It is quite possible to bring about changes in the wettability characteristics of a two-stage ceramic tile grout by means of high power diode laser (HPDL) surface treatment. Such changes manifest themselves as a reduction in the contact angle, Š , and are due to the HPDL inducing changes which reduce the surface roughness, increase the surface O 2 content and increasing the polar component of the surface energy. What is more, HPDL treatment of the two-stage ceramic tile grout surface was found to effect an improvement in the bonding characteristics by increasing the work of adhesion, W ad . Along with wettability experiments carried out with selected liquid-metals, an electronic approach was used to identify the bonding characteristics of the two-stage ceramic tile grout before and after HPDL. It is thought that HPDL induced changes to the two-stage ceramic tile grout produced a surface with a reduced bandgap energy which consequently increased W ad by increasing the electron transfer at the metal-oxide i...

In order to improve the practical laser hole drilling application, the assessment of the end product quality is essential. One of the methods of assessing the hole quality is to analyze the features of hole geometric sections by statistical methods. In the present study, laser hole drilling in Inconel 617 alloy is considered and the factorial analysis based on the statistical technique is introduced when identifying the significance levels of the operational parameters. The parameters selected are drilling ambient pressure, laser output energy, focus settings of focusing lens, and workpiece thickness. In order to complete the factorial analysis, four levels of each parameter are taken into account. The laser drilled holes were cross-sectioned and examined under the microscope. A marking scheme is introduced to evaluate the geometric features of the hole cross-section. It is found that the workpiece thickness and focus setting are the most significant parameters for the formation of hole cross-section. The effects of ambient pressure on the resultant hole geometry are also found to be significant.

The aim of this investigation was the production of wear and corrosion resistant coatings on magnesium base alloys. In particular it was proposed to generate by laser layers which operate as cylinder liners in a magnesium engine block thus replacing the currently used cast iron cylinder liners used in aluminium engines. These layers were produced using a 10 kW CO 2 laser and powder mixtures of aluminium + copper, aluminium + silicon and an alloyed aluminium-silicon powder in the single step process. The properties of these layers were characterised by metallographic investigations such as optical and scanning electron microscope and hardness measurements. The corrosion resistance has been determined using a modified immersion test in sulphuric acid with drying cycles in air. These conditions are comparable to the conditions found in combustion engines where the layers are to be used. Positive results were obtained with respect to the microstructure formation. Intermetallic phases can ensure a good wear resistance in laser treated material. An acceptable corrosion resistance was achieved by laser alloying with AlSi30 powder.

The thermal phenomena induced by zeptosecond (10 m 21 s) laser pulses are discussed in this article. Considering the theoretical proposal of the lasetron , the Heaviside equation for heat transport on zeptosecond time scale is formulated. In the article, the modified Schrodinger equation (Janina Marciak-koz ^ owska and Miros ^ aw Koz ^ owski (2002). Lasers in Engineering , 12 , 53) for quantum phenomena on the zeptosecond time scale was also discussed.

With the growing importance of micro machining, it has become important to characterise the profile of slot surfaces in order to understand the machining process in detail. In this paper, a novel optical layout adapting the concept of Mirau interferometry to polarization optics, in combination with instantaneous phase shifting interferometry, for measurement of slot surfaces is described. Experiments were carried out with this setup on a wafer surface with slot and the results were compared with that of a commercial surface profiler to demonstrate the applicability of the principle. The results obtained, were discussed with reference to the beam spot size, positioning of the object and the vertical resolution of the measurement setup, and compared with that of the commercial surface profiler.

Laser surface alloying involves tailoring the surface microstructure and composition by rapid melting, intermixing and solidification of a pre/co-deposited surface layer with a part of the underlying substrate. It is a potential method of enhancing hardness and wear resistance of engineering components. In the present study, a one-dimensional heat transfer model based on the explicit finite difference method has been developed to predict the thermal history (i.e., temperature profile, thermal gradient, cooling rate and solid-liquid interface velocity) and hence, the microstructure of the alloyed zone developed by laser surface alloying. The incident laser power and laser-matter interaction time are chosen as the main variables to study the effect of laser parameters on thermal history, and consequently, microstructure of the alloyed zone. The numerical calculations have been carried out for the model system of AISI 304 stainless steel laser surface alloyed with pre-deposited molybdenum. The predicted results have been compared with same relevant experimental data.

In this paper the interaction of attosecond laser pulses with matter is investigated. The scattering and motion of heat carriers as well as the external force are considered. The heat transport is described by the thermally forced Klein-Gordon or thermal modified telegraph equation depending on the ratio of the scattering and potential motion. In the case of the thermal Heisenberg type relation V ‰ ∽ E ( ‰ is the relaxation time and V is the potential) the heat transport is described by the thermal distortionless damped wave equation. In this paper the Klein-Gordon, modified telegraph 1 equation and wave equation are solved.

Recently the measurement of X-ray pulses approaching the attosecond frontier was published (M. Drescher et al ., Science 291 (2001) p. 1923). The attosecond laser pulse enables the study and control of the motion of electrons inside atoms. In this paper we develop and solve the modified Schrodinger equation (MSE) which describes the interaction of electrons with its surroundings in an atom. This interaction can be detected only using an attosecond laser pulse within the relaxation time of the interaction which is of the order of 10 attoseconds.

The surface melting characteristics of AZ91 alloy is investigated using excimer laser (pulses of length 45 ns) under ambient conditions and also a N 2 environment. Experiments are carried out on overlapping spots with close interval. The melt layer hardness for treatment in air is increased to 162 VHN as compared to 73 VHN for the untreated alloy (AZ91 T4 condition), whereas the hardness of the sample treated in an N 2 atmosphere is 116 VHN. A transmission electron microscopy study reveals that the laser treated surface contains nanoparticles of oxide and nitride embedded in the submicron grains of the Mg solid solution. This is responsible for the observed high hardness which gives rise to the improved abrasive resistance. We propose a model to describe the formation of nanoparticles during the laser treatment.

This article concerns functionally gradient materials (FGM) realized by laser sintering. Layers of Fe rich and Cu rich powders were compacted first and then laser sintered to obtain multilayer samples with smooth composition gradients. Microanalysis profiles on the cross sections of sintered samples show gradual increasing of Cu content and decreasing of Fe content. The laser sintered FGM contain several phases such as free graphite, ferrite, pearlite, Cu-Ni solid solutions, austenite, f -Cu phase, i -phase (Cu 31 Sn 8 ), k -phase (Cu 3 Sn) as well as m -phase (Cu 6 Sn 5 ). The experimental results show good wear resistance and toughness properties of the laser sintered FGMs.