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Recent progress in laser additive manufacturing of aluminum matrix composites
摘要： Laser additive manufacturing (LAM) can produce high-performance and near net shape parts of aluminum matrix composite (AMC) with higher specific strength, better wear resistance and more outstanding physical properties than aluminum alloys, which are widely used in automotive and aerospace fields. This article covers emerging researches on particle-reinforced AMCs fabricated by LAM techniques. The current research status is reviewed from the perspectives of powder preparation, microstructure characterization and mechanical properties. The microstructure evolution of AMCs is discussed in depth and the formation mechanism of in situ phase is analyzed. In addition, different strengthening mechanisms of AMCs are studied in detail. The last part summarizes the merits and demerits of AMCs and proposes the existing problems and future research directions.
关键词： Laser additive manufacturing,Mechanical properties,Microstructure,Aluminum matrix composites,Strengthening mechanisms
更新于2025-09-23 15:19:57
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FIB-SEM Investigation of Laser-Induced Periodic Surface Structures and Conical Surface Microstructures on D16T (AA2024-T4) Alloy
摘要： The use of aluminum alloy AA2024-T4 (Russian designation D16T) in applications requiring a high strength-to-weight ratio and fatigue resistance such as aircraft fuselage often demands the control and modification of surface properties. A promising route to surface conditioning of Al alloys is laser treatment. In the present work, the formation of ripples and conical microstructures under scanning with femtosecond (fs) laser pulses was investigated. Laser treatment was performed using 250 fs pulses of a 1033 nm Yb:YAG laser. The fluence of the pulses varied from 5 to 33 J/cm2. The scanning was repeated from 1 to 5 times for different areas of the sample. Treated areas were evaluated using focused ion beam (FIB)- scanning electron microscopy (SEM) imaging and sectioning, energy-dispersive X-ray (EDX) spectroscopy, atomic force microscopy (AFM), and confocal laser profilometry. The period of laser-induced periodic surface structures (LIPSS) and the average spacing of conical microstructures were deduced from SEM images by FFT. Unevenness of the treated areas was observed that is likely to have been caused by ablation debris. The structural and elemental changes of the material inside the conical microstructures was revealed by FIB-SEM and EDX. The underlying formation mechanisms of observed structures are discussed in this paper.
关键词： femtosecond laser,LIPSS,conical microstructures,aluminum alloy 2024
更新于2025-09-23 15:19:57
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Infrared radiation Induced attenuation of radiation sensitive optical fibers: influence of temperature and modal propagation
摘要： We investigate the X-ray (40 keV) and γ-ray (1.2 MeV) radiation responses of three different radiation sensitive Optical Fibers (OFs) up to 100 Gy(SiO2). In particular, we study the Radiation Induced Attenuation (RIA) in the Near Infrared domain (NIR) for single mode OFs doped with Phosphorus (P), Aluminum (Al) and Phosphorus/Cerium (PCe) in their cores at three temperatures up to 50 °C. RIA levels and kinetics strongly depend on the operating wavelength and fiber composition. For both P and PCe-doped fibers, the P1 defects are the main contributors to the RIA, with Ce-codoping inducing a decrease of radiation sensitivity. For the Al-doped fiber, no specific absorption bands can be discriminated in the NIR. Both X- and γ-rays lead to the same RIA levels and kinetics. The RIA spectral dependences on dose and temperature highlight the potential of the three investigated fibers for radiation detection and dosimetry. To better discuss the properties of point defects responsible for the NIR RIA, we analyze how the fundamental mode propagation influences the RIA spectra of each fiber type. By reasonably assuming that the core RIA exceeds largely the cladding RIA and by calculating the mode Confinement Factor (CF), the RIA spectra of the core material are reconstructed and the spectral characteristics of defects are discussed for each type of fibers.
关键词： Radiation Induced Attenuation,Aluminum,Optical fiber,Phosphorus,Cerium
更新于2025-09-23 15:19:57
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Boosting the Conversion Efficiency Over 20 % in MAPbI <sub/>3</sub> Perovskite Planar Solar Cells by Employing Solution-Processed Aluminum-Doped Nickel Oxide Hole Collector
摘要： Recently, nickel oxide (NiOx) thin films have been used as an efficient and robust hole transport layer (HTL) in inverted planar perovskite solar cells (IP-PSCs) to replace costly and unstable organic transport materials. However, the power conversion efficiency (PCE) of most IP-PSCs using NiOx HTLs is rather limited below 20 % due to insufficient electronic conductivity of the NiOx. In this work, solution-processed Al-doped NiOx (ANO) films are suggested as HTLs for low cost and stable IP-PSCs. The electrical conductivity of the NiOx film is significantly enhanced by the Al doping which effectively reduces the non-radiative recombination losses at the HTL(cid:150)perovskite interfaces and boosts hole extraction/transportation. The device with undoped NiOx shows the best PCE of 16.56 %, whereas ANO HTL (5 % doping) contributes to achieve a PCE of 20.84 %, which outperforms other CH3NH3PbI3 IP-PSCs with NiOx-based HTLs reported to date. Moreover, a reliability test (1728 h storage) shows that the performance stability is enhanced by approximately 11 % by employing ANO HTLs. This investigation into ANO HTLs provides a new guideline for the further development of highly efficient and reliable IP-PSCs using low cost and robust metal oxide HTLs.
