Search Results (414)

Femtosecond laser processing enables spatially controlled modification of the structure, composition, and functionality of advanced materials through highly localized energy deposition and laser–matter interaction mechanisms. This review discusses the role of ultrafast laser irradiation in the engineering of oxide-based functional systems, including functional oxides, oxide-containing layers, interfaces, and heterogeneous structures whose properties are substantially determined by an oxide component. The mechanisms governing laser-induced oxidation, phase transformation, elemental redistribution, defect generation, and hierarchical micro-/nanostructure formation are considered. Particular attention is given to the ability of femtosecond laser processing to create surfaces with tailored interactions with light, liquids, biological environments, and external stimuli, enabling responsive devices and advanced manufacturing strategies. Laser-modified oxide layers and nanostructured interfaces are analyzed as pathways for controlling surface energy, optical properties, chemical activity, and functional response. The relationship between laser-generated architectures and their applications in sensing, actuation, wetting control, and multifunctional systems is discussed. By connecting ultrafast laser surface engineering with emerging 4D manufacturing concepts, this review highlights femtosecond laser technologies as a versatile platform for designing systems with spatially programmed functionality and, where stimulus-dependent behavior is demonstrated, time-dependent performance. Such approaches provide opportunities for integrating adaptive oxide-based functional systems into advanced manufacturing. Full article

Ultrafast laser processing enables the creation of functional surfaces in metals, semiconductors, ceramics, polymers and other materials through spatially controlled nonequilibrium energy deposition. However, the resulting surface functionality cannot be explained solely by laser parameters or geometric features. Femtosecond irradiation induces a sequence of coupled processes, including nanoscale structuring, phase transformation, chemical modification, defect formation, and relaxation, which define the final surface state. This review introduces the Surface-by-Design concept, where functional surfaces are considered as engineered material states formed through controlled laser–matter interaction rather than as predefined patterns. Representative examples including laser-induced periodic surface structures, hierarchical micro/nanotextures, modified oxide layers, and laser-generated functional interfaces are analyzed in relation to wettability, tribological behavior, corrosion resistance, optical response, and other properties. The review further examines how advanced characterization, digital engineering, beam shaping, in situ diagnostics, and data-driven methods contribute to controlling surface evolution. Remaining challenges include reproducibility, scalability, and reliable prediction of functional behavior during service conditions. Future progress in femtosecond laser surface engineering will depend on the ability to control not only the generated morphology but also the evolving structural and physicochemical state of functional interfaces. Full article

Ti-6Al-4V has seen widespread adoption in the aerospace industry due to its advantageous material properties, but the alloy is costly to produce with vulnerable supply chains. Repair and remanufacture offer economic and environmental benefits over scrapping components. Powder-based additive-manufacturing processes have been investigated; however, coaxial wire laser metal deposition (LMD) remains understudied in repair scenarios, and the transfer of planar process parameters to inclined geometries for complex repairs has not been established. This paper identifies a process window for 1.2 mm Ti-6Al-4V wire and applies the parameters to repair a trapezoidal groove. Tensile and fatigue properties are evaluated, and fractography is conducted using optical and scanning electron microscopy. Findings show the transfer from planar to inclined geometry induces evolving geometric and thermal boundary conditions, including underbuilding and thermal accumulation. Nonetheless, the repair exhibited a yield strength of 868.2 MPa, an ultimate tensile strength of 920.5 MPa, and an elongation of 8.9%. Moreover, UFT revealed a fatigue performance of the repairs that was consistent with heat-treated SLM materials. Fractographic analysis revealed triangular defects and feedstock contamination that contribute to reduced repair properties. As such, this paper demonstrated that coaxial wire-LMD can be used to deposit material into complex geometries, but a complete, defect free repair was not achieved. Full article

