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Silver-Gold Bimetallic Alloy versus Core-Shell Nanoparticles: Implications for Plasmonic Enhancement and Photothermal Applications
摘要： Bimetallic plasmonic nanoparticles enable tuning of the optical response and chemical stability by variation of the composition. The present numerical simulation study compares Ag-Au alloy, Ag@Au core-shell, and Au@Ag core-shell bimetallic plasmonic nanoparticles of both spherical and anisotropic (nanotriangle and nanorods) shapes. By studying both spherical and anisotropic (with LSPR in the near-infrared region) shapes, cases with and without interband transitions of Au can be decoupled. Explicit comparisons are facilitated by numerical models supported by careful validation and examination of optical constants of Au-Ag alloys reported in literature. Although both Au-Ag core-shell and alloy nanoparticles exhibit an intermediary optical response between that of pure Ag and Au nanoparticles, there are noticeable differences in the spectral characteristics. Also, the effect of the bimetallic constitution in anisotropic nanoparticles is starkly different from that in spherical nanoparticles due to the absence of Au interband transitions in the former case. In general, the improved chemical stability of Ag nanoparticles by incorporation of Au comes with a cost of reduction in plasmonic enhancement, also applicable to anisotropic nanoparticles with a weaker effect. A photothermal heat transfer study confirms that increased absorption by the incorporation of Au in spherical Ag nanoparticles also results in an increased steady state temperature. On the other hand, anisotropic nanoparticles are inherently better absorbers, hence better photothermal sources and their photothermal properties are apparently not strongly affected by the incorporation of one metal in the other. This study of the optical/spectral and photothermal characteristics of bimetallic Au-Ag alloy versus core-shell nanoparticles provides a detailed physical insight for the development of new taylor-made plasmonic nanostructures.
关键词： Localized Surface Plasmon Resonance (LSPR),Au@Ag core-shell,Ag-Au alloy,Ag@Au core-shell,Bimetallic plasmonic nanoparticles,Photothermal applications
更新于2025-09-23 15:21:01
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Ideal alloys of two donor isomers with non-covalently conformational locking for ternary organic solar cells
摘要： Ternary organic solar cells (OSCs) based on the alloy model have great potential in maximizing the improvement of device performance due to the probability of simultaneously enhancing the photocurrent through morphology optimization and improving open circuit voltage (Voc) by energy level adjustment. However, rationally designing compatible materials and constructing an effective alloy remain difficult. In this manuscript, two donor isomers, BT-TO-ID and BT-OT-ID with non-covalently conformational locking of alkoxy groups at different position, were designed and synthesized to obtain an ‘‘ideal alloy’’. A linearly tunable Voc was observed between the Voc limitation of binary blends with the changes of the composition across the full range, indicating the behavior of an ideal alloy in the ternary blends. A face-on molecular packing and an appropriate phase separation was observed in the ternary blends due to the strong interactions between the two isomers, which facilitated charge transport and charge recombination suppression. Notable improvements of 76% and 29% in device performance were obtained for the ternary blends compared with BT-OT-ID based and BT-OT-ID based binary devices, respectively. Therefore, this work provided a probable molecular design strategy to guide the construction of an effective alloy in ternary OSCs.
关键词： Open circuit voltage,Non-covalently conformational locking,Alloy model,Device performance,Molecular packing,Phase separation,Ternary organic solar cells,Donor isomers
更新于2025-09-23 15:21:01
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Influence of laser weld shape on mechanical and fatigue behaviour of single lap laser welded joints
摘要： Traditional manufacturing processes, like arc welding and resistance spot welding, are still the main welding processes to join structural components used across the on/o?-road vehicle industry. Due to the abundance of data, experiences and insights over the decades of usage, lot of fatigue design data has been generated for different joint geometries produced using these methods. The laser welding process has excellent capabilities to join thin sheet metal structures with minimum heat input resulting into lower deformation and improved productivity that offers significant benefit as compared to the arc and resistance welding processes. However, due to the agility of designing joint configurations and limited availability of understanding regarding the fatigue behaviour of laser welded joints, the need arises for the fatigue design data. Most of the research presents the use of straight linear shape laser welds and limited knowledge exist regarding the influence of shape of laser welds on mechanical and fatigue performance of the laser welded joints. The laser welded joints produce small notch like radius at the root of laser weld which could act as a stress raiser causing early crack initiation. For this work, C-shape laser weld has been selected as the geometric shape in comparison to the straight linear shape of laser weld produced on a series of single lap joints. Detailed fatigue experimental investigation has been carried out for linear and C-shape laser welded joints tested in 3 different orientations with respect to the applied cyclic load and several different R-ratio’s and the results are compared. The metallurgical studies have been carried out to understand the failure mode and micro-hardness variations across the weld and heat affected zone. Further, the residual stress profiles have been compared for the C-shape laser weld with the linear welds using detailed X - Ray Diffraction based residual stress measurement.
