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•The femtosecond laser irradiated silicon structures consist of the amorphous layer, dislocation layer and unaffected layer.•The formation of the high-density defect layer is ...attributed to the laser-induced thermal effect and stress.•Dislocations dominate the micro-deformation of the silicon structure and affect its nano-hardness.
As a pillar material of semiconductors, single-crystal silicon (Si) has attracted much attention due to its excellent electronic properties. Meanwhile, femtosecond laser processing as a convenient fabrication method for miniaturized structures provides an effective way to improve the performance of Si-based devices. However, the final-state analysis of femtosecond laser-induced Si micro-nano structures remains to be explored. In this study, the evolution of the micro-nano structures and the variation of surface and subsurface damage with pulse number were studied. Based on the atomic structure, the amorphous layer, dislocation layer, and unaffected layer were found. The amorphous layer resulted from the re-solidification of melted materials. The dislocation layer consisted of dislocations and lattice distortion. The unaffected layer retained the initial lattice structure and was not affected by laser irradiation. The high temperature and stress induced by multiple pulses led to the stacking faults and nano-twins in the subsurface layer. The evolution of the Si structure was essentially a transition process from a dislocation layer to a high-density defect layer and a transition process from nanotips to laser-induced periodic surface structures. During this process, dislocations dominated the femtosecond laser-induced microstructural deformation, affecting the nano-hardness of the irradiated surface. As a result, the nano-hardness of Si structures fabricated using femtosecond laser processing was maximally enhanced by 9.54%. This work provides new information about ultrafast laser-induced surface and subsurface damage, which is significant for the efficient and high-precision fabrication of Si-based functional micro-nano devices.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Femtosecond (fs) laser processing has received great attention for preparing novel micro-nano structures and functional materials. However, the induction mechanism of the micro-nano structures ...induced by fs lasers still needs to be explored. In this work, the laser-induced periodic surface structure (LIPSS) of monocrystalline silicon (Si) under fs laser irradiation is investigated. Three different layers named amorphous silicon (a-Si) layer, transition layer, and unaffected Si layer are observed after laser irradiation. The a-Si layer on the surface is generated by the resolidification of melting materials. The unaffected Si layer is not affected by laser irradiation and maintains the initial atomic structure. The transition layer consisting of a-Si and unaffected Si layers was observed under the irradiated subsurface. The phase transition mechanism of Si irradiated by fs laser is “amorphous transition”, with the absence of other crystal structures. A numerical model is established to describe the fs laser-Si interaction to characterize the electronic (lattice) dynamics of the LIPSS formation. The obtained results contribute to the understanding of fs laser processing of Si at the atomic scale as well as broaden the application prospects of fs laser for treating other semiconductor materials.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The heat transfer and solidification characteristics significantly affect the solidified microstructure of direct laser deposited coatings. In this work, a Ti-based coating was prepared on the Ti811 ...alloy by coaxial laser cladding to reveal the in-situ synthesis mechanism of the reinforcing phase and enhance its mechanical properties. The heat transfer evolution and solidification characteristics of the molten pool were investigated by numerical simulations and experiments. The phase composition, microstructure, interface characteristics, nano-hardness, and tribological properties of the deposited coating were studied. The results showed that the sufficient temperature of the molten pool ensured the formation of a deposited coating. The Marangoni convection of the molten pool facilitated the powder particles melting process as well as the uniformity of the reinforcing phase distribution. In addition, the temperature gradient and solidification rate at the upper of the solidified interface increased 2.27 and 29 times, respectively, compared to those at the bottom of the solidified interface. Thermodynamic and simulation results determined the precipitation sequence and mechanism of the phases. Due to the solid solution strengthening, dispersion strengthening effects, and robust interfacial bonding between phases, the nano-hardness of the deposited coating was 2.5 times higher than the substrate. Compared to the Ti811 alloy, the friction coefficient of the coating was reduced by around 30%. The tribological properties of the deposited coating dramatically improved, and the wear mechanism was mainly abrasive wear. This work theoretically and experimentally revealed the primary mechanism of in-situ enhancement to protect titanium alloys.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Aqueous zinc-ion batteries provide a most promising alternative to the existing lithium-ion batteries due to their high theoretical capacity, intrinsic safety, and low cost. However, commercializing ...aqueous zinc-ion batteries suffer from dendritic growth and side reactions on the surface of metallic zinc, resulting in poor reversibility. To overcome this critical challenge, here, we report a one-step ultrafast laser processing method for fabricating three-dimensional micro-/nanostructures on zinc anodes to optimize zinc nucleation and deposition processes. It is demonstrated that the three-dimensional micro-/nanostructure with increased specific surface area significantly reduces nucleation overpotential, as well as preferentially absorbs zinc ions to prevent dendritic protuberances and corrosion. As a result, the presence of three-dimensional micro-/nanostructures on the zinc metal delivers stable zinc plating/stripping beyond 2500 h (2 mA cm
-2
/1 mAh cm
-2
) in symmetric cells, a high Coulombic efficiency (99.71%) in half cells, and moreover an improved capacity retention (71.8%) is also observed in full cells. Equally intriguingly, the pouch cell with three-dimensional micro-/nanostructures can operate across various bending states without severely compromising performance. This work provides an effective strategy to construct ultrafine and high-precision three-dimensional micro-/nanostructures achieving high-performance zinc metal anodes and is expected to be of immediate benefit to other metal-based electrodes.
