Search NASA⌕ Search

SEARCH · Search NASA

Results for “PLA”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Design and scale-up of 3D printed bat houses with biomass-derived polymer composites

Biomass (e.g., pine sawdust, especially high–ash content pine sawdust) is commonly disposed of as waste. Combining biomass with polymers to make composite feedstocks for 3D printing has been explored as a method to reduce or repurpose the biomass waste. Although not all biocomposite properties are known, the wood-based polylactic acid (PLA) composite has promising qualities for applications in ecological settings. In this work, pine wood–PLA composite feedstock was used to 3D print supplemental roost structures for endangered tree-roosting bats, which often face a paucity of suitable naturally occurring roosts. This material combination was selected because it is estimated to degrade faster than the synthetic material systems that are used widely in supplemental bat roosting structures to aid in the conservation of tree roosting bats. The layered, rough surface created by the 3D printing process serves as a surface that bats can grip while roosting. Computer-aided design (CAD) models were generated based on natural roost structures, and a full-size bat house was successfully additively manufactured using a pellet-fed large-scale 3D printing system. The 3D printed hexagon exhibited a tensile strength of 22–23 MPa and a Young’s modulus of 3202–3218 MPa in the x-direction. It has been demonstrated that the 3D printed bat house can be installed on a tree in a stable fashion. This successful demonstration of a bat roost manufactured using a bioderived composite should promote its use in other fish and wildlife structures and broader industrial applications such as construction and automobiles.

3D printing↗
DOE OSTI2023

Microstructure and defect engineering of graphite anodes by pulsed laser annealing for enhanced performance of lithium-ion batteries

We report nanosecond pulsed laser annealing significantly improves cyclability and current carrying capacity of lithium-ion batteries (LIBs). This improvement is achieved by engineering of microstructure and defect contents present in graphite in a controlled way by using pulsed laser annealing (PLA) to increase the number density of Li + ion trapping sites. The PLA treatment causes the following changes: (1) creates surface steps and grooves between the grains to improve Li + ion charging and intercalation rates; (2) removes inactive polyvinylidene difluoride (PVDF) binder from the top of graphite grains and between the grains which otherwise tends to block the Li + migration; and (3) produces carbon vacancies in (0001) planes which can provide Li + charging sites. From X-ray diffraction data, we find upshift in diffraction peak or reduction in planar spacing, from which vacancy concentration was estimated to be about 1.0%, which is higher than the thermodynamic equilibrium concentration of vacancies. The laser treatment creates single and multiple C vacancies which provide sites for Li + ions, and it also produces steps and grooves for Li + ions to enter the intercalating sites. It is envisaged that the formation of these sites enhances Li+ ion absorption during charge and discharge cycles. The current capacity increases from an average 360 mAh/g to 430 mAh/g, and C–V shows significant reduction in SEI layer formation after the laser treatment. If the vacancy concentration is too high and charge-discharge cycles are long, then trapping of electrons by Li + may occur, which can lead to Li 0 formation and Li plating causing reduction in current capacity.

25 ENERGY STORAGE↗
DOE OSTI2025

Sandwich-structured paper composite with water and oil resistance for food packaging and tableware applications

The growing environmental challenges posed by plastic waste from disposable tableware highlight the urgent need for sustainable alternatives. Traditional plastics decompose over centuries, generating microplastics that threaten ecosystems and human health. While lignin has emerged as a promising material for plastic replacement, its inherent dark brown color and processing challenges in paper-based products have limited its application, particularly in food-contact materials. Here, to address these limitations, we have developed biodegradable sandwich-structured paper composites comprising parchment paper as surface layers and a lignin-polymer core with polyvinyl alcohol (PVA) and polylactic acid (PLA). This innovative structure eliminates the need for binders, minimizing potential food contamination, and enables direct application as packaging or molded tableware. Lignin micro- and nano-particles (LMNP) enhances durability and provides natural water and oil resistance without harmful additives, such as per- and polyfluoroalkyl substances (PFAS), while PVA and PLA improve the composite's tenacity. The resulting material, composed of 65 wt% lignin, demonstrates excellent water and oil resistance, with no penetration exceeding 1 h, and exhibits enhanced tensile strength (45 MPa), making it a viable and eco-friendly alternative for disposable tableware.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Modeling the interfacial failure and resulting mechanical properties of z-pinned additively manufactured composites

