The welding of glass using ultrashort laser pulse has attracted much attention due to its potential applications in many fields such as solar cells, implanted microelectronics, OLED, MEMS, micro sensors and so on. However the optical contact which requires a distance between two glasses less than 100 nm is a very harsh requirements in practical engineering applications. A welding method of glass, which adopts bursts sequences of ultrashort laser pulses oscillated in a small region to react more glass material and release heat stress gently, is presented in this paper. In this way, a stable and mild liquid pool with more melt glass can be achieved to weld glasses with large gap. The maximum gap distance between two glasses is almost 40 μm which is an order of magnitude higher than other methods, and the joint strength of the glass weld with the natural contact gap of 10 μm is up to 64 MPa. At last, the encapsulation experiment of the welding glass with a closed area was carried out to prove that the sample can guarantee good sealing in 100 hours.
Superhydrophobic surfaces with various levels of adhesion have attracted tremendous research attentions due to their potential applications in both academic research and industrial application. Herein, we proposed a rapid and simple method to realize superhydrophobic surfaces with tunable water adhesion by nanosecond pulse laser irradiation on PTFE. The surfaces were composed of nanoscale and microscale square array. By only adjusting the power of the laser scanning, the adhesive forces between the water droplets and the as-prepared PTFE surfaces could be dynamically tuned. The tunable water adhesion was mainly ascribed to the change of micro/nano structure on the as-prepared surfaces which resulted from the change laser power. The as-prepared superhydrophobic surfaces showed tunable water adhesion from ultralow to ultrahigh, on which the static contact angle (SCA) of up to 155.2 ± 1.5°, and the sliding angle (CA) can be controlled from 3 ± 0.5° to > 90°. The tunable adhesive surperhydrophobic surfaces could be achieved by a fast laser scanning speed. Compared with the other laser equipment, the 355nm nanosecond pulse laser had a high single photon energy, high processing speed, low equipment cost and maintenance cost, and showed a huge potential in industrial applications for large-scale fabrication of superhydrophobic surfaces.
Laser cladding (LC), with small heat affected zone (HAZ) and lower dilution, is a promising way to repair and strengthen the rail. However, the traditional LC may lead to the cracking of the coatings and the martensitic transformation in the HAZ; which will threaten the safety of railway transportation. In this work, laser-induction hybrid cladding (LIHC) was innovatively proposed to prepare Ni-based coatings on a fullscale rail. Cracking behaviors, microstructures and mechanical properties of the coatings obtained by LC and LIHC were studied systemically. The results indicate that the cracks appeared in the HAZ of the specimen prepared by LC can be prevented LIHC, and the coatings obtained exhibit higher second dendrite arm spacing (SDAS). However, the martensitic structures with high hardness of HV730-HV900 in the HAZ by LC could not be avoided by LIHC, while the HAZ has lower plasticity and fracture toughness, which may accelerate the extending rate of cracks.
During the iron-making process in blast furnace, the Si content in liquid pig iron was usually used to evaluate the quality of liquid iron and thermal state of blast furnace. None effective method was found for rapid detecting the Si concentration of liquid iron. Laser-induced breakdown spectroscopy (LIBS) is a kind of atomic emission spectrometry technology based on laser ablation. Its obvious advantage is realizing rapid, in-situ, online analysis of element concentration in open air without sample pretreatment. The characteristics of Si in liquid iron were analyzed from the aspect of thermodynamic theory and metallurgical technology. The relationship between Si and C, Mn, S, P or other alloy elements were revealed based on thermodynamic calculation. Subsequently, LIBS was applied on rapid detection of Si of pig iron in this work. During LIBS detection process, several groups of standard pig iron samples were employed in this work to calibrate the Si content in pig iron. The calibration methods including linear, quadratic and cubic internal standard calibration, multivariate linear calibration and partial least squares (PLS) were compared with each other. It revealed that the PLS improved by normalization was the best calibration method for Si detection by LIBS.