Metal parts produced by directed energy deposition go through a complex thermal history during the deposition stage, which can result in heterogeneous microstructures and the accumulation of residual stress. While individual post-processing heat treatments are widely used to address these issues, the industrial logistics of manufacturing large components often demand specific sequences of combined treatments (e.g., applying stress relief prior to substrate detachment to prevent distortion, followed by high-temperature solubilization, or vice versa). The microstructural and mechanical consequences of altering this sequence remain underexplored. Therefore, this study aimed to investigate the effects of different post-processing heat treatment sequences on the mechanical properties of AISI 316L deposited through laser-directed energy deposition. Tensile and Charpy impact tests were carried out on the specimens under five conditions: (i) as-built; (ii) stress relief; (iii) solubilization; (iv) stress relief and solubilization; and (v) solubilization and stress relief. A statistical analysis of variance supported a comparison between each treatment’s influence on the mechanical properties under each condition. Furthermore, the typical microstructures were assessed by optical microscopy, scanning electron microscopy (SEM) equipped with electron backscatter diffraction (EBSD), and X-ray diffraction (XRD). The solubilization treatment reduced the ultimate tensile strength (from ~618 MPa to ~576 MPa) and the yield stress (from ~424 MPa to ~299 MPa), while no significant change was observed in elongation (ranging from 27% to 38%) due to high data dispersion. The stress relief, however, did not significantly change these mechanical properties. Considering the heat treatment combinations, the solubilization had a stronger impact on tensile stress than the stress relief, regardless of the treatment order. Impact resistance was not significantly affected by any of the heat treatments, maintaining an average of ~114 J. The solubilization treatment fully recrystallized the microstructure, while the stress relief did not promote any significant changes at an optical microscopy level. Ultimately, this study demonstrates that the microstructural transformations induced by the solubilization step dominate the final mechanical baseline, indicating that the sequence order is not a determining factor. This finding grants critical flexibility for industrial manufacturing logistics, allowing stress relief to be strategically applied when most convenient for dimensional stability without compromising final part performance. Full article

Photo-induced reactions, also known as photochemical reactions, are chemical processes that are initiated or driven by the absorption of light energy. Photo-induced reactions have been applied in a variety of fields from organic synthesis to polymer curation. One such application of much current interest is additive manufacturing (AM)—a technique used within a variety of fields to produce intricately shaped components. Currently, additive manufacturing is utilized within the solar, medicine, electronic, and nuclear application industries, making it a diverse and expansive system of production. Present reviewed AM production methods include laser powder bed fusion (L-PBF), stereolithography (SLA), direct energy deposition (DED), and selective laser sintering (SLS). However, the literature points to the need for expansion of feedstock capabilities as the horizon broadens to extreme environments like nuclear reactors, a solution which might be found in photolytic reaction synthesis. This review examines photo-induced synthesis most applicable to additive manufacturing, focusing on four key reaction types: oxidation–reduction, combustion, decomposition and polymerization. Past and present applications, future challenges, and emerging opportunities regarding photolytic reaction synthesis are analyzed. This assessment provides insights into the current state and future potential of these reactions in advancing additive manufacturing technologies. Full article

Residual stresses generated during laser powder bed fusion (LPBF) can cause substantial distortion in slender structures, compromising dimensional accuracy and structural reliability. This study tests the hypothesis that, under identical nominal processing conditions, geometry-dependent stiffness and constraint govern how the evolving thermally induced stress field is redistributed and manifested as warpage after support removal. Bridge-type TA15 titanium alloy cantilever specimens with different spans, thicknesses, and support densities were fabricated by LPBF, and their post-cut warpage was quantified by three-dimensional scanning. A coupled thermo-mechanical finite element model was validated against the measured deformation profiles and subsequently used to examine simulated stress evolution during deposition and redistribution after support removal. Cantilevers with different spans approached similarly high simulated surface tensile-stress plateaus in the constrained as-built state but exhibited markedly different measured warpage after cutting, showing that the as-built stress magnitude alone does not reliably rank post-release deformation. Increasing span reduced global flexural resistance and enlarged the effective bending arm, whereas increasing thickness enhanced flexural rigidity and suppressed curvature even when relatively high localized stress was retained. With the total support volume held constant, changing support density altered the system-level constraint through the combined effects of support-leg stiffness, support spacing, local thermal and mechanical response, and deformation compatibility. Together, these results provide an experimentally supported process-structure interpretation of LPBF cantilever distortion across controlled variations in span, thickness, and support distribution. Full article

