Correlations between residual stress and water diffusion in silica glass at low temperatures

Residual stress profiles in silica glass were measured after water diffusion treatment under 47.33 kPa (355 Torr) water vapor at 350°C and 650°C. Earlier, it was found that water solubility in silica glass exhibited peculiar time dependence: Solubility increased with time exceeding the normal water solubility expected from higher temperatures. Then, the water solubility decreased with time. It was hypothesized that the stress induced by water diffusion and its subsequent relaxation is responsible for the phenomenon. Residual surface stress generation in silica glass was found to correlate closely with surface hydroxyl concentration, systematically increasing until eventual surface stress relaxation results in stress decrease for treatments beyond 265 hours at 650°C. This observation validates previous theories of time dependent diffusivity in silica glass.     

Hybrid Hydrogen Home Storage for Decentralized Energy Autonomy

As the share of distributed renewable power generation increases, high electricity prices and low feed-in tariff rates encourage the generation of electricity for personal use. In the building sector, this has led to growing interest in energy self-sufficient buildings that feature battery and hydrogen storage capacities. In this study, we compare potential technology pathways for residential energy storage in terms of their economic performance by means of a temporal optimization model of the fully self-sufficient energy system of a single-family building, taking into account its residential occupancy patterns and thermal equipment. We show for the first time how heat integration with reversible solid oxide cells (rSOCs) and liquid organic hydrogen carriers (LOHCs) in high-efficiency, single-family buildings could, by 2030, enable the self-sufficient supply of electricity and heat at a yearly premium of 52% against electricity supplied by the grid. Compared to lithium-ion battery systems, the total annualized cost of a self-sufficient energy supply can be reduced by 80% through the thermal integration of LOHC reactors and rSOC systems.     

Universally applicable model for the quantitative determination of lake sediment composition using fourier transform infrared spectroscopy

Fourier transform infrared spectroscopy (FTIRS) can provide detailed information on organic and minerogenic constituents of sediment records. Based on a large number of sediment samples of varying age (0-340,000 yrs) and from very diverse lake settings in Antarctica, Argentina, Canada, Macedonia/Albania, Siberia, and Sweden, we have developed universally applicable calibration models for the quantitative determination of biogenic silica (BSi; n = 816), total inorganic carbon (TIC; n = 879), and total organic carbon (TOC; n = 3164) using FTIRS. These models are based on the differential absorbance of infrared radiation at specific wavelengths with varying concentrations of individual parameters, due to molecular vibrations associated with each parameter. The calibration models have low prediction errors and the predicted values are highly correlated with conventionally measured values (R = 0.94-0.99). Robustness tests indicate the accuracy of the newly developed FTIRS calibration models is similar to that of conventional geochemical analyses. Consequently FTIRS offers a useful and rapid alternative to conventional analyses for the quantitative determination of BSi, TIC, and TOC. The rapidity, cost-effectiveness, and small sample size required enables FTIRS determination of geochemical properties to be undertaken at higher resolutions than would otherwise be possible with the same resource allocation, thus providing crucial sedimentological information for climatic and environmental reconstructions.     

Modal Analysis of the GTD Diffraction Coefficients for the Half-Plane’s Edge

The GTD diffraction coefficients for the half-planes edge are obtained by a new semi-analytic approach: From the modal expansion of the Greens function of an acoustically soft or hard wedge the total field due an incident plane wave is derived by locating a line source at infinity and by transforming the incident line-source field to an incident plane-wave field. By means of the second Greens theorem and by using the bilinear form of the free-space Greens function, the scattered far field is obtained from the exact field values on the wedges flanks. The isolated edge-diffracted part can be identified as the difference between the far field scattered by a half plane and one half of the far field scattered by the entire plane. The obtained alternating and —in the classical sense— non-converging series are numerically evaluated by means of a linear (consistent) summation technique, and the comparison to Kellers result shows excellent agreement. The main advantage of this new method is that it can be applied to a certain class of more difficult problems (circular and elliptic cone, plane angular sector, etc.).     

A Facile Molecular Approach to Amorphous Nickel Pnictides and Their Reconstruction to Crystalline Potassium-Intercalated γ-NiOOHx Enabling High-Performance Electrocatalytic Water Oxidation and Selective Oxidation of 5-Hydroxymethylfurfural

The low-temperature molecular precursor approach can be beneficial to conventional solid-state methods, which require high temperatures and lead to relatively large crystalline particles. Herein, a novel, single-step, room-temperature preparation of amorphous nickel pnictide (NiE; EP, As) nanomaterials is reported, starting from NaOCE(dioxane)_n and NiBr₂(thf)_1.5. During application for the oxygen evolution reaction (OER), the pnictide anions leach, and both materials fully reconstruct into nickel(III/IV) oxide phases (similar to γ-NiOOH) comprising edge-sharing (NiO₆) layers with intercalated potassium ions and a d-spacing of 7.27 Å. Remarkably, the intercalated γ-NiOOH_x phases are nanocrystalline, unlike the amorphous nickel pnictide precatalysts. This unconventional reconstruction is fast and complete, which is ascribed to the amorphous nature of the nanostructured NiE precatalysts. The obtained γ-NiOOH_x can effectively catalyse the OER for 100 h at a high current density (400 mA cm⁻²) and achieves outstandingly high current densities (>600 mA cm⁻²) for the selective, value-added oxidation of 5-hydroxymethylfurfural (HMF). The NiP-derived γ-NiOOH_x shows a higher activity for both processes due to more available active sites. It is anticipated that the herein developed, effective, room-temperature molecular synthesis of amorphous nickel pnictide nanomaterials can be applied to other functional transition-metal pnictides.     

Flow Field Simulation and Measurement in Packed Beds Based on 4D-X-Ray Computed Tomography

X-ray computed tomography (XCT) combined with computational fluid dynamics (CFD) simulations have proved to be a powerful and versatile tool to describe fluids flow through packed bed systems. In this contribution, two examples of the application of XCT experiments to track the fluid flow and fluid penetration in packed bed systems are shown. The first one shows how geometrical information extracted from XCT measurements can be coupled to CFD simulations to assess fluid flows reliably. Here the example of a packed bed of three-dimensional (3D) printed cylindrical-shaped particles is considered. Finally, a short case study on the monitoring of the progress of the water penetration front in a packed bed composed of glass spheres using four-dimensional (4D) XCT imaging data is presented.