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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Studies on the Encapsulation of Brine Generated from a Process Using Selective Electrodialysis Reversal

This topical report summarizes the laboratory testing, geochemical modeling, and mineralogical testing conducted to examine the efficacy of wastewater encapsulation for the brine generated from the Saltworks Flex electrodialysis reversal technology. Within the laboratory testing, the short- and long-term physical properties of seven separate mix designs were examined along with the leaching of each mix design. Additionally, geochemical thermodynamic modeling was used along with mineralogical analyses to help gain a fundamental understanding of the chemistry involved in the encapsulation process. Encapsulation is a process that results in the immobilization of constituents of interest by creating an engineered material that contains the waste within its matrix, both physically and chemically, in such a manner that the receiving environment is protected from adverse effects. Within the context of this study, encapsulation mix designs involved mixing the Saltworks brine with fly ash and various additives, principally lime (calcium oxide) and cement, to form a paste that eventually sets and hardens into a monolith upon placement in a landfill. Moisture conditioning fly ash with wastewater sources for on-site landfill disposal is a process that is in use at some sites and has been presented as a viable option to dispose of liquid wastes. However, because chemical reactions that can lead to sequestration of constituents of interest are not optimized, leaching can occur. Therefore, in this study, mixes were created to mimic moisture conditioning, as well as engineered pastes of varying mix designs. The study found that engineered encapsulation mixes provide significant resistance to leaching compared to moisture conditioning alone. The best performing encapsulation mix used lime as the additive, which proved superior to the use of cement. After 90 days of curing, this encapsulated mix was 5.5 times stronger than the moisture conditioned mix. Additionally, this mix exhibited an approximate 2.5 order of magnitude drop in hydraulic conductivity compared to the moisture conditioned mix. When comparing leaching, nearly all the chloride was found to evolve from the moisture conditioned mix, whereas only 6.7% of the chlorine contained in the best performing encapsulated mix leached out. Mineralogical analysis via X-ray diffraction (XRD) showed a significant concentration of the chloride sequestering mineral, Friedel’s salt, in the best performing encapsulation mix, whereas none was observed in the moisture conditioned mix, pointing to it being the primary chemical mechanism for chloride retention, along with the physical impermeability of the material. With respect to the modeling study, the model was successful in predicting the presence of most mineral phases observed in the XRD analysis.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2025

Molecular H 2 as the Reducing Agent in Low-Temperature Oxide Reduction Using Calcium Hydride

Low-temperature synthesis is crucial for advancing sustainable manufacturing and accessing novel metastable phases. Metal hydrides have shown great potential in facilitating the reduction of oxides at low temperatures, yet the underlying mechanism—whether driven by H - , H 2 , or atomic H—remains unclear. Here, in this study, we employ in situ electrical transport measurements and first- principles calculations to investigate the CaH 2 -driven reduction kinetics in epitaxial α-Fe 2 O 3 thin films. Intriguingly, samples in direct contact with or separated from CaH 2 powders exhibit similar apparent activation energies for H 2 reduction, although direct contact significantly increases the reduction rate. These findings indicate that molecular H 2 is the dominant reducing species in the low-temperature reduction of oxides using CaH 2 , with a key aspect of the hydrides' superior reducing power attributed to their ability to eliminate residual moisture. This work underscores the critical role of moisture control in enabling effective low-temperature oxide reduction for advanced material synthesis.

Wang, Jiayue [SLAC National Accelerator Laboratory↗
DOE OSTI2019

Cationic Effect of Ferrous Ions on Sulfide Capacity of CaO-Fe{sub t}O-Al{sub 2}O{sub 3}-SiO{sub 2} Slag System

