RESUMEN
Laser micromelting (LMM) technology allows for the remelting of pre-positioned coatings on the surface of a specimen to form a metallurgical bond with the substrate material, significantly improving the coating's film-base bond. However, the high energy input from the laser modification process can cause severe element diffusion, rendering the coating susceptible to deformation and cracking. This can be mitigated by controlling the laser power, scanning speed, and offset of the LMM process. The temperature and stress fields of the samples in the LMM process were analyzed via finite element simulation. The effects of the LMM process parameters on the coating morphology were analyzed in conjunction with experiments. The results indicated that the laser power significantly affected the morphology of the coating after remelting, and a higher scanning speed was more likely to cause the coating to accumulate stress. Additionally, a smaller offset inhibited crack generation. At a laser power of 30 W, a scanning speed of 1200 mm/min, and a scanning spacing of 0.035 mm, the surface of the coating had no obvious defects and was relatively flat, and the adhesion and corrosion resistance were significantly improved. This study provides valuable guidance for improving the preparation of micron-sized protective coatings on Zr alloy surfaces.
RESUMEN
Laser process technology provides a feasible method for directly manufacturing surface-metallized carbon fiber composites (CFCs); however, the laser's process parameters strongly influence on the adhesion strength between electroless copper and CFCs. Here, a nanosecond ultraviolet laser was used to fabricate electroless copper on the surface of CFCs. In order to achieve good adhesion strength, four key process parameters, namely, the laser power, scanning line interval, scanning speed, and pulse frequency, were optimized experimentally using response surface methodology, and a central composite design was utilized to design the experiments. An analysis of variance was conducted to evaluate the adequacy and significance of the developed regression model. Also, the effect of the process parameters on the adhesion strength was determined. The numerical analysis indicated that the optimized laser power, scanning line interval, scanning speed, and pulse frequency were 5.5 W, 48.2 µm, 834.0 mm/s, and 69.5 kHz, respectively. A validation test confirmed that the predicted results were consistent with the actual values; thus, the developed mathematical model can adequately predict responses within the limits of the laser process parameters being used.
RESUMEN
Pulsed laser ablation in liquid, used for nanoparticle synthesis from solid bulk metal targets (a top-down approach), has been a hot topic of research in the past few decades. It is a highly efficient and 'green' fabrication method for producing pure, stable, non-toxic (ligand-free), colloidal nanoparticles, which is often challenging using traditional chemical methods. Due to the short time scale interaction between the laser pulses and the target, it is difficult to achieve complete control on the physical characteristics of metallic nanoparticles. Laser process parameters, liquid environment, and external fields vastly effect the shape and structure of nanoparticles for targeted applications. Past reviews on pulsed laser ablation have focused extensively on synthesising different materials using this technique but little attention has been given to explaining the dependency aspect of the process parameters in fine-tuning the nanoparticle characteristics. In this study, we reviewed the state of the art literature available on this technique, which can help the scientific community develop a comprehensive understanding with special insights into the laser ablation mechanism. We further examined the importance of these process parameters in improving the ablation rate and productivity and analysed the morphology, size distribution, and structure of the obtained nanoparticles. Finally, the challenges faced in nanoparticle research and prospects are presented.