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Статті в журналах з теми "Laser surfaces treatment":
1
Ristic, Slavica, Suzana Polic, Bojana Radojkovic, and Joakim Striber. "Analysis of ceramics surface modification induced by pulsed laser treatment." Processing and Application of Ceramics 8, no. 1 (2014): 15–23. http://dx.doi.org/10.2298/pac1401015r.
Анотація:
This paper presents the effects of laser light irradiation on the surface of ceramics dating from archaeological site Stubline (Obrenovac, Belgrade), Serbia. Two different pulsed lasers: TEA CO2 (10.6 ?m wavelength, pulse duration tp = 100 ns) and Nd:YAG (wavelengths 1064 nm and 532 nm, tp = 150 ps) have been used for surfaces treatment. Laser irradiation fluence was in the range of 1-20 J/cm2. Ceramics surface modifications induced by pulsed laser treatment were examined by scanning electron microscope, SEM, and the composition with energy dispersive X-ray, EDX, analysis. The tests were performed in order to obtain as much as possible information about the appropriate choice of materials and techniques for the further conservation and restoration of these items. The second objective was to determine the surface modifications induced by pulsed laser treatment above damage threshold (a safe cleaning laser fluence), as an important parameter in the use of lasers for the cleaning of cultural ceramic items.
2
HONDA, RYO, MASAYOSHI MIZUTANI, HITOSHI OHMORI, and JUN KOMOTORI. "BIOCOMPATIBILITY EVALUATION OF NANOSECOND LASER TREATED TITANIUM SURFACES." International Journal of Modern Physics: Conference Series 06 (January 2012): 682–87. http://dx.doi.org/10.1142/s2010194512003972.
Анотація:
We developed surface modification technologies for dental implants in this study. The study contributes to shortening the time required for adhesion between alveolar bone and fixtures which consist of dental implants. A Nd : YVO 4 nanosecond laser was used to modify the surfaces of commercially pure titanium (CP Ti ) disks, and their biocompatibility was evaluated cytocompatibility and bioactivity. First, rows of 200 µm spaced rectilinear laser treatments were performed on surfaces of CP Ti disks. Osteoblasts derived from rat mesenchymal stem cells were then cultured on the treated surfaces. Cytocompatibility on the laser treated area was evaluated by observing adhesion behavior of cells on these surfaces. The results indicated that the micro-order structure formed by the laser treatment promoted adhesion of osteoblasts and that traces of laser treatment without microstucture didn't affect the adhesion. Second, surfaces of CP Ti disks were completely covered by traces of laser treatment, which created complex microstructures of titania whose crystal structure is rutile and anatase. This phenomenon allowed the creation of hydroxyapatite on the surface of the disks in 1.5-times simulated body fluid (1.5SBF) while no hydroxyapatite was observed on conventional polished surfaces in the same conditions. This result indicates that bioactivity was enabled on CP Ti by the laser treatment. From these two results, laser treatment for CP Ti surfaces is an effective method for enhancing adhesion of osteoblasts and promoting bioactivity, which are highly appreciated properties for dental implants.
3
Aronov, V., and M. Benetatos. "Wear Resistance of Laser Treated Partially Stabilized Zirconia." Journal of Tribology 111, no. 2 (April 1, 1989): 372–77. http://dx.doi.org/10.1115/1.3261926.
Анотація:
The laser beam treatment of magnesia partially stabilized zirconia (Mg-PSZ) sample surfaces has shown a considerable improvement in their wear resistance and surface hardness. The laser beam treated surfaces exhibited higher wear resistance than either ground untreated or ground and laser treated ceramic surfaces. There are optimum combination of the laser treatment process parameters (laser power and exposure characteristics) that resulted in the minimum wear rate or the maximum surface hardness. There was no correlation found between the wear rate and the surface hardness. There were two wear mechanisms operational, namely, surface fracture and surface polishing. The treatment of the ceramic surfaces reduced the fracture component of the wear rate. The laser treatment effect on the polishing process was not detected. The increase in the wear resistance and the surface hardness of the laser beam treated surfaces were due to the thermally induced phase transformations resulted in the formation of the compressive stress field on the surface and altering the surface structure.
4
Dodiuk, H., A. Buchman, S. Kenig, M. Rotel, J. Zahavi, and T. J. Reinhart. "Preadhesion Laser Treatment of Aluminum Surfaces." Journal of Adhesion 41, no. 1-4 (June 1993): 93–112. http://dx.doi.org/10.1080/00218469308026556.
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Scarano, Antonio, Francesca Postiglione, Ahmad G. A. Khater, Faez Saleh Al-Hamed, and Felice Lorusso. "A Novel Technique to Increase the Thickness of TiO₂ of Dental Implants by Nd: DPSS Q-sw Laser Treatment." Materials 13, no. 18 (September 20, 2020): 4178. http://dx.doi.org/10.3390/ma13184178.
Анотація:
High bone–implant contact is a crucial factor in the achievement of osseointegration and long time clinical success of dental implants. Micro, nano, microtopography, and oxide layer of dental implants influence tissue response. The lasers were used for achieving an implant surface with homogeneous micro texturing and uncontaminated surface. The present study aimed to characterize the implant surfaces treated by Nd: DPSS Q-sw Laser treatment compared to machined implants. A total of 10 machined implants and 10 lasered surface implants were evaluated in this study. The implant surfaces were evaluated by X-ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES), and metallography to characterize and measure the thickness of the oxide layer on the implant titanium surface. The machined surfaces showed a non-homogeneous oxide layer ranging between 20 and 30 nm. The lasered implant surfaces showed a homogeneous oxide layer ranging between 400 nm and 460 nm in the area of the laser holes, while outside the layer, thickness ranged between 200 nm and 400 nm without microcracks or evidence of damage. Another exciting result after this laser treatment is a topographically controlled, repeatable, homogeneous, and clean surface. This technique can obtain the implant surface without leaving residues of foreign substances on it. The study results indicate that the use of Nd: DPSS Q-sw laser produces a predictable and reproducible treatment able to improve the titanium oxide layer on the dental implant surface.
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Yilbas, Bekir S., Ihsan-ul-Haq Toor, and Jahanzaib Malik. "Laser surface treatment of aluminum composite: surface characteristics." Science and Engineering of Composite Materials 23, no. 5 (September 1, 2016): 495–503. http://dx.doi.org/10.1515/secm-2014-0108.
Анотація:
AbstractLaser treatment of an aluminum composite surface was carried out to improve tribological properties and corrosion resistance at the surface. The workpiece consists of 15% SiC and pure aluminum, and it is produced by hot pressing. The characteristics of the laser-treated surface were examined using optical and scanning electron microscopes, energy dispersive spectroscopy, X-ray diffraction, a micro-tribometer, and a potentiostat. Laser treatment was carried out by following a spiral scanning track at the surface. This provides a self-annealing effect of the lately formed laser tracks on the initially formed tracks while lowering the cooling rates at the surface. It was found that laser-treated surfaces are free from asperities such as large-scale cracks and voids. Laser treatment improves the hardness of the surface because of the dense layer formation in the surface region. The friction coefficient of the laser-treated surface attains lower values than that corresponding to the untreated surface. Laser treatment improves the corrosion resistance of the surface.
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Yao, Wan-Ling, Jerry Chin Yi Lin, Eisner Salamanca, Yu-Hwa Pan, Pei-Yo Tsai, Sy-Jye Leu, Kai-Chiang Yang, Haw-Ming Huang, Huei-Yu Huang, and Wei-Jen Chang. "Er,Cr:YSGG Laser Performance Improves Biological Response on Titanium Surfaces." Materials 13, no. 3 (February 7, 2020): 756. http://dx.doi.org/10.3390/ma13030756.
