Search Results (350)

Foraminiferal shell crystals incorporate the chemical signals of their environment during growth. The recorded information is extracted from the crystals via proxies and can be used to reconstruct paleoenvironments, paleoclimates, and the change of the latter. However, the information that is obtained from the biocrystals is often biased, due to structural and chemical modification of the crystals resulting from dissolution, precipitation, recrystallization, and overall, the transformation of the biologically formed crystals into their inorganic analogs. Electron-backscatter diffraction (EBSD) measurements and analysis render a wide range of information regarding crystallographic-structural attributes of the crystals, such as crystal-microstructure, crystal-texture, the misorientation interrelation of adjacent crystals, crystal-twin-generation and many more. We demonstrate in this study that diagenetic overprint of foraminiferal shell Ca-carbonate crystals can be identified by structural-crystallographic characteristics obtained from EBSD measurements. We investigated modern/pristine and fossil Trilobatus sacculifer shells and observed an undisturbed shell surface for both. Despite the latter, we demonstrate here that with an increase in the degree of fossilization and diagenetic overprint, there is an increase in recrystallized calcite in the shells and a decrease in twinned calcite. Twinned calcite is the hallmark of pristine T. sacculifer shells. We show that, with increasing degrees of shell overprint, crystal-microstructure, and crystal-texture, the frequency of the 60°|<001> twin misorientation is modified and propose to use structural-crystallographic attributes determined with EBSD measurements for the identification of recrystallized/overprinted foraminiferal carbonate. We discuss that disclosing low degrees of overprint is of main importance, as minor structure changes of overprinted shells are easily overlooked with SEM imaging. Nonetheless, these are readily identified with EBSD-measurements. Full article

This study aims to develop sustainable conductive nanocomposites based on poly(lactic acid) (PLA)/poly(ε-caprolactone) (PCL) blends reinforced with multi-walled carbon nanotubes (MWCNT) and graphene nanoplatelets (G), focusing on their multifunctional performance. The novelty lies in the production of hybrid nanocomposites based on PLA/PCL blends with MWCNT/G using conventional industrial processing techniques, enabling the development of eco-friendly nanocomposites with tailored electrical, mechanical, and electromagnetic properties. The nanocomposites were prepared by twin-screw extrusion followed by injection molding. Rheological, scanning electron microscopy (SEM), mechanical, thermal, thermomechanical, electrical conductivity, and electromagnetic shielding properties were systematically evaluated. From a rheological perspective, the PLA/PCL/MWCNT and PLA/PCL/MWCNT/G nanocomposites exhibited a plateau at low frequencies, associated with the formation of a percolated network. This was confirmed by the significant increase in electrical conductivity and electromagnetic shielding response. The morphology observed by SEM showed a refinement of the PCL phase in the PLA matrix with the incorporation of MWCNT. The PLA/PCL/MWCNT/G (4/2 parts per hundred resin, phr) nanocomposite showed a 309% increase in impact strength compared to neat PLA, while maintaining the heat deflection temperature (HDT). The elastic modulus exceeded 2300 MPa and accelerated the crystallization process by more than 15 °C compared to PLA, which makes it important to reduce injection molding time. Additionally, it exhibited the highest electrical conductivity level, around 6.79 × 10⁻⁵ S/cm, which resulted in improved electromagnetic shielding performance in the 8.2–18 GHz range, highlighting the synergistic effect between 1D and 2D fillers. The developed PLA/PCL/MWCNT and PLA/PCL/MWCNT/G nanocomposites demonstrate potential for antistatic applications, combining sustainability with multifunctional performance and industrial scalability. Full article

