Solids

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

The present study addresses the fabrication of porous gyroid architectures by additive manufacturing from preceramic polymer feedstocks. Photocurable emulsions were engineered by combining a silicone powder with acrylate monomers and dispersing an emulsified secondary phase of calcium nitrate. The formulations showed light-curing behaviour compatible with digital light processing vat photopolymerization (DLP-VPP), enabling high-fidelity replication of triply periodic minimal surface (TPMS) gyroids (designed porosity: 85 vol.%). After pyrolysis in nitrogen at 700 °C, the lattices converted into CaO–SiO₂-derived amorphous matrices embedding an in situ turbostratic/pyrolytic carbon fraction, as suggested by the photothermal response and preliminary impedance behaviour, although the latter was measured in liquid electrolyte and therefore does not isolate electronic transport. To improve robustness during polymer-to-ceramic conversion, pharmaceutical borosilicate waste glass (BASG) was added as a passive filler (30–70 wt.%). The waste-glass phase acts as a passive filler that improves processing robustness and can mitigate shrinkage-induced damage during pyrolysis, while remaining electrically insulating (dielectric) and therefore not directly contributing to electronic conduction. The resulting structures combine high surface-to-volume ratio, controlled open porosity, and structural integrity with electrochemical responsiveness under the adopted test conditions, making them promising architected platforms for electrochemical components where interconnected porosity is advantageous. Full article

Two-dimensional molybdenum disulfide (MoS₂) has emerged as a promising candidate for next-generation electronics and optoelectronics; however, its scalable synthesis with precise control over domain size and film continuity remains challenging. Herein, we report a physical vapor deposition (PVD)-assisted chemical vapor deposition (CVD) strategy for the controllable growth of high-quality monolayer MoS₂. By thermally evaporating an ultrathin (3 nm) MoO₃ precursor film, spontaneous post-deposition dewetting yields a porous honeycomb morphology that significantly enhances vapor–solid reaction kinetics during subsequent sulfurization. Crucially, by modulating the argon carrier gas flow rate to regulate the local sulfur chemical potential, we achieve distinct growth regimes: a high flow rate (70 sccm) suppresses nucleation density, enabling isolated triangular and hexagonal single crystals with lateral dimensions up to 500 μm, whereas a reduced flow rate (50 sccm) promotes high-density nucleation and coalescence into continuous centimeter-scale polycrystalline films. Comprehensive structural and optical characterizations, including atomic force microscopy, Raman spectroscopy, photoluminescence, and X-ray photoelectron spectroscopy, confirm that the synthesized MoS₂ exhibits prototypical monolayer thickness (~0.7 nm), well-defined local crystallinity and a direct bandgap emission at 1.84 eV. This work establishes a robust, scalable, and highly tunable route for synthesizing large-area 2D TMDs tailored for advanced device integration. Full article

Using the molecular dynamics method, the compression of nickel nanoparticles with a nanocrystalline structure was simulated. The influence of the nanoparticle size (from 2 to 20 nm) and the average grain size within it (from 2 to 8 nm) on the compressive strength and on the strain at which the maximum stress is reached was investigated. In addition, the stability of the nanocrystalline structure of the nanoparticles was studied as a function of temperature and grain size. It is shown that the smaller the diameter of the nanocrystalline particle, the higher the compressive strength and the strain at which the maximum stress is reached. A decrease in grain size leads to a reduction in compressive strength, which is associated with the main mechanism of plastic deformation of nanocrystalline nanoparticles, namely, grain boundary sliding. At the first stage of deformation, the entire particle structure typically rotates until the maximum value of the stress vector projection onto the preferred slip plane is reached, which, in the case of a nanocrystalline structure, is determined by the mutual orientation of the grain boundaries. Grain boundaries elongated approximately along a single plane represent, in this case, the preferred slip plane. Full article

