Search Results (89)

This study investigates the irradiation response of two L1₂-strengthened HEAs, (Ni₂Co₂FeCr)₉₂Ti₄Al₄ (TiHEA) and (Ni₂Co₂FeCr)₉₂Nb₄Al₄ (NbHEA), subjected to 6.4 MeV Fe³⁺ irradiation at 500 °C up to 30 dpa. Transmission electron microscopy (TEM) and atom probe tomography (APT) consistently showed that the Ti-containing HEA maintains L1_2-ordered structure and compositional stability better than Nb-containing alloys under irradiation. This difference is attributed to the distinct solute–defect interactions. Ti imposes a weaker hindering effect on vacancy mobility, allowing vacancies to remain mobile and participate in thermal reordering processes that counteract ballistic mixing, whereas Nb acts as a strong vacancy trap, suppressing the diffusion required for structural recovery. Irradiation-induced dislocation loops in the two alloys further exhibited different characteristics. TiHEA showed larger loops at lower number density, and NbHEA exhibited a higher density of smaller loops, consistent with their respective stacking fault energies and loop mobility. Nanoindentation results indicated that TiHEA exhibited a slightly higher irradiation hardening rate (27%) than NbHEA (23%), likely associated with a stronger order-strengthening contribution, given the better preservation of precipitate order in TiHEA under irradiation. These findings show the critical role of solute addition in designing radiation-tolerant high-entropy alloys. Full article

This study evaluated the ballistic performance and failure mechanisms of epoxy-based hybrid laminates reinforced with abaca/UHMWPE and pineapple leaf fiber (PALF)/UHMWPE fabrics fabricated by using vacuum-assisted hand lay-up. Ballistic tests utilized 9 mm full metal jacket (FMJ) rounds (~426 m/s impact velocity) under NIJ Standard Level IIIA conditions (44 mm maximum allowable BFS). This experimental test was complemented by finite element analysis (FEA) incorporating an energy-based bilinear fracture criterion to simulate matrix cracking and fiber pull-out. The results showed that abaca/UHMWPE composites exhibited lower backface signature (BFS) and depth of penetration (DOP) values (~23 mm vs. ~42 mm BFS; ~7 mm vs. ~9 mm DOP) than PALF/UHMWPE counterparts, reflecting superior interfacial adhesion and more ductile failure modes. Accelerated weathering produced matrix microcracking and delamination in both systems, reducing overall ballistic resistance. Scanning electron microscopy confirmed improved fiber–matrix bonding in abaca composites and interfacial voids in PALF laminates. The FEA results reproduced major failure modes, such as delamination, fiber–matrix debonding, and petaling, and identified stress concentration zones that agreed with experimental observations, though the extent of delamination was slightly underpredicted. Overall, the study demonstrated that abaca/UHMWPE hybridcomposites offer enhanced ballistic performance and durability compared with PALF/UHMWPE laminates, supporting their potential as sustainable alternatives for lightweight protective applications. Full article

Lead halide perovskites, exemplified by methylammonium (MA) lead iodide (MAPbI₃), combine strong optical absorption, long carrier diffusion lengths, and defect-tolerant electronic structure with facile processing, making them attractive for photovoltaics and radiation detection. Yet, their behavior under electron irradiation remains insufficiently understood, limiting deployment in space and dosimetry contexts. Here, we employ Monte Carlo simulations (Geant4) to model electron interactions with MAPbI₃ across energies from 0.1 to 100 MeV and absorber thicknesses from 10 μm to 1 cm. We quantify deposited energy, event statistics, energy per interaction, non-ionizing energy loss, and dominant radiation effects. The results reveal strong thickness-dependent regimes: thin photovoltaic-type layers (~hundreds of nanometers) are largely transparent to MeV electrons, minimizing bulk damage but allowing localized ionization, exciton self-trapping, and photoexcitation-driven ion migration. Although localized excitations can temporarily improve carrier collection under short-term exposure, their cumulative effect drives ionic rearrangement and defect growth, ultimately reducing device stability. In contrast, thicker detector-type films (10–100 μm) sustain multiple scattering and ionization cascades, enhancing sensitivity but accelerating defect accumulation. At centimeter scales, energy deposition saturates, enabling bulk-like absorption for high-flux dosimetry. Overall, electron irradiation in MAPbI₃ is dominated by electronic excitation rather than ballistic displacements, underscoring the need to optimize thickness and composition to balance efficiency, sensitivity, and durability. Full article

