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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 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Insights into Dopant-Mediated Tuning of Silica-Supported Mo Metal Centers for Enhanced Olefin Metathesis

Here, we show that the electronic environment around active Mo centers supported on mesoporous silicates can be tuned by the addition of transition metals creating highly dispersed bimetallic catalysts that display enhanced activity for ethylene + 2-butene metathesis to propylene. The bimetallic catalysts are prepared by incorporating electrophilic Lewis acid metals (M) such as Nb, Ta, Zr, or Hf as dopant promoters into mesoporous KIT-6 supports using a one-pot sol–gel technique followed by impregnation of the Mo species. All the bimetallic Mo/M-KIT-6 catalysts display better activity than monometallic Mo/KIT-6 catalyst (28.7 ± 1.1 mmol (mol Mo s ) –1 ), with (Mo/Nb-KIT-6) catalysts exhibiting maximum propylene formation rates (54.2 ± 0.5 mmol (mol Mo s ) –1 ) at an identical Mo loading.

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

Chalcocarbogels as High-Capacity and Cycle-Stable Electrode Materials for Lithium and Sodium Ion Batteries

The low capacities of commercial Li ion batteries and cycle instabilities of amorphous metal sulfide based batteries impose constraints on their utilization for large-scale energy storage. We report here the acid-free, room-temperature (RT), and solution-based synthesis of a chalcogenide–carbonaceous hybrid aerogel, termed as “chalcocarbogel”, comprising molybdenum sulfide (MoS x ) and graphene oxide (GO). The chalcocarbogel is a nanoparticle-aggregated, porous, amorphous gel consisting of Mo 3 S 13 and Mo 2 S 12 -like structures as determined by synchrotron X-ray PDF, XANES, and EXAFS. The MoS x -GO chalcocarbogel demonstrates high specific capacities of ~1215 and ~807 mAh g –1 for Li/MoS x -GO and Na/MoS x -GO cells, respectively, for a 50 mAg –1 discharge rate during the first cycle. After the activation cycles, the MoS x -GO chalcocarbogel stabilizes, maintaining high specific capacities of approximately ~700 mAh g –1 for Li/MoS x -GO and ~473 mAh g –1 for Na/MoS x -GO cells, while continuously cycling. Importantly, the MoS x -GO aerogel reported here serves as a promising platform to develop chalcocarbogels for applications spanning both Li and Na ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2026

Assessing Structural, Thermal, and Functional Characteristics of Marigold Flower Protein as a Sustainable Food Ingredient

The demand for sustainable and alternative protein sources has been on the rise, driving interest in the valorization of underutilized plants. This study evaluated Calendula officinalis (marigold), a common floral waste, as a sustainable alternative protein source for the food industry. The primary objective of this study was to investigate the physicochemical properties of protein fractions from Calendula officinalis flower to evaluate their potential as a novel protein ingredient. Extraction of the Calendula officinalis flower yielded 92.17% of the crude protein. A sequential extraction of albumin, globulin, glutelin, and prolamin from marigold flower revealed albumin as the dominant fraction (65.47%) and exhibited the highest protein functionality, including water-holding capacity (2.37 g/g), oil-holding capacity (2.49 g/g), and emulsifying capacity (65.22 mL/g). Compared with other protein fractions, glutelin showed a relatively high emulsifying and foaming capacity (EC: 59.13 mL/g; FC: 16.23%). Differential scanning calorimetry revealed high thermal stability for albumin (T p = 105.28 °C) and glutelin (T p = 97.6 °C). Sodium Dodecyl Sulfate–Polyacrylamide Gel Electrophoresis (SDS-PAGE) and Liquid Chromatography–Mass Spectrometry (LC-MS) confirmed the presence of abundant low-molecular-weight polypeptides (<37 kDa), which enhanced emulsification, while scanning electron microscopy revealed porous structures aligned with hydration properties. Antioxidant activity was higher in albumin and glutelin, linked to surface hydrophobicity. LC-MS/MS identified 33 short-chain proteins, including oxidoreductase proteins and lipid-transfer proteins. Findings highlight marigold flower proteins as a sustainable, functional ingredient for a diverse range of food applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Relaxation and Aging of Nanosphere Assemblies at a Water–Oil Interface

