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Xiaoyan Zeng - One of the best experts on this subject based on the ideXlab platform.
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effect of parameters on picosecond Laser ablation of cr12mov cold work mold steel
Applied Physics A, 2018Co-Authors: Peng Liu, Fei Zhang, Jun Duan, Xizhao Wang, Xiaoyan ZengAbstract:Cr12MoV cold work mold steel, which is a difficult-to-machining material, is widely used in the mold and dye industry. A picosecond pulse Nd:YVO4 Laser at 1064 nm was used to conduct the study. Effects of operation parameters (i.e., Laser Fluence, scanning speed, hatched space and number of scans) were studied on ablation depth and quality of Cr12MoV at the repetition rate of 20 MHz. The experimental results reveal that all the four parameters affect the ablation depth significantly. While the surface roughness depends mainly on Laser Fluence or scanning speed and secondarily on hatched space or number of scans. For Laser Fluence and scanning speed, three distinct surface morphologies were observed experiencing transition from flat (Ra 2.40 μm). However, for hatched space and number of scan, there is a small bumpy and rough zone or even no rough zone. Mechanisms including heat accumulation, plasma shielding and combustion reaction effects are proposed based on the ablation depth and processing morphology. By appropriate management of the Laser Fluence and scanning speed, high ablation depth with low surface roughness can be obtained at small hatched space and high number of scans.
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study on picosecond pulse Laser ablation of cr12mov cold work mold steel
Materials & Design, 2016Co-Authors: Peng Liu, Jun Duan, Xiaoyan Zeng, Leimin Deng, Xizhao WangAbstract:Abstract Cr12MoV has wide applications in the molds and dies industry. However, it is also a hard-to-machining material due to its high mechanical strength and hardness. Area ablation of Cr12MoV cold-work mold steel was carried out using a picosecond (ps) pulse Nd:YVO4 Laser. The effects of Laser Fluence and wavelength on the ablation rate and machining quality were investigated with wavelengths of 1064 nm, 532 nm and 355 nm. The experimental results indicate a logarithmic increase of the ablation rate to a maximum value of ~ 41 nm/pulse with the increase of Laser Fluence using the wavelengths of 1064 nm and 355 nm. For the wavelength of 532 nm, an ablation rate of ~ 33 nm/pulse is achieved at low Laser Fluence of 8.28 J/cm2, then increases logarithmically into about 54 nm/pulse at 25.10 J/cm2, and then decreases steeply into almost zero as the Laser Fluence increases above 25.10 J/cm2. For the three Laser wavelengths, different pore sizes were observed in the Laser ablation region. The surface roughness increases exponentially with the increase of the Laser Fluence. The inFluence mechanisms of Laser Fluence and wavelength on the Laser ablation rate and machining quality were systematically analyzed and discussed in this paper.
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tailoring the surface wettability of polyimide by uv Laser direct texturing in different gas atmospheres
Materials & Design, 2016Co-Authors: Jianguo Liu, Lianbo Guo, Xiaoyan ZengAbstract:Abstract Surface wettability modification of polyimide film was studied by UV Laser direct texturing (UVLDT). The inFluences of Laser Fluence on surface microstructure, chemical composition and wettability were explored in air, O2, and N2 atmospheres, respectively. Scanning electron microscopy (SEM), surface probe profilometry, X-ray photoelectron spectroscopy (XPS), and water contact angle measurement were utilized for the characterization of Laser-textured surfaces. It was found that in the same modification atmosphere, surface microstructure and roughness played a major role in changing the wetting behavior of polyimide film with varied Laser Fluence. However, in the three different atmospheres, when polyimide film was textured with the same Laser Fluence, no significant difference of surface microstructure and roughness was observed. Here, XPS analysis showed that O2 atmosphere was the most favorable environment for increasing surface oxygen-containing groups and realizing superhydrophilicity. Whereas, in N2 atmosphere, the least oxygen-containing groups were produced and the superhydrophilic surface could not be obtained. It could be inferred that the effect of different modification atmospheres on wettability was due to the change of surface chemistry. Understanding of wetting mechanism and fabricating superhydrophilic polyimide film would benefit the development of surface engineering for flexible electronics, microfluidics and adhesion applications.
