Ultrafine and nanoparticle formation and emission mechanisms during laser processing of ceramic materials

The use of laser technology in the ceramic industry is undergoing an increasing trend, as it improves surface properties. The present work aimed to assess ultrafine and nanoparticle emissions from two different types of laser treatments (tile sintering and ablation) applied to two types of tiles. New particle formation mechanisms were identified, as well as primary nanoparticle emissions, with concentrations reaching up to 6.7 x 10(6) particles Cm-3 and a mean diameter of 18 nm. Nanoparticle emission patterns were strongly dependent on temperature and raw tile chemical composition. Nucleation events were detected during the thermal treatment independently of the laser application. TOM images evidenced spherical ultrafine particles, originating from the tile melting processes. When transported across the indoor environment, particles increased in size (up to 38 nm) with concentrations remaining high (2.3 x 10(6) particles cm(-3)), Concentrations of metals such as Zn, Pb, Cu, Cr, As and al were found in particles < 250 nm

Improved copper–epoxy adhesion by laser micro- and nano-structuring of copper surface for thermal applications

The objective of this work is the enhancement of metal-to-metal bonding to provide high thermal conductivity together with electrical insulation, to be used as heat sinks at room and cryo-genic temperatures. High thermal conductive metal (copper) and epoxy resin (Stycast 2850FT) were used in this study, with the latter also providing the required electrical insulation. The copper surface was irradiated with laser to induce micro- and nano-patterned structures that result in an improvement of the adhesion between the epoxy and the copper. Thus, copper-to-copper bonding strength was characterized by means of mechanical tensile shear tests. The effect of the laser processing on the thermal conductivity properties of the Cu/epoxy/Cu joint at different temperatures, from 10 to 300 K, is also reported. Using adequate laser parameters, it is possible to obtain high bonding strength values limited by cohesive epoxy fracture, together with good thermal conductivity at ambient and cryogenic temperatures. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Large enhancement of thermal conductance at ambient and cryogenic temperatures by laser remelting of plasma-sprayed Al2O3 coatings on Cu

Joints of high thermal contact conductance and electrical insulation have been obtained by coating copper supports with thin alumina (Al2O3) layers (of 140–150 µm thickness). This has been achieved by a combination of plasma spraying process and the subsequent coating remelting by a near-Infrared (n-IR) laser. With a proper optimization of the laser processing conditions, it is possible to transform the metastable ¿-Al2O3 phase of the as-sprayed coatings to stable a-Al2O3, and to achieve denser alumina coatings. This results in a large enhancement of the thermal conductance of the joints, enabling their application as heat sinks at cryogenic and ambient temperatures. The process proposed in this work is scalable for the formation of alumina coatings on large metallic pieces of complex geometries. © 202

Properties and antibacterial activity of MnFe2O4 nanoparticles obtained by pulsed laser ablation in liquid

In this study, MnFe2O4 nanoparticles (NPs) were fabricated via pulsed laser ablation in liquid. Chemical and structural composition, microstructure, magnetic and antibacterial properties were characterized. Spinel was found as the main crystalline phase, while Fe2O3 and Mn2O3 were observed as the major secondary phases, all identified by X-ray diffractometry (XRD). Observation by Transmission Electron Microscopy (TEM) indicated that most of the nanoparticles were spherical in shape and found in agglomerates, most likely because of their magnetic nature. Moreover, Fast Fourier Transform of selective area electron diffraction patterns pointed at the existence of crystalline particles. The coercive field (Hc) and saturation magnetization (Ms) values determined for these NPs were found to increase with decreasing temperature. Their antibacterial properties were evaluated using the viable bacteria counting technique (colony) for MnFe2O4 concentrations of 100 and 300 μg/mL with Bacillus subtilis, Salmonella typhimurium, Pseudomonas aeruginosa, Klebsiella pneumoniae and Escherichia coli strains

Laser-induced coloration of ceramic tiles covered with magnetron sputtered precursor layers