The mechanical properties of Fused Filament Fabrication (FFF) parts are limited in the build direction, albeit advantages such as design flexibility and in-house customization. Here, in this paper, a novel z-pinning approach that enhances mechanical properties in the build direction by depositing material across multiple layers within the part was investigated through numerical simulations and validated experimentally. A finite element model for z-pinned composite structures was developed by assigning fiber-orientation dependent material properties obtained using a micromechanics approach to beads and pins. The bead-to-bead and pin-to-pin adhesions within the z-pinned structures were modeled using a cohesive traction separation law. The properties of cohesive elements for carbon fiber-reinforced polylactic acid (CF-PLA) z-pinned composites were calibrated using tensile experiments. The elastic modulus and tensile strength of CF-PLA z-pinned composites in the build direction were predicted with the developed numerical model. The numerical investigation on various geometrical parameters revealed that the largest pin volume increases the stiffness and tensile strength by 40% and thus, has the greatest influence on the mechanical properties of the z-pinned composites. The effect of z-pin geometrical parameters on the mechanical properties was summarized to aid in the design of z-pinned additively manufactured composite structures.

36 MATERIALS SCIENCE↗
DOE OSTI2025

3D printed polymer gaskets for custom-form batteries

Additive manufacturing (AM) processes, like 3D printing, help to facilitate complex and customizable battery geometries which can provide design freedom and enhance volumetric energy density within electronic devices. AM materials must have the thermal and mechanical properties that enable printability, and when used in batteries, AM materials must also be chemically and electrochemically compatible with the battery chemistry. The compatibility between AM materials and the battery is of particular importance for the cell packaging materials which must be inert and are often overlooked. This study systematically studies AM-compatible polymeric materials for use as gaskets in lithium-ion cells. The materials investigated include three thermoplastics suitable for material extrusion printing: polylactic acid (PLA), polycarbonate, and polypropylene/polyethylene copolymer (PPPEC); and two photoresins suitable for vat photopolymerization (VPP) printing: an acrylate-based photoresin and a polyethylene glycol diacrylate photoresin. The AM gasket materials were tested in comparison to a conventional commercial polypropylene gasket. Mechanical testing (swell measurements and material stiffness) and electrochemical testing (linear sweep voltammetry and galvanostatic cycling of full cells) demonstrated that PLA and the VPP polymers were the least compatible with the lithium-ion battery chemistry, despite their prevalent use in studies of AM batteries, and that PPPEC was the most compatible.

3D printing↗
DOE OSTI2023

Characterization of 3D printing filaments containing metal additives and their particulate emissions

Polylactic acid (PLA) filaments are widely used in fused filament fabrication (FFF) processes (3D printing). Filament additives such as metallic particles incorporated into PLA to modify functional and aesthetic features of print objects are becoming increasingly popular. However, the identities and concentrations of low percentage and trace metals in these filaments have not been well described in either the literature or product safety information included with the product. Here, we report the structures and concentrations of metals in selected Copperfill, Bronzefill and Steelfill filaments. We also report size-weighted number concentrations and size-weighted mass concentrations of particulate emissions as a function of print temperature for each filament. Particulate emissions were heterogenous in shape and size with airborne particles below 50 nm diameter dominating the size-weighted particle concentrations and larger particles (approximately 300 nm) dominating the mass weighted particle concentration. Results indicate that potential exposure to particles in the nano-size range increase when using print temperatures above 200o C. Because inhalation exposure to nanoparticles has been linked to adverse health outcomes, we suggest that using lower print temperatures for specific metal-fill filaments may reduce their operational hazard.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Aqueous-Based Polyimine Functionalization of Cellulose Nanofibrils for Effective Drying and Polymer Composite Reinforcement

Here a simple strategy was developed to synthesize polyimine-coated cellulose nanofibrils (CNF) for effective CNF drying and composite reinforcement. The polyimine was synthesized in an aqueous medium using a selective hydrophilic and hydrophobic component that forces the polyimine to precipitate, which prevents the reverse imine reaction. The polyimine coating allowed the CNF to be easily oven-dried while maintaining a fibrillar morphology to provide mechanical reinforcement in poly(ethylene terephthalate glycol) (PETG) composites. In comparison, poor mechanical performance and a heterogeneous fracture surface were observed when the coated CNF were incorporated into poly(l-lactide) (PLA) composites. It is hypothesized that intermolecular aromatic–aromatic interactions are formed at the interface between fibers and the polymer matrix in the PETG system, while no such phenomena occur in the PLA system. Overall, this facile strategy to produce modified, easily dried CNF can be adapted to produce polyimine-coated CNF with unique functionalities that are useful in a range of applications.

