CO2 valorization from real feedstocks through CH4 tri-reforming (CH4-TR), combining steam reforming (SR), dry reforming (DR), and partial oxidation (CPO) of methane in a single process, is a desirable strategy for greenhouse gas mitigation and syngas (CO + H-2) production. NiCo/gamma-Al2O3 catalysts prepared by impregnation at different relative metal contents (Ni50Co50 and Ni30Co70) were investigated for CH4-TR in a fixed-bed reactor under conventional heating and characterized by XRD, FESEM, and Raman spectroscopy after catalytic runs. This study focused on the role of the Ni/Co ratio and feed composition on selectivity for CO2 valorization, syngas yield, and deactivation resistance. Both the catalysts showed high activity, with a superior performance of Ni50Co50 confirming Ni metal species as the active sites. While in DR, a slow deactivation occurred due to coke deposition, in CH4-TR, the addition of small O-2 and/or H2O amounts stabilized activity and selectivity due to surface carbon removal. Large O-2 and H2O amounts strongly inhibited CO2 conversion due to competition with CPO and SR, in the order CPO >= DR > SR. Interestingly, the stoichiometric CH4-to-oxidants ratio favored the DR pathway, giving very high CO2 conversion. Modulating CH4 addition into real flue mixtures renders CH4-TR on NiCo/gamma-Al2O3 catalysts a favorable strategy for effective valorization of CO2 industrial or biomass-derived streams.

We investigate the impact of proton, Xe ion, and gamma-ray irradiation on the critical current density components in the singe-crystal iron-based superconductor CaKFe4As4 In particular, we investigate via magnetic measurements the in-plane critical current densities for fields applied along the c axis (J(c)) and parallel to the ab plane J(c)(ab). This 1144-type compound, known for its high J(c) and anisotropic pinning behavior, exhibits a complex vortex pinning landscape. By comparing pre- and post-irradiation behavior under magnetic fields applied parallel and perpendicular to the irradiation direction, we assess the effectiveness of different defect types as pinning centers. Our results provide insights into how irradiation type influences J(c) anisotropy and its field dependence, with implications for conductor development.

Magnetic nanoparticles capable of generating heat under alternating high-frequency electromagnetic fields were employed to drive methane bi-reforming with steam and carbon dioxide. Ni–Co alloy nanoparticles with compositions Ni50Co50 and Ni30Co70, supported on γ-Al₂O₃ pellets, were synthesized and comprehensively characterized. Their catalytic performance under magnetic induction heating was investigated as a function of alloy composition, applied magnetic field, and CO2/H2O feed ratio at a fixed CH4/(CO2+H2O) ratio. All catalysts exhibited significant activity in methane bi-reforming, achieving high methane conversions and tunable syngas compositions. Co-rich alloys reached higher steady-state temperatures due to their higher Curie temperatures, enhancing CO2 conversion, whereas Ni-rich catalysts showed higher activity at lower applied fields. Increasing CO2 content in the feed promoted dry reforming, decreasing the H2/CO ratio while improving CO2 utilization, at the expense of increased carbon deposition. Post-reaction characterization confirmed the structural stability of the Ni-Co alloys under induction-heated operation. These results demonstrate that magnetic induction heating enables fast, localized, and controllable heating for methane bi-reforming. Proper optimization of the Ni/Co ratio and operating conditions is essential to balance catalytic activity, heating efficiency, and resistance to carbon formation, highlighting the potential of this approach for electrified and energy-efficient syngas production.

The development of sustainable sorbents for energy-efficient CO2 capture is a pressing challenge. Here we report a simple, solvent-minimized liquid-assisted grinding (LAG) route for the preparation of CALF-20 and its magnetic composite CALF-20@Fe3O4. The MOF synthesized in only 2 h exhibits high crystallinity, a BET surface area of similar to 600 m(2) g(-1), and a CO2 uptake of 5,0 mmol g(-1) at 273 K and 1 bar, comparable to solvothermal benchmarks. Incorporation of 8 wt% Fe3O4 nanoparticles yields a composite with preserved porosity, strong CO2/N-2 selectivity (S approximate to 323 at 273 K), and near-bulk magnetic properties. When shaped into poloxamer-bound granules, the composite retains its structural integrity while exhibiting an increased working capacity (1,4 mmol g(-1)) due to enhanced regenerability at 403 K. Under alternating magnetic fields, the granules achieve rapid, volumetric heating with specific absorption rates up to 80 W g(-1), enabling fast sorbent regeneration. These results demonstrate that CALF-20@Fe3O4 combines the chemical robustness of CALF-20 with magnetic induction heating functionality, offering a scalable platform for low-energy post-combustion CO2 capture.

