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Effect of Beam Parameters on Femtosecond Laser Induced Surface Structures on Titanium and Copper.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Effect of Beam Parameters on Femtosecond Laser Induced Surface Structures on Titanium and Copper.
Author:	Biswas, Sanchari.
Published:	Ann Arbor : ProQuest Dissertations & Theses, 2020
Description:	103 p.
Notes:	Source: Dissertations Abstracts International, Volume: 82-05, Section: B.
Notes:	Advisor: Kietzig, Anne-Marie.
Contained By:	Dissertations Abstracts International82-05B.
Subject:	Chemical engineering.
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28267027
ISBN:	9798691248047

Effect of Beam Parameters on Femtosecond Laser Induced Surface Structures on Titanium and Copper.
Biswas, Sanchari.

Effect of Beam Parameters on Femtosecond Laser Induced Surface Structures on Titanium and Copper. - Ann Arbor : ProQuest Dissertations & Theses, 2020 - 103 p.

Source: Dissertations Abstracts International, Volume: 82-05, Section: B.

Thesis (Ph.D.)--McGill University (Canada), 2020.

This item must not be sold to any third party vendors.

Femtosecond (fs) laser micromachining has the ability to impart a large variety of hierarchical microstructures in a single processing step on all types of materials, under any ambient condition and without the requirement of clean room or high vacuum facilities. Thereby with years, fs laser micromachining has become an emergent surface engineering technique. Since the nature of the micromachining outcome strongly depends on several micromachining parameters, in order to exercise control over the machining outcome, it is desirable to understand how these parameters influence surface structure formation. However, the major focus of existing research has been on understanding the effects of micromachining parameters on single or multiple pulse ablation threshold with limited discussion on structure formation. Furthermore, most reports discuss the effect of parameters such as the fluence, or scan velocity or number of scans. Again, limited reports exist that outline the effect of laser beam parameters such as the pulse repetition rate and the laser irradiation wavelength. This thesis aims to show the effect of the beam parameters (the repetition rate and irradiation wavelength) on structure formation in pursuit of bridging the gaps in literature.To analyze the effect of repetition rate, structures resulting from micromachining metallic samples, titanium (Ti) and copper (Cu), at 1 and 10 kHz repetition rate were compared. It was discovered that the effect of repetition rate on the structure thresholds strongly depend on the material properties such as the electron-phonon (e-ph) coupling constant and the thermal conductivity (k). On Cu, the structure thresholds decreased whereas on Ti the structure thresholds increased with the increase in repetition rate. This opposing trend was attributed to the opposing material characteristic and the resultant melt dynamics. When machining Ti at 10 kHz, the melt layer induced by one laser pulse persists until the next pulse arrives. The melt layer acts as a dielectric for the subsequent pulse, thereby increasing the structure thresholds. On Cu, however, the melt layer quickly resolidifies, and no such dielectric-like phase is observed.Additionally, the effect of repetition rate on surface texture was carried out through lacunarity analysis. Structures on both metals that were fabricated at relatively lower fluence had higher lacunarity when micromachined at 10 kHz. On the contrary, structures that were fabricated at higher fluence had higher lacunarity when micromachined at 1 kHz.Next, the effect of irradiation wavelength on structure formation was examined. Ti and Cu samples were micromachined at four different wavelengths in the UV-Vis-IR range (275 nm, 400 nm, 800 nm and 1200 nm). This conveniently allowed to map the structure evolution along the entire wavelength spectrum. The effect of irradiation wavelength on the structure thresholds was also determined. It was discovered that the structure thresholds strongly depend on the material's absorbance spectra. Interestingly, in contrast to results from single spot ablation where a positive correlation is found between the ablation threshold and wavelength, our results for the structure thresholds rather demonstrate a negative correlation with a material's absorbance across the wavelength spectrum.Additionally, several other new surface structures were fabricated and reported for the first time, among which the formation mechanism of ‘aggregate’ structures, one of the new surface structures, is presented in this thesis.Altogether, this thesis contributes to the current knowledge on the (fs) laser-material interaction in the direct (fs) laser micromachining technique by addressing the gaps that exist in determining the effect of laser beam parameters on the micromachining outcome.