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plasma confinement by hemispherical cavity in Laser induced breakdown spectroscopy
Applied Physics Letters, 2011Co-Authors: Y S Zhou, Lianbo Guo, B Y Zhang, Ziqiang Cai, Xiaoyan ZengAbstract:An aluminum hemispherical cavity (diameter: 11.1 mm) was used to confine plasmas produced by a KrF excimer Laser in air from a steel target with a low concentration manganese in Laser-induced breakdown spectroscopy. A significant enhancement (factor >12) in the emission intensity of Mn lines was observed at a Laser Fluence of 7.8 J/cm2 when the plasma was confined by the hemispherical cavity, leading to an increase in plasma temperature about 3600 K. The maximum emission enhancement increased with increasing Laser Fluence. The spatial confinement mechanism was discussed using shock wave theory.
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parameters and surface performance of Laser removal of rust layer on a3 steel
Surface & Coatings Technology, 2003Co-Authors: Zemin Wang, Xiaoyan Zeng, Weiling HuangAbstract:Rust layers were prepared on the surfaces of polished A3 (C1029 in AISI) steel blocks in an air furnace. The effects of Laser parameters on cleaning and performance of the cleaned surfaces were studied. The results demonstrate that rust layers can be removed completely with a pulsed Nd:YAG Laser at suitable Laser processing parameters. The repetition frequency has no apparent inFluence on the roughness of the cleaned surfaces. The roughness of the cleaned surface increases slightly with increasing Laser Fluence. Moreover, with the increase of the scanning velocity, the roughness of the cleaned surface increases considerable. Especially, the roughness of the cleaned surfaces can be remained unchanged by harmonizing different Laser parameters. The microhardness and corrosion resistance of the cleaned surfaces are improved after Laser cleaning and increase with increasing Laser Fluence.
Alain Jalocha - One of the best experts on this subject based on the ideXlab platform.
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experimental study of Laser induced plasma inFluence of Laser Fluence and pulse duration
Spectrochimica Acta Part B: Atomic Spectroscopy, 2013Co-Authors: Maxime Perrier, Vincent Mottoros, David Sabourdy, Luc Nguyen, Alain Jalocha, Jin YuAbstract:Abstract InFluence of Laser Fluence and pulse duration on the morphology and the internal structure of plasma induced by infrared nanosecond Laser pulse on an aluminum target placed in an argon ambient gas of one atmosphere pressure was experimentally studied. Dual-wavelength differential spectroscopic imaging was used in the experiment, which allowed observing the detailed structure inside of the ablation plume with distributions of species evaporated from the target as well as contributed by the ambient gas. Different regimes of post-ablation interaction were investigated using different Laser Fluences and pulse durations. We demonstrate in particular that plasma shielding due to various species localized in different zones inside of the plume leads to different morphologies and internal structures of the plasma. At moderate Fluence, the plasma shielding due to the ablation vapor localized in the central part of the plume leads to its nearly spherical expansion with a layered structure of the distribution of different species. At higher Fluence, the plasma shielding becomes strongly contributed by ionized ambient gas localized in the propagation front of the plume. An elongated morphology of the plume is observed with a zone of mixing between different species evaporated from the target or contributed by the ambient gas. Finally with extremely strong plasma shielding by ionized ambient gas in the case of a long duration pulse at high Fluence, a delayed evaporation from the target is observed due to the ejection of melted material by splashing.
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convoluted effect of Laser Fluence and pulse duration on the property of a nanosecond Laser induced plasma into an argon ambient gas at the atmospheric pressure
Journal of Applied Physics, 2013Co-Authors: Vincent Mottoros, Jin Yu, David Sabourdy, Luc Nguyen, Alain JalochaAbstract:We studied the behavior of the plasma induced by a nanosecond infrared (1064 nm) Laser pulse on a metallic target (Al) during its propagation into argon ambient gas at the atmospheric pressure and especially over the delay interval ranging from several hundred nanoseconds to several microseconds. In such interval, the plasma is particularly interesting as a spectroscopic emission source for Laser-induced plasma spectroscopy (LIBS). We show a convoluted effect between Laser Fluence and pulse duration on the structure and the emission property of the plasma. With a relatively high Fluence of about 160 J/cm2 where a strong plasma shielding effect is observed, a short pulse of about 4 ns duration is shown to be significantly more efficient to excite the optical emission from the ablation vapor than a long pulse of about 25 ns duration. While with a lower Fluence of about 65 J/cm2, a significantly more efficient excitation is observed with the long pulse. We interpret our observations by considering the post-a...