Despite the growing preference for solid-state pH sensors due to their advantages over glass pH electrodes, their practical application is still limited by challenges, particularly in metal-oxide based systems. The main issue is their susceptibility to redox-active species such as dissolved oxygen, ascorbic acid, sulfides, and transition-metal ions. In this work, the effects of representative redox interferents, with particular emphasis on ascorbic acid, together with dissolved oxygen and potassium permanganate, were investigated and mitigated through the application of Ta₂O₅/Nafion overlayers. The solid-state metal-oxide pH-sensitive electrodes were fabricated with laser micro-etching of radio-frequency (RF) sputtered RuO₂ thin films deposited on ceramic Al₂O₃ substrates. The resulting RuO₂ electrodes exhibited excellent potentiometric pH sensing characteristics, including near-Nernstian sensitivity (58.8 mV pH⁻¹ at 25 °C), highly linear response over a wide pH range (pH 2–12, R² > 0.9999), minimal hysteresis (1.3 mV), low potential drift (2.9 mV h⁻¹), and fast response times (<30 s). Following on from our previous work, which demonstrated that the Ta₂O₅/Nafion solid-state sensor could measure beverage pH accurately, here we explain why that architecture works by systematically investigating the role of Ta₂O₅ and Nafion in suppressing redox interference and improving measurement stability in complex sample matrices. The results demonstrate that RuO₂ electrodes modified with combined Ta₂O₅/Nafion thin films exhibit significantly enhanced measurement stability compared to unmodified RuO₂ electrodes, owing to effective suppression of potential fluctuations induced by dissolved oxygen and representative redox couples, particularly those associated with ascorbic acid interference. These findings could give a promising strategy for improving the robustness and reliability of solid-state RuO₂-based pH sensors in complex electrochemical environments. Full article

Pitting corrosion is a more insidious and dangerous failure mode than uniform corrosion for protective coatings in marine environments, especially when sulfide ions (S²⁻) are present. In this work, Inconel 625 (IN625) and IN625-5 wt.% yttria-stabilized zirconia (YSZ) composite coatings were fabricated on 20G steel by laser-directed energy deposition (LDED) using optimized parameters. The coatings exhibit dense microstructures, with porosities of 1.87% ± 0.10% and 1.67% ± 0.10%, respectively. The pitting resistance was systematically evaluated by cyclic potentiodynamic polarization (CPP) and electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl solution without and with 20 ppm Na₂S. The CPP results show that the addition of YSZ decreases the pitting potential (E_pit) and protection potential (E_prot), indicating reduced resistance to pit initiation, while the smaller hysteresis loop suggests an improved tendency for repassivation. S²⁻ induces a notable drop in E_prot and impairs repassivation for both coatings, yet the IN625-YSZ coating retains a slightly higher E_prot than IN625. EIS analysis reveals that the IN625-YSZ coating in S²⁻-containing solution shows an increased R_ct of 2.738 × 10⁵ Ω·cm² compared with its counterpart in 3.5 wt.% NaCl solution, while the corresponding R_L decreases to 2.513 Ω·cm², suggesting a weakened outer barrier layer despite partial interfacial blocking. Post-corrosion morphology shows that YSZ particles act as preferential pitting nucleation sites; in sulfide-free solution they produce numerous shallow pits, whereas in S²⁻-containing solution they lead to larger and deeper pits. The results may provide a reference for the future design and evaluation of LDED-manufactured composite coatings under sulfide-containing marine environments. Full article