The relaxation and aging of an assembly of spherical nanoparticles (NPs) at a water-oil interface are characterized in situ by grazing incidence X-ray photon correlation spectroscopy. The dynamics of the interfacial assembly is measured while the interface saturates with NPs. Weak attractions between NPs lead to gel-like structures in the assembly, where the in-plane ordering is inhibited by the broad size distribution of the NPs. Structural rearrangements on the length scale of the NP-NP center-to-center distances proceed by intermittent fluctuations instead of continuous cooperative motions. Here, the coexistence of rapid and slow NP populations is confirmed, as commonly observed in soft glass-forming materials. Dynamics are increasingly slowed as the NPs initially segregate to the locally clustered interface. The structural relaxation of the NPs in these localized clusters is 5 orders of magnitude slower than that of free particles in the bulk. When the interface is nearly saturated, the time for relaxation increases suddenly due to the onset of local jamming, and the dynamics slow exponentially afterward until the system reaches collective jamming by cooperative rearrangements. This investigation provides insights into structural relaxations near the glass transition and the evolution of the structure and dynamics of the assemblies as they transition from an isotropic liquid to a dense disordered film.

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

Residual Strain and Nanostructural Effects during Drying of Nanocellulose/Clay Nanosheet Hybrids: Synchrotron X-ray Scattering Results

Cellulose nanofibrils (CNF) with 2D silicate nanoplatelet reinforcement readily form multifunctional composites by vacuum-assisted self-assembly from hydrocolloidal mixtures. The final nanostructure is formed during drying. The crystalline nature of CNF and montmorillonite (MTM) made it possible to use synchrotron X-ray scattering (WAXS, SAXS) to monitor structural development during drying from water and from ethanol. Nanostructural changes in the CNF and MTM crystals were investigated. Changes in the out-of-plane orientation of CNF and MTM were determined. Residual drying strains previously predicted from theory were confirmed in both cellulose and MTM platelets due to capillary forces. The formation of tactoid platelet stacks could be followed. We propose that after filtration, the constituent nanoparticles in the swollen, solid gel already have a “fixed” location, although self-assembly and ordering processes take place during drying.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Nutrient Capture from Aqueous Waste and Photocontrolled Fertilizer Delivery to Tomato Plants Using Fe(III)–Polysaccharide Hydrogels

Inexpensive and sustainable methods are needed to reclaim nutrients from agricultural waste solutions for use as a fertilizer while decreasing nutrient runoff. Fe(III)–polysaccharide hydrogels are able to flocculate solids and absorb nutrients in liquid animal waste from Confined Animal Feeding Operations (CAFOs). Fe(III)–alginate beads absorbed 0.05 mg g –1 NH 4 + and NO 3 - from 100 ppm solutions at pH = 7, with > 80% phosphate uptake and ~30% uptake of ammonium and nitrate. Ammonium uptake from a raw manure solution (1420 ppm NH 4 + ) showed a significant 0.7 mg g –1 uptake. Tomato plant trials carried out with Fe(III)–alginate hydrogel beads in greenhouse conditions showed controlled nutrient delivery for the plants compared to fertilizer solution with the same nutrient content. Plants showed an uptake of Fe from the gel beads, and Fe(III)–alginate hydrogel beads promoted root growth of the plants. The plants treated with nutrient-loaded Fe(III)–alginate hydrogels yielded comparable tomato harvest to plants treated with the conventional fertilizer solution.

