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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 1,063 records · Page 59
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Well–based monitoring of CO 2 geological sequestration operations in saline aquifers: Critical insights into key questions

Geological carbon sequestration in saline aquifers is one of the most promising strategies to help mitigate emissions of CO 2 to the atmosphere. Significant challenges in ensuring the security of the sequestration process rest in the evolution and expansion of the CO 2 plume in the subsurface. The ability to track the movement of the injected CO 2 poses another challenge. Critical questions related to the integrity of the sequestration operations in saline aquifers relate to plume characteristics that can we monitor using well-based variables. We addressed this and related questions using an integrated modeling framework through a numerical investigation of carbon sequestration in saline aquifers during long-term and post-injection periods. This modeling paradigm incorporates the effect of structural, geological, and petrophysical characteristics. That way, we can account for critical physicochemical processes, rock-fluid interactions, and lithology dependencies. The well fluid variables investigated include fluid composition, pH, fluid density, and ion activity. We learned that fluid property analytics and diagnostics can be powerful tools to estimate the movement of CO 2 and its storage in different trapping mechanisms. These analytics can help optimize operational aspects and simplify reservoir-scale models while still reflecting the complex nature of the CO 2 interactions underground and offering insights into plume evolution.

58 GEOSCIENCES↗
DOE OSTI2017

Effects of saturated lightweight sand content on key characteristics of ultra-high-performance concrete

In this study, 0 to 75% volume of river sand was replaced by an equivalent amount of pre-saturated lightweight sand (LWS) to enhance mechanical properties and reduce autogenous shrinkage of ultra-high-performance concrete (UHPC). The use of LWS is demonstrated to effectively decelerate and reduce the drop in internal relative humidity and autogenous shrinkage of UHPC. Isothermal calorimetry and thermal gravimetry results showed that the use of LWS promoted cement hydration degree after 28 d of hydration. Mercury intrusion porosimetry and scanning electron microscope analyses revealed that the porosity was decreased and interface properties between sand and cement matrix is enhanced by use of LWS up to 25%. The optimum replacement ratio of LWS to river sand was found to be 25%, which resulted in the highest compressive strength (168 MPa at 91 d), flexural strength (24 MPa at 28 d), and autogenous shrinkage limited to 365 μm/m at 28 d.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Key mechanisms controlling internal curing performance of natural fibers

Since the physical and chemical characteristics of wood pulps are complex, their behaviors in a cementitious matrix are difficult to capture by conventional techniques. Here, in situ NMR/MRI along with isothermal calorimetry and surface characterization methods are used to obtain new insights into the internal curing mechanisms of hardwood pulp-cement composites. It found that eucalyptus pulps release free water in their lumen structure within 25 h of hydration. Beyond 25 h, mostly free water in small cell wall pores and bound water in the cell wall are responsible for mitigation of the ongoing self-desiccation during continued cement hydration. Sorption results suggest that chemical wood pulps behave like a semi-permeable membrane, in which the greatest binding occurs for the most abundant cation. Surface analysis reveals discrete precipitates on the pulp surface, suggesting that it may facilitate nucleation of hydration products.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Key properties of mixed cerium and zirconium microspheres prepared by the internal gelation process with previously boiled HMTA and urea

The internal gelation process using previously boiled hexamethylenetetramine-urea was used in exploratory study to produce CeO 2 –ZrO 2 microspheres, which can serve as a simulant for ceramic transuranic fuel particles and as a viable three-way catalyst. The calcined CeO 2 and ZrO 2 microspheres with Barrett–Joyner–Halenda (BJH) pore size and volumes of 8–10 nm and 0.19–0.20 mL/g, respectively, had many more surface cracks than their relatively smooth CeO 2 –ZrO 2 counterparts even though the BJH pore sizes and volumes of mixed oxide spheres were lower at 3 nm and 0.11–0.12 mL/g, respectively. The Brunauer–Emmett–Teller (BET) surface areas for the CeO 2 and ZrO 2 microspheres were 74 and 93 m2/g, respectively, and the BET surface areas for the mixed oxides were much greater at 155–158 m 2 /g, which should improve catalytic performance. Overall, the catalytic activity of each microsphere composition was confirmed through the oxidation of carbon monoxide.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Elucidating key reducing species beyond ions in hydrogen plasma smelting reduction of iron ore

