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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

High-Rate and Low-Temperature Fabrication of Cu(In,Ga)Se 2 Solar Cells Using AgBr Induced Recrystallization

We present results demonstrating a three-stage, high-rate, low-temperature deposition process for Cu(In,Ga)Se 2 solar cells including a recrystallization step after the second stage, catalyzed by AgBr. The entire deposition and recrystallization process takes place below 450 °C in less than 15 min. Device results with efficiencies exceeding 16% are shown. Here, we achieve very high levels of grain growth and a greater than a 5% absolute increase in device performance because of the recrystallization step relative to an identical process not involving AgBr.

14 SOLAR ENERGY↗
DOE OSTI2026

Low Temperature Tantalum Electrodeposition: Enabling Next Generation Coatings

This project aimed to identify the ligand and solvation conditions necessary for the electrodeposition of refractory metals from low-temperature organic electrolytes. Tantalum (Ta) was chosen as a specific exemplar for programmatic purposes. It was hoped that a deeper understanding of these relationships could facilitate the innovative application of refractory metal coatings on thermally sensitive and geometrically intricate components used in extreme environments related to energy generation and storage, nuclear deterrence, aerospace, defense, and beyond.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Unconventional low temperature decomposition of a saturated hydrocarbon over atomically-dispersed titanium-aluminum-boron catalyst

Sonochemically-synthesized atomically-dispersed titanium-aluminum-boron nanopowder (TiAlB NP) exhibits a remarkable low-temperature catalytic activation of aliphatic C-H bonds at 750 K followed by C-C bond activation thus emerging as a potent low-cost alternative to expensive platinum group metals. Here, the model saturated hydrocarbon, exo-tetrahydrodicyclopentadiene (C10H16), undergoes catalytic decomposition on TiAlB NPs in a chemical microreactor to produce 1,3-cyclopentadiene (c-C5H6), cyclopentene (c-C5H8), and molecular hydrogen (H2) as detected in situ via isomer-selective, single-photon ionization time-of-flight mass spectrometry. Extensive electronic structure theory calculations on model clusters of the catalyst decode a unique synergy among the atomic constituents of the catalyst and chemical bonding in this stepwise, retro Diels Alder reaction: Ti, although insensitive to C-H activation in its metallic state, initiates the catalysis via chemisorption of the hydrocarbon, adjacent B centers readily abstract hydrogen atoms and store them during the catalytic cycle, while Al stabilizes the catalyst structure yet providing space for critical docking sites for the departing hydrocarbons.

Biswas, Souvick↗
DOE OSTI2022

Cryogenic User Facilities for R&D on Noble Liquid Detectors and Low Temperature Devices

Cryogenic test facilities are critical infrastructure for physics experiments in a variety of fields, perhaps most notably for particle detection with noble liquid detectors, low-temperature device development, and quantum information research. However, considerable investment and technical knowledge are required to construct and operate such facilities. This white paper discusses proposals for user facilities aimed at broadening the availability of testing capabilities for the scientific community.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Adaptation strategies of giant viruses to low-temperature marine ecosystems

Abstract Microbes in marine ecosystems have evolved their gene content to thrive successfully in the cold. Although this process has been reasonably well studied in bacteria and selected eukaryotes, less is known about the impact of cold environments on the genomes of viruses that infect eukaryotes. Here, we analyzed cold adaptations in giant viruses (Nucleocytoviricota and Mirusviricota) from austral marine environments and compared them with their Arctic and temperate counterparts. We recovered giant virus metagenome-assembled genomes (98 Nucleocytoviricota and 12 Mirusviricota MAGs) from 61 newly sequenced metagenomes and metaviromes from sub-Antarctic Patagonian fjords and Antarctic seawater samples. When analyzing our data set alongside Antarctic and Arctic giant viruses MAGs already deposited in the Global Ocean Eukaryotic Viral database, we found that Antarctic and Arctic giant viruses predominantly inhabit sub-10°C environments, featuring a high proportion of unique phylotypes in each ecosystem. In contrast, giant viruses in Patagonian fjords were subject to broader temperature ranges and showed a lower degree of endemicity. However, despite differences in their distribution, giant viruses inhabiting low-temperature marine ecosystems evolved genomic cold-adaptation strategies that led to changes in genetic functions and amino acid frequencies that ultimately affect both gene content and protein structure. Such changes seem to be absent in their mesophilic counterparts. The uniqueness of these cold-adapted marine giant viruses may now be threatened by climate change, leading to a potential reduction in their biodiversity.

