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Pressure measurement in combusting and non-combusting gases using laser-induced grating spectroscopy
摘要： The measurement of pressure using laser-induced thermal grating spectroscopy, LITGS, with improved accuracy and precision is reported. Pressure values are derived from the record of the time-profile of LITGS signals by fitting of modelled signals to experimental data. The procedure is described for accurate modelling of the LIGS signals involving a sequence of calculation steps with appropriate weighting and calibration to determine the best-fit value of pressure-dependent parameters for averaged and single-shot measurements. Results are reported showing application of this model-fitting method to measurements of pressure in static cells using LITGS generated from NO in mixtures containing N2 at pressures in the range 0.5–5.0 bar with accuracy of 1–3% and single-shot precision of 4–7%. Time-resolved measurements of pressure, using LITGS signals generated in toluene-seeded fuel vapour, during the compression and expansion strokes of a motored optically accessible engine are reported with pressure-dependent accuracy ranging from better than 10 to around 20% over the cycle and single-shot precision in the range 5–15% over the same range. Measurements in the engine under firing conditions were obtained over a limited range and slightly increased uncertainties associated with varying composition resulting from exhaust gas residuals. The method was found to be of limited utility for measurements in high temperature flames at around ambient pressures.
关键词： Combustion,Laser-induced thermal grating spectroscopy,Non-combusting gases,Pressure measurement,LITGS
更新于2025-11-25 10:30:42
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Novel combined instrumentation for laser-induced breakdown spectroscopy and Raman spectroscopy for the <i>in situ</i> atomic and molecular analysis of minerals
摘要： An instrument combining laser-induced breakdown spectroscopy (LIBS) and Raman spectroscopy was developed for the in situ atomic and molecular composition analysis of minerals. The apparatus consists of an optical system, a sample chamber, a spectrometer for Raman and another for LIBS, as well as a control system equipped with laboratory-written software. Gypsum, calcite, prehnite, pearl, lazurite, and several mixtures of NaBr and CaCO3 were selected as samples for evaluation of the performance of the instrument. Sulfate, carbonate, silicate, and crystalline water were identified and different structures of CaCO3 were clearly distinguished by the use of a Gaussian fit. The limit of detection for CaCO3 in a NaBr mixture was 5.7 mg/g by Raman. LIBS was employed to determine calcium, magnesium, iron, sodium, aluminum, and carbon with the newly developed system. The limits of detection obtained for Ca, Na, and C were 90.2 lg/g, 84.6 lg/g, and 2.5 mg/g, respectively. The experimental results from commercial Raman spectroscopy instruments were used to verify and support the measurements from this novel instrument.
关键词： Instrumentation,Raman spectroscopy,laser-induced breakdown spectroscopy (LIBS),mineral,LIBRAS
更新于2025-11-25 10:30:42
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Investigation on the crack fracture mode and edge quality in laser dicing of glass-anisotropic silicon double-layer wafer
摘要： This work puts forward numerical and experimental investigations on laser dicing of glass-anisotropic single-crystal silicon double-layer wafer using laser induced thermal-crack propagation (LITP). A semiconductor continuous wave laser working at the defocusing mode serves as volumetric heat source for glass layer while as surface heat source for silicon layer. Based on the classical fracture theory, a static seam-type crack is introduced under the circumstance of ABAQUS to simulate the crack fracture modes in glass layer as well as silicon layer with crystal planes of (100), (110) and (111) during laser dicing in different dicing directions. In the experiments, processing parameters are kept the same as the simulations and typical dicing directions obtained from simulations are also used. The surface morphologies of crack edges are measured by the optical microscope and surface profiler. Through the comparison of numerical and experimental results it is discovered that for the specific substrate, the evolution of crack edge qualities in different dicing directions and different layers can be interpreted based on the corresponding stress distribution and stress intensity factor (SIF) ratio explicitly. And most important of all, the anisotropy of silicon layer has significant influence on the fracture mode and edge quality of crack in both layers.
