Role of solute in stress development of nanocrystalline films during heating: An in situ synchrotron X-ray diffraction study

The effect of the solute (Mo) on the stress development of nanocrystalline Ni and Ni–Mo films upon heating has been investigated in real time using in situ synchrotron X-ray diffraction. The complex and distinct relationship between the film stress and grain boundaries (GBs) has been examined by the evolution of real-time intrinsic stress in combination with the in situ grain growth and thermal characterizations. The different intrinsic stress evolutions in the Ni and Ni–Mo films during the heating process result from the modification of GBs by Mo alloying, including GB amorphization, GB relaxation, and GB segregation. It has been found that GBs play a vital role in the stress development of nanocrystalline films. The addition of a solute can not only inhibit grain growth but also influence the stress evolution in the film by changing the atomic diffusivity at the GBs. This work provides valuable and unique insights into the effect of solutes on stress development in nanocrystalline films during annealing, permitting control of the film stress through solute addition and heat treatment, which is critical for improving the design, processing, and lifetime of advanced nanocrystalline film devices at high temperatures

Water is a radiation protection agent for ionised pyrrole

Radiation-induced damage of biological matter is an ubiquitous problem in nature. The influence of the hydration environment is widely discussed, but its exact role remains elusive. Utilising well defined solvated-molecule aggregates, we experimentally observed a hydrogen-bonded water molecule acting as a radiation protection agent for ionised pyrrole, a prototypical aromatic biomolecule. Pure samples of pyrrole and pyrrole(H$_2$O) were outer-valence ionised and the subsequent damage and relaxation processes were studied. Bare pyrrole ions fragmented through the breaking of C$-$C or N$-$C covalent bonds. However, for pyrrole(H$_2$O)$^+$, we observed a strong protection of the pyrrole ring through the dissociative release of neutral water or by transferring an electron or proton across the hydrogen bond. Overall, a single water molecule strongly reduces the fragmentation probability and thus the persistent radiation damage of singly-ionised pyrrole

Exploring optimal Li composite electrode anodes for lithium metal batteries through in situ X-ray computed tomography

The uncontrolled Li dissolution/deposition dynamics and rapid Li pulverizations hinder the widespread deployment of Li metal batteries (LMB). Designing a Li composite electrode possessing a mechanically robust and lithiophilic three-dimensional (3D) framework represents a promising strategy to address these challenges. This study involves the preparation of three uniquely tailored Li-B-Mg composites using a combined metallurgical process of melting, casting, and rolling, along with the synergistic application of in situ X-ray computed tomography (CT) and post-mortem failure analysis to explore the most promising composite electrode candidate for LMBs. During the in-depth investigation, the optimal 70Li-B-Mg composite electrode stands out due to its robust skeleton fiber structure, uniform Li dissolution/deposition characteristics and high capacity of free-Li. Its promising prospects for enabling high-performance LMBs are showcased by the superior performance of the built Li||O2, Li||LiFePO$_4$, Li||NCM622 and Li||NCM811 battery systems. This work offers a novel approach for exploring universally applicable and robust Li composite electrodes to realize high-performance LMBs using in situ CT analysis

Optical Absorption Properties in Pentacene/Tetracene Solid Solutions

Modifying the optical and electronic properties of crystalline organic thin films is of great interest for improving the performance of modern organic semiconductor devices. Therein, the statistical mixing of molecules to form a solid solution provides an opportunity to fine-tune optical and electronic properties. Unfortunately, the diversity of intermolecular interactions renders mixed organic crystals highly complex, and a holistic picture is still lacking. Here, we report a study of the optical absorption properties in solid solutions of pentacene and tetracene, two prototypical organic semiconductors. In the mixtures, the optical properties can be continuously modified by statistical mixing at the molecular level. Comparison with time-dependent density functional theory calculations on occupationally disordered clusters unravels the electronic origin of the low energy optical transitions. The disorder partially relaxes the selection rules, leading to additional optical transitions that manifest as optical broadening. Furthermore, the contribution of diabatic charge-transfer states is modified in the mixtures, reducing the observed splitting in the 0–0 vibronic transition. Additional comparisons with other blended systems generalize our results and indicate that changes in the polarizability of the molecular environment in organic thin-film blends induce shifts in the absorption spectrum

