This paper introduces a novel formulation for simulating the condensation of magnesium (Mg) and aluminum (Al) particles from the vapor phase induced in solid material of these elements by laser welding. Our phase field model captures critical physical phenomena, including the extreme density difference between vapor and condensed phases, and the influence of the temperature gradient. Vapor concentrations and temperature boundary conditions are provided by a 2D melt pool model, simulating realistic manufacturing conditions. Although the current work focuses on a single-component system, the formulation is extendable to multicomponent systems. Qualitative comparisons with in situ laser melting experiments in an argon atmosphere demonstrate that the model accurately predicts very rapid condensation near the melt pool. Our findings offer an effective approach for non-isothermal vapor/liquid/solid phase transformations and provide an elegant method for incorporating thermodynamic free energy terms on a molar basis using the grand potential form.

Titanium electroreduction is desired for a variety of medical, electronic, and bonding applications but has not been possible until recently. Titanium electrodeposition with leveler and brightener additives in the deep eutectic solvent ethaline has been studied for effects on spectroscopic reflectance. Polymeric leveling agents and several small-molecule brighteners produce level/bright films (respectively) with high values for both specular and diffuse reflectance. The application of these leveling and brightening agents can produce films with appearances and surface roughnesses that may be suitable for application in medical implants such as stents, corrosion protection of electronics for wearable technology, and as interlayers between dissimilar metals.

Control of multicomponent alloys during welding is challenging because it lacks a real-time understanding of composition. The optical emissions of plasma formed during laser-induced metal welding correlate with the composition of particles ejected from the melt pool. Plasma emissions observed in this study contain large iron, manganese, chrome, and copper signatures, which match the composition of emitted particles. Particles recovered closest to the melt pool exhibit a core-shell morphology that is composed of iron-manganese-chrome intermetallic cores within copper shells. Particles collected farther from the melt pool, do not share this core-shell morphology, though similar elemental compositions are observed. The correlation between plasma optical emissions and particle composition can be used to predict the composition of the melt pool, allowing for real-time welding and sintering control. This work presents an initial look at correlating the optical emissions of the weld plasma to that of the composition of particles condesned from the plasma plume. Particles removed from the melt pool through the plasma plume have atomic percent level differences in composition of alloy elements when compared to the originating metal.image (c) 2024 WILEY-VCH GmbH

The dynamic realm of laser absorption in materials is not yet fully understood because the amount of energy absorbed by metal surfaces is not well characterized. Previous studies of the absorptivity of metals during industrial laser welding have indicated some dependence on surface roughness and plume obstruction. No prior experimental data exist for commercially available stainless steel 316 (316SS). This work presents a new dataset of the effective absorptivity of 316SS as a function of pulse width and surface roughness at 108 W using calorimetry. Experimental data indicate that 316SS with a surface roughness greater than half of the wavelength of the laser—1064 nm in this study—absorbs more energy. The effective absorptivity at laser pulses longer than 3 ms has a low confidence due to obfuscation of the laser after plume formation.

Particulate mass estimation from 3-pixel images is desirable in many fields. Red–green–blue (RGB) analysis and Boolean logic were shown to estimate the mass of luminescent tracers in microscopic images. With a controlled background intensity, an estimation error of 1.8 to 3.5

Condensate ring formation can be used as a benchmark in welding processes to assess the efficiency and quality of the weld. Condensate formation is critical as the resulting condensate settles into the powder thereby altering the quality of unconsolidated powder. This study investigates the intricate relationship between alloy composition, vapor pressure, and condensate ring thickness as seen in a two-dimensional micrograph. To study the process, laser spot welding was performed on 9 different alloys, and the inner spot weld diameter along with the condensate ring formation was studied. Leveraging machine learning models, experimental observations, and molecular dynamics simulations, we explore the fundamental factors governing condensate ring formation. The models, adept at predicting weld spot diameter and condensate ring thickness, identify laser power as a primary determinant for weld spot diameter followed by physical properties like hardness and density. Conversely, for condensate ring thickness, vapor pressure and melting point descriptors consistently emerge as paramount, as validated across all models. Molecular dynamics simulations on Ni-Cr alloys elucidate the vaporization dynamics, confirming the role of vapor pressure in governing surface vaporization. Our findings underscore the pivotal influence of vapor pressure and melting point descriptors in condensate ring formation. The convergence of machine learning predictions and simulation insights elucidates the dominance of these descriptors, offering crucial insights into alloy design strategies to minimize condensate ring formation in laser welding processes.

Volatile radioisotopes represent a substantial health risk when released into the environment. To better understand the environmental fate of radioisotopes, the authors constructed a cylindrical steel-walled chamber to simulate the atmospheric processing of volatile radioactive gases. Optical modeling was performed for the properties of simulated sunlight in the chamber to better characterize atmospheric reaction studies. Optical simulations were performed using two wall materials (steel and thin-film silica) and validated against experimental measurements. This optical analysis methodology can be used to improve the fidelity of atmospheric models by accounting for optical inhomogeneities enabling a firmer grasp of radioisotopes’ environmental fate. Graphical abstract

Three tasks were proposed for this work. All three were completed. The tasks were as follows: Task 1: A larger plating system will be purchased for process scale-up. TiF3 will be tested as the metal precursor in an effort to reduce water sensitivity of the process. Task 2: Ti on steel samples will be created at PNNL and shipped to Atlas Technologies. Atlas Technologies will diffusion bond the samples to aluminum and test the bond strength. The results will be reported to PNNL. Task 3: Investigation into DOE mission relevant Ti and Zr alloys and demonstration on larger scale work pieces.