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Convoluted effect of Laser Fluence and pulse duration on the property of a nanosecond Laser-induced plasma into an argon ambient gas at the atmospheric pressure
Journal of Applied Physics, 2013Co-Authors: Xueshi Bai, David Sabourdy, Luc Nguyen, Vincent Motto-ros, Alain JalochaAbstract:We studied the behavior of the plasma induced by a nanosecond infrared (1064 nm) Laser pulse on a metallic target (Al) during its propagation into argon ambient gas at the atmospheric pressure and especially over the delay interval ranging from several hundred nanoseconds to several microseconds. In such interval, the plasma is particularly interesting as a spectroscopic emission source for Laser-induced plasma spectroscopy (LIBS). We show a convoluted effect between Laser Fluence and pulse duration on the structure and the emission property of the plasma. With a relatively high Fluence of about 160 J/cm2 where a strong plasma shielding effect is observed, a short pulse of about 4 ns duration is shown to be significantly more efficient to excite the optical emission from the ablation vapor than a long pulse of about 25 ns duration. While with a lower Fluence of about 65 J/cm2, a significantly more efficient excitation is observed with the long pulse. We interpret our observations by considering the post-ablation interaction between the generated plume and the tailing part of the Laser pulse. We demonstrate that the ionization of the layer of ambient gas surrounding the ablation vapor plays an important role in plasma shielding. Such ionization is the consequence of Laser-supported absorption wave and directly dependent on the Laser Fluence and the pulse duration. Further observations of the structure of the generated plume in its early stage of expansion support our explanations.
Shuji Sakabe - One of the best experts on this subject based on the ideXlab platform.
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derivation of effective penetration depth of femtosecond Laser pulses in metal from ablation rate dependence on Laser Fluence incidence angle and polarization
Applied Physics Letters, 2015Co-Authors: Yasuhiro Miyasaka, Takaya Nishii, Masaki Hashida, Shunsuke Inoue, Shuji SakabeAbstract:Ablation rate dependence on Laser Fluence for copper subjected to oblique femtosecond Laser irradiation has been determined experimentally in order to investigate processing induced by oblique irradiation. A difference of ablation rate between p-polarized and s-polarized oblique irradiation is clearly observed. Effective penetration depth is defined to explain the ablation rate dependence instead of using optical penetration depth, which is treated as a key value for determining the ablation rate in conventional theory. The effective penetration depth for copper is presented in simple formulas as a function of Laser incidence angle for each polarization.
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metal like self organization of periodic nanostructures on silicon and silicon carbide under femtosecond Laser pulses
Journal of Applied Physics, 2013Co-Authors: Laura Gemini, Yasuhiro Miyasaka, Masaki Hashida, Shunsuke Inoue, Shigeki Tokita, Masahiro Shimizu, J Limpouch, Tomas Mocek, Shuji SakabeAbstract:Periodic structures were generated on Si and SiC surfaces by irradiation with femtosecond Laser pulses. Self-organized structures with spatial periodicity of approximately 600 nm appear on silicon and silicon carbide in the Laser Fluence range just above the ablation threshold and upon irradiation with a large number of pulses. As in the case of metals, the dependence of the spatial periodicity on Laser Fluence can be explained by the parametric decay of Laser light into surface plasma waves. The results show that the proposed model might be universally applicable to any solid state material.