Environmental Sciences & Ecology↗
DOE OSTI2020

Insights into the Biogeochemical Cycling of Cobalt: Precipitation and Transformation of Cobalt Sulfide Nanoparticles under Low-Temperature Aqueous Conditions

Cobalt sulfide precipitates, key phases in the natural biogeochemical cycling of cobalt and in relevant remediation and resource recovery processes, remain poorly defined under low-temperature aqueous conditions. Here, we systematically studied the Co-(Fe) sulfides precipitated and aged in environmentally relevant solutions, defined by different combinations of pH, initial cobalt-to-iron ratios ([Co] aq /[Fe] aq ), with/without S 0 , and the presence/absence of sulfate-reducing bacteria. The initial abiogenic precipitates without Fe aq were composed exclusively of amorphous Co-sulfide hydrates (CoS· x H 2 O), whose estimated log K* was three orders of magnitude higher than that previously reported for crystalline Co-sulfides. The addition of S 0 , in combination with acidic pH and elevated temperature (60°C), resulted in the recrystallization of the amorphous precipitates into nanocrystalline jaipurite (hexagonal CoS) within one month (which otherwise remained stable for up to two months). In the presence of Fe(II) aq , the abiogenic precipitates were composed of more crystalline Co-sulfide hydrates and/or Co-rich mackinawite, the exact phase being dependent on the specific [Co] aq /[Fe(II)] aq . The biogenic precipitates displayed higher crystallinity for Co sulfides (up to the formation of nanocrystalline cobalt pentlandite, Co 9 S 8 ) and lower crystallinity for Co-rich mackinawite, suggestive of mineral-specific bacterial interaction. The revealed precipitation and transformation pathways of Co-(Fe-)sulfides in this study allows for predicting the prevalent Co-bearing phases in various natural and engineered environments.

58 GEOSCIENCES↗
DOE OSTI2024

Low-Temperature Activation and Coupling of Methane on MgO Nanostructures Embedded in Cu 2 O/Cu(111)

Here, the efficient conversion of methane into valuable hydrocarbons such as ethane and ethylene at relatively low temperatures without deactivation issues is crucial for advancing sustainable energy solutions. Herein, AP-XPS and STM studies show that MgO nanostructures (0.2-0.5 nm wide, 0.4-0.6 Å high) embedded in a Cu 2 O/Cu(111) substrate activate methane at room temperature, mainly dissociating it into CH x (x = 2 or 3) and H adatoms, with minimal conversion to C adatoms. These MgO nanostructures in contact with Cu 2 O/Cu(111) exhibit unique reactivity, enabling C-C coupling into ethane and ethylene at 500 K, a significantly lower temperature than that required for bulk MgO catalysts (>700 K), with negligible carbon deposition and no deactivation. DFT calculations corroborate these experimental findings. The CH 4,gas → *CH 3 +*H reaction is a downhill process on MgO/Cu 2 O/Cu(111) surfaces. The activation of methane is facilitated by an electron transfer from copper to MgO and the existence of Mg and O atoms with a low coordination number in the oxide nanostructures. The formation of O-CH 3 and O-H bonds overcomes the energy necessary for the cleavage of a C-H bond in methane. DFT studies reveal that smaller Mg 2 O 2 model clusters provide stronger binding and lower activation barriers for C-H dissociation in CH 4 , while larger Mg 3 O 3 clusters promote C-C coupling due to weaker *CH 3 binding. All these results emphasize the importance of size when optimizing the catalytic performance of MgO nanostructures in the selective conversion of methane.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Balancing sugar recovery and inhibitor generation during energycane processing: Coupling cryogenic grinding with hydrothermal pretreatment at low temperatures

