Effects Of Laser Irradiation Time Research Articles

Effect of laser irradiation time on the surface characteristics of a carbon fiber composite

Owing to their unique physical and mechanical properties, carbon fiber reinforced plastics (CFRPs) are finding wide applications in a variety of industries. This broad application necessitates a consideration of the material response in nontraditional environments to evaluate their overall reliability. In the current study, we investigate the time-dependent behavior of unidirectional [0°]6 CFRPs irradiated by a short pulse Nd:YVO4 near-infrared laser for durations ranging between 100 and 500 ms. Post irradiation, the damage on the surface was characterized using optical and electron microscopy as well as optical surface profilometry. Qualitatively, the heat-affected zone (HAZ) was found to primarily consist of an out-of-plane expansion and anisotropic matrix removal with no structural damage to the fibers. The growth in HAZ size is conduction dependent and has a rapid trajectory along the fiber direction and a subdued trajectory along the transverse direction. Further evaluation of the subsurface via x-ray micro-CT showed the HAZ to be surface localized. An analytical heat conduction approach was also used to understand the evolution of surface HAZ with exposure time. This simplified approach was found to adequately capture the shape and growth of the HAZ.

Structural changes and electrical properties of nanowelded multiwalled carbon nanotube junctions.

This study proposes an efficient approach that uses a 1064nm continuous fiber laser to achieve nanoscale welding of crossed multiwalled carbon nanotubes (MWCNTs). We investigate the effects of laser irradiation time (from 1 to 6s) on the structure changes and the welding quality of crossed MWCNTs using a scanning electron microscope, transmission electron microscope, and Raman spectroscopy. The experimental results demonstrate that (1)after 2 or 3s laser irradiation, moderate temperature of MWCNTs can be formed and can cause a higher degree of graphitization and (2)the degree of graphitization and effective contact of nanowelded MWCNT junctions strongly affects its electrical properties.

Implementation of a thermomechanical model to simulate laser heating in shrinkage tissue (effects of wavelength, laser irradiation intensity, and irradiation beam area)

Advancements in the use of laser technology in the medical field have motivated the widespread use of thermal energy to treat a wide variety of diseases and injuries. During laser-induced thermotherapy, the tissue gains heat from laser irradiation and its shape is deformed due to non-uniform temperature distribution. To describe the phenomenon adequately, the mathematical model that considers both heat transfer and mechanical deformation is needed. In this study, the formulation of mathematical model describing coupled heat transfer and mechanical deformation of tissue subjected to laser-induced thermotherapy is numerically implemented. The effects of laser irradiation time, wavelength, laser intensity, laser beam radius and blood perfusion rate on temperature distribution, Von Mises stress distribution, and displacement of the layered skin during laser irradiation are systematically investigated. The values obtained provide an indication of limitations that must be considered in administering laser-induced thermotherapy.

Ablation behavior of Ti6Al4V in laser micro machining process

The effect of laser irradiation time and laser power on the laser ablation behavior of Ti6Al4V is studied experimentally in the study. It is indicated that the contents of the elements are varied with the locations after laser irradiation. The irradiated region by the laser is segmented into two parts (the laser ablation and heat-affected regions) by two circles. The radii of the inner and outer circles increase with the laser irradiation time for all the laser powers and reach to a stable value of the laser beam radius, respectively. Then the ablation mechanism of the Ti6Al4V is revealed according to the Gaussian distribution of laser beam.

Nanocatalyst support of laser-induced photocatalytic degradation of MTBE

This study was undertaken to develop a methodology suitable for the direct removal and degradation of methyl tertiary butyl ether (MTBE) in water using different nano-catalysts supported laser based photo-oxidation process. For this purpose, nano-structured WO3 catalyst was synthesized in our laboratory and its photocatalytic activity for the demineralization of MTBE in water was compared with different catalysts such as ZnO, TiO2, Fe2O3 and NiO using 355 nm laser radiations generated by the third harmonic of Nd: YAG laser. The effect of laser irradiation time, amount of catalysts and pH were also investigated for the optimization of MTBE removal process. For 60 min of laser exposure time, the overall percentage of MTBE degradation was found to be 93%, 89%, 82%, 80% and 71% for WO3, ZnO, Fe2O3, NiO and TiO2, respectively. In addition the photonic efficiencies of different nano-structured catalysts toward degradation of MTBE were estimated, and they were found to follow the trend of WO3 > ZnO > Fe2O3 > NiO > TiO2.

The Study of Thermal Effect in Liquid Crystal Director

The model of thermal effect for liquid crystal director was built. The temperature field of liquid crystal was numerically studied. The effects of laser irradiation time and the crystal size on the thermal effect were analyzed and compared. With the increase of laser irradiation time, the temperature field became stable.

Laser-based photo-oxidative degradation of methyl tertiary-butyl ether (MTBE) using zinc oxide (ZnO) catalyst

Laser-induced photo-catalytic process for the removal of MTBE from water has been investigated in this study. We have studied the laser-based photo-oxidation of MTBE using ZnO semiconductor catalysts at 355 nm laser radiation generated by third harmonic of Nd: YAG laser. The effect of laser irradiation time, laser energy power, catalyst amount and pH parameters were investigated for the efficient removal of MTBE from water using ZnO catalyst. It was found that at pH value of 8, 300 mg of ZnO catalyst, 60 minutes laser irradiation time and 200 mJ of laser energy, delivered best results with maximum degradation of MTBE in water.

Synthesis of composite gold/tin-oxide nanoparticles by nano-soldering

Composite Au–SnO2 nanoparticles (NPs) are synthesized by nano-soldering of pure Au and SnO2 NPs. The multi-step process involves synthesis of pure Au and SnO2 NPs separately by nanosecond pulse laser ablation of pure gold and pure tin targets in deionized water and post-ablation laser heating of mixed solution of Au colloidal and SnO2 colloidal to form nanocomposite. Transmission Electron Microscopy (TEM) and High-Resolution Transmission Electron Microscopy (HRTEM) were used to study the effect of laser irradiation time on morphology of the composite Au–SnO2 NPs. The spherical particles of 4 nm mean size were obtained for 5 min of post-laser heating. Increased mean size and elongated particles were observed on further laser heating. UV–vis spectra of Au–SnO2 nanocomposites show red shift in the plasmon resonance absorption peak and line shape broadening with respect to pure Au NPs. The negative binding energy shift of Au 4f7/2 peak observed in X-ray Photoelectron Spectra (XPS) indicates charge transfer in the nano-soldered Au–SnO2 between gold and tin oxide and formation of soldered nanocomposite.