Research

11 pages, 6020 KiB

Open AccessArticle

Synthesis of Optoelectronic Nanostructures on Silicon and Gold-Coated Silicon via High-Intensity Laser Pulses at Varied Pulse Durations

by Nishant Singh Jamwal and Amirkianoosh Kiani

Coatings 2023, 13(2), 375; https://doi.org/10.3390/coatings13020375 - 07 Feb 2023

Cited by 2 | Viewed by 1320

Abstract

This work defines the generation of nanostructures on silicon and gold-coated silicon substrates by tuning the pulse duration of our proposed method: ultra-short laser pulses for in situ nanostructure generation (ULPING) under ambient conditions. The method is a single-step novel method which is [...] Read more.

This work defines the generation of nanostructures on silicon and gold-coated silicon substrates by tuning the pulse duration of our proposed method: ultra-short laser pulses for in situ nanostructure generation (ULPING) under ambient conditions. The method is a single-step novel method which is efficient in synthesizing nanostructures on the substrates. We observed a higher nanofiber generation at a shorter pulse duration using Scanning Electron Microscopy (SEM) imaging. Silicon oxide formation was confirmed by Energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) analysis and a band gap of 8.19 eV was achieved for the Si + Au sample, which was determined by the Reflection Electron Energy Loss Spectroscopy (REELS) spectra. A high valence band offset of 4.93 eV was measured for the silicon-based samples for the Si/SiO₂ interface. The addition of gold nanoparticles decreased the band gap and we observed a blue shift in optical conductivity for samples with nanofibers using optical spectroscopy. Full article

(This article belongs to the Special Issue Laser Surface Treatment)

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19 pages, 35540 KiB

Open AccessArticle

Investigation into Corrosive Wear of the CoCrFeNiTa_x Laser-Clad Coatings on TC4 in the Neutral and Alkaline Circumstance

by Yanan Yan, Jun Li, Ruoliu Li, Meng Shao and Jing Li

Coatings 2023, 13(1), 105; https://doi.org/10.3390/coatings13010105 - 05 Jan 2023

Cited by 1 | Viewed by 1079

Abstract

CoCrFeNiTa_x (x = 0, 1) coatings were prepared on the surface of TC4 by laser-cladding to improve the corrosive wear property of TC4 and extend its service life in corrosive media, ultimately aiming to improve its surface performance. The effects of Ta [...] Read more.

CoCrFeNiTa_x (x = 0, 1) coatings were prepared on the surface of TC4 by laser-cladding to improve the corrosive wear property of TC4 and extend its service life in corrosive media, ultimately aiming to improve its surface performance. The effects of Ta addition on the phase constituent and microstructure of the coatings were first investigated. Given the wide application of TC4 in corrosive media (even undergoing friction), the corrosive wear of TC4 covered with the coatings was especially focused in two media (neutral and alkaline). The results showed that the coatings were composed of primary α(Ti) and eutecticum (α(Ti) + Ti₂Ni) as the matrix and TiC as the reinforcement. The introduction of Ta increased the volume fraction of eutecticum and TiC and made the microstructure more uniform. The coating with Ta performed more outstanding corrosive wear resistance than the other two samples in the two media. The wear rate of the coating with Ta was 4.7458 × 10⁻⁴ mm³·N⁻¹·m⁻¹ in the neutral environment and 6.6808 × 10⁻⁴ mm³·N⁻¹·m⁻¹ in the alkaline environment, 64.45% and 61.79% lower than those of TC4, respectively. The wear mechanism of the samples is a combination of serious micro-cutting, active dissolution, and oxidation, and the introduction of Ta effectively improved the resistance to micro-cutting. Full article

(This article belongs to the Special Issue Laser Surface Treatment)

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13 pages, 2453 KiB

Open AccessArticle

ANN Laser Hardening Quality Modeling Using Geometrical and Punctual Characterizing Approaches

by Ilyes Maamri, Noureddine Barka and Abderrazak El Ouafi

Coatings 2018, 8(6), 226; https://doi.org/10.3390/coatings8060226 - 20 Jun 2018

Cited by 3 | Viewed by 3857

Abstract

Maximum hardness and hardened depth are the responses of interest in relation to the laser hardening process. These values define heat treatment quality and have a direct impact on mechanical performance. This paper aims to develop models capable of predicting the shape of [...] Read more.

