Laser dressing of metal bonded diamond blades for cutting of hard brittle materials

Philipp von Witzendorff, Anas Moalem, Rainer Kling, and Ludger Overmeyer

In this study, the authors investigate the laser dressing of metal bonded diamond blades by means of laser pulses with different pulse durations and wavelengths. Conventional dressing suffers from excessive blade wear, whereas laser dressing enables precise removal of the bonding metal to generate the required chip space of protruding diamond grains. The challenge for processing this composite material is to find appropriate level of ablation for the bonding metal without damaging the diamond grains through cracking or graphitization. For worn out blades, the influence of pulse duration and wavelength on laser dressed surface topography and bonding metal removal is studied. The experiments are performed with 532 and 1064 nm laser radiation with pulse durations from 12 ps to 20 ns. The blade surface topography and bonding metal removal of the dressed blades are measured with a confocal microscope, where the protruding diamond grains are identified by scanning electron microscope examinations. The dressing results show the bonding metal removal for the available laser sources in the studied pulse duration range, with the increasing number of protruding diamond grains for shorter pulse durations. The results indicate a significant increase of blade lifetime for laser dressed blades compared to conventional dressing methods.

Silicon(IV) phthalocyanine-loaded-nanoparticles for application in photodynamic process

Andreza Ribeiro Simioni, Fernando L. Primo, and Antonio Claudio Tedesco

The aim of this study was to evaluate the potential application of biodegradable nanoparticles containing a photosensitizer in photodynamic therapy. The poly (D,L lactic-co-glycolic acid) nanoparticles were studied by steady-state techniques, time-resolved fluorescence, and laser flash photolysis. The external morphology of the nanoparticles was established by scanning electron microscopy, and the biological activity was evaluated by in vitro cell culture by 3-(4,5 dimethyl-thiazol-2,5 biphenyl) tetrazolium bromide assay. The particles were spherical in shape exhibiting a 435 nm diameter with a low tendency to aggregate. The loading efficiency was 77%. The phthalocyanine-loaded-nanoparticles maintained their photophysical behavior after encapsulation. The cellular viability was determined, obtaining 70% of cellular death. All the performed physical–chemical, photophysical, and photobiological measurements indicated that the phthalocyanine-loaded-nanoparticles are a promising drug delivery system for photodynamic therapy and photoprocesses.

Ultra-high speed disk laser cutting of carbon fiber reinforced plastics

Kwang-Woon Jung, Yousuke Kawahito, and Seiji Katayama

Laser cutting of carbon fiber reinforced plastics (CFRPs) has been known to be difficult due to the thermal damage to CFRP material. Therefore, with the objectives of evaluating the cutting possibility for long- or short-fiber pellet CFRP sheets of 3 mm in thickness and obtaining narrower heat affected zone (HAZ) for better cut quality, ultra-high speed cutting was conducted by using a continuous-wave high brightness disk laser. The increase in the laser power rendered the cutting time shorter and the kerf depth deeper for CFRP full cut. It was revealed that CFRP cut with narrow HAZ of less than 50 μm could be produced under the conditions of the laser powers of 2–5 kW, the cutting speed of 5 m/s, the time interval between repeated runs of 1 s, and the defocused distance of 0 mm. It was also confirmed that short fiber pellet CFRP was more easily cut and suffered less thermal damage in comparison with long fiber one. Furthermore, it was demonstrated that the tensile strength of fully laser-cut CFRP was almost equal to that of the base CFRP specimen. This means the laser-cut surfaces of the CFRP sheet were not degraded in mechanical properties.

J. Laser Appl. 24, 012007 (2012)

Laser texturization to improve absorption and weld penetration of aluminum alloys

J. M. Sánchez-Amaya, Z. Boukha, L. González-Rovira, J. Navas, J. Martín-Calleja, and F. J. Botana

In the present work, laser texturization treatments have been performed for the first time on aluminum alloys to increase their absorption and weld penetration. Adjusting the experimental conditions, laser texturization increases the roughness and decreases the diffuse and specular reflectance of surfaces. The textured samples were subsequently subjected to bead-on-plate laser weld treatments with a high power diode laser. Taking the weld beads of sandblasted samples as reference, depth improvements percentages around 20% are reached in some textured samples. Laser texturization has demonstrated to increase the weld penetration ability of aluminum alloys, constituting a potential tool to reduce the energetic requirements of the laser welding process.