Анотація:
Porphyromonas gingivalis infection is one of the causes of implant failures, which can lead to peri-implantitis. Implant surface roughness is reportedly related strongly to P. gingivalis adhesion, which can lead to peri-implantitis and, later, cell adhesion. Our aim was to evaluate the effects of Er,Cr:YSGG laser on titanium (Ti) disc surfaces and its interaction with bacterial adhesion and fibroblast viability. Ti discs underwent two treatments: autoclaving (control) and erbium, chromium-doped yttrium scandium gallium garnet (Er,Cr:YSGG) laser treatment (test). Ti disc surfaces were examined with scanning electronic microscope (SEM), Energy-dispersive spectrometry (EDX), X-ray photoelectron spectroscopy (XPS). The surface roughness same as wettability were also investigated. Fibroblast viability was assessed with the water-soluble tetrazolium 1 (WST-1) test, and osteoblast differentiation was assessed with the alkaline phosphatase (ALP) assay. Bacterial structure and colony formation were detected with scanning electron microscopy and Gram stain. In comparison to control discs, the test discs showed smoother surfaces, with 0.25-µm decrease in surface roughness (p < 0.05); lower P. gingivalis adhesion (p < 0.01); less P. gingivalis colonization (p < 0.05); and increased fibroblast viability and osteoblast differentiation (p < 0.05). Er,Cr:YSGG laser treatment improved disc surfaces by making them slightly smoother, which reduced P. gingivalis adhesion and increased fibroblast viability and osteoblast differentiation. Er,Cr:YSGG laser treatment can be considered a good option for managing peri-implantitis. Further investigations of laser-assisted therapy are necessary for better guidelines in the treatment of peri-implantitis.
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Ho, Mei Po, Hon Wah Wai, Wai Yin Tam, and Michael Leung. "The Effect of Laser Treatment on the Secondary Bonding Behavior of Carbon Fibre Composite." Key Engineering Materials 845 (May 2020): 27–32. http://dx.doi.org/10.4028/www.scientific.net/kem.845.27.
Анотація:
Joining carbon fibre reinforced composites with adhesive are widely used in various applications including aircraft structures and commercialized leisure products. However, surface contaminations hinder the adhesion of the bonding. Laser based surface treatment on bonding surface is suggested to improve the adhesion on the surfaces for secondary bonding. In this paper, single lap shear tests of the samples show that the laser pre-treated samples lead to the higher joint strength then acetone cleaned reference samples and surface sanded samples. The failure mode changed from adhesion failure in the reference sample to cohesion mode in the laser treated samples. The structure, topography and morphology of the composite surfaces which were pre-treated with laser radiation were observed. A correlation between surface properties and adhesive bonding strength was investigated. It should be noted that the variation of the pulse frequency level of the laser treatment contributed to the fibre breakage and the epoxy removal level of the sample surfaces.
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Alnusirat, Walid, Maksym Kyrychok, Stefano Bellucci, and Iaroslav Gnilitskyi. "Impact of Ultrashort Laser Nanostructuring on Friction Properties of AISI 314 LVC." Symmetry 13, no. 6 (June 10, 2021): 1049. http://dx.doi.org/10.3390/sym13061049.
Анотація:
Laser irradiation yields a powerful tool to modify the symmetry and asymmetry features of materials surfaces. In this paper, femtosecond laser-induced periodic surface structures were applied on stainless steel AISI 314, specially hardened by a low-vacuum carburizing procedure. Symmetry modifications in the surface’s morphology and chemistry before and after the laser treatment were investigated by SEM and EDS, respectively. Coefficient of friction (COF) was observed in dry sliding condition by using block-on-ring sliding test. The results show that COF values are substantially lower after laser-induced periodic surface structures (LIPSS) surface treatment.
10
Liang, Shanshan, Hongqiang Ye, and Fusong Yuan. "Changes in Crystal Phase, Morphology, and Flexural Strength of As-Sintered Translucent Monolithic Zirconia Ceramic Modified by Femtosecond Laser." Applied Sciences 11, no. 15 (July 28, 2021): 6925. http://dx.doi.org/10.3390/app11156925.
Анотація:
Conventional bonding technology suitable for silica-based ceramics is not applicable to zirconia, due to its polycrystalline phase composition, chemical stability, and acid corrosion resistance. The development of an effective treatment to improve its surface roughness and mechanical properties remains an unresolved problem. Therefore, to solve this problem, this in vitro study evaluated the changes in surface morphology and flexural strength of translucent monolithic zirconia surfaces treated with femtosecond laser technology. As-sintered translucent zirconia specimens were subjected to airborne particle abrasion and femtosecond laser treatments, while control group specimens received no treatment. After treatment, the roughness and morphology of the treated zirconia surfaces were examined. The flexural strength and X-ray diffraction of the treated specimens were measured and analyzed. Statistical inferential analysis included one-way analysis of variance at a set significance level of 5%. The surface roughness after femtosecond laser treatment was significantly improved when compared with the control group and the group that received the airborne particle abrasion treatment (p < 0.05). In comparison with the airborne particle abrasion group, the flexural strength of the group that received the femtosecond laser treatment was significantly improved (p < 0.05). The femtosecond laser approach using appropriate parameters enhanced the roughness of the zirconia without reducing its flexural strength; therefore, this approach offers potential for the treatment of zirconia surfaces.
Дисертації з теми "Laser surfaces treatment":
1
Katakam, Shravana K. "Laser Surface Treatment of Amorphous Metals." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc500194/.
Анотація:
Amorphous materials are used as soft magnetic materials and also as surface coatings to improve the surface properties. Furthermore, the nanocrystalline materials derived from their amorphous precursors show superior soft magnetic properties than amorphous counter parts for transformer core applications. In the present work, laser based processing of amorphous materials will be presented. Conventionally, the nanocrystalline materials are synthesized by furnace heat treatment of amorphous precursors. Fe-based amorphous/nanocrystalline materials due to their low cost and superior magnetic properties are the most widely used soft magnetic materials. However, achieving nanocrystalline microstructure in Fe-Si-B ternary system becomes very difficult owing its rapid growth rate at higher temperatures and sluggish diffusion at low temperature annealing. Hence, nanocrystallization in this system is achieved by using alloying additions (Cu and Nb) in the ternary Fe-Si-B system. Thus, increasing the cost and also resulting in reduction of saturation magnetization. laser processing technique is used to achieve extremely fine nanocrystalline microstructure in Fe-Si-B amorphous precursor. Microstructure-magnetic Property-laser processing co-relationship has been established for Fe-Si-B ternary system using analytical techniques. Laser processing improved the magnetic properties with significant increase in saturation magnetization and near zero coercivity values. Amorphous materials exhibit excellent corrosion resistance by virtue of their atomic structure. Fe-based amorphous materials are economical and due to their ease of processing are of potential interest to synthesize as coatings materials for wear and corrosion resistance applications. Fe-Cr-Mo-Y-C-B amorphous system was used to develop thick coatings on 4130 Steel substrate and the corrosion resistance of the amorphous coatings was improved. It is also shown that the mode of corrosion depends on the laser processing conditions. The microstructure evolution and the corrosion mechanisms operating are evaluated using post processing and post corrosion analysis.
2
Dolan, Jeffrey Alan. "Characterization of Laser Modified Surfaces for Wood Adhesion." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/64352.