Hydrogen plasma smelting reduction (HPSR) of iron ore has attracted significant attention over the past decade due to its high-temperature operation, rapid plasma mediated reduction kinetics, and simpler density-based separation of molten iron product, compared to H2-based solid-state reduction. All of these attributes enable processing of low-grade ores for downstream use in electric-arc furnaces, as virgin iron with low gangue content is required for high quality steel and improved furnace operation. While positive ions exist within the plasma arc, this work demonstrates that near the anodic ore surface, hydrogen radicals and vibrationally excited hydrogen species dominate and their densities correlate well with observed reduction rates. Species concentrations in the transferred plasma arc and at the plasma-ore interface are evaluated using coupled thermal plasma and near-wall non-equilibrium plasma models. The thermal plasma model is validated against experimental voltage data and spectroscopic measurements of plasma temperature and density for varying current inputs. Modeling of the near surface thermochemical non-equilibrium and micrometer scale anode sheath layer reveals, in addition to the expected H + , significant concentrations of ArH + and H$^+_3$ ions, typically not observed in thermal plasmas under thermodynamic equilibrium. Our results show that the inverted sheath structure at the anodic ore surface strongly suppresses reactive positive ion fluxes, while non-equilibrium electron-impact processes generate abundant hydrogen radicals and vibrationally excited species. These findings highlight the critical role of non-equilibrium effects in hydrogen arc-driven iron ore reduction and advance understanding beyond prevailing hypotheses centered on hydrogen ion-driven mechanisms.

08 HYDROGEN↗
DOE OSTI2023

From electronic structure to model application of key reactions for gasoline/alcohol combustion: Hydrogen-atom abstractions by $CH_3\dot{O}$ radical

H-atom abstraction by methoxy radical ($CH_3\dot{O}$) plays an important role in capturing the kinetics of reactions between gasoline components and alcohols. This study focuses on determining the reaction rates and thermodynamic properties of methoxy radical reactions with five gasoline fuel components: n-heptane, iso-octane, 1-hexene, cyclopentane and toluene. Electronic structure calculations were per-formed for all the stationary points with M06-2X/6 -311 ++ g(d,p) method. G3 composite method with atomization method is used for determining Δ f H 0 of all the closed shell and radical species, using which the necessary thermodynamic data of all the species was determined. Coupled cluster theory QCISD(T)/cc-pVXZ (where X = D and T) and Møller-Plesset perturbation theory MP2/cc-pVXZ (where X = D, T and Q) were used to calculate single point energies. Subsequently, rate constants for all hydrogen atom ab-straction channels have been performed using conventional transition state theory with unsymmetric tunneling corrections. A systematic comparison of rates for abstraction from different sites within the same species and same site from different species is done in order to get insights into this reaction class. Here, the computed thermodynamic properties and rate constants were incorporated into a recent gasoline mechanism to investigate the impact of the calculations performed in this work. A shift in predicted NTC (negative temperature coefficient) behavior and significant reduction in model reactivity is observed upon incorporating the rates calculated herein.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2016

Sustainability as the key to prioritize investments in public infrastructures

Infrastructure construction, one of the biggest driving forces of the economy nowadays, requires a huge analysis and clear transparency to decide what projects have to be executed with the few resources available. With the aim to provide the public administrations a tool with which they can make their decisions easier, the Sustainability Index of Infrastructure Projects (SIIP) has been defined, with a multi-criteria decision system called MIVES, in order to classify non-uniform investments. This index evaluates, in two inseparable stages, the contribution to the sustainable development of each infrastructure project, analyzing its social, environmental and economic impact. The result of the SIIP allows to decide the order with which projects will be prioritized. The case of study developed proves the adaptability and utility of this tool for the ordinary budget management.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