Carbon dioxide-negative composite materials: an economically viable solution for CO 2 sequestration
Carboxylating lignin and lignite fillers to sequester CO 2 in composite materials.
CO2 capture↗
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Results for “Chemical Engineering”
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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A fundamental study of lignin reactions with formaldehyde and glyoxal
Lignin-glyoxal: a fully biobased wood adhesive.
Siahkamari, Mohsen [Department of Forestry, Michig↗
Heterogenous HER activity of Ni( ii )N 2 S 2 molecular catalysts
Structure-activity relationship of surface immobilized electrocatalysts shows overpotential dependence on ligand basicity and steric accessibility.
Paudel, Mohan [Department of Chemistry, University↗
Atomic-scale defects generated in the early/intermediate stages of dielectric breakdown in Si/SiO 2 transistors
In this study, electrically detected magnetic resonance and near-zero-field magnetoresistance measurements were used to study atomic-scale traps generated during high-field gate stressing in Si/SiO 2 MOSFETs. The defects observed are almost certainly important to time-dependent dielectric breakdown. The measurements were made with spin-dependent recombination current involving defects at and near the Si/SiO 2 boundary. The interface traps observed are P b0 and P b1 centers, which are silicon dangling bond defects. The ratio of P b0 /P b1 is dependent on the gate stressing polarity. Electrically detected magnetic resonance measurements also reveal generation of E' oxide defects near the Si/SiO 2 interface. Near-zero-field magnetoresistance measurements made throughout stressing reveal that the local hyperfine environment of the interface traps changes with stressing time; these changes are almost certainly due to the redistribution of hydrogen near the interface.
42 ENGINEERING↗
Low voltage AC electroluminescence in silicon MOS capacitors
Low power silicon based light source and detector are attractive for on-chip photonic circuits given their ease of process integration. However, conventional silicon light emitting diodes emit photons with energies near the band edge where the corresponding silicon photodetectors lack responsivity. On the other hand, previously reported hot carrier electroluminescent silicon devices utilizing a reverse biased diode require high operating voltages. Here, we investigate hot carrier electroluminescence in silicon metal–oxide–semiconductor capacitors operating under transient voltage conditions. Further, during each voltage transient, large energy band bending is created at the edge of the source contact, much larger than what is achievable at a steady state. As a result, electrons and holes are injected efficiently from a single source contact into the silicon channel at the corresponding voltage transient, where they subsequently undergo impact ionization and phonon-assisted interband recombination. Notably, we show low voltage operation down to 2.8 V by using a 20 nm thick high-κ gate dielectric. We show further voltage scaling is possible by reducing the gate dielectric thickness, thus presenting a low voltage platform for silicon optoelectronic integrated circuits.
42 ENGINEERING↗
Chemical bond and phase stability of Ga-doped Sm2Fe17Cx magnet
Sm2Fe17C3 phase (2:17) is metastable and exhibits excellent intrinsic hard magnetic properties. Doping elements such as Ga facilitate the formation of a single-phase 2:17 structure in arc-melted Sm2Fe17Cx alloys, which opens a promising route for fabricating fully dense bulk Sm2Fe17Cx magnets via high-temperature techniques such as melting and sintering. First-principles electronic structure calculation indicates that Ga prefers to partially replace Fe at the 9d and 18h crystallographic sites in Sm2Fe17C3 and Sm2Fe17, respectively. This difference in site preference is attributed to the distinct chemical environments surrounding the Fe atoms in the two compounds. Ga substitution favors the Sm–Ga bonding formation while avoiding Ga–C interactions. Doped Ga atoms result in more negative formation energy in Sm2(Fe, Ga)17C3, indicating improved structural stability. Crystal Orbital Hamilton Population analysis reveals that carbon insertion weakens the bonding of Sm-Fe (18h) and Sm-Fe (18f) in Sm2Fe17C3. Ga doping facilitates electron redistribution across chemical bonds, thereby reinforcing Fe(18h)–Sm and Fe(18f)–Sm interactions and stabilizing the carbon-centered octahedral local structure. This synergistic effect contributes significantly to the observed enhancement in phase stability of Sm2(Fe, Ga)17Cx. These findings suggest that chemical bond engineering through the selective doping of Ga can enhance phase stability and facilitate the synthesis of Sm2Fe17C3, providing a viable strategy for developing advanced magnets.