The cationic effect of ferrous ions on the sulfide capacity of CaO-Fe{sub t}O-Al{sub 2}O{sub 3}-SiO{sub 2} slags was studied from the viewpoint of the ionic structure in the slag using micro-Raman spectroscopy. In the cation-excess region (M{sup 2+}/2(Fe{sup 3+} + Al{sup 3+}) > 1.0), the sulfide capacity was directly proportional to the basicity of the slags, owing to the S{sup 2−} stabilizing effect of excess cations. However, in the cation-deficient region (M{sup 2+}/2(Fe{sup 3+} + Al{sup 3+}) < 1.0), the sulfide capacity was independent of the basicity of the slags owing to the deficiency of cations required for charge compensation with Al{sup 3+} and Fe{sup 3+}. The cation-substitution effect on the sulfide capacity of the CaO-rich slags (Fe{sub t}O/(Fe{sub t}O + CaO < 0.5) exhibited a linear relationship with the Fe{sup 2+} content because Fe{sup 2+} had a stronger affinity with S{sup 2−} compared to that with Ca{sup 2+}. However, in the Fe{sub t}O-rich slags (Fe{sub t}O/(Fe{sub t}O + CaO > 0.5), the sulfide capacity decreased with the increase of the Fe{sup 2+} content owing to the Q{sup n} unit affinity of the Fe{sup 2+} ion. The sulfide capacity was determined by the competition between the Q{sup n} unit affinity and stability of the S{sup 2−} ion, depending on the type of cation. Therefore, the partial covalent bonding between the M{sup 2+} cations (M: Ca, Fe) and aluminosilicate affected the ionic interactions with the S{sup 2−} ions.

36 MATERIALS SCIENCE↗
NASA NTRS1979

Reactions of calcium orthosilicate and barium zirconate with oxides and sulfates of various elements

Calcium orthosilicate and barium zirconate were evaluated as the insulation layer of thermal barrier coatings for air cooled gas turbine components. Their reactions with various oxides and sulfates were studied at 1100 C and 1300 C for times ranging up to 400 and 200 hours, respectively. These oxides and sulfates represent potential impurities or additives in gas turbine fuels and in turbine combustion air, as well as elements of potential bond coat alloys. The phase compositions of the reaction products were determined by X-ray diffraction analysis. BaZrO3 and 2CaO-SiO2 both reacted with P2O5, V2O5, Cr2O3, Al2O3, and SiO2. In addition, 2CaO-SiO2 reacted with Na2O, BaO, MgO, and CoO and BaZrO3 reacted with Fe2O3.

Zaplatynsky, I.↗
DOE OSTI2019

Experimental Liquidus Study of the Ternary CaO-ZnO-SiO{sub 2} System

Phase equilibria of the ternary CaO-ZnO-SiO{sub 2} system have been investigated at 1170 °C to 1691 °C for oxide liquid in equilibrium with air and solid oxide phases: tridymite or cristobalite SiO{sub 2} (up to two immiscible liquids), pseudowollastonite (CS) CaSiO{sub 3}, rankinite (C{sub 3}S{sub 2}) Ca{sub 3}Si{sub 2}O{sub 7}, dicalcium silicate (C{sub 2}S) (Ca, Zn){sub 2}SiO{sub 4}, tricalcium silicate (C{sub 3}S) (Ca, Zn){sub 3}SiO{sub 5}, lime (Ca, Zn)O, zincite (Zn, Ca)O, willemite Zn{sub 2}SiO{sub 4} and hardystonite (melilite) Ca{sub 2}ZnSi{sub 2}O{sub 7}, covering the ranges of concentrations not studied before. High-temperature equilibration on primary phase (silica) or inert metal (platinum) substrates followed by quenching and direct measurement of the Ca, Zn and Si concentrations in the phases with the electron probe X-ray microanalysis (EPMA) has been used to accurately characterize the system. Liquidus phase equilibrium data of the present authors for the CaO-ZnO-SiO{sub 2} system are essential to obtain a self-consistent set of parameters of thermodynamic models for all phases.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Effect of additives on carbon dioxide uptake and compressive strength of dry-cast concrete

The main thrust of the work reported herein is to study the effect of chemical additives to make beneficial use of carbon dioxide in enhancing the compressive strength of dry-cast concrete. The additives used in this investigation were calcium and magnesium oxides and silicates, nickel oxide, sodium hydroxide, sodium bicarbonate and strontium chloride. The experimental results showed that both the carbonation reactions and the compressive strength of dry-cast concrete mixtures were improved when using chemical additives. Experimental investigations for optimisation were also undertaken with selected additives to further increase the carbon dioxide uptake and improve the compressive strength. The best results were obtained when using calcium silicate in combination with calcium oxide. The early-age compressive strength of specimens made from the optimised mixture increased from 9·82 MPa to 13·32 MPa, and the specimens’ carbon dioxide uptake increased from 8·76% to 10·62% of cement weight.