关键词： Crack fracture mode,Laser induced thermal-crack propagation,Glass-anisotropic single-crystal silicon double-layer wafer,Crack edge quality,Static seam-type crack
更新于2025-11-21 11:24:58
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Repulsive magnetic field–assisted laser-induced plasma micromachining for high-quality microfabrication
摘要： Surface micro-/nanostructures are widely used in the fabrication of various functional microsystems. Laser-induced plasma micromachining can greatly improve surface quality in terms of recast layers and thermal defects compared with laser direct writing. Magnetic field has the ability to constrain plasma diffusion and can ensure the stability of laser-induced plasma processing. This paper compares the effects of laser direct–writing processing and laser-induced plasma processing of single-crystal silicon at the micro-/nanoscale, and emphatically analyzes the material removal mechanism of repulsive magnetic field–assisted laser-induced plasma micromachining. It is shown that the volume of the laser-induced plasma was constrained under the influence of Lorentz force, a high-quality smooth microgroove without thermal defects was obtained, and its line width was reduced by 30%.
关键词： Laser-induced plasma micromachining,Magnetic confinement,Thermal defects,Micro-/nanofabrication
更新于2025-11-21 11:24:58
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Possibilities of Dry and Lubricated Friction Modification Enabled by Different Ultrashort Laser-Based Surface Structuring Methods
摘要： In this contribution we report on the possibilities of dry and lubricated friction modification introduced by different laser surface texturing methods. We compare the potential of Laser-Induced Periodic Surface Structures and Laser Beam Interference Ablation on 100Cr6 steel in a linear reciprocating ball-on-disc configuration using 100Cr6 steel and tungsten carbide balls with load forces between 50 mN and 1000 mN. For dry friction, we find a possibility to reduce the coefficient of friction and we observe a pronounced direction dependency for surfaces fabricated by Laser Beam Interference Ablation. Furthermore, Laser-Induced Periodic Surface Structures result in a load-dependent friction reduction for lubricated linear reciprocating movements. This work helps to identify the modification behaviour of laser generated micro structures with feature sizes of approximately 1 μm and reveals new possibilities for surface engineering
关键词： lubricated friction,smart surfaces,laser surface texturing,laser beam interference ablation,laser-induced periodic surface structures,dry friction
更新于2025-11-21 11:18:25
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Tailored focal beam shaping and its application in laser material processing
摘要： Besides the optimization of the laser and processing parameters, the adaptation of the focal intensity distribution offers great potential for a well-defined control of laser processing and for improving the processing results. In this paper, different tailored intensity distributions were discussed with respect to their suitability for femtosecond laser material processing on the micro- and nanoscale such as cutting, marking, and the generation of laser-induced periodic surface structures. It was shown by means of laser processing of stainless steel that the numerical simulations for the beam shaping unit are in good agreement with the experimental results. Also, the suitability of the beam shaping device to work with a scanner and an F-theta lens as commonly used for material processing was demonstrated. In this context, the improvement of the machining results was shown experimentally, and a significant reduction of the machining time was achieved.
关键词： laser-induced periodic surface structures,donut,femtosecond laser processing,top-hat,beam shaping
更新于2025-11-21 11:01:37
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AIP Conference Proceedings [Author(s) CURRENT TRENDS IN RENEWABLE AND ALTERNATE ENERGY - Guwahati, India (4–6 December 2018)] - Study of laser induced micro-structural changes in reduced graphene oxide
摘要： Graphene is a promising 2D material for solar cell and energy storage applications. Graphene based materials such as Graphene oxide (GO) are proposed as anode materials for Lithium ion batteries, transparent conducting films, electrodes in polymer based solar cells and many other applications. The present paper discusses laser induced micro structural changes in reduced GO (r-GO) thin films. GO was prepared by Modified Hummers Method, which is easy and low cost method for its large-scale production. The samples were thermally annealed at 400°C to obtain r-GO. To study the influence of laser exposure on micro structure of r-GO, the Raman spectra was recorded after exposure to different time 2, 4, 6 and 8 minutes. Two different laser intensities (95 and 159 KW/cm2) were used to do the same. A blue shift in peak positions and change in ratio of intensity were observed in D and G peaks of Raman spectra after exposure. A total Raman blue shift of about 5 cm-1 is noted in each case, which is due to increased compressive stress between the carbon-carbon bonds. The Raman data was used for calculations of residual stress, grain size and defect density, which changes in gradual pattern with increase in power density and time of exposure. From these observations, it can be concluded that r-GO thin film undergoes micro-structural changes at exposed portion, without affecting rest of the film.
