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On the long term oxidation behaviour of homogeneous Ni Fe Cu alloys for CO2 free aluminium electrowinning applications at 800C
Full text linkThe oxidation behaviour of homogeneous Ni29Fe56Cu15 wt. , Ni42Fe38Cu20 wt. and Ni60Fe30Cu10 wt. is investigated under 1 atm flux of high purity O 2 gas using thermogravimetry with respect to application as oxygen evolving anodes for aluminium electrolysis. Stable cubic oxidation behaviour was observed in Ni42Fe38Cu20 wt. and Ni60Fe30Cu10 wt. after 30 h and 264 h, respectively, with the former showing particular promise for electrowinning applications due to a tendency to form a well adhered scale consisting of approximately 70 NiFe2 O4 by thickness, as measured from EDX line scans. NiO dominated the scale of Ni60Fe30Cu10 wt. up to 272 h, showing worse scale adhesion and prominent intergranular oxidation of iron. Partially blistered regions of the scale locally increased NiO CuO formation in Ni42Fe38Cu20 wt. , evolved to become Cu Ni, Fe O spinel oxides over tim
Optimizing Aesthetic Appearance of Perovskite Solar Cells Using Color Filters
Full text linkThe significance of color aesthetics in photovoltaic PV modules gains importance, especially in design centric applications like building integrated PVs. Color filters based on distributed Bragg reflectors, consisting of alternating thin film layers of different refractive indices, can modify the appearance of standard silicon modules. This approach is also extended to optimize the color appearance of emerging PV technologies such as perovskite solar cells, which typically exhibit a less appealing gray brownish appearance. In this contribution, perovskite solar cell stacks combined with MorphoColor color filters are presented. Angular resolved reflectance simulations based on wave optics and ray tracing with experimental data are validated, and the color appearance from various viewing angles is evaluated. Additionally, the impact of individual layers on color appearance and the maximum achievable short circuit current density in the perovskite solar cell is investigated. By applying Bayesian optimization, the color distance is minimized to the targeted appearance. Tailoring the bridging layers between the color filter and the perovskite solar cell is found to strongly influence the color impression due to the coherently combined color filter and perovskite solar cell. The presented color optimization concept allows to customize the aesthetics of emerging PV thin film technologies such as perovskite solar cell
Simultaneous multi angle AR XANES for surface sensitive chemical speciation of gold nanolayers in wall painting replica
Full text linkWall paintings from the world heritage site Petra Jordan contain gilding remnants, which show various types of degradation. To investigate the deterioration processes as well as assess the conservation treatment, non destructive ND and non invasive NI analyses of the chemical species of gold are mandatory. In this work, simultaneous multi angle angle resolved X ray absorption near edge spectroscopy AR XANES measurements were performed to assess gold species variations in depth. Experimental validation proved the method to be successful in differentiating between gold species in nanolayered structures. Technical advantages and limitations of the method are discussed. The application of a conservation material containing Nano Gold Gel NGG applied underneath a gold layer to regenerate adhesion with its support layer was also examine
Revealing Catalyst Restructuring and Composition During Nitrate Electroreduction through Correlated Operando Microscopy and Spectroscopy
Full text linkElectrocatalysts alter their structure and composition during reaction, which can in turn create new active selective phases. Identifying these changes is crucial for determining how morphology controls catalytic properties but the mechanisms by which operating conditions shape the catalyst s working state are not yet fully understood. In this study, we show using correlated operando microscopy and spectroscopy that as well defined Cu2O cubes evolve under electrochemical nitrate reduction reaction conditions, distinct catalyst motifs are formed depending on the applied potential and the chemical environment. By further matching the timescales of morphological changes observed via electrochemical liquid cell transmission electron microscopy with time resolved chemical state information obtained from operando transmission soft X ray microscopy, hard X ray absorption spectroscopy and Raman spectroscopy, we reveal that Cu2O can be kinetically stabilized alongside metallic copper for extended durations under moderately reductive conditions due to surface hydroxide formation. Finally, we rationalize how the interaction between the electrolyte and the catalyst influences the ammonia selectivit