ISBN: 9798691248047Subjects--Topical Terms:

206267
Chemical engineering.
Subjects--Index Terms:

Femtosecond laser micromachining

Effect of Beam Parameters on Femtosecond Laser Induced Surface Structures on Titanium and Copper.
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100 1 $a Biswas, Sanchari. $3 886718
245 1 0 $a Effect of Beam Parameters on Femtosecond Laser Induced Surface Structures on Titanium and Copper.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2020
300 $a 103 p.
500 $a Source: Dissertations Abstracts International, Volume: 82-05, Section: B.
500 $a Advisor: Kietzig, Anne-Marie.
502 $a Thesis (Ph.D.)--McGill University (Canada), 2020.
506 $a This item must not be sold to any third party vendors.
520 $a Femtosecond (fs) laser micromachining has the ability to impart a large variety of hierarchical microstructures in a single processing step on all types of materials, under any ambient condition and without the requirement of clean room or high vacuum facilities. Thereby with years, fs laser micromachining has become an emergent surface engineering technique. Since the nature of the micromachining outcome strongly depends on several micromachining parameters, in order to exercise control over the machining outcome, it is desirable to understand how these parameters influence surface structure formation. However, the major focus of existing research has been on understanding the effects of micromachining parameters on single or multiple pulse ablation threshold with limited discussion on structure formation. Furthermore, most reports discuss the effect of parameters such as the fluence, or scan velocity or number of scans. Again, limited reports exist that outline the effect of laser beam parameters such as the pulse repetition rate and the laser irradiation wavelength. This thesis aims to show the effect of the beam parameters (the repetition rate and irradiation wavelength) on structure formation in pursuit of bridging the gaps in literature.To analyze the effect of repetition rate, structures resulting from micromachining metallic samples, titanium (Ti) and copper (Cu), at 1 and 10 kHz repetition rate were compared. It was discovered that the effect of repetition rate on the structure thresholds strongly depend on the material properties such as the electron-phonon (e-ph) coupling constant and the thermal conductivity (k). On Cu, the structure thresholds decreased whereas on Ti the structure thresholds increased with the increase in repetition rate. This opposing trend was attributed to the opposing material characteristic and the resultant melt dynamics. When machining Ti at 10 kHz, the melt layer induced by one laser pulse persists until the next pulse arrives. The melt layer acts as a dielectric for the subsequent pulse, thereby increasing the structure thresholds. On Cu, however, the melt layer quickly resolidifies, and no such dielectric-like phase is observed.Additionally, the effect of repetition rate on surface texture was carried out through lacunarity analysis. Structures on both metals that were fabricated at relatively lower fluence had higher lacunarity when micromachined at 10 kHz. On the contrary, structures that were fabricated at higher fluence had higher lacunarity when micromachined at 1 kHz.Next, the effect of irradiation wavelength on structure formation was examined. Ti and Cu samples were micromachined at four different wavelengths in the UV-Vis-IR range (275 nm, 400 nm, 800 nm and 1200 nm). This conveniently allowed to map the structure evolution along the entire wavelength spectrum. The effect of irradiation wavelength on the structure thresholds was also determined. It was discovered that the structure thresholds strongly depend on the material's absorbance spectra. Interestingly, in contrast to results from single spot ablation where a positive correlation is found between the ablation threshold and wavelength, our results for the structure thresholds rather demonstrate a negative correlation with a material's absorbance across the wavelength spectrum.Additionally, several other new surface structures were fabricated and reported for the first time, among which the formation mechanism of ‘aggregate’ structures, one of the new surface structures, is presented in this thesis.Altogether, this thesis contributes to the current knowledge on the (fs) laser-material interaction in the direct (fs) laser micromachining technique by addressing the gaps that exist in determining the effect of laser beam parameters on the micromachining outcome.
