OCT capillary depth measurement in copper micro welding using green lasers. - In: Applied Sciences, ISSN 2076-3417, Bd. 11 (2021), 6, 2655, S. 1-15
The transition of the powertrain from combustion to electric systems increases the demand for reliable copper connections. For such applications, laser welding has become a key technology. Due to the complexity of laser welding, especially at micro welding with small weld seam dimensions and short process times, reliable in-line process monitoring has proven to be difficult. By using a green laser with a wavelength of [lambda] = 515 nm, the welding process of copper benefits from an increased absorption, resulting in a shallow and stable deep penetration welding process. This opens up new possibilities for the process monitoring. In this contribution, the monitoring of the capillary depth in micro copper welding, with welding depth of up to 1 mm, was performed coaxially using an optical coherence tomography (OCT) system. By comparing the measured capillary depth and the actual welding depth, a good correlation between two measured values could be shown independently of the investigated process parameters and stability. Measuring the capillary depth allows a direct determination of the present aspect ratio in the welding process. For deep penetration welding, aspect ratios as low as 0.35 could be shown. By using an additional scanning system to superimpose the welding motion with a spacial oscillating of the OCT beam perpendicular to the welding motion, multiple information about the process could be determined. Using this method, several process information can be measured simultaneously and is shown for the weld seam width exemplarily.
https://doi.org/10.3390/app11062655
Welche Verfahren für welche Anwendungen? : Schweißen von Strukturkomponenten aus Aluminium: Lichtbogen-, Laserstrahl- oder Rührreibschweißen. - In: Der Praktiker, ISSN 0554-9965, Bd. 73 (2021), 3, S. 98-101
Hydroxyapatite-coated SPIONs and their influence on cytokine release. - In: International journal of molecular sciences, ISSN 1422-0067, Bd. 22 (2021), 8, 4143, S. 1-19
Richtiger Name des 7. Verfassers: Aldo R. Boccacccini
Hydroxyapatite- or calcium phosphate-coated iron oxide nanoparticles have a high potential for use in many biomedical applications. In this study, a co-precipitation method for the synthesis of hydroxyapatite-coated nanoparticles (SPIONHAp), was used. The produced nanoparticles have been characterized by dynamic light scattering, X-ray diffraction, vibrating sample magnetometry, Fourier transform infrared spectrometry, atomic emission spectroscopy, scanning electron microscopy, transmission electron microscopy, selected area diffraction, and energy-dispersive X-ray spectroscopy. The results showed a successful synthesis of 190 nm sized particles and their stable coating, resulting in SPIONHAp. Potential cytotoxic effects of SPIONHAp on EL4, THP-1, and Jurkat cells were tested, showing only a minor effect on cell viability at the highest tested concentration (400 [my]g Fe/mL). The results further showed that hydroxyapatite-coated SPIONs can induce minor TNF-α and IL-6 release by murine macrophages at a concentration of 100 [my]g Fe/mL. To investigate if and how such particles interact with other substances that modulate the immune response, SPIONHAp-treated macrophages were incubated with LPS (lipopolysaccharides) and dexamethasone. We found that cytokine release in response to these potent pro- and anti-inflammatory agents was modulated in the presence of SPIONHAp. Knowledge of this behavior is important for the management of inflammatory processes following in vivo applications of this type of SPIONs.
https://doi.org/10.3390/ijms22084143
Molecular dynamics in ionic liquid/radical systems. - In: The journal of physical chemistry, ISSN 1520-5207, Bd. 125 (2021), 18, S. 4850-4862
Molecular dynamics of the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)imide (Emim-Tf2N) with either of the four organic stable radicals, TEMPO, 4-benzoyloxy-TEMPO, BDPA, and DPPH, is studied by using Nuclear Magnetic Resonance (NMR) and Dynamic Nuclear Polarization (DNP). In complex fluids at ambient temperature, NMR signal enhancement by DNP is frequently obtained by a combination of several mechanisms, where the Overhauser effect and solid effect are the most common. Understanding the interactions of free radicals with ionic liquid molecules is of particular significance due to their complex dynamics in these systems, influencing the properties of the ion-radical interaction. A combined analysis of EPR, DNP, and NMR relaxation dispersion is carried out for cations and anions containing, respectively, the NMR active nuclei 1H or 19F. Depending on the size and the chemical properties of the radical, different interaction processes are distinguished, namely, the Overhauser effect and solid effect, driven by dominating dipolar or scalar interactions. The resulting NMR relaxation dispersion is decomposed into rotational and translational contributions, allowing the identification of the corresponding correlation times of motion and interactions. The influence of electron relaxation time and electron-nuclear spin hyperfine coupling is discussed.
https://doi.org/10.1021/acs.jpcb.1c02118
Quantitative interpretation of UWB radar images for non-invasive tissue temperature estimation during hyperthermia. - In: Diagnostics, ISSN 2075-4418, Bd. 11 (2021), 5, 818, insges. 16 S.