MnO2_2 superstructure cathode with boosted zinc ion intercalation for aqueous zinc ion batteries

The simultaneous intercalation of protons and Zn$^{2+}$ ions in aqueous electrolytes presents a significant obstacle to the widespread adoption of aqueous zinc ion batteries (AZIBs) for large-scale use, a challenge that has yet to be overcome. To address this, we have developed a MnO$_2$/tetramethylammonium (TMA) superstructure with an enlarged interlayer spacing, designed specifically to control H$^+$/Zn$^{2+}$ co-intercalation in AZIBs. Within this superstructure, the pre-intercalated TMA+ ions work as spacers to stabilize the layered structure of MnO$_2$ cathodes and expand the interlayer spacing substantially by 28 % to 0.92 nm. Evidence from in operando pH measurements, in operando synchrotron X-ray diffraction, and X-ray absorption spectroscopy shows that the enlarged interlayer spacing facilitates the diffusion and intercalation of Zn$^{2+}$ ions (which have a large ionic radius) into the MnO$_2$ cathodes. This spacing also helps suppress the competing H$^{+}$ intercalation and the formation of detrimental Zn$_4$(OH)$_6$SO$_4$·5H$_2$O, thereby enhancing the structural stability of MnO$_2$. As a result, enhanced Zn$^{2+}$ storage properties, including excellent capacity and long cycle stability, are achieved

Synthesis of a helical boron-doped PAH by post-functionalization of 3,9-diboraperylene

We present herein the post-functionalization of doubly boron-doped polycyclic aromatic hydrocarbons (PAHs) by various aryl substituents, namely the syntheses of a series of (2,8,)3,9-aryl-substituted 3,9-diboraperylenes via boron-substitution of (2,8-diaryl-)3,9-dihydroxy-3,9-diboraperylenes. These new boron-doped PAHs exhibit two reversible reductions with a remarkably facile first reduction between E = −1.04 and −1.13 V vs. Fc$^+$/Fc. Friedel–Crafts cyclization of the 2-isopropenylnaphthyl-substituted derivative afforded a helical boron-doped polycyclic aromatic hydrocarbon that is endowed with a low LUMO level, high absorption coefficients and fluorescence (Φ$_F$ = 0.73), combined with a one-dimensional π–π stacking interaction in the solid state

Microplasticity and macroplasticity behavior of additively manufactured Al-Mg-Sc-Zr alloys: in-situ experiment and modeling

Understanding and controlling the performance of additively manufactured aluminum alloys containing scandium (Sc) and zirconium (Zr) elements heavily relies on knowledge of their microplasticity and macroplasticity behavior. However, this aspect has received very little attention. In this investigation, we examined the microplasticity and macroplasticity behavior of additively manufactured Al-Mg-Sc-Zr alloys before and after aging, using in-situ synchrotron X-ray diffraction and full-field crystal plasticity modeling. Our study provides a quantitative assessment of the transitions from elasticity to microplasticity and then to macroplasticity and analyzes the development of the initial microstructure, particularly the dislocations. We constructed crystal plasticity fast-Fourier-transform models based on dislocation densities. The predicted evolutions of macroscopic stress-strain curves, lattice strains, and dislocation densities agree with in-situ measurements. The present findings provide deep insights into controlling the performance of AM Al-Mg-Sc-Zr alloys. Besides, the micromechanical model developed in this investigation paves the way for predicting the microplasticity and macroplasticity behavior of various metallic materials

Building Nitridic Networks with Phosphorus and Germanium–from GeIIP2_2N4_4 to GeIVPN3_3