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periodic nano grating structures produced by femtosecond Laser pulses for metals with low and high melting points
Journal of Laser Micro Nanoengineering, 2012Co-Authors: Masaki Hashida, Yasuhiro Miyasaka, Shigeki Tokita, Yoshinobu Ikuta, Kazuto Otani, Shuji SakabeAbstract:Periodic nano-grating structures self-formed on the surface of several metals by femtosecond Laser pulses are analyzed by two-dimensional Fourier-transform. For the self-formation of grating structures on metal surfaces, the period of the structures depend on Laser Fluence. This dependence is the same for all metals, although the range of Laser Fluence in which the structures are formed differs between metals. For Ti with relatively low melting temperature(Tm=1938K) the grating nanostructures were self-formed for Laser Fluence of 0.09 – 0.45 J/cm 2 , while for Mo with high melting temperature (Tm =2888K) structures were formed for Laser Fluence of 0.18 – 1.1 J/cm 2 . Higher the melting temperature, upper limit of grating structure formation tends to be higher. These experimental results indicate that the period of the self-formed grating structure depend not on metal characteristics, but rather on the density of the surface plasma produced by a Laser pulse.
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Laser Fluence dependence of periodic grating structures formed on metal surfaces under femtosecond Laser pulse irradiation
Physical Review B, 2010Co-Authors: Kiminori Okamuro, Yasuhiro Miyasaka, Masaki Hashida, Shigeki Tokita, Yoshinobu Ikuta, Shuji SakabeAbstract:Periodic structures self-formed on the surface of several metals under femtosecond Laser-pulse irradiation are investigated by electron microscopy. For the self-formation of periodic gratings on metal surfaces, the interspaces of the periodic structures depend on Laser Fluence. This dependence is the same for all metals, although the range of Laser Fluence in which the structures are formed differs between metals. The Laser Fluence dependence can be explained by the generation of a plasma wave through the parametric decay of Laser light [S. Sakabe, M. Hashida, S. Tokita, S. Namba, and K. Okamuro, Phys. Rev. B 79, 033409 (2009)]. This indicates that the formation of periodic structures depends not only on metal properties but also on the electron density of plasma produced on a surface by femtosecond Laser pulses.
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ion emission from a metal surface through a multiphoton process and optical field ionization
Physical Review B, 2010Co-Authors: Masaki Hashida, Shin Namba, Kiminori Okamuro, Shigeki Tokita, Shuji SakabeAbstract:In order to investigate the physics of ion emission under an intense optical field, the ions emitted from a Laser-irradiated copper surface were studied by time-of-flight energy spectroscopy. The lowest Laser Fluence at which ions are emitted, ${F}_{th,L}$, is $0.028\text{ }\text{J}/{\text{cm}}^{2}$, and two higher emission thresholds were identified at Fluences of ${F}_{th,M}=0.195\text{ }\text{J}/{\text{cm}}^{2}$ and ${F}_{th,H}=0.470\text{ }\text{J}/{\text{cm}}^{2}$. The relation between the number of emitted ions per pulse ${N}_{i}$ and the Laser Fluence $F$ was in good agreement with ${N}_{i}\ensuremath{\propto}{F}^{4}$ for ${F}_{th,L}\ensuremath{-}{F}_{th,M}$, ${N}_{i}\ensuremath{\propto}{F}^{3}$ for ${F}_{th,M}\ensuremath{-}{F}_{th,H}$, and ${N}_{i}\ensuremath{\propto}{F}^{2}$ for $\ensuremath{\ge}{F}_{th,H}$. The dependence of ion production on Laser energy Fluence is explained well by multiphoton absorption and optical field ionization. Even at a low Laser Fluence such as $0.136\text{ }\text{J}/{\text{cm}}^{2}$, the emitted ions have an energy of 30 eV, and the ion energy depends on the Laser Fluence (790 eV at $14.4\text{ }\text{J}/{\text{cm}}^{2}$). The Laser Fluence dependence of ion energy is reasonably well related to those of the interspaces of gratings that are self-organized on a metal surface by femtosecond Laser pulses.
Yuan T Lee - One of the best experts on this subject based on the ideXlab platform.