Batch crystallization processes are prone to batch-to-batch inconsistencies arising from operational uncertainties and equipment-induced noise. This study presents a Robustness-Aware Genetic Algorithm (RAGA) integrated with a Long Short-Term Memory (LSTM) digital twin for the design of robust crystallization procedures. The RAGA employs a hierarchical fitness function that strictly enforces a target median crystal size D₅₀ as the primary constraint while maximizing process yield as a secondary objective. Robustness is incorporated directly into the optimization by requiring candidate trajectories to satisfy the D₅₀ specification across five independent stochastic realizations with perturbed operating conditions. A candidate is promoted in the evolutionary search only if all five evaluations produce a predicted D₅₀ within ±2 µm of the target. The framework was applied to seeded cooling crystallization of creatine monohydrate across three target crystal sizes of 115, 125, and 135 µm. Robustness of optimal crystallization procedures was independently verified through 100-run Monte Carlo simulations under ±10% parameter perturbations with success defined as D₅₀ within ±5 µm of target. Experimental validation at laboratory scale confirmed that optimized procedures translate to practice, with two of three target sizes achieved within the ±5 µm specification and the third deviating due to the combined effect of LSTM prediction uncertainty and thermal lag. Despite having no embedded mechanistic knowledge, the optimizer successfully converged on physically coherent crystallization strategies. Its variations in seed loading, batch time, and cooling trajectory parameters remained entirely consistent with established principles of supersaturation management. The results demonstrate that embedding robustness directly within the evolutionary optimization loop enables consistent crystal size control using data-driven models. Full article

Biodegradable polymer blends are promising materials for flexible packaging films with tunable properties. In this work, poly(butylene succinate)/poly(vinyl alcohol) (PBS/PVOH) blown films were produced by twin-screw melt compounding followed by film blowing, and the effect of PVOH content on phase organization, processability, morphology, and functional performance was investigated. The blends showed phase-separated morphologies and composition-dependent structural evolution. DSC indicated that both polymers largely retained their crystallization ability, although the crystallinity decrease was more evident for PVOH. Rheological analysis revealed limited compatibility and increasing elastic response at higher PVOH contents, consistent with the formation of structured PVOH insoluble gel-like domains. SEM confirmed droplet–matrix morphologies, becoming coarser and more heterogeneous at high PVOH content, with film-blowing instability for PBS/PVOH 20/80. PVOH incorporation improved oxygen and water-vapor barrier properties and increased stiffness, but progressively reduced ductility. Model fitting supported the structure–property correlations, relating film performance to blend composition, morphology, and PVOH phase organization. Among the processable formulations, PBS/PVOH 80/20 showed the best balance between improved barrier properties and acceptable extensibility for food packaging application. Overall, PBS/PVOH blown films are promising biodegradable systems for flexible food packaging, provided that PVOH phase structuring is properly controlled. Full article

We report a new approach to enhance the photonic response of thin-film topological insulator Bi₂Se₃ by significantly reducing twin domains and antiphase disorder. The strategy employs closely lattice-matched trigonal substrates combined with surface structuring to preferentially seed a single rotational domain before epitaxy. Characterization using optical second harmonic generation (SHG), nonlinear optical tensor analysis, X-ray diffraction, and atomic force microscopy confirms the near-single crystal Bi₂Se₃ heteroepitaxial layers. These results show a clear six-fold symmetric sin²(3ϕ) SHG pattern at normal incidence, and a vanishingly small 100-to-1 peak-height ratio from X-ray pole-scans showing negligible twinning. These results show that this approach can yield near perfect single crystal heteroepitaxial Bi₂Se₃ whose photonic properties converge to those of bulk-grown single crystals. Full article

Cobalt-free Li-rich Mn-based layered oxides are promising cathode materials for next-generation lithium-ion batteries because of their high capacity and reduced reliance on cobalt resources. However, their practical application is still limited by low initial Coulombic efficiency, sluggish reaction kinetics, severe voltage decay, and progressive structural degradation during cycling. In this work, a Na-assisted sol–gel strategy was developed to construct a cobalt-free Li-rich Mn-based cathode with multiple twin boundaries, and the optimized sample with the composition of Li_1.13Na_0.06Mn_0.594Ni_0.219O₂ was denoted as SG-TB. Unlike conventional surface coating or elemental doping, this strategy focuses on regulating the bulk crystal framework through crystallographic defect engineering. Structural characterizations indicate that SG-TB contains repeatedly distributed twin-boundary-related interfaces, supporting the presence of multiple twin boundaries within the layered cathode. Benefiting from this structural feature, SG-TB delivers an initial Coulombic efficiency of 96%, an initial discharge capacity of 256 mAh/g, a discharge capacity of 167 mAh/g at 5 C, and a capacity retention of 77% after 200 cycles at 1 C. Further analyses suggest that the multiple twin boundaries help reduce electrochemical polarization, enhance Li⁺ diffusion kinetics, and improve structural retention during cycling. This work demonstrates that Na-assisted multiple twin-boundary engineering is an effective strategy for improving the reaction reversibility and structural stability of cobalt-free Li-rich Mn-based cathodes. Full article