The proposed paper illustrates the fabrication and heat treatment of high strength Al-Cu-Mg alloy produced by selective laser melting (SLM) process. Al-Cu-Mg alloy is one of the heat treatable aluminum alloys regarded as difficult to fusion weld. SLM is an additive manufacturing technique through which components are built by selectively melting powder layers with a focused laser beam. The process is characterized by short laser-powder interaction times and localized high heat input, which leads to steep thermal gradients, rapid solidification and fast cooling. In this research, 3D Al-Cu-Mg parts with relative high density of 99.8% are produced by SLM from gas atomized powders. Room temperature tensile tests reveal a remarkable mechanical behavior: the samples show yield and tensile strengths of about 276 MPa and 402 MPa, respectively, along with fracture strain of 6%. The effect of solution treatment on microstructure and related tensile properties is examined and the results demonstrate that the mechanical behavior of the SLMed Al-Cu-Mg samples can be greatly enhanced through proper heat treatment. After T4 solution treatment at 540°C, under the effect of precipitation strengthening, the tensile strength and the yield strength increase to 532 MPa and 338 MPa, respectively, and the elongation increases to 13%.
Laser processing 3-D microstructures inside KDP crystals is an effective way to suppress the transverse stimulated ramam scattering(TSRS)in high power lasers. A simulation study on the transmission characteristics of focused laser inside KDP crystal was carried out to investigate the feasibility of laser processing 3-D microstructures and the effects of laser parameters on the machining accuracy, efficiency and yield. The effects of the peak power density, spot distortion and deviation of laser focus are the main factors on the machining accuracy and crystal fragmentation. The size and shape of the e-ray focus will distort and its peak power density decreases rapidly with the increasing of angle between incident laser and crystal optical axis. The results show that the effect of the e-ray will make the processing efficiency increase more than double when the angle is less than 15°, and can be neglected in the low-energy or easily causes crystal fragmentation in high-energy when the angle is greater than 30°, in this case the e-ray should be shielded. The related simulated results have an important engineering value on increasing the accuracy
of laser micromachining birefringent materials.
Improved spectral resolutions were achieved in laser-induced breakdown spectroscopy (LIBS) through generation of
high-temperature and low-density plasmas. A first pulse from a KrF excimer laser was used to produce particles by
perpendicularly irradiating targets in air. A second pulse from a 532 nm Nd:YAG laser was introduced parallel to the
sample surface to reablate the particles. Optical scattering from the first-pulse plasmas was imaged to elucidate particle
formation in the plasmas. Narrower line widths (full width at half maximums: FWHMs) and weaker self-absorption were
observed from time-integrated LIBS spectra. Estimation of plasma temperatures and densities indicates that high
temperature and low density can be achieved simultaneously in plasmas to improve LIBS resolutions.
A pair of permanent magnets and an aluminum hemispherical cavity (diameter: 11.1 mm) were both used to confine
plasmas produced by chromium targets in air using a KrF excimer laser in laser-induced breakdown spectroscopy. A
significant enhancement factor of about 24 in the emission intensity of Cr lines was acquired at a laser fluence of 6.2
J/cm2 using the hybrid confinement. In comparison, an enhancement factor of only about 12 was obtained with just a
cavity. The Si plasmas, however, were not influenced by the presence of magnets as Si is hard to ionize and, hence, has
less free electrons and positive ions. The hybrid confinement mechanism is discussed using shock wave theory in the
presence of a magnetic field.