关键词： Perovskite,Solar cells,Hole transport layer,Nickel oxide,Aluminum
更新于2025-09-23 15:19:57
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Size dependence of emission enhancement of Tris(8-hydroxyquinolinato) aluminum with plasmonic Al nanostructure
摘要： It is essential to understand which mechanism of localized surface plasmon (LSP) emission enhancement is to be utilized when combining plasmonic metal nanostructures with an emissive material to produce an optoelectronic device. Herein, we report on the size dependence and time-resolved dynamics of photoluminescence (PL) enhancement using three sizes of aluminum nanotriangles (Al NTs) on emission by tris(8-hydroxyquinolinato) aluminum (Alq3) for elucidating its enhancement mechanism. Al nanostructures were fabricated using a nanosphere lithography technique. Two-dimensionally aligned polystyrene (PSt) beads with different diameters were used as mask templates for obtaining the Al NTs. The absorption peaks red-shifted with increasing Al NT size, and hence, were attributed to the LSP resonance. From PL of Alq3 with and without Al NTs, 2–3 fold PL enhancements were observed among the samples with different Al NTs sizes. The significant shortening of the PL lifetime was observed only in Alq3/Al NTs using Ps500, indicating the effective coupling of LSP of Al NTs and the emission, which is also evidenced from the overlapping the PL peak and the LSP absorption. In contrast, the PL emission enhancement due to LSP coupling with the absorption process of Alq3 was dominant in Alq3/Al NTs using Ps200, suggested from the similarity of the PL decay curve with that of bare Alq3, and the excitation energy matching with LSP resonance. From these observation, we can distinguish the LSP coupling process (absorption or emission) from the presence or absence of lifetime enhancement in the time-resolved PL measurements, offering a guideline for designing the optical devices incorporating the metal nanostructures.
关键词： Aluminum nanostructure,Plasmon effect,Time-resolved measurement,Photoluminescence,Localized surface plasmon
更新于2025-09-23 15:19:57
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Hot cracking in autogenous welding of 6061-T6 aluminum alloy by rectangular pulsed Nd:YAG laser beam
摘要： Due to high hot crack susceptibility of Al-Mg-Si alloys, autogenous welding by rectangular pulsed laser beam has not been generally successful in the removal of cracks. In this research, the effect of pulsed Nd:YAG laser parameters and preheating on the creation of hot cracks in the 6061-T6 aluminum alloy was investigated. The sample that was fabricated by the laser parameters including 1 Hz, 0.12 mm/s, 10 ms, and without preheating exhibited the highest cooling rate and the smallest dendrite arm spacing but no hot crack was observed. The tensile test specimens of this sample fractured at a point far from the weld metal and a decrease in the precipitation of silicon and magnesium in the inter-dendritic space and the reduction of thermal stresses resulted in the elimination of hot cracks. However, according to macro-scale models for the creation of hot cracks, preheating decreased the tensile stresses in the BTR (brittle temperature range), but increasing the preheating temperature led to increasing rather than decreasing the hot crack length. In this case, the formation of hydrogen porosity, the segregation of silicon and magnesium, and the creation of low melting point compounds were the important parameters affecting the hot crack initiation and growth.
关键词： Laser welding,6061 aluminum alloy,Stress simulation,Solidification microstructure,Hot crack modeling,Rectangular pulse
更新于2025-09-23 15:19:57
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Influence of lowa??level laser therapy on implant stability in implants placed in fresh extraction sockets: A randomized clinical trial
摘要： Background: Low-level laser therapy (LLLT) has been suggested to improve primary stability at the early stages of osseointegration in animal models. However, there is still scarce evidence about its influence on implant stability in humans. Purpose: To assess the influence of LLLT on implant stability in implants placed in fresh extraction sockets. Material and methods: A randomized controlled trial was designed according to the SPIRIT guidelines and is reported following the CONSORT. Patients were randomly allocated according to control or LLLT groups. LLLT consisted in the application of GaAlAs laser (808 nm, avg. power density: 50 mW, circular spot diameter and area: 0.71 cm/0.4cm2) applied in six points in contact mode with peri-implant soft tissue (1.23 minutes in each point of application; dose per point 11 J) before bone perforation and after suturing. The total dose resulted in 66 J per application moment. This LLLT protocol was applied only in the dental implant placement session. Implant stability was by ISQ at implant placement (T0) and the abutment selection (Ta). Digital radiographs for T0 and Ta were used to assess the distance between the implant platform and alveolar bone crest, in millimeters. T-test and Shapiro-Wilk test were used to analyze data between groups using the implant as a unit of analysis. Results: Fifty implants were placed in 44 patients. The insertion torque ranged from 15 to 60 N.cm (mean 35.64 ± 13.34). Two implants of the LLLT and one of the control groups were lost to follow-up and one implant of the control group failed to osseointegrate (4.3%). ISQ at T0 ranged from 17 to 79 (mean 59.33 ± 13.05) and from 40 to 89 (mean 66.46 SD ± 11.56) at Ta. No differences were observed when comparing the groups with ISQ difference (P = .433) or radiographical peri-implant alterations (P = .261). Conclusions: LLLT did not influence implant stability in implants placed in fresh extraction sockets when assessed at healing abutment installation.