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ion to neutral ratio of 2 5 dihydroxybenzoic acid in matrix assisted Laser desorption ionization
Rapid Communications in Mass Spectrometry, 2013Co-Authors: Mingtsang Tsai, Sheng Lee, Kuanyu Chu, Chiwei Liang, Chihhao Lee, Yuan T LeeAbstract:RATIONALE In most previous studies, the ratios of desorbed ions and neutrals from matrix-assisted Laser desorption/ionization (MALDI) were measured outside the common MALDI conditions. In this work, we measured the ratios under common MALDI conditions. METHODS Ions were detected using a time-of-flight mass spectrometer in combination with a time-gated ion imaging detector. Mass-resolved desorbed neutral molecules at different angles and velocities were measured using a modified crossed molecular beam apparatus. RESULTS The upper limit of the ion-to-neutral ratio from pure 2,5-dihydroxybenzoic acid (25DHB) is 4 × 10−9 at Laser Fluence 40 J/m2, it increases to 3 × 10−7 at Laser Fluence 250 J/m2. The ratios of matrix from the mixture of 25DHB and analyte remain in the same order of magnitude as pure 25DHB. However, the ratio of analyte depends strongly on the analyte. Values as large as 10−3–10−4 for bradykinin and as small as <10−8 for glycine were observed at Laser Fluence ~100 J/m2. CONCLUSION The ion-to-neutral ratios of 25DHB matrix measured in this work are much smaller than some of the values reported in previous work using different methods and/or under different MALDI conditions. Copyright © 2013 John Wiley & Sons, Ltd.
Xizhao Wang - One of the best experts on this subject based on the ideXlab platform.
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effect of parameters on picosecond Laser ablation of cr12mov cold work mold steel
Applied Physics A, 2018Co-Authors: Peng Liu, Fei Zhang, Jun Duan, Xizhao Wang, Xiaoyan ZengAbstract:Cr12MoV cold work mold steel, which is a difficult-to-machining material, is widely used in the mold and dye industry. A picosecond pulse Nd:YVO4 Laser at 1064 nm was used to conduct the study. Effects of operation parameters (i.e., Laser Fluence, scanning speed, hatched space and number of scans) were studied on ablation depth and quality of Cr12MoV at the repetition rate of 20 MHz. The experimental results reveal that all the four parameters affect the ablation depth significantly. While the surface roughness depends mainly on Laser Fluence or scanning speed and secondarily on hatched space or number of scans. For Laser Fluence and scanning speed, three distinct surface morphologies were observed experiencing transition from flat (Ra 2.40 μm). However, for hatched space and number of scan, there is a small bumpy and rough zone or even no rough zone. Mechanisms including heat accumulation, plasma shielding and combustion reaction effects are proposed based on the ablation depth and processing morphology. By appropriate management of the Laser Fluence and scanning speed, high ablation depth with low surface roughness can be obtained at small hatched space and high number of scans.
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study on picosecond pulse Laser ablation of cr12mov cold work mold steel
Materials & Design, 2016Co-Authors: Peng Liu, Jun Duan, Xiaoyan Zeng, Leimin Deng, Xizhao WangAbstract:Abstract Cr12MoV has wide applications in the molds and dies industry. However, it is also a hard-to-machining material due to its high mechanical strength and hardness. Area ablation of Cr12MoV cold-work mold steel was carried out using a picosecond (ps) pulse Nd:YVO4 Laser. The effects of Laser Fluence and wavelength on the ablation rate and machining quality were investigated with wavelengths of 1064 nm, 532 nm and 355 nm. The experimental results indicate a logarithmic increase of the ablation rate to a maximum value of ~ 41 nm/pulse with the increase of Laser Fluence using the wavelengths of 1064 nm and 355 nm. For the wavelength of 532 nm, an ablation rate of ~ 33 nm/pulse is achieved at low Laser Fluence of 8.28 J/cm2, then increases logarithmically into about 54 nm/pulse at 25.10 J/cm2, and then decreases steeply into almost zero as the Laser Fluence increases above 25.10 J/cm2. For the three Laser wavelengths, different pore sizes were observed in the Laser ablation region. The surface roughness increases exponentially with the increase of the Laser Fluence. The inFluence mechanisms of Laser Fluence and wavelength on the Laser ablation rate and machining quality were systematically analyzed and discussed in this paper.
