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

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

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

Effect of laser induced rapid solidification structures on adhesion and bonding characteristics of alumina/silica based oxide to vitreous enamel

The present work is concerned with investigating the effects of high power diode laser (HPDL) radiation on the microstructure of an amalgamated alumina/silica based oxide compound (AOC). The main rapid solidification theories, namely constitutional supercooling and the theory of morphological stability, are used to explain the observed microstructural changes in the AOC resulting from HPDL interaction. Without laser treatment of the AOC surface it was impossible to fire the enamel onto the AOC. However, wetting experiments, using a number of control liquids and the sessile drop technique, revealed that laser treatment of the AOC surface significantly altered the wetting characteristics of the AOC and allowed the enamel to bond to the AOC. Accordingly, HPDL treatment was identified as allowing the vitreous enamel to wet the surface by causing a decrease in the enamel contact angle from 118° to 33°. Moreover, no discernible difference was seen in the change in contact angle across the range of rapid solidification microstructures obtained. The actual incidence of rapid surface resolidification, and not the degree of rapid surface resolidification, was therefore identified as being the primary factor governing changes in contact angle. The bonding mechanisms were identified as being principally owing to van derWaals forces, however, some evidence of chemical bonding was also observed. The work has clearly shown that laser radiation can be used to alter the wetting characteristics of the AOC

On the mechanisms of wetting characteristics modification for selected metallic materials by means of high power diode laser radiation

This work elucidates and analyses the factors responsible for modifications to the wettability characteristics of metallic materials after high power diode laser (HPDL) treatment. It was found that interaction of EN3 and EN8 mild steel with HPDL radiation resulted in the wettability characteristics of the mild steels altering to various degrees depending upon the laser processing parameters. Such changes in the wettability characteristics of the mild steels were found to be due essentially to: (i) modifications to the surface roughness; (ii) changes in the surface O2 content and (iii) the increase in the polar component of the surface energy. All of these factors were seen to influence the wettability characteristics of the mild steels, however, the degree of influence exerted by each was found to differ. Work was therefore conducted to isolate each of these influential factors, thereby allowing the magnitude of their influence to be determined. This analysis revealed that surface roughness was the primary influential factor governing changes in and hence the wettability characteristics of the mild steels. Surface energy, by way of microstructural changes, was also shown to influence to a lesser extent changes in the wettability characteristics, whilst surface O2 content, by way of process gas, was found to play a minor role in inducing changes in the wettability characteristics of the mild steels

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

A comparative study of the surface glaze characteristics of concrete treated with CO2 and high power diode lasers. Part I: glaze characteristics

This present work describes the differences in the characteristics of glazes generated on the ordinary Portland cement (OPC) surface of concrete by means of CO2 and high power diode laser (HPDL) radiation. The value of such an investigation would be to facilitate the hitherto impossible task of generating a durable and long-lasting surface seal on the concrete, thereby extending the life and applications base of the concrete. The basic process phenomena are investigated and the laser effects in terms of glaze morphology, composition, phase and microstructure are presented. Also, the resultant heat affects are analysed and described. The glaze generated after HPDL interaction was found be fully amorphous in nature, whilst the glaze generated after CO2 laser interaction was seen to be of a semi-amorphous structure, with sizeable areas, randomly located within the glaze, displayed a somewhat regular columnar structure. This is proposed to be due to the differing solidification rates occasioned by each laser after treatment as a result of differences in the beam absorption lengths

Wettability characteristics of a modified mild steel with CO2, Nd:YAG, excimer and high power diode lasers

Interaction of CO2, Nd:YAG, excimer and high-power diode laser radiation with the surface of a common mild steel (EN8) was found to effect changes in the wettability characteristics of the steel, namely changes in the measured contact angle of certain liquids. Such changes were identified as being due to modifications to (i) the surface roughness, (ii) changes in the surface oxygen content and (iii) changes in the surface energy of the mild steel. However, it was found that changes in the wettability characteristics of the mild steel were predominantly influenced by the surface roughness. To a much lesser extent surface O2 content is also thought to play a role. The work has shown that the wettability characteristics of the selected mild steel could be controlled and/or modified with laser surface treatment. Moreover, the findings of this work strongly indicate the existence of a relationship between the change of the wetting properties of the mild steel and the laser wavelength

Determination of the absorption length of CO2 and high power diode laser radiation for a high volume alumina-based refractory material

The laser beam absorption lengths of CO2 (10.6 m wavelength) and a high power diode laser (HPDL) (810 nm wavelength ) radiation for an Al2O3/SiO2-based refractory have been determined through the application of Beer-Lambert’s law. The findings revealed marked differences in the absorption lengths despite the material having similar beam absorption coefficients for both lasers. The absorption lengths for the Al2O3/SiO2-based refractory of CO2 and a HPDL radiation were calculated as being 34522 m and 19815 m respectively. Moreover, this method of laser beam absorption length determination, which has hitherto been used predominantly with lasers operated in the pulsed mode, is shown to be valid for use with lasers operated in the continuous wave (CW) mode, depending upon the material being treated