Iron-based superconductors (IBS) such as FeSe0.5Te0.5 (Fe(Se,Te)) are highly promising for applications in high magnetic fields and low temperatures, allowing their adoption in liquid helium at fields exceeding 20 T. In these regimes, while high-temperature superconductors (HTS) exhibit superior performance, IBS materials offer advantages, including a large critical grain-boundary angle that reduces the need for strict texturing, making them strong candidates for coated conductors. Fe(Se,Te) films can be deposited under less extreme conditions compared to HTS, simplifying manufacturing and making Fe(Se,Te)-based coated conductors a cost-effective alternative for large-scale production. Recently, we demonstrated that a thin TiN film serves as an effective buffer layer, enabling the oriented growth of superconducting Fe(Se,Te) on biaxially textured Ni-W. This leads to a simple coated conductor architecture, fabricated using pulsed laser deposition, based on a single electrically conducting buffer layer. The resulting tape exhibits normal-state resistivity comparable to that of the substrate, proving the electrical connection that allows the substrate itself to function as an intrinsic stabilizer. In this work, we analyze the microstructure of the TiN-based tape via TEM, elucidating the Fe(Se,Te) growth mechanism on the mismatched TiN buffer layer and investigating the micro- and nanostructure of the superconducting film. Depending on deposition conditions, the formation of a nanostructured hexagonal secondary phase (SP) was detected, contributing to an effective pinning landscape. This results in high critical current densities (JC), exceeding 0.1 MA cm-2 at 4.2 K in magnetic fields up to 17.5 T and around 3.2 MA cm-2 at 4.2 K in self-field. The angular dependence of the critical current density reveals a quasi-isotropic behavior, attributed to the presence of the nanosized SP, contributing to uniformly distributed pinning centers within the superconducting matrix. These findings represent significant advancements in process simplification and performance of Fe(Se,Te)-based coated conductors, further reinforcing the potential of IBS-coated conductors for applications.

An unexplored approach for the improvement of the flux pinning of YBa2Cu3O7-x(YBCO) superconducting films grown by pulsed laser deposition (PLD) on SrTiO3 single-crystals is presented. Hence, substrate-decorated ZrO2 nanoislands combined with Ba2Y(Nb/Ta)O6 nanocolumns were engineered into YBCO films. The nanoislands produced a high density of pinning centres. In this synergistic combined pinning scenario, an absence of a temperature scaling pinning force, Fp(H) behaviour was observed, confirming several pinning mechanisms are active in the system. Thus, the high density of stacking faults and BYTO nanocolumns were both shown to be effective for high field pinning at <50K. Further optimisation of the densities and volumes of each pinning type is expected to produce enhanced high field (>9 T) pinning behaviour.

Ir/terpyridine-based solid molecular catalysts facilitate efficient base-free formic acid dehydrogenation both in batch and continuous operation. A kinetic isotope effect study highlights β-hydride elimination as a rate-determining step.

This work describes the fabrication of long-length YBa2Cu3O7-delta (YBCO)-coated conductors via chemical solution deposition starting with colloidal BaHfO3 nanocrystals with different surface functionalization. Two types of stabilization ligands, such as phosphonic and carboxylic acids, are explored in this work to emphasize the crucial role of nanocrystal surface chemistry in the nucleation, growth, and superconducting properties of YBCO nanocomposite films. By investigation of the thermal decomposition of stabilization ligands and the YBCO precursor solution, the impact of ligands on the YBCO microstructure can be revealed. Increasing the nanocrystal concentration to enhance pinning properties was found to affect the nucleation mechanism due to unbalanced stoichiometry, resulting in the formation of more and new secondary phases such as BaO6P2. This indicates that the careful selection of stabilization ligands and process parameters is crucial to achieve superior pinning performance and superconducting properties in the YBCO nanocomposite films. This work presents the fabrication of YBCO-coated conductors via chemical solution deposition method using colloidal BaHfO3 nanocrystals with carboxylic and biphosphonic ligands. It highlights how ligand chemistry influences nucleation, growth, and microstructure. Increased nanocrystal content affects YBCO stoichiometry, forming additional secondary phases. Careful selection of ligands and processing conditions is essential for optimizing superconducting properties.