This paper reports a new methodology for the coloring of glazed ceramic tiles consisting of the near infrared pulsed laser processing of copper containing oxide coatings prepared by magnetron sputtering. As a second approach, the employ for the same purpose of a novel laser furnace technique is also described. Changing the laser parameters and using the laser furnace to treat the tiles at high temperature during irradiation has resulted in a wide color palette. The optical characterization of the modified tiles by UV-Vis spectroscopy has been complemented with their microstructural and compositional analysis by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Time Of Flight Secondary Ion Mass Spectrometry (TOF-SIMS). The chemical composition of the surface was obtained by X-ray Photoemission Spectroscopy (XPS) and its structure determined by X?ray diffraction (XRD). The chemical resistance was characterized by several tests following the norm ISO 10545-13. Color changes have been attributed to surface microstructural and chemical transformations that have been accounted for by simple models involving different ablation, melting, diffusion, and segregation/agglomeration phenomena depending on the laser treatments employed

Continuous processing of Bi 2 Sr 2 CaCu 2 O 8+? precursor powders

A continuous solid-state process inside a roller furnace has been used to fabricate Bi-2212 powders. These powders were synthesized for their use as precursors to obtain textured monoliths by laser induced directional solidification. A thermal cycle has been defined, which depends on the length of the furnace, the prefixed temperature profile and the velocity of the sample inside the furnace. Powder properties have been studied as a function of the number of processing cycles. Phase evolution has been analyzed using X-ray diffraction, while other relevant properties of the powders, including grain size distribution, thermal behavior and temperature dependence of the AC susceptibility, have also been measured. These properties have been compared with those of commercial powders and precursors prepared using a standard solid-state protocol. Textured samples using these continuous solid-state precursors exhibit superconducting properties comparable to those similarly processed but prepared from commercial powders. © 2018 Elsevier Ltd and Techna Group S.r.l.ENE2014-52105-R Gobierno de Aragón Ministerio de Economía y CompetitividadThis work was supported by the Spanish Ministerio de Economía y Competitividad and the European FEDER Program (project ENE2014-52105-R ), and by the Gobierno de Aragón (research groups T12, T87 and T54_17R). The authors acknowledge the use of Servicio General de Apoyo a la Investigación-SAI, University of Zaragoza

Microstructure and transport properties of Bi-2212 prepared by CO 2 laser line scanning

A novel Laser Line Scanning method has been applied to process rectangular cross-section Bi-2212 monoliths containing 2.9 % Ag using a CO2 Laser. Although previous work has suggested the use of nIR lasers (?0.8-1.1 µm) for melt-processing metal oxide superconductors, the results obtained here demonstrate that mid-IR radiation from a CO2 laser (10.6 µm) may be just as convenient for such a purpose while it enables processing large surface areas. The samples described here were processed at traverse rates ranging between 15 and 60 mm/h, exhibited a complex textured microstructure and yielded highest Ic values of 71 A at 77 K. © 2012 Springer Science+Business Media New York.LIFE11/ENV/ES 560 Direction Générale de l’Armement: Superconductivity MAT2011-22719, MAT2008-00429 Universidad de Zaragoza: UZ2011-TEC-03Acknowledgements The authors acknowledge the European Commission LIFE Program (LIFE11/ENV/ES 560 “CERAMGLASS”), the Spanish MINECO and European Commission FEDER Program (Projects MAT2008-00429 and MAT2011-22719), Universidad de Zaragoza (Project UZ2011-TEC-03 and Servicio General de Apoyo a la Investigación-SAI), as well as DGA for Groups T87 (Laser Applications Lab) and T13 (Applied Superconductivity)

Workplace exposure to nanoparticles in ceramic processes using laser technology

W artykule przedstawiono wyniki oryginalnych badań dotyczących narażenia pracowników przemysłu ceramicznego na ultradrobnej nanocząstki, które powstają w trakcie wykorzystywania lasera do spiekania oraz w wyniku ablacji laserowej. Wyniki przeprowadzonych badań porównano z wartościami referencyjnymi, zalecanymi w stosunku do wymienionych cząstek, a także skomentowano poziom narażenia pracowników, który został uwidoczniony eksperymentalnie.The article presents original research results regarding the exposure of workers employed in the ceramic industry towards ultra small and nanoparticles created as a result of laser sintering as well a laser ablation. The results of the research were compared with the referential values for the abovementioned particles and the experimentally proven level of worker's exposure was awarded a commentary