Construction & Building Technology↗
DOE OSTI2021

Synthesis, characterization, and thermodynamic study of selected K-based zeolites

Potassium-rich zeolites often occur in cementitious systems, as K{sup +} is widespread in various cementitious materials, such as Portland, blended and alkali-activated cements. The knowledge of their stability and of thermodynamic models for solid solutions with Na{sup +} and Ca{sup 2+} are critical to understand long-term development and durability in such cements. Completing previous studies on Na- and Ca-based zeolites, the current work aims to determine the thermodynamic data of 14 types of K-based zeolites, which could possibly form in cementitious systems. The zeolites were synthesized hydrothermally, exchanged with K{sup +}, and characterized thoroughly with respect to framework structures, elemental compositions, water contents, and bond variations. Their thermodynamic properties were derived from the experimental solubility data, which allowed establishing predominance diagrams in the K{sub 2}O-SiO{sub 2}-Al{sub 2}O{sub 3}-H{sub 2}O system. The K-based zeolites typically showed the lowest solubility between 0 and 100 °C, with the notable exception of Ca-gismondine and two Na-based zeolites: natrolite and Na-mordenite.

36 MATERIALS SCIENCE↗
NASA NTRS2003

MN Carbonates in the Martian Meteorite Nakhla: Possible Evidence of Brine Evaporation

The importance of secondary phases in martian meteorites lies in their potential to provide clues about the martian environments responsible for their formation. During this study, we analyzed a number of carbonate-bearing fracture surfaces from the Nakhla meteorite. Here we describe the physical and chemical properties of several manganese-calcium-rich siderites. Additionally, we describe a potential model for the formation and alteration of these carbonates, and we suggest constraints on the conditions responsible for their precipitation. Nakhla is an olivine-bearing clinopyroxenite with minor amounts of feldspar, FeS, and Fe oxides. Secondary mineral assemblages include vein filling clay with embedded iron oxides, a calcium sulfate, amorphous silica, chlorapatite, halite and carbonates. Bridges and Grady suggested that the carbonates in Nakhla formed from brine evaporation. Isotope studies of the Mn rich siderite are also consistent with formation from hydrothermal fluids with an upper T constraint of ~170 C.

Bailey, J. V.↗
DOE OSTI2019

Microstructure Evolution During Controlled Solidification of “Fe{sub 2}O{sub 3}”-CaO-SiO{sub 2} Liquids in Air

The principal chemical components in iron ore sintering are Fe{sub 2}O{sub 3}, CaO, and SiO{sub 2}. This sintering process consists of three key steps: heating, holding at peak temperature, and cooling. During the cooling stage, a liquid oxide solidifies to form the final sinter microstructures. To investigate the fundamental processes taking place during the cooling of sinters, a new experimental technique has been developed that allows the stages of solidification to be determined in isolation, rather than inferred from the final microstructures. Fe{sub 2}O{sub 3}-CaO-SiO{sub 2} oxide samples of a bulk composition having a CaO/SiO{sub 2} mass ratio of 3.46 and 73.2 wt pct Fe{sub 2}O{sub 3} were cooled in air from 1623 K (1350 °C) at 2 K/s, quenched at 5 K temperature intervals from 1533 K to 1453 K (1260 °C to 1180 °C), and analyzed using Electron Probe Micro X-Ray Analysis (EPMA). During cooling, four distinct stages were observed, consisting of the phase assemblages Liquid + Hematite (I), Liquid + Hematite + C{sub 2}S(II), Liquid + C{sub 2}S + CF{sub 2}(III), and C{sub 2}S + CF{sub 2} + CF (IV). This solidification sequence differs from that predicted under equilibrium and Scheil–Gulliver Cooling. Importantly, no Silico-Ferrite of Calcium (SFC) phase was observed to form on solidification of the liquid. Based on the microstructures formed and liquid compositions, measured by EPMA, it was demonstrated that kinetic factors play a major role in determining the phases and microstructures formed under the conditions investigated.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Oxide Solubility Minimum in Liquid Fe-M-O Alloy