Анотація:
The controlled degradation of wood surfaces with infrared light from a CO2 pulsed laser facilitated adhesion without the use of additional resins. Laser modification creates a surface phenomenon that physically and chemically alters the natural biopolymer organization of lignocellulosic materials in a way that promotes adhesion when hot pressed using typical industrial equipment. Laser optimization was determined through mechanical and microscopic observation. It was determined that a mild level of laser surface modification (scale of 30 W/mm2) resulted in the highest bond-line strength. The large spot size of the laser beam resulted in evenly modified surfaces. Surface analysis revealed that laser modification changed native wood morphology, hydrolyzed and vaporized hemicellulose, and enriched the surface with cellulose II and lignin. Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR FTIR) was used to analyze the bulk of the laser material. This experiment revealed a change in the hydroxyl region related to hydrogen bonding conformations between wood polymers, mainly cellulose. X-ray photoelectron spectroscopy (XPS) provided an elemental composition of the top 5 nanometers of the surface, which resulted in increased carbon-carbon/carbon-hydrogen linkages and decreased oxygen containing bonds due to laser ablation. Static acid-base contact angle analysis was conducted using three probe liquids to find the Lewis acid, Lewis base, and dispersion components of the top nanometer of surface chemistry. Contact angle analysis revealed laser modified samples had a surface free energy that remained similar to the control wood sample. In addition, the dispersion component of the surface free energy increased due to laser ablation while acid-base components were reduced. Atomic force microscopy (AFM) visually displays a reduction in surface roughness due to the laser technique. An additional set of experiments like thermal gravimetric analysis, thermal pre and post treatments, and heated ATR FTIR and XPS support findings which require more investigation into this adhesion phenomenon.Master of Science
3
Belaud, Vanessa. "Structuration de surfaces au moyen d'un traitement laser femtoseconde : applications à la fonctionnalisation de surface du polypropylène en vue de sa métallisation." Thesis, Ecully, Ecole centrale de Lyon, 2014. http://www.theses.fr/2014ECDL0003/document.
Анотація:
Ce présent travail de thèse porte sur l’étude du potentiel d’un traitement de surface par laser femtoseconde comme étape de substitution aux traitements réalisés actuellement lors de la métallisation de polymère. Pour cela, l’étude des modifications chimiques et morphologiques induites par traitement laser femtoseconde ainsi que leurs influences respectives sur les propriétés d’adhérences et de mouillabilités de la surface polypropylène sont présentées. Une revue bibliographique met en évidence la faisabilité d’une modification contrôlée de la surface du polypropylène après traitement laser femtoseconde. De plus, ces modifications engendrent une évolution démontrée des propriétés de mouillage qui peuvent répondre à certaines demandes industrielles. Après traitement laser femtoseconde, la surface traitée répond de différentes manières à la sollicitation en fonction de ses propriétés intrinsèques. Les expériences d’impacts localisés et de surfaces nous ont conduits à observer trois stades de modifications topographiques pour les conditions étudiées : un phénomène d’incubation, d’accumulation et d’ablation. Ce dernier a fait l’objet d’une étude plus approfondie. De manière générale, on observe deux régimes d’ablation linéaires pour l’ensemble des densités de puissance étudiées lorsque l’on étudie la profondeur d’ablation en fonction du nombre d’impulsion et le volume d’ablation en fonction de la densité de puissance cumulée. Enfin, nous montrons que les liaisons présentes en surface après traitement sont dépendantes de deux facteurs ; la densité de puissance cumulée utilisée et l’environnement de travail. Sachant que les modifications topographiques obtenues sont de types multi-échelles, les résultats ont été analysés sur la base des modèles de Wenzel (1936) et de Cassie-Baxter (1944) relatifs à la théorie du mouillage de surfaces rugueuses. Les résultats expérimentaux et leurs corrélations avec les paramètres de rugosités 3D calculés à différentes échelles ont été traités par une analyse statistique. On observe alors un comportement mixte avec un contact intime de la goutte sur les sommets des aspérités (modèle de Wenzel) et un contact hétérogène (airpolypropylène) à une échelle mésoscopique (état « fakir » décrit par le modèle de Cassie-Baxter). Toutefois, la situation où la goute repose sur le sommet des structures (CB) n’est pas toujours stable. Nous avons étudié la transition de l’état CB à l’état W par des expériences d’évaporation. On observe que cette transition est fortement dépendante de la chimie de surface dont la contribution est prépondérante sur les propriétés d’adhérence métal/PP. En contrôlant cette propriété, il est alors possible de répondre à une problématique industrielle de galvanoplastie (adhérence augmenté par le traitement laser) ou d’électroformage (adhérence faible permettant une réplication de bonne qualité des motifs)This work presents the potential of a femtosecond laser surface treatment as an alternative step of pretreatments during the metallization of polymer. To do this, the study of chemical and morphological modification induced by femtosecond laser treatment and their respective influences on the properties of adhesion and wettability of polypropylene surface are presented. A literature review highlights the feasibility of a controlled surface modification after femtosecond laser treatment of polypropylene (PP). In addition, it is known that these modifications changes the wetting properties and can be used to meet industrial applications development. After femtosecond laser treatment, the treated surface responds to the solicitation with different morphological comportment according to its intrinsic properties. Experiences of localized impacts and surfaces us to observe three stages of topographic changes to the conditions studied: an incubation phenomenon of accumulation and ablation. The ablation phenomenon is further study. Generally, two linear ablation regime is observed for all power densities examined when considering the depth of ablation as a function of the pulse number and the ablation volume according to the accumulated power density. Finally, we show that the bonds present on the surface after treatment are dependent on two factors: the accumulated power density used and the working environment. Knowing that topographic obtained is multi-scales, the results were analyzed on the basis of models Wenzel (W)(1936) and Cassie–Baxter (CB) (1944) which explain the theory of wetting of rough surfaces. The experimental results and their correlations with 3D roughness parameters calculated at different scales were treated by statistical analysis. We observe a mixed model behavior with intimate contact of the drop on the tops of the asperities (Wenzel model) and a heterogeneous contact (air - PP) in a mesoscopic scale (state " fakir " described by the Cassie -Baxter model). However, this situation where the drop sits on the top of asperities (CB) is not always the most stable. We have studied the transition between the CB state and the W state by evaporation experiments. It is observed that this transition is strongly dependent on the surface chemistry whose contribution is much greater than the adhesion properties metal / PP. If controlling this property, it is possible to obtain two industrial applications: electroplating (increased adhesion by laser treatment) or electroforming (low adherence to replicate the topography)
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Rezai, Bidakhavidi Caminde. "Nouvelles solutions de préparation et d'activation des surfaces : assemblages époxy-fonte." Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCA021/document.
Анотація:
Les revêtements organiques déposés en surface de tuyaux en fonte ductile ont pour vocation d’assurer une protection (notamment la résistance chimique, la tenue à la corrosion) vis-à-vis des effluents agressifs transportés. Pour assurer l’adhérence entre le revêtement (époxy) et son substrat, une préparation de surface est souvent nécessaire. Parmi les procédés conventionnels, le grenaillage est la solution la plus utilisée. Simple à mettre en œuvre et d’efficacité prouvée, il permet d’assurer le décapage de la surface tout en générant une rugosité adaptée. Si la solution est approuvée, des questions subsistent néanmoins quant à l’influence respective de la topographie et de la physico-chimie des surfaces. De plus, encouragées par les nouvelles réglementations environnementales, de nouvelles techniques de préparation de surface se développent.Le travail présenté s’est alors attaché à évaluer l’effet de nouvelles techniques de préparation comme le laser de structuration et le jet d’eau à ultra haute pression à comparer à d’autres procédés conventionnels tels que le brossage et le sablage. Ces nouvelles alternatives vont permettre alors de mieux comprendre l’influence du décapage et de la rugosité de surface avant la mise en peinture.Enfin, les différents résultats obtenus ont été alors spécifiquement analysés pour permettre la compréhension des phénomènes ou mécanismes d’adhésion se produisant à l’interface du couple époxy/substrat, d’un point de vue mécanique et physico-chimique. Divers moyens d’analyses ont alors pu être mis en œuvre pour caractériser les surfaces d’un point de vue morphologique (ratio de surface) et chimique (spectroscopies Raman et photoélectronique à rayons X (XPS)) pour évaluer la tenue interfaciale (test de traction adhérence)Organic coatings applied on the surface of cast iron pipes ensure very good chemical and anti-corrosion protection against aggressive effluents. To improve adherence between coating (epoxy) and substrate, a surface preparation is required. Among conventional processes shot blasting has emerged as the most efficient and cheapest solution for ensuring stripping while generating adapted roughness. However, as it may enhance both mechanical anchorage and chemical bonding a better understanding of these phenomena should be developed. Besides new eco-friendly alternatives were investigated.Indeed, new techniques were evaluated, i.e. laser structuring and an ultra-high pressure water jet whose major benefits are understanding the effect of ablation and surface roughness prior to applying a coating. Moreover, two other conventional processes (sand blasting and brushing) were introduced to obtain a various roughness.Results obtained were then analyzed to further understand bonding mechanisms at the interface.Several processes were then implemented to evaluate the surface morphology as well as the surface chemistry (spectroscopy Raman and XPS) correlated to the adhesion mechanisms
5
Pacquentin, Wilfried. "Contribution à l'étude des propriétés physico-chimiques des surfaces modifiées par traitement laser : application à l'amélioration de la résistance à la corrosion localisée des aciers inoxydables." Phd thesis, Université de Bourgogne, 2011. http://tel.archives-ouvertes.fr/tel-00676332.
