Solids, Volume 7, Issue 4 (August 2026) – 6 articles

Enclosed reinforced concrete structures subjected to internal blast loading represent a critical safety concern in infrastructure applications where detonations may occur within confined spaces. Although circular cross-sections have been widely adopted for blast-resistant containment structures, systematic quantitative comparisons of internal blast responses between circular and square enclosed configurations under progressive charge weight conditions remain limited. LS-DYNA finite element simulations are conducted under four trinitrotoluene (TNT) charge weight conditions ranging from 1200 to 2500 kg, and the failure-inducing blast load is defined as the minimum charge weight at which continuous concrete element deletion first occurs in the roof or side-wall region. In this study, the failure-inducing blast load is interpreted as an erosion-based comparative indicator under the adopted empirical blast-loading framework rather than as an absolute real-world confined-blast failure threshold. The roof failure-inducing blast load is identical for both structures at 1200 kg, whereas the side-wall failure-inducing blast loads are 2500 kg for the circular structure and 1500 kg for the square structure, indicating approximately 67% higher side-wall blast resistance in the circular structure. This difference is attributed to the membrane action of the curved wall, which redistributes internal blast-induced lateral pressure along the circumferential direction and limits out-of-plane deformation. Under the 2500-kg condition, the peak side-wall displacement of the square structure is 161.6% higher than that of the circular structure, whereas its peak roof displacement is 33.3% lower. Axial strains at all reinforcement locations remain within the elastic range, confirming that concrete damage is governed by the low tensile capacity of concrete rather than reinforcement yielding. Full article

The new requirements for materials with improved properties and resistance to hazardous aggressive environments is very important in industrial incinerators and stoves. Thus, the present manuscript is dedicated to the study of the chemical interaction between Fe-Cr alloys at high temperatures (500–600 °C). Four alloys with different Al, Si, and Mo chemical composition were tested to determine their resistance to active laboratory conditions. The conditions were established based in those inside waste disposal incinerators. Laboratory equipment was set up to reproduce an enclosed aggressive but controlled atmosphere. Cylinders filled with N₂ and O₂ generated an 8% vol, and other containers produced a 220 vppm of HCl, 360 Vppm of H₂O, and 200 vppm of SO₂. The exposition was not continuous because the goal was to analyze the material response along different exposition times. The corrosion products that resulted after chemical etching were characterized using Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), and taking an average of various thermo-gravimetric measurements. The main products were Cr₂O₃, Fe₂O₃, Fe_0.6Cr_0.4, and Fe and Cr. The alloy with the best performance was found and theoretical principles of corrosion were analyzed to understand the corrosion mechanisms, which were driven by the formation of non-protective oxides. Full article

Corrosion of carbon steel components represents a major economic and safety challenge in industrial applications, motivating the development of protective thin film coatings with optimized deposition parameters. This study investigates the deposition of nickel nitride (Ni-N) thin films on AISI 1016 carbon steel and silicon (111) wafers by reactive radio-frequency (r.f.) magnetron sputtering at three power levels: 150, 175, and 200 W. Surface color, film thickness, roughness, crystal structure, mechanical properties, and electrochemical behavior were evaluated using optical microscopy, stylus profilometry, atomic force microscopy (AFM), X-ray diffraction (XRD), nanoindentation, and potentiodynamic polarization combined with electrochemical impedance spectroscopy (EIS). Increasing r.f.-power produced systematic surface color changes consistent with variations in film thickness, which ranged from approximately 25.0 to 50.7 nm. Higher deposition power promoted smoother surfaces, with average roughness (Ra) decreasing from 64.28 nm at 150 W to 20.62 nm at 200 W. XRD analysis revealed a monocrystalline Ni₃N hexagonal close-packed (HCP) phase at 150 W, transitioning to a dual-phase Ni₃N (HCP) and Ni₄N face-centered cubic (FCC) microstructure at 175 and 200 W. The highest hardness (11.80 ± 3.34 GPa) was recorded at 150 W, accompanied by pop-in events attributed to dislocation nucleation in the HCP lattice. Electrochemical evaluation in 3.5 wt.% NaCl solution demonstrated that films deposited at 150 and 175 W exhibited corrosion current densities and rates exceeding those of bare steel, confirming that these conditions accelerate rather than inhibit corrosion. Only the film deposited at 200 W achieved superior corrosion protection, with a corrosion current density and rate approximately 50% lower than bare steel, attributed to its denser microstructure and smoother surface morphology. These findings demonstrate that r.f. power is a critical parameter governing the properties of Ni-N thin films, and that careful optimization of deposition conditions is essential before recommending such coatings for industrial corrosion-protective applications. Full article

