Ppm O2 Research Articles

Optimizing Magnetic Force Microscopy Resolution and Sensitivity to Visualize Nanoscale Magnetic Domains.

Magnetic force microscopy (MFM) enables mapping local magnetic fields across a sample surface with nanoscale resolution. To perform MFM, an atomic force microscopy (AFM) probe whose tip has been magnetized vertically (i.e., perpendicular to the probe cantilever) is oscillated at a fixed height above the sample surface. The resultant shifts in the oscillation phase or frequency, which are proportional to the magnitude and sign of the vertical magnetic force gradient at each pixel location, are then tracked and mapped. Although the spatial resolution and sensitivity of the technique increases with decreasing lift height above the surface, this seemingly straightforward path to improved MFM images is complicated by considerations such as minimizing topographical artifacts due to shorter range van der Waals forces, increasing the oscillation amplitude to further improve sensitivity, and the presence of surface contaminants (in particular water due to humidity under ambient conditions). In addition, due to the orientation of the probe's magnetic dipole moment, MFM is intrinsically more sensitive to samples with an out-of-plane magnetization vector. Here, high-resolution topographical and magnetic phase images of single and bicomponent nanomagnet artificial spin-ice (ASI) arrays obtained in an inert (argon) atmosphere glovebox with <0.1 ppm O2 and H2O are reported. Optimization of lift height and drive amplitude for high resolution and sensitivity while simultaneously avoiding the introduction of topographical artifacts is discussed, and detection of the stray magnetic fields emanating from either end of the nanoscale bar magnets (~250 nm long and <100 nm wide) aligned in the plane of the ASI sample surface is shown. Likewise, using the example of a Ni-Mn-Ga magnetic shape memory alloy (MSMA), MFM is demonstrated in an inert atmosphere with magnetic phase sensitivity capable of resolving a series of adjacent magnetic domains each ~200 nm wide.

Time-Sensitive Aspects of Mars Sample Return (MSR) Science.

Time-Sensitive Aspects of Mars Sample Return (MSR) Science.

Transcriptomic analysis of chloride tolerance in Leptospirillum ferriphilum DSM 14647 adapted to NaCl.

Chloride ions are toxic for most acidophilic microorganisms. In this study, the chloride tolerance mechanisms in the acidophilic iron-oxidizing bacterium Leptospirillum ferriphilum DSM 14647 adapted to 180 mM NaCl were investigated by a transcriptomic approach. Results showed that 99 genes were differentially expressed in the adapted versus the non-adapted cultures, of which 69 and 30 were significantly up-regulated or down-regulated, respectively. Genes that were up-regulated include carbonic anhydrase, cytochrome c oxidase (ccoN) and sulfide:quinone reductase (sqr), likely involved in intracellular pH regulation. Towards the same end, the cation/proton antiporter CzcA (czcA) was down-regulated. Adapted cells showed a higher oxygen consumption rate (2.2 x 10−9 ppm O2 s-1cell-1) than non-adapted cells (1.2 x 10−9 ppm O2 s-1cell-1). Genes coding for the antioxidants flavohemoprotein and cytochrome c peroxidase were also up-regulated. Measurements of the intracellular reactive oxygen species (ROS) level revealed that adapted cells had a lower level than non-adapted cells, suggesting that detoxification of ROS could be an important strategy to withstand NaCl. In addition, data analysis revealed the up-regulation of genes for Fe-S cluster biosynthesis (iscR), metal reduction (merA) and activation of a cellular response mediated by diffusible signal factors (DSFs) and the second messenger c-di-GMP. Several genes related to the synthesis of lipopolysaccharide and peptidoglycan were consistently down-regulated. Unexpectedly, the genes ectB, ectC and ectD involved in the biosynthesis of the compatible solutes (hydroxy)ectoine were also down-regulated. In line with these findings, although hydroxyectoine reached 20 nmol mg-1 of wet biomass in non-adapted cells, it was not detected in L. ferriphilum adapted to NaCl, suggesting that this canonical osmotic stress response was dispensable for salt adaptation. Differentially expressed transcripts and experimental validations suggest that adaptation to chloride in acidophilic microorganisms involves a multifactorial response that is different from the response in other bacteria studied.

