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DOE OSTI2024

Synthesis and Functionalization of Coal Fly Ash-Derived Zeolites for Boron Removal From Wastewater

There are hundreds of both active and unused surface impoundments in the United States containing coal combustion residuals (CCRs) produced by coal-fired power plants which can leach toxic elements into surface and groundwater. Therefore, the development of efficient means for both the clean-up of surface impoundments and for deriving economically viable products from CCRs are urgent tasks for researchers. Herein, a microwave-assisted strategy is presented for converting a common coal combustion residual, coal fly ash (CFA), into zeolite-based sorbents for boron (B) removal from wastewater. Specifically, CFA constitutes the main source of Si and Al ions to produce zeolite type-A and the resulting sorbent subsequently undergoes simple cation exchange with Ca to enhance its B adsorption capacity. Structure and composition of the sorbents were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), inductively coupled plasma (ICP)-mass spectrometry (MS), and ICP-optical emission spectroscopy (OES). The Ca-modified zeolite sorbent derived from CFA exhibits comparable B removal capacity with similar commercial zeolites.

Muldoon, Patrick↗

DOE OSTI2024

Trace Element Control in Master Alloys and Impact of Feedstock Purity on a Ta-containing Steel during Electroslag Remelting

Advanced materials design often leads to new complex compositions that can bring challenges to manufacturing processes. Melt processing of a novel alloy with a tight chemistry range revealed a 25% Ta loss after manufacturing. Vacuum induction melting (VIM) and electroslag remelting (ESR) were performed using industry practices at a laboratory scale and the loss occurred from the VIM electrode to the ESR ingot. Several tools were used for characterization, including combustion analysis, scanning electron microscopy, and electron probe microanalysis for observation of the precipitate and inclusion phases. Additionally, computational modeling of the ESR process was performed to predict macrosegregation and inclusion travel. It was found that a significant amount of Ta2O5 inclusions formed during VIM and were transferred to the slag during ESR. This led to a 95% decrease in density of inclusions explaining to Ta loss. Pathways to better control advanced alloy chemistries during melt processing will be discussed.

Detrois, Martin↗

DOE OSTI2023

Low-Power Nuclear Heating Tests of UN Fuel Particles in Hydrogen Environment for Nuclear Thermal Propulsion

Recently, there has been a reemergence of interest within the space-exploration community regarding nuclear thermal propulsion (NTP) for interplanetary travel. NTP, as conceptualized, is a compact propulsion source, is relatively light because there is no need for an oxidizing agent and has a very high specific impulse compared to traditional forms of propulsion. These factors would reduce first-leg orbital-rocketry costs (by the source’s low weight and volume) and decrease overall travel time for astronauts with higher transit speeds. Idaho National Laboratory was provided bare, uncoated, and tungsten-coated uranium nitride fuel particles as part of a preliminary investigation. The fuel was fabricated by BWX Technologies and irradiated at the Massachusetts Institute of Technology research reactor. X-ray computed tomography and scanning electron microscopy and associated chemical analysis techniques were performed on these particles at Idaho National Laboratory. Both coated and uncoated forms were examined in the as-fabricated and as-irradiated conditions. The tungsten coating was found to be intact following the irradiation, indicating positive attributes for performance under these low-power-irradiation conditions. The irradiation of uncoated particles resulted in nitrogen enrichment at the edge of the particle.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2024

Embedded High-Temperature Sensors: Enhancing Thermoelectrical Performance with Refractory Composites Gradient Layers

To monitor the stability of various energy and manufacturing systems, sensors capable of operating at temperatures exceeding 1000 °C in diverse environments for extended durations are essential. However, under harsh conditions, degradation of sensing materials is a concern that can be controlled by embedding the sensors into refractory oxides. Doped-LaCrO3 based composites are excellent candidates for high-temperature sensing applications due to their good thermoelectrical properties. However, chemical reactivity between the conductive phase and the refractory oxides can decrease the performance of the sensors. In this work, it was devised gradient-type protective layers safeguarding conductive phases within embedded thermocouples, which were fabricated and characterized by X-Ray Diffraction for phase development analysis, Scanning Electron Microscopy and Energy-dispersive X-ray spectroscopy for microstructure and cationic interdiffusion kinetics, long-term thermoelectric testing was completed up to 1400 °C. The enhanced performance of these novel sensors addresses a critical limitation, rendering them viable for long-term high-temperature applications.