Prediction of Olivine Composition Under Limited Calibration Inputs Comparative Study of Mid Infrared Reflection, Raman Scattering, and Laser Induced Plasma Spectroscopies
No full textIn situ optical analytical spectroscopies offer great geochemical insights due to their capability to resolve the chemical composition of regolith surfaces of rocky celestial bodies. The use of suitable calibration targets improves the precision of mineral determination, which is of critical importance for short living, low mobility landers, and enables, in special cases, determination of elemental composition. We investigate the capabilities of three space relevant optical analytical techniques used for in situ mineralogical analysis, i.e., mid infrared reflection, Raman light scattering, and laser induced plasma spectroscopies, to predict the chemical composition of olivine under a limited calibration input, namely using two bulk samples of natural olivine, chemically close to the end members of the mineral group. We determine the accuracy of the forsterite numbers obtained with each technique and discuss the choice of calibration methods applicable to limited in situ calibration input, which are summarized in recommendations for space instrumentatio
Operando X Ray Tomoscopy of Laser Beam Welding
Full text linkThe phenomena occurring in a weld seam during advancement of a laser beam over a metallic component are still under dispute. The occurrence and evolution of porosity and the occasional blowout of melt need to be understood. Here, a recently developed X ray tomoscopy setup is applied, providing one hundred 3D images per second to capture the temporal evolution of the melt pool in an AlSi9Cu3 Fe die casting while a laser beam advances. The number of pores, their size, shape and distribution are quantified with 10 ms time resolution and reflect a complex dynamic pattern. Apart from conventional welding, a variant involving a dynamic beam modulation superimposed onto the linear motion is studied. Reductions of porosity and surface roughness are observed and explained by increased pore mobility and stepwise degassing as the beam repeatedly cuts through pores. The keyhole formed in the melt pool integrated over 10 ms is represented in 3
Unveiling the enzymatic pathway of UMG SP2 urethanase insights into polyurethane degradation at the atomic level
Full text linkThe recently discovered metagenomic urethanases UMG SP1, UMG SP2, and UMG SP3 have emerged as promising tools to establish a bio based recycling approach for polyurethane PU waste. These enzymes are capable of hydrolyzing urethane bonds in low molecular weight dicarbamates as well as in thermoplastic PU and the amide bond in polyamide employing a Ser Sercis Lys triad for catalysis, similar to members of the amidase signature protein superfamily. Understanding the catalytic mechanism of these urethanases is crucial for enhancing their enzymatic activity and improving PU bio recycling processes. In this study, we employed hybrid quantum mechanics molecular mechanics methods to delve into the catalytic machinery of the UMG SP2 urethanase in breaking down a model PU substrate. Our results indicate that the reaction proceeds in two stages STAGE 1 acylation, in which the enzyme becomes covalently bound to the PU substrate, releasing an alcohol leaving group; STAGE 2 deacylation, in which a catalytic water hydrolyzes the enzyme ligand covalent adduct, releasing the product in the form of a highly unstable carbamic acid, expected to rapidly decompose into an amine and carbon dioxide. We found that STAGE 1 comprises the rate limiting step of the overall reaction, consisting of the cleavage of the substrate s urethane bond by its ester moiety and the release of the alcohol leaving group overall Gibbs activation energy of 20.8 kcal mol amp; 8722;1 . Lastly, we identified point mutations that are expected to enhance the enzyme s turnover for the hydrolysis of urethane bonds by stabilizing the macrodipole of the rate limiting transition state. These findings expand our current knowledge of urethanases and homolog enzymes from the amidase signature superfamily, paving the way for future research on improving the enzymatic depolymerization of PU plastic material
Towards an EPR on a Chip Spectrometer for Monitoring Radiation Damage During X ray Absorption Spectroscopy
