Welding fumes induce lung toxicity and are carcinogenic to humans but the molecular mechanisms have yet to be clarified. The aim of this study was to evaluate the toxicity of stainless and mild steel ...particles generated via gas-metal arc welding using primary human small airway epithelial cells (hSAEC) and ToxTracker reporter murine stem cells, which track activation of six cancer-related pathways. Metal content (Fe, Mn, Ni, Cr) of the particles was relatively homogenous across particle size. The particles were not cytotoxic in reporter stem cells but stainless steel particles activated the Nrf2-dependent oxidative stress pathway. In hSAEC, both particle types induced time- and dose-dependent cytotoxicity, and stainless steel particles also increased generation of reactive oxygen species. The cellular metal content was higher for hSAEC compared to the reporter stem cells exposed to the same nominal dose. This was, in part, related to differences in particle agglomeration/sedimentation in the different cell media. Overall, our study showed differences in cytotoxicity and activation of cancer-related pathways between stainless and mild steel welding particles. Moreover, our data emphasizes the need for careful assessment of the cellular dose when comparing studies using different in vitro models.
The growing field of MOF–catalyst composites often relies on postsynthetic modifications for the installation of active sites. In the resulting MOFs, the spatial distribution of the inserted ...catalysts has far-reaching ramifications for the performance of the system and thus needs to be precisely determined. Herein, we report the application of a scanning nuclear microprobe for accurate and nondestructive depth profiling of individual UiO-66 and UiO-67 (UiO = Universitetet i Oslo) single crystals. Initial optimization work using native UiO-66 crystals yielded a microbeam method which avoided beam damage, while subsequent analysis of Zr/Hf mixed-metal UiO-66 crystals demonstrated the potential of the method to obtain high-resolution depth profiles. The microbeam method was further used to analyze the depth distribution of postsynthetically introduced organic moieties, revealing either core–shell or uniform incorporation can be obtained depending on the size of the introduced molecule, as well as the number of carboxylate binding groups. Finally, the spatial distribution of platinum centers that were postsynthetically installed in the bpy binding pockets of UiO-67-bpy (bpy = 5,5′-dicarboxyy-2,2′-bipyridine) was analyzed by microbeam and contextualized. We expect that the method presented herein will be applicable for characterizing a wide variety of MOFs subjected to postsynthetic modifications and provide information crucial for their optimization as functional materials.
Multicomponent TixNbCrAl nitride films were deposited on Si(100) substrates by reactive direct current magnetron sputtering (dcMS) and high power impulse magnetron sputtering (HiPIMS) in the absence ...of substrate heating and bias. Three single Ti, Nb, and Cr50Al50 targets were either driven by three dc or three HiPIMS power supplies. The Ti content in the films was varied by tuning the power applied to the Ti target. The composition was determined by ion beam analysis. The nitrogen content is nearly stoichiometric (48–50 at.%) in the HiPIMS series, while the dcMS are understoichiometric (39–45 at.%). The crystal structure, stress and density of the studied film were investigated by X-ray techniques and the microstructure was examined by scanning electron microscopy. All the Ti-containing films for both series exhibit an fcc NaCl-type phase structure. In particular, the dcMS series shows a (111) preferred orientation, resulting in a faceted surface morphology compared to a dense and smooth microstructure of the HiPIMS films. The compressive stress of the HiPIMS series (> 2.0 GPa) is significantly larger than the values of the dcMS series (<0.5 GPa). Nanoindentation measurements show a maximum hardness of 29.9 GPa and Young's modulus of 304 GPa were obtained in the HiPIMS series. The results may promote HiPIMS techniques for the synthesis of complex multicomponent films for the application aspect to protective and hard coatings.
•Multicomponent TixNbCrAl nitride films were deposited by dcMS and HiPIMS.•Nitrogen content is nearly stoichiometric in the HiPIMS series, while being understoichiometric in the dcMS films.•The density, compressive stress, and hardness of the HiPIMS series are higher than the dcMS series.•The HiPIMS samples showed one order of magnitude lower corrosion rate than the dcMS samples in 0.1 M NaCl solution.
Direct growth of orthorhombic Ta3N5-type Ta-O-N compound thin films, specifically Ta3-xN5-yOy, on Si and sapphire substrates with various atomic fractions is realized by unbalanced magnetron ...sputtering. Low-degree fiber-textural Ta3-xN5-yOy films were grown through reactive sputtering of Ta in a gas mixture of N2, Ar, and O2 with keeping a partial pressure ratio of 3:2:0.1 in a total working pressure range of 5–30 mTorr. With increasing total pressure from 5 to 30 mTorr, the atomic fraction of O in the as-grown Ta3-xN5-yOy films was found to increase from 0.02 to 0.15 while that of N and Ta decrease from 0.66 to 0.54 and 0.33 to 0.31, respectively, leading to a decrease in b lattice constant up to around 1.3%. Metallic TaNx phases were formed without oxygen. For a working pressure of 40 mTorr, an amorphous, O-rich Ta-N-O compound film with a high O fraction of ~0.48, was formed, mixed with non-stoichiometric TaON and Ta2O5. By analyzing the plasma discharge, the increasing O incorporation is associated with oxide formation on top of the Ta target due to a higher reactivity of Ta with O than with N. The increase of O incorporation in the films also leads to a optical bandgap widening from ~2.22 to ~2.96 eV, which is in agreement with the compositional and structural changes from a crystalline Ta3-xN5-yOy to an amorphous O-rich Ta-O-N compound.