Investigation of the Effect of Irradiance and Pulse Duration in Industrial Percussion Laser-Drilling of Waspaloy

Robin Bright and Harris L. Marcus

As the use of pulsed lasers in the manufacture of cooling holes in high-temperature gas-turbine engine components continues to increase, understanding the material behavior during laser-material interaction and the subsequent effects on hole quality becomes critical. In this study, atomic emission spectroscopy is used to monitor the optical characteristics of ejected material during percussion laser-drilling of Waspaloy over irradiance and pulse duration values in the ranges of 10–20 MW/cm2 and 0.3–1.1 ms, respectively. While irradiance is a widely used target parameter, it was experimentally determined that pulse duration had a larger impact on both the calculated electron temperature of the ejected material as well as on the thickness of residual resolidified, or recast, layer of material on the inside walls of drilled holes.

Thermal Diffusivity Measurement of Silver Nanofluid by Thermal Lens Technique

Reza Zamiri, B. Z. Azmi, E. Shahriari, Kazim Naghavi, E. Saion, Zahid Rizwan, and M. S. Husin

The thermal lens technique was utilized in silver nanofluid containing silver nanoparticles in polyvinylpyrrolidone solution to study the effect of nanoparticle size on thermal diffusivity. The different sizes of silver nanoparticles were prepared by irradiating the solution of silver nitrate in polyvinylpyrrolidone with respective dose of γ-radiation. The average sizes of particle in the prepared samples were measured using nanophox machine. The thermal lens measurement was carried out by using a diode laser of wavelength 514 nm and a He–Ne laser for the excitation source and the probe beam, respectively. The obtained result showed a decrease in the thermal diffusivity of nanofluid with the decrease in particle size.

Direct Manufacturing of Net-Shape Functional Components/Test Pieces for Aerospace, Automotive and Other Applications

Lijue Xue, Yangsheng Li and Shaodong Wang

Laser consolidation (LC) is a novel computer-aided manufacturing process being developed by the Industrial Materials Institute of National Research Council of Canada (NRC-IMI). This rapid manufacturing process produces net-shape functional metallic parts layer-by-layer directly from a computer-aided design (CAD) model by using a laser beam to melt the injected powder and resolidifying it on the substrate or previous layer. As an alternative to the conventional machining process, this novel manufacturing process builds net-shape functional parts or features on an existing part by adding instead of removing materials. In this paper, laser consolidation of various high performance materials (such as Ni-alloys, tool steels, etc.) will be demonstrated to manufacture functional components or test-pieces (such as shell-based mold inserts, impeller, intersected multihexagon tube, goblet shape, etc.) for potential aerospace, automotive, and other applications. In the paper, dimensional accuracy of various laser-consolidated test-pieces will be measured and compared with CAD models. In addition, an example will be given on laser consolidation to build complex cold spray nozzles that are difficult to make otherwise and significantly improve the performance.

Femtosecond Laser Machined Microfluidic Devices for Imaging of Cells during Chemotaxis

Lino Costa, Alexander Terekhov, Deepak Rajput, William Hofmeister, D. Jowhar, G. Wright, C. Janetopoulos

Microfluidic devices designed for chemotaxis assays were fabricated on fused silica substrates using femtosecond laser micromachining. These devices have built-in chemical concentration gradient forming structures and are ideally suited for establishing passive diffusion gradients over extended periods of time. Multiple gradient forming structures, with identical or distinct gradient forming characteristics, can be integrated into a single device, and migrating cells can be directly observed using an inverted microscope. In this paper, the design, fabrication, and operation of these devices are discussed. Devices with minimal structure sizes ranging from 3 to 7 μm are presented. The use of these devices to investigate the migration of Dictyostelium discoideum cells toward the chemoattractant folic acid is presented as an example of the devices’ utility.

The Effect of Multiple Laser Alloyed Tracklines on the Corrosion Properties of Al-MMC

Patricia A. I. Popoola, Sisa L. Pityana, and Olawale M. Popoola

In real life engineering applications, production of large area coverage is often required especially for preventing material loss and component damage. To enhance such applications, multiple tracklines laser surface alloying of Al/TiB2 was performed to obtain a large area coverage using Nd:YAG laser. The overlap rate was 50%. The characterization of the metal matrix composite was carried out by optical microscopy (OM), scanning electron microscopy (SEM), and x-ray diffraction (XRD).