The effects of high power diode laser radiation on the wettability, adhesion and bonding characteristics of an alumina/silica-based oxide and vitreous enamel

An amalgamated alumina/silica-based oxide compound (AOC) was surface treated using a 60 W high power diode laser (HPDL). The effects of HPDL radiation on the wettability and adhesion characteristics of the AOC and a vitreous enamel have been determined. The basic process phenomena are investigated and the effects of laser irradiation in terms of composition and microstructure are presented. Without laser treatment of the AOC surface it was not possible to fire the enamel onto the AOC. However, wetting experiments using a number of control liquids, by the sessile drop technique, revealed that laser treatment of the AOC surface resulted in the polar component of the surface energy increasing after laser treatment from 2.00 mJm-2 to 16.15 mJm-2. Additionally, surface roughness measurements revealed that after laser treatment, the surface roughness had decreased from an Ra value of 25.85μm to 6.27μm, whilst an energy disperse X-ray analysis (EDX) revealed that the relative surface oxygen content of the AOC had increased by 36.29% after laser treatment. Thus, laser treatment was identified as effecting a decrease in the enamel contact angle from 1180 to 330; consequently allowing the vitreous enamel to wet the surface. The bonding mechanisms were identified as being principally due to van der Waals forces, however, some evidence of chemical bonding was observed. The work has shown clearly that laser radiation can be used to alter the wetting characteristics of the AOC

High power diode laser marking and engraving of building materials

A Diomed 60W-cw high power diode laser (HPDL) has been used for the marking and engraving of various building materials, including; marble, granite, clay tiles, ceramic tiles, roof tiles, ordinary Portland cement (OPC) and clay bricks. Morphological and microstructural characteristics are presented. The basic mechanisms of marking/engraving and characteristics of the beam absorption are described. The effects of material texture, colour and laser processing parameters are reported. The work shows that engraving depths of over 2mm (0.75mm for a single pass) can be achieved on marble substrates by thermal disintegration of CaCO3 into loose CaO powder and CO2 gas. Uniform amorphous glazed lines (1-3mm line width) of a colour different from the untreated materials can be generated on clay tiles, ceramic tiles, roof tiles, clay bricks and OPC by solidification phase formation after laser melting of these materials. Effects of atmospheric conditions, for instance using O2 and Ar gas shrouds, have been examined, with different coloured marks being observed when different shroud gases are used. To demonstrate the practical worth of the process a UMIST crest has been marked on a ceramic tile using the system. Laser beam reflectivity is found to depend not only on material composition but also its colour. Reflectivity has been found to range between 12% to 18% for the various construction materials used in the experiment, except for marble (grey) which showed over 27% reflectivity. Since the HPDL is a portable device, in-field application of these processing techniques can be realised, which would be either impossible or difficult when using other types of lasers

Grout or mortar removal by lasers

The method comprises the steps of directing the beam of a portable laser device (40) onto grout (14) at a power level to cause removal of the grout; causing mutual relative movement between said laser beam and said grout; and, providing removal means (30, 32) for debris resulting from said grout removal. The laser beam (16) is transmitted to the grout (14) via optical fibre. The laser is selected from the group comprising: Nd-YAG laser; semi-conductor laser; and, diode pumped fibre laser, and may also include a low-power visible aiming laser. An area of grout being treated is surrounded by an enclosure (22) to prevent escape of laser light. The enclosure is transparent to optical light and opaque to laser light of the wavelength, e.g. 0.4 to 10.6 $g(m)m, in use. The laser beam spot (18) size being commensurate with the grout width. Debris removal means, possibly assisted with a gas jet (42), comprises suction removal (44) at a position adjacent the grout laser treatment area. The method may include the step of applying additional water to the grout

A two-stage ceramic tile grout sealing process using a high power diode laser Part II: Mechanical, chemical and physical properties

Ceramic tiles sealed using a portable 60 W-cw high power diode laser (HPDL) and a specially developed grout material having an impermeable enamel surface glaze have been tested in order to determine the mechanical, chemical and physical characteristics of the seals. The work showed that the generation of the enamel surface glaze resulted in a seal with improved mechanical and chemical properties over conventional epoxy tile grouts. Both epoxy tile grout and laser generated enamel seals were tested for compressive strength, surface roughness, wear, water permeability and acid/alkali resistance. The enamel seal showed clear improvements in strength, roughness and wear, whilst being impermeable to water, and resistance (up to 80% concentration) to nitric acid, sodium hydroxide and detergent acids. The bond strength and the rupture strength of the enamel seal were also investigated, revealing that the enamel adhered to the new grout and the ceramic tiles with an average bond strength of 45-60 MPa, whilst the rupture strength was comparable to the ceramic tiles themselves. The average surface roughness of the seals and the tiles was 0.36m and 0.06m respectively, whilst for the conventional epoxy grout the average surface roughness when polished was 3.83m, and in excess of 30m without polishing. Life assessment testing revealed that enamel seals had an increase in actual wear life of 2.9 to 30.4 times over conventional epoxy tile grout, depending upon the corrosive environment

