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Quantification of Interfacial Charges in Multilayered Nanocapacitors by Operando Electron Holography
Get PDFInterfaces in heterostructures play a major role in the functionality of electronic devices. Phenomena such as charge trapping detrapping at interfaces under electric field affect the dynamics of metal oxide metal capacitors and metal oxide semiconductor transistors used for memory and logic applications. Charge traps are also key for the stabilization of a ferroelectric polarization and its ability to switch in ferroelectric devices such as ferroelectric tunnel junctions FTJs . However, electric field induced charging phenomena remain unclear even in conventional dielectric heterostructures due to a lack of direct measurement methods. Here, it is shown how operando off axis electron holography can be used to quantify the charges trapped at the dielectric dielectric interfaces as well as metal dielectric interfaces in HfO2 and Al2O3 based nanocapacitors. By mapping the electrostatic potential at sub nanometer spatial resolution while applying a bias, it is demonstrated that these interfaces present a high density of trapped charges, which strongly influence the electric field distribution within the device. The unprecedented sensitivity of the electron holography experiments coupled with numerical simulations highlights for the first time the linear relationship between the trapped charges at each interface and the applied bias, and the effect of the trapped charges on the local electrical behavio
A sustainable delta MnO derived from Amazon rainforest Mn ore tailings for applications in lithium ion batteries
Get PDFThe transition to net zero emissions by 2050 necessitates the development of sustainable and efficient energy storage systems to complement the rise in renewable energy generation. Lithium ion batteries LiBs are pivotal in this energy transformation, yet challenges remain in developing sustainable, high performance materials. Manganese oxides MnO amp; 8339; are promising candidates for LiBs anodes due to their abundance and high theoretical capacity. However, the commercial synthesis of MnO amp; 8339; materials is resource intensive, and the mining processes generate large amounts of environmentally hazardous tailings. In this study, we propose a novel method to recover manganese from mining tailings in the Brazilian Amazon and synthesize amp; 948; MnO amp; 8322; as a high capacity conversion anode material for LIBs. Using a green recovery method involving KOH and H amp; 8322;O amp; 8322;, we extracted potassium manganate K amp; 8322;MnO amp; 8324; from the tailings with a recovery efficiency of 90.3 ,and synthesized amp; 948; MnO amp; 8322;. The prepared material showed promising electrochemical properties, demonstrating its potential as a sustainable alternative to commercially available manganese oxides. This process not only offers a way to mitigate the environmental risks posed by manganese mining tailings but also provides an economically viable solution for producing high performance battery materials. The developed methodology can be applied to other manganese bearing residues and low grade ores, contributing to the growing demand for battery grade manganese in a sustainable and circular manne
On Chip Planar Metasurfaces for Magnetic Sensors with Greatly Enhanced Sensitivity
Get PDFMetamaterials with engineered structures have been extensively investigated for their capability to manipulate optical, acoustic, or thermal waves. In particular, magnetic metamaterials with precise geometry, shape, size and arrangement of their elemental blocks may be used to concentrate, focus, or guide magnetic fields. In this work, we show the potential of using soft magnetic permalloy Py metasurfaces to tailor the physical properties of other magnetic structures at the local scale. As an illustration, the magnetic response of a Cobalt Co sensor bar placed at the core of a Py metasurface is investigated as a function of in plane magnetic fields through the planar Hall effect. Our findings reveal that by appropriately selecting the metasurface geometrical parameters, we can adjust the Co bar s coercive field and susceptibility, leading to a huge enhancement in sensor sensitivity of over 2 orders of magnitude. Micromagnetic simulations, coupled with magneto transport equations and X ray photoemission electron measurements XPEEM with contrast from magnetic circular dichroism XMCD , accurately capture this effect and provide insights into the underlying physical mechanisms. These findings can potentially enhance the performance and versatility of magnetic functional devices by using specifically designed structural magnetic material
In Situ Cw ESR Study on Redox Behavior and Phase Heterogeneity in ASite Deficient Lanthanum Iron Manganite Perovskite Catalysts