Marine renewable energy systems, including offshore wind, tidal, and wave technologies, are central to global decarbonisation strategies but remain constrained by reliability-driven costs and uncertainty in long-term structural performance. Existing qualification approaches are largely based on empirical methodologies and deterministic safety factors that inadequately capture coupled degradation mechanisms operating in harsh offshore environments. This review presents a mechanism-based perspective on structural integrity in marine renewable energy systems by linking microstructure-sensitive deformation and damage processes with engineering-scale reliability assessment. Key degradation mechanisms, including corrosion–fatigue, hydrogen embrittlement, wear, and manufacturing-induced variability, are critically examined together with their interactions across multiple length scales. The review synthesises recent advances in multiscale modelling frameworks spanning crystal plasticity, damage mechanics, fracture mechanics, probabilistic reliability methods, and digital twin technologies. Particular emphasis is placed on the role of manufacturing variability, inspection-informed updating, and hybrid physics–data approaches in improving predictive capability and reducing uncertainty. The review identifies major limitations in current offshore qualification practice, including uncoupled degradation assumptions, insufficient representation of manufacturing effects, and limited integration of monitoring data within lifecycle assessment. Building on these findings, an integrated framework is proposed that combines multiscale modelling, manufacturing-aware qualification, adaptive inspection, and digital twin-enabled updating to support predictive and reliability-informed structural integrity assessment for next-generation marine renewable energy systems. Full article

Sulfur-containing medium-carbon microalloyed steel blooms are widely used for high-load automotive components, and reducing surface defects is important for improving product yield and lowering downstream processing costs. To address surface defects such as star cracks and microcracks in the continuous casting of these steel blooms, this study redesigned the mold flux on the basis of the steel’s solidification characteristics and crack susceptibility and carried out a twin-strand industrial comparative casting trial. Thermodynamic and thermophysical analyses indicated that the relatively high contents of S, Mn, and Ti/N in the steel promoted the precipitation of MnS and TiN–MnS complex inclusions along grain boundaries, severely weakening grain boundary cohesion. Meanwhile, the high specific heat capacity and low thermal conductivity further intensified thermal stress concentration in the solidifying shell, rendering the steel highly susceptible to cracking. Evaluation of the originally used mold flux (Flux A) revealed that its high melting temperature (1189 °C), long melting time (106 s), high break temperature (1170 °C), and poor crystallization behavior resulted in an excessively thin liquid slag layer (<5 mm) within the mold, making it difficult to provide adequate lubrication and stable heat transfer; these were key external factors inducing surface defects. Accordingly, the optimized mold flux (Flux B) was designed and prepared by increasing the basicity from 0.95 to 1.1, raising the Al₂O₃ content from 9.48% to 11.16%, increasing the F content from 4.93% to 5.58%, and reducing the carbon content from 13.85% to 6.97%. The rheological and crystallization properties of the flux were optimized in a coordinated manner, allowing uniform heat transfer through the crystalline slag layer while maintaining adequate lubrication. Industrial comparative trials demonstrated that Flux B stabilized the liquid slag layer at 8–10 mm, increased slag consumption to 0.56 kg/t, and significantly reduced surface defects such as star cracks and microcracks on blooms. The ultrasonic testing acceptance rate for rolled products increased to 98.6%, thereby meeting stringent quality requirements for the continuous casting of sulfur-containing, medium-carbon, microalloyed steel blooms. Full article