Анотація:
Les matériaux métalliques sont utilisés dans des conditions de plus en plus sévères et doivent présenter une parfaite intégrité sur des périodes de plus en plus longues. L'objectif de ce travail de thèse est d'évaluer le potentiel d'un traitement de refusion laser pour améliorer la résistance à la corrosion d'un acier inoxydable de type 304L ; l'utilisation du laser dans le domaine des traitements de surface constituant un procédé en pleine évolution à cause des changements récents dans la technologie des lasers. Dans le cadre de ce travail, le choix du laser s'est porté sur un laser nano-impulsionnel à fibre dopée ytterbium dont les caractéristiques permettent la fusion quasi-instantanée sur quelques microns de la surface traitée, immédiatement suivie d'une solidification ultra-rapide avec des vitesses de refroidissement pouvant atteindre 1011 K/s. La combinaison de ces processus favorise l'élimination des défauts surfaciques, la formation de phases hors équilibre, la ségrégation d'éléments chimiques et la formation d'une nouvelle couche d'oxyde dont les propriétés sont gouvernées par les paramètres laser. Afin de les corréler avec la réactivité électrochimique de la surface, l'influence de deux paramètres laser sur les propriétés physico-chimiques de la surface a été étudiée : la puissance du laser et le taux de recouvrement des impacts laser. Pour clarifier ces relations, la résistance à la corrosion par piqûration des surfaces traitées a été déterminée par des tests électrochimiques. Pour des paramètres laser spécifiques, le potentiel de piqûration d'un acier inoxydable de type 304L augmente de plus de 500 mV traduisant ainsi une meilleure tenue à la corrosion localisée en milieu chloruré. L'interdépendance des différents phénomènes résultant du traitement laser a rendu complexe la hiérarchisation de leur effet sur la sensibilité de l'alliage testé. Cependant, il a été montré que la nature de l'oxyde thermique formé au cours de la refusion laser et ses défauts sont du premier ordre pour l'amorçage des piqûres.
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Abang, mahmod Dayang Salyani Binti. "Sintering of Zirconium Diboride-Silicon Carbide (ZrB2-SIC) and Titanium Dibor'ide-Silicon Carbide (TiB2-SIC) Ceramic Composites and Laser Surface Treatment : Application in Low Temperature Protonic Ceramic Fuel Cells (LTPCFCs)." Thesis, Limoges, 2017. http://www.theses.fr/2017LIMO0074/document.
Анотація:
Le frittage et le traitement par laser sont des techniques remarquables, couramment utilisées dans de nombreux domaines d’applications du fait des qualités qu’ils confèrent aux surfaces traitées. Ces technologies permettent de substantielles économies d’énergie comparée aux traitements de surfaces conventionnels. Le chauffage est par ailleurs, strictement localisé à la zone choisie. Notre recherche a pour objectif de développer une fine couche de verre de silice à la surface de céramiques poreusescomposites : le diborure de zirconium-carbure de silicium (ZrB2-SiC) et le diborure de titane-carbure de silicium (TiB2-SiC) frittées avec une porosité contrôlée d’environ 30%. La principale application de ces matériaux concerne les piles à combustibles protoniques fonctionnant à basse température (de type LTPCFCs). Les poudres ZrB2-SiC et TiB2-SiC sont soigneusement mélangées et pressées à froid dans un moule à la pression de 40 MPa. Le frittage naturel est conduit dans un four à 1900 et 2100 °C durant 2,5 heures, sous atmosphère contrôlée d’argon. Après polissage, le traitement de surface est effectué par laser verre-ytterbium. Les paramètres du traitement ont été optimisés (puissance et trajet du faisceau laser, temps de traitement, atmosphère) et ont permit d’obtenir une couche superficielle d’un verre à forte conduction protonique, sans affecter la structure et la composition des couches situées au-dessous de la surface. Les échantillons ont été caractérisés en utilisant les méthodes classiques : EDS, XRD, MEB, microscopie optique. Les meilleurs résultats ont été obtenus avec des échantillons de composition 61 mol. % ZrB2-SiC et 61 mol. % TiB2-SiC traités thermiquement a 1900 °C. La porosité obtenue, de l’ordre de 30%, assure une bonne circulation des gaz. La couche de verre produite sur le composite ZrB2-SiC, d’une épaisseur moyenne de 8 μm, est continue et exempte demacro fissuration. Une microfissuration est cependant détectée par MEB aux plus forts grossissements. Les essais ont été conduits à plus haute température de frittage (2100 °C) et avec des compositions différentes dans le but d’améliorer les propriétés du substrat. ZrB2-SiC. A la composition de 80 mol. % ZrB2-SiC les analyses révèlent la présence de cristaux de forme cuboïdale, attribuée à la formation de carbure de bore B4C dont la formation est admise par l’analyse thermodynamique. Les essais sur le composite ZrB2-SiC conduisent à l’apparition de bulles et de défauts dans la couche de verre. Une optimisation des conditions de traitement sera nécessaire pour contrôler ce phénomène. Cette étude démontre qu’il est possible de développer des couches poreuses de matériaux céramiques de type ZrB2-SiC, et de former à leur surface une couche de verre dense et exempte de fissuration par traitement laser. Les propriétés générales de cette couche permettent d’envisager une utilisation comme électrolyte solide dans les piles à combustibles de type LTPCFCsSintering and laser are a remarkable technology with a broad range of applications especially material processing. It offers a wide variety of desired surface properties depending on the type of usage. Sintering allows high reliability and repeatability to the large mass production. Laser benefits in the aspect of energy saving compared to conventional surface heat treatment due to the heating is restricted and localized only to the required area. Therefore, this research aims to develop a silica-glass-layer onto a porous non-oxide, Zirconium Diboride-Silicon Carbide (ZrB2-SiC) and Titanium Diboride-Silicon Carbide (TiB2-SiC) ceramic composites by sintering and laser surface treatment for potential application in the Low-Temperature Protonic Fuel Cells (LTPCFCs). ZrB2-SiC and TiB2-SiC mixed powders at different composition were cold-pressed around 40 MPa under ambient environment. Next, the composites were pressureless sintered at 1900 °C and 2100 °C for 2.5 h dwell time under argon atmosphere, respectively. The pressureless sintering was conducted by Nabertherm furnace and followed by surface treatment via an ytterbium fibre laser (Yb). Anew round spiral laser pattern was inspired, designed and scanned onto the surface of pellets to obtain a smooth glass surface layer that acted as proton-conducting (electrolyte) while preserving the beneath structures of laser-treated pellets that served as an electrode. Characterization techniques such as Scanning Electron Microscope (SEM) equipped with Energy Dispersive X-Ray Spectroscopy (EDS) and X-ray Diffraction (XRD) were performed accordingly onto the samples. Pressureless sintering of 61 mol.% ZrB2-SiC and 61 mol.% TiB2-SiC pellets at 1900 °C exhibited ca. 29% porosity. The resulting porosity was in the best range of effectiveness for gas diffusion. SEM micrographs revealed the formation of semiglassy layer on the surface of sintered 61 mol.% ZrB2-SiC pellets. The bulk structures remained unaffected and unoxidized. SEM micrographs and EDS patterns displayed thatsilica (SiO2) at a thickness of 8 μm, presence on the surface of ZrB2-SiC structures. It demonstrated that the surface treatment by Yb-fibre laser on sintered ZrB2-SiC ceramic composites at 1900 °C had accomplished. The laser surface treatment was ineffective for TiB2-SiC pellets due to several bubbles formation and crack deflection. Nevertheless, at higher magnification of the SEM for laser-treated ZrB2-SiC ceramic composites, cracks were observed. Therefore, the pressureless sintering at high temperature was conducted to improve the ZrB2-SiC structural properties. Sintering at 2100 °C had demonstrated increment of density and at 80 mol.% ZrB2-SiC sintered pellet unpredictably exhibited the presence of boron carbide (B4C) compounds. SEM micrographs revealed the dark cuboidal shapes and XRD patterns identified as B4C peaks. The reactions of B4C formation were proposed andsupported by thermodynamic analysis. In conclusion, the present research had developed a glassy layer on the surface of ZrB2-SiC ceramic composites which has potential in the application of LTPCFCs. It proved that B4C was possible to be developed by pressureless sintering at 2100 °C and it might assist in developing better morphology for ZrB2-SiC ceramic composites
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Perrin, Thibaut. "Elaboration et caractérisation de revêtements base Ni, obtenus par projection, pour outils de coupe agricoles." Thesis, Troyes, 2021. http://www.theses.fr/2021TROY0016.