Full text linkElectron paramagnetic resonance EPR spectroscopy is an essential tool to investigate the effects of ionizing radiation, which is routinely administered for reducing contaminations and waste in food products and cosmetics as well as for sterilization in industry and medicine. In materials research, EPR methods are not only employed as a spectroscopic method of structural investigations, but also have been employed for detection of changes in electronic structure due to radiation damage from high energy X rays, for example, to monitor radical formation inside biomolecules caused by X ray irradiation at carbon, nitrogen, and oxygen K edges at synchrotron facilities. Here a compact EPR spectrometer, based on EPR on a chip EPRoC sensor and a portable electromagnet, has been developed as a solution for monitoring radiation damage of samples during their investigation by X ray absorption spectroscopy XAS at synchrotron facilities. A portable electromagnet with a soft iron core and forced air temperature stabilization was constructed as the source of the external magnetic field. The sweep range of magnetic field inside the most homogeneous region of the portable electromagnet is 12 290 mT. The compact spectrometer performance was evaluated by placing the EPRoC sensor inside either a commercial electromagnet or the portable electromagnet to record the EPR spectrum of tempol, irradiated alanine, and dilithium phthalocyanine Li2Pc . The potential performance of the portable spectrometer for the detection of radiation damage in organic compounds and transition metal containing catalysts during XAS measurements in both fluorescence and transmission modes was calculated with promising implications for measurements after implementation in a synchrotron based XAS spectromete
Texture Enhanced Mechanical Stability of Transparent Electrodes for Flexible Optoelectronics with Near Infrared Response
Full text linkTransparent electrodes with high conductivity and mechanical robustness are essential for flexible opto electronic applications. Indium tin oxide ITO single layers have long been considered as unsuitable for flexible applications due to their brittleness. Here, it is shown that their mechanical stability can be substantially enhanced by texturing the flexible substrate. First, the opto electronic performance of single ITO layers and ITO Ag ITO stacks on polyethylene terephthalate PET foils is evaluated numerically by means of Haacke s figure of merit. Single ITO layers are found to be the electrode of choice for applications with a near infrared response due to their superior transparency. Following this, the sheet resistance of ITO layers is experimentally investigated on textured PET upon deformation parallel and perpendicular to a 1D texture grating. An accordion like deformation perpendicular to the grating and high texture aspect ratios are shown to avoid crack formation and loss of conductivity in the ITO. Simulations prove the considerably reduced occurrence of mechanical stress in this case. It is further experimentally demonstrated that texturing foils increase transmittance and haze. The enhanced mechanical robustness and optical performance by using textured foils make single ITO layers promising candidates for flexible opto electronic applications with a near infrared response, such as all perovskite tandem solar cells, thermal sensors, and photodetector
New Gold I Complexes as Potential Precursors for Gas Assisted Methods Structure, Volatility, Thermal Stability, and Electron Sensitivity
No full textWe report the synthesis and characterization of new, user friendly gold I [Au4 amp; 956; NH 2CC2F5 4]n coordination polymer and [Au2Cl2 NH2 NH CC2F5 2]n complex. These compounds were investigated for potential application as precursors in chemical vapor deposition CVD and focused electron ion beam induced deposition FEBID FIBID , which are additive methods to produce nanomaterials. Single crystal X ray diffraction, elemental analysis, and infrared spectroscopy were used to determine the complexes composition and structure. We studied their thermal stability and volatility using thermal analysis and variable temperature infrared spectroscopy VT IR and by conducting sublimation experiments. The gold I amidinate [Au2 amp; 956; NH 2CC2F5 2]n sublimates at 413 K under 10 amp; 8722;2 mbar pressure. The electron induced decomposition of the complexes molecules in the gas phase and of their thin layers on silicon substrates was analyzed using electron impact mass spectrometry EI MS and microscopy studies SEM EDX , respectively, to provide insights for FEBID and FIBID precursor design. The [Au2Cl2 NH2 NH CC2F5 2]n hydrogen chloride molecules evolved during heating, with the formation of gold I amidinate. The obtained results revealed that the new gold I amidinate may be a promising source of metal for nanomaterial fabrication by gas assisted method