An analysis of the beam interaction characteristics of selected lasers with an alpha-alumina bioceramic

Certain differences between the interaction characteristics of a CO2 laser, a Nd:YAG laser and a high power diode laser (HPDL) with an alpha-alumina bioceramic have been investigated. For each laser the fluence threshold values at which significant material removal occurs were found graphically. Through the implementation of a derivative of Beer-Lambert’s law, the laser beam absorption lengths were calculated along with the thermal loading values. An examination of the laser induced meltpool propagation in the alpha-alumina revealed good agreement with the Stefan solution to the heat diffusion equation for the lasers. Absorptivity measurements revealed that there was no correlation between the actual absorptivity of the alpha-alumina and the absorption length for each of the three lasers on account of the absorptivity measurements being similar for each laser. However, differences in the depth of melting experienced by the alpha-alumina meant that it is reasonable to assume that absorption length is the principal influence on the melt depth

On the potential role of the high power diode laser in modern dentistry

It is being increasingly realised by many that there is much to be said for the more extensive deployment of lasers to perform a wide variety of tasks. Within the fields of science, engineering and medicine, lasers have, and still are replacing existing equipment and tools as well as, perhaps more importantly, being used to carry out unique functions that were hitherto not possible. Moreover, this evolutionary cycle has advanced a stage further with technologically mature lasers now being superseded by more contemporary lasers. This is particularly true of the contemporary diode laser

A high power diode laser (HPDL)-based technique for the bonding of composite patches to aluminium alloys on various military aircraft

A rapid, effective and repeatable technique for repairing the damaged skins of various military aircraft, both fixed and rotary winged, using high power diode laser (HPDL) radiation is described herein. The HPDL beam was traversed across the surface of an APC-2 repair patch, thereby melting a thermoplastic adhesive placed in between the repair patch and an Alclad substrate, consequently bonding the repair patch to the Alclad substrate. When subjected to single lap shear tests, the shear strength of the bond generated with the HPDL radiation was 47.8 ± 4.7 MPa, compared to 32.4 ± 3.7 MPa for the induction welded samples. When subjected to the Boeing wedge test, the HPDL samples had a 1 hour crack growth rate that was rated as very good (1.9 ± 0.5 mm/h); for the induction welded samples the 1 hour crack growth rate that was rated as good (2.7 ± 1.2 mm/h). Of great significance was processing time achieved with the HPDL, which was reduced from 11.75 minutes when employing induction welding to 2.75 minutes with the HPDL. Moreover, the use of HPDL radiation has been shown in this work to be an effective means for bonding that is superior to its contemporary counterparts

Laser cleaning of the output window in a laser ignition system for gas turbines

Laser ignition (LI) of both liquid fuels and gaseous combustible mixtures in gas turbines offers the potential for reduced emissions and increased reliability. During the combustion process, carbon and other by-products accumulate on the walls of the combustion chamber. For laser based ignition systems, this could potentially reduce the transmissive properties of the output window required for transmission of the laser radiation into the combustion chamber. Presented in this paper is an empirical study into the laser cleaning of an output window for the removal of accumulated carbon prior to laser ignition, with the mechanism of removal discussed

The characteristics of a high-power diode laser fired enamel coating on a carbon steel

Significant changes to the wettability characteristics of a common engineering carbon steel(EN8) were effected after high power diode laser (HPDL) surface treatment. These modifications havebeen investigated in terms of the changes in the surface roughness of the steel, the presence of any surface melting, the polar component of the steel surface energy and the relative surface O2 content of the steel. The morphological and wetting characteristics of the mild steel and the enamel were determined using optical microscopy, scanning electron microscopy, X-ray photoemission spectroscopy, energy-dispersive X-ray analysis and wetting experiments by the sessile drop technique. This work has shown that HPDL radiation can be used to alter the wetting characteristics of carbon steel so as to facilitate improved enamelling. Furthermore, standard mechanical, physical and chemical testing of the HPDL-fired enamel glaze revealed the glaze to possess similar properties to those of a conventionally fired enamel glaze in terms of bond strength, rupture /impact strength, wear and corrosion resistance. Such similar performance can be attributed to the two glazes possessing the same mechanical properties and similar amorphous structure, despite their very different firing techniques

Finite element analysis of temperature distribution using ABAQUS for a laser based tile grout sealing process