Sulphuric acid aerosols in low oxygen environments

Experiments on sulphuric acid nucleation in low oxygen atmospheres were done in order to investigate the role of nucleation in the Archean atmosphere. Nucleation initiated by photolysis of SO2 and subsequent reaction between atomic O and SO2 was measured with a PSM and a separate CPC. The parameters were <10 ppm O2 with varying levels of SO2 (4 levels from 40 to 105 ppb), RH (3 levels from 0 to 51%), UV light (254 nm, 4 levels from 55 to 100% power), and ionization (2 levels: Background (∼3 cm−3 s−1) and increased w. gamma sources (∼42 cm−3 s−1)). We find that nucleation is possible under these conditions and that the measured formation rates correlate positively with all varied parameters. This suggests that the sulphuric acid nucleation system could have played a role in the Archean atmosphere.

Atmospheric Profit & Loss — Oxygen Depletion as the Remaining Piece for a Proper CO2 Emissions Assessment

Climate change is one of the most pressing matters of modern society. The current models for assessing CO2 emissions do not consider the oxygen drainage from the atmosphere. Oxygen depletion is happening at rates much higher than the natural capacity of the planet to regenerate the oxygen back to the atmosphere through photosynthesis. On average, each 1.0 ppm increase of CO2 brings a corresponding loss of 2.15 ppm of O2 in the atmosphere. The present work provides a new methodology for emissions assessment that includes oxygen usage called Atmospheric Profit and Loss Score. Simple examples are provided to demonstrate that, once oxygen is included in the assessment, renewable and photosynthesis-based processes that follow the sustainability criteria become much more attractive to society.

Self-Sensitized and Reversible O2 Reactivity with Bisphenalenyls for Simple, Tunable, and Multicycle Colorimetric Oxygen-Sensing Films.

Monitoring the levels of molecular oxygen (O2) is critical for numerous applications, but there is still a long-standing challenge to develop robust and cost-effective colorimetric sensors that enable detection by changes in color. Current technologies employ chromophores that require additional additives, which inherently increase the cost and complexity. Here, we report that bisphenalenyls (PQPLs) function as the single active component for colorimetric O2 sensing through their quantitative conversion into aromatic endoperoxides (EPOs). PQPLs display self-sensitizing reactivity: they are capable of generating singlet oxygen and binding it without the need for external photosensitizers. The rates of PQPL photooxygenation depend on the electron-donating ability of substituents, which highlights a simple strategy for tuning O2 sensitivity. EPOs are stable under ambient conditions but can be thermally stimulated to convert back to PQPLs and concomitantly release O2. Polymer-supported (PTMSP) films of PQPLs (2 wt %) reproduce these reactivity trends with a rapid red-to-colorless transition that is visible to the naked eye within 1 h of exposure and show a very low limit of detection (<5 ppm O2). Films are chemically and thermally robust and maintain up to >99% of their original colorimetric response when reused and subjected to multiple cycles of photooxygenation and O2 release. The simplicity and solution processability of these materials highlight their potential as "intelligent" inks for printable colorimetric sensors.

Residual stresses and porosity in Ti-6Al-4V produced by laser powder bed fusion as a function of process atmosphere and component design

The influence of the process gas, laser scan speed, and sample thickness on the build-up of residual stresses and porosity in Ti-6Al-4V produced by laser powder bed fusion was studied. Pure argon and helium, as well as a mixture of those (30% helium), were employed to establish process atmospheres with a low residual oxygen content of 100 ppm O2. The results highlight that the subsurface residual stresses measured by X-ray diffraction were significantly lower in the thin samples (220 MPa) than in the cuboid samples (645 MPa). This difference was attributed to the shorter laser vector length, resulting in heat accumulation and thus in-situ stress relief. The addition of helium to the process gas did not introduce additional subsurface residual stresses in the simple geometries, even for the increased scanning speed. Finally, larger deflection was found in the cantilever built under helium (after removal from the baseplate), than in those produced under argon and an argon-helium mixture. This result demonstrates that complex designs involving large scanned areas could be subjected to higher residual stress when manufactured under helium due to the gas’s high thermal conductivity, heat capacity, and thermal diffusivity.

Potential impacts of oxygen impurities in carbon capture and storage on microbial community composition and activity

Gaseous impurities, such as O2, are expected to be present within CO2 captured for storage. This could stimulate microbial activity in a geological CO2 storage site which has the potential to lead to operational issues such as injection well blockages, corrosion and oil souring. A series of experiments were carried out to examine the effect of 10 ppm and 100 ppm O2 in an anoxic (CO2 or N2) atmosphere on microbial communities and microbial gas production in laboratory scale experiments. Experiments inoculated with sulphate reducing bacteria enrichments were compared to uninoculated controls. The results show that H2S production is delayed in a CO2 atmosphere compared to the N2 atmosphere. 100 ppm O2 in CO2 resulted in a spike of H2S production as well as greater bacterial biomass when compared to the 10 ppm O2 in CO2 atmosphere. The inoculated N2 experiments showed similar patterns in H2S production and biomass regardless of O2 concentration. These results suggest that a concentration of O2 lower than 100 ppm in CO2 could reduce the potential for microbial growth and H2S production in CO2 storage sites. CH4 production was observed in some microcosms subsequent to H2S production, highlighting the potential for microbial methanogenesis in the in CCS reservoirs.

