Laser cleaning, as a conservation technique, is a selective, precise and minimal intrusive method... more Laser cleaning, as a conservation technique, is a selective, precise and minimal intrusive method of removing corrosion product layers. Nevertheless, in order to optimise this method as a standard conservation technique, it is still necessary to define different laser cleaning methodologies. In this study, laser cleaning was performed with near-IR lasers on artificially aged copper specimens and on two copper coins coming from Bubastis (Egypt) in order to remove the patinas in a totally non invasive way. Different irradiance and different number of passes were utilised and compared. Treated surface is characterised by optical and scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Results show that near-IR laser has successfully removed corrosion products from the surface. An alteration of the metallic surface is observed only after treatments performed with higher irradiance values or with numerous passes.
Page 1. 185 macla nº 9. septiembre '08 revista de la sociedad española de mineralogí... more Page 1. 185 macla nº 9. septiembre '08 revista de la sociedad española de mineralogía Síntesis de Zeolitas (Silicalita-1) sobre Sustratos Modificados Mediante Ablación Láser / JAVIER PÉREZ CARVAJAL (1), LAURA QUIJANO ...
2013 Conference on Lasers & Electro-Optics Europe & International Quantum Electronics Conference CLEO EUROPE/IQEC, 2013
ABSTRACT form only given. The formation of Laser-Induced Periodic Surface Structures (LIPSS) is a... more ABSTRACT form only given. The formation of Laser-Induced Periodic Surface Structures (LIPSS) is a universal phenomenon [1] that can be observed in a wide variety of materials under certain irradiation conditions. Although the study of sub-wavelength LIPSS in semiconductors and dielectrics irradiated below bandgap has been particularly intense [2], the formation of LIPSS in metals have also been given attention due to its specific features [3,4,5] that have been related to the characteristics of electron-phonon coupling, plasma density and electron diffusion upon fs-laser irradiation at low repetition rates. In this work we report on the unique characteristics of low spatial frequency LIPSS patterns fabricated in Cr upon high repetition rate fs-laser irradiation employing beam scanning. Highly regular patterns with sub-wavelength period can be produced for a wide range of repetition rates (100's kHz range), over large areas (~cm2) and high scan speeds (~m/s).The experiments have been performed with a fs-fibre-laser amplifier (Tangerine, Amplitude Systemes) delivering ≈ 400 fs at 1030 nm and a repetition rate from 50 kHz up to 2 MHz. A galvo-scanner system enables to raster-scan the beam over the sample surface by focusing it with a f=100 mm, f-theta lens to a spot diameter of ≈ 30 μm. Different irradiation conditions (laser repetition rate, beam polarization, pulse energy, scan speed and scan line separation...) have been explored. Figure 1 shows AFM images of LIPSS patters formed by scanning the surface of a sample at v=1500 mm/s, and a repetition rate of 500 kHz for three different pulse energies. In all cases the ripples are formed perpendicular to the polarization axis with period (typically -0.85 μm) smaller than the laser wavelength. The best results in terms of modulation are observed for the scanning direction perpendicular to the polarization axis. High energies (Fig. 1a) produce well-defined and aligned ripples bu- the uniformity is worse than for lower ones (Fig. 1b) featuring a ripple substructure. If the pulse energy is further reduced, (Fig. 1c) the ripple structure becomes discontinuous. Extremely homogenous large-area grating structures with a modulation depth of several hundreds of nanometers have been produced for different repetition rates and scan speeds.In the work we analyse the role of the different irradiation parameters on the characteristics of the generated structures and discuss their origin in the frame of the models presently used for LIPSS formation in metals [3,4,5] with emphasis on the possible influence of thermal accumulation and geometrical factors on the homogeneous propagation of the sub-wavelength structure over macroscopic regions.
MOF micromembranes of 20–32 μm diameter were prepared by synthesizing ZIF-8 on Nd:YAG laser-perfo... more MOF micromembranes of 20–32 μm diameter were prepared by synthesizing ZIF-8 on Nd:YAG laser-perforated 75 μm thick brass sheets (63/37 Cu/Zn). The membranes were applied to the separation of H2–CH4, He–CH4, CO2–CH4and O2–N2mixtures.
Silicalite-1 micromembranes of approximately 80 μm in diameter have been prepared by synthesizing... more Silicalite-1 micromembranes of approximately 80 μm in diameter have been prepared by synthesizing the zeolite material inside a network of perforations created by using a NdYAG laser on 75 μm thick stainless steel sheets. Several strategies have been introduced here to reduce the ...
