arXiv subjects

Stefano Deledda

Publications and source records attributed to Stefano Deledda.

5 recordsLinked to original sources

arXiv2026

Building a physics-aware AI ecosystem for solid-state hydrogen storage materials

Hydrogen storage remains a central bottleneck for scalable hydrogen energy systems due to the multiscale and coupled nature of the thermodynamics, kinetics, and microstructural evolution of hydrogen storage materials (HSMs). Although artificial intelligence (AI) has accelerated materials discovery, current approaches remain constrained by fragmented data, limited physical consistency, and weak integration with experimental validation. Here, we propose a unified framework that integrates coherent data infrastructure, physics-grounded modeling, and AI-driven inverse design within a closed-loop discovery paradigm. By embedding physical constraints and experimental feedback, this approach enables adaptive, physically consistent optimization, thereby establishing a pathway toward autonomous, digital-twin-enabled discovery of HSMs.

cond-mat.mtrl-sci↗

arXiv2026

Effect of Niobium Doping on the Crystal Structure and Hydrogen Sorption Properties of TiFe: Combined Synchrotron X-ray Diffraction and Extended X-ray Absorption Fine Structure Study

TiFe alloys are attractive compounds for solid-state stationary hydrogen storage. They can absorb hydrogen gas reversibly at near ambient temperatures and practical pressures with high volumetric capacities surpassing that of cryogenically liquified H2. The main drawback of TiFe-based storage systems is a costly activation procedure required due to the formation of oxide surface layer, which hinders hydrogen diffusion into the bulk. Doping the alloy with various additives is known to improve hydrogen diffusion softening the conditions of the activation procedure. Hydrogen sorption properties of the modified alloys have been the focus of most studies whereas less attention has been dedicated to the fundamental understanding of the effects of hydrogen sorption on the alloys' structure. The latter, however, is an important information in the knowledge-guided design of novel materials. In this work, we investigated effects of Nb-doping on crystallographic structure of TiFe metal-alloy compounds and their hydrogen sorption properties. TiFe samples with two different Nb stoichiometries were synthesized using arc-melting (AM) and characterised with synchrotron powder X-ray diffraction (SR-PXRD) and extended X-ray absorption fine structure (EXAFS) analysis. Overall, H2 absorption measurements (at 50 +/- 2 degrees C and 40 +/- 2 bar), have shown that doping of TiFe with Nb can improve matrix activation and kinetics of hydrogen sorption without compromising the overall storage capacities. Refinement of SR-PXRD and EXAFS data showed significant Nb occupancy in secondary Ti phases, which improved the hydrogenation properties of the alloys.

cond-mat.mtrl-sci↗

arXiv2025

Scalable Production of Photochromic Yttrium Oxyhydride Powder via Ball Milling

Yttrium oxyhydride (YHO) represents one of the most promising photochromic materials discovered in recent years, yet its practical deployment has been severely constrained by the limitations of thin film deposition methods. Here we demonstrate the first successful synthesis of photochromic YHO powders through reactive ball milling under hydrogen atmosphere followed by controlled oxidation a fundamentally scalable approach that overcomes the production barriers facing this technology. High-energy planetary ball milling of yttrium metal under 50 bar hydrogen for 20 hours, followed by controlled oxidation in ultra-dry technical air, yielded nanostructured YHO powders with less than 500 nm particle sizes. These powders exhibit robust photochromic response with reflectance modulation at 850 nm under 405 nm excitation, reversible cycling behavior, and the characteristic memory effect previously observed only in thin films. Powder X-ray diffraction confirms the formation of the cubic YHO phase with lattice expansion consistent with oxygen incorporation into the yttrium hydride structure. Critically, we demonstrate that YHO powders can be processed into polymer composites enabling spatially-resolved photochromic patterning a capability essential for practical device applications. While optimization of optical contrast remains an opportunity for future work, this powder synthesis route fundamentally transforms the manufacturing of YHO-based photochromic systems, enabling mass-scale production using established industrial ball milling infrastructure. These findings establish a viable pathway toward commercial deployment of YHO in smart windows, adaptive optics, and rewritable information storage applications.