Interfacial phase change memory (iPCM) devices have been shown to switch with significantly reduced power consumption, compared with conventional phase-change memory devices. These iPCMs are based on a periodic structure of nanometer-sized layers of chalcogenides called a chalcogenide superlattice (CSL). Strong temperature increases have been observed within the CSL during the switching procedure, questioning the stability of the CSL structure. In this study, we conduct a detailed quantitative analysis to investigate the evolution of the structure and composition of the sputter-deposited GeTe-Sb2Te3 CSL upon a temperature increase using atom probe tomography. We find that GeTe-Sb2Te3 CSLs already feature significant interdiffusion during the synthesis, with a considerable fraction of Sb found in GeTe and Ge in Sb2Te3. Upon heating the atoms rearrange considerably and form layers of stable Ge2Sb2Te5 and Ge3Sb2Te6 phases, which can be described as a layered solid of GeTe and Sb2Te3 blocks, i.e., Ge2Sb2Te5 = 2 × GeTe + Sb2Te3, while Ge3Sb2Te6 = 3 × GeTe + Sb2Te3. Moreover, these layered solids form in such a way as to preserve and maximize the number of van der Waals (vdW)-like contacts. Interestingly, our electrothermal simulations indicate that the transformation of the original CSL structure into layered stacks of Ge2Sb2Te5 and Ge3Sb2Te6 will have a beneficial effect on device performance. Finally, we discuss the mechanism behind the interdiffusion and phase formation and its implications for iPCM devices. In doing so, the applicability of atom probe tomography to directly investigate intermixing and phase formation on the nanoscale in phase change and related memory devices is demonstrated.

[This corrects the article DOI: 10.1016/j.isci.2024.111032.].

It was reported in the literature that the influence of grain growth inhibitors (GGIs) on the WC grain growth during sintering of cemented carbides is related to the formation of complexions at WC/Co interfaces at temperatures of liquid-phase sintering. However, this viewpoint was not confirmed experimentally, as such complexions were found upon cooling after sintering. The influence of different grain growth inhibitors on the kinetics of WC coarsening in WC-10 wt% Co cemented carbides was investigated. The presence of complexions having a thickness of nearly 1 to 3 nm at WC/Co interfaces was established by STEM, EDX and HRTEM as a result of adding VC, Cr3C2 and TaC to WC + Co. WC grains in WC-Co cemented carbides containing Mo2C was characterized by the presence of near-surface layers of (W,Mo)C having a thickness of about 100 nm and absence of complexions at the WC/binder interface. The values of activation energies for all the GGIs except for Mo2C lie in the range typical for the solid-state diffusion-controlled processes, therefore, the solid-state diffusion of W and C atoms through the nm-thick complexions is presumably a limiting stage of WC coarsening. Considering the activation energy and distribution of heavy elements in the binder for the samples doped with Mo2C, one can assume that in the liquid binder containing dissolved W, C and Mo atoms, molybdenum suppresses the diffusion of tungsten atoms. Therefore, the rate of the tungsten atoms' diffusion in the liquid binder is likely to be a limiting stage of WC coarsening.

The design of iron-based coated conductors (IBS-CC) with a simplified architecture is possible thanks to the material properties that allow for milder requirements on the template crystalline quality. With respect to the state-of-the-art multilayered layout, it is possible to use a single buffer layer that remains necessary for protection and to promote the oriented growth of the superconducting film. In this work, Fe(Se,Te) films are grown via pulsed laser deposition (PLD) on commercial tapes using a single, chemically deposited, CeO2-based buffer layer, and interesting properties are obtained. In detail, the preparation and characterization of the buffer layer is presented, along with the detailed analysis of the Fe(Se,Te) current transport properties. The samples show superconducting transitions with T c 0 around 12 K and critical current densities of ∼0.1 MA cm -2 at 4.2 K at zero field. These results show that the design of a low-cost IBS-CC with a single chemical buffer layer is possible.

We investigated the integration of transient liquid-assisted growth (TLAG) approach for epitaxial YBa 2 Cu 3 O 7− x (YBCO) films by physical deposition methodologies (pulsed laser deposition (PLD)), as an additional opportunity for high-throughput growth of YBCO. As a prerequisite, highly flat and amorphous YBCO precursor films were deposited by PLD at temperatures below 400 °C on single-crystalline SrTiO 3 (STO) and LaMnO 3 (LMO)/STO, as well as industrial coated conductor architectures. Contrary to TLAG based on chemical solution deposition, where BaCO 3 elimination is a key factor for the YBCO growth, TLAG-PLD growth is controlled by the transformation of Ba–Cu–O (s) to a transient liquid. High-quality c -axis YBCO films were successfully grown on different substrates, as demonstrated by high-resolution x-ray diffraction and transmission electron microscopy. In-situ resistance measurements revealed that the growth rates around 1000 nm s −1 can be achieved, outperforming the capabilities of standard PLD growth of REBa 2 Cu 3 O 7 films by few orders of magnitude. Experimental conditions such as temperature, oxygen partial pressure, and heating ramp, were optimized to obtain critical temperature ( T c ) values up to 90 K. Critical current densities of 15 MA cm −2 at 5 K and 1.7 MA cm −2 at 77 K were obtained for YBCO films of 450 nm on LMO/STO.