This study examines the potential of CALF-20, a zinc-based metal-organic framework (MOF), synthesized through mechanochemistry, for carbon dioxide (CO2) capture using temperature swing adsorption (TSA) in postcombustion processes. Unlike conventional methods, mechanochemical synthesis reduces solvent usage and reaction time, aligning with sustainability goals while preserving the structural integrity of CALF-20. This research investigates CALF-20 thermodynamic and kinetic properties, assessing its CO2 adsorption and desorption performance within a laboratory-scale fixed-bed reactor under various operational temperatures (28-130 degrees C) and CO2 concentrations (3-20 % by volume). Key findings reveal that CALF-20 displays promising CO2 adsorption and desorption efficiency, achieving complete regeneration in each cycle. Sips isotherm analysis demonstrates a high CO2 adsorption capacity (up to 2.55 mmol g-1) and surface heterogeneity, while isosteric heat of adsorption values confirm a physisorption-driven process. Kinetic analysis shows that the pseudo-firstorder model fits the CO2 adsorption data best, further confirming a primarily physical adsorption mechanism. Additionally, the study demonstrates the stable performance of CALF-20 across ten TSA cycles, underscoring its potential as a viable and sustainable material for CO2 capture applications.

The synthesis of CaKFe4As4 superconducting compounds either requires the adoption of high-temperature synthesis or implies the intimate mixing of the precursors via mechanochemical routes before the thermal step in order to avoid chemical inhomogeneities that lead to thermodynamically stable unwanted phases. High Energy Ball Milling (HEBM) represents a useful tool to ensure the comminution of the elements and their dispersion to obtain the target phase. The adoption of mechanochemical treatments is, however, known to lead to the formation of aggregates of small crystals, leading to a powder morphology not optimal for practical applications. In this work, we report our findings in the synthesis of CaKFe4As4 polycrystalline compounds showing the effect of milling energy on the morphology and phase composition of the powders. To overcome the limits of conventional synthesis, we report the results of a novel synthesis approach for CaKFe4As4 materials, highlighting how the choice of the proper precursors and the adoption of milder treatments can represent the key to optimizing the powder morphology.

Ca/K-1144 compounds constitute promising materials to be exploited for the fabrication of Iron Based Superconductors (IBSC) wires via the Powder in Tube (PIT) method thanks to the high critical currents observed in single crystals coupled to the simple and robust chemical composition. The production of Ca/K-1144 wires has been however hindered by the reactivity of Ca with Ag, the common choice for sheath materials in IBSC wires. In our recent work, we demonstrated the potentiality of composite Cu/Ta sheaths to be adopted for these kinds of applications. In this work, we show the effect of the variation of sintering temperature and mechanical processing on the morpho-structural and superconducting properties of wires processed through this combination of materials. While critical currents are still to be improved, compared to state of the art 122-Ag wires, with evident margins for what concerns both the synthesis step and the wire production process, the results show how sintering temperature can be raised up to 900°C. The intrinsic fragility of pure Ta observed during the wire processing is proposed to be mitigated by tailoring the sheath dimensions or the Ta barrier chemical composition.

A magnetic composite consisting of MOF HKUST-1 and magnetite nanoparticles was synthesized and successfully utilized for the separation of CO2 from N2/CO2 mixtures. The CO2 adsorbed by the porous material was successively desorbed by means of a recently proposed, high-efficiency technique so-called Magnetic Induction Swing Adsorption (MISA). The energy necessary to the desorption of carbon dioxide is transferred by electromagnetic induction to the magnetic nanoparticles that locally dissipate it into heat. The composite material has been synthesized by growing the metal organic framework on functionalized magnetite nanoparticles by means of liquid assisted grinding (LAG) mechanochemical process. The composite material has been characterized in its morphological and functional properties. Thanks to improved magnetic properties, the optimized nanocomposite requires lower magnetic fields to desorb the CO2 and allows for reaching the same regeneration temperature in the sorbent bed at lower magnetic field amplitude, compared to previously synthesized composite materials. A regeneration energy Q of 4.4 MJ/kg CO2 has been calculated at 130°C desorption temperature.

