The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Hasib Mustafa - One of the best experts on this subject based on the ideXlab platform.
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The role of pulse repetition rate on picosecond Pulsed Laser Processing of Zn and Zn-coated steel
Optics & Laser Technology, 2020Co-Authors: Hasib Mustafa, David Thomas Allan Matthews, G.r.b.e. RömerAbstract:Abstract Zinc and zinc-coated steel is processed with a picosecond Laser source at a wavelength of 1030 and 515 nm to investigate the effect of time between consecutive pulses, i.e. pulse repetition rate on the Laser ablation efficiency, in terms of maximum achievable depth of the ablated crater, material removal rate and Processing quality. With increasing pulse repetition rate up to 40 kHz and number of pulses on the same location, material removal rate increases due to heat accumulation, while the maximum achievable depth decreases due to particle shielding for both zinc and zinc coated steel. It was found that, unlike the zinc-coated sample, both material removal rate and achievable depth is enhanced for bulk zinc at high repetition rates, due to a greater degree of heat accumulation than particle shielding. Using a numerical heat flow model, it is shown that the difference between bulk zinc and zinc-coated steel stems from the steel substrate that effectively acts as a heat sink for the absorbed energy in the zinc coating, inhibiting a higher degree of heat accumulation.
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investigation of the ultrashort Pulsed Laser Processing of zinc at 515 nm morphology crystallography and ablation threshold
Materials & Design, 2019Co-Authors: Hasib Mustafa, D T A Matthews, Gert-willem RömerAbstract:Abstract Bulk polycrystalline pure zinc is ablated in air using a picosecond Laser source to perform single pulse and multi-pulse Processing at a wavelength of 515 nm. The geometries and surface morphologies of the resulting craters are determined by confocal Laser scanning microscopy and scanning electron microscopy. Further, the ablation threshold and its corresponding incubation coefficient is determined from the ablated volume for multiple Laser pulses. Two different thermal ablation regimes are identified. The single pulse ablation thresholds are found to equal 0.1 J/cm2 and 0.68 J/cm2 respectively for the two regimes. It is found that the incubation coefficients are larger than unity, indicating material removal becomes energy expensive for multiple pulse Laser irradiation. It is also found that an irradiated area undergoes Laser induced preferred crystal orientation.
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Data on Laser induced preferential crystal (re)orientation by picosecond Laser ablation of zinc in air.
Data in brief, 2019Co-Authors: Hasib Mustafa, David Thomas Allan Matthews, M.p. Aarnts, L. Capuano, Bernardus Gerardus RichardusAbstract:Abstract Laser ablation of zinc is performed with a 6.7 ps Pulsed Laser source to investigate the ablation mechanism and resulting morphology of the irradiated surface. The data shows the changes in crater morphology, as well as chemical composition, for different number of pulses and Laser fluence levels. We observed Laser Induced Preferential Crystal Orientation (LIPCO), as a result of ultra-short Pulsed Laser Processing of Zn at a wavelength of 515 nm. Crystallographic data for other Laser wavelengths, namely 343 and 1030 nm, as well as for Zn coated steel are also provided in support of this observation. Data presented in this article are related to the research article “Investigation of the ultrashort Pulsed Laser Processing of zinc at 515 nm: morphology, crystallography and ablation threshold” [1].
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Short and Ultrashort Pulsed Laser Processing of Zinc: Resolidification Morphology of Ablated Craters
Journal of Laser Micro Nanoengineering, 2018Co-Authors: Hasib Mustafa, David Thomas Allan Matthews, Maziyar Jalaal, N. Ur Rahman, Bernardus Gerardus RichardusAbstract:Laser surface texturing of polycrystalline zinc in bulk form and as galvanised coatings is performed with single, as well as multiple nanosecond and picosecond Laser pulses at a wavelength of 1030 nm. By varying the Laser fluence over a wide range, as well as varying the number of pulses on the same location, thousands of ablated craters can be fabricated and their morphology studied. From the analysis thereof, it can be concluded that, within the boundaries of our experimental (Laser) conditions, ablated craters always show molten features. Depending on the pulse fluence and duration, the final solidifed morphology can feature jets with meso- and micro scale spherical endings, micro rims and protrusions, as well as nano-roughness or a rim around the ablated crater. If the Laser fluence is high, one observes the evidence of surface waves and finger formation, resulted from different types of hydrodynamic instablity. In contrast to nanosecond Laser Processing, it is found that craters formed using picosecond pulses deviate significantly from the Gaussian shape of the Laser intensity distribution at high Laser intensity, due to different temperature gradients in the electronic and lattice subsystems.