20 FOSSIL-FUELED POWER PLANTS↗

DOE OSTI2024

Iodine Capture Studies of Silver Mordenite and Novel Alternative Metal Sorbents

Radioiodine is one of the radionuclides of concern when considering reprocessing of used nuclear fuel (UNF). It is expected to be released primarily in the dissolver off-gas (DOG) stream. Sorbents that target I 2 removal from a UNF processing off gas must perform efficiently under elevated temperatures in the presence of water vapor and nitrogen oxide gasses (NOx). Many studies have been conducted that examine the adsorption of iodine species in the presence of NOx gases through reduced silver-exchanged mordenite (Ag 0 Z), a zeolite mineral. This study characterizes the effects of iodine, water vapor, and nitrogen dioxide on the adsorption of I 2 by Ag 0 Z at lower temperatures suitable for comparison with novel Cu- and Bi- bearing sorbents which offer a non-RCRA alternative. When exposed to ‘harsh’ conditions such as I 2 , H 2 O, and NO 2 vapors carried by air, Cu 2 S-polyacrylonitrile (PAN) is more efficient than Ag 0 Z and all other novel sorbents, providing with 11% I capture efficiency. However, under ‘ideal’ conditions in which I 2 is carried by dry air), Ag 0 Z is more efficient than Cu 2 S-PAN and other novel sorbents, providing 74% I capture efficiency. To investigate this result and the overall performance of all sorbents tested, several characterization techniques were employed, including thermal gravimetric analysis, scanning electron microscopy – electron dispersion X-Ray spectroscopy, powder X-ray diffraction, and X-ray photoelectron spectroscopy. These techniques are discussed within this report. This document also includes a design and test plan update from Idaho National Laboratory as the next step in testing the high performing sorbents from thin-bed tests carried out by Oak Ridge National Laboratory.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2024

Understanding and controlling water-organic co-transport in amorphous microporous materials

The transport of molecules in microporous material is a significant and active area of research in separation applications. The movement of vapor/liquid molecules in a high-loading condition in microporous spaces is especially challenging to interrogate. This project aims to understand and control the transport of complex water and organic solvent mixtures in varying structures of microporous carbon molecular sieve (CMS) and activated carbon membranes. Modeling of transport behavior in such carbonaceous samples using computational modeling is difficult due to their amorphous structure. Therefore, this research intends to study the transport mechanism of water-organic mixtures by experimentally revealing fundamental transport properties, such as guest sorption amounts as well as diffusion and permeation rates. Considering the different size and guest-host affinity of water and organic solvent molecules, the objective of this research is to understand the structural conditions within the ultramicropores and micropores that generate different types of molecular transport and selection mechanisms within such complex systems. Carbonaceous materials are developed using tailored pyrolysis techniques to pyrolyze polymeric precursors, including polyvinylidene chloride (PVDC),polyvinylidene fluoride (PVDF), polymer of intrinsic microporosity (PIM) -1, and fully aromatic polyamide. The initial stage of the research will focus on the microscopic diffusion and sorption studies of pure component water, xylene isomers, and n,n- dimethylformamide within various carbons. Additional structural investigation on CMS, such as gas physisorption and neutron scattering studies, will be executed to gain deeper insight into these structure-transport relationships. Scanning electron microscopy and X-ray photoelectron microscopy are also used to further characterize these materials. The research will progress to probe mutual diffusion of complex water-organic mixtures within various CMS microstructures. Competitive sorption and permeation studies of the binary mixtures in different microstructural CMS will be followed. The obtained binary mixture transport parameters were used to predict binary water-organic mixtures transport.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Characterizing cobalt sequestration in manganese-rich coal mine drainage treatment solids

This study investigates Co adsorption on synthesized birnessites over a wide pH range and in sulfate-rich solution to simulate CMD treatment conditions. Langmuir and Freundlich adsorption isotherms of Co at pH values of 3.5, 4.5, and 6.5 at 25°C onto Na-and H-birnessite were generated. Cobalt concentrations in supernatants were determined by ICP-MS and chelation ion chromatography. Mineralogy and morphology of pre- and post-adsorption experiment solids characterization by X-ray diffraction and scanning electron microscopy will be presented. These experiments suggest that cobalt sulfate complexes and pH of CMD, as well as the Mn-oxide mineral structures present in treatment beds, will impact cobalt adsorption in CMD solids, and can be used as calibration points for equilibrium and kinetic modeling approaches that are critical for developing effective and implementable remediation processes and to better inform future Co recovery efforts from CMD solids.