This paper addresses ballistic protection, which is an important element in the performance of any military equipment. Improving ballistic properties is a necessity for individual protection through the use of protective vests. In this study, plasma jet thermal deposition was performed on ballistic protection materials, steel plates from the ARMOX category, using both metallic and ceramic powders. The samples with appropriate dimensions, covered with these types of powders, were analyzed from a microstructural point of view to determine their mechanical properties and evaluate the improvement in ballistic protection level. Microstructural analyses by optical and electronic microscopy, SEM (Scanning Electron Microscopy), allowed the performance of complex analyses regarding the adhesion of the deposits to the base material. It was possible to evaluate the microstructure, thickness, uniformity, and porosity of the deposits and the microstructural aspects at the interface between the base material and the deposit. For the efficient use of these deposits, tribological studies were carried out on the mechanical properties through scratch and microindentation analyses. The paper concludes the results obtained for the two types of deposits, metallic and ceramic, to streamline their use to increase the ballistic protection of bulletproof vests used in individual protection in military equipment. Full article

Microdevices with dimensions comparable to a blood cell, i.e., tens of micrometers, show great potential for use in the human body. They can be adopted to identify the source of diseases, track their evolution and enhance the effectiveness of therapies, significantly improving patients’ quality of life. A key challenge is how to power the devices, which should ideally be performed wirelessly from a remote source. Piezoelectric micromachined ultrasonic transducers (pMUTs) offer a solution thanks to their ability to generate and collect energy via acoustic waves. In this work, numerical simulations of transmitter pMUT arrays are performed with the aim of generating an acoustic wave synchronized with a single pMUT or pMUT array receiver. The latter is intended for insertion in the human body. The characteristics required to switch on and power nano-electronics, in terms of generated voltage and electrical power at the receiver, are studied in ballistic gel, a material that mimics human organs. The focus is on a bio-compatible material for the piezoelectric layer, i.e., aluminum nitride enriched with scandium. Coupled electromechanical and acoustic simulations show that, of the considered pMUT devices, an 8 × 8 transmitter array combined with a single-device receiver (with a 50 µm pitch) or a 2 × 2 receiver array provide alternative options, with each offering advantages in terms of voltage amplitude or power at a steady state. The overall dimensions of the receiver, at a maximum of only 100 × 100 µm², is compatible with a future proof-of-concept biosensing platform test chip. Full article

We present a comprehensive first-principles study of nanoribbons made from the α-borophene sheet. This study looks at how edge shape, ribbon width, and magnetic ordering affect their structural, electronic, and transport properties. Ribbons cut along armchair (ac) and zigzag (zz) directions with various edge designs—armchair (a), single (s), and double (d) chains—are all stable. The double chain “dd” edges have the highest binding energies and the lowest edge energies, which aligns with near-bulk coordination. Our analysis of electronic structure and ballistic transport shows strong metallic characteristics in almost all configurations. Only the narrowest “3-ad” ribbon shows a small energy gap that disappears as the width increases. Zigzag ribbons (“zz”) display edge magnetism that depends on width, changing from non-magnetic to antiferromagnetic and finally to ferromagnetic states. Their spin-resolved transmission demonstrates clear spin filtering with polarization exceeding about 40%. Edge passivation affects these properties: hydrogen and fluorine reduce the “zz” edge magnetic moments and spin transport, while oxygen maintains finite magnetism. Near the Fermi level, many ribbons allow for multiple conducting channels. This feature supports low-resistance charge flow even for widths below 10 nm, while higher-energy transmission shows greater dependence on width. These findings position α-borophene nanoribbons as promising one-dimensional components for nanoelectronic connections and spintronic devices, combining high stability, adjustable edge magnetism, and strong metallic conduction. Full article

This study investigates the ballistic performance of epoxy matrix composites reinforced with raffia fabric, aiming to evaluate their potential as the second layer in multilayered armor systems (MAS), replacing conventional synthetic aramid (Kevlar™) laminates. Composite plates with different volumetric fractions of raffia fabric (10, 20, and 30%) were manufactured and integrated with a ceramic front layer (Al₂O₃/Nb₂O₅) in MAS structures, which were then subjected to ballistic impact tests using high-energy 7.62 mm caliber ammunition. The backface signature (indentation depth) measured in ballistic clay, used as a human body simulant, showed that only the 10% raffia-reinforced composite (ER10) met the National Institute of Justice (NIJ 0101.06) safety threshold of 44 mm. Higher raffia contents (20% and 30%) led to increased indentation, compromising ballistic integrity. Scanning electron microscopy (SEM) of the fractured surfaces revealed typical energy dissipation mechanisms, such as fiber rupture, fiber pull-out, and interfacial delamination. The results indicate that raffia fabric composites with 10% fiber content can serve as a cost-effective and sustainable alternative to Kevlar™ in personal armor applications, while maintaining compliance with ballistic protection standards. Full article