It was recently shown that the introduction of nanodiamond (ND) into a superconducting metal-organic deposited YBa2Cu3O7-δ (YBCO) film produces an increase in critical current density in self-field conditions (B = 0 T). Such improvement appears to be due to the formation of denser and smoother films than the samples deposited without ND. This paper presents the work done to understand the role of ND during YBCO nucleation and growth. A detailed study on YBCO+ND films quenched at different temperatures of the crystallization process was carried out. Results showed that the reaction responsible for YBCO production appeared effectively affected by ND. In particular, ND stabilizes one of the YBCO precursors, BaF2(1-x)Ox, whose conversion into YBCO requires a prolonged time. Therefore, the YBCO nucleation is slowed down by ND and begins when the experimental conditions favor both thermodynamically and kinetically the formation of YBCO along the c-axis. This effect has important implications because the growth of a highly epitaxial c-axis YBCO film enables excellent superconducting performance.

Samples of submicron WC-Co-Re cemented carbide were produced and examined by different techniques. The microstructure of the samples is fine and extremely uniform indicating the strong inhibiting effect of Re with respect to the WC grain growth during liquid-phase sintering. Results of examination of hot hardness at a temperature of 500°C provide evidence for the significantly higher hardness value of the WC-Co-Re cemented carbide in comparison with that of a conventional submicron WC-Co grade. Studies of creep rates of WC-Co-Re and WC-Co cemented carbides at 800°C indicated dramatically improved high-temperature creep-resistance of the Re-containing cemented carbide. Carbide / binder grain boundaries in a FIB lamella prepared from the WC-Co-Re cemented carbide were examined by high-angle annular dark field scanning transmission electron microscopy and energy dispersive X-ray spectroscopy at a high resolution. Rhenium was found to segregate at the grain boundaries forming complexions of 2 to 3 atomic monolayers, which presumably consist of mixed W-Re carbide. Such complexions are believed to suppress the phenomena of grain boundary sliding at elevated temperatures and WC grain growth at sintering temperatures thus dramatically improving the high-temperature creep-resistance of the WC-Co-Re material in comparison with conventional WC-Co cemented carbide.

Journal Article A New Superstructure in Beam Sensitive Cathode Material Revealed by Multimodal STEM Combining ADF, iDPC and EDX Mapping Techniques Get access Maria Meledina, Maria Meledina Thermo Fisher Scientific, Materials & Structural Analysis, Eindhoven, the Netherlands Corresponding author: maria.meledina@thermofisher.com Search for other works by this author on: Oxford Academic Google Scholar Alexander Meledin, Alexander Meledin Thermo Fisher Scientific, Materials & Structural Analysis, Eindhoven, the Netherlands Search for other works by this author on: Oxford Academic Google Scholar Eric G T Bosch, Eric G T Bosch Thermo Fisher Scientific, Materials & Structural Analysis, Eindhoven, the Netherlands Search for other works by this author on: Oxford Academic Google Scholar Ivan Lazić, Ivan Lazić Thermo Fisher Scientific, Materials & Structural Analysis, Eindhoven, the Netherlands Search for other works by this author on: Oxford Academic Google Scholar Xiaochao Wu, Xiaochao Wu Institute of Inorganic Chemistry, RWTH Aachen University, Aachen, Germany Search for other works by this author on: Oxford Academic Google Scholar Ulrich Simon, Ulrich Simon Institute of Inorganic Chemistry, RWTH Aachen University, Aachen, Germany Search for other works by this author on: Oxford Academic Google Scholar Boy Markus, Boy Markus Thermo Fisher Scientific, Materials & Structural Analysis, Eindhoven, the Netherlands Search for other works by this author on: Oxford Academic Google Scholar Bert Freitag, Bert Freitag Thermo Fisher Scientific, Materials & Structural Analysis, Eindhoven, the Netherlands Search for other works by this author on: Oxford Academic Google Scholar Sorin Lazar, Sorin Lazar Thermo Fisher Scientific, Materials & Structural Analysis, Eindhoven, the Netherlands Search for other works by this author on: Oxford Academic Google Scholar Paolo Longo Paolo Longo Thermo Fisher Scientific, Materials & Structural Analysis, Eindhoven, the Netherlands Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 29, Issue Supplement_1, 1 August 2023, Pages 1764–1765, https://doi.org/10.1093/micmic/ozad067.912 Published: 22 July 2023

