Papers by Keyword: Pulse Laser

Abstract: Abstrac. In the present work, gold nanoparticle (Au NPs) was synthesis by pulsed laser ablation (PLA) by using Q-switched, (Nd: YAG) (E=80mJ) (λ=532,1064nm) and Number of pulses (500)pulse of the gold metal target in deionized water. The optical properties were studied with a UV-vis spectrophotometer which tests the absorbance spectra and comparison of the generated nanoparticles solution. atomic force microscope (AFM) results show that the grain size increase by decreasing wavelength. The optical limiter of the resulting colloidal solution was studied.

Abstract: In this paper, the ablated microstructures on copper film affected by ultraviolet nanosecond pulse laser are presented. The experimental system was consisted of two lasers, optics and controlling electronics. A 3000mW, 355nm Q-switched ultraviolet lasers was used to the micro-polishing experiments in the work. The repetition rate of the ultraviolet pulse laser is from single-shot to 100kHz, and the pulse width is less than 40ns. The sample used in experiment is copper film (200 nm) sputtered on glass. A series of experiments at different laser parameters and speed of work platform are done. The ablating experiments are also carried out on focusing and defocusing application in the laser direct writer. The results were analyzed.

Abstract: The Fe-based amorphous composite coatings were prepared by pulse laser cladding method. The amorphous powder with the size ranging from 100 to 200 meshes was cladded on the low carbon steel plate,and the nominal composition of the powder was (wt.%) Cr:14.95, Mo:25.7, B:1.24, C:3.45, Y:3.40, Fe:51.29. The microstructure, phase composition and hardness were characterized by XRD, SEM, DSC and semi-automatic Vickers hardness tester in this study, respectively. The results show that the coating which is composed of amorphous and nanocrystal phases has the dense structure and metallurgical bonding with the substrate. The hardness of coatings was about 5 times higher than that of the substrate. With the increase of cladding layer, the average hardness of coating showed an increasing trend, and the intrinsic mechanism was discussed.

Abstract: Laser assisted machining (LAM) is one important solution for machining difficult-to-machine materials. The heat transfer model of quasi steady state in laser assisted micro machining is built, and the simulation software for temperature distribution measurement is developed based on MATLAB. The simulated temperature distribution of the ZrO₂ ceramic heated by pulse laser shows a good agreement of tendency with the corresponding experimental results through the infrared temperature measurement method, while the simulated temperature is consistently overestimated. This difference maybe results from the neglect of the heat loss caused by the heat radiation and the heat convection in the model. The proposed model in this paper could provide reference for the selection of optimal process parameters and improve the machining quality, which are closely related to the temperature distribution.

Abstract: The thermal effect caused by absorbing inclusion irradiated by pulse laser is affected by size of inclusions, pulse duration, repetition interval and number of pulse laser. The temperature both in the center of inclusion and the interface between inclusion and dielectric increases firstly with the increase of the size of inclusion, then trends to a constant value when the size is over the critical radius. Pulse duration and repetition interval of pulse change the energy acumulation in inclusion then have influence on the peak temperature in the center and interface. The temperature fluctuates periodically but the overall assumes the trend of increase.

Abstract: The targets are micron-sized TiO₂ powders and micron-sized Ag powders, TiO₂@Ag nanocomposite particles with core-shell structure were synthesized by pulsed laser gas phase evaporation-liquid phase collecting method. The morphology, structure and synthesis mechanism of the samples were studied by means of transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), and X-ray diffraction technique (XRD). The results show that the pure TiO₂ nanoparticles sol was firstly prepared as liquid phase collecting system using gas phase evaporation-liquid phase collecting method; then, the target was changed using Ag, and TiO₂ @ Ag nanocomposite particles with core-shell structure, which are spherical or ellipsoidal, were successfully synthesized under certain conditions of laser synthesis parameters; the diameters of most TiO₂@Ag nanocomposite particles covering synthesized after 2h range from 15nm to 35nm, the diameters of most TiO₂ @Ag nanocomposite particles covering synthesized after 4h range from 25nm to 50nm, and the size of nanocomposite particles increases with the increase of covering synthesis time; TiO₂ nanoparticles synthesized previously in liquid phase function as crystallized cores, while Ag atoms and their clusters are adsorbed to TiO₂ surfaces and surround the surfaces to form TiO₂ @ Ag nanocomposite particles.

Abstract: Texturing processing experiment of SiC and YG8 surface was done by using lamp-pumped YAG-T50 laser marking machine and the depth of groove and the surface roughness was measured by using PS50 measurement which is non-contact. Through experiment, process parameters, such as effective vector step, effective vector step delay, Q frequency, laser current, effecting on the quality of the micro-shape processing were been researched. The experimental results show that, when effective vector step delay or laser current increases, the depth of the helical groove increases;while effective vector step or the Q frequency increases, the depth decreases;the surface roughness value decreases along with increasing of effective vector step delay Q frequency and laser current, increasing when effective vector step increases.

Abstract: An approach of detecting ultrasonic signals generated by pulsed laser is studied. The influence factors are analyzed on the received signals. Based on pulsed laser generating ultrasonic, a metal plate is used as a detected target. The ultrasonic is induced by way of combining high-power pulsed laser with optical attenuation unit, and then received by a piezoelectric ultrasonic transducer. The difference between ablation regime and thermo elasticity with different pulsed laser input parameters are compared. Moreover the ultrasonic propagation under different thickness of metal plate and the impacts of relative position of stimulating point and detection point on ultrasonic signal is researched. The validity of this method is demonstrated through these experiments and the laser input parameters are determined when in thermo elasticity.

Abstract: Bonding strength of the interface of film-substratum is an important factor and key problem that influence the reliability and usage of film-substratum system. The new technology of pulsed-laser shock detection method which analyzes the mechanism and mathematical model of film separation under the action of pulsed-laser shock,. With the example of measuring the adhesion strength of TiN/SKD11 film system, the surface was respectively impacted with pulsed-laser at the range of 650~1000mJ. To observe the surface topography of Impact points by scanning electron microscope, and to identify TiN film failure threshold by the reflected signal detection. By analyzing the experimental result, it was suggested that film/substrate interfacial adhesion strength was 4.954GW/cm2.

Abstract: The objective of this work was evaluating the creep resistance of the Ti-6Al-4V alloy with superficial treatment of pulsed Nd:YAG laser and ceramic coating in creep test of Ti-6Al-4V alloy. It was used Ti-6Al-4V alloy as cylindrical bars under forged and annealing of 190oC by 6 hours condition and cooled by air. The Ti-6Al-4V alloy after the superficial treatment of pulsed Nd:YAG laser and ceramic coating was submitted to creep tests at 600°C and 125 at 319 MPa, under constant load mode. In the Nd:YAG pulsed laser treatment was used an environment of 40 % N and 60 % Ar, with 2.1 W of power and 10 m/s of speed. Yttria (8 wt.%) stabilized zirconia (YSZ) with a CoNiCrAlY bond coat was atmospherically plasma sprayed on Ti-6Al-4V substrates by Sulzer Metco Type 9 MB. The obtained results suggest the laser treatment on Ti-6Al-4V alloy improved its creep resistance.