The Experts below are selected from a list of 269136 Experts worldwide ranked by ideXlab platform
Hiroshi Ogawa - One of the best experts on this subject based on the ideXlab platform.
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Surface Processing of pmma and metal nano particle resist by sub micrometer focusing of coherent extreme ultraviolet high order harmonics pulses
Optics Letters, 2020Co-Authors: Kazuyuki Sakaue, Hiroto Motoyama, Ryosuke Hayashi, Atsushi Iwasaki, Hidekazu Mimura, Kaoru Yamanouchi, Tatsunori Shibuya, Masahiko Ishino, Thanhhung Dinh, Hiroshi OgawaAbstract:We demonstrate sub-micrometer Processing of two kinds of thin films, polymethyl methacrylate (PMMA) and metal nano-particle resist, by focusing high-order harmonics of near-IR femtosecond laser pulses in the extreme ultraviolet (XUV) wavelength region (27.2–34.3 nm) on the thin film samples using an ellipsoidal focusing mirror. The ablation threshold fluences for the PMMA sample and the metal nano-particle resist per XUV pulse obtained by the accumulation of 200 XUV pulses were determined to be 0.42mJ/cm2 and 0.17mJ/cm2, respectively. The diameters (FWHM) of a hole created by the ablation on the PMMA film at the focus were 0.67 µm and 0.44 µm along the horizontal direction and the vertical direction, respectively. The fluence dependence of the Raman microscope spectra of the processed holes on the PMMA sample showed that the chemical modification, in which C=C double bonds are formed associated with the scission of the PMMA polymer chains, is achieved by the irradiation of the XUV pulses.
Kazuyuki Sakaue - One of the best experts on this subject based on the ideXlab platform.
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Surface Processing of pmma and metal nano particle resist by sub micrometer focusing of coherent extreme ultraviolet high order harmonics pulses
Optics Letters, 2020Co-Authors: Kazuyuki Sakaue, Hiroto Motoyama, Ryosuke Hayashi, Atsushi Iwasaki, Hidekazu Mimura, Kaoru Yamanouchi, Tatsunori Shibuya, Masahiko Ishino, Thanhhung Dinh, Hiroshi OgawaAbstract:We demonstrate sub-micrometer Processing of two kinds of thin films, polymethyl methacrylate (PMMA) and metal nano-particle resist, by focusing high-order harmonics of near-IR femtosecond laser pulses in the extreme ultraviolet (XUV) wavelength region (27.2–34.3 nm) on the thin film samples using an ellipsoidal focusing mirror. The ablation threshold fluences for the PMMA sample and the metal nano-particle resist per XUV pulse obtained by the accumulation of 200 XUV pulses were determined to be 0.42mJ/cm2 and 0.17mJ/cm2, respectively. The diameters (FWHM) of a hole created by the ablation on the PMMA film at the focus were 0.67 µm and 0.44 µm along the horizontal direction and the vertical direction, respectively. The fluence dependence of the Raman microscope spectra of the processed holes on the PMMA sample showed that the chemical modification, in which C=C double bonds are formed associated with the scission of the PMMA polymer chains, is achieved by the irradiation of the XUV pulses.
Jonathan Lawrence - One of the best experts on this subject based on the ideXlab platform.
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mathematical modelling of the fibre laser Surface Processing of a zirconia engineering ceramic by means of three dimensional finite element analysis
Proceedings of the Institution of Mechanical Engineers Part C: Journal of Mechanical Engineering Science, 2011Co-Authors: Pratik Shukla, Jonathan LawrenceAbstract:The thermal effects of fibre laser Surface treatment on a ZrO2 engineering ceramic were studied using a computational finite element model (FEM). Temperature increases on the Surface and the bulk of the ZrO2 during the fibre laser Processing were measured using an infra-red thermometer and specifically located thermocouples. The results showed an error of 5% with the Surface and 18% within the bulk of the ZrO2 when comparing the experimental readings with those of the FEM. The FEM revealed a relationship between the traverse speed; power density; time; depth and the temperature during various stages of the fibre laser Surface treatment of the ZrO2. By utilizing data obtained from a thermo, gravimetry- differential scanning calorimetry (TG-DSC), the FEM predictions of the temperature distribution were used to map phase transformations and significant events occurring during the fibre laser Surface treatment of the ZrO2. The mapping revealed that the fibre laser Surface treatment generally resulted in a phase transformation of the ZrO2 at various temperatures changes as further shown in the paper.