Анотація:
Sous l’impulsion du développement technologique et démographique, les exploitations agricoles ont évolué et les équipements agricoles se sont perfectionnés. Les machines sont fortement sollicitées, ainsi la durabilité des outils de coupe étant des pièces d’usure est devenue un enjeu stratégique. L’application d’un revêtement Cermet (céramique-metal) est alors largement utilisée industriellement, notamment par projection flamme-poudre. Dans une optique d’amélioration de la performance des outils, cette étude vise à augmenter la résistance de ce revêtement. La technologie de rechargement laser, qui permet d’appliquer des revêtements à forte teneur en carbure dans une matrice nickel, présente un fort potentiel. Un comparatif est réalisé entre les deux technologiques de dépôt, puis, une étude paramétrique est menée sur la poudre appliquée par rechargement laser. Les effets de la composition de la matrice, de la densité apparente de la poudre de carbure de tungstène, de sa proportion massique et de sa granulométrie sur les propriétés physico – chimiques, mécaniques, tribologiques et fonctionnelles des revêtements sont étudiés. Le laser prévient la décarburation, affine la microstructure et favorise la précipitation de phases intermétalliques par rapport à la flamme sans amélioration claire de la résistance du dépôt. L’étude paramétrique a montré que l’utilisation d’une poudre de carbure dense et dure, une teneur massique en carbure de 50 % et une granulométrie fine améliore la résistance du revêtement lors des essais de frottement et de coupeDriven by technological and demographic development, farms have evolved and agricultural equipment has improved. The machines are heavily used and maintenance operations are limited. As cutting tools are wearing parts, their durability has become a strategic issue. The application of Cermet composite coating is then widely used industrially, in particular by flame-powder spraying. To improve the performance of the tools, this study aims to increase the resistance of this coating to the degradation mechanisms. The laser cladding technology which can applying coatings with high carbide content has great potential. A comparison is made between the two deposition technologies, then a parametric study is carried out on the powder applied by laser cladding. The effect of the composition of the NiCrBSi matrix, the bulk density of the tungsten carbide powder, its mass ratio and its particle size are studied on the physicochemical, mechanical, tribological and functional properties of the coatings. Laser technology prevents carbide decarburization, refines the matrix structure and promotes intermetallic phase precipitation over flame - powder spraying without a clear improvement in deposit strength. The parametric study showed that the use of a dense and hard carbide powder, a carbide mass content of 50% and a fine particle size improves the resistance of the coating during friction and cutting tests
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Sexton, Cornelius Leo. "Rapid Alloy Scanning by laser cladding." Thesis, University of Liverpool, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320605.
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Primartomo, A. "Laser surface treatment using customised heat source profiles." Thesis, Loughborough University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429008.
10
Ng, Chi-Ho. "Laser surface modification of NiTi for medical applications." Thesis, University of Chester, 2017. http://hdl.handle.net/10034/620830.
Анотація:
Regarding the higher demand of the total joint replacement (TJR) and revision surgeries in recent years, an implant material should provide much longer lifetime without failure. Nickel titanium (NiTi) is the most popular shape memory alloy in the industry, especially in medical devices due to its unique mechanical properties such as pseudo-elasticity, damping capacity, shape memory and good biocompatibility. However, concerns of nickel ion release of this alloy still exist if it is implanted for a prolonged period of time. Nickel is well known for the possibility of causing allergic response and degeneration of muscle tissue as well as being carcinogenic for the human body beyond a certain threshold. Therefore, drastically improving the surface properties (e.g. wear resistance) of NiTi is a vital step for its adoption as orthopaedic implants. To overcome the above-mentioned risks, different surface treatment techniques have been proposed and investigated, such as Physical Vapour Deposition (PVD), Chemical Vapour Deposition (CVD), ion implantation, plasma spraying, etc. Yet all of these techniques have similar limitations such as high treatment temperature, poor metallurgical bonding between coated film and substrate, and lower flexibility and efficiency. As a result, laser gas nitriding would be an ideal treatment method as it could overcome these drawbacks. Moreover, the shape memory effect and pseudo-elasticity of NiTi from a reversible phase transformation between the martensitic phase and the austenitic phase are very sensitive to heat. Hence, NiTi implant is subjected to the following provisions of the thermo-mechanical treatment process, and this implant provides desired characteristics. It is important to suggest a surface treatment, which would not disturb the original build-in properties. As a result, the low-temperature methods for substrate have to be employed on the surface of NiTi. This present study aims to investigate the feasibility of applying diffusion laser gas nitriding technique to improve the wettability and wear resistance of NiTi as well as establish the optimization technique. The current report summaries the result of laser nitrided NiTi by continuous-wave (CW) fibre laser in nitrogen environment. The microstructure, surface morphology, wettability, wear resistance of the coating layer has been analysed using scanning electron microscopy (SEM), X-ray diffractometry (XRD), sessile drop technique, 3-D profile measurement and reciprocating wear test. The resulting surface layer is free of cracks, and the wetting behaviour is better than the bare NiTi. The wear resistance of the optimised nitride sample with different hatch patterns is also evaluated using reciprocating wear testing against ultra-high-molecular-weight polyethylene (UHMWPE) in Hanks’ solution. The results indicate that the wear rates of the nitride samples and the UHMWPE counter-part were both significantly reduced. It is concluded that the diffusion laser gas nitriding is a potential low-temperature treatment technique to improve the surface properties of NiTi. This technique can be applied to a femoral head or a bone fixation plates with relatively large surface area and movable components.
Книги з теми "Laser surfaces treatment":
1
Draper, Clifton W. Laser Surface Treatment of Metals. Dordrecht: Springer Netherlands, 1986.
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ALT '94 International Conference (1994 Konstanz, Germany). ALT '94 International Conference: Laser methods of surface treatment and modification : 5-9 September 1994, Konstanz, Germany. Edited by Prokhorov A. M. 1916-, Pustovoy Vladimir, Institut obshcheĭ fiziki (Rossiĭskai͡a︡ akademii͡a︡ nauk), Universität Konstanz, and Society of Photo-optical Instrumentation Engineers. Bellingham, Wash: SPIE, 1995.
3
Yilbas, Bekir Sami. Laser Drilling: Practical Applications. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013.
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Yilbas, Bekir Sami. Laser Surface Processing and Model Studies. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013.
5
Hao, Liang. Laser surface treatment of bio-implant materials. Chichester, UK: John Wiley & Sons, 2006.
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Hao, Liang. Laser surface treatment of bio-implant materials. Hoboken, NJ: Wiley, 2005.
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Draper, Clifton W., and Paolo Mazzoldi, eds. Laser Surface Treatment of Metals. Dordrecht: Springer Netherlands, 1986. http://dx.doi.org/10.1007/978-94-009-4468-8.
