J. Pou

Comprehensive assessment of the CO2 laser cut quality of ceramics with different assist gas injection systems

CO2 laser cutting is an efficient and advantageous process for cutting of ceramics when the hardness of such materials makes the conventional machining methods unproductive. At the same time, the application of laser cutting to ceramics involves the assessment of the different process parameters to select the suitable conditions for every specific ceramic. In this work, a comprehensive analysis of the CO2 laser cutting of mullite-alumina is presented. The cut quality was assessed under the criterion of facilitate the comparison of the results obtained using different process parameters and two different assist gas injection systems. For this reason, some quantitative standard parameters were analyzed (kerf width, roughness, perpendicularity), besides of the preliminary survey of some features and the microscopic examination of the heat affected zone. The results demonstrate the improvement of the cut quality using an assist gas injection system based on an off-axis De Laval nozzle.

Surface treatment of granite by high power diode laser

Granite stones have been used from times immemorial as structural element for public works and construction of every kind of building. At present, granite stones are used widely for facades, paving and flooring; polished being the most commonly used surface finish type. Recent years have seen a dramatic increase in the demand of granite plates having a rougher, more “rustic” surface finish. In this article we present the results of an exploratory study on the capabilities of the high power diode laser to treat the surface of granite plates. The results allow us to affirm that the laser presents several advantages in comparison to the conventional mechanical method: mechanical stresses are not induced in the granite plate, waste powder is reduced, and hazardous noise is not a byproduct.

Laser Surface Texturing of Polymers for Biomedical Applications

Polymers are materials widely used in biomedical science because of their biocompatibility, and good mechanical properties (which, in some cases, are similar to those of human tissues); however, these materials are, in general, chemically and biologically inert. Surface characteristics, such as topography (at the macro-, micro, and nanoscale), surface chemistry, surface energy, charge or wettability are interrelated properties, and they cooperatively influence the biological performance of materials when used for biomedical applications. They regulate the biological response at the implant/tissue interface (e.g., influencing the cell adhesion, cell orientation, cell motility, etc.). Several surface processing techniques have been explored to modulate these properties for biomedical applications. Despite their potentials, these methods have limitations that prevent their applicability. In this regard, laser-based methods, in particular laser surface texturing (LST), can be an interesting alternative. Different works have showed the potentiality of this technique to control the surface properties of biomedical polymers and enhance their biological performance; however, more research is needed to obtain the desired biological response. This work provides a general overview of the basics and applications of LST for the surface modification of polymers currently used in the clinical practice (e.g. PEEK, UHMWPE, PP, etc.). The modification of roughness, wettability, and their impact on the biological response is addressed to offer new insights on the surface modification of biomedical polymers.

Optimization of laser drilling of slate tiles

Slate is a natural rock with good mechanical properties and nice aesthetic appearance. Its utilization in residential constructions confers an elegant rustic external appearance, while keeping an excellent impermeability and robustness. Therefore, this rock is widely used in building construction, decoration, fireplaces and even handcrafted objects, particularly in regions owning natural slate quarries.The modern building construction is nowadays asking for improved manufacturing processes for its roofing materials since market requirements are continuously increasing. However, there is currently a lack of a reliable drilling process for slate. Making drills on a slate tile is still a difficult task because of its high hardness and its particular structure with parallel layers. A significant number of slate tiles are broken due to mechanical stress caused by traditional drilling tools. In this sense, lasers have already been demonstrated as a reliable tool for generate holes on a wide variety of materials and, particularly, in some stones. Due to its high precision, energy density, and its availability to be automated a great number of small holes can be produce in a short period of time.In this work, an experimental analysis on the CO2 laser drilling process of slate tiles is presented. We have used a systematic approach to determine the most adequate processing conditions to produce submillimeter holes in 5 mm thick slate tiles with good quality as well as in a minimum processing time.Slate is a natural rock with good mechanical properties and nice aesthetic appearance. Its utilization in residential constructions confers an elegant rustic external appearance, while keeping an excellent impermeability and robustness. Therefore, this rock is widely used in building construction, decoration, fireplaces and even handcrafted objects, particularly in regions owning natural slate quarries.The modern building construction is nowadays asking for improved manufacturing processes for its roofing materials since market requirements are continuously increasing. However, there is currently a lack of a reliable drilling process for slate. Making drills on a slate tile is still a difficult task because of its high hardness and its particular structure with parallel layers. A significant number of slate tiles are broken due to mechanical stress caused by traditional drilling tools. In this sense, lasers have already been demonstrated as a reliable tool for generate holes on a wide variety of materials...