Three-dimensional (3D) bioprinting has emerged as a versatile biofabrication strategy that enables the precise, spatiotemporally controlled co-deposition of living cells, biomaterials, and bioactive agents, including growth factors, cytokines, and extracellular matrix (ECM) components, into geometrically defined 3D constructs. By translating digital design models derived from computed tomography (CT), magnetic resonance imaging (MRI), or computational modeling directly into physical tissue architectures, 3D bioprinting facilitates the assembly of hierarchically organized constructs that closely recapitulate the structural, mechanical, and functional characteristics of native tissues. The principal 3D bioprinting strategies are broadly classified into scaffold-based and scaffold-free approaches. Engineered bioinks, whether formulated as cell-laden natural, synthetic, or composite polymer hydrogels, tissue-derived decellularized ECM (dECM) components, or pure cellular spheroids and organoids, constitute the cornerstone of these biofabrication platforms. Scaffold-based 3D bioprinting comprises extrusion-based, droplet-based (inkjet and drop-on-demand), light-based vat photopolymerization (stereolithography and digital light processing), and laser-assisted bioprinting based on laser-induced forward transfer (LIFT). Each of these modalities imposes distinct constraints on bioink rheology, crosslinking mechanisms, spatial resolution, throughput, and post-printing cell viability; consequently, a specific 3D bioprinting strategy is selected according to the specific requirements of the target tissue application. Scaffold-free 3D bioprinting and bioassembly techniques, including the Kenzan method, aspiration-assisted bioprinting, magnetic bioprinting, and other field-directed tissue assembly approaches, enable the fabrication of spheroid- and organoid-based constructs without the necessity for exogenous biomaterial scaffolds. Because native tissues exhibit diversity in cellular composition, ECM architecture, mechanical properties, and physiological function, no individual bioprinting platform or bioink formulation serves as a universal 3D bioprinting solution. The engineering of biomimetic tissue constructs, therefore, requires the selection of application-tailored fabrication approaches. Under this biofabrication paradigm, 3D bioprinting has been applied across a wide range of tissue engineering targets, including skin, bone, cartilage, osteochondral interfaces, cardiac and vascular tissue, neural structures, ocular, dental, and adipose tissue. This review discusses recent advances in scaffold-based and scaffold-free 3D bioprinting applications for tissue engineering and regenerative medicine across diverse tissue systems. Full article

This review aims to analyze defect-driven thermoelectric decoupling in pulsed laser deposition (PLD)-grown oxygen-deficient ${WO}_x$ and tungsten Magnéli thin films. While transition metal oxides offer a non-toxic, abundant alternative to conventional thermoelectrics, tungsten oxide stands out due to the profound impact of sub-stoichiometry on its transport properties. We systematically evaluate how ordered oxygen vacancies and crystallographic shear planes transform insulating ${WO}_3$ into sub-stoichiometric phases exhibiting metallic-like conductivity. Specifically, we analyze how the delocalization of W$5d$ electrons around defect-rich regions induces electronic states near the Fermi level, decoupling the Seebeck coefficient from electrical conductivity. Simultaneously, we discuss how these engineered defect networks and shear planes selectively enhance phonon scattering, drastically suppressing lattice thermal conductivity without hindering electronic transport. By establishing PLD as an effective approach for precise oxygen stoichiometry and defect architecture control, this review highlights the high-temperature potential of tungsten Magnéli phases and outlines future pathways to maximize their thermoelectric figure of merit ($ZT$). Full article