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NATO Advanced Study Institute on Laser Surface Treatment of Metals (1985 San Miniato, Italy). Laser surface treatment of metals. Dordrecht: Martinus Nijhoff, 1986.
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Lindner, Gunnar. Powder feeder design for laser surface treatment. Manchester: UMIST, 1995.
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Mazumder, J. Laser Processing: Surface Treatment and Film Deposition. Dordrecht: Springer Netherlands, 1996.
Частини книг з теми "Laser surfaces treatment":
1
Ramous, E. "Carburization of Steel Surfaces by Laser Treatment." In Laser Surface Treatment of Metals, 475–82. Dordrecht: Springer Netherlands, 1986. http://dx.doi.org/10.1007/978-94-009-4468-8_41.
2
McCafferty, E., and P. G. Moore. "Electrochemical Behavior of Laser-Processed Metal Surfaces." In Laser Surface Treatment of Metals, 263–95. Dordrecht: Springer Netherlands, 1986. http://dx.doi.org/10.1007/978-94-009-4468-8_27.
3
Draper, Clifton W. "Laser Preparation of Metal Surfaces for Telecommunication Needs." In Laser Surface Treatment of Metals, 309–17. Dordrecht: Springer Netherlands, 1986. http://dx.doi.org/10.1007/978-94-009-4468-8_29.
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Helms, Aubrey L., Chih-Chen Cho, Steven L. Bernasek, Clifton W. Draper, Dale C. Jacobson, and John M. Poate. "Defect Structures on Metal Surfaces Induced by Pulsed Laser Irradiation: Characterization by Leed-Spot Profile Analysis and He+ Ion Channeling." In Laser Surface Treatment of Metals, 141–56. Dordrecht: Springer Netherlands, 1986. http://dx.doi.org/10.1007/978-94-009-4468-8_15.
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Mazumder, J. "Non-Equilibrium Synthesis by Laser for Tailored Surfaces." In Laser Processing: Surface Treatment and Film Deposition, 47–75. Dordrecht: Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-009-0197-1_3.
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Blair, K. J., J. T. Spencer, and W. M. Steen. "The use of lasers in the formation of Vitreous layers on surfaces." In Laser Processing: Surface Treatment and Film Deposition, 613–28. Dordrecht: Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-009-0197-1_31.
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Milionis, Athanasios, Roberta Ruffilli, Ilker S. Bayer, Lorenzo Dominici, Despina Fragouli, and Athanassia Athanassiou. "Local Wetting Modification on Carnauba Wax-Coated Hierarchical Surfaces by Infrared Laser Treatment." In Advances in Contact Angle, Wettability and Adhesion, 227–41. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118795620.ch13.
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Fellowes, F. C. J., and W. M. Steen. "Laser surface treatment." In Advanced Surface Coatings: a Handbook of Surface Engineering, 244–77. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3040-0_10.
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Steen, William M., and Jyotirmoy Mazumder. "Laser Surface Treatment." In Laser Material Processing, 295–347. London: Springer London, 2010. http://dx.doi.org/10.1007/978-1-84996-062-5_7.
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Steen, William M. "Laser Surface Treatment." In Laser Material Processing, 218–71. London: Springer London, 1998. http://dx.doi.org/10.1007/978-1-4471-3609-5_7.
Тези доповідей конференцій з теми "Laser surfaces treatment":
1
Iakovlev, Alexey, Julia Ruzankina, Sergey Kascheev, Oleg Vasilyev, V. Parfenov, and Alexsandr Grishkanich. "Laser anti-corrosion treatment of metal surfaces." In SPIE LASE, edited by Stefan Kaierle and Stefan W. Heinemann. SPIE, 2017. http://dx.doi.org/10.1117/12.2249953.
2
Park, Hee K., Constantine P. Grigoropoulos, and Andrew C. Tam. "Practical excimer laser-assisted cleaning of solid surfaces." In Laser Methods of Surface Treatment and Modification: ALT '94 International Conference, edited by Alexander M. Prokhorov and Vladimir I. Pustovoy. SPIE, 1995. http://dx.doi.org/10.1117/12.203633.
3
Giren, Boleslaw G., and Gerard Sliwinski. "Laser treatment of 38HMJ steel surfaces in an Ar:N2 plasma environment." In Laser Technology: Fourth Symposium, edited by Wieslaw L. Wolinski, Zdzislaw Jankiewicz, Jerzy K. Gajda, and Bohdan K. Wolczak. SPIE, 1995. http://dx.doi.org/10.1117/12.203269.
4
Badr, Y., and M. Gheith. "Spectroscopic analysis of both enamel and dentin surfaces following XeCl excimer laser surface treatment." In SPIE BiOS, edited by Peter Rechmann and Daniel Fried. SPIE, 2011. http://dx.doi.org/10.1117/12.871471.
5
Hirogaki, Toshiki, Eiichi Aoyama, Keiji Ogawa, and Shogo Matsutani. "Influence of Cu Surface Treatment on the Cu-Direct Via Hole Drilling Efficiency of PWBs." In ASME 2007 InterPACK Conference collocated with the ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ipack2007-33194.
Анотація:
This report describes the quality assessment of blind via holes (BVHs) of Printed Wiring Boards (PWBs) drilled by a CO2 laser using Cu-direct drilling. In the Cu-direct drilling method, the copper foil and the buildup layer are melted at the same time, and the surface is treated to increase the laser energy absorbed by the copper foil because an untreated copper surface reflects most of the 10.6-μm-wavelength CO2 laser beam. We used black-oxide and V-bond treatments as surface treatment. Previously, the only black-oxide treatment was paid attention to, but the new V-bond treatment is also investigated in this report. First, a straightforward method employing infrared thermography was proposed to determine the absorbance of the CO2 laser beam by the copper surface. Then, we used SEM to characterize the copper surfaces after surface treatment, and established the relationship between laser absorbance and surface shape. Subsequently, we observed the circumference of a point irradiated with the CO2 laser and explained melting processes were different from surface shape. Finally, we investigated the relationship between laser absorbance and BVH quality, and showed that a high absorbance improved BVH quality.
6
Lamaignere, Laurent, Herve Bercegol, Philippe Bouchut, Annelise During, Jerome Neauport, Herve Piombini, and Gerard Raze. "Enhanced optical damage resistance of fused silica surfaces using UV laser conditioning and CO 2 laser treatment." In High-Power Laser Ablation 2004, edited by Claude R. Phipps. SPIE, 2004. http://dx.doi.org/10.1117/12.547071.
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Chichenev, N. A. "Improving the Thermal Fatigue Strength of Hot-Working Tools by Laser Treatment." In Modern Trends in Manufacturing Technologies and Equipment. Materials Research Forum LLC, 2022. http://dx.doi.org/10.21741/9781644901755-8.
Анотація:
Abstract. A method for increasing the thermal fatigue strength of a tool used in hot forming of bearing rings by applying circular laser tracks to the working surfaces is considered. Laser treatment is carried out with a power of 2.0...2.5 kW by applying on the end face working surface of the tool in the direction from the center to the periphery of the circular tracks with a common center coinciding with the center of the circumference of the end face; the tool is rotated at a constant angular rate, the spot diameter ds for each track is selected according to the dependence ds,i+1/ds,i = 0.85...0.90, and the laser radiation spots of adjacent tracks have a common point of contact. The results of pilot testing are presented, which confirmed the high technical and economic efficiency of the use of laser quenching for ejectors and punches. A tool made by machining, for example, an ejector of an AMP-70 automatic press, is subjected to volume quenching and tempering. The ejector material was steel 3Kh3M3F, quenching temperature in oil – 1030...1050 °С, tempering temperature – 580...610 °С. After volume quenching, additional machining is carried out, usually grinding, in order to remove the decarbonized layer of material formed during heat treatment and to give the working surface the required roughness class. The final stage in the tool manufacturing is the quenching of its working surface by laser treatment. Pilot testing showed that the use of laser treatment made it possible to increase the durability of ejectors of various types by 2 ... 3 times, of deforming punches – by 2.2 times.