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mathematical modelling of the fibre laser Surface Processing of a zirconia engineering ceramic by means of three dimensional finite element analysis
Proceedings of the Institution of Mechanical Engineers Part C: Journal of Mechanical Engineering Science, 2011Co-Authors: Pratik Shukla, Jonathan LawrenceAbstract:The thermal effects of fibre laser Surface treatment on a ZrO2 engineering ceramic were studied using a computational finite-element model (FEM). Temperature increases on the Surface and the bulk of the ZrO2 during the fibre laser Processing were measured using an infra-red thermometer and specifically located thermocouples. The results showed an error of 5 per cent with the Surface and 18 per cent within the bulk of the ZrO2 when comparing the experimental readings with those of the FEM. The FEM revealed a relationship between the traverse speed, power density, time, depth, and the temperature during various stages of the fibre laser Surface treatment of the ZrO2. By utilizing data obtained from a thermogravimetry-differential scanning calorimetry (TG-DSC), the FEM predictions of the temperature distribution were used to map phase transformations and significant events occurring during the fibre laser Surface treatment of the ZrO2. The mapping revealed that the fibre laser Surface treatment generally resulted in a phase transformation of the ZrO2 at various temperatures changes as further shown in the article.
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fracture toughness modifications by means of co2 laser beam Surface Processing of a silicon nitride engineering ceramic
36th International MATADOR Conference, 2010Co-Authors: Pratik Shukla, Jonathan LawrenceAbstract:Surface treatment of an Si3N4 engineering ceramic with a CO2 laser was carried out to identify changes in the fracture toughness (K1c). A Vickers macro hardness indentation method was adopted to determine the K1C prior to and after the CO2 laser treatment. After determination of the Surface integrity, crack geometry, crack lengths and the dimensions of the diamond indentations, computational and analytical methods were employed to calculate the K1c. A decrease in the Surface hardness of nearly 7% and of 44% in the resulting crack lengths was found after laser treatment. This inherently led to a 64% increase in the K1c for the Si3N4. This could have occurred due to melting and redistribution of the melt zone which softened the near (top) Surface layer forming a degree of oxidation, causing the Surface of the engineering ceramic to transform into a new composition.
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Fracture toughness of a zirconia engineering ceramic and the effects thereon of Surface Processing with fibre laser radiation
Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2010Co-Authors: H. Wu, P P Shukla, Jonathan LawrenceAbstract:Vickers hardness indentation tests were employed to investigate the near-Surface changes in the hardness of a fibre laser-treated and an as-received ZrO2 engineering ceramic. Indents were created using 5, 20, and 30 kg loads to obtain the hardness. Optical microscopy, white-light interferometry, and a coordinate measuring machine were then used to observe the crack lengths and crack geometry. Palmqvist and half-penny median crack profiles were found, which dictated the selection of the group of equations used herein. Computational and analytical approaches were then adapted to determine the K1c of ZrO2. It was found that the best applicable equation was: K1c = 0.016 (E/H)1/2 (P/c3/2), which was confirmed to be 42 per cent accurate in producing K1c values within the range of 8 to 12 MPa m1/2 for ZrO2. Fibre laser Surface treatment reduced the Surface hardness and produced smaller crack lengths in comparison with the as-received Surface. The Surface crack lengths, hardness, and indentation loads were found to be important, particularly the crack length, which significantly influenced the end K1c value when K1c = 0.016 (E/H)1/2 (P/c3/2) was used. This is because, the longer the crack lengths, the lower the ceramic's resistance to indentation. This, in turn, increased the end K1c value. Also, the hardness influences the K1c, and a softer Surface was produced by the fibre laser treatment; this resulted in higher resistance to crack propagation and enhanced the ceramic's K1c. Increasing the indentation load also varied the end K1c value, as higher indentation loads resulted in a bigger diamond footprint, and the ceramic exhibited longer crack lengths.
Peter Schaaf - One of the best experts on this subject based on the ideXlab platform.
