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

GSAG:Ce scintillator: insights from yttrium admixture

The GSAG:Ce scintillator represents a promising and cost-effective alternative to the expensive GGAG:Ce.Recent studies have attributed its low light yield to the thermal quenching effect. In this study, we employedthe strategy of adding an yttrium (Y) admixture to the GSAG matrix to increase the thermal activation energyof thermal quenching. The scintillation, optical, and luminescence properties of Gd$_{(3−x)}$YxSc$_2$Al$_3$O$_{12}$:Ce (x = 0,0.2, 0.5, 0.8) grown using the micro-pulling-down method are thoroughly studied and reported. We furtherinvestigated the correlation between the Y content and other characteristics (scintillation rise time, light yield,decay, etc.). The magnitude of thermal quenching was evidenced by combination of the temperaturedependentphotoluminescence decay kinetics and thermally stimulated luminescence. Excitation spectrawere measured down to 30 nm in the VUV range under the synchrotron radiation at DESY to monitor theenergy transfer efficiency from the host under excitation above the band gap. Results suggested that thermalionization was not the primary reason for the low performance of the GSAG:Ce composition, and otherdefects related to the presence of scandium (Sc) must play a role. Furthermore, it was found that thestoichiometric GSAG host provided a noticeably higher light yield than the previously studied congruent one.This research provides valuable insights into the characteristics of GSAG:Ce scintillators

Kinematic power corrections to DVCS to twist-six accuracy

We calculate $(\sqrt{-t}/Q)^k$ and $(m/Q)^k$ power corrections with $k\le 4$, where $m$ is the target mass and $t$ is the momentum transfer, to several key observables in Deeply Virtual Compton Scattering (DVCS). We find that the power expansion is well convergent up to $|t|/Q^2\lesssim 1/4$ for most of the observables, but is naturally organized in terms of $1/(Q^2+t)$ rather than the nominal hard scale $1/Q^2$. We also argue that target mass corrections remain under control and do not endanger QCD factorization for coherent DVCS on nuclei. These results remove an important source of uncertainties due to the frame dependence and violation of electromagnetic Ward identities in the QCD predictions for the DVCS amplitudes in the leading-twist approximation

Segregation-guided alloy design via tailored solidification behavior

This study presents an alloy design perspective guided by elemental segregation during solidification to determine the site-specific chemistry and related local thermodynamic properties of dendritic microstructures. This was accomplished via manipulation of the microsegregation behavior by means of nominal alloy composition and thermal conditions of the solidification processes, including modified cooling rates spanning over six orders of magnitudes using ingot casting, directed energy deposition (DED-LB/M) additive manufacturing (AM) and laser powder bed fusion (PBF-LB/M) AM processes. Our approach was demonstrated by computationally designing a novel AlxCo25Fe(50-x)Ni25 multi-principal element alloy (MPEA) as a model system, employing a combination of CALPHAD, Scheil, and multiphase-field simulations, and by experimentally validating the resulting microstructure evolution. The lower Al content (x = 10.5) was designated to generate a supersaturated single-phase fcc matrix suitable for heat-treatments to trigger local phase transformations. The higher Al content (x = 14.5) was selected to define the size and morphology of dual-phase microstructures by controlling phase nucleation and growth through segregation during solidification. Our results showcased how selective enrichment of the desired elements in interdendritic regions can be employed to induce local phase transformations during solidification or post heat-treatments, while their size can be flexibly controlled by the degree of undercooling during solidification. The suggested segregation-guided design approach can be transferred to other alloy systems, enabling effective tuning of local functional, structural, kinetic, and, as shown in this study, thermodynamic properties of dendritic microstructures by predetermining the nature of the alloy matrix through tailored solidification behavior

Search for new resonances decaying to pairs of merged diphotons in proton-proton collisions at s\sqrt{s} = 13 TeV

A search is presented for an extended Higgs sector with two new particles, X and $\phi$, in the process X $\to$$\phi\phi$$\to$$(\gamma\gamma)(\gamma\gamma)$. Novel neural networks classify events with diphotons that are merged and determine the diphoton masses. The search uses LHC proton-proton collision data at $\sqrt{s}$ = 13 TeV collected with the CMS detector, corresponding to an integrated luminosity of 138 fb$^{-1}$. No evidence of such resonances is seen. Upper limits are set on the production cross section versus the resonance masses, representing the most sensitive search in this channel

Measurability of Wigner time delay in a photoionization experiment

We visit significant historical steps in quantum collision physics that make photoionization time delay measurable, especially considering the time-reversal symmetry in related processes. The works of A. Ravi P. Rau and Ugo Fano inspire key ideas presented in this article

Elpasolite-type superstructures in inverse perovskite nitrides

We present a range of inverse perovskite nitrides with an elpasolite-type superstructure. (Ca3N0.682(9))Sn and (Ca3N0.559(7))Pb are variants of the previously described (Ca3N)Sn and (Ca3N)Pb which contain less nitrogen and crystallize in . (Ba3N0.5)Sn and (Ba3N0.5)Pb resemble the previously reported perovskites (Ba3Nx)Sn and (Ba3Nx)Pb, but with both the superstructure and octahedral tilting, resulting in space group . (Ca3N0.77(2))Si, (Ca3N0.669(6))Ge, (Sr3N0.5)Ge and (Ba3N0.5)Ge all crystallize in P21/n. Among these, only (Ca3Nx)Ge has been previously described as (Ca3N)Ge. (Ca3N0.77(2))Si is notably the first compound in which mutually isolated N3− and Si4− ions coexist. There also exists a version with composition (Ca3N0.86(6))Si, which crystallizes in the cubic perovskite aristotype structure with space group . Similarly, there are versions of (Sr3N0.5)Ge, (Ba3N0.5)Sn and (Ba3N0.5)Pb with elevated nitrogen contents, less strongly tilted octahedra and no apparent superstructure. Electronic structure calculations indicate a metallic nature of the title compounds, with rather narrow improper band gaps for the strontium and barium compounds

Measurements of Gravitational Attractions at small Accelerations

Gravitational interactions were studied by measuring the influence of small external field masses on a microwave resonator. It consisted of two spherical mirrors, which acted as independent pendulumsindividually suspended by strings. Two identical field masses weremoved along the axis of the resonator symmetrically and periodically betweena near and a far position. Their gravitational interaction altered the distance between the mirrors, changing the resonance frequency, which was measured and found consistent with Newton's law of gravity. The acceleration of a single mirror caused by the two field masses at the closest position varied from $5.4 10^{-12} m/s^2$ to $259 10^{-12}\ m/s^2$