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- 2018
- Carbon nanotubes
- Magnetic focused
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- Heat Trap
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Investigation of cut quality in fiber laser cutting of CFRP
摘要： Fiber laser cutting of CFRP sheets was investigated using a 2 kW multi-mode fiber laser, focusing on how the cut quality factors, such as kerf width, kerf depth, matrix evaporation width, matrix recession width, kerf taper angle, matrix damage zone, and cut surface morphology, change as laser power, laser scanning speed, and the number of laser passes are varied. By designing a systematic experiment on a large process window, several important parameters for kerf width, kerf depth, matrix evaporation width, and matrix recession width were identified, and using them, it was verified that the beam scanning speed is a dominant factor for minimizing thermal damages. Also, circular rings were observed in each carbon fiber at the cut surfaces, and it looked as if they were generated when each fiber was thermally fused in the radial direction. A larger number of laser passes was found to contribute to a smooth surface morphology, because of the formation of highly-fused surfaces, which prevents fiber delamination and pull-outs. Optimum process conditions were also identified by comparing various cut quality factors.
关键词： Fiber laser cutting,Optimal process conditions,Cut quality factors,Thermal damage,Carbon fiber reinforced plastic (CFRP)
更新于2025-11-28 14:24:20
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Butt welding-brazing of steel to aluminum by hybrid laser-CMT
摘要： A laser penetration welding-brazing combined with Cold Metal Transfer (CMT) arc, was proposed to improve weld shape and interfacial reaction inhomogeneity of 5052 aluminum alloy and Q235 low carbon steel with ER5356 welding wire in butt joint. The effects of wire feed speed, beam offset and welding speed on weld shape, interfacial microstructures and tensile strength of joints was studied. This method improved the undercut defect existed in butt laser welding-brazing, obtained well-formed joints and promoted the uniform distribution of the interface reaction. The interfacial intermetallic compounds (IMCs) layer consisted of Fe2Al5 and Fe4Al13 and the thicknesses were controlled to 3-5 μm. Microstructures of weld seam was composed of α-Al and Al3Mg2. The brittle IMCs layer thickened and then the tensile strength decreased with increasing the wire feed speed. The thickness of the IMCs layer decreased but weld shape became worse when the welding speed or the offset increased. The tensile strength increased first and then decreased. The highest tensile strength reached higher than 80 MPa and the joint fractured in IMCs layer along the interface.
关键词： intermetallic compound,Laser–CMT arc hybrid welding-brazing,dissimilar metals welding,low carbon steel,aluminum alloy
更新于2025-11-28 14:24:20
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Enhanced mechanical performance of fusion zone in laser beam welding joint of molybdenum alloy due to solid carburizing
摘要： It is unable to strengthen molybdenum (Mo) through solid-state phase transformation, while exploring the effect of carbon (C) on microstructures and properties of fusion zone (FZ) of laser beam welding (LBW) joints of Mo alloy with serious grain boundary embrittlement is significant. An analysis was made on changes of bonding strength of grain boundary and precipitates on the grain boundary surface in the FZ of Mo carburized welded joints, and the existing form and strengthening mechanism of carbon. At first, solid carburizing (SC) can achieve the goal of adding the C to welded joints and C mainly appeared as C atoms and Mo2C in Mo alloy. Afterwards, C could increase the grain boundary strength and the plasticity of grains in the FZ. Therefore, the compatibility of deformation at grain boundary and grain interior was improved. Finally, Mo2C distributing at the grain boundary can inhibit the crack propagation during the deformation. As a results, the tensile strength of carburized weld joints rose by 426% compared with that of uncarburized weld joints, meanwhile the above results provide a new idea for the method for strengthening the Mo fusion weld joints.
关键词： laser beam welding,grain boundary embrittlement,carbon,molybdenum
更新于2025-11-28 14:24:20
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Tunable Ytterbium-Doped Mode-locked Fiber Laser Based on Single-Walled Carbon Nanotubes
摘要： A tunable mode-locked ytterbium-doped fiber laser with a tuning range of 55 nm is demonstrated. Currently, this is the widest tuning range for all-normal dispersion (ANDi) ytterbium-doped mode-locked fiber laser based on new-material saturable absorber (SA). The combined effects of the single-walled carbon nanotubes (SWCNTs) saturable absorber and a reflective grating significantly improved laser performance: broad tuning range, superb stability and repeatability. The experimental results indicate that SWCNTs can be a brilliant saturable absorber in all-normal dispersion regime at 1 μm, with pulse width of 2.4 ps and optical spectral bandwidth of 1.6 nm across the full tuning range. The laser also shows that the optical spectrum can be tuned accurately and continuously, which gives possibility for various applications such as optical communications, spectroscopy, time-resolved measurement, etc.