The fabrication of a Fe-based coated conductor (CC) becomes possible when Fe(Se,Te) is grown as an epitaxial film on a metallic oriented substrate. Thanks to the material’s low structural anisotropy, less strict requirements on the template microstructure allow for the design of a simplified CC architecture with respect to the REBCO multi-layered layout. This design, though, still requires a buffer layer to promote the oriented growth of the superconducting film and avoid diffusion from the metallic template. In this work, Fe(Se,Te) films are grown on chemically-deposited, CeO 2 -based buffer layers via pulsed laser deposition, and excellent properties are obtained when a Fe(Se,Te) seed layer is used. Among all the employed characterization techniques, transmission electron microscopy proved essential to determine the actual effect of the seed layer on the final film properties. Also, systematic investigation of the full current transport properties J ( θ , H , T ) is carried out: Fe(Se,Te) samples are obtained with sharp superconducting transitions around 16 K and critical current densities exceeding 1 MA cm −2 at 4.2 K in self-field. The in-field and angular behavior of the sample are in line with data from the literature. These results are the demonstration of the feasibility of a Fe-based CC, with all the relative advantages concerning process simplification and cost reduction.

Organoarsenic compounds are widely used as feed additives in the poultry industry. However, the release of organoarsenic-containing wastewater can cause serious poisoning to the ecosystem. For this reason, detection and adsorption of organic arsenic from wastewater is crucial but also very challenging. Here, the use of covalent organic frameworks (COFs) as fluorescence sensors and adsorbents for the detection and adsorption of organic arsenic from water has been investigated for the first time. Two isoreticular crystalline and highly porous sp2 carbon-conjugated COFs were synthesized, and amidoxime-functionalized via post-synthetic modification (PSM). The long-range order and pi-conjugated system ensure that both COFs act as fluorescent sensors for detecting the representative organic arsenic, roxarsone (ROX). The fluorescence quenching efficiencies of ROX on both COFs are over 98%. The limits of detection (LOD) for ROX by both COFs are estimated to be 6.5 and 12.3 nM. Additionally, the regular pores and the abundantly decorated amidoxime moiety exhibit extraordinary accessibility, which facilitates the adsorption of ROX. High adsorption capacities were obtained for both materials which amounts are up to 732 and 787 mg g-1. After five times of recycling, a negligible decrease in the adsorption capacity was noted, which reveals the excellent regeneration ability of those two amidoximefunctionalized COFs. These results indicate that the state-of-the-art sp2 carbon-conjugated amidoxime-functionalized COFs exhibit a high potential for the practical detection and adsorption of organoarsenic compounds from wastewater.

The N-doping of carbon nanotubes (CNTs) is widely accepted as an effective way to enhance the catalytic performance of CNT-supported Ni catalysts for CO2 methanation. To demonstrate, in a direct systematic comparison, the importance of N-doping for producing high-performance CO2 methanation catalysts, we developed two catalysts composed of 15 wt% Ni on pristine (Ni/CNT) and N-doped CNT (Ni/CNT-N) and correlated their catalytic performance with their properties. Compared to Ni/CNT, Ni/CNT-N achieved a higher X-CO2 of 81.2% with S-CH4 = 99.2% at a lower temperature of 400 C, exhibiting excellent stability over 48 h time-on-stream testing. Our comprehensive comparative study demonstrated that the N-doped CNT support featured a better distribution of the Ni sites that were strongly interacting with the support, even with atomically dispersed Ni being observed by HAADF-STEM. This higher dispersion, enabled by the anchoring sites provided by the N-doping, is one of the main reasons for the enhanced performance of Ni/CNT-N, because it increases the H2 uptake capacity.(C)022 Elsevier Ltd. All rights reserved.