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Sancaktar, Erol, and Xiaoxiao Liu. "Excimer Laser Treatment of Steel Fibers for Improved Adhesion to Silicone Rubber." In ASME 2020 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/detc2020-22194.
Анотація:
Abstract Former investigators observed characteristic laser-induced structure on synthetic fibers and steel cord surfaces after irradiation, which is considered by us as an advantageous factor in developing bonding strength of fiber-elastomer composites. We applied various UV laser treatments on the surfaces of steel fiber in order to obtain similar topographic features. Surface modification was observed under scanning electron microscope (SEM). In consideration as factors in bonding strength, mechanical properties of the matrix elastomer (silicon rubber) had been tested in addition to its thermal properties by differential scanning calorimetry (DSC) and Carbon Black (CB) filler dispersion properties by atomic force microscopy (AFM). As the main test for adhesion strength, we performed a fiber pull-out test method developed by our research group for bonding strength of cord fibers to silicon rubber in both neat and CB filled forms for comparison purposes. Our experiment results revealed better adhesion strength when using silicone rubber matrix reinforced with CB.
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Campana, Giampaolo, Alessandro Ascari, and Giovanni Tani. "A Method for Laser Heat Treatment Efficiency Evaluation in Multi-Track Surface Hardening." In ASME 2009 International Manufacturing Science and Engineering Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/msec2009-84095.
Анотація:
Laser surface hardening is nowadays an industrial emerging technique, which is gradually substituting induction and flame surface hardening thanks to its advantages related to power saving and process versatility. This manufacturing technology is a challenging process especially when it has to be applied on surfaces larger than the beam spot. In this case several adjacent passes must be performed in order to scan the whole surface to be treated. This strategy involves inevitably an intrinsic tempering effect due to the re-heating of the previously hardened material. The extent of the softening occurring depends on several parameters. First of all, it depends on the material and its initial state, then on process parameters related to the laser source, such as type, optical path and spot dimension and further on the adopted surface scan strategy of the beam. This last set of process parameters is represented by: laser beam speed, number of tracks, pass overlapping degree and tracks sequence. The hardness uniformity of the heat treated layer and the consequent effectiveness of the process depend strictly on the tempering degree occurring in the material. According to this it is important to find a practical method devoted to quickly characterize the result of a laser surface treatment in terms of tempered zones extension and distribution. This article proposes, then, the definition of a “Covering Uniformity” index (CU) which represents an engineering approach to this problem and it allows to easily determine the effectiveness of a particular laser hardening treatment. The CU index is based upon hardness measurements and it is related to the ratio between the extension of the tempered zone and the total extension of the treated area. In order to underline and demonstrate the intrinsic value of this parameter a set of experimental trials was carried out on AISI 1070 carbon steel, AISI 1040 carbon steel and AISI 420B martensitic stainless steel.
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Бухтеев, Андрей Дмитриевич, Виктория Буянтуевна Бальжиева, Анна Романовна Тарасова, Фидан Гасанова, and Светлана Викторовна Агасиева. "TECHNOLOGIES FOR MANUFACTURING NANOSTRUCTURED SURFACES." In Наука. Исследования. Практика: сборник избранных статей по материалам Международной научной конференции (Санкт-Петербург, Октябрь 2020). Crossref, 2020. http://dx.doi.org/10.37539/srp293.2020.47.48.010.
Анотація:
В данной статье рассматривается применение и технологии получения наноструктурированных поверхностей. Рассмотрены такие методы как компактирование порошков (изостатическое прессование, метод Гляйтера), интенсивная пластическая деформация (угловое кручение, равноканальное угловое прессование, обработка давлением многослойных композитов) и модификация поверхности (лазерная обработка, ионная бомбардировка). This article discusses the application and technology for obtaining nano-structured surfaces. Methods such as compaction of powders (isostatic pressing, Gleiter method), severe plastic deformation (angular torsion, equal-channel angular pressing, pressure treatment of multilayer composites) and surface modification (laser treatment, ion bombardment) are considered.
Звіти організацій з теми "Laser surfaces treatment":
1
MacDonald, James D., Aharon Abeliovich, Manuel C. Lagunas-Solar, David Faiman, and John Kabshima. Treatment of Irrigation Effluent Water to Reduce Nitrogenous Contaminants and Plant Pathogens. United States Department of Agriculture, July 1993. http://dx.doi.org/10.32747/1993.7568092.bard.
Анотація:
The contamination of surface and subterranean drinking water supplies with nitrogen-laden agricultural wastewater is a problem of increasing concern in the U.S. and Israel. Through this research, we found that bacteria could utilize common organic wastes (e.g. paper, straw, cotton) as carbon sources under anaerobic conditions, and reduce nitrate concentrations in wastewater to safe levels. Two species of bacteria, Cellulomonas uda and a Comamonas sp., were required for dentitrification. Celulomonas uda degraded cellulose and reduced nitrate to nitrite. In addition, it excreted soluble organic carbon needed as a food source by the Comamonas sp. for completion of denitrification. We also found that recirculated irrigation water contains substantial amounts of fungal inoculum, and that irrigating healthy plants with such water leads to significant levels of root infection. Water can be disinfected with UV, but our experiments showed that Hg-vapor lamps do not possess sufficient energy to kill spores in wastewater containing dissolved organics. Excimer lasers and Xenon flashlamps do possess the needed power levels, but only the laser had a high enough repetition rate to reliably treat large volumes of water. Ozone was highly efficacious, but it's use as a water treatment is probably best suited to moderate or low volume irrigation systems. This research provides critical data needed for the design of effective water denitrification and/or pathogen disinfection systems for different growing operations.
2
Smoot, J. E. The Effect of Excimer Laser Treatment on the Surface Roughness and Fracture Strength of Alumina Substrates. Office of Scientific and Technical Information (OSTI), May 1998. http://dx.doi.org/10.2172/16594.
3
Chefetz, Benny, and Jon Chorover. Sorption and Mobility of Pharmaceutical Compounds in Soils Irrigated with Treated Wastewater. United States Department of Agriculture, 2006. http://dx.doi.org/10.32747/2006.7592117.bard.
Анотація:
Research into the fate of pharmaceutical compounds (PCs) in the environment has focused on aspects of removal efficiency during sewage treatment, degradation in surface water and accumulation in soils and sediments. However, very little information is available on the binding interactions of pharmaceuticals with dissolved organic matter (DOM) originating from wastewater treatment. Such interactions can significantly affect the transport potential of PCs in soils by altering compound affinity for soil particle surfaces. Our primary hypothesis is that the transport potential of PCs in soils is strongly impacted by the type and strength of interaction with DOM and the stability of resulting DOM-PC complexes. The overarching goal of the proposed work is to develop a better understanding of the risk associated with introduction of PCs into the environment with treated wastewater. This goal has been achieved by elucidating the mechanisms of the interaction of selected pharmaceuticals (that have shown to be widespread wastewater contaminants) with DOM constituents; by determining the stability and fate of DOM-PC complexes introduced to soils and soil constituents; and by evaluating the potential uptake of these compounds by plants. Based on the results obtained in this study (column and batch sorption-desorption experiments), we suggest that PCs can be classified as slow-mobile compounds in SOM-rich soil layers. When these compounds pass this layer and/or are introduced into SOM-poor soils, their mobility increases significantly. Our data suggest that in semiarid soils (consisting of low SOM), PCs can potentially be transported to the groundwater in fields irrigated with reclaimed wastewater. Moreover, the higher mobility of the acid PCs (i.e., naproxen and diclofenac) in freshwater column systems suggests that their residues in soils irrigated with reclaimed wastewater can leach from the root zone and be transported to the groundwater after rain events. Our data obtained from the binding experiments of PCs with DOM demonstrate that the hydrophobic DOM fractions were more efficient at sorbing PCs than the more polar hydrophilic fractions at a pH near the pKa of the analytes. At the pH of natural semiarid water and soil systems, including that of reclaimed wastewater and biosolids, the role of the hydrophobic fractions as sorption domains is less important than the contribution of the hydrophilic fractions. We also hypothesize that the DOM fractions interact with each other at the molecular level and do not act as independent sorption domains. In summary, our data collected in the BARD project demonstrate that the sorption abilities of the DOM fractions can also significantly affect the mobility of pharmaceutical compounds in soils influenced by intensive irrigation with treated wastewater or amended with biosolids.