Interaction of CO2, Nd:YAG, excimer and high power diode laser (HPDL) radiation with the surface of an Al2O3/SiO2 based ceramic was found to effect significant changes in the wettability characteristics of the material. It was observed that interaction with CO2, Nd:YAG and HPDL radiation reduced the enamel contact angle from 1180 to 310, 340 and 330 respectively. In contrast, interaction with excimer laser radiation resulted an increase in the contact angle to 1210. Such changes were identified as being due to: (i) the melting and partial vitrification of the Al2O3/SiO2 based ceramic surface as a result of interaction with CO2, Nd:YAG HPDL radiation. (ii) the surface roughness of the Al2O3/SiO2 based ceramic increasing after interaction with excimer laser radiation. (iii) the surface oxygen content of the Al2O3/SiO2 based ceramic increasing after interaction with CO2, Nd:YAG and HPDL radiation. The work has shown that the wettability characteristics of the Al2O3/SiO2 based ceramic could be controlled and/or modified with laser surface treatment. In particular, whether the laser radiation had the propensity to cause surface melting. However, a wavelength dependance of the change of the wetting properties could not be deduced from the findings of this work

Surface glazing of concrete using a 2.5 kW high power diode lase

Interaction of CO2, Nd:YAG, excimer and high power diode laser (HPDL) radiation with the surface of an Al2O3/SiO2 based ceramic was found to affect significant changes in the wettability characteristics of the material. It was observed that interaction with CO2, Nd:YAG and HPDL radiation reduced the enamel contact angle from 1180 to 310, 340 and 330 respectively. In contrast, interaction with excimer laser radiation resulted an increase in the contact angle to 1210. Such changes were identified as being due to: (i) the melting and partial vitrification of the Al2O3/SiO2 based ceramic surface as a result of interaction with CO2, Nd:YAG HPDL radiation. (ii) the surface roughness of the Al2O3/SiO2 based ceramic increasing after interaction with excimer laser radiation. (iii) the relative surface oxygen content of the Al2O3/SiO2 based ceramic increasing after interaction with CO2, Nd:YAG and HPDL radiation. The work has shown that the wettability characteristics of the Al2O3/SiO2 based ceramic could be controlled and/or modified with laser surface treatment. Moreover, it was found that changes in the wettability characteristics of the Al2O3/SiO2 based ceramic are related to the effects of laser wavelength, that is whether the wavelength of the laser radiation has the propensity to cause surface melting

Generic parameters governing the biofunctionality of laser surface engineered nylon 6,6

On account of an ever increasing demand on medicine there is a need and a drive by the biomedical industry to develop robust and predictable implant technology. This paper gives an account of the implementation of CO2 and KrF excimer laser systems to modulate the biofunctionality of nylon 6,6 in terms of osteoblast cell response. There were correlative trends between the cell response, contact angle, polar component and surface oxygen content for the whole area irradiative processed samples. Thus, allowing one to identify the potential for this technology in regenerative medicine. However, no strong correlations were determined for the laser-induced patterned samples which can be attributed to the likely mixed-state wetting regime. Through analytical analysis, governing equations are discussed, showing how different parameters can be used to predict the wettability of, and biological cell response to, laser surface engineered nylon 6,6

The effects of process gas type on the surface condition of high power diode laser treated ordinary Portland cement

This paper examines the effects of using O2, Ar and He process gasses during the treatment of the ordinary Portland cement (OPC) surface of concrete with a high power diode laser (HPDL). The study revealed that, depending on the shield gas used, distinct difference existed in the surface condition of the concrete after HPDL treatment. In particular, the use of O2 as the shield gas was seen to result in glazes with far fewer microcracks and porosities than those generated with either Ar or He shield gases. Such differences were found to be due to the smaller O2 gas molecules dissolving molecularly into the open structure of the HPDL generated glaze on the OPC surface of concrete and react with the glass network to increase the fluidity of the melt. This is turn was also seen to affect the cooling rate and therefore the tendency to generate microcracks

Wettability characteristics of polyethylene (PE) modified with CO2, Nd:YAG, excimer and high power diode lasers

Interaction of CO2, Nd:YAG, excimer and high power diode laser (HPDL) radiation with the surface of the bio-material, polyethylene (PE), was found to effect varying degrees of change to the wettability characteristics of the material depending upon the laser used. It was observed that interaction with CO2, Nd:YAG and HPDL effected very little change to wettability characteristics of the PE. In contrast, interaction of the PE with excimer laser radiation resulted an increase in a marked improvement in the wettability characteristics. After excimer laser treatment the surface O2 content was found to have increased and the material was seen to be more polar in nature, resulting in a significant increase in the wettability characteristics. The work has shown that the wettability characteristics of the PE could be controlled and/or modified with laser surface treatment. However, a wavelength dependence of the change of the wetting properties could not be deduced from the findings of this work