Get PDFTemperature dependent in situ continuous wave cw electron spin resonance ESR measurements are used for investigating changes in magnetization upon reduction and reoxidation in La deficient LaxFe0.7Mn0.3O3 x lt; 1 samples to advance the understanding of structural and chemical changes in these materials where A site deficiency was shown to affect catalytic performance. For these defect rich mixed perovskites with ferromagnetic ordering, the magnetic properties as characterized by in situ cw ESR spectroscopy are sensitive probes for structural changes in these materials. To this end, the ESR spectra observed in a redox cycle in H2 and O2 containing atmospheres not only show structural changes that were not observed by XRD but also provide evidence for heterogeneity in the magnetic phases, which notably depends on the La deficiency of the samples. This not only demonstrates the potential of such investigations for obtaining information complementary to other methods but also emphasizes the sensitivity of magnetic properties as probed by ESR to elucidate structural and chemical changes in such complex perovskite materials. While the XRD results lack indication for the presence of structural heterogeneity, STEM measurements provide evidence for a compositional heterogeneity between the grains but not for the presence of an additional magnetic phase, as observed by ESR for one of the samples. Importantly, the different magnetic phases exhibit distinct responses to reducing and re oxidizing atmospheres indicating for the sample with a lower La deficiency a facilitated reaction under reducing conditions at low temperatures but an overall higher structural stability. Both effects are expected to affect the reactivity in the redox reactions. Thus, these results provide new and complementary insights that can enhance the understanding of the effect of A site deficiency in perovskite materials in redox reactions considered to be important for the catalytic activity of these system
Fluctuation driven topological Hall effect in room temperature itinerant helimagnet Fe3Ga4
Get PDFThe topological Hall effect THE is a hallmark of a non trivial geometric spin arrangement in a magnetic metal, originating from a finite scalar spin chirality SSC . The associated Berry phase is often a consequence of non coplanar magnetic structures identified by multiple k vectors. For single k magnetic structures however with zero SSC, the emergence of a finite topological Hall signal presents a conceptual challenge. Here, we report that a fluctuation driven mechanism involving chiral magnons is responsible for the observed THE in a low symmetry compound, monoclinic Fe3Ga4. Through neutron scattering experiments, we discovered several nontrivial magnetic phases in this system. In our focus is the helical spiral phase at room temperature, which transforms into a transverse conical state in applied magnetic field, supporting a significant THE signal up to and above room temperature. Our work offers a fresh perspective in the search for novel materials with intertwined topological magnetic and transport propertie
Parchment preservation state of the Prayer book of Mary of Guelders
Get PDFIlluminated medieval manuscripts are of outstanding value and their preservation is of great importance, not only because of their beauty but also because of the information they contain about medieval society. This work focuses on the evaluation of the parchment s state of preservation of the Prayer book of Mary of Guelders, which comprises about 600 folios. The knowledge gained should support the decision making process regarding suitable conservation measures. An assessment of the preservation state of the parchment was performed from the macro down to the microscale. Optical observations of cracks in the parchment and colour measurements preceded chemical analyses. The hydrothermal stability of the fibres was evaluated by means of observations using a micro hot table MHT . The chemical state of preservation of parchment was evaluated using Laboratory based Fourier transform FT Infrared IR analysis in reflection mode as well as synchrotron FTIR imaging in transmission mode at the IRIS beamline at BESSY II HZB in Berlin. The study allowed the conclusion that the parchment of the Prayer book of Mary of Guelders was in good state of preservation and indicated that the parchment changes were mainly caused by mechanical stress on the folios due to tight binding of the book and not by chemical processe
The Heisenberg RIXS instrument at the European XFEL
Get PDFResonant inelastic X ray scattering RIXS is an ideal X ray spectroscopy method to push the combination of energy and time resolutions to the Fourier transform ultimate limit, because it is unaffected by the core hole lifetime energy broadening. Also, in pump probe experiments the interaction time is made very short by the same core hole lifetime. RIXS is very photon hungry so it takes great advantage from high repetition rate pulsed X ray sources like the European XFEL. The Heisenberg RIXS instrument is designed for RIXS experiments in the soft X ray range with energy resolution approaching the Fourier and the Heisenberg limits. It is based on a spherical grating with variable line spacing and a position sensitive 2D detector. Initially, two gratings were installed to adequately cover the whole photon energy range. With optimized spot size on the sample and small pixel detector the energy resolution can be better than 40 meV 90 meV at any photon energy below 1000 eV with the high resolution high transmission grating. At the SCS instrument of the European XFEL the spectrometer can be easily positioned thanks to air pads on a high quality floor, allowing the scattering angle to be continuously adjusted over the 65 145 range. It can be coupled to two different sample interaction chambers, one for liquid jets and one for solids, each state of the art equipped and compatible for optical laser pumping in collinear geometry. The measured performances, in terms of energy resolution and count rate on the detector, closely match design expectations. The Heisenberg RIXS instrument has been open to public users since the summer of 202