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

Chemical Recycling of Polybutadiene Rubber with Tailored Depolymerization Enabled by Microencapsulated Metathesis Catalysts

The effective management of plastic waste streams to prevent plastic land and water pollution is a growing problem that is also one of the most important challenges in polymer science today. Polymer materials that are stable over their lifetime and can also be cheaply recycled or repurposed as desired could more easily be diverted from waste streams. However, this is difficult for most commodity plastics. It is especially difficult to conceive this with intractable, cross-linked polymers such as rubbers. In this work, we explore the utility of microencapsulated Grubbs’ catalysts for the in-situ depolymerization and reprocessing of polybutadiene (PB) rubber. Second-generation Hoveyda-Grubbs catalyst (HG2) contained within glassy thermoplastic microspheres can be dispersed in PB rubber below the microsphere’s glass transition temperature (T g ) without adverse depolymerization, evidenced by rubber with and without these microspheres obtaining similar shear storage moduli of ≈16 and ≈28 kPa, respectively. The thermoplastic’s T g can be used to tune the depolymerization temperature, via release of HG2 into the rubber matrix. For example, using poly(lactic acid) (PLA) vs polysulfone results in an 85 and 162 °C depolymerization temperature, respectively. Liquefaction of rubber to a mixture of small molecules and oligomers is demonstrated using a 0.01 mol % catalyst loading using PLA as the encapsulant. Furthermore, at that same catalyst loading, depolymerization occurs to a greater extent in comparison to two ex-situ approaches, including a conventional solvent-assisted method, where it occurs at roughly twice the extent at each given catalyst loading. In addition, depolymerization of the microsphere-loaded rubbers was demonstrated for samples stored under nitrogen for 23 days. Lastly, we show that the depolymerized products can be reprocessed back into solid rubber with a shear storage modulus of ≈32 kPa. Thus, we envision that this approach could be used to recycle and reuse cross-linked rubbers at the end of their product lifetime.

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

Polyester functional graphenic materials as a mechanically enhanced scaffold for tissue regeneration

Traditional metal implants such as titanium, cobalt, and chromium have found wide utility in medicine; however, these come with a risk of toxicity. To overcome metal-related toxicity and enable degradability, polyesters including polycaprolactone (PCL), polylactic acid (PLA), and polyglycolic acid (PGA) show promise for the replacement of various biomedical applications of metals due to their accepted biocompatibility and FDA approval. However, polyesters are less stiff than their metallic counterparts, limiting their application to non-load bearing injury sites, such as fixation hardware for fingers. To improve mechanical properties, graphene oxide (GO)-polyester composites are a promising class of biodegradable scaffolds. Initial reports of these composites are encouraging, but mechanical properties still fall short. Traditional composites rely on non-covalent association between GO and the polyesters, which often leads to failure at the interface and weakens the overall strength of the material. Herein, we present a strategy for attachment of these FDA-approved polyesters onto a derivative of GO using a robust covalent bond. By covalently functionalizing the graphenic backbone with polyesters and without metal catalysts, we create functional graphenic materials (FGMs) to not only simultaneously retain biodegradability and compatibility, but also mechanically strengthen PCL, PLA, and PGA; we observed an average increase in the Young's modulus of over 140% compared to the graphenic backbone. These polyester-functionalized FGMs are a promising platform technology for tissue implants.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2025