Pretreatment of lignocellulosic biomass at high temperatures or with oxidizing chemicals generate various inhibitors that restrict the efficient bioconversion of sugars in subsequent steps. The present study systematically investigates individual and combinatorial effects of pretreatment parameters on the generation of inhibitors. Herein, a plot between pretreatment temperature and inhibitor revealed optimum pretreatment temperature for energycane bagasse i.e., 170 °C beyond which total inhibitor production increased exponentially. No inhibitor production was observed on mechanical processing i.e., disk milling/cryogenic grinding of biomass. Evaluation of response surface regression exhibited that biomass solids loading has a significant effect on inhibitor generation at higher temperatures. The concentrations of certain inhibitors such as acetic acid, furfurals, and HMF increased more than 3-folds on doubling the solids loading. Furthermore, a novel low-severity approach of low-temperature hydrothermal pretreatment coupled with cryogenic grinding for lignocellulosic biomasses has been introduced which improved sugar yields while maintaining a low inhibitor concentration.

09 BIOMASS FUELS↗
DOE OSTI2022

Understanding the low-temperature chemistry of 1,2,4-trimethylbenzene

1,2,4-trimethylbenzene is an important representative aromatic component of gasoline/diesel/jet fuels and thus it is necessary to understand its low-temperature chemistry. In this paper, ignition delay times (IDTs) of both 1,2,4-trimethylbenzene (124TMB) and its blends with n -heptane were measured at engine-like conditions using both a high-pressure shock tube and a rapid compression machine for fuel in ‘air’ mixtures at pressures of 10 and 30 atm and at temperatures in the range 600 – 1100K. The experiments in this study show for the first time that 124TMB presents a two-stage ignition behavior at engine relevant conditions. Blending n -heptane with 124TMB can significantly increase mixture reactivity at temperatures below 1000K. A new detailed mechanism has been developed to simulate the experimentally measured IDT data. The mechanism can capture well the two-stage ignition behavior as well as the ignition delays at different pressures, equivalence ratios over a wide temperature range, for both pure fuels and their blended mixtures. Flux analyses show that the benzylic radicals (formed via H-atom abstraction from the methyl groups ortho-sites on 124TMB) can add to O 2 forming $\mathrm{R\dot{O}_2}$ radicals, which can isomerize to $\dot{Q}$OOH by intramolecular H-atom transfer from the ortho- methyl group and these $\dot{Q}$OOH radicals undergo a second addition to O 2 . This is analogous to the chain branching reaction pathways of alkanes. The chain branching reaction pathways are responsible for the first-stage heat release of 124TMB. In conclusion, the competitions between chain branching and both chain propagating and chain termination reaction pathways lead to a less pronounced negative temperature coefficient (NTC) behavior for 124TMB oxidation, compared to two-stage ignition behavior observed for alkanes and other fuels.

1,2,4-trimethylbenzene↗
DOE OSTI2022

Quantification of Key Peroxy and Hydroperoxide Intermediates in the Low-Temperature Oxidation of Dimethyl Ether