Growth of 1D TiO2 nanostructures on Ti substrates incorporated with residual stress through humid oxidation and their characterizations

Different Ti substrates, such as particles (as-received and ball milled), plate and TEM grid were oxidized for the growth of one dimensional (1D) TiO2 nanostructures. The Ti substrates were oxidized for 4 h at temperatures of 700 °C–750 °C in humid and dry Ar containing 5 ppm of O2. The effects of residual stress on the growth of 1D TiO2 nanostructures were investigated. The residual stress inside the Ti particles was measured by XRD-sin2 ψ technique. The oxidized Ti substrates were characterized using field emission scanning electron microscope equipped with energy dispersive x-ray spectroscope, transmission electron microscope, x-ray diffractometer and x-ray photoelectron spectroscope. Results revealed that humid environment enhances the growth of 1D TiO2 nanostructures. Four different types of 1D morphologies obtained during humid oxidation, e.g. stacked, ribbon, plateau and lamp-post shaped nanostructures. The presence of residual stress significantly enhances the density and coverage of 1D nanostructures. The as-grown TiO2 nanostructures possess tetragonal rutile structure having length up to 10 μm along the 〈1 0 1〉 directions. During initial stage of oxidation, a TiO2 layer is formed on Ti substrate. Lower valence oxides (Ti3O5, Ti2O3 and TiO) then form underneath the TiO2 layer and induce stress at the interface of oxide layers. The induced stress plays significant role on the growth of 1D TiO2 nanostructures. The induced stress is relaxed by creating new surfaces in the form of 1D TiO2 nanostructures. A diffusion based model is proposed to explain the mechanism of 1D TiO2 growth during humid oxidation of Ti. The 1D TiO2 nanostructures and TiO2 layer is formed by the interstitial diffusion of Ti4+ ions to the surface and reacts with the surface adsorbed hydroxide ions (OH−). Lower valence oxides are formed at the metal-oxide interface by the reaction between diffused oxygen ions and Ti ions.

Oxidizing atmosphere and life on land during the late Paleoproterozoic outset of the “boring billion”

The so called “boring billion” (1800–800 Ma) of Late Paleoproterozoic and early Mesoproterozoic time can now be reassessed from the evidence of diverse paleosols in the Ruyang Group (1749–1561 Ma) in Henan Province, China. Widespread marine sulfidic facies is the reason for the term “boring billion”, but terrestrial facies and paleosols were far from uniform or anoxic at that time. The Ruyang Group in Henan has 12 distinct kinds of paleosols, with 5 distinct pedotypes in alluvial fan facies of the Bingmagou Formation, 6 in fluvial facies of the Yunmengshan Formation, 3 in coastal plain facies of the Baicaoping Formation, and 4 in the coastal to intertidal Beidajian Formation. These paleosols are evidence of hyperarid climate that was cool temperate despite proximity to the paleoequator. These ancient soils were alive with iron- and manganese-fixing bacteria that created desert varnish and vesicular structure, as well as sulfur-oxidizing bacteria creating desert roses of gypsum. The paleosols may also have supported cyanobacteria, algae and fungi, known from palynomorphs in shales of the Baicaoping and Beidajian formations. Consumption of alkali and alkaline earth elements in the paleosols are evidence of 1700–20,600 ppm (6–73 times preindustrial level or PAL) of atmospheric CO2, consistent with the amount needed for a greenhouse effect to offset a faint young sun. A comparable model based on iron and manganese oxidation in the paleosols indicates 318–16,623 ppm (0.002–0.08 PAL) O2. This was enough to support animals (0.005 PAL O2), considering that these are minimal estimates of O2 diluted by some soil respiration. Animals had not yet evolved, but that evolutionary process may not have been limited by atmospheric composition.