Among other Fe-based superconductors, Fe(Se,Te) is particularly interesting because of the low structural anisotropy, large upper critical fields, low field dependence of the critical current density and low toxicity. It can also be grown as an epitaxial film on a metallic oriented substrate, making the fabrication of a Fe-based coated conductor (CC) possible. Less strict requirements on the template microstructure allow for the design of a simplified design compared to REBCO CCs. This design requires a buffer layer to promote the oriented growth of the superconducting film and avoid diffusion from the metallic template. In this work, CeO 2 based buffer layers are prepared on single crystals via two chemical deposition techniques, metal organic decomposition (MOD) and polymer assisted deposition (PAD). With the design of a suitable thermal treatment, it is possible to obtain oriented buffers with large flat grains and low values of surface roughness. Fe(Se,Te) films are deposited on these templates via laser deposition, and excellent samples are obtained when a Fe(Se,Te) seed layer is used to favour chemical matching with the buffer: sharp superconducting transitions around 16 K and critical current densities exceeding 1 MA cm − 2 at 4.2 K in self-field are observed. These results are the demonstration of the feasibility of a Fe-based CC architecture, with all the relative advantages concerning process simplification and cost reduction.

Stabilization of single metal atoms is a persistent challenge in heterogeneous catalysis. Especially supported late transitions metals are prone to undergo agglomeration to nanoparticles under reducing conditions. In this study, nitrogen-rich covalent triazine frameworks (CTFs) are used to immobilize iridium complexes. Upon reduction at 400 degrees C, immobilized Ir(acac)(COD) on CTF does not form nanoparticles but transforms into a highly active Ir single atom catalyst. The resulting catalyst systems outperforms both the immobilized complex and supported nanoparticles in the dehydrogenation of formic acid as probe reaction. This superior performance could be traced back to decisive changes of the coordination geometry positively influencing activity, selectivity and stability. Spectroscopic analysis reveals an increase of electron density on the cationic iridium site by donation from the CTF macroligand after removal of the organic ligand sphere from the Ir(acac)(COD) precursor complex upon reductive treatment. This work demonstrates the ability of nitrogen moieties to stabilize molecular metal species against agglomeration and opens avenues for catalysts design using isolated sites in high-temperature applications under reducing atmosphere.

Cuprate coated conductors are promising materials for the development of large-scale applications, having superior performance over other superconductors. Tailoring their vortex pinning landscape through nanostructure engineering is one of the major challenges to fulfill the specific application requirements. In this work, we have studied the influence of the growth temperature on the generation of intrinsic pinning defects in YBa 2 Cu 3 O 7− δ films grown by chemical solution deposition using low Ba precursor solutions. We have analysed the critical current density as a function of the temperature, applied magnetic field magnitude and orientation, J c ( T,H,θ ), to elucidate the nature and strength of pinning sites and correlate the microstructure of the films with their superconducting performance. An efficient pinning landscape consisting of stacking faults and associated nanostrain is naturally induced by simply tuning the growth temperature without the need to add artificial pinning sites. Samples grown at an optimized temperature of 750 °C show very high self-field J c values correlated with an overdoped state and improved J c ( T,H,θ ) performances.

We report a successful fabrication of long-length rolling-assisted biaxially-textured substrate-based coated conductors (CCs) via chemical solution deposition starting from colloidal YBa2Cu3O7-delta (YBCO) solutions containing 5 mol-% preformed BaMO3 (M = Hf, Zr) (BMO) nanocrystals. Partial optimization of the existing continuous reel-to-reel YBCO processing via design of experiments approach allowed us to obtain YBCO nanocomposites that retain 80%-90% self-field performance of the pristine CC and show a 10%-40% improvement of in-field critical current, which is only a moderate performance improvement compared to similar films on single-crystal substrates prepared on lab-scale. Based on x-ray diffraction and transmission electron microscopy studies, we attribute this to worsening of the YBCO texture and strong coarsening of BMO nanoparticles, particularly, BaZrO3, during processing. Possible process improvements to overcome these effects are discussed.

Ru catalyst nanoparticles were encapsulated into the pores of a Cr-based metal-organic framework (MOF)-MIL-101. The obtained material, as well as the non-loaded MIL-101, were investigated down to the atomic scale by annular dark-field scanning transmission electron microscopy using low dose conditions and fast image acquisition. The results directly show that the used wet chemistry loading approach is well-fitted for the accurate embedding of the individual catalyst nanoparticles into the cages of the MIL-101. The MIL-101 host material remains crystalline after the loading procedure, and the encapsulated Ru nanoparticles have a metallic nature. Annular dark field scanning transmission electron microscopy, combined with EDX mapping, is a perfect tool to directly characterize both the embedded nanoparticles and the loaded nanoscale MOFs. The resulting nanostructure of the material is promising because the Ru nanoparticles hosted in the MIL-101 pores are prevented from agglomeration-the stability and lifetime of the catalyst could be improved.