关键词： Graphene,Raman Spectroscopy,Reduced Graphene Oxide,Laser Induced Changes,Graphene Oxide
更新于2025-11-21 11:01:37
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Laser-driven structural transformations in dextran- <i>graft</i> -PNIPAM copolymer/Au nanoparticles hybrid nanosystem: the role of plasmon heating and attractive optical forces
摘要： Laser induced structural transformations in a dextran grafted-poly(N-isopropylacrylamide) copolymer/Au nanoparticles (D-g-PNIPAM/AuNPs) hybrid nanosystem in water have been observed. The laser induced local plasmonic heating of Au NPs leads to Lower Critical Solution Temperature (LCST) phase transition in D-g-PNIPAM/AuNPs macromolecules accompanied by their shrinking and aggregation. The hysteresis non-reversible character of the structural transformation in D-g-PNIPAM/AuNPs system has been observed at the decrease of laser intensity, i.e. the aggregates remains in solution after the turn-off the laser illumination. This is an essential difference comparing to the case of usual heating–cooling cycles when there is no formation of aggregates and structural transformations are reversible. Such a fundamental difference has been rationalized as the result of action of attractive optical forces arising due to the excitation of surface plasmons in Au NPs. The attractive plasmonic forces facilitate the formation of the aggregates and counteract their destruction. The laser induced structural transformations have been found to be very sensitive to matching conditions of the resonance of the laser light with surface plasmon resonance proving the plasmonic nature of observed phenomena.
关键词： Plasmon heating,Attractive optical forces,LCST phase transition,Au nanoparticles,Laser induced structural transformations,Dextran-graft-PNIPAM copolymer
更新于2025-11-19 16:56:42
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Nanostructured Transparent Conductive Electrodes for Applications in Harsh Environments Fabricated via Nanosecond Laser‐Induced Periodic Surface Structures (LIPSS) in Indium–Tin Oxide Films on Glass
摘要： A self-organization phenomenon named laser-induced periodic surface structures (LIPSS) is utilized for pattern formation in indium–tin oxide (ITO) transparent conductive films coated on borosilicate glass. Stripe patterns with periodicities down to 175 nm are created by scanning the focused beam (30 μm spot diameter 1 e?2) of a nanosecond pulsed laser operating at 532 nm wavelength over ITO films. Highly ordered ITO-LIPSS are generated at a pulse duration of 6 ns, pulse frequencies between 100 and 200 kHz, pulse energies around 20 μJ, and laser spot scan speeds in the range of 50–80 mm s?1. Resulting nanopatterns are electrically conductive and feature improved optical transparency as well as stability against strong acids such as hydrochloric acid, sulfuric acid, and even aqua regia. The formation of mixed phases between ITO and silicon is considered to be the origin for the chemical robustness of laser patterned transparent conductive electrodes.
关键词： laser-induced periodic surface structures (LIPSS),laser patterning,self-organization,indium–tin oxide (ITO),transparent conductive films (TCF)
更新于2025-10-22 19:40:53
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Spectroscopic and theoretical studies of potassium sodium l-(+)-tartrate tetrahydrate and l-tartaric acid used as precursors for in situ laser-induced deposition of the catalytically active copper microstructures
摘要： In this work we study the influence of l-(+)-КNaC4H4O6 × 4H2O (KNaT) and l-H2C4H4O6 (H2T) on the complexation processes occurring during in situ laser-induced catalytic destruction of the organic components of the aqueous solutions with formation of the unsaturated hydrocarbons. For that purpose, ATR-FTIR, Raman, IR, and NIR spectroscopy as well as quantum chemical calculations were implemented. It was observed that hydration of T2? anion via carboxylate groups is stronger than that via hydroxyl groups. We also established the changes in the spectral characteristics of the absorption bands corresponding to vibrations of T2?, HT?, and H2T, at solid state-liquid and acid-salt transitions, depending on concentration of the solution components and the [OH?]/[H2T] ratio. Finally, it was shown that ethylene is a main product of the catalytic destruction of the copper tartrate complexes.
关键词： IR,Laser-induced copper deposition,DFT calculations,Tartaric acid,ATR-FTIR,Catalysis,NIR,Raman spectroscopy,Sodium potassium tartrate tetrahydrate
更新于2025-10-22 19:40:53