During the last decade, diode-pumped solid state (DPSS) lasers have been gained wider application in semiconductor
and electronics industry due to the advantages of high efficiency, low operating cost, good beam quality and flexibility
as well as miniature size. Now, 355nm DPSS UV laser has increasingly been adopted in micro-processing application for
both semiconductor and electronics industry where both micro-processing quality and precision of high-density, multilayer
and multi-material components are in a strong demand. Our works on typical applications of 355nm DPSS UV
laser micro-processing both semiconducting and electronic materials have been introduced in this paper, including
drilling (200μm blind holes in 4-layer FPC), cutting (coverlay, CCL, FPC, 0.6mm silicon), and etching (ITO-glass). The
effects of the processing parameters (pulse energy, frequency, peak power, scanning speed and focal plane position as
well as processing modes) on the micro-processing quality and precision have been investigated and analyzed. By
optimizing the processing parameters, the blind drilling depth to the second copper layer can be controlled accurately and
the roughness Sq 1.33μm on the second copper surface can be achieved. A high quality and size precision (position
precision 20μm) cutting edge without charring, burrs and micro-cracks as well as with very small heat affected zone
(HAZ) can be also obtained. When etching function film, the etching width is less than 20 micron, and the etching speed
is more than 500mm/s.
In this study, we described the scanning area limitation (SAL) speciality in laser flying marking and defined maximum markable time and maximum marking offset (MMO) for analyzing the effect of SAL on flying marking process. We presented maximum flying velocity (MFV) to evaluate the performance of a laser marking system and investigate the factors, including the the length of marking graphics in the moving direction and the marking order of graphics objects, which will impact the maximum flying velocity very much. Transverse and vertical directions of graphics entering into the scanning area and three object scanning path algorithms, the all-entered-marking, first-entering-first-marking (FEFM), and rowed-FEFM were analyzed and compared, and MMO and MFV were calculated using these algorithms. Experimental MFV results with different algorithms satisfied theoretical calculations very well, and it was shown that there is a best MFV performance when using the FEFM scanning path algorithm in the transverse moving direction.
SiO2-TiO2 planar optical waveguides are fabricated on silicon wafer substrate by dip-coating technique with the
Sol-Gel solutions, based on which the stripe optical waveguides are patterned by laser direct writing of the Sol-Gel films
using an Ytterbium fiber laser and followed by chemical etching. The effects of the laser processing parameters on the
microstructure of the core layer films are investigated. The relative chemical etching rates of the non-irradiated area in
Sol-Gel films that are haeted at different temperature are characterized. The optical fields and propagation losses of the
optical waveguides at the wavelength of 1550 nm are characterized by multi-channel fiber/waveguides coupling system.
The experimental results demonstrate that the composition, the post heat treatment temperature and laser power density
have a big effect on the widths of the stripe optical waveguides, and the minimum widths about 25 μm can be fabricated
with the suitable parameters. The core layer of the planar optical waveguides as received by Sol-Gel method is loose in
structure, and a shrinkage concave groove forms in the laser irradiated area. The microstructure and forming mechanisms
of the stripe waveguides by laser direct writing Sol-Gel films are discussed. The minimum propagation loss of the
fabricated stripe waveguides is about 1.77dB/cm at 1550nm. Better results are expected by improving the film
composition and laser processing parameters further.
A new cladding approach based on laser-induction hybrid technique on flat sheets is presented in this paper. Coating is produced by means of 5kw cw CO2 laser equipped with 100kw high frequent inductor, and the experiments set-up, involving a special machining-head, which can provide laser-induction hybrid heat resources simultaneously. The formation of thick NiCrSiB coating on a steel substrate by off-axial powder feeding is studied from an experimental point of view. A substrate melting energy model is developed to describe the energy relationship between laser-induction hybrid cladding and laser cladding alone quantitatively. By comparing the experimental results with the calculational ones, it is shown that the tendency of fusion zone height of theoretical calculation is in agreement with that of tests in laser-induction hybrid cladding. Via analyses and tests, the conclusions can be lead to that the fusion zone height can be increased easily and the good bond of cladding track can be achieved within wide cladding processing window in laser-induction hybrid processing. It shows that the induction heating has an obvious effect on substrate melting and metallurgical bond.