Design and manufacture of structure function integrated carbon fiber reinforced plastics for composite construction
No full textStructure function integrated composite can replace traditional structural components to bear loads, offering an innovative solution to reduce overall weight while storing energy in aircraft composite wings. The structural electrolyte featuring high ionic conductivity and tough mechanical properties is one of the vital components to realize high performance multifunctional structural composite batteries. Herein, a functional ternary hydrogel electrolyte i.e., MAP electrolyte is elaborately engineered through the strategical incorporation of multiple hydrogen bonding among polyacrylamide PAM with rigid reinforcing aramid nanofibers ANFs and ion conductive Ti3C2Tx MXene nanosheets. Accordingly, the ANFs fortify the fracture toughness and self healing properties of MAP hydrogel, and the MXene enables a doubled ionic conductivity of MAP electrolyte 32.48 mS cm 1 than that of pure PAM 16.18 mS cm 1 . In addition, the capacity retention of the MAP based full cell 81.9 is double of the liquid electrolyte 40.6 within 1000 cycles at 1 A g 1 . Impressively, the MAP electrolyte remarkably enhances the flexural performance of structural batteries, with a flexural modulus 14.5 GPa nearly three times that of structural batteries with liquid electrolytes 5.3 GPa due to hydrogen bonded ANFs. Simulation results and mechanical electrochemical tests further underscore the imperative functions of MAP electrolyte as a structural component to empower the stiffness and maintain the integrity of structural batteries. Moreover, fabricating curved wing scaled components utilizing multi point flexible forming technology demonstrates the practical feasibility of replacing structural components with complex shapes. This work will expedite the exploitation of structural battery prototypes and their real applications in EVs, UAVs, and electric powered maritime vehicle
Towards Green Processing of Perovskite Solar Cells Protic Ionic Liquids Enable Water and Alcohol Based MAPbI3 Precursor Inks for Slot die Coating
No full textHalide perovskite solar cells are approaching commercialization, with solution processing emerging as a key method for large scale production. This study introduces a significant advancement using non toxic solvents like water and alcohol in perovskite precursor inks facilitated by the protic ionic liquid methylammonium propionate MAP . MAP effectively dissolves perovskite precursors such as lead acetate and methylammonium iodide, enabling the first stable water based perovskite precursor ink suitable for one step slot die coating. This new ink formulation contrasts with conventional dimethylformamide DMF and dimethylsulfoxide DMSO based inks, as evidenced by in situ grazing incidence wide angle X ray scattering GIWAXS , which revealed an intermediate free liquid to solid transition. In situ mass spectrometry also showed that organic molecules evaporate during annealing, resulting in a crystalline perovskite phase. Optimization of the solvent mixture to H2O IPA MAP enabled successful slot die coating, yielding perovskite solar cells with an efficiency of up to 10 . This eco friendly ink reduces toxicity and environmental impact compared to DMF based inks, offering a longer shelf life and the possibility of using the ink in ambient conditions. This pioneering work represents the first report of a water based green ink formulation for one step thin film coating at room temperature conditions by slot die coating, highlighting its potential for sustainable commercial application
Role of graphene substrate in the formation of MoS2 based nanoparticles with improved sensitivity to NO2 gas
No full textMoS2 coatings were formed on surface oxidized silicon, chemical vapor deposition CVD grown graphene, and reduced fluorinated graphene rFG from ammonium tetrathiomolybdate. The samples were annealed under ultra high vacuum conditions at a temperature of 1000 C. Analysis of X ray photoelectron and X ray absorption spectra revealed a bonding between MoS2 and the supporting material that was particularly strong for CVD graphene. Uniform covering of the flat CVD graphene surface with MoS2 nanoparticles and numerous contacts between them promoted the removal of sulfur and the formation of exposed molybdenum edges. A cracked MoS2 coating consisting of dense domains was formed on the wrinkled rFG surface. The study of samples as NO2 gas sensors revealed the best performance of MoS2 CVD graphene. The sensor detected NO2 in air below 50 ppb at room temperature, had good response and recovery, operated in humid air, and demonstrated excellent NO2 selectivity. The other two sensors gave signals at elevated temperatures. The advantage of MoS2 CVD graphene is due to improved electron transport in the hybrid, accessibility of small MoS2 nanoparticles to the analyte, and passivation of high energy molybdenum sites by oxygen, which improves NO2 desorptio