Schaffer, Camille↗

DOE OSTI2025

Fundamental Study of Fatigue Crack Initiation at Grain and Twin Boundaries in Austentic Stainless Steel (Final Technical Report)

The overarching goal of this project was to understand the dislocation-based mechanisms driving fatigue crack initiation at grain and twin boundaries. The hypothesis of the work is that dislocation structures equivalent to persistent slip bands (PSBs) form in the boundaries, leading to local stress concentrations and fatigue crack initiation. The sub-goals associated with this work include: • Understanding the evolution of the dynamic stress state and dislocation density surrounding PSB/grain boundary interactions. This will require the development of new techniques that couple high resolution electron backscatter diffraction (HREBSD) with in situ scanning electron microscopy (SEM) deformation. • Uncover the mechanisms by which dislocations are accommodated in grain and twin boundaries during fatigue. The proposed approach here is to conduct in situ transmission electron microscopy (TEM) deformation experiments on fatigued samples. • Establish correlations between microstructure, deformation accommodation, and crack initiation across time and length scales. This work primarily focuses on understanding fatigue crack initiation in austenitic stainless steels, though promising work by an undergraduate researcher extended the work to high purity Al.

42 ENGINEERING↗

DOE OSTI2025

Characterization of Build Parameters and Microstructure in Low Heat Input WAAM of Ni-Based Superalloy Haynes 282

Ni-based superalloy Haynes® 282® is being targeted for various applications in advanced power generation systems for its superior fabricability, weldability, and excellent high temperature creep and corrosion performance. This process optimization study aims to use a low heat-input, high deposition rate, controlled Gas Metal Arc Welding (GMAW) process, Cold Metal Transfer (CMT) by Fronius, attempting to achieve fully dense fabrication and possibly avoid the need for HIP. Twenty-one multilayer blocks (~25x100x40 mm3) were deposited to explore a large set of build parameters variations that focused on varying the travel speed from 14 to 42 inches per minute (ipm) and wire feed speed from 150 to 450 ipm. A strong correlation has been observed between arc energy – controlled primarily by travel and wire feed speed. Initial visual inspection, internal microstructural examination, and computed tomography (CT) have been used to determine the effects of built parameters on evolution of internal porosity and defects. Scanning electron microscopy techniques enabled structural and compositional imaging of heterogeneity and changes in microstructural properties.

additive manufacturing↗

DOE OSTI2024

Scale-Up of Lithium Iron & Aluminum Nickelate Advanced Cathode and Fabrication of A Battery Pack Comprising The Same

Global battery manufacturers are increasingly worried about the serious supply chain constraint caused by rapid fluctuations in cobalt prices over the years. We present a novel cobalt-free, nickel-rich layered cathode material called NFA class (LiNixFeyAlzO2) to tackle this challenge. Spherical NFA(OH)2 precursors were successfully synthesized by incorporating Ni, Fe, and Al elements using a co-precipitation reaction in a continuous stirred tank reactor. The LiNFAO2 cathode, composed of LiNi0.85Fe0.05Al0.1O2, was synthesized and analyzed using X-Ray diffraction, Mössbauer spectroscopy, and scanning electron microscopy (SEM). The material's electrochemical behavior was evaluated through various techniques at different lithiation/delithiation states in two voltage ranges. The cobalt-free material exhibits a high capacity of 190 mAh/g at 0.1C within the voltage range of 3V-4.5V, as demonstrated by electrochemical performance evaluations. Rate and cycling evaluations showed good rate capability and cycling stability, with 88% capacity retention after 100 cycles at C/3 within the voltage range of 3V-4.3V. Our research shows the great potential of cobalt-free NFA cathodes as a feasible option for developing cost-effective lithium-ion batteries.