KTaO₃ (KTO) is a quantum paraelectric perovskite oxide which belongs to the cubic space group Pm$\overline{3}$m in a large temperature range. Polar optical modes with a T_1u symmetry of KTO are infrared-active and Raman-inactive according to the centrosymmetric exclusion principle of the selection rule. In general, the soft modes responsible for ferroelectric instability are infrared-active and Raman-inactive in the paraelectric phase. Therefore, there are still not enough studies on Raman-inactive soft modes and related phonon polaritons. In the present study, Raman-inactive polar modes and related polaritons of KTO crystals are studied by Terahertz Time-Domain spectroscopy (THz-TDS) and FTIR. The real and imaginary parts of a dielectric constant along the [100] axis are uniquely determined by transmission and reflection THz-TDS without any fitting in the low-frequency range between 6 and 225 cm⁻¹, which covers the two lowest-frequency polar modes. The reflectivity is determined by reflection FTIR in the range between 50 and 1200 cm⁻¹, and the complex dielectric constant is also estimated by the fitting in the range between 6 and 1200 cm⁻¹. The phonon–polariton dispersion relations of the real and imaginary parts of the polariton wavevector are also studied in the range between 6 and 1200 cm⁻¹. The crossover from photon-like to phonon-like polaritons and related polariton decay are observed, while no anomaly related to polariton scattering and coupling to other elementary excitations is observed in the polariton dispersion. Full article

Polymer-derived ceramics (PDCs) technology has been established for over five decades as a versatile route for the fabrication of advanced bioceramic materials. However, conventional processing routes for bioceramics, such as melt-quenching and sol–gel methods, still present significant limitations, including high processing temperatures, limited compositional flexibility, long processing times, and difficulties in fabricating complex and highly porous structures required for biomedical applications. In this context, increasing attention has been devoted to polymer-derived ceramics as an alternative approach for the fabrication of bioceramic materials. In this approach, preceramic polymers are converted into ceramic phases through thermal treatment in air or inert atmosphere (e.g., nitrogen), enabling low-temperature processing, high compositional flexibility, and precise control over phase evolution and microstructure. These features make the polymer-derived Ceramic route particularly attractive for the fabrication of complex and functional bioceramic architectures. This review provides an overview of the polymeric precursors employed for the synthesis of Polymer Derived Ceramic-based bioceramics, with particular emphasis on inorganic polymers, typically characterized by a siloxanic backbone, and the mechanisms governing their ceramization behavior. Special attention is given to emerging trends, including the integration of polymer-derived ceramics with additive manufacturing techniques and the development of functional systems for biomedical applications. Full article

The determination of the linear optical constants of solids is an important part of solid state optical characterization. Reflection spectroscopy and ellipsometry of surfaces or thin solid films represent established techniques to access those optical constants; however, they may suffer from ambiguity in the obtained optical constants. We discuss methods for identifying the physically meaningful solution from the solution multiplicity, making use of a proper combination of independent measurements. Elaborating contours of constant reflectance (iso-reflectance curves) facilitates the reliable identification of correct optical constants. A numerical criterion is further provided to select suitable combinations of measurements. The procedure is demonstrated through its application to simulated spectra of a Nb₂O₅ film in the spectral region where the onset of the fundamental absorption edge is observed. Full article

The persistent accumulation of antibiotic pollutants in aquatic environments poses potential threats to ecological safety and human health, highlighting the importance of developing low-cost, high-performance adsorbents for their efficient removal. In this study, a hydrothermal method was employed to prepare highly dispersed coal gangue-based calcium silicate hydrate (CSH) adsorbents. The structural characteristics, adsorption performance, and adsorption mechanisms of the material were systematically investigated. The as-prepared CSH exhibited an interwoven nanorod/nanosheet composite morphology with a more developed pore structure and a higher specific surface area. Kinetic analysis indicated that the adsorption process followed a pseudo-second-order model and involved both Boyd diffusion and intraparticle diffusion, with liquid-film diffusion likely serving as the primary rate-limiting step. Isotherm analysis revealed that the adsorption behavior was well described by the Langmuir model, suggesting monolayer adsorption, with a theoretical adsorption capacity (Q_m) of 129.29 mg/g. Thermodynamic analysis further demonstrated that the adsorption of CIP onto CSH was a spontaneous and endothermic process. Combined characterization results and theoretical calculations suggested that the adsorption of CIP by CSH was mainly governed by surface oxygen containing active sites, accompanied by electrostatic interactions, hydrogen bonding, and possible surface coordination effects. In addition, CSH maintained excellent adsorption performance and structural stability in the presence of coexisting ions, in tap water systems, and after repeated adsorption–desorption cycles. This study not only enables the high-value utilization of coal gangue but also provides new insights into the development of low-cost adsorbent materials for antibiotic removal. Full article