The knowledge of temperature distribution inside the tissue to be treated is essential for patient safety, workflow and clinical outcomes of thermal therapies. Microwave imaging represents a promising approach for non-invasive tissue temperature monitoring during hyperthermia treatment. In the present paper, a methodology for quantitative non-invasive tissue temperature estimation based on ultra-wideband (UWB) radar imaging in the microwave frequency range is described. The capabilities of the proposed method are demonstrated by experiments with liquid phantoms and three-dimensional (3D) Delay-and-Sum beamforming algorithms. The results of our investigation show that the methodology can be applied for detection and estimation of the temperature induced dielectric properties change.
https://doi.org/10.3390/diagnostics11050818
Preparation and gas-sensing properties of very thin sputtered NiO films. - In: Journal of electrical engineering, ISSN 1339-309X, Bd. 72 (2021), 1, S. 61-65
We present results on very thin NiO films which are able to detect 3 ppm of acetone, toluene and n-butyl acetate in synthetic air and to operate at 300˚C. NiO films with 25 and 50 nm thicknesses were prepared by dc reactive magnetron sputtering on alumina substrates previously coated by Pt layers as heater and as interdigitated electrodes. Annealed NiO films are indexed to the (fcc) crystalline structure of NiO and their calculated grain sizes are in the range from 22 to 27 nm. Surface morphology of the examined samples was influenced by a rough and compact granular structure of alumina substrate. Nanoporous NiO film is formed by an agglomeration of small grains with different shapes while they are created on every alumina grain.
https://doi.org/10.2478/jee-2021-0009
Electrostatic control of Au nanorod formation in automated microsegmented flow synthesis. - In: ACS applied nano materials, ISSN 2574-0970, Bd. 4 (2021), 2, S. 1411-1419
An automated flow rate program was applied for the synthesis of gold nanorods of different aspect ratios dependent on a two-dimensional concentration space of reducing agent and additional silver ions. It was found a regular redshift of the spectral position of the electromagnetic in-axis resonance of metal nanorods with decreasing concentration of reducing agent and increasing concentration of silver ions. The increase of resonance wavelength is strongly correlated with the aspect ratio of the formed nanorods. The experimental results agree with an electrostatic model of self-polarization due to positive excess charge of the nanorods in the presence of CTAB and confirm the crucial role of electrostatic control in the formation of nonspherical and composed nanoparticles in general.
https://doi.org/10.1021/acsanm.0c02941
Recent advances in ferromagnetic metal sulfides and selenides as anodes for sodium- and potassium-ion batteries. - In: Journal of materials chemistry, ISSN 2050-7496, Bd. 9 (2021), 15, S. 9506-9534
In next-generation rechargeable batteries, sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) have been considered as attractive alternatives to lithium-ion batteries due to their cost competitiveness. Anodes with complicated electrochemical mechanisms determine the performance and safety of battery systems to a large degree. Among a wide range of anode materials for SIBs and PIBs, ferromagnetic metal (Fe, Co, and Ni) sulfides and selenides have captured prominent attention by virtue of their high theoretical capacities, suitable potentials, and relatively low price. Although some breakthrough results have been achieved, a few intrinsic issues stemming from the materials themselves need to be further explored and studied, especially in the field of PIBs, an emerging research interest. Herein, in this review, we highlight the pioneering investigation of typical ferromagnetic metal sulfides and selenides for application as anodes in SIBs and PIBs and overview their recent research progress. Meanwhile, the preparation methods, structural characteristics, charge storage mechanisms, and electrochemical properties are outlined. Finally, the present challenges and research perspectives are discussed.
https://doi.org/10.1039/D1TA00831E
Chemical changes of float glass surfaces induced by different sand particles and mineralogical phases. - In: Journal of non-crystalline solids, ISSN 0022-3093, Bd. 566 (2021), 120868
Particles play an important role in the storage, transportation and natural weathering of glasses, but their influence on glass degradation is little studied. In this work, the influence of main sand components is investigated. Feldspar exhibits the strongest leaching rate for the network former Na, while quartz has the lowest. The leaching rate of natural sands is in between. Based on these findings, a model describing the leaching mechanism was developed: Hereby, hydroxyl groups adhering on sand grains adsorb network modifiers by substituting their hydrogen by network formers from the glass surface. The amount of available hydroxyl groups determines the leaching rate. This model is supported by loss on ignition performed for the sands, which might be a suitable method to roughly estimate their leaching rates. The adsorption of network modifiers suppresses carbonate formation, dendritic growth and Mg diffusion in the glass surface region. Pimple-like crystal growth is observed.
https://doi.org/10.1016/j.jnoncrysol.2021.120868
Quantifying crude oil contamination in sand and soil by EPR spectroscopy. - In: Applied magnetic resonance, ISSN 1613-7507, Bd. 52 (2021), 5, S. 633-648
Crude oil frequently contains stable radicals that allow detection by means of EPR spectroscopy. On the other hand, most sands and soils possess significant amounts of iron, manganese or other metallic species that often provide excessively broad EPR signatures combined with well-defined sharp features by quartz defects. In this study, we demonstrate the feasibility to identify oil contamination in natural environments that are subject to oil spillage during production on land, as well as beachside accumulation of marine oil spillage. Straightforward identification of oil is enabled by the radical contributions of asphaltenes, in particular by vanadyl multiplets that are absent from natural soils. This potentially allows for high-throughput soil analysis or the application of mobile EPR scanners.
https://doi.org/10.1007/s00723-021-01331-4