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free electron laser Surface Processing of titanium in nitrogen atmosphere
Applied Surface Science, 2005Co-Authors: Ettore Carpene, Michelle D. Shinn, Peter SchaafAbstract:Abstract Surface treatment by means of pulsed laser beams in reactive atmospheres is an attractive technique to enhance the Surface features, such as corrosion, wear resistances and hardness. Among all laser types, the free-electron laser (FEL) is relatively new for materials Processing, its main peculiarity being the versatile pulse structure, with high repetition rates (the so-called macropulse). We have employed the FEL at the Jefferson Lab (Virginia, USA) to irradiate pure titanium substrates in nitrogen atmosphere. The influence of various experimental parameters (macropulse duration, spot overlap and laser fluence) on the nitrogen incorporation and the resulting microstructures has been investigated. It will be shown that the laser treatment is not only a successful way to form titanium nitride, but also that a proper set of the experimental parameters can efficiently control the growth mechanism and the crystallographic texture of the resulting nitride phase, leading to the synthesis of highly oriented δ-TiN(2 0 0) layers. As it will be shown, the Surface features strongly depends on the irradiation conditions: in particular a very smooth, crack-free Surface can be obtained with small spot overlap and long macropulses (1000 μs), while the roughness increases with large overlap and short macropulses (
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Reactive Surface Processing by irradiation with excimer laser, Nd:YAG laser, free electron laser and Ti:sapphire laser in nitrogen atmosphere
Applied Surface Science, 2002Co-Authors: Ettore Carpene, Klaus-peter Lieb, Peter Schaaf, Michelle D. ShinnAbstract:Abstract Surface coatings and thin films can be easily produced by irradiation of materials with short laser pulses in (reactive) gas atmospheres, e.g. nitrided iron and steel or AlN films on Al and its alloys by irradiation with an excimer laser in nitrogen atmosphere. For these treatments, various lasers with different wavelengths and time structures can be used. In addition to the experiments with excimer laser (pulse duration: 55 ns; wavelength: 308 nm), also the results of irradiations with Nd:YAG laser (pulse duration: 8 ns; wavelength: 1060 nm), free electron laser (FEL) (pulse duration: 2 ps; wavelength: 3 μm) and Ti:sapphire laser (pulse duration: 150 fs; wavelength: 750 nm) will be presented. The pulse duration varies from nanoseconds to femtoseconds and thus includes different laser interaction regimes. The results of the Surface modifications and coating formation for the irradiation of different types of materials (Fe, Al, Si, and Ti) in pure nitrogen atmosphere will be presented.
Ettore Carpene - One of the best experts on this subject based on the ideXlab platform.
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free electron laser Surface Processing of titanium in nitrogen atmosphere
Applied Surface Science, 2005Co-Authors: Ettore Carpene, Michelle D. Shinn, Peter SchaafAbstract:Abstract Surface treatment by means of pulsed laser beams in reactive atmospheres is an attractive technique to enhance the Surface features, such as corrosion, wear resistances and hardness. Among all laser types, the free-electron laser (FEL) is relatively new for materials Processing, its main peculiarity being the versatile pulse structure, with high repetition rates (the so-called macropulse). We have employed the FEL at the Jefferson Lab (Virginia, USA) to irradiate pure titanium substrates in nitrogen atmosphere. The influence of various experimental parameters (macropulse duration, spot overlap and laser fluence) on the nitrogen incorporation and the resulting microstructures has been investigated. It will be shown that the laser treatment is not only a successful way to form titanium nitride, but also that a proper set of the experimental parameters can efficiently control the growth mechanism and the crystallographic texture of the resulting nitride phase, leading to the synthesis of highly oriented δ-TiN(2 0 0) layers. As it will be shown, the Surface features strongly depends on the irradiation conditions: in particular a very smooth, crack-free Surface can be obtained with small spot overlap and long macropulses (1000 μs), while the roughness increases with large overlap and short macropulses (
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Reactive Surface Processing by irradiation with excimer laser, Nd:YAG laser, free electron laser and Ti:sapphire laser in nitrogen atmosphere
Applied Surface Science, 2002Co-Authors: Ettore Carpene, Klaus-peter Lieb, Peter Schaaf, Michelle D. ShinnAbstract:Abstract Surface coatings and thin films can be easily produced by irradiation of materials with short laser pulses in (reactive) gas atmospheres, e.g. nitrided iron and steel or AlN films on Al and its alloys by irradiation with an excimer laser in nitrogen atmosphere. For these treatments, various lasers with different wavelengths and time structures can be used. In addition to the experiments with excimer laser (pulse duration: 55 ns; wavelength: 308 nm), also the results of irradiations with Nd:YAG laser (pulse duration: 8 ns; wavelength: 1060 nm), free electron laser (FEL) (pulse duration: 2 ps; wavelength: 3 μm) and Ti:sapphire laser (pulse duration: 150 fs; wavelength: 750 nm) will be presented. The pulse duration varies from nanoseconds to femtoseconds and thus includes different laser interaction regimes. The results of the Surface modifications and coating formation for the irradiation of different types of materials (Fe, Al, Si, and Ti) in pure nitrogen atmosphere will be presented.