To reveal the long-term anti-aging mechanisms of rubber–plastic elastomer-modified asphalt in complex service environments and overcome the inherent defects of single polymer modifiers—namely their susceptibility to degradation or phase separation—this study prepared styrene-butadiene-styrene (SBS), low Mooney rubber (LMMR), and low-density polyethylene (LDPE)-modified asphalts. Simultaneously, an LMMR-LDPE rubber–plastic thermoplastic elastomer (TPE) was fabricated utilizing twin-screw extrusion technology and subsequently used to prepare a composite-modified asphalt. Three aging protocols were simulated: short-term thermo-oxidative aging (RTFOT), long-term pressure aging (PAV), and ultraviolet light aging (UV). A multi-scale quantitative characterization was conducted using a dynamic shear rheometer, Fourier transform infrared spectroscopy, and atomic force microscopy to evaluate the rutting factor, carbonyl index, and surface microroughness of each system before and after aging. The experimental results indicate that the coupled effect of long-term stress and thermal oxidation causes the most severe damage to the colloidal structure of modified asphalt. Conventional SBS-modified asphalt, due to its abundance of unsaturated double bonds, exhibits a sharp increase in the carbonyl index and aging index of the rutting factor after aging, making it highly susceptible to oxidative chain scission. Although LDPE-modified asphalt possesses chemical inertness, it is prone to crystalline phase separation under aging conditions, resulting in a microroughness distortion rate of up to 86.36%. In contrast, the LMMR-LDPE composite system, leveraging the high chemical stability of the saturated aliphatic carbon chain and the flexibility-enhancing and crystallization-inhibiting effects of LMMR, effectively reduces active oxidation sites and improves interfacial compatibility. This composite system exhibits the lowest carbonyl increment and rheological attenuation under all aging conditions, while effectively inhibiting the free migration and agglomeration of macromolecular components. The LMMR-LDPE composite modification technology effectively overcomes the inherent drawbacks of single polymers, such as susceptibility to degradation or segregation, demonstrating excellent long-term macroscopic rheological stability and microscopic phase morphology anti-aging capability. The present findings provide laboratory-scale mechanistic support for the design of durable rubber–plastic-modified asphalt systems, while further pilot-scale, economic, and field validation is still required before practical engineering application can be fully assessed. Full article

Magnesium alloys that are low density and have a high specific strength are widely utilized as lightweight structural materials. Due to their hexagonal close-packed crystal structure, plastic deformation in magnesium alloys is strongly limited in dislocation slip and mainly accommodated by deformation twinning, which results in distinct mechanical anisotropy and tension–compression asymmetry. This paper, centered on mechanism competition and microstructure regulation, systematically reviews the recent progress in the compressive mechanical responses of magnesium alloys. Key results reveal the cooperative and competitive mechanisms between slip and twinning, the significant controlling effects of temperature and strain rate on deformation behavior, and the effective design strategies of gradient and heterogeneous structures that achieve superior strength–ductility synergy. This review provides essential theoretical support for the development and performance optimization of high-performance magnesium alloys. Full article

In response to the growing demand for sustainable manufacturing, 3D printing using recycled polyethylene terephthalate (rPET) offers a novel waste-to-value conversion method. Although the application of rPET in additive manufacturing has attracted significant attention from both the academic and industrial sectors, substantial challenges impede its further development, notably the high processing shrinkage and poor mechanical properties of the final product. This study focuses on developing recycled PET-based composites with favorable processing, thermal, and mechanical properties. Regranulates were produced via twin-screw extrusion using PET flakes, multifunctional chain extenders, and short glass fibers (GFs). The rPET-GF composites were characterized in terms of their processing, thermal, thermomechanical, and mechanical properties. Epoxy-functional chain extender modification effectively increased the molecular weight and improved the processability, whereas GF reinforcement enhanced the tensile properties of both injection-molded and FDM-manufactured parts. A primary advantage of the rPET systems developed in this study is their delayed crystallization kinetics. These findings highlight the significant potential of the composites developed herein for extrusion-based additive manufacturing (MEX-AM), as delayed crystallization facilitates enhanced interfacial adhesion, lower volumetric shrinkage, and superior dimensional stability. Full article

This study investigated the comparative effects of various maleic anhydride-grafted polymeric compatibilizers such as polyethylene-graft-maleic anhydride, polypropylene-graft-maleic anhydride, polyethylene(alt)-graft-maleic anhydride and poly(styrene-ethylene/butylene-styrene)-graft-maleic anhydride on the final properties of polypropylene (PP) carbon nanotube (CNT) composites. Polypropylene nanocomposites (PP-CNT) were prepared by melt mixing using a laboratory scale twin-screw extruder. The mechanical test results showed that the incorporation of CNTs along with various compatibilizers increased the tensile strength (10.3%) and tensile modulus (24.2%). The tensile modulus and yield stress of the PP-CNT nanocomposites were significantly higher than those of the pristine PP. Differential Scanning Calorimetry (DSC) analysis revealed that the addition of CNTs slightly increased the melting temperature of the crystallization peaks. In the compatibilized PP-CNT composites, the CNTs were well dispersed to enhance the onset of degradation and maximum decomposition temperatures. The frequency-dependent rheological behaviors of PP-CNT nanocomposites indicated that the storage modulus (G′), loss modulus (G″), and complex viscosity (η*) PP increased for the compatibilized system. The XRD results indicated that the addition of CNTs and compatibilizers slightly affected the crystalline nature of PP. Scanning electron microscopic images of the fractured surfaces presented in the micrographs showed the brittle nature of the surface morphology of PP-CNT nanocomposites. Full article