•Direct growth of orthorhombic Ta3-xN5-yOy compounds with various atomic fractions by unbalanced magnetron sputtering.•A simple method to control oxygen incorporation in the films by adjusting total working pressure.•Structure, chemical composition, and optical properties of as-grown films are highly dependent on incorporated oxygen.•No pure orthorhombic Ta3N5 phase was formed when the film was grown in a gas mixture of Ar and N2 without O2.
We present a thorough experimental study of electronic stopping of H, He, B, N, Ne and Al ions in TiN with the aim to learn about the energy loss mechanisms of slow ions. The energy loss was measured ...by means of time-of-flight medium-energy ion scattering. Thin films of TiN on silicon with a δ-layer of W at the TiN/Si interface were used as targets. We compare our results to non-linear density functional theory calculations, examining electron-hole pair excitations by screened ions in a free electron gas in the static limit, with a density equivalent to the expected value for TiN. These calculations predict oscillations in the electronic stopping power for increasing atomic number Z1 of the projectile. An increasing discrepancy between our experimental results and predictions by theory for increasing Z1 was observed. This observation can be attributed to contributions from energy loss channels different from electron-hole pair excitation in binary Coulomb collisions.
Determining the sequence of inks in a questioned document is important in forensic science. Conventional and micro beam‐based ion beam analysis using Rutherford backscattering spectrometry (RBS) and ...particle‐induced X‐ray emission were employed to study the depth distribution of chemical elements in plain paper and inks/toner deposited by different pens as well as inkjet and laser printers. Composition depth profiling with high lateral resolution was performed with focus on areas where two different coloring agents overlapped. We identify under which conditions the sequence of inks deposited can be reconstructed, analyzing the continuity of characteristic contributions to the obtained signals, with a focus on the depth‐resolved RBS data. The order of deposition was correctly determined for combinations of two different laser printers and in certain cases for pens. Results indicate a potential for analysis, depending on the composition of staining agent, that is, in particular if heavy species are present in sufficiently high concentration. In such cases, also characters obscured or modified by an agent of different composition can be revealed. Changing the probing depth by modifying the beam energy could yield additional information.
•Simultaneous high-resolution depth-profiling and crystallography.•Experiments can be performed in backscattering or transmission geometries.•Ion fraction of scattered particles can be ...measured.•Thermal annealing can be performed in-situ.•Spectrometry of electrons or desorbed particles can be performed.
We present the most recent upgrades of the time-of-flight medium energy ion scattering (TOF-MEIS) system in Uppsala. The experimental chamber features a 6-axis goniometer with a sample annealing stage and two delay line detectors for composition analysis with high depth resolution and depth-resolved crystallography. The first detector has a large solid angle and can be moved circularly around the target position which allows to detect backscattered or transmitted ions. The second detector features increased flight distance from sample to detector resulting in enhanced energy resolution. A reduction from 1.4 keV to 0.4 keV is achieved for 100 keV He scattered from an Au surface for 1 ns time resolution, equivalent to a depth resolution of 6 Å. This detector is equipped with an electrostatic electrode in order to deflect charged particles, which allows to study the charge state for scattered ions in the medium energy regime.
Si (100) wafers were implanted at 500 °C with 250 keV As ions and 350 keV In ions in this order. The implantations were carried out with three different fluences, namely 1 × 1016, 2 × 1016, and 5 × ...1016 cm−2. The samples were annealed with rapid thermal annealing (RTA) for 30 s at temperatures ranging from 800 up to 1000 °C. Different techniques like photoluminescence (PL) and Rutherford backscattering spectrometry (RBS) were employed to characterize the samples. Finally, scanning and transmission electron microscopy (SEM and TEM, respectively) provided further structural information of the InAs nanoclusters. The results indicate that InAs nanoprecipitates are formed after RTA treatment. Moreover, a broad photoluminescence peak was observed in all samples submitted to RTA. RBS results reveal that losses of implanted ions due to diffusion processes can be minimized through the use of RTA, depending of the fluence of ion implantation. Finally, the present results suggest that the photoluminescence yield depends on the degree of the radiation damage induced in the Si matrix during the implantation process.
Multicomponent or high-entropy ceramics show unique combinations of mechanical, electrical, and chemical properties of importance in coating applications. However, generalizing controllable thin-film ...processes for these complex materials remains a challenge. Here, understoichiometric (TiZrTaMe)N1–x (Me = Hf, Nb, Mo, or Cr, 0.12 ≤ x ≤ 0.30) films were deposited on Si(100) substrates at 400 °C by reactive magnetron sputtering using single elemental targets. The influence of ion energy during film growth was investigated by varying the negative substrate bias voltage from ∼10 V (floating potential) to 130 V. The nitrogen content for the samples determined by elastic recoil detection analysis varied from 34.9 to 43.8 at. % (0.12 ≤ x ≤ 0.30), and the metal components were near-equimolar and not affected by the bias voltage. On increasing the substrate bias, the phase structures of (TiZrTaMe)N1–x (Me = Hf, Nb, or Mo) films evolved from a polycrystalline fcc phase to a (002) preferred orientation along with a change in surface morphology from faceted triangular features to a dense and smooth structure with nodular mounds. All the four series of (TiZrTaMe)N1–x (Me = Hf, Nb, Mo, or Cr) films exhibited increasing intrinsic stress with increasing negative bias. The maximum compressive stress reached ∼3.1 GPa in Hf- and Cr-containing films deposited at −130 V. The hardness reached a maximum value of 28.0 ± 1.0 GPa at a negative bias ≥100 V for all the four series of films. The effect of bias on the mechanical properties of (TiNbZrMe)N1–x films can thus guide the design of protective high-entropy nitride films.
PDF