Sub-milimetric titanium parts generated by rapid prototyping based on laser cladding

Rapid Prototyping based on Laser Cladding is an Additive Manufacturing (AM) technique that can be applied to any material which can be melted. It can be found under different names and acronyms: Direct Laser Deposition (DLD), Laser Metal Deposition (LMD), Laser Engineering Net Shaping (LENS), etc. Despite the different names, the basics of these methods are the same: a scanning laser beam creates a molten pool, in which a precursor material is fed; by the relative movement between the substrate and the laser, a cladding track is generated; and by the overlapping of cladding tracks is possible to manufacture functional 3D parts, layer by layer. Apart from that, titanium and its alloys present excellent properties like corrosion resistance, biocompatibility and high strength-to-weight ratio. They are widely used by several industries, in particular for biomedical, chemical, aircraft and marine applications. However, the machinability of titanium is considered poor and the loss of material produced by conventional manufacturing methods is highly costly. Rapid Prototyping Based on Laser Cladding is a solution to manufacture functional parts of titanium and avoid these obstacles. In this research work, Rapid Prototyping based on Laser Cladding is applied to obtain sub-milimetric simple titanium parts. A fiber laser delivering a maximum power of 200 W is used to process the precursor material selected: commercial pure titanium (cp-Ti) powder. The parts generated are analyzed by different characterization methods to study the microstructure, composition and properties.Rapid Prototyping based on Laser Cladding is an Additive Manufacturing (AM) technique that can be applied to any material which can be melted. It can be found under different names and acronyms: Direct Laser Deposition (DLD), Laser Metal Deposition (LMD), Laser Engineering Net Shaping (LENS), etc. Despite the different names, the basics of these methods are the same: a scanning laser beam creates a molten pool, in which a precursor material is fed; by the relative movement between the substrate and the laser, a cladding track is generated; and by the overlapping of cladding tracks is possible to manufacture functional 3D parts, layer by layer. Apart from that, titanium and its alloys present excellent properties like corrosion resistance, biocompatibility and high strength-to-weight ratio. They are widely used by several industries, in particular for biomedical, chemical, aircraft and marine applications. However, the machinability of titanium is considered poor and the loss of material produced by conven...

Rapid prototyping of metallic structures based on laser micro-cladding

In the last years, the demand of products fabricated by rapid prototyping techniques has grown sharply for many different uses, such as the fabrication of scale models and functional pieces with special characteristics for the industrial sector or the production of implants in the biomedical sector. This fact is joined to the research effort which is being carried out to obtain micro-scale products like biomedical sensors, a huge amount of MEMS devices or even 3D batteries in order to overcome some of the limits of the current macro-devices.In the majority of the cases, thin film techniques like sputtering or LCVD as well as techniques based on 3D printing are being used to obtain the micro-scale devices, with the limitations inherent to these techniques like the need of vacuum systems, the processing speed or the restrictions in the types of materials. In that sense, some of these limitations could be overcome adopting a raping prototyping technique based on laser cladding. In this work we propose the rapid prototyping of functional parts based on laser micro-cladding, which can be considered as a downscaling of conventional laser cladding, due to its higher processing rate and its ability to work with a wide range of materials. On the other hand, another main feature of this one step additive technique is the low thermal loads applied to the substrate, which is an important parameter in applications where the laser interaction zone is close to sensitive elements.An experimental set-up based on the use of a single mode fiber laser and a lateral powder injection system adequate to supply micron and submicron particles was used to produce metallic 3D structures in the micrometer range. The influence of several processing parameters on the geometry and mechanical properties of the tridimensional structures were systematically studied.In the last years, the demand of products fabricated by rapid prototyping techniques has grown sharply for many different uses, such as the fabrication of scale models and functional pieces with special characteristics for the industrial sector or the production of implants in the biomedical sector. This fact is joined to the research effort which is being carried out to obtain micro-scale products like biomedical sensors, a huge amount of MEMS devices or even 3D batteries in order to overcome some of the limits of the current macro-devices.In the majority of the cases, thin film techniques like sputtering or LCVD as well as techniques based on 3D printing are being used to obtain the micro-scale devices, with the limitations inherent to these techniques like the need of vacuum systems, the processing speed or the restrictions in the types of materials. In that sense, some of these limitations could be overcome adopting a raping prototyping technique based on laser cladding. In this work we propose the ra...