Additive Manufactured Compact Microwave Absorbers

A high-performance, compact microwave absorber was created using Fused Deposition Modeling (FDM) 3D printing. Both a narrowband and a broadband absorber were created. The narrowband absorber was designed at 4.9 GHz, mid-band in WR-187 waveguide. The broadband absorber tried to achieve the best attenuation across the entire 3.95 to 5.85 GHz band. Two types of carbon loaded polylactic acid (PLA) plastic and one type of unloaded PLA were 3D printed with variable percentages of air to achieve different values of effective dielectric constant and loss tangent. The absorber comprised five or six rectangular pieces of these plastic materials. The thickness and fill factor values for each piece were optimized to minimize reflection through fast analytic modeling in MATLAB®. The results were then verified by HFSS® simulation as well. The stack progressed from the lowest loss and lowest dielectric constant to the highest at the shorting end. The final narrowband load had simulated return loss of 87 dB at 4.9 GHz with an analytic solution in MATLAB. The measured return loss of the 3D printed attenuator was 73 dB at 4.929 GHz. The total length of the absorber was 2.44 inches. A commercial absorber for WR-187 with return loss of 40 dB has length of 13 inches. The experiment proves that an effective and compact microwave absorber can be created using 3D printing.

36 MATERIALS SCIENCE↗
DOE OSTI2023

A comparative study of cerium oxides formed by pulsed laser ablation and continuous wave laser heating

Abstract The formation of Ce 2 O 3 from cerium metal requires complex reducing conditions. Alternatively, we show that different stoichiometries and structures of cerium oxides can be generated in high‐temperature laser experiments by varying the availability of oxygen and the use of either pulsed laser ablation (PLA) or continuous wave (CW) laser heating of cerium metal. X‐ray diffraction and Raman spectroscopy suggest that a low structural order Ce 2 O 3 /CeO 2 mixed structure is formed in a 1% O 2 atmosphere with PLA. For CW heating in a 1% O 2 environment, Raman measurements show the formation of crystalline A‐type Ce 2 O 3 in proximity to the point of laser impingement. These experiments were repeated in 18 O 2 and allowed us to report for the first time the corresponding Raman spectrum of Ce 2 18 O 3 .

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

Nanosecond Laser Annealing of NMC 811 Cathodes for Enhanced Performance

Improved performance of lithium-ion batteries (LIBs) plays a critical role in the future of next- generation battery applications. Nickel-rich layered oxides such as LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC 811), are popular cathodes due to their high energy densities. However, they suffer from high surface reactivity, which results in the formation of Li 2 CO 3 passive layer. Herein, we show the role of nanosecond pulsed laser annealing (PLA) in improving the current capacity and cycling stability of LIBs by reducing the carbonate layer, in addition to forming a protective LiF layer and manipulating the NMC 811 microstructures. We use high-power nanosecond laser pulses in a controlled way to create nanostructured surface topography which has a positive impact on the capacity retention and current capacity by providing an increased active surface area, which influences the diffusion kinetics of lithium-ions in the electrode materials during the battery cycling process. Advanced characterizations show that the PLA treatment results in the thinning of the passive Li 2 CO 3 layer, which is formed on as-received NMC811 samples, along with the decomposition of excess polyvinylidene fluoride (PVDF) binder. The high-power laser interacts with the decomposed binder and surface Li + to form LiF phase, which acts as a protective layer to prevent surface reactive sites from initiating parasitic reactions. As a result, the laser treated cathodes show relative increase of the current capacity of up to 50%, which is consistent with electrochemical measurements of LiB cells.

25 ENERGY STORAGE↗
DOE OSTI2024

Optimal load attachment of a deeply embedded ring anchor in clay

A Deeply Embedded Ring Anchor (DERA) system has been developed as a cost-effective solution for mooring arrays of floating offshore wind turbines (FOWTs) to the seabed. The DERA boasts several key features, including its versatility in various soil types, compact size, compatibility with diverse mooring systems, multi-line potential, and robust performance even under unintentional loading conditions. While prior preliminary studies have provided valuable insights into how the DERA can enhance cost-effectiveness by offering a high load capacity, these studies have predominantly focused on optimizing anchor performance under translational horizontal and vertical loading. However, to design the DERA optimally, we must also consider its ability to handle inclined loading conditions in addition to lateral and axial loadings. Due to its shorter length compared to a conventional caisson, the DERA has less resistance to moments, making it more sensitive to horizontal load capacity and the optimal load attachment depth concerning load angle. For this reason, our study introduces an analytical approach to evaluate the effects of inclined loading on anchor performance, utilizing the previously validated upper bound plastic limit analysis (PLA) method. In investigating the optimal load attachment of the DERA, this paper conducts a parametric study to analyze how factors such as load attachment depth, anchor aspect ratio, and load inclination affect the DERA’s load capacity. Our findings indicate that PLA can serve as a valuable analytical tool for assessing the ultimate load capacity of the DERA, particularly under inclined loading conditions.