Effects of hypoxia and hyperoxia on growth parameters and transcription levels of growth, immune system and stress related genes in rainbow trout

Hypoxia and hyperoxia are disparate stressors which can have destructive influences on fish growth and physiology. It is yet to be determined if hypoxia and hyperoxia have a cumulative effect in aquatic ecosystems that affect biological parameters in fish, and to understand if this is associated with gene expression. Here we address whether growth performance and expressions of growth, immune system and stress related genes were affected by hypoxia and hyperoxia in fish. Rainbow trout was chosen as the study organism due to its excellent service as biomonitor. After an acclimatization period, fish were exposed to hypoxia (4.0 ± 0.5 ppm O2), normoxia (7.5 ± 0.5 ppm O2) and hyperoxia (12 ± 1.2 ppm O2) for 28 days. At 6 h, 12 h, 24 h, 48 h, 72 h and 28 days, samples were collected. Hypoxia and hyperoxia negatively affected weight gain (WG), specific growth rate (SGR), survival rate (SR) and feed conversion ratio (FCR). The best WG, SGR, SR and FCR values occurred in fish exposed to normoxia, whereas hypoxia was most suppressive on growth and hyperoxia showed intermediate suppression of these parameters. Gene expression analyses were performed in liver and results revealed that long term exposure caused reduced growth hormone-I (GH-I) and insulin like growth factor I-II (IGF I-II) levels in both hypoxia and hyperoxia-treated fish. Heat shock protein (HSP70) levels increased in both hypoxia and hyperoxia treatment, and both exposures caused elevation of leptin (LEP) expression in long-term exposure. Overall data indicate that both hypoxia and hyperoxia cause stress in rainbow trout and negatively affects growth parameters.

Effect of the Process Atmosphere Composition on Alloy 718 Produced by Laser Powder Bed Fusion

The detrimental effect of nitrogen and oxygen when it comes to the precipitation of the strengthening γ’’ and γ’ phases in Alloy 718 is well-known from traditional manufacturing. Hence, the influence of the two processing atmospheres, namely argon and nitrogen, during the laser powder bed fusion (L-PBF) of Alloy 718 parts was studied. Regardless of the gas type, considerable losses of both oxygen of about 150 ppm O2 (≈30%) and nitrogen on the level of around 400 ppm N2 (≈25%) were measured in comparison to the feedstock powder. The utilization of nitrogen as processing atmosphere led to a slightly higher nitrogen content in the as-built material—about 50 ppm—compared to the argon atmosphere. The presence of the stable nitrides and Al-rich oxides observed in the as-built material was related to the transfer of these inclusions from the nitrogen atomized powder feedstock to the components. This was confirmed by dedicated analysis of the powder feedstock and supported by thermodynamic and kinetic calculations. Rapid cooling rates were held responsible for the limited nitrogen pick-up. Oxide dissociation during laser–powder interaction, metal vaporization followed by oxidation and spatter generation, and their removal by processing atmosphere are the factors describing an important oxygen loss during L-PBF. In addition, the reduction of the oxygen level in the process atmosphere from 500 to 50 ppm resulted in the reduction in the oxygen level in as-built component by about 5%.

Topographic and nanomechanical mapping of plutonium surfaces

Atomic force microscopy of gallium-stabilized δ-phase plutonium coupons has been used to map their topography and qualitative mechanical character, including Derjaguin-Muller-Toporov modulus, adhesion, deformation, and dissipation. Initial topographical results demonstrate that the plutonium surface is considerably rough and heterogeneous. Qualitative nanomechanical mapping revealed distinct striation patterns that are not observed in the topography images. Further investigation of the striations in the nanomechanical modes of imaging suggest that they are not measurement artifacts, or plutonium specific features. Similar investigations of stainless steel surfaces established a strong correlation between the mechanical working of the surface (i.e. cutting and grinding) and the appearance of the striations. Reimaging of the plutonium surface after moderate oxidation occurring within an inert Ar atmosphere (∼1 ppm O2) over the course of 13 months revealed a diminished striation pattern. It is suggested that surface stress/strain induced by the mechanical working of the metal surfaces results in the patterns of variable modulus, adhesion, deformation, and dissipation, and that these patterns are affected by the chemical changes and aging of the plutonium surface.