Dimethyl ether (DME) oxidation is a model chemical system with a small number of prototypical reaction intermediates that also has practical importance for low-carbon transportation. Although it has been studied experimentally and theoretically, ambiguity remains in the relative importance of competing DME oxidation pathways in the low-temperature autoignition regime. To focus on the primary reactions in DME autoignition, we measured the time-resolved concentration of five intermediates, CH 3 OCH 2 OO (ROO), OOCH 2 OCH 2 OOH (OOQOOH), HOOCH 2 OCHO (hydroperoxymethyl formate, HPMF), CH 2 O, and CH 3 OCHO (methyl formate, MF), from photolytically initiated experiments. We performed these studies at P = 10 bar and T = 450-575 K, using a high-pressure photolysis reactor coupled to a time-of-flight mass spectrometer with tunable vacuum-ultraviolet synchrotron ionization at the Advanced Light Source. Our measurements reveal that the timescale of ROO decay and product formation is much shorter than predicted by current DME combustion models. The models also strongly underpredict the observed yields of CH 2 O and MF and do not capture the temperature dependence of OOQOOH and HPMF yields. Adding the ROO + OH $\rightarrow$ RO + HO 2 reaction to the chemical mechanism (with a rate coefficient approximated from similar reactions) improves the prediction of MF. Increasing the rate coefficients of ROO ↔ QOOH and QOOH + O 2 ↔ OOQOOH reactions brings the model predictions closer to experimental observations for OOQOOH and HPMF, while increasing the rate coefficient for the QOOH $\rightarrow$ 2 CH 2 O + OH reaction is needed to improve the predictions of formaldehyde. In conclusion, to aid future quantification of DME oxidation intermediates by photoionization mass spectrometry, we report experimentally determined ionization cross-sections for ROO, OOQOOH, and HPMF.

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

Low-temperature spin Seebeck effect in nonmagnetic vanadium dioxide

The spin Seebeck effect (SSE) is sensitive to thermally driven magnetic excitations in magnetic insulators. Vanadium dioxide in its insulating low-temperature phase is expected to lack magnetic degrees of freedom, as vanadium atoms are thought to form singlets upon dimerization of the vanadium chains. Instead, we find a paramagnetic SSE response in V⁢O 2 films that grows as the temperature decreases below 50 K. The field and temperature-dependent SSE voltage is qualitatively consistent with a general model of paramagnetic SSE response and inconsistent with triplet spin transport. Quantitative estimates find a spin Seebeck coefficient comparable in magnitude to that observed in strongly magnetic materials. Finally, the microscopic nature of the magnetic excitations in V⁢O 2 requires further examination.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

A planar-sheet nongraphitic zero-bandgap sp 2 carbon phase made by the low-temperature reaction of γ-graphyne

The highest sheet symmetry form of graphyne, with one triple bond between each neighboring hexagon in graphene, irreversibly transforms exothermically at ambient pressure and low temperatures into a nongraphitic, planar-sheet, zero-bandgap phase consisting of intrasheet-bonded sp 2 carbons. The synthesis of this sp 2 carbon phase is demonstrated, and other carbon phases are described for possible future synthesis from graphyne without breaking graphyne bonds. While measurements and theory indicate that the reacting graphyne becomes nonplanar because of sheet wrinkling produced by dimensional mismatch between reacted and nonreacted sheet regions, sheet planarity is regained when the reaction is complete. Although the observed elimination of triple bonds to make parallel planar sp 2 carbon sheets likely requires ordered transformation within each sheet, diffraction data for reacted multisheet stacks indicate that the relative lateral positions of neighboring sheets are disordered, as predicted, since no crystalline diffraction peak (other than for the intersheet spacing) is observed.

Aliev, Ali E. (ORCID:0000000300349707)↗
DOE OSTI2024

State of the art in low-temperature and high-temperature electrolysis

Water electrolysis is gaining traction in large-scale applications, with production of multiple technologies scaling to hundreds and thousands of megawatts of new electrolyzer capacity annually. Low-temperature electrolysis has dominated the electrolyzer market for decades, but still only represents a small amount of the overall hydrogen market, due to the higher production costs versus hydrogen derived from fossil fuels. Advances are needed in capital cost and efficiency to close the cost gap, especially for energy applications. Similarly, while high-temperature electrolyzers can operate more efficiently, reducing the operating cost, they still need further scale-up and cost reduction to compete in these markets. Understanding the recent advances in each and the priority research directions is important to focus and accelerate innovation, and will be discussed in this article. The different advantages and disadvantages of each of these technologies will also be reviewed; there will likely be applications for each in the overall deployment of renewable hydrogen.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Low temperature process for diode termination of fully depleted high resistivity silicon radiation detectors that can be used for shallow entrance windows and thinned sensors

Fabrication of vertical diodes for radiation sensing using a low temperature microwave anneal is provided. This kind of anneal allows the back side processing to be performed after the front side processing is done without damaging the front side structures. This enables a simplified fabrication of thinned detectors compared to a conventional silicon on insulator process. Another feature that this technology enables is a thin entrance window for a detector that also serves as the doped diode termination. Such thin entrance windows are especially suitable for detection of low energy radiation.