42 ENGINEERING↗
DOE OSTI2020

Effects of Testosterone Supplementation on Ghrelin and Appetite During and After Severe Energy Deficit in Healthy Men

Abstract Background Severe energy deficits cause interrelated reductions in testosterone and fat free mass. Testosterone supplementation may mitigate those decrements, but could also reduce circulating concentrations of the orexigenic hormone ghrelin, thereby exacerbating energy deficit by suppressing appetite. Objective To determine whether testosterone supplementation during severe energy deficit influences fasting and postprandial ghrelin concentrations and appetite. Design and methods Secondary analysis of a randomized, double-blind trial that determined the effects of testosterone supplementation on body composition changes during and following severe energy deficit in nonobese, eugonadal men. Phase 1 (PRE-ED): 14-day run-in; phase 2: 28 days, 55% energy deficit with 200 mg testosterone enanthate weekly (TEST; n = 24) or placebo (PLA; n = 26); phase 3: free-living until body mass recovered (end-of-study; EOS). Fasting and postprandial acyl ghrelin and des-acyl ghrelin concentrations and appetite were secondary outcomes measured during the final week of each phase. Results Fasting acyl ghrelin concentrations, and postprandial acyl and des-acyl ghrelin concentrations increased in PLA during energy deficit then returned to PRE-ED values by EOS, but did not change in TEST (phase-by-group, P < 0.05). Correlations between changes in free testosterone and changes in fasting acyl ghrelin concentrations during energy deficit (ρ = -0.42, P = 0.003) and body mass recovery (ρ = -0.38; P = 0.01) were not mediated by changes in body mass or body composition. Transient increases in appetite during energy deficit were not affected by testosterone treatment. Conclusions Testosterone supplementation during short-term, severe energy deficit in healthy men prevents deficit-induced increases in circulating ghrelin without blunting concomitant increases in appetite. Clinical Trials Registration www.clinicaltrials.gov NCT02734238 (registered 12 April 2016).

Karl, J. Philip↗
DOE OSTI2026

Thermal images collected during 3D printing with Cincinnati BAAM

This data set contains images produced to test the performance of anomaly and fault detection methods in the context of additive manufacturing. A total of 10 print jobs were executed using a Cincinnati BAAM (model 606) with a Cincinnati medium compression screw. The material used was compounded polylactic acid (PLA) with wood flour as a filler produced by Jabil (80% NatureWorks Ingeo 6060D amorphous PLA, % 100 mesh pine flour from American Wood Fiber). Print sheets were 1/4in polycarbonate.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Biochar-compost-based controlled-release nitrogen fertilizer intended for an active microbial community

Nitrogen (N) fertilizers in agriculture suffer losses by volatilization of N to the air, surface runoff and leaching into the soil, resulting in low N use efficiency (NUE) (< 50%) and raising severe environmental pollutions. Controlled- release nitrogen fertilizers (CRNFs) can control the release of N nutrients to NUE in crop production. Different methods were used to develop new CRNFs. However, different CRNF technologies are still underdeveloped due to inadequate controlling on N releasing time and/or unsustainable diffusion. The study on the influences of CRNF processing parameters on microbial conditions are lacking when the CRNFs composed of various bio-ingredients such as biochar, composts, and biowaste. The complexity of processing methods, material biodegradability, and other physical properties make current CRNFs of questionable value in agricultural production. This research aims to develop a novel biochar-compost-based controlled-release urea fertilizer (BCRUF) to preserve microbial properties carried by the compost. The BCRUF was synthesized by pelletizing the 50:50 (dry, wt/wt) mixture of biochar and compost. BCRUF was loaded with urea and then spray-coated with polylactic acid (PLA). The releasing time of two types of BCRUFs, coated and uncoated with PLA, for 80% of N release in water was up to 6 h at three different temperatures (4, 23, and 40 °C), compared to conventional urea fertilizer and commercial environmentally smart N (ESN) fertilizer. The releasing time of coated BCRUF for 80% N release in soil was up to 192 h (8 days). Fourier-transform infrared spectroscopy (FTIR) analysis revealed that no new functional groups were found in the release solution, indicating no new chemical hazards generated. The differential scanning calorimetry (DSC) tests also verified that its thermal stability could be up to 160 °C. The microbe populations in the BCRUF pellets were reduced after the pelleting and drying processes in BCRUF fabrication, but a few bacteria can endure in the air-drying process. BCRUF pellets soaked in water for 4 days retained some bacteria. The BCRUF showed very promising characteristics to improve NUE and sustainability in agricultural production.