Bituminous Coal Char-Derived Hard Carbon As a Low-Cost Anode Material for Sodium-Ion Batteries

Increasing demands in the global energy markets for large-scale electric energy storage systems have made it essential to improve current rechargeable battery technologies. Due to the high price and low safety of current commercial lithium-ion batteries, as well as potential resource limitations of lithium, there is a need to explore alternative ion intercalation battery technologies [1]. Sodium-ion batteries (SIBs), having a theoretical energy density comparable with lithium-ion, are a promising next-generation energy storage technology to replace lithium-ion batteries in large-scale, stationary energy storage applications. A current challenge in achieving high performance SIBs is improving capacity and reducing cost of anode materials. While carbons derived from coal tar pitch have been widely studied as intercalation materials, hard carbons derived from coal char (the solid component of bituminous and sub-bituminous coals) are only recently gaining attention as SIB anode materials with surprisingly high sodium storage capacity, good rate performance, and long cycle life [2]. Bituminous coal char is used primarily as a fuel source for power production, making it an extremely low-cost electrode material. The high mineral ash content of with bituminous coal char, however, is a significant challenge to achieving high anode capacities with this material.This work investigates the effect of pyrolysis conditions and deashing parameters on the material properties and sodium-ion intercalation capacity of hard carbons derived from bituminous, SUFCO mine coal char. SUFCO coal, known as steam coal, is a local Utah coal used for power generation. Pyrolysis temperature and atmosphere, as well as acid/base washing conditions, are varied to produce anode materials with varying carbon structure and ash content. Deashing conditions explored in this work include treating raw coal char with various basic and dilute acid (10%) solutions, as well as a high concentration mixture of H2SO4:HNO3 (30:70), at different temperatures (22°C and 80 °C) and for varying times. The structure and composition of the resulting carbons are characterized via scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and pore-size distribution measurements. Electrochemical behavior is investigated by assembling coin cells (half-cells using Na metal and NaClO4 electrolyte), in a nitrogen glove box (LC Technology Solutions Inc, <0.1 ppm H2O, <0.1 ppm O2) using an MTI CR20XX coin cell press. All coin cell testing is performed using a Gamry Interface 1000E potentiostat and a Gamry four-terminal coin cell holder. The results provide insight into process-structure-performance relationships for coal char-derived hard carbons as SIB anode materials, including charge-discharge capacity, cycle life, rate performance, and electrochemical impedance.This work is supported in-part by NSF Award #1742696.[1] P. Bai, Y. He, X. Zou, X. Zhao, P. Xiong, Y. Xu, Elucidation of the Sodium-Storage Mechanism in Hard Carbons, Adv. Energy Mater. 8 (2018) 1–9.[2] Yunming Li, Yong-Sheng Hu, Xingguo Qi, Xiaohui Rong, Hong Li, Xuejie Huang, Liquan Chen, Advanced sodium-ion batteries using superior low cost pyrolyzed anthracite anode: towards practical applications, Energy Storage Materials 5 (2016) 191–197. Figure 1

Corrosion of SS310 and Alloy 740 in high temperature supercritical CO2 with impurities H2O and O2

This study investigated corrosion performance of SS310 and Alloy 740 in supercritical CO2 with the impurity of 100 ppm H2O or O2 at 600 °C and 30 MPa for up to 1000 h. The addition of 100 ppm H2O remarkably enhanced general and localized oxidations while the presence of O2 led to the opposite tendency. Alloy 740 exhibited better resistance to carburization compared to SS310, possibly due to the higher solubility of carbides in Ni-based alloys than those in Fe-based alloys. Both alloys exhibit near parabolic oxidation behavior and acceptable corrosion resistance in the supercritical CO2 environments.

Process intensification of the high-purity nitrogen production in twin-bed Pressure Swing Adsorption plants

With increasing nitrogen purity, PSA plants require an over-proportional air demand with the consequence that high-purity PSA systems engender a distinct interest in energy-saving measures. This paper presents process intensification strategies with the focus on a reduced energy consumption. Therefore, the influence of PSA configuration and cycle organisation on process performance was investigated. Results are presented at two product purity levels (10 ppm/1000 ppm O2) and two operating temperatures (25 °C/45 °C) in a lab-scale twin bed PSA (2 × 2 L). It is shown that dedicated strategies are available to intensify the PSA process; however, their effects are dependent on ambient conditions and product purity levels.

Oxygen balance during laser powder bed fusion of Alloy 718

The generation of spatters during laser powder bed fusion (L-PBF) of Alloy 718 is known to be detrimental for the re-use of the feedstock powder and the quality of the final product. In this study, dedicated powder sampling from different positions within the build chamber and powder bed was performed. The results clearly indicate the importance of the surface-to-volume ratio of the built components on powder degradation, as demonstrated by the analysis of the powder using capsules filled with dense lattice structures. Extensive formation of Al- and Cr-rich oxides on the entrained powder deposited on the gas inlet and outlet was detected. Significant oxygen pick-up by spatter particles compared to the virgin powder was measured (>300 ppm O2); while the as-built material experienced a slight loss (~30 ppm O2). The change in the microstructure of spatter particles in comparison to the virgin powder, namely the primary dendrite arm spacing, indicates significantly higher cooling rate during spatter solidification, estimated to be of about 108 K/s, compared to around 106 K/s for the virgin powder and 107 K/s for the L-PBF component. These findings allows to evaluate the extent of powder degradation during L-PBF and establish the oxygen balance of the process.