K403 alloy is promising in aero-engine and gas turbine components due to its outstanding mechanical properties. Here, in order to investigate the manufacturability, K403 coating was prepared on ...casted K403 substrate by laser melting deposition (LMD). The microstructure, microhardness, and wear performance of the coatings were studied. The results showed that the coating mainly consists of Ni3 (Al, Ti), Co3Ti and Cr3Mo. The microstructure of the coating is closely dependent on laser power. Precipitates were formed in the coating due to these high melting point elements. The highest microhardness of K403 superalloy coating is 455 HV0.2, which is 40% higher than that of casted K403 substrate. K403 superalloy coating also showed a better wear resistance than casted K403 substrate. The wear rate and friction coefficient of the K403 coating are only 41% and 70% of those of the casted K403, respectively. Furthermore, the formation of crack was discussed. We envision direct laser melting deposition of K403 superalloy can be an effective way to repair and enhance tribological performance of K403 superalloy components.
•K403 superalloy coatings are successfully fabricated by laser melting deposition.•As the laser power increases, the microstructure gradually becomes coarser and the growth direction is more regular.•Flocculent precipitates Cr3Mo and granular precipitates formed by W, Mo and Ti are produced along grain boundaries.•Compared with cast K403 superalloy substrate, K403 superalloy coating has better wear resistance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Inconel718 and nickel-plated carbon nanotubes composite inconel718 alloy coatings were prepared on 304 stainless steel by laser melting deposition.•The effect of laser power on the structure and ...hardness of Inconel 718 coating was studied.•Adding carbon nanotubes to Inconel 718 coatings reduces cracks, friction wear and electrochemical corrosion resistance decreased.
Nickel-plated carbon nanotubes composite inconel718 alloy coatings were prepared on 304 stainless steel by laser melting deposition. Its properties of microstructure, wear resistance and corrosion resistance were studied. In the inconel718 coating, the phases are γ-(Ni, Fe), γ′-Ni (Al, Ti) and Fe3Ni2. Compared with the coating without nickel-plated carbon nanotubes, the new phases are C, (Fe, C), C70 and Fe5C2, the grain structure is more uniform, the number of cracks is less and the length of cracks is shorter, the hardness is reduced by 21%, the self-corrosion potential is decreased by 4.4%, the corrosion current density is increased by 47%, the polarization resistance is decreased by 44%, the friction coefficient increases by 18% and the mass wear increases by 83%.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Building better nuclear fusion equipment with reduced cost is important for a sustainable society. In this study, pure tungsten is deposited on different steel substrates by directed energy ...deposition (DED). Specifically, the deposited layers with graded tungsten content by low and high laser scanning speed are fabricated. In addition, the processing parameters were optimized by analyzing the microstructure, phases and defects. Results show that the 9-layer sample (3000 W @ 3000 mm/min) exhibits a better thermal performance, which the thermal conductivity is about 73.75 W/(m·K) at room temperature and 147.45 W/(m·K) at 900 °C, respectively. Finally, the surface of the manufactured thick deposited layer by high-low combined laser scanning speed can reach a high tungsten content of up to 99.78 wt%. It is believed that the additive manufacturing of pure tungsten by DED can combine the advantages of tungsten and steel substrates, and simplify the manufacturing process of thermo-nuclear fusion devices.