Khiam Aik Khor - One of the best experts on this subject based on the ideXlab platform.
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Pulsed Laser Processing of plasma sprayed thermal barrier coatings
Journal of Materials Processing Technology, 1997Co-Authors: Khiam Aik KhorAbstract:The requirements for thermal barrier coatings on turbine blades in jet engines and gas turbines are stringent due to the extreme temperatures and constant thermal cycling that demand a material with excellent thermal shock resistant and thermal insulation properties. Plasma sprayed zirconia alloys have been found to fit this role with some degrees of success. However, the presence of surface pores and a network of inter-connecting micropores within the coatings accentuates the oxidation of the bond coat, Often leading to spallation of the ceramic coat. A Pulsed mode Nd:YAG Laser was used in the present study to process plasma sprayed zirconia alloy coatings. The results indicated the effective melting of the ceramic layer that yielded a shiny surface finish. Scanning electron microscopy observation of the fractured surfaces revealed distinct zones comprised of columnar grains, granular structures similar to that of sintered ceramics and the typical lamellar structure of plasma sprayed ceramic coatings. The crack area and depressions formed were quantified using an image and analyser. The results show that the average crack area in the treated surface increases with increasing Laser energy density. However, the average area of depressions in the treated surface appears to be independent of the Laser energy density input.
D. R. F. West - One of the best experts on this subject based on the ideXlab platform.
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Pulsed Laser Processing of thermal barrier coatings
Journal of Materials Science, 1991Co-Authors: K. Mohammed Jasim, R. D. Rawlings, D. R. F. WestAbstract:Results are reported of the effects of surface melting (sealing) produced by a 1 kW Laser in Pulsed mode on the structure of plasma-sprayed 8wt% yttria partially stabilized zirconia (YPSZ); pulse lengths in the range of 1 to 90msec were used. Smooth surfaces were produced with shallow cracks at values of Laser energy 5 to 40 J. Comparison of the data is made with results obtained by sealing using continuous wave CO_2 Laser Processing.
K. Mohammed Jasim - One of the best experts on this subject based on the ideXlab platform.
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Pulsed Laser Processing of thermal barrier coatings
Journal of Materials Science, 1991Co-Authors: K. Mohammed Jasim, R. D. Rawlings, D. R. F. WestAbstract:Results are reported of the effects of surface melting (sealing) produced by a 1 kW Laser in Pulsed mode on the structure of plasma-sprayed 8wt% yttria partially stabilized zirconia (YPSZ); pulse lengths in the range of 1 to 90msec were used. Smooth surfaces were produced with shallow cracks at values of Laser energy 5 to 40 J. Comparison of the data is made with results obtained by sealing using continuous wave CO_2 Laser Processing.
R. D. Rawlings - One of the best experts on this subject based on the ideXlab platform.
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Pulsed Laser Processing of thermal barrier coatings
Journal of Materials Science, 1991Co-Authors: K. Mohammed Jasim, R. D. Rawlings, D. R. F. WestAbstract:Results are reported of the effects of surface melting (sealing) produced by a 1 kW Laser in Pulsed mode on the structure of plasma-sprayed 8wt% yttria partially stabilized zirconia (YPSZ); pulse lengths in the range of 1 to 90msec were used. Smooth surfaces were produced with shallow cracks at values of Laser energy 5 to 40 J. Comparison of the data is made with results obtained by sealing using continuous wave CO_2 Laser Processing.