Mitigating oxygen pick-up during laser powder bed fusion of Ti-6Al-4V by limiting heat accumulation

The dissolution of oxygen in Ti-6Al-4V during laser powder bed fusion (L-PBF) is a limitation for the final ductility of the produced components and a challenge for the end-users. In the present work, the effect of the residual oxygen in the process atmosphere of a laboratory scale L-PBF machine, as well as the role of heat accumulation, are studied. It was shown that oxygen content in the as-built Ti-6Al-4V is determined by the size of the scanned area and build time. The heat accumulation aspect was investigated by adjusting the inter-layer time (ILT), by increasing the recoating time or the number of produced parts. The results showed that oxygen pick-up could be limited by reducing residual oxygen level in the atmosphere or heat accumulation. A 400 ppm O2 reduction measured at the top of a 70 mm column was achieved by increasing the ILT manually by 4.5 s, and a 1200 ppm O2 reduction by increasing the scanned area by 7 times. By doing so, the hardness at full height was reduced by approximately 30 HV10. It is shown that design features characterised by high aspect ratio can absorb significant amount of oxygen resulting in increased brittleness.

Oxygen Balance During Laser Powder Bed Fusion of Alloy 718

The generation of spatters during laser powder bed fusion (L-PBF) of Alloy 718 is known to be detrimental for the re-use of the feedstock powder and the quality of the final product. In this study, dedicated powder sampling from different positions within the build chamber and powder bed was performed. The results clearly indicate the importance of the surface-to-volume ratio of the built components on powder degradation, as demonstrated by the analysis of the powder using capsules filled with dense lattice structures. Extensive formation of Al- and Cr-rich oxides on the entrained powder deposited on the gas inlet and outlet was detected. Significant oxygen pick-up by spatter particles compared to the virgin powder was measured (>300 ppm O2); while the as-built material experienced a slight loss (~30 ppm O2). The change in the microstructure of spatter particles in comparison to the virgin powder, namely the primary dendrite arm spacing, indicates significantly higher cooling rate during spatter solidification, estimated to be of about 108 K/s, compared to around 106 K/s for the virgin powder and 107 K/s for the L-PBF component. These findings allows to evaluate the extent of powder degradation during L-PBF and establish the oxygen balance of the process.

Control of residual oxygen of the process atmosphere during laser-powder bed fusion processing of Ti-6Al-4V

The effect of the residual oxygen concentration in the process atmosphere during laser-powder bed fusion (L-PBF) of Ti-6Al-4V was investigated, using an external oxygen monitoring system equipped with two types of oxygen sensors typically used in L-PBF hardware: a lambda probe and an electrochemical oxygen sensor. The recordings of the oxygen variations during L-PBF highlighted that the electrochemical sensor is more reliable than the lambda probe, whose signal showed a maximum deviation of about 700 ppm O2 after 7 h, attributed to its sensitivity to hydrogen present in the system. The study revealed that proper monitoring of the oxygen in the laboratory scale L-PBF system used is necessary to limit oxygen and nitrogen pick-ups by the built material. Concentrations as high as 2200 ppm O2 and 500 ppm N2 in the Ti-6Al-4V part built under standard conditions were measured, compared to maximum levels of 1800 ppm O2 and 250 ppm N2 with the external oxygen control. In addition, the findings underline the critical effect of the component design, such as the high aspect ratio columns or the lattice structures, on the heat accumulation in case of Ti-6Al-4V, leading to enhanced oxygen and nitrogen pick-up, as high as 600 ppm O2 and 150 ppm N2 difference between the bottom and top of the cylindrical samples of 70 mm height used in this study. The determination of tensile properties of samples built at different heights put in evidence the detrimental effect of the oxygen increase with build height on the ductility, which decreased from 12% to below 6% between the bottom and top positions. This work highlights that the possible presence of impurities in the L-PBF atmosphere can have harmful impact on the properties of Ti-6Al-4V components, which can be mitigated adjusting the oxygen control system.