关键词： optical tuning,mode locked,fiber laser,Ultrafast optics,carbon nanotubes
更新于2025-11-28 14:24:03
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Nanotube mode-locked, wavelength and pulsewidth tunable thulium fiber laser
摘要： Mode-locked oscillators with highly tunable output characteristics are desirable for a range of applications. Here, with a custom-made tunable filter, we demonstrate a carbon nanotube (CNT) mode-locked thulium fiber laser with widely tunable wavelength, spectral bandwidth, and pulse duration. The demonstrated laser’s wavelength tuning range reached 300 nm (from 1733 nm to 2033 nm), which is the widest-ever that was reported for rare-earth ion doped fiber oscillators in the near-infrared. At each wavelength, the pulse duration can be regulated by changing the filter’s bandwidth. For example, at ~1902 nm, the pulse duration can be adjusted from 0.9 ps to 6.4 ps (the corresponding output spectral bandwidth from 4.3 nm to 0.6 nm). Furthermore, we experimentally and numerically study the spectral evolution of the mode-locked laser in presence of a tunable filter, a topic that has not been thoroughly investigated for thulium-doped fiber lasers. The detailed dynamical change of the mode-locked spectra is presented and we observed gradual suppression of the Kelly sidebands as the filter’s bandwidth is reduced. Further, using the polarization-maintaiing (PM) cavity ensures that the laser is stable and the output laser’s polarization extinction ratio is measured to exceed 20 dB.
关键词： thulium fiber laser,spectral bandwidth,polarization-maintaiing cavity,Kelly sidebands,tunable wavelength,pulse duration,Mode-locked oscillators,carbon nanotube
更新于2025-11-28 14:23:57
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Characterization of a double Time-Of-Flight detector system for accurate velocity measurement in a storage ring using laser beams
摘要： The Isochronous Mass Spectrometry (IMS) is a powerful tool for mass measurements of exotic nuclei with half-lives as short as several tens of micro-seconds in storage rings. In order to improve the mass resolving power while preserving the acceptance of the storage ring, the IMS with two Time-Of-Flight (TOF) detectors has been implemented at the storage ring CSRe in Lanzhou, China. Additional velocity information beside the revolution time in the ring can be obtained for each of the stored ions by using the double TOF detector system. In this paper, we introduced a new method of using a 658 nm laser range finder and a short-pulsed ultra-violet laser to directly measure the distance and time delay difference between the two TOF detectors which were installed inside the 10?11 mbar vacuum chambers. The results showed that the distance between the two ultra-thin carbon foils of the two TOF detectors was ranging from 18032.5 mm to 18035.0 mm over a measurable area of 20×20 mm2. Given the measured distance, the time delay difference which comes with signal cable length difference between the two TOF detectors was measured to be ??????????????1?2 = 99(26) ps. The new method has enabled us to use the speed of light in vacuum to calibrate the velocity of stored ions in the ring. The velocity resolution of the current double TOF detector system at CSRe was deduced to be ??(??)∕?? = 4.4 × 10?4 for laser light, mainly limited by the time resolution of the TOF detectors.
关键词： Ultra-high vacuum,Ultra-thin carbon foil,TOF detectors,Velocity measurement,Laser range-finder,ps-pulsed UV laser
更新于2025-11-25 10:30:42
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Rapidly self-heating shape memory polyurethane nanocomposite with boron-doped single-walled carbon nanotubes using near-infrared laser
摘要： In this study, boron-doped single-walled carbon nanotubes (SWCNTs) were synthesized by high-temperature heat treatment (1300 °C) with a boric acid precursor and SWCNTs instead of the conventional chemical doping process. Then, these boron-doped single-walled carbon nanotubes (B-SWCNTs) were added to polyurethane to prepare polyurethane nanocomposites having excellent thermal and mechanical properties. Changes in properties that occurred due to structural changes inside the composite were investigated as the added amount of nanofiller was increased. In particular, a near-infrared (NIR) laser (808 nm) was directly irradiated on the nanocomposite film to induce photothermal properties on the surface of the B-SWCNTs. In the case of the PU nanocomposite film with a filler content of 3 wt%, a self-heating film material that rapidly heated to 250 °C within 10 s was developed. The newly developed material can be applied to electronic devices and products as a heat-generating coating material, de-icing of airplane, a heat sink, for bio-sensing, etc., using a moulding process.