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

Increasing the Carbohydrate Output of Bamboo Using a Combinatorial Pretreatment

Bamboo represents a family of highly lignified biomass with significant resistance to cellulolytic enzyme degradation, and typically, a severe thermochemical pretreatment is needed to overcome its recalcitrance for producing fermentable sugars. Combinatorial pretreatments with a low holding temperature and low alkali dosage were investigated in this study in an attempt to remove the impediments to the accessibility of bamboo cellulose to enzymes and enable the efficient conversion of hemicellulose. Upon autohydrolysis at 180 °C, more than half of the hemicellulose (~58%) was solubilized, contributing to further delignification in the subsequent dilute alkali extraction (DAE). The solubilized hemicellulose mainly existed in the form of soluble xylan, which, after a novel endo-β-1,4-xylanase hydrolysis, generated a large amount of xylo-oligosaccharides with the xylobiose and xylotriose proportion reaching 72.99%. After the fractionation with combinatorial pretreatments, cellulose and xylose enzymatic hydrolysis yields were 73.36 and 86.98%, respectively, representing increments of 22.42 and 43.15% compared with the sole autohydrolysis process. Fluorescence microscopy (FM) and confocal Raman microscopy (CRM) images revealed that these dramatic improvements were caused by the deconstruction of the bamboo cell walls, including separation of the adjacent cell walls, removal of hemicellulose and lignin, migration and redistribution of lignin, and the increased exposure of cellulose. In addition, lignin chemical structure variations during the combinatorial pretreatment were analyzed with gel permeation chromatography (GPC), 2D HSQC NMR, and 31 P NMR, and the correlation between the lignin structure and enzymatic hydrolysis efficiency was investigated. In summary, this study highlighted the application of combinatorial pretreatments to maximize the carbohydrate output of bamboo and unveiled their mechanism that enabled the high-efficiency utilization of bamboo.

09 BIOMASS FUELS↗
DOE OSTI2020

Investigation of a Lignin-Based Deep Eutectic Solvent Using p -Hydroxybenzoic Acid for Efficient Woody Biomass Conversion

Deep eutectic solvents (DESs) are effective solvents for biomass conversion and have been proposed as alternatives to ionic liquids (ILs). In this paper, we first report an effective pretreatment of woody biomass using a novel hardwood lignin-based DES prepared from p -hydroxybenzoic acid (PB) and choline chloride (ChCl), which are used as the hydrogen bond donor and acceptor, respectively. The impacts of the ChCl-PB DES on structural properties and enzymatic hydrolysis of poplar wood were comprehensively evaluated. The performance of ChCl-PB DES was also compared with two other DESs with p -coumaric acid (PCA) and 4-hydroxybenzaldehyde (PHA) as the hydrogen bond donors, which have been successfully applied to herbaceous biomass conversion in previous studies. The results showed that hemicellulose and lignin were effectively fractionated during the proposed ChCl-PB DES pretreatment under a relatively mild temperature. The ChCl-PB DES pretreatment resulted in up to 69% of delignification, and the pretreated poplar residues had over 90% of glucose yield by a 72 h-enzymatic hydrolysis. Transformation of poplar biomass during the DES pretreatment was evaluated by gel permeation chromatography (GPC), two-dimensional heteronuclear single quantum coherence (2D-HSQC), and 31 P nuclear magnetic resonance (NMR) spectroscopies. The recovered lignin showed relatively high purity, narrow molecular weight distribution (PDI < 1.6), and relatively low molecular weight (~1400 g/mol for M w ). A sustainable process was achieved by recycling DES as well as the utilization of PB, which is a producible aromatic compound from hardwood lignin, for the proposed DES formation in the system. This study indicates that the proposed novel DES with a hardwood lignin-based PB compound is a promising pretreatment solvent to achieve an economically feasible biomass conversion process.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

CMPO-Functionalized Silica Sorbents for pH-Tunable Separation and Enrichment of Rare-Earth Elements from Environmental Matrices

Rare-earth elements (REEs) are crucial in many applications, yet mutual separation is challenging due to their similar chemical behavior. Octylphenyl- N,N-diisobutyl carbamoyl methyl phosphine oxide (CMPO) is an organophosphorus ligand originally developed for extracting actinides and lanthanides from spent nuclear fuel. Here, we report a pH-tunable CMPOfunctionalized silica sorbent for selective REE separation from complex aqueous matrices. A CMPO-associated silica gel sorbent was synthesized and characterized by Brunauer−Emmett−Teller (BET) surface area, scanning electron microscopy, and X-ray photoelectron spectroscopy to confirm the surface functionalization and binding behavior. Sorbent performance was evaluated by using a synthetic 46- element solution and a real phosphate rock fertilizer leachate. Notably, REEs were successfully eluted with ultrapure water, demonstrating reversible desorption controlled by pH adjustment. Packed-bed column studies increased the REE mass fraction from 3.6% to 64% (20-fold enrichment), with up to 30-fold enrichment of neodymium. The adsorption process follows the Langmuir isotherm behavior and follows pseudo-second-order kinetics. The uptake capacity of 1 μmol of REEs per 4.2 μmol of CMPO supports the formation of a predominantly 4:1 ligand:rare earth element(III) pseudocomplex. These results demonstrate CMPO-functionalized silica as a selective, water-elutable, and low-chemical-input platform for sustainable REE recovery from environmental and industrial sources.

