The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Ruimei Yuan - One of the best experts on this subject based on the ideXlab platform.
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Ablation resistance of hfb2 sic coating prepared by in situ reaction method for sic coated c c composites
Ceramics International, 2017Co-Authors: Peipei Wang, Hejun Li, Yulei Zhang, Ruimei YuanAbstract:Abstract To improve the Ablation resistance of SiC coating, HfB 2 -SiC coating was prepared on SiC-coated carbon/carbon (C/C) composites by in-situ reaction method. Owing to the penetration of coating powders, there is no clear boundary between SiC coating and HfB 2 -SiC coating. After oxyacetylene Ablation for 60 s at heat flux of 2400 kW/m 2 , the mass Ablation Rate and linear Ablation Rate of the coated C/C composites were only 0.147 mg/s and 0.267 µm/s, reduced by 21.8% and 60.0%, respectively, compared with SiC coated C/C composites. The good Ablation resistance was attributed to the formation of multiple Hf-Si-O glassy layer including SiO 2 , HfO 2 and HfSiO 4 .
E Audouard - One of the best experts on this subject based on the ideXlab platform.
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femtosecond laser volume Ablation Rate and threshold measurements by differential weighing
Optics Express, 2012Co-Authors: David Pietroy, Y Di Maio, B Moine, E Baubeau, E AudouardAbstract:Precise weight measurements of stainless steel, PZT and PMMA samples were performed after groove machining with femtosecond laser pulses (150 fs, 800 nm, 5 kHz) to determine volume Ablation Rates and Ablation threshold with good accuracy. Weighing clearly enables faster determination of such phenomenological parameters without any methodological issue compared to other methods. Comparisons of the three types of materials reveal similar monotonous trends depending on peak fluences from 0.2 to 15 J/cm2. The metallic target exhibits both the lowest volume Ablation Rate under the highest irradiation conditions with almost 400 µm3/pulse and the lowest Ablation threshold with 0.13 J/cm2. Ceramic PZT reaches 3.103 µm3/pulse with a threshold fluence of 0.26 J/cm2 while polymer PMMA attains 104 µm3/pulse for a 0.76 J/cm2 threshold. Pros and cons of this method are also deduced from complementary results obtained on microscopic and confocal characterizations.
Peipei Wang - One of the best experts on this subject based on the ideXlab platform.
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Ablation resistance of hfb2 sic coating prepared by in situ reaction method for sic coated c c composites
Ceramics International, 2017Co-Authors: Peipei Wang, Hejun Li, Yulei Zhang, Ruimei YuanAbstract:Abstract To improve the Ablation resistance of SiC coating, HfB 2 -SiC coating was prepared on SiC-coated carbon/carbon (C/C) composites by in-situ reaction method. Owing to the penetration of coating powders, there is no clear boundary between SiC coating and HfB 2 -SiC coating. After oxyacetylene Ablation for 60 s at heat flux of 2400 kW/m 2 , the mass Ablation Rate and linear Ablation Rate of the coated C/C composites were only 0.147 mg/s and 0.267 µm/s, reduced by 21.8% and 60.0%, respectively, compared with SiC coated C/C composites. The good Ablation resistance was attributed to the formation of multiple Hf-Si-O glassy layer including SiO 2 , HfO 2 and HfSiO 4 .
G. Robinson - One of the best experts on this subject based on the ideXlab platform.
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Femtosecond laser micro-structuring of aluminium under helium
Applied Surface Science, 2004Co-Authors: G. RobinsonAbstract:The interaction of 180fs, 775nm laser pulses with aluminium under a flowing stream of helium at ambient pressure have been used to study the material re-deposition, Ablation Rate and residual surface roughness. Threshold fluence Fth???0.4Jcm-2 and the volume Ablation Rate was measured to be 30
Mihai Stafe - One of the best experts on this subject based on the ideXlab platform.