2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), 2019
Laser tailoring has been used for increasing the active area of the yttria stabilised zircona (YS... more Laser tailoring has been used for increasing the active area of the yttria stabilised zircona (YSZ) electrolyte interface in solid oxide fuel cells to reduce the polarisation losses and improve the cell electrochemical performance.
Resumen del trabajo presentado al 7th International Congress on Ceramics (ICC), celebrado en Foz ... more Resumen del trabajo presentado al 7th International Congress on Ceramics (ICC), celebrado en Foz de Iguazu (Brasil) del 17 al 21 de junio de 2018.
ABSTRACT Back-scattered Scanning Electron Microscopy (BSEM) has been used to identify weathering ... more ABSTRACT Back-scattered Scanning Electron Microscopy (BSEM) has been used to identify weathering mechanisms occurring in two oolitic limestones from urban areas in London and Cambridge, United Kingdom. From a petrographical point of view, the two stones can be described as oosparite and oomicrite, their main distinctive feature being the crystal size of the cement binding the limestone grains together. The sulphation mechanism, i.e. the replacement of calcium carbonate (calcite: CaCO3) by calcium sulphate dehydrate (gypsum: CaSO4 2H2O), at the surface and within the stone fabric is confirmed as the general decay process. Differences in macroporosity/permeability distribution in the two limestones lead to different weathering patterns. BSEM provides evidence that gypsum patinas still commonly found on limestone facades in polluted urban locations are advancing inside the diseased stone and that their removal is urgently needed to arrest the growth of the in-growing weathering front.
Trabajo presentado al 8th Annual Low Carbon Earth Summit, celebrado en Qingdao (China) del 23 al ... more Trabajo presentado al 8th Annual Low Carbon Earth Summit, celebrado en Qingdao (China) del 23 al 25 de octubre de 2018.
Resumen del trabajo presentado al LII Congreso Anual de la Sociedad Espanola de Ceramica y Vidrio... more Resumen del trabajo presentado al LII Congreso Anual de la Sociedad Espanola de Ceramica y Vidrio celebrado en Burgos del 3 al 6 de octubre de 2012.
Laser cleaning, as a conservation technique, is a selective, precise and minimal intrusive method... more Laser cleaning, as a conservation technique, is a selective, precise and minimal intrusive method of removing corrosion product layers. Nevertheless, in order to optimise this method as a standard conservation technique, it is still necessary to define different laser cleaning methodologies. In this study, laser cleaning was performed with near-IR lasers on artificially aged copper specimens and on two copper coins coming from Bubastis (Egypt) in order to remove the patinas in a totally non invasive way. Different irradiance and different number of passes were utilised and compared. Treated surface is characterised by optical and scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Results show that near-IR laser has successfully removed corrosion products from the surface. An alteration of the metallic surface is observed only after treatments performed with higher irradiance values or with numerous passes.
Page 1. 185 macla nº 9. septiembre '08 revista de la sociedad española de mineralogí... more Page 1. 185 macla nº 9. septiembre '08 revista de la sociedad española de mineralogía Síntesis de Zeolitas (Silicalita-1) sobre Sustratos Modificados Mediante Ablación Láser / JAVIER PÉREZ CARVAJAL (1), LAURA QUIJANO ...