cond-mat.mtrl-sci↗

arXiv2022

In-situ neutron diffraction during reversible deuterium loading in Ti-rich and Mn-substituted Ti(Fe,Mn)0.90 alloys

Hydrogen is an efficient energy carrier that can be produced from renewable sources, enabling the transition towards CO2-free energy. Hydrogen can be stored for a long period in the solid-state, with suitable alloys. Ti-rich TiFe0.90 compound exhibits a mild activation process for the first hydrogenation, and Ti(Fe,Mn)0.90 substituted alloys can lead to the fine tuning of equilibrium pressure as a function of the final application. In this study, the crystal structure of TiFe(0.90-x)Mnx alloys (x = 0, 0.05 and 0.10) and their deuterides has been determined by in-situ neutron diffraction, while recording Pressure-Composition Isotherms at room temperature. The investigation aims at analysing the influence of Mn for Fe substitution in Ti-rich Ti(Fe,Mn)0.90 alloys on structural properties during reversible deuterium loading, which is still unsolved and seldom explored. After activation, samples have been transferred into custom-made stainless-steel and aluminium alloy cells used for in-situ neutron diffraction experiments during deuterium loading at ILL and ISIS neutron facilities, respectively. The study enables remarkable understanding on hydrogen storage, basic structural knowledge, and support to the industrial application of TiFe-type alloys for integrated hydrogen tank in energy storage systems by determining the volume expansion during deuteration. Furthermore, the study demonstrates that different contents of Mn do not significantly change the volumetric expansion during phase transitions, affecting only the deuterium content for the {\gamma} phase and the cell evolution for the \b{eta} phase. The study confirms that the deuterated structures of the {\gamma} phase upon absorption, \b{eta} and {\alpha} phase upon desorption, correspond to S.G. Cmmm, P2221 and Pm-3m, respectively.

cond-mat.mtrl-sci↗

arXiv2022

TiFe$_{0.85}$Mn$_{0.05}$ alloy produced at industrial level for a hydrogen storage plant

In the use of hydrogen as large-scale energy vector, metal hydrides based on intermetallic compounds play a key role, thanks to mild temperatures and pressures required for the storage. It is increasingly necessary to develop hydrogen-based devices, and in this work, the intermetallic compound TiFe$_{0.85}$Mn$_{0.05}$ is evaluated and selected as H$_2$-carrier for a storage system of 50 kg of H$_2$. A batch of 5 kg of alloy was synthesized at industrial level and characterized through scanning electron microscopy and powder X-ray diffraction, to determine the structure and phase abundance. Moreover, the hydrogen sorption properties were investigated through thermodynamic and kinetic analyses, followed by a long-term cycling study and resistance to O$_2$ and H$_2$O poisoning. Comparing results for alloys with same nominal composition, but prepared either under industrial or laboratory conditions, it was found that the alloy synthesis promotes discrepancies in phase abundance and microstructure and promotes the formation of a passive layer that deeply affect the hydrogen sorption properties. A scheme based on Monte Carlo simulation and structural results was developed to explain the key role of the passive layer (Ti$_3$Fe$_3$O) and of the secondary phases (Ti$_4$Fe$_2$O$_{0.4}$ and $\beta$-Ti$_{80}$(Fe,Mn)$_2$0) in promoting the hydrogenation of the TiFe$_{0.85}$Mn$_{0.05}$. A storage system based on this alloy can be integrated with an electrolyser upstream (25 bar) and a fuel cell downstream (1 bar) at 55 $^\circ$C, storing 1.0 H$_2$ wt.%, displaying fast kinetic, resistance to oxygen, water and nitrogen gas impurities, and stability over more than 250 cycles.

cond-mat.mtrl-sci↗