This work presents a comprehensive investigation of the thermal decomposition of nickel oxalate dihydrate as a precursor for the synthesis of porous NiO, with particular emphasis on microstructural formation and evolution. The transformations occurring at successive stages of the reaction were examined using SEM, TEM, N₂ adsorption, TG–DSC–MS, and in situ powder XRD, enabling the mechanisms of pore formation to be elucidated. The decomposition results in the formation of a porous pseudomorph composed of NiO nanoparticles with an average size of approximately 4 nm. This is the first time that the resulting microstructure has been shown to exhibit hierarchical, bimodal porous architecture. During dehydration, macropores are generated as a result of crystal fragmentation into blocks several hundred nanometers in size. Subsequent oxalate decomposition leads to the formation of mesoporous aggregates composed of nanometer-sized particles. The factors governing the parameters of the porous microstructure are analyzed. The resulting NiO, with its hierarchical pore structure, shows significant potential for applications in heterogeneous catalysis, gas sensing, and as electrodes for supercapacitors, lithium-ion batteries, and photoelectrochemical devices, as its macropores facilitate mass transport by reducing diffusion resistance while its mesopores provide a large accessible surface area for adsorption and catalytic reactions. Full article

An experimental investigation of the Cu-As-Sb ternary system in the Cu-rich region led to the identification of a new intermetallic phase, Cu₅(As,Sb)₂. The compound crystallizes in the orthorhombic Mg₅Ga₂-type structure (oI28, Ibam), analogous to the binary parent phase Cu₅As₂, with lattice parameters a = 5.968–5.977(1) Å, b = 11.550–11.565(3) Å, c = 5.530–5.573(3) Å. Similar to the parent Cu₅As₂ phase, the ternary compound forms with slight Cu under stoichiometry and exhibits a limited compositional range, with no continuous solid solubility between the binary and ternary phases. The phase formation, compositional stability, and decomposition behavior were systematically studied using a combination of powder and single-crystal X-ray diffraction (XRD, including Rietveld refinement), metallographic analysis with optical and scanning electron microscopy with energy-dispersive X-ray spectroscopy (LOM, SEM-EDXS), electron backscatter diffraction (EBSD) and thermal analysis (DTA, DSC). The results reveal that Cu₅(As,Sb)₂ is a high-temperature phase forming peritectically at 650–635 °C and stable only within a limited temperature interval. No continuous solid solubility exists between the ternary compound and the parent binary phase Cu₅As₂. Its formation occurs in strong competition with that of two other close neighboring solid-solution compounds, [Cu_3−x(As_1−ySb_y) (Cu₃P-type; hP24, P6₃cm) and Cu_3−x(As,Sb) (Cu₉TeSb₂-type; cP32, Pm−3n)], reflecting a complex interplay between composition, solubility ranges and thermal history. No evidence for the existence of high-temperature (HT) and low-temperature (LT) polymorphic phases was found for either the binary compound Cu₅As₂ or the ternary compound Cu₅(As,Sb)₂. Electrical resistivity measurements on a quenched sample indicate metallic behavior. These findings provide new insight into phase stability and structure–property relationships in Cu-As-Sb alloys and contribute to the understanding of competing intermetallic phases in this system. Full article

Piezoelectric semiconductor combines the unique properties of semiconducting characteristics and piezoelectric effect together, providing a universal methodology to modulate piezoelectric semiconductor device’s performance by simply introducing mechanical strain. To reveal the device physics beneath the piezoelectric modulation, in this work, a multiphysics COMSOL 6.0 simulation was employed to investigate the modulation of Si/GaN heterojunction PN diode characteristics via piezoelectric-induced interface polarization charges. The effects of charge polarity and density on forward recovery, reverse recovery, and irradiation responses were systematically analyzed. The results demonstrate that negative interface charges enhance carrier injection and accelerate device activation, whereas positive charges suppress overshoot and stabilize transient voltage behavior. During reverse recovery, negative charges shorten the storage delay and reduce the reverse peak current, improving the switching speed, whereas positive charges cause slower recovery. Under irradiation, the interface polarization charges modulate the photocurrent density by altering the depletion width and carrier collection efficiency; negative charges notably enhance the photocurrent in partially depleted devices. Furthermore, the influence of the polarization charges diminishes with increasing device length or doping concentration, as the built-in charge and electric field effects dominate. This study elucidates the physical mechanisms of piezoelectric charge control in Si/GaN heterojunctions and provides theoretical guidance for the design of high-speed, low-loss, and radiation-tunable power and optoelectronic devices. Full article