We have investigated the local structure of the iron-based CaKFe4As4 superconductor featuring distinct aliovalent substitutions at the Ca and K sites, that is CaKFe4As4, CaK0.9Sr0.1Fe4As4, CaK0.9Ba0.1Fe4As4 and Ca0.9Na0.1K0.9Ba0.1Fe4As4. Temperature-dependent Fe K-edge extended x-ray absorption fine structure (EXAFS) measurements are used to determine the near-neighbors bondlengths and their stiffness. The EXAFS analysis reveals that the Fe-As bondlength undergoes negligible changes by substitution, however, the Fe-Fe bondlength and the As height are affected by the Sr substitution. The superconducting transition temperatures of CaK0.9Sr0.1Fe4As4 and CaK0.9Ba0.1Fe4As4 are very similar even if the mean As heights are significantly different suggesting that the anion height may not be a unique parameter to describe the superconductivity in CaKFe4As4. The mean As heights show a peculiar temperature dependence characteristic of CaKFe4As4 system. Furthermore, the temperature-dependent mean square relative displacements reveal similar Fe-Fe bond stiffness in all samples, instead the Fe-As bond is substantially stiffer in case of CaK0.9Sr0.1Fe4As4. The local structure results are discussed in relation to the differing transport properties of aliovalent substituted 1144 superconductor.

1144 is a family of Iron Based Superconducting Compounds that attracts interest due to its regular structure, composed by an alternance of alkaline and alkaline-earth planes that intercalate Fe-As layers. This rigidity grants to 1144 compounds a stoichiometric nature, and thus a robust critical temperature not affected by chemical inhomogeneities, and a peculiar pinning landscape enhancing critical currents at high fields. Critical currents can be however further enhanced by introducing further defects by means of irradiation and chemical doping on the Fe site. In our works, as a different approach, we evaluate the effect of the alkaline and alkaline-earth aliovalent substitutions. For this scope, CaKFe4As4 polycrystalline powders have been successfully doped by partially replacing Ca with Na and K with Ba by means of a mechanochemically assisted thermal synthesis. Such substituted compounds crystallize in the P4/mmm structure typical of 1144 compounds. X-ray diffraction analysis revealed that depending on the level of substitution the reflections characteristic of the P4/mmm tend to vanish. In particular, peaks analysis has shown that doping introduces increasing disorder in selected crystalline planes. Barium and sodium, as dopant, do not act the same way, the latter being less invasive, so that 1144 structure is preserved up to 40% substitution. The contemporary replacement of potassium and calcium with barium and sodium exhibits an intermediate behavior. Analysis of X-ray diffraction profiles collected as a function of temperature down to 100 K allowed to calculate the thermal expansion coefficients for the synthesized compounds, with CTE values similar for pristine and substituted compounds close to 1 x 10(-6)K(-1) and 3 x 10(-5)K(-1) respectively along the a-axis and c-axis.

Among Iron Based superconductors (IBSC), the compounds belonging to the 1144 family are characterized by the A1AE1Fe4As4 chemical composition (A=Alkaline, AE=Alkaline-Earth) and considered stoichiometric.In recent experiments, we obtained 1144 samples characterized by different levels of alkali and alkaline earth metals substitutions and demonstrated how the lattice distortion induced by such variation in the chemical composition plays a fundamental role on critical temperature values.In this work, we investigate the possibility to obtain Ca/K-1144 compounds substituted with Rare-Earth (RE) elements.We produced polycrystalline samples in which RE ions partially replace Ca ions in the 1144 phase.The lattice structure is consistently affected by the substituent element inducing a contraction of the c-axis.Multiple substitution of RE and A or AE elements was also attempted, showing that appropriate combinations allow simultaneous inclusion of different elements in the structure.For compounds that include RE elements, the critical temperature of the samples appears to follow to the same trend with respect to the distortion of the crystal lattice induced by A and AE substitutions.