58 GEOSCIENCES↗
DOE OSTI2021

Mineral-Ground Micro-Fibrillated Cellulose Reinforcement for Polymer Compounds

Additive Manufacturing (AM) is quickly becoming a mainstream, energy efficient manufacturing technique for complex and custom components. ORNL has taken polymer AM into the next level with Big Area Additive Manufacturing (BAAM). However, we need to develop the strength of AM materials (specifically polymers) to satisfy the mechanical requirements of structural parts. Also, it is crucial that the developed process can easily be scaled up to have a significant impact in the manufacturing industry of US. Furthermore, renewable, bio-derived AM materials are desirable from a sustainability perspective. In the first phase of this project the mechanical properties of polymer AM components were significantly improved developing a micro fibrillated cellulose (MFC)-reinforced composite material system that is derived from biomass and compatible with BAAM. Unfortunately, the improvements were observed only with freeze-dried MFCs, and freeze-drying is a very slow process and is not industrially scalable. Furthermore, MFCs were not available in large quantities at low cost. However, FiberLean has reached 12,000 tons/year capacity (60,000 tons/year including the minerals). FiberLean offers MFCs at a scale and order of magnitude lower price than current market participants. With their recently developed novel (patent pending) drying process FiberLean can achieve over 50% solid content commercially. In the 2nd phase of the project, the original objective was to investigate this new novel drying process along with compounding with different formulations to optimize and adapt to large scale additive manufacturing. However, the compounded materials prepared via this approach were very brittle and demonstrated poor mechanical performance. Therefore, the project was focused more on a scalable chemical surface modification of MFCs to enable their drying via conventional oven process with minimal agglomeration and better dispersion in PLA polymer matrix. Fiberlean and ORNL have worked together in this project to develop mineral-ground microfibrillated cellulose (MFC) - reinforced additive manufacturing feedstock materials with significantly improved mechanical properties. Properly surface modified and dried Fiberlean cellulose microfibrils led to tensile strength increases up to ~40% and elastic modulus increases up to 70% with the addition of 30% MFC into PLA matrix. The work has led to a high impact journal article and a provisional patent. Opportunities for a follow up work to demonstrate the technology in large scale and application of it to AM applications are currently being searched.

36 MATERIALS SCIENCE↗
DOE OSTI2024

An Investigation of Oxides of Tantalum Produced by Pulsed Laser Ablation and Continuous Wave Laser Heating

Recent progress has seen multiple Ta 2 O 5 polymorphs generated by different synthesis techniques. However, discrepancies arise when these polymorphs are produced in widely varying thermodynamic conditions and characterized using different techniques. This work aimed to characterize and compare Ta 2 O 5 particles formed at high and low temperatures using nanosecond pulsed laser ablation (PLA) and continuous wave (CW) laser heating of a local area of tantalum in either air or an 18 O 2 atmosphere. Scanning electron microscopy (SEM) and Raman spectroscopy of the micrometer-sized particles generated by PLA were consistent with either a localized amorphous Ta 2 O 5 phase or a similar, but not identical, crystalline β-Ta 2 O 5 phase. The Raman spectrum of the material formed at the point of CW laser impingement was in good agreement with the previously established ceramic “H-Ta 2 O 5 ” phase. TEM and electron diffraction analysis of these particles indicated the phase structure matched an oxygen-vacated superstructure of monoclinic H-Ta 2 O 5 . Further from the point of laser impingement, CW heating produced particles with a Raman spectrum that matched β-Ta 2 O 5 . We confirmed that the high-temperature ceramic phase characterized in previous work by Raman spectroscopy was the same monoclinic phase characterized in different work by TEM and could be produced by direct laser heating of metal in air.

36 MATERIALS SCIENCE↗