The origin of the solubility minimum of oxide (M{sub x}O{sub y}) in liquid Fe-M-O alloy was investigated, and the minimum was predicted based on thermodynamic calculations. Due to the characteristic property of activities of M and O in the liquid, a maximum exists in the product between the two activities if the affinity of M to O is significantly high, as most deoxidizing elements are. A critical activity product is defined, which is an indicator of the solubility minimum of the M{sub x}O{sub y} in the liquid Fe-M-O alloy according to the following relationship: max(a{sub M}{sup x}×a{sub O{sub -}{sup y}})=K{sub M{sub xO{sub y}}}×a{sub M{sub xO{sub y}}}, where the a{sub M{sub xO{sub y}}} is unity if the alloy is in equilibrium with the pure M{sub x}O{sub y}. The origin of the solubility minimum was explained using the change of the activity product by composition. Available CALPHAD assessments for several binary Fe-M liquid alloys and Wagner’s solvation shell model were combined to calculate the activity product in the Fe-M-O alloy, which can be used to predict the solubility minimum of M{sub x}O{sub y}. A favorable agreement was obtained when M=Al, B, Cr, Mn, Nb, Si, Ta, Ti, V, and Zr. The Gibbs energy of dissolution of O in pure liquid M (Δg{sub O{sub -(M)}{sup ∘}}) and the Gibbs energy of the formation of M{sub x}O{sub y} per mole of atoms (Δg{sub M{sub xO{sub y}{sup ∘}}}/(x+y)) play important roles in determining the solubility minimum, as long as an interaction between Fe and M is less significant than the interaction between metal (Fe and M) and O. Predictions of the solubility minima of CaO and MgO were not satisfactory, requiring further improvement of the present analysis.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Quantum Magnetic Properties and Metal‐to‐Insulator Transition in Chemically Doped Calcium Ruthenate Perovskite

Ruthenates provide a comprehensive platform to study a plethora of novel properties, such as quantum magnetism, superconductivity, and magnetic fluctuation mediated metal–insulator transition (MIT). Herein, an overview of quantum mechanical phenomenology in calcium ruthenium oxide with varying compositions is provided. While the stoichiometric composition of exhibits non‐fermi liquid (FL) behavior with quasi‐criticality, chemically doped compounds depict prominent signatures of quantum magnetic fluctuations at low temperature that in some cases are argued to mediate in metal–insulator transition. In the case of cobalt‐doped , an unusual continuum fluctuation is found to persist deep inside the glassy phase of the material. These observations reflect the richness of the ruthenate research platform in the study of quantum magnetic phenomena of fundamental importance.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Furfural Upgrading by Aldol Condensation with Ketones over Solid-Base Catalysts

Aldol condensation reactions between furfural and various ketones were studied in a flow reactor at 373 K and 100 psi for application to upgrading of furfural. Specific rates for the reaction of acetone and furfural were measured on MgAl 2 O 4 , Al 2 O 3 , CaO/MgAl 2 O 4 and MgO/MgAl 2 O 4 and found to be highest on CaO/MgAl 2 O 4 . While the presence of CO 2 and H 2 O did not affect the stability of the CaO/MgAl 2 O 4 catalyst, the catalyst deactivated over a period of a few hours due to the production of 2-furoic acid formed by the Cannizzaro reaction. While aldol condensation rates between furfural and either 2-pentanone and decanal approached that of acetone, rates for 4-heptanone and 2,5-heptanedione were significantly lower because the α-hydrogens of the carbonyl compounds are less easily attacked in these molecules. The selectivity to aldol products is affected by the relative rates of the aldol-condensation and the Cannizzaro reactions. Possible strategies for maximizing production of the aldol products with larger ketones are discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Assessment of Physicochemical Properties of Electrical Arc Furnace Slag and Their Effects on Foamability