chelating ligands↗
DOE OSTI2025

Hydrogel-Immobilized Multienzyme Systems for Cell-Free Chemical Bioproduction

Cell-free gene expression systems derived from bacterial lysates enable the expression of biosynthetic pathways from inexpensive and easily prepared DNA templates. These systems hold great promise for modular and on-demand bioproduction of valuable small molecules in resource-limited settings but are constrained in their long-term stability, reusability, and deployability. In this work, we demonstrate that multiple cell-free expressed enzymes can be co-immobilized in biocompatible hydrogels made from poly(ethylene glycol) diacrylate (PEGDA) with added glycerol for enhanced gel integrity. Using small-angle X-ray scattering (SAXS), we show that the mesh size of PEGDA-glycerol hydrogels is comparable to the globular sizes of many proteins and enzymes, which could be used for protein entrapment. We found that the combination between entrapment and chemical ligation of the enzymes was effective to retain proteins. By employing a method for direct fluorescence measurement from hydrogels, we found that proteins can be retained in PEGDA-glycerol for at least a week. By separating the cell-free enzyme expression from the immobilization step, we successfully fabricated enzyme-laden hydrogels with three heterologous cell-free enzymes for the bioconversion of pyruvic acid to malic acid, an industrially valuable and versatile precursor chemical. Both heterologous and endogenous enzymes from the lysate remain functional in photo-cross-linked hydrogels and can be reused for multiple biocatalytic cycles. Moreover, we also found that the immobilized enzymes exhibit up to 1.6-fold higher activity and 2-fold longer lifetimes than free enzymes in liquid reactions. Furthermore, these results could advance the deployment of cell-free synthetic biology because they show that reusable, stable, and durable multienzyme systems can be created using readily available materials and fabrication techniques.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Light-Mediated Synthesis and Reprocessing of Dynamic Bottlebrush Elastomers under Ambient Conditions

We introduce a novel grafting-through polymerization strategy to synthesize dynamic bottlebrush polymers and elastomers in one step using light to construct a disulfide-containing backbone. The key starting material—α-lipoic acid (LA)—is commercially available, inexpensive, and biocompatible. When installed on the chain end(s) of poly(dimethylsiloxane) (PDMS), the cyclic disulfide unit derived from LA polymerizes under ultraviolet (UV) light in ambient conditions. Significantly, no additives such as initiator, solvent, or catalyst are required for efficient gelation. Formulations that include bis-LA-functionalized cross-linker yield bottlebrush elastomers with high gel fractions (83–98%) and tunable, supersoft shear moduli in the ~20–200 kPa range. An added advantage of these materials is the dynamic disulfide bonds along each bottlebrush backbone, which allow for light-mediated self-healing and on-demand chemical degradation. These results highlight the potential of simple and scalable synthetic routes to generate unique bottlebrush polymers and elastomers based on PDMS.

36 MATERIALS SCIENCE↗
DOE OSTI2023

In Situ Imaging of Faujasite Surface Growth Reveals Unique Pathways of Zeolite Crystallization