Kenney, Christopher J.↗
DOE OSTI2021

Effect of Low Temperature Nitrogen Baking on Superconducting Radio Frequency Cavities With Different Frequency

We report the rf performance of several single-cell superconducting radiofrequency cavities frequency ranging from 1.3-3.0 GHz after low temperature baking in nitrogen environment The cavities are treated at different temperature in the range of (120-160oC) for extended period of time (~24-48 hours) with nitrogen gas injection in the furnace. The improvement in Q0 with Q-rise in some case was observed when nitrogen gas was injected at elevated temperature (~250-290 oC) and held at the temperature range 120-200 oC without any degradation in accelerating gradient over the baseline performance. The temperature and time of baking play significant role in dependence of quality factor on accelerating gradient.

Khanal, B.↗
DOE OSTI2020

Suppression of low temperature magnetic ordering in samarium nanoparticles

The role of finite size effects on magnetic order has been investigated in samarium nanoparticles prepared by physical vapor deposition. In this study, a dense layer composed of distinct nanoparticles with a mean particle diameter of 26 nm was deposited on a diamagnetic substrate. M(T) measurements identify the expected pair of antiferromagnetic ordering temperatures in the bulk Sm precursor, at 113 K and 14 K, where the magnetic unit cell for the lower ordering temperature is 10.36 nm along the c-axis. The high temperature ordering of the hexagonal sites in the Sm nanocrystals is slightly decreased with respect to that of bulk Sm, while the low temperature transition associated with the cubic sites is significantly suppressed. The observed changes are attributed to finite size effects, with ordering suppressed as the particle radius approaches the length of the magnetic unit cell, and surface moments become more prominent.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Innovative SCR Materials and System for Low Temperature Aftertreatment

US automotive OEMs are required to meet the twin challenge of corporate average fleet fuel economy of 54.5 mpg and stringent Bin30/SULEV30 emissions standards for light duty vehicles by 2025. This creates a heavy burden on the R&D community to discover and develop the necessary enabling technologies by 2023 to integrate into powertrain systems intended for 2025. Further amplifying the emissions challenge is the reduction in engine exhaust energy resulting from more fuel-efficient powertrains and the regulatory requirement of 15-year system performance. This forces aftertreatment systems to continue to push their operational limits to increasingly lower temperatures. This CRADA will focus on a broad and very important area of critical relevance to DOE and Stellantis, i.e., development of low temperature aftertreatment approaches, while not sacrificing durability.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2021

Low-Temperature 2D/2D Ohmic Contacts in WSe 2 Field-Effect Transistors as a Platform for the 2D Metal–Insulator Transition

in this work, we report the fabrication of hexagonal-boron-nitride (hBN) encapsulated multiterminal WSe 2 Hall bars with 2D/2D low-temperature Ohmic contacts as a platform for investigating the two-dimensional (2D) metal-insulator transition. We demonstrate that the WSe 2 devices exhibit Ohmic behavior down to 0.25 K and at low enough excitation voltages to avoid current-heating effects. Additionally, the high-quality hBN-encapsulated WSe 2 devices in ideal Hall-bar geometry enable us to accurately determine the carrier density. Measurements of the temperature (T) and density (n s ) dependence of the conductivity σ(T, n s ) demonstrate scaling behavior consistent with a metalinsulator quantum phase transition driven by electron-electron interactions, but where disorder-induced local magnetic moments are also present. Our findings pave the way for further studies of the fundamental quantum mechanical properties of 2D transition metal dichalcogenides using the same contact engineering.

2D materials↗