267649 research outputs found
Sort by
Evaluating the predictive capabilities of part-scale residual stress simulations of PBF-LB/M up to crack formation by a comparison to neutron diffraction
No full textAdditive manufacturing technologies have proven to be an excellent alternative to conventional production methods, especially when geometrically complex parts and low production quantities are aimed at. Specifically, powder bed fusion of metals using a laser beam (PBF-LB/M) additionally allows for the manufacturing of mechanically highly stressable parts. However, the heat input through the laser beam into the material and an irregular cooling during the processing result in the formation of high residual stresses. These lead to form deviations outside the specified tolerances and may accumulate to an extent, at which stress-induced cracking occurs. This emphasizes the need for an accurate prediction of the residual stresses during the PBF-LB/M process with the goal of a first-time-right additive manufacturing. In this study, three specimens exhibiting high residual stress formations during PBF-LB/M were manufactured from the nickel-based superalloy Inconel 718. Afterwards, the stresses were measured by means of neutron diffraction. The results provided the validation data for a subsequent finite element simulation, representing the build-up process on a part-scale, in which the data evaluation was conducted in accordance with the measurements for a high comparability. A comparison between the simulation and the neutron diffraction results of all three specimens showed a very good agreement of the normal stresses in all three coordinate directions, both for tensile and compressive stresses. The obtained results highlight the validity of the applied simplified part-scale simulation. The latter can, therefore, be utilized to increase the process understanding of residual stress and crack formations. It can also be used to enable process parameter modifications or geometry adaptions, aiming at a first-time-right additive manufacturing
Quaternised cellulosic materials prepared from chain-growth polymerisation of a grafted reactive ionic liquid
No full textNeutron transmission studies with GdCl for tracing concentration polarization in reverse osmosis
No full textConcentration polarization (CP) is determined by neutron transmission in a reverse osmosis (RO) system consisting of two cells, one with and the other without an RO membrane, to get the net neutron response for the feed solution in front and far from the membrane separately. The aqueous feed was a dilute solution of NaCl and GdCl3. The special feature of these experiments is that GdCl3 can be selectively determined with neutrons, since the neutron absorption cross-section of Gd is larger orders of magnitude compared to other elements such as Na, Cl, and water, and therefore has a strong influence on the overall transparency of the sample for neutrons. It is therefore the transmission of neutrons through both cells (one with and the other without membrane), by which the concentration and CP of GdCl3 can be determined. Transmission and small-angle scattering (SANS) were measured in parallel, demonstrating the performance of this method as an in-situ method for determining CP as a function of time under near-realistic conditions. The neutron experiments are complemented by measurements of permeate flux and electrical conductivity of the feed, which were used to determine the salt concentrations, the osmotic pressure and the concentration polarization of the two salts individually and of a mixture of both. The CP results of this study are in good agreement with the values presented in the literature, determined mainly from flux data under a wide variety of conditions
The affinity towards the hydrophobic region of biomimicking bacterial membranes drives the antimicrobial activity of EFV12 peptide from Lactobacillus gasseri gut microbiota
No full textThe gut microbiota consists of a large variety of microorganisms, which interact with the immune system and exert essential roles for the human body health. Many of these microorganisms are also capable of producing various bioactive molecules, such as selective antimicrobial peptides, thus promoting the proliferation of only certain bacterial strains. These result in the shaping of the composition of the local microbiome and the co-evolution with a complex microbiome. Recently, a small peptide, named EFV12 and deriving from the bacterium Lactobacillus gasseri SF1109 regularly placed in the human intestine, showed a significant antimicrobial activity. Here we discuss a biophysical study on the structural changes induced by the peptide on lipid bilayers mimicking bacterial membranes with the aim of shedding light on the molecular features driving the biocidal activity against Gram(+) and Gram(−) strains. Supported Lipid Bilayers and liposomes composed of 1,2-oleoyl-sn-glycero-3-phosphocholine and 1,2-oleoyl-sn-glycero-3-rac-phosphoglycerol, both in the absence and presence of cardiolipin and lipopolysaccharides (LPSs), were selected to investigate the peptide-lipid interactions through a combination of specular Neutron Reflectometry, Dynamic Light Scattering, Small-Angle X-ray Scattering and Circular Dichroism measurements. The obtained results indicated association of EFV12 peptide with the hydrophobic region of lipid bilayers, which caused their destabilization, and is thus driving the antimicrobial activity against bacterial cells