关键词： Laser Weld,Ultra-high strength steel,C Shape,Crack propagation,High strength low alloy steel,Crack initiation
更新于2025-09-23 15:21:01
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Effects of laser surface melting on crystallographic texture, microstructure, elastic modulus and hardness of Tia??30Nba??4Sn alloy
摘要： The biocompatibility of orthopedic implants is closely related to their elastic modulus and surface properties. The objective of this study was to determine the effects of cold rolling, recrystallization and laser surface melting (LSM) on the microstructure and mechanical properties of a biphase (α″+β) Ti?30Nb?4Sn alloy. X-ray diffraction (XRD) texture analysis of the cold-rolled substrate revealed the [302]α″//ND texture component, while analysis of the recrystallized substrate showed the [302]α″//ND and [110]α″//ND components. The β-phase texture could not be directly measured by XRD, but the presence of the [111]β//ND texture component was successfully predicted by considering the orientation relationship between the α″ and β phases. Nanoindentation measurements showed that the elastic modulus of the cold-rolled substrate (63 GPa) was lower than that of the recrystallized substrate (74 GPa). Based on the available literature and the results presented here, it is suggested that this difference is caused by the introduction of crystal defects during cold deformation. The combined nanoindentation/EBSD analysis showed that the nanoindentation results are not affected by crystal orientation. LSM of the deformed alloy produced changes in hardness, elastic modulus and crystallographic texture similar to those produced by recrystallization heat treatment, creating a stiffness gradient between surface and substrate.
关键词： laser surface melting,stiffness-graded material,crystallographic texture,cold rolling,titanium alloy,recrystallization
更新于2025-09-23 15:21:01
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Computational Assessment of Thermokinetics and Associated Microstructural Evolution in Laser Powder Bed Fusion Manufacturing of Ti6Al4V Alloy
摘要： Although most of the near non-equilibrium microstructures of alloys produced by laser powder bed fusion (LPBF) additive manufacturing (AM) are being reported at a rapid rate, the accountable thermokinetics of the entire process have rarely been studied. In order to exploit the versatility of this AM process for the desired properties of built material, it is crucial to understand the thermokinetics associated with the process. In light of this, a three-dimensional thermokinetic model based on the finite element method was developed to correlate with the microstructure evolved in additively manufactured Ti6Al4V alloy. The computational model yielded the thermal patterns experienced at given location while building a single layer through multiple laser scans and a whole part through multiple layers above it. X-ray analysis of the resultant microstructure confirmed the presence of acicular martensitic (α′) phase of (002) texture within the build-plane. Computationally predicted magnitude of the thermal gradients within the additively manufactured Ti6Al4V alloy in different directions (X, Y, and Z) facilitated the understanding about the evolution of grain morphology and orientation of acicular martensite in prior β grains. The scanning electron microscopy observations of the alloy revealed the distinct morphology of phase precipitated within the martensitic phase, whose existence was, in turn, understood through predicted thermal history.
关键词： Thermokinetics,Additive manufacturing,Microstructural evolution,Laser powder bed fusion,Ti6Al4V alloy
更新于2025-09-23 15:21:01
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Fatigue behaviors of foreign object damaged Ti-6Al-4V alloys under laser shock peening
摘要： Two-sided and simultaneous laser shock peening (TSLSP) was used to strengthen the Ti-6Al-4V titanium alloy. The fatigue crack growth rate of the specimens was investigated by fatigue test. The results show that both direct TSLSP (TSLSP-D) and indirect TSLSP (TSLSP-I) can reduce the fatigue crack growth rate by producing high magnitude compressive residual stress. The maximum fatigue life increases by 94% (TSLSP-D) and 169% (TSLSP-I) compared with the original specimens. Moreover, the TSLSP-D results show decreased resistance to foreign object damage because of decreased plasticity while the TSLSP-I simultaneously achieves superior foreign object damage resistance and fatigue performance.
关键词： Fatigue performance,Foreign object damage,Two-sided and simultaneous laser shock peening,Titanium alloy
更新于2025-09-23 15:21:01
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The effects of growth TiO <sub/>2</sub> nanotubes on forged Ti <sub/>6</sub> Al <sub/>4</sub> V alloy and selectivelaser sintered Ti <sub/>6</sub> Al <sub/>4</sub> V alloy surfaces for environment and medical applications
摘要： The paper describes the effect of growth TiO2 nanotubes on titanium surfaces by anodic oxidation for environmental and medical applications. The importance of the metallurgical state of TiAl6V alloy on the growing of TiO2 nanotubes by anodization will be highlighted. Starting from the possibility of obtaining the TiO2 nanotubes, the paper presents results on TiO2 nanotubes grown by electrochemical anodization method, using a solution containing HF 0,4% and having as electrodes, graphite as cathode and titanium alloy specimens obtained by two technologies: by cold plastic deformation as well as by additive manufacturing process SLS, as anode. So, the nanotubes were produced by anodization and analysed by scanning electron microscopy. The aim of this paper is to compare the electrochemical formation of TiO2 on the surface of both specimens knowing that the titanium alloys and its oxides are used in many biomedical and environmental applications, thus providing the importance of nanotubes and the fact that their properties open doors in these fields.