The microstructure and mechanical properties of interface between GH4133 substrate and laser cladding were
investigated experimentally. It was found that the process variables for laser cladding can result in the formation of
incomplete fusion between the cladding layer and substrate or reheat cracking along the grain boundary in the coarse
grain zone of the heat-affected zone (HAZ) during ageing treatment. The SEM and EDS analysis demonstrates that the
chemical compositions in the crack and substrate are very similar and there is not precipitation in the crack. Therefore,
the reheat cracking has nothing to do with liquid film on the grain boundaries, the possible cause of the formation of
reheat cracking is that the plastic deformation caused by residual stress formed during thermal cycle of laser cladding
concentrates on the coarse grain boundary in HAZ because precipitations precipitating in the grain during ageing
treatment strengthen grain. The laser cladding layer with integrated melt interface and without reheat cracking can be
obtained by optimizing laser power, scanning velocity and powder thickness. The experimental results of microhardness
have shown that the microhardness of laser cladding layer is the same with that of GH4133 base metal after ageing
treatment, thus the properties of the clad layer and the substrate are homogeneous.
Recently, the study on the direct laser fabrication by CO2 laser is more than that by Nd: YAG laser. The primary goal of
this research is to study technics and structure performance of metal component of laser rapid prototyping based on Nd:
YAG laser and coaxial powder feeder. The experimental equipments consist of ROFIN 1.1KW YAG laser, a 3-axis CNC
table, a coaxial powder nozzle and a powder recycler. Firstly, the single-track cladding experiment was conducted; the
effect of laser power, scan velocity and Z-axis increment on the single-track cladding shape was studied with different
processing parameters. Secondly, some tensile samples, which were built by direct laser fabrication (DLF) using the best
processing parameters, were analyzed by tensile experiment, SEM and EDS. The effect of Nd: YAG laser rapid
prototyping technology on the structure and performance was studied and compared with the results of CO2 laser
fabrication on the approximate condition. Lastly, some molding samples built by Nd: YAG laser were shown in the
paper. In conclusion, the technics parameters have large effect on the molding result; the key technology of laser rapid
prototyping is searching the best process parameters. The tensile samples built by Nd: YAG laser have the features of
high intensity, fine crystalline grains and orientated solidification structure; moreover, the orientations of laser scanning
have influence on tensile performance. Compared with the CO2 laser rapid prototyping, its tensile strength is higher and
its plasticity is lower.
A laser flying marking system with a galvanometer scanner could be widely used as a workhorse because the moving speed of product on the workline would not be affected while being marked. A laser flying marking system, with high-speed galvanometer scanners, was set up. Two kinds of marking effects, vector style and matrix style, were realized in the system. Different motion-tracing methods, including a closed-loop feedback tracing mode and an open-loop computing tracing mode, were studied and utilized in the control software. Experimental results show that the system using the closed-loop feedback motion-tracing method has more adaptability for variable-speed applications.
Infrared thermograph technology in the research of laser-matter interaction was discussed. The formation of molten pool and heat transfer and matter transfer in laser repairing cracks of components were investigated using infrared thermal imaging system. Because the software system of HWRX-3 thermovision is not compatible with the present computer and operation system, we discussed several methods, where the compatibility has been solved and the image processing system can be transformed to windows operation system by the redesign software. The friendly user interface and very high visibility of the optimized software have been testified during laser repairing cracks of components processing. One practical method of digital process for the investigation on heat transfer and matter transfer in laser repairing cracks of components has been developed.
This report presented a detailed study on parameters and mechanisms of cleaning rubber layer from a tire mold surface with pulse laser. The results demonstrated that pulse laser can remove rubber layer completely under proper parameters, and there exist cleaning thresholds and damage threshold in laser cleaning. When the laser fluences are in the ranges between the initiated cleaning threshold and complete cleaning threshold, cleaning percentage of the mold surface increases with the increasing of laser fluences. When the laser fluences are in the ranges between complete cleaning threshold and damage threshold, cleaning percentage keeps up 100% and there is no damage on substrate surface. Two mechanisms for laser cleaning rubber layer are suggested: one is the combustion and vaporization of upper rubber layer resulted by high temperature of laser irradiation, the other is particles splattering due to the vibration of deep rubber layer as well as thermal shock action by laser pulse.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.