Zeolite crystallization occurs by complex processes involving a variety of possible mechanisms. The sol gel media used to prepare zeolites leads to heterogeneous mixtures of solution and solid states with diverse solute species. At later stages of zeolite synthesis when growth occurs predominantly from solution, classical two-dimensional nucleation and spreading of layers on crystal surfaces via the addition of soluble species is the dominant pathway. At earlier stages, these processes occur in parallel with nonclassical pathways involving crystallization by particle attachment (CPA). The relative roles of solution- and solid-state species in zeolite crystallization have been a subject of debate. Here, in this work, we investigate the growth mechanism of a commercially relevant zeolite, faujasite (FAU). In situ atomic force microscopy (AFM) measurements reveal that supernatant solutions extracted from a conventional FAU synthesis at various times do not result in growth, indicating that FAU growth predominantly occurs from the solid state through a disorder-to-order transition of amorphous precursors. Elemental analysis shows that supernatant solutions are significantly more siliceous than both the original growth mixture and the FAU zeolite product; however, in situ AFM studies using a dilute clear solution with a lower Si/Al ratio revealed three-dimensional growth of surfaces that is distinct from layer-by-layer and CPA pathways. This unique mechanism of growth differs from those observed in studies of other zeolites. Given that relatively few zeolite frameworks have been the subject of mechanistic investigation by in situ techniques, these observations of FAU crystallization raise the question whether its growth pathway is characteristic of other zeolite structures.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Electrochemical Synthesis of Zeolite Coatings with Controlled Crystal Polymorphism and Self-Regulating Growth

Zeolite coatings are studied as molecular sieves for membrane separation, membrane reactors, and chemical sensor applications. They are also studied as anticorrosive films for metals and alloys, antimicrobial and hydrophobic films for heating, ventilation, and air conditioning, and dielectrics for semiconductor applications. Zeolite coatings are synthesized by hydrothermal, ionothermal, and dry-gel conversion approaches, which require high process temperatures and lengthy times (ranging from hours to days). Here, we report the first zeolite coatings synthesized via electrochemical deposition on a cathodic electrode, with controlled crystal polymorphism achieved within subhourly duration. We demonstrate this approach by developing sodium zeolite (e.g., sodalite (SOD), NaA (LTA), and Linde Type N (LTN)) coatings on a titanium electrode and extending the synthesis method to porous stainless steel. The coating morphology and crystallinity depend on the temperature, time, and applied current. The coating thickness is independent of the applied current, showing the presence of a self-regulating mechanism to ensure a uniform coating thickness across the metal surface. The electrochemical zeolite growth mechanism was elucidated with high-resolution transmission electron microscopy, and applications of the resultant zeolite coatings for oil/water separation and ethanol/water pervaporation were exploited. Electrochemical synthesis represents a novel, simple, fast, and environmentally friendly approach to preparing zeolite coatings. It can potentially be generalized for developing zeolite materials with diverse framework structures, morphologies, and orientations for substrates with complicated geometries.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Unveiling the Reactivity of Fluoropolymers with Sodium Metal: Mechanistic Insights and Battery Implications

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) has broad applications across various metal-ion battery systems, such as a binder for electrodes, a supporting matrix for electrolytes, and a separator material. Due to its excellent mechanical properties, PVDF-HFP has become an excellent candidate for fabricating gel and solid-state electrolytes in sodium-based batteries. However, in this study, we noticed notable side reactions occurring at the interface of PVDF-HFP membranes and Na metal. These reactions not only alter chemical compositions but also further affect the surface morphology and adhesive properties of membranes. Similar phenomena are observed in other polyfluoroalkyl-based membranes (PVDF and PTFE). Therefore, we systematically studied the reaction mechanisms between the Na metal and these polymers. The influence of different functional groups (−F, −CF 3 , −H) and their arrangement on the reaction extent has also been discussed. Finally, we concluded with the key factors driving these side reactions and provided new perspectives for designing polymers tailored for sodium-based batteries.

Interfacial side reactions↗
DOE OSTI2026

Highlighting the Importance of Authentic Reference Chemicals in the Unambiguous Identification of Unknowns during Routine Sample Analysis─An OPCW Proficiency Test Case

The unequivocal identification of unknown chemicals during routine sample analysis is a constant occurrence in the field of analytical chemistry. The process can be painstakingly tedious, particularly in situations where a tentatively identified unknown may possess isomeric counterparts yielding identical accurate mass values and very similar mass spectra. In this work, we present the experimental process involved in the correct identification of 1,4-oxathiane 4,4-dioxide and differentiation from its constitutional isomer, 2-hydroxyethyl vinyl sulfone, when present in a silica gel matrix featured in the 54th Environmental Organisation for the Prohibition of Chemical Weapons (OPCW) proficiency test. After discovering that the library-generated mass spectrum for 2-hydroxyethyl vinyl sulfone in a preliminary gas chromatography–mass spectrometry (GC-MS) analysis did not match the one from an authentic reference chemical, we embarked on an unknown structure determination campaign involving GC-MS, liquid chromatography-tandem mass spectrometry (LC-MS-MS), and nuclear magnetic resonance (NMR) spectroscopy. All of the information obtained, coupled to the synthesis of an authentic reference chemical, was used to determine the identity of the unknown as 1,4-oxathiane 4,4-dioxide. The process described in this work highlights the important role played by authentic reference chemicals in the identification of unknown chemicals during routine sample analysis.