Laser materials processing with diode lasers

Laser materials processing is currently dominated by CO2, Nd-YAG and Excimer lasers. Continuous advances in semiconductor laser technology over the last decade have increased the average power output of the devices annualy by two fold, resulting in the commercial availability of the diode lasers today with delivery output powers in excess of 60W in CW mode and 5kW in qasi-CW mode. The advantages of compactness, high reliability, high efficiency and potential low cost, due to the mass production capability of the diode laser, will inextricably shape its future in the field of materials processing. This papers reports on work exploring the feasibility of a range of materials processing applications using a Diomed 60W diode laser, transmitted through a 600m diameter optical fibre and coupled to a 3 axis CNC workstation. The applications studied include; marking and engraving natural stones (marble and granite), marking ceramic tiles, glazing and sealing tile grouts, marking and cutting glass, marking wood, welding metal wire and transformation hardening of tool steels. The study shows that even at the present limited power level of diode laser, many materials processing applications can be accomplished with satisfactory results. Through the study an initial understanding of interaction of diode laser beam with various materials has been gained. Also, within the paper basic beam characteristics, the state of the art of high power diode laser technology and current materials processing applications are also reviewed

Ceramic tile grout removal & sealing using high power lasers

Work has been conducted using a Nd:YAG laser, a CO2 laser and a high power diode laser (HPDL) in order to determine the feasibility of removing contaminated tile grout from the void between adjoining vitrified ceramic tiles, and to seal the void permanently with a material having an impermeable surface glaze. Reported on in the paper are; the basic process phenomena, the process effectiveness, suitable vitrifiable material development, a heat affect study and a morphological and compositional analysis

Surface modification of an Al2O3/SiO2 based ceramic treated with CO2, Nd:YAG, excimer and high power diode lasers for altered wettability characteristics

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 method of improving wettability and enamelling

There is described a method of enamelling a substrate, the method including the steps of: treating a thin surface layer of said substrate with a laser beam so as to promote a change in the surface energy thereof; allowing the surface to cool; and, applying enamel thereto to wet and coat said substrate

A Supersymmetric Twin Higgs

We present a supersymmetric realization of the twin Higgs mechanism, which cancels off all contributions to the Higgs mass generated above a scale f. Radiative corrections induced by the top quark sector lead to a breaking of the twin sector electroweak symmetry at a scale f ~ TeV. In our sector, below the scale f, these radiative corrections from the top quark are present but greatly weakened, naturally allowing a Z boson mass an order of magnitude below f, even with a top squark mass of order 1 TeV and a messenger scale near the Planck mass. A sufficient quartic interaction for our Higgs boson arises from the usual gauge contribution together with a radiative contribution from a heavy top squark. The mechanism requires the presence of an SU(2)-adjoint superfield, and can be simply unified. Naturalness in these theories is usually associated with light winos and sleptons, and is largely independent of the scale of the colored particles. The assumption of unification naturally predicts the existence of many exotic fields. The theory often has particles which may be stable on collider timescales, including an additional color octet superfield. In the limit that m_SUSY >> f, the mechanism yields a UV completion of the non-supersymmetric twin Higgs, but with the notable improvement of a tree-level quartic for the standard model Higgs. In this framework, a successful UV completion requires the existence of new charged fields well below the scale f.Comment: 20 page

Olfactory working memory: the role of perceived odor name-ability

The purpose of this study was to examine the relationship among three factors: perceived odorant name ability, whether the odorant was ingested through a single nostril or both nostrils, and how the odorant is represented in working memory. Participants smelled odorants through the left or right nostril or with both nostrils and then provided an identifying label for each odor and rated how accurately their label represented the odor. After a short delay, the participants were given a new stimulus set consisting of new and old odorants. Participants were asked to provide a label for the odor and determine whether the odor was new or old. These ratings were used to evaluate how odors are represented in working memory. A significant main effect showing a both nostril advantage in odor naming accuracy compared to single nostril accuracy was observed