The environmental impact of petroleum-based materials in driving climate change has stimulated growing interest in natural lignocellulosic fibers (NLFs) as reinforcements for polymeric matrices. NLFs exhibit specific mechanical properties that, in some cases, rival those of synthetic fibers such as aramid, carbon, and glass. Among the wide variety of NLFs, kenaf has been extensively investigated in applications including textiles, construction, and furniture, owing to its long-established global cultivation. Previous studies have also demonstrated its potential as a reinforcement in polymeric matrices for engineering applications, including ballistic protection. In this context, the present work reports, for the first time, on the tensile and dynamic impact toughness of epoxy matrix composites reinforced with 10, 20, and 30 vol% kenaf fibers. The tensile toughness, defined as the area under the stress–strain curve up to fracture, ranged from 9.36 kJ/m² at 10 vol% to 52.30 kJ/m² at 30 vol% fiber content—representing a three- to tenfold increase compared to the neat epoxy matrix. In Izod impact tests, the composites containing 30 vol% kenaf fibers absorbed 22 times more energy than the neat epoxy, rising from 1.8 to 38.8 kJ/m². On average, the tensile toughness values exceeded those of the corresponding dynamic impact toughness. Scanning electron microscopy revealed the fracture morphology and highlighted the influence of the fibers under both toughness conditions. Full article

Aramid fibre has become a critical material for individual soft body armour due to its lightweight nature and exceptional impact resistance. To investigate its energy absorption mechanism, quasi-static and dynamic tensile experiments were conducted on Kevlar^® 29 plain-woven fabric using a universal material testing machine and a Split Hopkinson Tensile Bar (SHTB) apparatus. Tensile mechanical responses were obtained under various strain rates. Fracture morphology was characterised using scanning electron microscopy (SEM) and ultra-depth three-dimensional microscopy, followed by an analysis of microstructural damage patterns. Considering the strain rate effect, a viscoelastic constitutive model was developed. The results indicate that the tensile mechanical properties of Kevlar^® 29 plain-woven fabric are strain-rate dependent. Tensile strength, elastic modulus, and toughness increase with strain rate, whereas fracture strain decreases. Under quasi-static loading, the fracture surface exhibits plastic flow, with slight axial splitting and tapered fibre ends, indicating ductile failure. In contrast, dynamic loading leads to pronounced axial splitting with reduced split depth, simultaneous rupture of fibre skin and core layers, and fibrillation phenomena, suggesting brittle fracture characteristics. The modified three-element viscoelastic constitutive model effectively captures the strain-rate effect and accurately describes the tensile behaviour of the plain-woven fabric across different strain rates. These findings provide valuable data support for research on ballistic mechanisms and the performance optimisation of protective materials. Full article

The aim of the current study is to investigate the mechanical properties and ballistic performance of HARDOX 450 steel for defense applications in different conditions: uncoated, alumina-coated, and LINE X polyurea-coated. Tensile tests and Vickers microhardness measurements were conducted, along with fracture surface analysis using stereomicroscopy, scanning electron microscopy, and computed tomography. Experimental results showed that uncoated HARDOX 450 steel exhibited the highest strength and hardness, with ductile fracture features. Polyurea-coated HARDOX 450 steel samples retained good mechanical properties and demonstrated effective ballistic protection, including the containment of fragments. In contrast, alumina-coated HARDOX 450 steel samples exhibited reduced strength and ballistic resistance, attributed to the microstructural changes in HARDOX 450 steel caused by the high-temperature deposition process of alumina. Numerical simulations performed with the 5.56 × 45 mm bullet used in the simulation, along with its ballistic impact interaction with the Hardox 450 target model, aligned well with experimental ballistic impact results for all the samples. Overall, LINE X polyurea coating on HARDOX 450 steel proved to be the more suitable coating for applications requiring a balance of mechanical strength and ballistic impact resistance. Full article

This paper elaborates on the proposal of a new analytical model for a non-ballistic transport scenario for Schottky barrier carbon nanotube field effect transistors (SB-CNTFETs). The non-ballistic transport scenario depends on incorporating the effects of acoustic phonon (A-Ph) and optical phonon (O-Ph) electron scattering mechanisms. The analytical model is rooted in the solution of the Landauer integral equation, which is modified to account for non-ballistic transport through a set of approximations applied to the Wentzel–Kramers–Brillouin (WKB) transmission probability and the Fermi–Dirac distribution function. Our proposed model was simulated to evaluate the total current and transconductance, considering scenarios both with and without the electron–phonon scattering effect. The simulation results revealed a substantial decrease of approximately 78.6% in both total current and transconductance due to electron–phonon scattering. In addition, we investigated the impact of acoustic phonon (A-Ph) and optical phonon (O-Ph) scattering on the drain current under various conditions, including different temperatures, gate lengths, and nanotube chiralities. This comprehensive analysis helps in understanding how these parameters influence device performance. Compared with experimental data, the model’s simulation results demonstrate a high degree of agreement. Furthermore, our fully analytical model achieves a significantly faster runtime, clocking in at around 2.726 s. This validation underscores the model’s accuracy and reliability in predicting the behavior of SB-CNTFETs under non-ballistic conditions. Full article