AEgIS experiment at CERN: design and commissioning of SARA (Scintillator Assemblies to Reveal Annihilations)
No full textSARA is the system of plastic scintillators coupled with silicon photomultipliers that will take part in the AEgIS experiment at CERN, measuring the time-of-flight of antihydrogen as it falls through a moiré deflectometer. Its development focused on simplicity, versatility and economy of the design and was supported by both physical tests and numerical simulations. The instrument structure pairs the utilization of the scintillators as structural components with custom made 3D printed corner elements and the electronics allows selection between coincidence discrimination made on each scintillator and made between different scintillators
Spin dynamics of germanium diluted ferrimagnetic spinel MnCoO
No full textWe report a detailed structure and spin dynamics in two different insulating polycrystalline spinels of varying Ge and Fe contents in cubic MnCo2O4 (MCO). The stoichiometry of the investigated system being (Ge0.1Mn0.9)(Fe0.2Co1.8)O4 [G1F2] and (Ge0.2Mn0.8)(Fe0.4Co1.6)O4 [G2F4]. Both systems exhibit robust ferrimagnetic (FiM) characteristics with enhanced Curie temperature as high as TC ∼ 240 K in comparison to the pristine MCO (TC ∼ 180 K). The FiM ordering is predominantly due to the different temperature dependence of the cationic moments resulting in the effective magnetic moment = 7.36 μB/f.u. (7.1 μB/f.u. for G2F4) for G1F2. However, just below the TC both of these mixed spinels show frequency dispersion in ac-susceptibility that demonstrates the re-entrant spin-glass signatures with the freezing temperature TSG = 206 K (234.8 for G2F4) for G1F2 below TC. Formation of tiny magnetic clusters of size D ∼ 10–12 nm were probed by means of modified Langevin's expression involving M-H isotherms. Using the Néel's two-sublattice model we have extracted the strength of exchange interactions: JAA/kB ∼ −19.12 K (−25.05 K), JBB/kB ∼ 2.79 K (10.512 K), and JAB/kB ∼ 4.4 K (5.76 K) for both the systems G1F2 (G2F4). Within a certain temperature window (TH1) both compounds exhibit unusual hysteresis behaviour as the magneto crystalline anisotropy field (HK) exceeds to the coercivity (HC) for T < TH1 and becomes negligible beyond TH1
Synthesis of PtCu/C Nanostructured Electrocatalysts for the Oxygen Reduction Reaction via One-Step Electrochemical Erosion
No full textReducing the precious metal loading while increasing the oxygen reduction reaction (ORR) mass activity of novel electrocatalysts constitutes one of the remaining key challenges in the widespread application of proton exchange membrane fuel cells, which is inevitable for the transition to the climate-neutral hydrogen economy. However, this requires a simple, scalable, and affordable production of active nanostructured electrocatalysts. Alloyed nanoparticles of Platinum (Pt) with transition metals like cobalt, nickel, or copper have shown promising activity toward ORR, but their preparation usually involves complex multistep processes and environmentally harmful surfactants or structure-capping agents. In this work, we present the successful synthesis of nonspherical copper-alloyed Pt nanoparticles (PtCu) by employing a simple one-step top-down approach without surfactants or capping agents. The electrocatalysts were characterized by high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and inductively coupled plasma mass spectrometry. The ORR kinetics were evaluated using the rotating (ring) disk electrode technique. The synthesized PtCu/C catalysts revealed outstanding mass activities of ∼1.2 A mgPt–1 at 0.9 V vs the reversible hydrogen electrode, which clearly surpasses state-of-the-art Pt-based catalysts in the literature and demonstrates the highest ORR mass activities reported for PtCu nanoparticles
Glass-ceramics and molybdenum doping synergistic approach for Nasicon-type solid-state electrolytes
