A5021196205- Additive Manufacturing Materials and Processes
- Diamond and Carbon-based Materials Research
- Ion-surface interactions and analysis
- Welding Techniques and Residual Stresses
- Additive Manufacturing and 3D Printing Technologies
- Semiconductor materials and devices
- Laser Material Processing Techniques
- Nuclear Materials and Properties
- Advanced Electron Microscopy Techniques and Applications
- High Entropy Alloys Studies
- Electronic and Structural Properties of Oxides
- Advanced Surface Polishing Techniques
- Radioactive element chemistry and processing
- Electron and X-Ray Spectroscopy Techniques
- High-pressure geophysics and materials
- Force Microscopy Techniques and Applications
- Integrated Circuits and Semiconductor Failure Analysis
- Nuclear materials and radiation effects
- Advanced X-ray and CT Imaging
- Fluid Dynamics and Thin Films
- Silicon and Solar Cell Technologies
- Titanium Alloys Microstructure and Properties
- Metal and Thin Film Mechanics
- Laser-induced spectroscopy and plasma
- Magnesium Alloys: Properties and Applications
Lawrence Livermore National Laboratory
2015-2024
SUNY Polytechnic Institute
2019
University of Technology Sydney
2007-2017
University of Technology
2016
Universidad de Valladolid
2010
Abstract Laser powder bed fusion additive manufacturing is an emerging 3D printing technique for the fabrication of advanced metal components. Widespread adoption it and similar technologies hampered by poor understanding laser-metal interactions under such extreme thermal regimes. Here, we elucidate mechanism pore formation liquid-solid interface dynamics during typical laser conditions using in situ X-ray imaging multi-physics simulations. Pores are revealed to form changes scan velocity...
Circumventing spatter Laser powder bed fusion is an additive manufacturing technique that laser-melts layer by to build a three-dimensional (3D) part. Khairallah et al. used experiments and multiphysics model determine the origin of melt defect formation degrade properties built parts (see Perspective Polonsky Pollock). Informed modulation laser power important avoid disturbing creating shadowing. This reduces pore formations leads more uniform 3D-printed parts. Science , this issue p. 660 ;...
Advanced in situ characterization is essential for determining the underlying dynamics of laser-material interactions central to both laser welding and rapidly expanding field additive manufacturing. Traditional techniques leave a critical experimental gap understanding complex subsurface fluid flow metal evaporation inherent laser-induced heating metal. Herein, ultra-high-speed transmission X-ray imaging revealed be bridging this information gap, particularly via comparison with validation...
In situ X-ray-based measurements of the laser powder bed fusion (LPBF) additive manufacturing process produce unique data for model validation and improved understanding. Synchrotron X-ray imaging diffraction provide high resolution, bulk sensitive information with sufficient sampling rates to probe melt pool dynamics as well phase microstructure evolution. Here, we describe a laboratory-scale LPBF test designed accommodate experiments at synchrotron source during operation. We also present...
Abstract Laser powder bed fusion (LPBF) is a method of additive manufacturing characterized by the rapid scanning high powered laser over thin metallic to create single layer, which may then be built upon form larger structures. Much melting, resolidification, and subsequent cooling take place at much higher rates with thermal gradients than in traditional metallurgical processes, this occurring below surface. We have used situ speed X-ray diffraction extract subsurface following...
When tungsten is processed by laser powder bed fusion additive manufacturing, the combination of high residual stresses and tungsten's inherent ductile-to-brittle transition leads to a network microcracks. While preheating widely accepted as most efficient way reduce in additively manufactured parts, thus far it has proven ineffective completely eliminating microcracking tungsten. In addition preheating, changing alloy composition an increasingly popular approach circumvent cracking. This...
Laser powder bed fusion (LPBF) is a powerful tool for additive manufacturing (AM) of metal components. However, fabricating components with overhanging features using LPBF remains challenge. Overhangs suffer from dimensional inaccuracies, high surface roughness, and agglomerated material or dross. These parts often do not meet engineering requirements are discarded reprinted until met, redesigned to avoid overhangs. Printing flat overhang especially challenging due the long, unsupported that...
Laser powder bed fusion (LPBF) metal additive manufacturing provides distinct advantages for aerospace and biomedical applications. However, widespread industrial adoption is limited by a lack of confidence in part properties driven an incomplete understanding how unique process parameters relate to defect formation ultimately mechanical properties. To address that gap, high‐speed X‐ray imaging used probe subsurface melt pool dynamics void‐formation mechanisms inaccessible other monitoring...