520 $a Le micro-usinage au laser femtoseconde (fs) est capable de creer une grande variete de microstructures hierarchiques en une seule etape sur tout type de materiaux, en toutes conditions, et sans avoir recours a un environnement sous-vide ou a des salles blanches. Ainsi, au long des annees, le micro-usinage au laser femtoseconde est devenu une technique emergente d’ingenierie de surface. Puisque le resultat du micro-usinage depend de plusieurs parametres, pour exercer plus de controle sur le resultat, il est desirable de comprendre comment ces parametres influencent la formation de structures de surface. Cependant, jusqu’a present, la majorite des etudes s’est concentre sur la comprehension des effets des parametres de micro-usinage sur le seuil d’ablation avec une analyse limitee de la formation de structures. De plus, une grande partie des etudes se concentre sur l’effet des parametres telle la fluence, la vitesse du balayage ou le nombre de balayages. Encore, peu d’analyses qui se concernent avec les effets des parametres du rayon laser tel la frequence et la longueur d’onde existent. Cette these a pour objectif de montrer les effets des parametres du rayon laser sur la formation de structures afin d’adresser les lacunes qui existent presentement.Afin d’analyser l’effet de la frequence, des structures creees par micro-usinage de surface metalliques, a base de titane (Ti) et cuivre (Cu), a 1 et 10 kHz ont ete comparees. Il a ete decouvert que l’effet de la frequence sur le seuil de formation des structures depend fortement des proprietes des materiaux telle la constante de couplage electron-phonon (e-ph) et la conductivite thermique (k). Sur le cuivre, les seuils de formation de structures ont baisse tandis que sur le titane les seuils de formation ont augmente en fonction de la frequence. Cette opposition a ete attribuee aux differentes proprietes des materiaux et a la dynamique de fusion qui en derive. Par micro-usinage du Ti a 10 kHz, la couche en fusion creee par une impulsion laser persiste jusqu’a l’arrivee de l’impulsion suivante. Cette couche agit comme un materiau dielectrique vis-a-vis de l’impulsion suivante, et ainsi augmente le seuil de formation de structures. Cependant, sur le Cu, la couche en fusion est rapidement resolidifiee, et aucune phase dielectrique n’est observee.De plus, l’effet de la frequence sur la texture de surface a ete etudie par analyse lacunaire. Les structures sur les deux metaux qui ont ete fabriquees a des fluences relativement basses ont des lacunarites plus elevees apres fabrication a 10 kHz. Au contraire, les structures fabriquees a des fluences plus elevees ont des lacunarites plus elevees apres fabrication a 1 kHz.Ensuite, l’effet de la longueur d’onde sur la formation de structures a ete examine. Des echantillons de Ti et Cu ont ete micro-usines a quatre longueurs d’onde differentes dans le domaine UV-VIS-IR (275 nm, 400 nm, 800 nm, et 1200 nm). Ceci a permit d’enregistrer l’evolution des structures sur tout le long du spectre de longueurs d’onde. L’effet de la longueur d’onde sur le seuil de formation des structures a aussi ete determine. Il a ete decouvert que le seuil de formation de structures depend fortement du spectre d’absorption du materiau. Interessement, en contraste avec les resultats d’ablation a impulsion unique ou une correlation positive est observee entre le seuil d’ablation et la longueur d’onde, nos resultats pour le seuil de formation de structures demontrent une correlation negative avec l’absorption du materiau tout au long du spectre de longueur d’ondes.En somme, cette these contribue au savoir actuel concernant les interactions entre les lasers fs et les materiaux en adressant les lacunes qui existent en ce qui concerne l’effet des parametres des rayons laser sur les resultats de micro-usinage.
590 $a School code: 0781.
650 4 $a Chemical engineering. $3 206267
653 $a Femtosecond laser micromachining
653 $a Micromachining metallic samples
653 $a Electron-phonon coupling constant
653 $a Thermal conductivity
690 $a 0542
710 2 $a McGill University (Canada). $3 531188
773 0 $t Dissertations Abstracts International $g 82-05B.
790 $a 0781
791 $a Ph.D.
792 $a 2020
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856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28267027