The study investigated the addition of nanocellulose (NC) as a reinforcing agent in wood-phenol resorcinol formaldehyde (PRF) composites for thermoset extrusion-based manufacturing. Three types of NC (cellulose nanocrystals (CNC), bleached nanofibers (BNFs), and unbleached nanofibers (UBNFs)) at 1–3% loadings and new (NP) and 4-year old (OP) PRF resin were evaluated by a combination of thermal analysis, rheology and flexural testing. The NP was shown to gel at a lower temperature than OP. CNC addition advanced gelation and yield stress; whereas, UBNFs reduced viscosity and yield stress through plasticization but were suitable for extrusion. The NC-reinforced wood–PRF formulations were successfully extruded into continuous composite rods. A flexural modulus of 8.1 GPa and strength of 77 MPa was achieved. Moreover, NC was shown to reduce 24 h water absorption compared to controls. These findings show that NC reinforcement improves wood–PRF composites systems for potential sustainable additive manufacturing. Full article

In this work, the structural, optical, vibrational, and stability properties of a series of Al_xAs_x nanostructures are systematically investigated using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). Starting from the fundamental cubic-like Al₄As₄ building block, progressively larger nanostructures were constructed through directional elongation and structural rearrangements, allowing for the exploration of one-dimensional chains, two-dimensional planar structures, and several exotic geometries. The calculated UV–visible absorption spectra reveal that structural dimensionality and topology strongly influence the electronic transitions of the nanostructures, with elongated and distorted configurations exhibiting broader absorption features and richer spectral distribution. Vibrational analysis shows that increasing structural complexity and reducing symmetry lead to a higher density of IR-active modes and more complex infrared spectra. The stability of the nanostructures is evaluated through binding energy calculations, which indicate a clear size-dependent stabilization trend, with the Al₂₄As₂₄-L1 configuration exhibiting the highest stability among the examined systems. In addition, the calculated HOMO-LUMO gaps reveal the semiconducting character of the clusters and demonstrate their sensitivity to geometric topology. The present results establish clear structure–property relationships between dimensional growth and the optical response of AlAs nanoparticles and provide theoretical reference data for future experimental investigations of III-V semiconductor nanostructures. Full article

The structural, electronic, and magnetic properties of the PdRSb, usually also referred to as RPdSb, ($R=$ La-Lu) semi-Heusler compound series have been systematically investigated using first-principles calculations based on Density Functional Theory (DFT). Our structural optimizations reveal that the cubic $C{1}_{\mathrm{b}}$ A-type variant is the energetically most favorable and thermodynamically stable ground state across the entire series. The calculated equilibrium lattice constants follow the well-known lanthanide contraction trend, with the exception of the Yb-based compound, which displays an anomalous lattice expansion. Magnetic stability analysis demonstrates that the magnetism is highly localized at the rare-earth (R) sites and closely follows the progressive filling of the $4f$ shell, peaking at $7{\mathsf{\mu }}_{\mathrm{B}}$ for PdGdSb, while PdLaSb, PdYbSb, and PdLuSb remain non-magnetic. Furthermore, our electronic structure calculations reveal a rich variety of behaviors: PdLaSb and PdLuSb behave as gapless semiconductors, while most of the magnetic compounds exhibit near half-metallic characteristics. Notably, PdCeSb is predicted to be a perfect half-metal with an integer magnetic moment of $1{\mathsf{\mu }}_{\mathrm{B}}$. These findings highlight the significant chemical tunability of the PdRSb family, positioning them as promising candidates for future applications in spintronics and magnetoelectronics. Full article