关键词： medical applications,TiO2 nanotubes,environmental applications,anodic oxidation,Ti6Al4V alloy
更新于2025-09-23 15:21:01
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Application of high power pulsed nanosecond fibre lasers in processing ultra-thin aluminium foils
摘要： This study is directed at developing a micro-scale laser scoring process and understanding the laser-material interaction in ultra-thin aluminium foils (160 ??m thickness). The research is carried out by the latest generation of nanosecond pulsed ?bre lasers manufactured by SPI Lasers. Presented comparative analysis of 70 W and 120 W laser types gives important insights for laser functionality and can provide recommendations for scalability of the process and quality assurance. High average power lasers were used to meet the requirement of high processing speed in aluminium foils. Scoring in aluminium foils was analysed using the fundamental laser-material interaction parameters that fully determine the way the material responds to the laser energy independent of the laser system. This approach permits transferring the results from the micro-scale laser process between various laser systems. Energy density and laser power density calculated for considered beam spot area at various frequencies were found to be the parameters that determine the scoring ablation depth in the range of 40 ??m–60 ??m. Microscopic examination of the ablation depth and score quality was carried out by an LED illumination 3D microscope. The SEM micrographs indicated minor growth of material debris from the ejected material.
关键词： Aluminium alloy,Scoring,Pulsed wave,Processing,Nanosecond ?bre laser,Ablation
更新于2025-09-23 15:21:01
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Laser printing of micro-electronic communication systems for smart implants applications
摘要： Endow the implant with intrinsic communication system between sensors and actuators or between implant and patient is a key factor for its long-term success. The capacity of early diagnosis of failures and the ability to remedy them are necessary to minimize expensive complications and reducing revision procedures. Ti6Al4V is the most used titanium alloy for implant’s fabrication. In this sense, this work presents a promising approach to print communication systems by using laser technology, aiming integrate the smart components on titanium implants. Laser has been employed as a versatile tool to modify the surface in different ways, such as texturing, oxidizing and sintering. Silver wires have been printed on Ti6Al4V surface in order to conduct electrical current. To minimize current loss for the substrate, titanium oxide layer has been produced by different methods (laser and anodization). Laser sintering (LS) has been also compared to a conventional method (Hot-pressing- HP) to consolidate the silver powder into the cavities. In comparison to the conventional techniques, laser demonstrated to be a competitive approach to oxidizing the surface and also for consolidating the micro-wires on Ti6Al4V surface. Consequently, the micro-wires printed by laser approach presented satisfactory results in terms of electrical resistance, actuating as the conductor path for electrical current, with values of 0.0131 Ω, which is similar to the resistance of the wire printed in an insulator substrate.
关键词： Ti6Al4V titanium alloy,Laser oxidation,Implants,Laser surface modification,Nd:YAG laser,Laser sintering
更新于2025-09-23 15:21:01
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EBSD characterization of the L-605 Co-based alloy welds processed by pulsed Nd:YAG laser welding
摘要： Herein, pulsed Nd:YAG laser welding of the L-605 Co-based alloy was investigated. The effect of the welding heat input (HI) on the penetration depth, microstructure, and mechanical properties of the weld metal was studied. A field emission scanning electron microscopy equipped with an electron backscatter diffraction (EBSD) detector was used to perform microstructural characterization. The results indicated that use of the HI value in the range of 48–80 J/mm could result in the formation of sound welds with full penetration depth at bead-on-plate configuration. EBSD studies revealed that when a low HI value was used to fabricate the double-welded sample, the {1 0 0} direction of austenite grains in the weld metal was parallel to the transvers and welding directions. Regarding the single-welded sample with a high HI value, the ?1 0 0? direction was strongly oriented at an angle between 40° to 50° with respect to the welding direction. Improvement in the hardness of both single-welded and double-welded samples was observed, as compared to the based metal. The results of tensile tests showed that tensile strength of the weldments was higher or almost similar to that of the base metal. Overall, the changes in the HI values had no significant effect on mechanical behavior of the weldments.
关键词： EBSD analysis,Microstructure,Laser welding,Mechanical behavior,Co-based alloy
更新于2025-09-23 15:21:01