25 ENERGY STORAGE↗

DOE OSTI2025

Characterization of Build Parameters and Microstructure in Low Heat Input WAAM of Ni-Based Superalloy Haynes 282

additive manufacturing↗

DOE OSTI2025

Improving Stability of an Optical Fiber pH Sensor with a Calcined Polyethylenimine-Coating at High Pressures and Temperatures

With an increased interest in subsurface gas storage technology for various energy applications, monitoring wellbore structural stability and subsurface geochemistry has become more pressing, and pH is a key parameter to measure. As high pressure and elevated temperatures in subsurface conditions are comparatively harsh relative to that expected for most standard pH sensor designs, any pH monitoring hardware must be designed for extended exposure to high pressures and temperatures. We previously reported that an optical fiber pH sensor functionalized with a calcined polyethylenimine coating had shown some promise as a high temperature and pressure pH sensor but with some drifting when operating for longer than 8 hours. In this paper, we investigated the coating composition and potential cause of the drifting and improved the stability of the prepared coating to minimize sensor drift under simulated wellbore conditions. Scanning electron microscopy (SEM) had previously shown moderate cracking at high pressures over short tests. By applying X-ray photoelectron spectroscopy (XPS) to characterize the sensor coating before and after one week of testing in an H2/CH4 gas blend at 80 °C and 900 psi, a compositional change in the coating was observable, which may indicate susceptibility to alteration by subsurface gas storage conditions. Non-reducing (CH4, N2) environments were also tested, and confirmed that both temperature and pressure were also contributing to the drift.

energy infrastructure↗

DOE OSTI2022

Data Mining – Image Analysis of Radiography for Zr Redistribution

The research effort described in this report represents a first attempt to investigate the radial redistribution of Zr in ternary fuel alloys U-xPu-10Zr (x = 0, 8, 19) irradiated in the in-reactor fuel experiments during the operation of the U.S. Department of Energy’s (DOE’s) Experimental Breeder Reactor II (EBR-II) at Idaho National Laboratory (INL) using methods of image processing on post-irradiation neutron radiographs. Approximately 130,000 metal fuel pins were irradiated in EBR-II during its 30 years of operation to develop and characterize existing and prospective fuels. For many of the metal fuel irradiation experiments, neutron radiography imaging was performed historically now allowing application of modern image analysis techniques to characterize fuel behavior, such as fuel swelling, fluff formation, and now, fuel alloy constituent redistribution. The redistribution of fuel components depends on the temperature field, radially, within the fuel. Specifically, Zr is expected to redistribute radially towards the center of the pin, as well as towards the outer zones. Currently, direct imaging of a pin cross-section through optical methods or scanning electron microscopy (SEM) is used to study the constituents’ redistribution, which is very time-consuming and can only be applied to a limited number of pins. An automated image processing technique allowing for the investigation of fuel radial redistribution zones would significantly accelerate data analysis. In general, if the fuel temperature is hot enough, three redistribution zones are expected, corresponding to the main fuel components (e.g., U, Pu, Zr). While more assessment will be performed in fiscal year (FY)-2023, it seems possible to differentiate the pins according to their fuel composition using image analysis techniques on neutron radiographs of metallic fuel pins based on the analysis to date.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2025

Micro-Mechanically Guided High-Throughput Alloy Design Exploration Towards Metastability-Induced H Embrittlement Resistance

We develop a high-throughput approach for studying H embrittlement (HE)-resistance in alloys, which is based on combinatorial compositional screening of metastability effects by in situ scanning electron microscopy H-analyses. The project objective included: (i) technique development of high-throughput screening (HTS) for HE-resistance, (ii) discovery of new metallic materials with superior HE-resistance, (iii) Multiscale verification of HE-resistance of the new alloys and H-barrier layers, from atomic scale to an engineering scale. The investigation focused on a model system that enables exploration of different metastable states in Fe-based complex-concentrated alloys. Composition spread islands with hundreds of varying compositions are fabricated on a single substrate using a combinatorial co-sputtering technique. To screen these alloys, we developed and employed a home-built SEM-based integrated analysis system capable of characterizing H-permeability, H-trapping, H-influence on mechanical properties, and other material properties, as well as atomistic to continuum simulations to study the underlying physics.