Metal additive manufacturing (MAM) is extensively being utilized by aerospace and automobile industries to produce parts with complex geometries with minimum lead time, no material wastage, and higher dimensional accuracy. Additively manufactured (AMed) AlSi10Mg alloys are one of the most used alloys in lightweight structural applications due to their tailored microstructure and suitable mechanical properties for these applications. This review critically presents the recent and current developments on the AlSi10Mg alloys fabricated using various MAM methods such as laser powder bed fusion (LPBF), directed energy deposition (DED), and electron beam melting (EBM). Special attention is given to the establishment of linkage among the process–structure–property–performance of the AMed AlSi10Mg alloy. This review highlights that LPBF-fabricated AlSi10Mg alloys typically exhibit a finer cellular α-Al matrix with a continuous Si network and provide superior strength with lower ductility. DED samples showed a coarser dendritic microstructure and exhibited moderate strength and ductility. However, EBM fabrication leads to near-equilibrium microstructures and exhibits reduced strength with improved ductility due to higher processing temperatures and thermal gradients. The effects of MAM methods, build orientations, and their process parameters on the microstructural evolution and mechanical performance of AlSi10Mg alloy products are extensively investigated. The influence of post-processing methods is also discussed, which reveals their critical role in the anisotropy, ability to mitigate defects like porosity and a lack of fusion, surface irregularities and material strengths. Despite showing steady progress in this area, several challenges like residual stresses, process-induced porosity, and limited availability of universal standardizations remain unaddressed. Such issues raise doubts about the reproducibility and adoption of the fabricated components on a large scale. This review study is likely to help the aerospace and automobile industries in the printing of structural components using an optimized parameter range, leading to an optimized microstructure and balanced mechanical properties with minimum defects. This review provides a comprehensive comparison of the LPBF, DED, and EBM processing routes for AlSi10Mg alloys by correlating the processing parameters to the microstructural evolution, mechanical properties, and fatigue performance. It indicates that the optimization of process parameters and post-processing treatments are the key strategies to reduce defects, control the microstructure, and obtain a good balance between strength and ductility. The review also points out the existing research gaps and future directions towards reliable industrial implementation of AMed AlSi10Mg components. Full article

Aluminum volatilization during laser deposition manufacturing severely deteriorates the microstructure and service performance of TiAl alloys, causing aggravated brittleness, elevated crack sensitivity and structural degradation. To tackle this issue, this work proposes an aluminum composition compensation strategy based on Ti-48Al-2Cr-2Nb pre-alloyed powder, with three mass fractions of elemental Al (15 wt.%, 20 wt.% and 25 wt.%) added to systematically investigate their influences on the macroscopic cracking behavior, microstructure evolution, phase constitution and mechanical properties of the deposited alloys. The results demonstrate that 15 wt.% Al addition achieves crack-free laser deposition, yielding a uniform microstructure dominated by γ-TiAl phase with dispersedly distributed TiAl₂ and minor B2 phases as well as low residual internal stress. No α₂-Ti₃Al phase is detected in all samples, as the Al-rich composition shift thermodynamically suppresses the stability of Ti-rich α₂ phase. Excessive Al addition induces the massive formation of brittle Al-rich intermetallics (TiAl₂ and TiAl₃), which gradually evolve from isolated particles to a continuous network structure, leading to a sharp increase in crack susceptibility. Al addition continuously improves the microhardness of the alloys, and the 25 wt.% Al sample attains the maximum hardness of 522.3 HV, benefiting from the synergistic effects of grain refinement strengthening and second-phase strengthening. The 15 wt.% Al sample delivers the optimal comprehensive mechanical performance, with an ultimate tensile strength of 550.2 Mpa and a fracture elongation of 0.76%, where the finely dispersed TiAl₂ precipitates exert a remarkable dispersion strengthening effect without causing severe embrittlement. This work provides a feasible experimental basis and technical reference for crack control and property optimization of laser deposition-manufactured TiAl alloys. Full article

Additive manufacturing (AM) has emerged as a transformative manufacturing technology for producing complex components with unprecedented design flexibility. However, the widespread application of AM parts in tribological environments is often limited by inherent defects such as high surface roughness, porosity, residual stresses, anisotropy, and weak interlayer bonding, which adversely affect friction, wear resistance, and tribocorrosion performance. This review critically examines the tribological behavior of AM materials and components, emphasizing the influence of processing routes, material selection, secondary reinforcing phases, and microstructural evolution on tribological performance. Particular attention is given to surface engineering strategies, including thermal spray coatings, laser surface treatments, plasma electrolytic oxidation, vapor deposition technologies, and mechanical surface modification techniques for mitigating AM-induced defects and improving surface durability. Recent advances in machine learning (ML) and artificial intelligence (AI) for wear prediction, process optimization, and intelligent tribological monitoring are also discussed. The review highlights the relationships among manufacturing parameters, surface integrity, and wear mechanisms, while identifying key challenges associated with process variability, long-term reliability, and industrial implementation. Future research should focus on multifunctional surface systems, smart coatings, real-time condition monitoring, and data-driven design approaches to accelerate the deployment of tribologically optimized AM components in aerospace, biomedical, automotive, and energy applications. Full article