Liu, Xubo [Critical Materials Innovation Hub, Divi↗
Probing exchange bias at the surface of a doped ferrimagnetic insulator
With the realization of stress-induced perpendicular magnetic anisotropy, efficient spin-orbit torque switching, and room temperature topological Hall effect, interest in rare earth iron garnets has been revived in recent years for their potential in spintronic applications. In this study, we investigate the magnetic properties of micrometer-thick Bi and Ga substituted thulium iron garnets (BiGa:TmIG) grown by the liquid-phase epitaxy method. Above the magnetization compensation (MC) temperature, anomalous triple hysteresis is observed in BiGa:TmIG/Pt heterostructures by anomalous Hall effect measurements. X-ray magnetic circular dichroism and energy dispersive spectroscopy measurements reveal its origin as an internal exchange bias (EB) effect arising from inhomogeneities localized at the surface of the film. Possibly depending on the difference in thickness and defect realization of the EB layer, two types of magnetization reversal mechanisms, namely, the Stoner-Wohlfarth type and the reversible domain-wall motion type, are observed. Furthermore, our results show that rich meta-magnetic phases exist in garnets close toMC, which can be robustly tuned by chemical composition engineering and conveniently probed by electrical transport measurements.
36 MATERIALS SCIENCE↗
Tutorial on forming through-silicon vias
Through-silicon vias (TSVs) are a critical technology for three-dimensional integrated circuit technology. These through-substrate interconnects allow electronic devices to be stacked vertically for a broad range of applications and performance improvements such as increased bandwidth, reduced signal delay, improved power management, and smaller form-factors. There are many interdependent processing steps involved in the successful integration of TSVs. This article provides a tutorial style review of the following semiconductor fabrication process steps that are commonly used in forming TSVs: deep etching of silicon to form the via, thin film deposition to provide insulation, barrier, and seed layers, electroplating of copper for the conductive metal, and wafer thinning to reveal the TSVs. Recent work in copper electrochemical deposition is highlighted, analyzing the effect of accelerator and suppressor additives in the electrolyte to enable void-free bottom-up filling from a conformally lined seed metal.
42 ENGINEERING↗
Human NLRP3 inflammasome activation leads to formation of condensate at the microtubule organizing center
The NLRP3 inflammasome is a multiprotein molecular machine that drives inflammatory responses in innate immunity. Although its dysregulation is implicated in numerous human diseases, its structural organization in cells remains poorly understood. Here, we used precise fluorescence-guided cryo–focused ion beam (cryo-FIB) milling and cryo–electron tomography (cryo-ET) to visualize NLRP3 inflammasomes in situ within human macrophages at various stages of activation. After priming and activation, we observed expansion and dispersion of Golgi cisternae, along with the emergence of 50-nanometer NLRP3-associated vesicles, which likely transport NLRP3 to the MTOC. Dense NLRP3-containing condensates then formed in and around the MTOC. In later stages, the condensates solidified, coincident with widespread mitochondrial damage, autophagy, and pyroptotic cell death.
Wang, Jue [Division of Chemistry and Chemical Engi↗
Enabling Lignin Valorization Through Integrated Advances in Plant Biology and Biorefining
Despite lignin having long been viewed as an impediment to the processing of biomass for the production of paper, biofuels, and high-value chemicals, the valorization of lignin to fuels, chemicals, and materials is now clearly recognized as a critical element for the lignocellulosic bioeconomy. However, the intended application for lignin will likely require a preferred lignin composition and form. To that end, effective lignin valorization will require the integration of plant biology, providing optimal feedstocks, with chemical process engineering, providing efficient lignin transformations. Recent advances in our understanding of lignin biosynthesis have shown that lignin structure is extremely diverse and potentially tunable, while simultaneous developments in lignin refining have resulted in the development of several processes that are more agnostic to lignin composition. Here, we review the interface between in planta lignin design and lignin processing and discuss the advances necessary for lignin valorization to become a feature of advanced biorefining.
09 BIOMASS FUELS↗
Confocal Raman Microscopy as a Probe of Material Deconstruction in Processed Low-Density Polyethylene Particles
Confocal Raman microscopy was applied to detect structural change within individual particles of low-density polyethylene (LDPE) following chemical and electrochemical processing steps that aimed to facilitate material decomposition. A high numerical aperture (NA) oil-immersion objective enabled depth-profiling through the near surface region (20 μm–40 μm) of irregularly shaped particles with an axial spatial resolution < 2 μm estimated from measurements of instrument detection efficiency profiles. Changes in vibrational bands sensitive to polyethylene crystallinity were evident following treatments and linked to the release of low molecular weight compounds present as additives and products of processing. Effects of processing were probed by monitoring the rise of Raman scattering intensity in vibrational modes associated with polyethylene chains in a zig-zag (trans) conformation near 1128 cm –1 , 1294 cm –1 , and 1418 cm –1 , signaling chain clustering and development of organized, crystalline-like assemblies. Pristine LDPE particles displayed a uniform structure across the near surface region, while particles treated initially with chemical extractant and then further processed displayed increasingly enhanced crystallinity up to the maximum depth probed (40 μm). As a step toward measurements on ensembles of particles, least squares modeling was adapted to derive pure component spectra reflecting crystallinity change within spectral datasets. The work demonstrates high spatial resolution Raman depth-profiling for the characterization of processed polymers using a high NA immersion objective to overcome the limitations of air-objectives often used for confocal Raman microscopy.