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•The deposited layers with graded tungsten content by DED were fabricated.•The defects in DED of pure tungsten and its further improvement were studied.•The microstructural evolution mechanism for DED of pure tungsten was proposed.•A 4.4 mm thick deposition with 99.78 wt% tungsten at top surface was prepared.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
To overcome the unworkability of hot work molds in conventional manufacturing, laser additive manufacturing (AM) is widely adopted to print molds/dies with complex internal structures. However, in ...the AM process, some hot work steels easily crack (e.g., H11 and H13 tool steel) or exhibit dissatisfactory wear resistance (e.g., MS1 maraging steel). To tackle this issue, toughened functionally graded metal matrix/ceramic composite materials can be fabricated on existing molds by laser directed energy deposition (L-DED). Contrary to previous studies that clad Co on WC to avoid the decomposition of ceramic, in this work, we innovatively utilized a type of WC-12Co powder with a substructure to accelerate its decomposition and improve the toughness of composites. It was found that the unmelted tens-micrometer-magnitude WC-12Co powder and in situ synthesized nano WC coexist in the laser-deposited H13 steel/WC-12Co composites to act as the reinforcement phase. Particularly, all the brittle phases (WC and FexWxC) are wrapped by soft γ phases, alleviating the coefficient of thermal expansion (CET) mismatch between materials and the residual stress generated by laser AM. Consequently, defect-free deposits with varied WC contents are manufactured by L-DED and exhibit high hardness and superior wear resistance at both room and elevated temperatures due to the second phase and grain refinement strengthening mechanisms. These findings provide a disparate metal matrix composite design route for laser additive manufacturing to improve the toughness of metal matrix/ceramic composite materials and obtain exceptional performance.
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•The micro/nano strengthening mechanism of WC is studied in Fe-based WC composite.•The Co-coated WC powder with a large specific surface area promotes the in situ synthesis of nano WC precipitates.•All the brittle strengthening phases are wrapped by the ductile austenite to avoid crack.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Traditional orthopedic metal implants, such as titanium (Ti), Ti alloys, and cobalt-chromium (Co-Cr) alloys, cannot be degraded in vivo. Fracture patients is must always suffer a second operation to ...remove the implants. Moreover, stress shielding, or stress protection occurs when traditional orthopedic metal implants are applied in fractures surgery. The mechanical shunt produced by traditional orthopedic metal implants can cause bone loss over time, resulting in decreased bone strength and delayed fracture healing. Biodegradable metals that ‘biocorrode’ are currently attracting significant interest in the orthopedics field due to their suitability as temporary implants. As one of the biodegradable metals, magnesium (Mg) and Mg alloys have gained interest in the field of medicine due to their low density, excellent biocompatibility, high bioresorbability, and proper mechanical properties. Additionally, Mg ions released from the metal implants can promote osteogenesis and angiogenesis during the degradation process in vivo, which is substantially better for orthopedic fixation than other bioinert metal materials. Therefore, this review focuses on the properties, fabrication, biological functions, and surface modification of Mg-based alloys as novel bioabsorbable biomaterials for orthopedic applications.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this work, a preplaced TaZr alloy powder layer (Ta:Zr = 7:3 in wt%) is coated on a Ti6Al4V substrate by laser-based directed energy deposition. Crack-free, smooth TaZr alloy coating is acquired, ...and the content of elements (Ta, Zr, Ti, Al, V) distributes in a gradient. In this coating, the bcc α-Ta grains with a rectangular shape and a size of 10–20 nm surrounded by the TiZr phase, the Al3Zr4 phase mainly gathers in grain boundary. The corrosion resistance of the coating and substrate is tested via electrochemical measurement and the coating exhibits a better resistance in 0.5 mol/L H2SO4 solution. The average microhardness of the coating is around 600 HV, which is ~1.7 times than that of the substrate. The wear test results show the mass loss of the coating is approximately 60 times lower than the substrate at room temperature. It is believed that this coating could shed light on not only the protection of Ti-based alloy, but also the Fe-based and Ni-based components with the functionally graded transition layers.
•The TaZr powder was coated on Ti6Al4V via laser directed energy deposition.•Microstructural features of the Ta alloy coating were investigated.•The Ta alloy coating exhibits excellent microhardness and corrosion resistance.•The wear resistance and corresponding mechanism of the coating was revealed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