Journal Article Towards On-the-Fly Feedback Loops for Direct Energy Deposition Systems Get access Matthew Olszta, Matthew Olszta Pacific Northwest National Laboratory, Richland, WA, United States Search for other works by this author on: Oxford Academic Google Scholar Lance Hubbard, Lance Hubbard Pacific Northwest National Laboratory, Richland, WA, United States Search for other works by this author on: Oxford Academic Google Scholar Nicole Overman, Nicole Overman Pacific Northwest National Laboratory, Richland, WA, United States Search for other works by this author on: Oxford Academic Google Scholar Floyd Hilty, Floyd Hilty Pacific Northwest National Laboratory, Richland, WA, United States Search for other works by this author on: Oxford Academic Google Scholar Ankit Roy, Ankit Roy Pacific Northwest National Laboratory, Richland, WA, United States Search for other works by this author on: Oxford Academic Google Scholar Shawn Riechers Shawn Riechers Pacific Northwest National Laboratory, Richland, WA, United States Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 29, Issue Supplement_1, 1 August 2023, Page 85, https://doi.org/10.1093/micmic/ozad067.034 Published: 22 July 2023

Radioisotopes and hazardous gases can have undetermined environmental pathways. Researchers at Pacific Northwest National Laboratory constructed a chamber that complies with the requirements needed for an atmospheric reaction platform and the safety principles of interacting with hazardous dispersible sources to enable the environmental testing of these gases. Initial dynamic testing showed inter-chamber mixing completed from minutes to 1.5 h. The photooxidation of butyl iodine showed the presence of signals from reaction products and intermediaries for up to 50 h. Current detection limits of the chamber and analytical collection and testing approach were shown to be in the single-digit parts per billion levels. The comparisons between the measured oxidation trends and literature show the utility of performing laboratory experiments to validate the results of modeling for larger-scale scenarios. Researchers at Pacific Northwest National Laboratory constructed and tested an atmospheric chamber that begins to demonstrate the utility of such a chamber design for the study of the atmospheric fate of especially hazardous and radioactive gases.

To explore particulate movement near the plasma of chemical explosions, rugged tracer particles were placed within and on the exterior of metal charges and electrically detonated. The particles were collected on/in the porous walls of plastic cylinders at diameters that correlated to the plasma width during different phases of the explosion. The particles’ positions were determined by Boolean logic analysis of their luminescent intensity. The cylinders which caught particles from the initial phases of the explosion retained placement information, while wider cylinders showed uniform mixing. These results/analysis methodology can help improve the understanding of particulate mixing in harsh environments. Graphical abstract

Tracking mass through harsh environments requires surrogate particles that withstand the event and endure until sampling. Silica-covered quantum dots have been shown to withstand a range of environmental pHs from months to years; in this work they are shown to endure in anticipated local environments. Two methods of particle synthesis were employed to produce luminescent silica with particle diameters 0.1–4 μm. These tracer particles scale for mass production, tolerate harsh environments, and endure in debris. They could be deployed in places such as chemical explosions, industrial processes, geologic test beds, oil and gas fields, nuclear reactors, and geothermal plants to track mass under harsh conditions. Graphical abstract

The near real-time detection of airborne particles-of-interest is needed for avoiding current/future threats. The incorporation of imprinted particles into a micelle-based electrochemical cell produced a signal when brought into contact with particle analytes (such as SARS-COV-2), previously imprinted onto the structure. Nanoamp scales of signals were generated from what may’ve been individual virus-micelle interactions. The system showed selectivity when tested against similar size and morphology particles. The technology was compatible with airborne aerosol sampling techniques. Overall, the application of imprinted micelle technology could provide near real-time detection methods to a host of possible analytes of interest in the field.

Experiments were conducted to investigate a passive production mechanism for the world’s most energy intensive commodity, ammonia. A novel method, gamma catalyzed ammonia production at ambient conditions, was investigated. Ammonia is currently produced through the highly energy intensive Haber-Fritz process, which requires an operation pressure of 400 atmosphere and 600 degrees Celsius. Due to the high demand and need for ammonia, the Haber-Bosch process consumes 25% all energy produced globally. Reported herein was an attempt to produce ammonia at ambient temperature (20 C) and ambient pressure (1 atm), through a novel process developed at PNNL, gamma driven catalysis of ammonia. Although the measurements of the ammonia production suggest wild success, reports in the literature by Gao et.al. suggest an experimental positive bias in the results. To rule out the potential positive bias, multiple additional production campaigns would be needed to with an alternate analysis technique such as ion chromatography, as suggested by Gao et.al. Unfortunately, due to this late determination of potential positive bias, the results of this study remain inconclusive to the feasibility of gamma driven catalysis of ammonia and more work is needed to describe the chemical evolution with time. The results are a first step and demonstrate that gamma-catalyst mediated reactions are possible. This represents a key opportunity to explore the fundamental chemistry of high band gap catalysts that can change the paradigm of radiation, transforming it from a waste to a valuable energy source.

The near real-time detection of airborne particles-of-interest is needed for avoiding current/future threats. The incorporation of imprinted particles into a micelle-based electrochemical cell produced a signal when brought into contact with particle analytes (such as SARS-COV-2), previously imprinted onto the structure. Nanoamp scales of signals were generated from what may’ve been individual virus-micelle interactions. The system showed selectivity when tested against similar size and morphology particles. The technology was compatible with airborne aerosol sampling techniques. Overall, the application of imprinted micelle technology could provide near real-time detection methods to a host of possible analytes of interest in the field.