The composition of slags of an electric arc furnace (EAF) in a commercial melt shop was systematically analyzed with a focus on slag foaming. Basic behavior of FeO in an EAF slag was confirmed using fundamental thermodynamics. Monoxide ([Mg,Fe,Mn]O = M’O) and spinel ([Mg,Fe]Al{sub 2}O{sub 4}) phases in EAF slag were confirmed by X-ray diffraction analysis, and these results were interpreted in the context of equilibrium cooling calculation using FactSage™ software. Furthermore, the distribution of MgO with respect to the M’O-saturation limit at different basicity ratios (=CaO/SiO{sub 2}=C/S) and temperatures was evaluated. In particular, the relationship between MgO and FeO for C/S ratios ranging from 1.3 to 1.6 was considered with reference to phase equilibria. Foam height was affected by slag viscosity (η) and gas generation according to changes in C/S ratio and FeO content. Foaming index (Σ) decreased with the increasing C/S ratio and FeO content. The measured foam heights were relatively higher than the calculated values, and the result indicates that the effect of M’O on slag foaming in commercial process is remarkable. Therefore, slag chemistry should be optimized based on thermodynamic considerations and thermophysical properties to achieve good foaming characteristics.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Reactions of self-healing agents and the chemical binding of aggressive ions in sea water: Thermodynamics and kinetics

New self-healing agents that can chemically bind seawater ions invading cracked cementitious materials were proposed. The potential of self-healing and binding of seawater ions were investigated by thermodynamic modeling. It was found that CaO-NaAlO{sub 2} and CaO-metakaolin agents can have Cl{sup −}, SO{sub 4}{sup 2−} and Mg{sup 2+} chemically bound by reacting with sea water to form Friedel's salt, Kuzel's salt, ettringite and hydrotalcite. The removal of Cl{sup −} from seawater firstly increased and then decreased with the increase of Ca/Al molar ratio in both agents, while the removal of Mg{sup 2+} and SO{sub 4}{sup 2−} were hardly influenced and approximated 100%. Because NaAlO{sub 2} dissolves and releases Al(OH){sub 4}{sup −} rapidly, precipitates binding Cl{sup −}, SO{sub 4}{sup 2−} and Mg{sup 2+} were formed fast. In comparison, the reaction of metakaolin binding aggressive ions occurred after 3 days. Because of the faster reaction and the capacity to make [Cl{sup −}]/[OH{sup −}] lower in the solution, CaO-NaAlO{sub 2} would be more efficient for self-healing and mitigating reinforcement corrossion than CaO-metakaolin.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Influence of CaO/FeO ratio on the formation mechanism and properties of alkali-activated Fe-rich slags

Highlights: • Effect of the CaO/FeO molar ratio in alkali-activated Fe-rich slags is unraveled. • Low CaO/FeO molar ratios enhance the early kinetics and compressive strength. • Reaction extent and strength further increase with higher CaO/FeO ratio after 7 days. • Fe{sup 2+}-trioctahedral layers of the binder are hydroxylated and in a silicate phase. • The final strength is determined by the influence of Ca on the reaction products. In the search for CO{sub 2} mitigating cement technologies, alkali-activated Fe-rich slags present a possible alternative. The influence of the chemical composition of the synthetic Fe-silicate slag on the reaction mechanisms is assessed by varying the CaO/FeO molar ratio. The alkali-activated Fe-rich slags consist of trioctahedral layers that are shown to be hydroxylated and in contact with silicates, in a similar way to phyllosilicate minerals. The formation of this phyllosilicate-like structure is hindered during the first days for samples with high CaO/FeO ratios, because of the partial incorporation of Ca in the trioctahedral layers. At later ages, the samples with higher CaO/FeO ratios gain in reaction extent, to exceed the reaction extent of low CaO/FeO ratios at 28 days and beyond. The increase in compressive strength is even more pronounced than the effect on the reaction extent, which underlines the importance of Ca on the inherent strength of the binding phases.

36 MATERIALS SCIENCE↗