Two-dimensional (2D) heterostructures offer tunable electronic structures and synergistic interactions that enhance electrocatalytic activity beyond the limits of single-component materials. However, the same atomically thin interfaces that enable high performance also introduce inherent mechanical, chemical, and electronic vulnerabilities, giving rise to complex and coupled degradation pathways. In this review, we provide a systematic overview of degradation in 2D heterojunction electrocatalysts during electrochemical operation, covering failure mechanisms, operando characterization, and stabilization strategies. Degradation is governed by interfacial strain accumulation, bubble-induced stress and delamination, galvanic corrosion, and selective leaching, while stability can be improved through interfacial coupling, structural confinement, and controlled reconstruction. These insights provide practical design guidelines for developing robust 2D heterostructures for electrochemical energy conversion. Full article

Plastic pyrolysis is widely used to treat polyolefin-rich waste; however, wax byproducts generated during these processes are typically regarded as low-value intermediates. Here, a byproduct-compatible upcycling strategy is proposed to convert polyethylene (PE) pyrolysis wax into activated carbon, enabling integration of functional carbon production into existing recycling value chains. Thermal oxidation was employed to stabilize the wax prior to carbonization, and stabilization at 300 °C yielded a mechanically stable precursor with a high carbon yield. Subsequent carbonization and KOH activation at 900 °C produced an activated carbon (PEWax_AC) with a specific surface area of 1704 m²/g, exceeding that of a representative commercial activated carbon (1575 m²/g). Microstructural analysis revealed predominantly amorphous carbon with locally ordered domains. In symmetric supercapacitor cells, PEWax_AC exhibited higher capacitance at low rates and superior rate capability at high scan rates and current densities, along with reduced charge-transfer resistance. Specifically, PEWax_AC delivered a specific capacitance of 22.9 F/g at 5 mV/s and exhibited a rate retention of 18.6% from 0.1 to 7.0 A/g. These findings demonstrate that plastic pyrolysis wax is a viable and scalable carbon precursor for high-performance supercapacitor electrodes. Full article

Metal-chalcogenide compounds with perovskite-type compositions have drawn increasing attention for their optical properties for solar energy conversion. Herein, a new α-type polymorph of the ternary sulfide SrHfS₃ is described, crystallizing in the NH₄CdCl₃ structure type. The yellow-colored plate-shaped crystals were synthesized at 1173 K using an elemental tin flux in an evacuated sealed tube. Its crystal structure was characterized at room temperature using single crystal X-ray diffraction to form in the orthorhombic Pnma space group, with the refined cell parameters of a = 8.5041(4) Å, b = 3.8004(2) Å, c = 13.8935(6) Å, and V = 449.02(4) ų. The structure comprises five independent crystallographic sites, having one Sr, one Hf, and three S sites. The structure can be described as containing one-dimensional chains of distorted HfS₆ octahedra extending down the b-axis to form ${\displaystyle \genfrac{}{}{0pt}{}{1}{\infty }}[$HfS₃]²⁻ strips of edge-sharing octahedra. The Sr atoms act as charge-balancing space fillers in the structure. High-purity bulk samples of α-SrHfS₃ could be prepared for measurement of its bandgap by optical diffuse-reflectance spectroscopy, showing a direct bandgap of 2.1(1) eV. Results of electronic structure calculations are consistent with this bandgap and type. The conduction and valence band edges stem from the respective empty Hf d-orbitals and the filled S p-orbital states. In summary, crystal growth of the α-type polymorph of SrHfS₃ has been demonstrated using a Sn flux approach, which can facilitate future broader synthetic explorations at lower temperatures. Full article