08 HYDROGEN↗

DOE OSTI2024

Scale-Up of Lithium Iron & Aluminum Nickelate Advanced Cathode and Fabrication of A Battery Pack Comprising The Same

25 ENERGY STORAGE↗

DOE OSTI2025

Investigation of Undissolved Solids from Salt Waste Processing Facility (SWPF) Salt Batches Collected via Filtration

SRNL researchers performed six experiments wherein 0.1 μm-grade stainless steel filters were used to filter samples pulled from salt batches 6, 9B, and 11B, without the addition of monosodium titanate. Three of these experiments were performed to collect filterable solids from each salt batch and characterize trapped solids via scanning electron microscopy. The remaining three experiments were performed to collect and then dissolve the same solids using 3.5 M nitric acid (similar to that employed in the Salt Waste Processing Facility) for characterization via Inductively-coupled plasma atomic emission spectroscopy.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2025

Wafer-Free Crystalline Silicon Solar Cells (CRADA Final Report)

This CRADA project, based on the DOE Solar Energy Technologies Office (SETO) Solar Prize Voucher program, helped Leap Photovoltaics to develop methodologies to immobilize Si particles by permanently attaching them to an Al-coated substrate and thereby forming carrier-selective electrical contacts to the Si particles. The bigger goal was to help Leap Photovoltaics develop these immobilized and contacted particle arrays into relatively efficient, inexpensive, and industrially relevant solar cells. By using Si particles instead of wafers in a solar cell absorber layer, one can avoid costs associated with growing monocrystalline Si ingots, then diamond-sawing them into wafers, then processing wafers into cells – a mainstream practice in today's high-efficiency Si cell and module technology. Monocrystalline or polycrystalline Si particles can be obtained in various ways: for example, Si kerf from wafer sawing is monocrystalline; recycled Si cell wafers can be ball-milled into particles; particles can be grown using various gas-phase techniques (mostly from SiH4). These Si particles can be assembled onto a substrate and serve as an absorber layer for the solar cell, absorbing photons to generate photocarriers. The challenge with this technique is to collect photocarriers from individual Si particles, with separation of photogenerated electrons to the negative cell’s electrode and positive photogenerated holes to the positive electrode. Therefore, each particle must have two isolated, carrier-selective contacts: one for electrons and one for holes. Plus, particles need to be immobilized onto a solid substrate. The goal of this work was focused on the immobilization of Si particles and creating hole-selective contact to them at the same time, using industrially relevant Si photovoltaic (PV) cell technology: screen printing of Al back-surface field electrodes. This is used in the mainstream Propane Education and Research Council (PERC) technology for hole-collecting contacts at the back of the cell. The work performed at NREL consisted of screen printing of Al metal paste on substrates, spreading Si particles onto it, and thermally processing the structures to form hole-collecting contacts. The final structures were investigated by scanning electron microscopy (SEM) after focused ion beam (FIB) cross-sectioning and polishing. The work was done jointly by NREL staff and Leap Photovoltaics (Leap PV) employees stationed at NREL. The samples were then taken to Leap PV for further processing. Training the Leap PV employee on various NREL techniques (laser cutting, screen printing, thermal processing, characterization) was part of the scope.

14 SOLAR ENERGY↗

DOE OSTI2025

Dissimilar metal joining of Ti-6Al-4V and Inconel 625

The dissimilar joining of Ti-6Al-4V and Inconel 625 by using a suitable interlayer shows potential design flexibility by avoiding the brittle intermetallic phases from direct welding. These phases include NiTi , NiTi 2 , and Ni 3 Ti . The objective of this work is to facilitate laser welding of Ti-6Al-4V and Inconel 625 through a vanadium interlayer to form an intermetallic free, strong, and corrosion resistant joint. Vanadium was chosen based on binary phase diagram solubilities, literature, and theoretical CalPhaD calculations in PanDat. Laser welding was systematically explored from based on beam mode, offset, power, and scan speed. Varied parameters include laser power from 325 to 650 watts, laser scan speed from 80 to 160 in/min, and beam offset up to a ¼ of the beam diameter. Parameters were chosen based on previous dissimilar joining research and those found in the literature. Metallography, including optical and scanning electron microscopy, was used to analyze the weld chemical composition, grain structure, and defects through both the fusion and heat affected zones. The results and discussion will examine the relationship between process parameters, microstructure, and observed weld defects. Our findings will not only assess the weldability of vanadium and Inconel 625 but also establish a transferable framework for studying other dissimilar material combinations, providing valuable insights for future research in this field.

36 MATERIALS SCIENCE↗