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Surface structural alteration of multi-walled carbon nanotubes decorated by nickel nanoparticles based on laser ablation/chemical reduction methods to enhance hydrogen storage properties
摘要： The catalytic effect of nickel is addressed to decorate the multi-walled carbon nanotubes for the purpose of hydrogen storage. The hydrogen sorption/desorption are investigated using the volumetric technique. Nickel nanoparticles are distributed on the surface of nanotubes using the laser ablation/chemical reduction treatments. The hydrogen uptake is elevated at higher nickel population up to a certain value and then experiences a significant drop for larger nickel content. The laser treatment is accompanied by the induced pores around nanotubes. This gives rise to the creation of the larger pores at higher laser doses leading to decrease the hydrogen trapping. Despite the pore size distribution strongly alters during both synthesis methods, however the abundance of small pore size in laser treatments is relatively higher than the that of the other technique. In comparison, the laser ablation demonstrates a relatively smaller desorption temperature against chemical one, mainly owing to the formation of larger pore size/volume. Generally, the hydrogen trapping efficiently takes place in the laser treated samples against chemical reduction method. The highest value of hydrogen storage ~1% (0.6% weight) is corresponding to 12.3% (13% weight) of nickel loading via the laser ablation (chemical reduction).
关键词： Hydrogen uptake,Nickel nanoparticles,Laser ablation,Chemical reduction,Pore size
更新于2025-09-23 15:22:29
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Enhanced visible-light-photoconversion efficiency of TiO2 nanotubes decorated by pulsed laser deposited CoNi nanoparticles
摘要： The pulsed laser deposition (PLD) technique has been used to decorate TiO2 nanotubes (NTs) with cobalt-nickel (CoNi) nanoparticles (NPs). The TiO2 NTs were produced beforehand through the controlled anodic oxidation of titanium substrates. The effect of the nature of the PLD background gas (Vacuum, O2 and He) on the microstructure, composition and chemical bondings of the CoNi-NPs deposited onto the TiO2-NTs has been investigated. We found that the PLD CoNi-NPs have a core/shell (oxide/metal) structure when deposited under vacuum, while they are fully oxidized when deposited under O2. On the other hand, by varying the CoNi-NPs loading of the TiO2-NTs (through the increase of the number of laser ablation pulses (NLP)), we have systematically studied their photocatalytic effect by means of cyclic-voltammetry (CV) measurements under both AM1.5 simulated solar light and filtered visible light. We show that depositing CoNi-NPs on the substrate under vacuum and He increases the photo-electrochemical conversion effectiveness (PCE) by 600% (at NLP = 10,000) in the visible light domain, while their overall PCE degrades with NLP under solar illumination. In contrast, the fully oxidized CoNi-NPs (deposited under O2) are found to be the most effective catalyst under sunlight with an overall increase of more than 50% of the PCE at the optimum loading around NLP ~1000. Such catalytic enhancement is believed to result from both an enhanced light absorption by CoO (of which bandgap is of ~2.4 eV) and the formation of a heterojunction between NiO/CoO nanoparticles and TiO2 nanotubes.
关键词： TiO2 nanotubes,Pulsed laser deposition,Cobalt/nickel nanoparticles,Photo-electrochemistry,Water-splitting
更新于2025-09-19 17:13:59
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Metal-Assisted Silicon Chemical Etching Using Self Assembled Sacrificial Nickel Nanoparticles Template for Anti-Reflection Layers in Photovoltaic and Light-Trapping Devices
摘要： Thin film de-wetting is a simple patterning approach that provides a straight forward method for fabricating silicon structures using metal-assisted chemical etching (MacEtch). Currently, this has been mainly demonstrated with gold (Au) or silver (Ag) catalyst for MacEtch and to accomplish this, an extra Au or Ag nanoparticles lift-off step is required. The uncertain success with the lift-off process is potentially a major hindrance to achieve low-cost, large-scale and uniform Si nanostructures. In this work, we report on the use of nickel (Ni) as an alternative sacrificial metal for the de-wetting process. The de-wetting phenomenon of Ni on silicon dioxide is investigated to show that controllable sizes and density are achievable for this material system. A physical model to describe the relationship among Ni film thickness, particle interspacing and density is proposed. Using the Ni nanoparticles as a starting mask template, an improved approach for the large scale fabrication of silicon nanowires without the use of lithography methods is demonstrated. This not only eliminates problems associated with lift-off but also allows for scaling up of such fabrication using the proposed self-assembly approach, which holds great potential in furthering the versatility of the MacEtch technique in anti-reflection surfaces and light-trapping devices applications.
关键词： MacEtch,Nickel nanoparticles,Silicon,MACE,De-wetting,Metal-assisted chemical etching
更新于2025-09-19 17:13:59
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Ni-NPs doped PVA: An efficient saturable absorber for generation multiwavelength Q-switched fiber laser system near 1.5?μm
摘要： We report on the use of Nickel nanoparticles (Ni-NPs) as saturable absorber (SA) to generate Q-switched fiber laser pulses in C-band. The Ni-NPs were incorporated in polyvinyl alcohol (PVA) to produce thin film-based saturable absorber (SA) and integrated into an erbium-doped fiber laser (EDFL) ring cavity to generate passively Q-switching. The Ni-doped PVA SA reveals modulation depth of 15% and a saturation intensity of 200 MW/cm2. Lasing in CW region begins at 77 mW pump power, whereas stable self-starting Q-switching with a central wavelength of 1563.1 nm begins at 85 mW. By fine adjustment of the laser diode pump power up to 236.4 mW dual-, and triple- lasing lines have been observed at 1563.1, 1563.3 and 1563.4 with side mode suppression ratio (SMSR) of more than 49 dB. The proposed laser is useful for generating pulse laser with a minimum pulse width of 1.5 μs and a maximum repetition rate of 56.79 kHz with a pulse energy of about 4.33 nJ at the maximum pump power of 275 mW. The stability of the pulse is verified from the radio-frequency (RF) spectrum with a measured signal-to-noise ratio (SNR) of 44 dB. The ability of Ni-PVA as an effective SA may lead to further development of pulsed fiber laser in the field of photonics.
关键词： Nickel Nanoparticles,Passive Q-switching,Multiwavelength Laser
更新于2025-09-16 10:30:52
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Nickel nanoparticles‐based saturable absorber: Toward compact multiwavelength Yb‐doped fiber pulsed lasers near 1 μm region
摘要： We experimentally demonstrate a compact pulsed dual-wavelength Ytterbium-doped fiber laser (YDF) based on Nickel nanoparticles (Ni-NPs) as a Q-switcher and optical stabilizer. By integrating the Ni-NPs saturable absorber (SA) in the cavity, and adjust the 975 nm diode pump power to 185 mW, a self-starting passively Q-switched was generated at a central wavelength of 1038.5 nm. By exploiting the extra high nonlinearity of Ni-NPs, the homogenous gain broadening of the YDF oscillator can be suppressed. Consequently, at a pump power of 195 mW, a stable dual-wavelength passively Q-switching laser has been generated at room temperature without any intracavity spectral filters or modulation elements. As increases the pump power up to the maximum value of 288 mW, the Ytterbium-doped fiber laser observed that the smallest pulse width, the maximum repetition rate, and the maximum pulse energy of 1.44 μs, 100.1 kHz, and 4.45 nJ, respectively. The Ni-NPs SA proof its potential in generating multi-wavelength pulsed laser in the 1 μm region for different photonic applications.
关键词： Q-switching,fiber laser,multiwavelength,nickel nanoparticles
更新于2025-09-11 14:15:04