High-temperature corrosion severely impairs the service life of boiler heating tubes and threatens the safe and economical operation of thermal power units. With diversified fuels (coal, biomass and refuse-derived fuels) and continuously elevated operating parameters (steam temperature exceeding 620 °C for ultra-supercritical units), boiler heating surfaces are exposed to increasingly complex corrosive environments. High-temperature oxidation, sulfidation, chlorination, molten salt hot corrosion and deposit-induced multi-factor coupled corrosion coexist and exacerbate each other. This paper adopts a four-dimensional analytical framework of “mechanisms–technologies–materials–evaluation” to systematically summarize relevant research progress. From the perspective of corrosion mechanisms, the evolution of understandings from single high-temperature oxidation to multi-factor coupled corrosion is reviewed. In terms of surface coating technologies, seven mainstream processes including HVOF/HVAF spraying, plasma spraying, cold spraying, laser cladding and weld overlay are compared in terms of preparation characteristics and engineering applicability. For coating materials, twelve material systems such as NiCr alloys, MCrAlY, cermets, Fe-based amorphous/nanocrystalline alloys and high-entropy alloys are evaluated for their corrosion resistance under diverse service conditions. As for monitoring and evaluation, this work introduces full-range corrosion management technologies covering electrochemical monitoring, non-destructive testing, numerical simulation and life assessment. Finally, the paper discusses the application prospects of gradient coating design, AI-assisted material screening and digital twin technology, and points out key research gaps including long-term service reliability verification of coatings and quantitative prediction models for multi-factor coupled corrosion. Full article

The long-term stability of biodegradable polymer coatings deposited by matrix-assisted pulsed laser evaporation (MAPLE) remains insufficiently understood, particularly under ultraviolet irradiation conditions where photochemical effects may accompany material transfer. In this work, thin films of poly(lactide-co-caprolactone)-block-poly(ethyleneglycol)-block-poly(lactide-co-caprolactone), also known as PLCL-PEG-PLCL, are deposited from chloroform solutions by UV-MAPLE using a nanosecond Nd:YAG laser operating at 266 nm over a wide laser fluence range (0.25–0.9 J/cm²). The effect of laser fluence on the morphological, structural, and chemical evolution of the coatings is investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDS), focused ion beam scanning electron microscopy (FIB-SEM), and X-ray diffraction (XRD). At low laser fluence, relatively homogeneous coatings are obtained while largely preserving the characteristic functional groups of the triblock copolymer. Increasing the laser fluence progressively induces surface restructuring phenomena, including droplets, wrinkles, and the appearance of highly symmetric faceted structures. These entities develop preferentially in samples deposited at elevated fluence and frequently appear only after prolonged aging under ambient conditions, revealing delayed recrystallization behaviour associated with metastable species generated during the deposition process. EDS analyses reveal localized chlorine enrichment within the faceted structures, while FIB-SEM investigations show porous internal morphologies. XRD confirms that the polymer matrix remains predominantly amorphous. The combined observations suggest that UV-MAPLE deposition from chloroform involves not only physical material transfer but also photochemical processes that promote decomposition, recombination, and delayed crystallization phenomena. A phenomenological model describing the successive stages of surface evolution, aging, and recrystallization is proposed. These results provide new insight into the long-term evolution of laser-deposited biodegradable polymer coatings and highlight the importance of solvent selection and processing conditions in determining their stability. Full article