Nitridophosphates and nitridogermanates attract high interest in current research due to their structural versatility. Herein, the elastic properties of GeP$_2$N$_4$ were investigated by single-crystal X-ray diffraction (XRD) upon compression to 44.4(1) GPa in a diamond anvil cell. Its isothermal bulk modulus was determined to be 82(6) GPa. At 44.4(1) GPa, laser heating resulted in the formation of multiple crystalline phases, one of which was identified as unprecedented germanium nitridophosphate GePN$_3$. Its structure was elucidated from single-crystal XRD data (C2/c (no. 15), a = 8.666(5), b = 8.076(4), c = 4.691(2) Å, β = 101.00(7)°) and is built up from layers of GeN6 octahedra and PN$_4$ tetrahedra. The GeN$_6$ octahedra form double zigzag chains, while the PN4 tetrahedra are found in single zigzag chains. GePN$_3$ can be recovered to ambient conditions with a unit cell volume increase of about 12%. It combines P$^V$ and Ge$^{IV}$ in a condensed nitridic network for the first time

Evidence for Exclusive Direct Mechanism of Urea Electro-Oxidation Driven by In Situ- Generated Resilient Active Species on a Rare-Earth Nickelate

Stabilization of active NiOOH species for achieving exclusive operationof the direct mechanism of the urea electro-oxidation reaction (UOR) presents aformidable challenge. Despite the extensive repertoire of UOR electrocatalystsdeveloped so far, the sustenance of active NiOOH species throughout the reactionremains unaccomplished due to the predominant operation of the indirect mechanismthat involves the reduction of NiOOH into Ni(OH)2 during electrocatalysis. Thecapability of a UOR electrocatalyst to retain the active species is of paramountimportance as it ensures the optimal engagement of the maximum pool of active Nicenters in the electrocatalytic process, resulting in enhanced activity with reduced Nimass loading. In this context, the present study unveils the electrocatalytic UORcapability of a rare-earth nickelate, NdNiO3, showcasing high UOR activity with areduced burden of Ni mass loading. From the detailed cyclic voltammetry studies, in situX-ray absorption spectroscopy, and impedance analyses, it has been substantiated that NdNiO3 triggers the UOR to proceed throughthe unconventional direct mechanism, obviating the need for catalyst regeneration during UOR. The adsorption free energycalculation of reactants such as urea, OH− ions, and product CO2 reveals that NdNiO3 effectively interacts with the reactants, and itssurface is highly tolerant toward COx poison when compared to NiO. The preferential direct mechanism of UOR, enhanced massactivity, and commendable resistance against COx poisons emanate from the more facile formation and effective stabilization ofactive NiOOH species on NdNiO3

Exploring the Potential of Nitride and Carbonitride MAX Phases: Synthesis, Magnetic and Electrical Transport Properties of V2_2GeC, V2_2GeC0.5_{0.5}N0.5_{0.5}, and V2_2GeN

The chemical composition variety of MAX phases is rapidly evolving in many different directions, especially with the synthesis of carbides that contain two or more metals on the M-site of these layered solids. However, nitride and carbonitride MAX phases are still underrepresented, and only a few members have been reported that are for the most part barely characterized, particularly in terms of magnetic and electronic properties. Here, we demonstrate a simple and effective synthesis route, as well as a comprehensive characterization of three MAX phases, (i) V$_2$GeC, (ii) the hitherto unknown carbonitride V$_2$GeC$_{0.5}$N$_{0.5}$, and (iii) the almost unexplored nitride V$_2$GeN. By combining a microwave-assisted precursor synthesis with conventional heat treatment and densification by spark plasma sintering, almost phase-pure (carbo)nitride products are obtained. Magnetic measurements reveal an antiferromagnetic-paramagnetic-like phase transition for all samples in the temperature range of 160–200 K. In addition, increasing the amount of nitrogen on the X-site of the MAX phase structure leads to a constant increase in the magnetic susceptibilities while the electrical resistivity is constantly decreasing. Overall, these findings provide crucial insights into how to tune the electronic and magnetic properties of MAX phases by only varying the chemical composition of the X-site. This further substantiates the demand for (carbo)nitride research with the potential to be extended to the remaining elemental sites within the MAX phase structure to push toward controlled material design and to achieve desired functional properties, such as ferromagnetism