In this study, we demonstrate that the Sn₂Se₂P₄ monolayer exhibits intrinsic anisotropic electronic characteristics with the strain-synergistic modulation of carrier transport and optoelectronic properties, as revealed by various levels of density functional theory calculations combined with the non-equilibrium Green’s function method. The calculations reveal that a-axis uniaxial compression of the Sn₂Se₂P₄ monolayer induces an indirect-to-direct bandgap transition (from 1.73 eV to 0.97 eV, as calculated by HSE06), reduces the hole effective mass by ≥70%, and amplifies current density by 684%. Conversely, a-axis uniaxial expansion (+8%) boosts ballistic transport (a/b-axis current ratio > 10⁵), rivaling black phosphorus. Notably, a striking negative differential conductance arises with the maximum I_peak/I_valley in the order of 10⁵ under the 2% uniaxial compression along the b-axis of the Sn₂Se₂P₄ monolayer. Visible-range anisotropic absorption coefficients (~10⁵ cm⁻¹) are achieved, where −4% a-axis strain elevates the photocurrent density (6.27 μA mm⁻² at 2.45 eV) and external quantum efficiency (39.2%) beyond many 2D materials benchmarks. Non-monotonic strain-dependent photocurrent density peaks at 2.00 eV correlate with hole effective mass reduction patterns, confirming the carrier mobility of the Sn₂Se₂P₄ monolayer as the governing parameter for photogenerated charge separation. These results establish Sn₂Se₂P₄ as a multifunctional material enabling strain-tailored anisotropy for logic transistors, negative differential resistors, and photovoltaic devices, while guiding future investigations on environmental stabilization and heterostructure integration toward practical applications. Full article

This paper presents a synthesis of failures of aramid fibers used in protective systems, with the help of SEM images obtained from three types of samples (panels made of fabrics with aramid fibers) tested against bullets, knives and spikes. This investigation is useful when using a step-by-step magnification and even macro photos in order to explain the mechanical failures of fibers. Several types of failure mechanisms (shear and tensile break, local bending, debonding from the matrix, fibrillation, local necking, etc.) were detected and discussed. Almost all of these failure mechanisms are present, with different densities of occurrence, in the studied panels made of aramid fibers. The description of failure mechanisms had to be conducted following the test conditions accurately. Failure mechanisms of aramid fibers are particularly relevant due to their specific molecular chains making them adequate for applications like ballistic and bladed weapon attacks. Full article

This study examines the microstructural evolution and mechanical properties of A500 bulletproof steel joints welded with austenitic stainless steel (ER371) and ferritic (T91) filler materials. While austenitic fillers are traditionally used in bulletproof steel welding to prevent cracking and hydrogen embrittlement, their lower hardness creates a potential weakness in welded joints. This research explores an alternative approach using a newly developed ferritic filler material to achieve strength matching with the base material. Detailed microstructural characterization was conducted using Optical Microscopy (OM) and Scanning Electron Microscopy (SEM), while mechanical properties were evaluated through tensile testing, impact testing, and hardness measurements. The results revealed significantly different mechanical behaviors between the two filler materials, with the ferritic filler achieving superior weld metal hardness (470 HV1) compared to the austenitic filler (185 HV1) in WZ. The fine-grained heat-affected zone (FGHAZ) exhibited the highest hardness (518 HV1) in A500-T91 joints and (480 HV1) in A500-ER371 joints, while ballistic testing demonstrated enhanced penetration resistance with the ferritic filler material. Full article

The development of efficient and sustainable armor systems is crucial for protecting bodies and vehicles. In this study, epoxy composites reinforced with natural lignocellulosic fibers (NLFs) from carnauba (Copernicia prunifera) were produced with 0, 10, 20, 30, and 40% fiber volume fractions. Their ballistic performance was evaluated by measuring residual velocity and absorbed energy after impact with 7.62 mm ammunition, as well as their application in a multilayer armor system (MAS). Scanning electron microscopy (SEM) was used to analyze fracture regions, and explicit dynamic simulations were performed for comparison with experimental tests. Residual velocity tests indicated a limit velocity (V_L) between 213 and 233 m/s and absorbed energy (E_abs) between 221 and 264 J, surpassing values reported for aramid fabric. All formulations showed indentation depths below the National Institute of Justice (NIJ) limit, with the 40% fiber sample achieving the lowest depth (31.2 mm). The simulation results correlated well with the experimental data, providing insight into deformation mechanisms during a level III ballistic event. These findings demonstrate the high potential of carnauba fibers in epoxy-based polymer composites, particularly as an intermediate layer in MAS, offering a sustainable alternative for ballistic protection. Full article