关键词： boron-doping,photothermal,thermoelectrics,carbon nanotube,polyurethane
更新于2025-11-25 10:30:42
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A carbon nanotube-iron (III) oxide nanocomposite as a cathode in dye-sensitized solar cells: Computational modeling and electrochemical investigations
摘要： Here is the evaluating result on the applicability of the multi-walled carbon nanotube (MWCNT) and a-iron (III) oxide (a-Fe2O3) nanocomposite as a cathode material in dye-sensitized solar cells (DSCs). The morphology and the structure of the MWCNT/a-Fe2O3 nanocomposite have characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray elemental mapping analysis. Moreover, the electrochemical performance of the nanocomposite has studied toward the activity of Iˉ/I3ˉ redox couple which represents high current density, low peak-to-peak separation, low charge-transfer resistance, and almost 100% stable response signal. Furthermore, the computational modeling employing the molecular mechanics (MM) and the restricted-Hartree Fock/semiempirical parameterization (RHF/PM6) methods reveals that the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), and the HOMO-LUMO energy gap of the modeled nanocomposite are as (cid:1)6.88, (cid:1)3.62, and 3.26 eV, respectively. These properties match with the electronic-level domino of the DSC structure. Finally, the DSC device has fabricated using N719-sensitized TiO2 photoanode and MWCNT/a-Fe2O3 counter electrode, presenting the open-circuit potential, the short-circuit current density, and the power-conversion ef?ciency of 0.7 V, 20.37 mA cmˉ2, and 6.0%, respectively. This study successfully approves the potential of the nanocomposite as a cathode material in iodine-based dye-sensitized solar cells.
关键词： Dye-sensitized solar cell,Nanocomposite,Carbon nanotube,Molecular mechanics,RHF/PM6,Iron (III) oxide
更新于2025-11-21 11:18:25
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Keyhole cutting of carbon fiber reinforced polymer using a long-duration nanosecond pulse laser
摘要： The machining performance of a high-energy nanosecond pulse laser with a near-infrared wavelength is investigated for carbon fiber-reinforced polymer (CFRP) with two different fiber arrangements. This research work demonstrates for the first time that a keyhole mode cutting can be achieved for CFRP materials using a high-energy nanosecond pulse laser of a Long Pulse mode (120 ns). Specifically, it is shown that the short-duration Q-Switch mode (8 ns) results in ineffective material removal for CFRP, despite much higher peak laser power intensity than the Long Pulse mode. In Long Pulse mode, multi-pass straight line and contour cutting experiments are further performed to investigate the effect of laser processing parameters and resultant machined surface integrity. Plasma absorption effects using both pulse modes are discussed. The results show that a 2.2 mm thick cross-ply CFRP panel can be cut through using as few as 6 laser passes, and a high-quality machined surface can be produced with a limited heat-affected zone and minimal fiber pull-out using Argon assist gas. The successful outcomes from this work provide the key to enable efficient CFRP laser machining using high-energy nanosecond pulse lasers, and offer insight into the unique energy absorption mechanisms for CFRP laser machining.
关键词： Laser cutting,Keyhole,Long pulse,Nanosecond pulse laser,Carbon fiber reinforced polymer
更新于2025-11-21 11:08:12
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Green Preparation of Fluorescent Carbon Quantum Dots from Cyanobacteria for Biological Imaging
摘要： Biomass-based carbon quantum dots (CQDs) have become a significant carbon materials by their virtues of being cost-effective, easy to fabricate and low in environmental impact. However, there are few reports regarding using cyanobacteria as a carbon source for the synthesis of fluorescent CQDs. In this study, the low-cost biomass of cyanobacteria was used as the sole carbon source to synthesize water-soluble CQDs by a simple hydrothermal method. The synthesized CQDs were mono-dispersed with an average diameter of 2.48 nm and exhibited excitation-dependent emission performance with a quantum yield of 9.24%. Furthermore, the cyanobacteria-derived CQDs had almost no photobleaching under long-time UV irradiation, and exhibited high photostability in the solutions with a wide range of pH and salinity. Since no chemical reagent was involved in the synthesis of CQDs, the as-prepared CQDs were confirmed to have low cytotoxicity for PC12 cells even at a high concentration. Additionally, the CQDs could be efficiently taken up by cells to illuminate the whole cell and create a clear distinction between cytoplasm and nucleus. The combined advantages of green synthesis, cost-effectiveness and low cytotoxicity make synthesized CQDs a significant carbon source and broaden the application of cyanobacteria and provide an economical route to fabricate CQDs on a large scale.
关键词： bioimaging,cyanobacteria,carbon quantum dots,hydrothermal method
更新于2025-11-21 11:08:12