4
Chefetz, Benny, and Jon Chorover. Sorption and Mobility of Pharmaceutical Compounds in Soils Irrigated with Treated Wastewater. United States Department of Agriculture, 2006. http://dx.doi.org/10.32747/2006.7709883.bard.
Анотація:
Research into the fate of pharmaceutical compounds (PCs) in the environment has focused on aspects of removal efficiency during sewage treatment, degradation in surface water and accumulation in soils and sediments. However, very little information is available on the binding interactions of pharmaceuticals with dissolved organic matter (DOM) originating from wastewater treatment. Such interactions can significantly affect the transport potential of PCs in soils by altering compound affinity for soil particle surfaces. Our primary hypothesis is that the transport potential of PCs in soils is strongly impacted by the type and strength of interaction with DOM and the stability of resulting DOM-PC complexes. The overarching goal of the proposed work is to develop a better understanding of the risk associated with introduction of PCs into the environment with treated wastewater. This goal has been achieved by elucidating the mechanisms of the interaction of selected pharmaceuticals (that have shown to be widespread wastewater contaminants) with DOM constituents; by determining the stability and fate of DOM-PC complexes introduced to soils and soil constituents; and by evaluating the potential uptake of these compounds by plants. Based on the results obtained in this study (column and batch sorption-desorption experiments), we suggest that PCs can be classified as slow-mobile compounds in SOM-rich soil layers. When these compounds pass this layer and/or are introduced into SOM-poor soils, their mobility increases significantly. Our data suggest that in semiarid soils (consisting of low SOM), PCs can potentially be transported to the groundwater in fields irrigated with reclaimed wastewater. Moreover, the higher mobility of the acid PCs (i.e., naproxen and diclofenac) in freshwater column systems suggests that their residues in soils irrigated with reclaimed wastewater can leach from the root zone and be transported to the groundwater after rain events. Our data obtained from the binding experiments of PCs with DOM demonstrate that the hydrophobic DOM fractions were more efficient at sorbing PCs than the more polar hydrophilic fractions at a pH near the pKa of the analytes. At the pH of natural semiarid water and soil systems, including that of reclaimed wastewater and biosolids, the role of the hydrophobic fractions as sorption domains is less important than the contribution of the hydrophilic fractions. We also hypothesize that the DOM fractions interact with each other at the molecular level and do not act as independent sorption domains. In summary, our data collected in the BARD project demonstrate that the sorption abilities of the DOM fractions can also significantly affect the mobility of pharmaceutical compounds in soils influenced by intensive irrigation with treated wastewater or amended with biosolids.
5
Kloepper, Joseph W., and Ilan Chet. Endophytic Bacteria of Cotton and Sweet Corn for Providing Growth Promotion and Biological Disease Control. United States Department of Agriculture, January 1996. http://dx.doi.org/10.32747/1996.7613039.bard.
Анотація:
Endophytes were isolated from 16.7% of surface-disinfested seeds and 100% of stems and roots of field-growth plants. Strains from Israel with broad-spectrum in vitro antibiosis were mainly Bacillus spp., and some were chitinolytic. Following dipping of cut cotton roots into suspensions of these strains, endophytes were detected up to 72 days later by isolation and by autoradiograms of 14C-labelled bacteria. Selected endophytes exhibited biological control potential based on significant reductions in disease severity on cotton inoculated with Rhizoctonia solani or Fusarium oxysporum f. sp. vasinfectum as well as control of Sclerotium rolfsii on bean. Neither salicylic acid nor chitinase levels increased in plants as a result of endophytic colonization, suggesting that the observed biocontrol was not accounted for by PR protein production. Some biocontrol endophytes secreted chitinolytic enzymes. Model endophytic strains inoculated into cotton stems via stem injection showed only limited movement within the stem. When introduced into stems at low concentrations, endophytes increased in population density at the injection site. After examining several experimental and semi-practical inoculation systems, seed treatment was selected as an efficient way to reintroduce most endophytes into plants.
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Droby, Samir, Michael Wisniewski, Ron Porat, and Dumitru Macarisin. Role of Reactive Oxygen Species (ROS) in Tritrophic Interactions in Postharvest Biocontrol Systems. United States Department of Agriculture, December 2012. http://dx.doi.org/10.32747/2012.7594390.bard.
Анотація:
To elucidate the role of ROS in the tri-trophic interactions in postharvest biocontrol systems a detailed molecular and biochemical investigation was undertaken. The application of the yeast biocontrol agent Metschnikowia fructicola, microarray analysis was performed on grapefruit surface wounds using an Affymetrix Citrus GeneChip. the data indicated that 1007 putative unigenes showed significant expression changes following wounding and yeast application relative to wounded controls. The expression of the genes encoding Respiratory burst oxidase (Rbo), mitogen-activated protein kinase (MAPK) and mitogen-activated protein kinase kinase (MAPKK), G-proteins, chitinase (CHI), phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS) and 4-coumarate-CoA ligase (4CL). In contrast, three genes, peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT), were down-regulated in grapefruit peel tissue treated with yeast cells. The yeast antagonists, Metschnikowia fructicola (strain 277) and Candida oleophila (strain 182) generate relatively high levels of super oxide anion (O2−) following its interaction with wounded fruit surface. Using laser scanning confocal microscopy we observed that the application of M. fructicola and C. oleophila into citrus and apple fruit wounds correlated with an increase in H2O2 accumulation in host tissue. The present data, together with our earlier discovery of the importance of H₂O₂ production in the defense response of citrus flavedo to postharvest pathogens, indicate that the yeast-induced oxidative response in fruit exocarp may be associated with the ability of specific yeast species to serve as biocontrol agents for the management of postharvest diseases. Effect of ROS on yeast cells was also studied. Pretreatment of the yeast, Candida oleophila, with 5 mM H₂O₂ for 30 min (sublethal) increased yeast tolerance to subsequent lethal levels of oxidative stress (50 mM H₂O₂), high temperature (40 °C), and low pH (pH 4). Suppression subtractive hybridization analysis was used to identify genes expressed in yeast in response to sublethal oxidative stress. Transcript levels were confirmed using semi quantitative reverse transcription-PCR. Seven antioxidant genes were up regulated. Pretreatment of the yeast antagonist Candida oleophila with glycine betaine (GB) increases oxidative stress tolerance in the microenvironment of apple wounds. ROS production is greater when yeast antagonists used as biocontrol agents are applied in the wounds. Compared to untreated control yeast cells, GB-treated cells recovered from the oxidative stress environment of apple wounds exhibited less accumulation of ROS and lower levels of oxidative damage to cellular proteins and lipids. Additionally, GB-treated yeast exhibited greater biocontrol activity against Penicillium expansum and Botrytis cinerea, and faster growth in wounds of apple fruits compared to untreated yeast. The expression of major antioxidant genes, including peroxisomal catalase, peroxiredoxin TSA1, and glutathione peroxidase was elevated in the yeast by GB treatment. A mild heat shock (HS) pretreatment (30 min at 40 1C) improved the tolerance of M. fructicola to subsequent high temperature (45 1C, 20–30 min) and oxidative stress (0.4 mol-¹) hydrogen peroxide, 20–60 min). HS-treated yeast cells showed less accumulation of reactive oxygen species (ROS) than non-treated cells in response to both stresses. Additionally, HS-treated yeast exhibited significantly greater (P≥0.0001) biocontrol activity against Penicillium expansum and a significantly faster (Po0.0001) growth rate in wounds of apple fruits stored at 25 1C compared with the performance of untreated yeast cells. Transcription of a trehalose-6-phosphate synthase gene (TPS1) was up regulated in response to HS and trehalose content also increased.