Wahiduzzaman, Md. [Department of Chemistry and Bio↗
Adjoint sensitivity analysis and data assimilation for verification of dry storage cask contents
Dry cask storage is a method for interim storage of spent fuel assemblies which contain fissile isotopes of uranium and plutonium. These can present a proliferation concern and consequently there is a need for non-destructive testing methods to verify a dry cask's contents for proliferation protection. We present an application of adjoint sensitivity analysis and data assimilation to a multigroup diffusion model of dry cask storage. Adjoint sensitivity analysis allows the efficient calculation of sensitivities for use in data assimilation to calibrate imprecisely known parameter values and data consistency tests to detect diversion scenarios. (authors)
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
"A" is for Ammonia: Why and How Fertilizer May Power the Planet [Slides]
Ammonia (chemical formula NH 3 ) is so pervasive in our history that human beings simply wouldn't exist without it: 4 billion people on this planet are fed by food grown using ammonia fertilizer, but this powerful molecule consumes nearly 2% of the world's energy supply to be produced at an industrial scale. This talk will first explore the energy challenges of ammonia's current means of industrial production, followed by a new vision for its synthesis using only renewable electricity, air and water, and opportunities to use ammonia as a hydrogen source. Fertilizer may one day fuel more than just our mouths.
08 HYDROGEN↗
"A" is for Ammonia: Why and How Fertilizer May Power the Planet [Slides]
Ammonia (chemical formula NH3) is so pervasive in our history that human beings simply wouldn't exist without it: 4 billion people on this planet are fed by food grown using ammonia fertilizer, but this powerful molecule consumes nearly 2% of the world's energy supply to be produced at an industrial scale. This talk will first explore the energy challenges of ammonia's current means of industrial production, followed by a new vision for its synthesis using only renewable electricity, air and water, and opportunities to use ammonia as a hydrogen source. Fertilizer may one day fuel more than just our mouths.
08 HYDROGEN↗
"A" is for Ammonia: Why and How Fertilizer May Power the Planet
Ammonia (chemical formula NH3) is so pervasive in our history that human beings simply wouldn't exist without it: 4 billion people on this planet are fed by food grown using ammonia fertilizer, but this powerful molecule consumes nearly 2% of the world's energy supply to be produced at an industrial scale. This talk will first explore the energy challenges of ammonia's current means of industrial production, followed by a new vision for its synthesis using only electricity, air and water, and opportunities to use ammonia as a hydrogen source. Fertilizer may one day fuel more than just our mouths.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Final report: Insights from ARM observations into aerosol processing and transport by extratropical cyclones and aerosol effects on cyclone clouds
This project advanced understanding of aerosol–cloud interactions in extratropical cyclones using observations from the Atmospheric Radiation Measurement (ARM) Eastern North Atlantic (ENA) observatory and ACE-ENA field campaigns, along with satellite datasets and numerical modeling. We have quantified the susceptibility of frontal clouds to aerosols, showing that this susceptibility is similar to that in non-frontal clouds despite substantial (factor 2) differences in droplet concentrations between these cloud types, and also significant differences in cloud albedo. A key finding was that Aitken-mode (here, 60-100nm diameter) aerosols play a disproportionately important role in droplet activation in frontal clouds, and concentrations of these particles are frequently strongly biased in climate models. Activation of aerosols depends strongly on updraft speeds, and via collaboration with Argonne National Laboratory we contributed to quantifying these better with the ARM radar wind profiler at the ENA site. Our studies in the North Atlantic have analogs in the Southern Ocean, and to draw these out we examined data from the MARCUS and SOCRATES field campaigns. We identified new particle formation within extratropical cyclones as a potentially important source of cloud condensation nuclei in these pristine marine environments. By combining ARM observations with perturbed parameter ensemble simulations, we demonstrated that surface observations can effectively constrain aerosol–cloud adjustments and reduce uncertainty in simulated cloud liquid water path responses by approximately 15%, yielding stronger constraints on historical aerosol cooling effects. The work further established precipitation processes as a dominant control on aerosol–cloud interactions and Earth system predictability.
Gordon, Hamish [Department of Chemical Engineering↗
Final Technical Report for Kokes Awards for the 29th North American Catalysis Society Meeting
Final Report
Hibbitts, David Douglas [Davidson School of Chemic↗
Investigation of Lunar Surface Chemical Contamination by LEM Descent Engine and Associated Equipment
Lunar surface and atmospheric contamination study caused by LEM rocket exhaust and inorganic, organic, and microbiological contaminants
MICROBIOLOGY↗