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EXPERIMENTAL INVESTIGATION OF THE NANOSECOND LASER Ablation Rate OF ALUMINUM
2020Co-Authors: Mihai Stafe, I. Vladoiu, C. Neguþu, Ion M. PopescuAbstract:The dependence of the Ablation Rate of aluminum of the laser spot diameter and laser fluency is analysed, in the visible and infrared nanosecond-pulses irradiation regimes. Experimental results indicate that, for a constant flux of energy and large laser spots, the Ablation Rate decays linearly with increasing laser spots diameter reaching maximum values of 5.5 Pm/pulse for the visible radiation respectively, 0.35 Pm/pulse in the case of infrared laser pulses. This indicates that the infrared radiation is much less efficiently coupled to the metallic sample than the visible radiation. By decreasing the diameter of visible laser-spot below a threshold value (| 0.6 mm) a nonlinear increase of the Ablation Rate are observed. The decrease of the spot diameter leads to an increase of laser fluence. For the values of the fluence in the low and medium regimes, increasing the fluence of the infrared and visible laser waves gives rise to an increase of the Ablation Rate inversely proportional with the square-root of the fluence. Further increase of the visible laser fluence above a threshold value (| 60 J/cm 2 ) leads to a marked quadratic increase of the Ablation Rate. The transition from the asymptotic to the quadratic increase of the Ablation Rate with increasing laser fluence, and from the linear to the nonlinear increase with decreasing laser-spot diameter, are related to the transition from a normal vaporization regime to a phase explosion regime.
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Effect of laser fluence on the Ablation Rate of metals in the infrared, visible, and ultraviolet nanosecond pulses irradiation regime
International Congress on Applications of Lasers & Electro-Optics, 2020Co-Authors: Mihai Stafe, C. Negutu, I. Vladoiu, Ion M. PopescuAbstract:We performed experiments to investigate the dependence of the Ablation Rate of three metals (aluminium, titanium and copper) on the fluence of nanosecond laser pulses at 1064, 532 and 355 nm wavelength in atmospheric air. We assessed the Ablation Rate for values of the fluence in the range of 1-600 J/cm2 by changing the irradiated area at the target surface, while exchanging the harmonics modules of a Nd-YAG laser system to vary the wavelength. The data indicate that, at each wavelength, the Ablation Rate for the three metals studied here increases approximately logarithmically with the fluence. By analysing the logarithmic dependence of the Ablation Rate on fluence, we find three main characteristics that describe metal Ablation in nanosecond regime. First, the Ablation threshold fluence is directly related to the optical penetration depth, which depends on the irradiated material and wavelength. Second, the Ablation Rate decays with the optical penetration depth and thermal diffusivity of the material, the aluminium Ablation being the most efficient. Third, the Ablation Rate of metals increases with increasing laser wavelength. The increase of the Ablation Rate with wavelength is related to the superposition of two effects: the increase of plasma absorption with wavelength, which leads to an enhanced recoil pressure on the melted surface of the target, and the increase of the evaporation and melt ejection Rates due to the large recoil pressure.We performed experiments to investigate the dependence of the Ablation Rate of three metals (aluminium, titanium and copper) on the fluence of nanosecond laser pulses at 1064, 532 and 355 nm wavelength in atmospheric air. We assessed the Ablation Rate for values of the fluence in the range of 1-600 J/cm2 by changing the irradiated area at the target surface, while exchanging the harmonics modules of a Nd-YAG laser system to vary the wavelength. The data indicate that, at each wavelength, the Ablation Rate for the three metals studied here increases approximately logarithmically with the fluence. By analysing the logarithmic dependence of the Ablation Rate on fluence, we find three main characteristics that describe metal Ablation in nanosecond regime. First, the Ablation threshold fluence is directly related to the optical penetration depth, which depends on the irradiated material and wavelength. Second, the Ablation Rate decays with the optical penetration depth and thermal diffusivity of the material, ...