Chemistry↗
DOE OSTI2024

p14 ARF forms meso-scale assemblies upon phase separation with NPM1

NPM1 is an abundant nucleolar chaperone that, in addition to facilitating ribosome biogenesis, contributes to nucleolar stress responses and tumor suppression through its regulation of the p14 Alternative Reading Frame tumor suppressor protein (p14 ARF ). Oncogenic stress induces p14 ARF to inhibit MDM2, stabilize p53 and arrest the cell cycle. Under non-stress conditions, NPM1 stabilizes p14 ARF in nucleoli, preventing its degradation and blocking p53 activation. However, the mechanisms underlying the regulation of p14 ARF by NPM1 are unclear because the structural features of the p14 ARF -NPM1 complex were elusive. Here we show that p14 ARF assembles into a gel-like meso-scale network upon phase separation with NPM1. This assembly is mediated by intermolecular contacts formed by hydrophobic residues in an α-helix and β-strands within a partially folded N-terminal portion of p14 ARF . These hydrophobic interactions promote phase separation with NPM1, enhance p14 ARF nucleolar partitioning, restrict NPM1 diffusion within condensates and nucleoli, and reduce cellular proliferation. Our structural analysis provides insights into the multifaceted chaperone function of NPM1 in nucleoli by mechanistically linking the nucleolar localization of p14 ARF to its partial folding and meso-scale assembly upon phase separation with NPM1.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

A blueprint for biomolecular condensation driven by bacterial microcompartment encapsulation peptides

Bacterial microcompartments are protein organelles with diverse metabolic capabilities. Their functional diversity is determined by an enzymatic core that is sequestered within a structurally conserved protein shell architecture. Segregation of protein cargo into the bacterial microcompartment is enabled by encapsulation peptides, which are short helical domains fused to core proteins through a disordered linker. Here, we investigate how encapsulation peptides drive multicomponent cargo assembly into biomolecular condensates. In vitro experiments supported by molecular dynamics simulations demonstrate the importance of both conserved hydrophobic packing and electrostatic interactions in stabilizing trimeric encapsulation peptide bundles. Topological rearrangements of encapsulation peptide domains can drive programmable liquid- or gel-like partitioning in vitro and in vivo. This partitioning is found to be encapsulation peptide-specific, modular, and can co-assemble at least three fluorescent reporters. In summary, we describe the molecular features necessary to drive biomolecular condensation using a widespread peptide tag. This work can serve as a blueprint for implementing encapsulation peptide biotechnology across diverse applications.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Spatially resolved nanostructural analysis of disordered phases in carbonated alkali-activated slag

Alkali-activated slag (AAS) is a promising low-CO 2 alternative cement consisting of several disordered phases of similar composition. Although their local atomic arrangements are known to influence macroscopic behavior, determination of structural changes in response to external stimuli remains a challenge. Here, X-ray diffraction-computed tomography (XRD-CT), pair distribution function-CT (PDF-CT), and nanoprobe X-ray fluorescence (nano-XRF) have been used to uncover how an increase of magnesium in AAS affects the atomic structure and spatial arrangement of phases after aggressive carbonation (100% dry CO 2 ), conditions experienced in applications such as oil and gas wells and geological storage of CO 2 . From PDF-CT it is found that a higher magnesium content decreases the average nanoscale crystallite size of disordered calcium carbonate. At the same time, higher magnesium content is correlated with a less decalcified C-(N)-A-S-H gel, as determined via analysis of Ca-Si atom-atom correlations from PDF-CT and Ca/Si ratios from nano-XRF. Finally, nano-XRF reveals that the disordered (i.e., amorphous) calcium carbonate is stabilized by the presence of silicates.

McCaslin, Eric R. [Princeton Univ., NJ (United Sta↗