of continuous and highly reproducible pH data sets from slurries, pastes, and hardening materials leading to new vistas for individual (trans)formation pathways of solids, hydration and consolidation reactions in high alkaline cementitious systems.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Nanostructural evolution of Al(OH)3 gel formed by the cubic and orthorhombic ye'elimite clinkers of calcium sulfoaluminate cements in an ultra-wide hydration temperature range

This paper investigated the influence of hydration temperature on the nanostructure of the AH{sub 3} phase formed in calcium sulfoaluminate cements. Orthorhombic ye'elimite (st-ye'elimite) and cubic ye'elimite (ss-ye'elimite) were hydrated in an ultra-wide temperature range (5–220 °C). Results showed that the AH{sub 3} phase formed by ss-ye'elimite was always microcrystalline in nature at various curing temperatures (5–130 °C), and transformed into the AlOOH phase at 150 °C and above. However, the AH{sub 3} phase formed by st-ye'elimite grew from a microcrystal to a favorable crystal as the temperature increased, and transformed into the AlOOH phase at 170 °C and above. The nanostructure of hydration products was further investigated using TEM/SAED analysis together with FE-SEM images, directly evidencing that the formed AFm-12 phase was single-crystal in nature, and the formed AH{sub 3} phase was microcrystalline at low temperatures and grew into single-crystal hexagonal prisms with the preferred growth direction along [001] direction at high temperatures.

36 MATERIALS SCIENCE↗
DOE OSTI2022

A step-wise ion hydration model of aqueous electrolyte solution: The 2:2, 2:1 and 1:2 punches

In prior work we showed that the current step-wise hydration framework shows promise for modeling the concentration-activity relationship in aqueous solutions of ions representing 1:1 electrolytes, alcohols, and sugars, and accurately predicting the partitioning of the water between the bound (hydrated) pool and an unbound (free) pool. Here, in the current work, we continue developing this framework by applying it to ions representing 2:2, 2:1 and 1:2 electrolyte in aqueous solutions. Properly treating ion hydration as an ideal solution along with employing mean spherical approximation of the long-range electrostatic interactions yields an accurate model for most electrolytes considered. This simple model of aqueous solutions is robust for electrolytes and organic solutes.

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

Unexpected Hydroxide Ion Structure and Properties at Low Hydration

Understanding the behavior of hydroxide ions in aqueous and non-aqueous media is fundamental to many chemical, biological, and electrochemical processes. Research has primarily focused on a single fully solvated hydroxide ion, either as an isolated cluster or in bulk. This work presents the first computational study to consider hydroxide under low hydration levels in detail, where the anion may not be fully solvated. Under such conditions, we find that the anions are predominantly present as unique water-bridged hydroxide pair complexes, distinct from previously reported structures under fully hydrated conditions. Although similar hydroxide pair structures were previously reported, we analyze these structures for the first time in the disordered liquid state where they are found to be unusually stable in the presence of bulky quaternary ammonium cations. Our findings help explain the unusual diffusion behavior as well as the higher reactivity of hydroxide anions observed under low hydration conditions.

computational studies↗