Production of TiO2 nanoparticles by laser ablation in aqueous medium

TiO2 nanoparticles have received a special attention due to their applications in many different fields. In this work we report on the production of TiO2 nanoparticles by means of a pulsed laser to ablate titanium metallic target submerged in water and ethanol. TiO2 nanoparticles with controllable average diameter have been obtained. Crystalline phases, morphology and optical properties of the obtained nanoparticles were characterized by means of transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and UV-vis absorption spectroscopy. The produced colloidal suspensions consisting in titanium dioxide crystalline nanoparticles showed spherical shape with diameters ranging from 3 to 40u2005nm. Nanoparticles are polycrystalline and exhibit the coexistence of anatase as well as rutile phases when de-ionized water is used as dissolvent, while the presence of brookite is observed when ethanol is used.TiO2 nanoparticles have received a special attention due to their applications in many different fields. In this work we report on the production of TiO2 nanoparticles by means of a pulsed laser to ablate titanium metallic target submerged in water and ethanol. TiO2 nanoparticles with controllable average diameter have been obtained. Crystalline phases, morphology and optical properties of the obtained nanoparticles were characterized by means of transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and UV-vis absorption spectroscopy. The produced colloidal suspensions consisting in titanium dioxide crystalline nanoparticles showed spherical shape with diameters ranging from 3 to 40u2005nm. Nanoparticles are polycrystalline and exhibit the coexistence of anatase as well as rutile phases when de-ionized water is used as dissolvent, while the presence of brookite is observed when ethanol is used.

Production of micro-scale coatings by novel laser micro-cladding technique

Production of coatings in the micrometer range (i.e.: with features smaller than 100 micrometers) is still a challenge. Extending the well established thin film techniques such as CVD, PLD or sputtering to produce thicker coatings means to invest a huge amount of time in producing such coatings. On the other hand the techniques available to produce thick coatings such as plasma spray, flame spray, or laser cladding are not suitable to produce coatings in the micrometer range.In order to provide an adequate response to this challenge, a new technique called laser micro-cladding has been developed to produce clad strips with geometrical characteristics in the micrometer range. Main feature of laser micro-cladding processing is the ability to reduce the thermal load applied to the substrate but keeping the good mechanical properties of the coating material.A new experimental set-up based on the use of a single mode fibre laser and a powder micro-feeder was used to produce the micro-coatings. The study of the...

A model of material removal mechanisms in pulsed laser cutting of ceramics

A theoretical model of the pulsed laser cutting of ceramics is presented. The ejection mechanisms of the processed material from the cutting front are modeled under the assumption that the ceramic material may be both melted and evaporated by the laser radiation. Therefore, three ejection mechanisms are investigated simultaneously: ejection of molten material by the assist gas, evaporation of the liquid, and ejection of molten material due to the recoil pressure generated by the evaporation from the cutting front.The temporal evolution of the ejection mechanisms is solved for several laser pulse modes. Theoretical results are compared with experimental observations to validate the conclusions regarding the influence of frequency and pulse length on the cutting process.