Papers by Keyword: Nd-YAG Laser

Abstract: Abstract. Laser ablation of a silver target immersed in distilled water utilizing Nd: YAG laser with wavelengths of 532nm,1064nm, and 1320nm was carried out to fabricate silver nanoparticles. The synthesis of Ag NPs was carried out using various laser energy (200-1000 mJ) and different pulses (200-1000 pulse). Optical properties for the Ag nanoparticles solution were tested using UV-Visible spectrum, while the morphological properties for the Ag-nanoparticles solution after deposited on glass were tested using the atomic force microscope (AFM). The results showed that the synthesis of the Ag-nanoparticles using pulsed laser ablation in liquid (PLAL) (water) gives nanoparticles with homogeneous grain distribution and uniform surface roughness. It was found that the absorption peaks of Ag NPs increase by increasing the number of pulses shoot for the same laser wavelength and laser energy, and the reported maximum value of absorption peak is 0.363 when using 1000 pulses shoot. AFM results showed that the average diameter of the Ag NPs prepared by PLAL increases with increasing the laser wavelength. However, when using laser wavelengths of 1320nm,1064nm, and 532nm, the resulted average diameter of silver nanoparticles will be 55.38nm, 34.18nm, and 30.3nm, respectively. Finally, the average surface roughness of the Ag NPs prepared by PLAL increased with increasing the laser wavelength. The obtained average surface roughness of silver nanoparticles when using wavelengths of 1320nm,1064nm, and 532nm were 2.75nm, 1.19nm, and1.06nm, respectively.

Abstract: This article presents some results of laser processing of materials, used for the construction of microsystems and micro-sensors, e.g. Si, Al₂O₃ and zirconia ceramics. The necessity of faithful reproducing the geometry and dimensions in the micro-scale puts specific requirements for laser machining process. Laser micro-technologies must be conducted under conditions which ensure the perfect guidance of a well-focused laser beam, scanning at a suitable speed, and the laser pulse duration with proper repetition frequency. The amount of absorbed energy depends on wavelength of laser radiation and kind of material, which also influence on this process. All these conditions should take into account the need to maintain a small heat affected zone (HAZ). This guarantees keeping the true reproduction of micro-shapes and cutting edges with a different angle of lines even in micro-scale details. The present work confirms the possibility of using laser technology for such applications.

Abstract: Laser cladding technology was adopted to fabricate hydroxyapatite(HAP) and calcium phosphate compound coating according to the feature that a metallurgical bonding can be formed by laser cladding process. Compared with CO₂ laser, Nd-YAG laser has different wavelength(the former is 1.06μm and the latter is 10.06μm). Metal and ceramic material has quite different absorbance ability towards them and thus they can generate different laser cladding products by these two laser surface processings with different wavelength. This paper presents a new process and mechanism analysis to obtain bioceramic composite coating on Ti6Al4V substrate by Nd-YAG laser cladding. A bioceramic composite coating including HAP，Ca₂P₂O₇，Ca₃(PO₄)₂ and calcium titanates and was successfully obtained by Nd-YAG laser cladding with pre-depositing mixed powders of CaHPO₄•2H₂O and CaCO₃ directly on Ti6Al4V substrate. Nd-YAG laser transmits mixed powders of CaHPO₄•2H₂O and CaCO₃ and the laser power is absorbed by Ti6Al4V substrate to produce a thin layer of molten region. There are mainly two kinds of chemical reaction systems in the coating during laser cladding processing. When CaHPO₄•2H₂O and CaCO₃ react together, they make calcium phosphate bioceramic products; The microstructure of the bioceramic composite coating is even and minute because of the rapid solidification in laser processing. A chemical metallergical bonding is formed between the boceramic composite coating and Ti6Al4V substrate. It can also be expected that Nd-YAG laser cladding technology can be used as a further modification procedure to enhance HAp/metal interface property.

Abstract: Laser Induced Plasma Assisted Ablation (LIPAA) has been used to carry out back side dry etching/ablation of different optical glasses under vacuum. It is observed that etching depth increases with decrease in target-substrate gap and becomes maximum (50 μm) at zero gap size for steel-quartz pair. The maximum ablation depth for brass-quartz pair was 25 μm. The effects of laser power on etching depth and laser scan speed has also been reported.

Abstract: The optimization of chemical vapor deposition synthesis conditions for multiwall carbon nanotubes (MWCNTs) was experimentally investigated. Carbon nanotubes were grown on cobalt substrate thicknesses of 20, 100 and 1000 nm at 700 and 900 0C with 2 replications. The configuration and morphology of the carbon nanotubes were investigated by scanning electron microscope and Fourier transform raman spectrometer, respectively. The tendency of the parameters was evaluated by statistical design of experiment. Observations on samples produced under our optimised production process, showed that a large number of MWCNTs bundles were produced. Diameter of MWCNTs bundles ranges between 30 and 100 nm throughout the samples. From the variance analysis of the Raman spectra we observe that the thickness of cobalt and temperature of synthesis are highly significant in which the coherence length and innermost diameter increase for either the thickness increases or the temperature decreases.

Abstract: In order to reduce the thermal influences in laser machining of sapphire surface, effects of a short-pulse ultra-violet laser were investigated. For the UV laser, the Fifth harmonic generation (Fifth HG) wave of an Nd:YAG laser (wavelength:213nm) was utilized. Significant reduction of thermal damages on the surface was demonstrated with the Fifth HG pulses compared to longer wavelengths of the Nd:YAG laser. It was shown that the control of depth of bottom surface with reduced thermal influences was possible in lower fluence cases(less than 40 J/cm2) with a homogenized beam and smooth surface roughness Ra < 200nm was obtainable.