The 1144 Iron-Based Superconductors (IBSC), characterized by the A 1 AE 1 Fe 4 As 4 chemical composition (A=Alkaline, AE=Alkaline-Earth), has gained significant interest in the recent years due to their crystalline structure character-ized by an intrinsic modulation of the strain along the c-axis and by the proneness in forming crystalline defects with a positive impact on flux pinning. Moreover, it has been proved that the compound is compatible with the cost-effective powder-in-tube (PIT) manufacturing process. In our recent experiments, we have showed that the A 1 AE 1 Fe 4 As 4 structure can be tailored to obtain a 1144 com-pound characterized by different (A x AE 1-x )(AE y A 1-y )Fe 4 As 4 chemical formulae without any depression in the critical temper-ature value. On the other hand, it has been recently shown that the doping with selected elements on both A and AE sites has a clear influence on the pinning and the grain boundary properties of poly-crystalline samples. In this work we report the results of the extensive magnetic characterization performed on pristine Ca 1 K 1 Fe 4 As 4 and doped (A x Ca 1-x )(AE y K 1-y )Fe4As4 with Ba as dopant on the K site and ei-ther La or Na as dopant on the Ca site. In particular, the magnet-ization hysteresis loops recorded at different temperatures M(H, T) and the critical current density dependences extracted from the M(H) using the Bean model, J c (B, T), have been analyzed in order to assess the effect of aliovalent doping on the quality of the produced samples in terms of grain boundary properties and pinning efficiency.

Iron-based superconductors (IBSCs) are a class of material under investigation for the development of superconducting wires in the low-temperature-high magnetic fields power application. Among the various families of IBSCs, the 1144 CaKFe4As4 compound is a promising material able to achieve outstanding superconducting properties with a cheap and simple chemical composition. Oxidation, in these compounds, is considered an obstacle for high intergranular critical current density, Jc,GB. A study devoted to the evaluation of oxidation phenomena and their effects on the superconducting properties is thus needed in order to fully understand the involved mechanisms. From the evaluation of polycrystalline samples obtained by a mechanochemically assisted synthesis route, a degradation of the critical temperature and critical currents has been observed concurrently with oxygen accumulation at grain boundaries in open porosities. However, the crystalline structure at an atomic level seems not affected, as well as intragranular superconducting properties assessed by means of calorimetric methods. These results suggest that loss of superconducting properties in Ca/K-1144 compounds following oxidation is significantly associated with the worsening of grain connectivity.

To draw a complete vortex phase diagram for a CaKFe4As4 polycrystalline iron-based superconductor, different kinds of magnetic measurements have been performed focusing on the critical parameters of the sample. Firstly, magnetic moment versus field measurements m(H) were performed at low fields in order to evaluate the lower critical field Hc1. After that, by performing relaxation measurements m(t), a field crossover Hcross was detected in the framework of a strong pinning regime. The irreversibility field Hirr as a function of the temperature curve was then drawn by plotting the critical current densities Jc versus the field for temperatures near Tc. Jc(H) has demonstrated a second magnetization peak effect phenomenon, and the second peak field Hsp has been identified and plotted as a function of temperature, providing information about an elastic to plastic transition in the vortex lattice. Finally, the upper critical field Hc2 as a function of the temperature has been obtained. Hc1, Hcross, Hsp, Hirr, Hc2 have been fitted and used for drawing the complete vortex phase diagram of the sample. It can be helpful for the understanding of the applicative ranges in the field and temperature of the materials with not-optimized fabrication characteristics, as usually is found in superconducting wires and cables for power applications.

NiCo supported magnetic nanoparticles can catalyze the steam reforming of methane and at the same time provide the heat necessary to run the process by dissipating an external radio frequency electromagnetic field. Magnetic samples with different Ni:Co molar ratio and total metal loading on the support have been synthesized using a traditional impregnation procedure and characterized in terms of morphological and structural prop-erties. The ability of the materials to provide process heat was assessed by temperature measurements. Methane conversion value and syngas composition have been measured for different applied field amplitude. The sample with a composition Ni50Co50_30 wt% was found to be the most performing in terms of conversion obtained with the same applied magnetic field. The developed magnetic catalysts contribute to the transition to distributed hydrogen production and help to tackle some of the challenges related to the intensification of production processes by electrification.