The selection of deformation mechanisms in hexagonal close-packed (HCP) metals is strongly influenced by both crystallographic orientation and macroscopic deformation constraints. In commercially pure titanium, plastic deformation under constrained loading conditions involves a complex interplay between dislocation slip and deformation twinning, whose respective activation cannot be fully described by classical stress-based criteria. In this study, the mechanical origin of slip and twinning variant selection in commercially pure titanium subjected to plane strain compression is investigated experimentally. Plane strain compression is used as a canonical loading condition representative of constrained deformation paths encountered in sheet metal forming. Interrupted in-situ electron backscatter diffraction is combined with slip trace and twin variant analyses to identify the active deformation mechanisms at the grain scale. Resolved shear stress calculations show that stress-based criteria provide a necessary first-order condition for the activation of both slip and twinning systems. While the Schmid factor reasonably predicts part of the observed slip activity, it fails to uniquely determine the selection of active twinning variants. A kinematic analysis reveals that twinning variant selection is governed by the compatibility between the deformation induced by twinning and the macroscopic strain constraints imposed by plane strain compression. Only variants whose deformation accommodates compression along the loading axis, extension along the free in-plane direction, and minimal strain along the constrained in-plane direction are preferentially activated. These results demonstrate that deformation mechanism selection in HCP titanium under constrained loading conditions results from a combined effect of resolved shear stress and kinematic compatibility. The proposed framework provides a physically grounded basis for interpreting deformation-induced texture evolution and offers clear perspectives for the development of crystal plasticity models incorporating twinning under complex strain paths. Full article

We present a temperature-dependent photoluminescence (PL) study of solution-grown CsPbBr₃ bulk crystal and thin film, using one-photon and two-photon excitations. Twin planes are observed in X-ray diffraction spectra in crystal. In analyzing PL peak position and spectral widths as function of temperature, we find that the electron–phonon interaction is generally stronger in CsPbBr₃ crystals than in films. Moreover, with one photon excitation, emissions from excitons and trapped excitons are observed in CsPbBr₃ crystal. Under two-photon excitation, only the emissions from trapped excitons are observed in bulk crystal. Our work demonstrates that two-photon excitation PL is more sensitive to the trapped excitons inside CsPbBr₃, implicating an optical method to probe the inside quality of the crystal. Full article

Polyethylene terephthalate (PET) plays a pivotal role in the chemical fiber industry, constituting over 50% of fiber consumption. However, the reduction of the recycled fiber-derived viscosity of the PET significantly impacts its spinning performance and restricts its closed-loop recycling to high-value regenerated fibers. To address these limitations, this study explored the viscosity improvement of black and white waste fiber-derived polyester particles through a two-step process involving micro-glycolysis and self-polycondensation. Initially, a continuous micro-glycolysis of fiber-derived PET was carried out in a twin-screw extruder with ethylene glycol (EG), which effectively cleaves the ester bonds in the PET chains, generating oligomers with reactive hydroxyl end groups. Subsequently, these oligomers were repolymerized without purification, and a higher molecular weight regenerated PET with enhanced intrinsic viscosity was obtained with antimony ethylene glycolate (Sb-EG) as a catalyst. The results revealed that the intrinsic viscosity decreased exponentially with increasing EG dosage during glycolysis, reaching approximately 50% of the initial value at 0.2–2 phr EG dosages. Optimal viscosity enhancement was achieved at a polycondensation time of 1–3 h, resulting in improved thermal stability and reduced crystallization temperatures. Importantly, regenerated PET samples with EG dosages of ≤2 phr demonstrated intrinsic viscosities of about 0.70 dL/g, meeting the standard for spin-grade polyester fiber, which is used to produce regenerated polyester fibers. This recycling process is low cost, environmentally friendly, and easy to scale-up, contributing significantly to the development of industrial recycling of waste polyester fabrics. Full article