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Pulsed Laser Ablation of Solids
Romanian Reports in Physics, 2014Co-Authors: Mihai Stafe, Aurelian Marcu, Niculae N. PuscasAbstract:Here we give an overview on our main experimental and theoretical work on pulsed laser Ablation (PLA) on several targets: metals (Al, Ti, Fe and Cu) and dielectrics (Er 3+ :Ti:LiNbO 3). PLA is demonstRated to be effective when the laser fluence is larger than a threshold value which depends mainly on the optical properties of the material and wavelength. The experiments indicate that the Ablation Rate decreases approximately linearly with wavelength and with the inverse of beam diameter, whereas an increasing fluence leads to logarithmic increase of the Ablation Rate. Opto-dynamics and laser spectroscopy are used for analyzing the Ablation plasmas and the ablated structures in real-time. We further characterize theoretically the laser Ablation and present the photo-thermal model for Ablation with short pulses. We show that PLA in ns/ps regimes can be considered as a superposition of heating, melting, vaporization and melt ejection under the action of the plasma recoil pressure, the plasma shielding effect being also accounted for. The Ablation Rate is calculated numerically by solving through finite-differences method a heat-type equation in an iterative algorithm and indicates, like the experiments do, that the Ablation Rate is first constant during the first pulses and decreases strongly afterward with increasing pulse number.
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A spectroscopic and theoretical study of the laser Ablation Rate of Al
Advanced Topics in Optoelectronics Microelectronics and Nanotechnologies VI, 2012Co-Authors: Mihai Stafe, C. Negutu, Adrian N. Ducariu, Niculae N. PuscasAbstract:We investigated experimentally and theoretically the laser Ablation of Al by using nanosecond laser-pulses at 532 nm wavelength in atmospheric air. We analyzed experimentally the dependence of the Ablation Rate on the laser fluence and pulse number. The fluence was varied between 3 and 3000 J/cm2 by changing the laser-energy, while pulse number was varied between 4 and 60 in steps of 4. The optical microscopy data indicate that the Ablation Rate increases approximately linearly with the 1/3 power of the fluence. For high fluences (hundreds of J/cm2) the Ablation Rate is demonstRated to be very large (~2 micron/pulse) and approximately constant during 30 consecutive pulses and much smaller during the next pulses. The dependence of the Ablation Rate on pulse number was further addressed by spectrometric analysis of the Ablation-plasmas produced at high fluences. We found that the plasma temperature varies similarly to the Ablation Rate when increasing the pulse number. The Ablation Rate in the low fluence regime was addressed theoretically within the frame of a photo-thermal model which accounts for the material heating, melting and evaporation upon laser radiation. The theoretical and experimental results are in good agreement indicating the validity of the model for low laser fluences.
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Effect of pulse number on the Ablation Rate of metals in PLA multipulse regime
Advanced Topics in Optoelectronics Microelectronics and Nanotechnologies V, 2010Co-Authors: C. Negutu, Niculae N. Puscas, Mihai Stafe, I. Vladoiu, A. Rizea, Ion M. PopescuAbstract:The pulsed laser Ablation of aluminium, copper and titanium irradiated with 4.5 ns pulses at 355 nm, 532 nm and 1064 nm wavelengths is investigated in open air at normal atmospheric conditions. The effect of pulse number, which is varied in the range of 5 to 50, on Ablation Rate in these three wavelength regimes is determined. The results indicate a higher efficiency of the Ablation in VIS and UV regimes as compared to IR regime which is characterised by a very small optical absorbtivity. The Ablation Rate is demonstRated to be approximately constant when increasing the pulse number up to a certain value which strongly depends on the thermal properties of the material. Further increase of pulse number leads to a progressive decrease of Ablation Rate. The most pronounced decrease was obtained at 355 nm in aluminium where the Ablation Rate corresponding to the 50 th pulse is about 20% of the Ablation Rate corresponding to of first pulse. The decay of the Ablation Rate with the pulse number is attributed to the superposition of two phenomena: the enhanced attenuation of the laser beam in the plasma plume which is confined within the cRater, and the decay of the effective laser fluence at the target surface due to the gradual increment of the effective irradiated area with pulse number.