No full textAdvancing energy density, enabling lithium metal anodes, and ensuring unparalleled safety and operational reliability in lithium batteries hinge on advancing inorganic solid-state electrolytes. To overcome current im-pediments, we present an innovative approach that integrates glass-ceramics with a pioneering new Nasicon strategy involving molybdenum doping. In the conducted study, a series of 14Li2O-9Al2O3-38TiO2-(39-x)P2O5- xMoO3 glasses, denoted as LATPMox, along with their corresponding glass-ceramics (LATPMox-GC), have exhibited a promising characteristic as solid electrolytes. X-ray diffraction (XRD) analysis confirms the formation of the novel Mo-doped Nasicon phases in the glass-ceramics, as validated by Rietveld refinement. Examination of the crystallization kinetic behavior of the glasses reveals a three-dimensional nucleation process with spherical particle growth, featuring an activation energy of 165 kJ mol-1. Transmission Electron Microscopy TEM char-acterization aligns crystallization behavior with crystallite and distribution within the glass matrix, resulting in a compact and dense microstructure. The structural properties of the resultant phases are examined through FT-IR, Raman spectroscopy, and TEM-SEAD analysis. Vickers indentation tests were employed to assess the microscopic fracture toughness, and both the glass and glass-ceramics materials demonstrated favorable mechanical per-formance. Optical characterization using UV–visible absorption highlights the reduction of Mo6+ to Mo5+, likely occupying tetrahedral sites within the crystalline lattice. Impedance spectroscopy measurement showcases the effective promotion of ionic conductivity following Mo doping, reaching a total conductivity value of 5.50 × 10-5 Ω-1 cm-1 along with a high lithium transference number of 0.99 at room temperature for LATPMo2.6-GC glass-ceramic. This value is larger than that of many other glass-ceramics as well as that of the well-known lithium phosphorous oxy-nitride LiPON solid electrolyte whose ionic conductivity at RT is around 2 × 10-6 Ω-1 cm-1
Controlling the Cold-Set Gelation of Bovine Serum Albumin Protein using Alcohol and Ionic Surfactant
No full textHeating of globular protein solutions usually leads to protein denaturation and subsequent gelation at high temperatures. Under “cold gelation”, protein forms a gel at a much lower temperature than its original gelation temperature (TG), which can be achieved by modifying various physicochemical conditions such as the pH of the solution, the presence of salts, etc. In this study, we investigated the cold gelation of Bovine Serum Albumin (BSA) protein induced by ethanol and controlled by ionic surfactant, using small-angle neutron scattering (SANS), dynamic light scattering (DLS), and rheology The results show that the TG of the protein with ethanol is systematically decreased as compared to the that of pure BSA solutions (~80 ◦C), reaching ~60 ◦C at 10 wt% ethanol, ~55 ◦C at 20 wt% and finally as low as ~38 ◦C in presence of 30 wt% ethanol in the solution. Rheo-logical measurements demonstrate a significant strengthening of the gel network, with the enhancement in storage modulus (G′) from ~20 Pa at 0 wt% to ~250 Pa at 30 wt% ethanol. Structural characterization reveals an increase in fractal dimension with rising ethanol content, indicating denser and more branched gel networks. Interestingly, the addition of the anionic surfactant sodium dodecyl sulfate (SDS) inhibits the alcohol-assisted cold gelation of BSA protein, depending upon the relative amount of ethanol and SDS in solution. The results are explained based on the interplay of interactions in the protein, manipulated by the presence of alcohol, elevated temperatures, and ionic surfactant. Our study highlights the tunability of gelation pathways and offers useful inputs for controlled protein gelation in biomaterial and food industry
In situ high temperature X-ray diffraction and dilatometric analysis of CGO–Cu composites for solid oxide devices
No full textUnderstanding the thermo-mechanical compatibility of composite electrodes is essential for the longterm reliability of solid-oxide electrochemical devices. In this study, we demonstrate a combined in situ synchrotron X-ray diffraction (XRD) and simultaneous dilatometry approach as a rapid and predictive method to quantify both phase-resolved and bulk thermal expansion while tracking microstructural evolution at operational temperatures. Ce0.8Gd0.2O2−δ–Cu (CGO–Cu) composites with varying CGO:Cu ratios (39:61–70:30 vol%) were synthesized as potential anode materials compatible with CGO electrolytes up to 800 °C. In situ XRD confirmed only the CGO and Cu phases, with Rietveld refinement revealing a slight lattice expansion and reduced CGO crystallite size with increasing CGO content. Concurrent dilatometry indicated systematic changes in the macroscopic thermal expansion and densification behavior, which correlated with the phase and microstructural evolution observed during heating. The CGO–Cu (59:41) composite exhibited a nearly temperature-independent coefficient of thermal expansion consistent with the rule-of-mixtures predictions and minimal high-temperature shrinkage. These findings validate the combined in situ synchrotron XRD + dilatometry methodology as a powerful approach for characterizing and capturing the TEC characteristics of cermets, and for guiding the design of thermomechanically compatible oxide-metal composites for high temperatureelectrochemical applications