Among IBSC superconductors, the 1144 family ( AAE Fe4As4 with A = alkali metal, AE = alkaline-earth metal), has attracted considerable interest in recent years because of their propensity to form lattice defects that positively influence the flux pinning properties. Extensive research is underway to optimize this class of materials for the low-temperature high-field regime, both in the form of single crystal and polycrystalline powder. The latter is of particular interest because the 1144 material has been shown to be suitable for wire production through the easy and well-assessed Powder In Tube (PIT) process. In our recent experiments, it has been shown that the 1144 structure can be tailored to obtain a doped compound with a different chemical formula ( A x AE 1-x )( AE y A 1-y )Fe 4 As 4 , that is characterized by unaltered critical temperature values despite the high level of substitution up to 15 at.%. In order to unveil the influence of the double substitution on the grain boundary and pinning properties of doped samples, we recently started an extensive characterization campaign whose preliminary results are presented here. Both structural and morphological properties of the compound are not affected by the simultaneous doping with 10 at.% Na and 5 at.% Ba, as revealed by XRD and SEM analyses. On the contrary, the study of magnetic properties shows that although there is no improvement in transport properties, the aliovalent substitution induces a clear change in the in-field behavior which deserves further investigations.

Ca/K-1144 compounds have been described widely in literature as stoichiometric compounds, with a Ca:K ratio equal to unity. In this work, we demonstrate that Sr ions can substitute K ions in the 1144 lattice. Polycrystalline samples were produced via a mechanochemically assisted synthesis route. Sr substitution in the Ca/K compound leads to a shortening of its c axis, while no differences are appreciable from the morphological point of view. The CaK0.9Sr0.1Fe4As4compound is characterized by a slightly reduced critical temperature of approximately 31 K, with respect to the 35 K of the pristine compound. The role of lattice distortion, carrier concentration or structural disorder that may be accounted for the reduction of critical temperature is here discussed.

Among the iron-based superconductors, the so-called 1144 family has, in recent years, attracted significant interest due to its stoichiometric nature, with materials robust towards chemical inhomogeneities and characterized by a well-defined critical temperature. The most studied 1144 compounds are characterized by the A 1 AE 1 Fe 4 As 4 chemical composition, where A and AE constitute an appropriate combination of alkaline and alkaline-earth metals, respectively. The 1144 structure is in fact formed only when the A and AE elements respect specific requirements in terms of relative size and parent compound structure. The stoichiometric aspect, one of their strong points, has represented, however, up to today a restriction, limiting the conceptualization of 1144 structures to quaternary compounds. In this work, we demonstrate that to obtain the 1144 crystalline phase it may be sufficient to maintain a 1:1 ratio between ions of different size that intercalate the Fe-As planes, and that in selected conditions an opportunely tailored cation substitution is possible. Using a simple mechanochemically assisted synthesis route 1144 compounds where Ca is substituted by Na, K by Ba, and both simultaneously, are obtained. We demonstrate that the critical temperature of doped compounds is not simply related to the substitution amount or to the resulting Fe valence. We show that the superconducting transition is in fact linked to the structural distortion induced by the chemical composition variation: by tailoring the chemical composition we obtain doubly substituted samples—with substitution levels up to 20%—characterized by a tetragonality ratio c / a similar to the pristine compound and critical temperatures of approximately 34 K.

Iron based superconducting wires (IBSCs) produced by the Powder in Tube (PIT) method rely on the use of silver sheaths as chemical buffer between the outer metal and the superconducting core. The adoption of silver entails however some limitations, such as the viable temperature range when coupled with copper, and the incompat-ibility with calcium-based IBSCs already at 600 degrees C, driving the research towards other wires architecture. Taking inspiration from the low temperature superconductors field, we decided to evaluate the adoption of tantalum as diffusion barrier in a layered Cu/Ta architecture, choosing a Ca/K-1144 IBSC as case study considering the high reactivity issues already reported in the case of silver sheaths for this compound. Squared wires were produced through a groove rolling lamination process coupled with a thermal treatment at 800 degrees C. The microstructural analyses show the absence of interdiffusion between the different parts of the wire, and the magnetic character-ization shows performance in line with similar polycrystalline manufacts, with margin of enhancement to be pursued via the optimization of the mechanical process and other experimental variables. The reported results suggest thus the effectiveness of tantalum as diffusion barrier for Ca/K-1144 PIT wires.