Laser powder bed fusion (LPBF) additive manufacturing and laser welding are powerful metal processing techniques with broad applications in advanced sectors such as the biomedical aerospace industries. One common process variable that can tune laser-material interaction dynamics these two is adjustment of composition pressure atmosphere which conducted. While some physical mechanisms governed by ambient well known from literature, it remains unclear how extend to distinct conditions LPBF. In...
Detonation nanodiamond (DND) is known to form aggregates that significantly reduce their unique nanoscale properties and require postprocessing separate. How when DND an important question has not been answered experimentally could provide the foundation for approaches limit aggregation. To answer this question, time-resolved small-angle X-ray scattering was performed during detonation of high-explosives are expected condense particulates in diamond, graphite, liquid regions carbon phase...
Hydrogel infused additive manufacturing (HIAM) is an emerging technique for the of ceramics and metals. Distinct from slurry- or powder-based techniques, a hydrogel scaffold obtained in the...
Metal parts produced by laser powder bed fusion (LPBF) additive manufacturing exhibit characteristic microstructures comparable to those observed in welding. The primary cause of this microstructure is rapid, localized heating and cooling cycles, which result extreme thermal gradients where material solidification followed fast the solid state. final mechanical performance are also influenced pore formation caused melt pool fluid dynamics. Here, we use high speed, situ X-ray diffraction...
Abstract We present our recent development of an integrated mesoscale digital twin (DT) framework for relating processing conditions, microstructures, and mechanical responses additively manufactured (AM) metals. In particular, focusing on the laser powder bed fusion technique, we describe how individual modeling simulation capabilities are coupled to investigate control AM microstructural features at multiple length time scales. review prior case studies that demonstrate schemes, in which...
Controlled fabrication of semiconductor nanostructures is an essential step in engineering high performance photonic and optoelectronic devices. Diamond particular has recently attracted considerable attention as a promising platform for quantum technologies, photonics resolution sensing applications. Here we demonstrate the optically active, functional diamond structures using gas-mediated electron beam induced etching (EBIE). The technique achieves dry chemical at room temperature through...
We present a direct-write chemical technique for controlling the charge state of near-surface nitrogen vacancy centers (NVs) in diamond by surface fluorination. Fluorination H-terminated is realized electron beam stimulated desorption H2O presence NF3 and verified with environmental photoyield spectroscopy (EPYS) photoluminescence (PL) spectroscopy. PL spectra shallow NVs H- F-terminated nanodiamonds show expected dependence NV on their energetic position respect to Fermi-level. EPYS reveals...
Abstract In situ monitoring is required to improve the understanding and increase reliability of additive manufacturing methods such as laser powder bed fusion (LPBF). Current diagnostic for LPBF capture optical images, X-ray radiographs, or measure emission thermal acoustic signals from component. Herein, a methodology based on electrons - thermionic metal surface during proposed which can resolve laser-material interaction dynamics. The high sensitivity temperature morphology revealed...
We report the use of ammonia (NH(3)) vapor as a new precursor for nanoscale electron beam induced etching (EBIE) carbon, and an efficient imaging medium environmental scanning microscopy (ESEM). Etching is demonstrated using amorphous carbonaceous nanowires grown by deposition (EBID). It ascribed to carbon volatilization hydrogen radicals generated dissociation NH(3) adsorbates. The process also effective at preventing buildup residual hydrocarbon impurities that often compromise EBIE, EBID...
Models of adsorbate dissociation by energetic electrons are generalized to account for activated sticking and chemisorption, used simulate the rate kinetics electron beam induced chemical vapor deposition (EBID). The model predicts a novel temperature dependence caused thermal transitions from physisorbed chemisorbed states that govern coverage EBID rates at elevated temperatures. We verify these results experiments also show how can be deposit high purity materials characterize energy...
Abstract Recent advances in focused ion beam technology have enabled high-resolution, maskless nanofabrication using light ions. Studies with ions to date have, however, on milling of materials where sub-surface damage does not inhibit device performance. Here we report single crystal diamond a oxygen Material quality is assessed by Raman and luminescence analysis reveals that the layer generated can be removed non-intrusive post-processing methods such as localised electron induced chemical etching.
The rendering in the background shows a metal component being manufactured through laser powder bed fusion additive manufacturing. film strip contains frames from high-speed X-ray imaging revealing previously unseen void defect formation during build which furthers understanding of material properties and performance these components. Further details can be found article number 1900455 by Johanna Nelson Weker co-workers.