2013 Conference on Lasers & Electro-Optics Europe & International Quantum Electronics Conference CLEO EUROPE/IQEC, 2013
ABSTRACT form only given. The formation of Laser-Induced Periodic Surface Structures (LIPSS) is a... more ABSTRACT form only given. The formation of Laser-Induced Periodic Surface Structures (LIPSS) is a universal phenomenon [1] that can be observed in a wide variety of materials under certain irradiation conditions. Although the study of sub-wavelength LIPSS in semiconductors and dielectrics irradiated below bandgap has been particularly intense [2], the formation of LIPSS in metals have also been given attention due to its specific features [3,4,5] that have been related to the characteristics of electron-phonon coupling, plasma density and electron diffusion upon fs-laser irradiation at low repetition rates. In this work we report on the unique characteristics of low spatial frequency LIPSS patterns fabricated in Cr upon high repetition rate fs-laser irradiation employing beam scanning. Highly regular patterns with sub-wavelength period can be produced for a wide range of repetition rates (100's kHz range), over large areas (~cm2) and high scan speeds (~m/s).The experiments have been performed with a fs-fibre-laser amplifier (Tangerine, Amplitude Systemes) delivering ≈ 400 fs at 1030 nm and a repetition rate from 50 kHz up to 2 MHz. A galvo-scanner system enables to raster-scan the beam over the sample surface by focusing it with a f=100 mm, f-theta lens to a spot diameter of ≈ 30 μm. Different irradiation conditions (laser repetition rate, beam polarization, pulse energy, scan speed and scan line separation...) have been explored. Figure 1 shows AFM images of LIPSS patters formed by scanning the surface of a sample at v=1500 mm/s, and a repetition rate of 500 kHz for three different pulse energies. In all cases the ripples are formed perpendicular to the polarization axis with period (typically -0.85 μm) smaller than the laser wavelength. The best results in terms of modulation are observed for the scanning direction perpendicular to the polarization axis. High energies (Fig. 1a) produce well-defined and aligned ripples bu- the uniformity is worse than for lower ones (Fig. 1b) featuring a ripple substructure. If the pulse energy is further reduced, (Fig. 1c) the ripple structure becomes discontinuous. Extremely homogenous large-area grating structures with a modulation depth of several hundreds of nanometers have been produced for different repetition rates and scan speeds.In the work we analyse the role of the different irradiation parameters on the characteristics of the generated structures and discuss their origin in the frame of the models presently used for LIPSS formation in metals [3,4,5] with emphasis on the possible influence of thermal accumulation and geometrical factors on the homogeneous propagation of the sub-wavelength structure over macroscopic regions.
MOF micromembranes of 20–32 μm diameter were prepared by synthesizing ZIF-8 on Nd:YAG laser-perfo... more MOF micromembranes of 20–32 μm diameter were prepared by synthesizing ZIF-8 on Nd:YAG laser-perforated 75 μm thick brass sheets (63/37 Cu/Zn). The membranes were applied to the separation of H2–CH4, He–CH4, CO2–CH4and O2–N2mixtures.
Silicalite-1 micromembranes of approximately 80 μm in diameter have been prepared by synthesizing... more Silicalite-1 micromembranes of approximately 80 μm in diameter have been prepared by synthesizing the zeolite material inside a network of perforations created by using a NdYAG laser on 75 μm thick stainless steel sheets. Several strategies have been introduced here to reduce the ...
2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), 2019
Laser tailoring has been used for increasing the active area of the yttria stabilised zircona (YS... more Laser tailoring has been used for increasing the active area of the yttria stabilised zircona (YSZ) electrolyte interface in solid oxide fuel cells to reduce the polarisation losses and improve the cell electrochemical performance.
Resumen del trabajo presentado al 7th International Congress on Ceramics (ICC), celebrado en Foz ... more Resumen del trabajo presentado al 7th International Congress on Ceramics (ICC), celebrado en Foz de Iguazu (Brasil) del 17 al 21 de junio de 2018.
ABSTRACT Back-scattered Scanning Electron Microscopy (BSEM) has been used to identify weathering ... more ABSTRACT Back-scattered Scanning Electron Microscopy (BSEM) has been used to identify weathering mechanisms occurring in two oolitic limestones from urban areas in London and Cambridge, United Kingdom. From a petrographical point of view, the two stones can be described as oosparite and oomicrite, their main distinctive feature being the crystal size of the cement binding the limestone grains together. The sulphation mechanism, i.e. the replacement of calcium carbonate (calcite: CaCO3) by calcium sulphate dehydrate (gypsum: CaSO4 2H2O), at the surface and within the stone fabric is confirmed as the general decay process. Differences in macroporosity/permeability distribution in the two limestones lead to different weathering patterns. BSEM provides evidence that gypsum patinas still commonly found on limestone facades in polluted urban locations are advancing inside the diseased stone and that their removal is urgently needed to arrest the growth of the in-growing weathering front.
Trabajo presentado al 8th Annual Low Carbon Earth Summit, celebrado en Qingdao (China) del 23 al ... more Trabajo presentado al 8th Annual Low Carbon Earth Summit, celebrado en Qingdao (China) del 23 al 25 de octubre de 2018.
Resumen del trabajo presentado al LII Congreso Anual de la Sociedad Espanola de Ceramica y Vidrio... more Resumen del trabajo presentado al LII Congreso Anual de la Sociedad Espanola de Ceramica y Vidrio celebrado en Burgos del 3 al 6 de octubre de 2012.
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