关键词： osseointegration,gallium aluminum arsenide lasers,dental implants,controlled clinical trial
更新于2025-09-23 15:19:57
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Size- and Surface-Dependent Photoresponses of Solution-Processed Aluminum Nanoparticles
摘要： Plasmonic aluminum nanoparticles have emerged as an exciting new materials platform due to the high natural abundance of aluminum, their ability to be synthesized in the solution phase, and the potential of these materials to be used for photocatalysis and sensing. However, the photothermal properties of solution-processed aluminum nanoparticles, in particular, how phonon energy transfer depends on the particle size and surface properties, are critical for practical applications and are currently unexplored. Here we use transient absorption spectroscopy, in combination with simulations of phonon and thermal energy dissipation, to investigate the photoresponses of aluminum nanoparticles of various diameters (54, 85, 121, and 144 nm) suspended in 2-propanol. Fast thermal-transfer rates to the solvent (170?280 ps) are observed for particles of all sizes and are facilitated by native oxide coverage, as veri?ed by a two-interface thermal energy-transfer model. Size-dependent phonon “breathing”/vibrational modes are also observed as oscillations in the total cross-section. We ?nd that both the oscillation frequency and the damping rate increase as the diameter of the particles decreases. On the basis of the results of ?nite element calculations, we attribute the damping strength and oscillation period observed to a combination of the noncrystalline nature of the native oxide shell and the presence of surface-bound ligands, both of which increase the vibrational mode damping rates relative to bare Al and Al particles with a bare crystalline oxide shell. These insights should guide future work on controlling energy transfer through the use of size and surface tuning in sustainable aluminum nanomaterial systems for applications in catalysis and sensing.
关键词： aluminum,phonons,surface effects,transient absorption,heat transfer,localized surface plasmon resonances
更新于2025-09-23 15:19:57
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Atomic Layer Deposition of Al <sub/>2</sub> O <sub/>3</sub> Using Aluminum Tri-Isopropoxide (ATIP): A Combined Experimental and Theoretical Study
摘要： The aluminum precursor plays a crucial role in the Al2O3 ALD process. Up to date, trimethyl aluminum (TMA) is one of the most widely used precursors in experimental and theoretical studies. However, its application at industrial scale can pose safety risks since it is pyrophoric and extremely reactive with water. Aluminum alkoxides offer a promising alternative, but have received far less attention. A combined theoretical and experimental investigation is carried out on the Al2O3 ALD process using aluminum triisopropoxide (ATIP) as a prototypical example of Al-alkoxide precursors. The experimental results pointed out that the thermal ALD process using ATIP and water has a maximal growth per cycle (GPC) of 1.8 ?/cycle at temperatures of 150°C to 175°C. Based on the in-situ mass spectrometry analysis and DFT calculations, the formation of the alumina film mainly occurs during the water pulse by ligand exchange reactions between water and adsorbed precursors, while during the ATIP pulse only adsorption of ATIP and/or its dissociation occur. Design of heteroleptic precursors containing alkoxide group as basic ligand is challenging, but greatly promising for future industrial scale Al2O3 ALD.
关键词： Al2O3,DFT calculations,Atomic Layer Deposition,Aluminum Triisopropoxide,Ligand Exchange Reactions
更新于2025-09-23 15:19:57
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Electrical, Structural, Optical, and Adhesive Characteristics of Aluminum-Doped Tin Oxide Thin Films for Transparent Flexible Thin-Film Transistor Applications
摘要： The properties of Al-doped SnOx films deposited via reactive co-sputtering were examined in terms of their potential applications for the fabrication of transparent and flexible electronic devices. Al 2.2-atom %-doped SnOx thin-film transistors (TFTs) exhibit improved semiconductor characteristics compared to non-doped films, with a lower sub-threshold swing of ~0.68 Vdec?1, increased on/off current ratio of ~8 × 107, threshold voltage (Vth) near 0 V, and markedly reduced (by 81%) Vth instability in air, attributable to the decrease in oxygen vacancy defects induced by the strong oxidizing potential of Al. Al-doped SnOx films maintain amorphous crystallinity, an optical transmittance of ~97%, and an adhesive strength (to a plastic substrate) of over 0.7 kgf/mm; such films are thus promising semiconductor candidates for fabrication of transparent flexible TFTs.
关键词： tin oxide,thin-film transistor,aluminum doping,adhesive property,oxide semiconductor
更新于2025-09-19 17:15:36