Maximum hardness and hardened depth are the responses of interest in relation to the laser hardening process. These values define heat treatment quality and have a direct impact on mechanical performance. This paper aims to develop models capable of predicting the shape of the hardness profile depending on laser process parameters for controlling laser hardening quality (LHQ), or rather the response values. An experimental study was conducted to highlight hardened profile sensitivity to process input parameters such as laser power (P_L), beam scanning speed (V_S) and initial hardness in the core (H_C). LHQ modeling was conducted by modeling attributes extracted from the hardness profile curve using two effective techniques based on the punctual and geometrical approaches. The process parameters with the most influence on the responses were laser power, beam scanning speed and initial hardness in the core. The obtained results demonstrate that the geometrical approach is more accurate and credible than the punctual approach according to performance assessment criteria. Full article

(This article belongs to the Special Issue Laser Surface Treatment)

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17 pages, 3585 KiB

Open AccessArticle

Thermo-Mechanical Finite Element Modeling of the Laser Treatment of Titanium Cold-Sprayed Coatings

by Felice Rubino, Antonello Astarita and Pierpaolo Carlone

Coatings 2018, 8(6), 219; https://doi.org/10.3390/coatings8060219 - 12 Jun 2018

Cited by 15 | Viewed by 4470

Abstract

This paper implements a thermo-mechanical model to simulate the laser treatment effects on a cold-sprayed titanium coating and aluminum substrate. The thermo-mechanical finite element model considers the transient temperature field due to the laser source and applied boundary conditions, using them as input [...] Read more.

This paper implements a thermo-mechanical model to simulate the laser treatment effects on a cold-sprayed titanium coating and aluminum substrate. The thermo-mechanical finite element model considers the transient temperature field due to the laser source and applied boundary conditions, using them as input loads for the subsequent stress-strain analysis. Numerical outcomes highlighted the relevance of thermal gradients and the presence of thermally-induced stress-strain fields responsible for promoting damage in the coating. Full article

(This article belongs to the Special Issue Laser Surface Treatment)

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11 pages, 3019 KiB

Open AccessShort Note

An Analysis of Effect of CO₂ Laser Treatment on Carbon Fibre Fabric

by Yu-de Liou, Kam-hong Chau, Chi-yuen Hui, Ju-liang He, Yin-ling Lam and Chi-wai Kan

Coatings 2018, 8(5), 178; https://doi.org/10.3390/coatings8050178 - 06 May 2018

Cited by 4 | Viewed by 4415

Abstract

The colour of carbon fibre fabric is black which limits its aesthetic properties. CO₂ laser has been used for cutting carbon fibres. The impact of CO₂ laser treatment to modify the surface of carbon fibre fabric is investigated in this work. [...] Read more.

The colour of carbon fibre fabric is black which limits its aesthetic properties. CO₂ laser has been used for cutting carbon fibres. The impact of CO₂ laser treatment to modify the surface of carbon fibre fabric is investigated in this work. Different combinations of laser process parameters, i.e., pixel time (110, 120, 130, 140, 150, 160, 170, 180, 190 and 200 µs, with 10 µs intervals) and resolution (70, 80, 90 and 100 dpi (dots per inch), with 10 dpi intervals), were used for treating carbon fibre fabric surface. Since the laser process is a surface treatment, contact angle measurement was used for evaluating the wetting property imparted after laser processing. The resistivity of the laser-treated carbon fibre fabric was measured to evaluate any effect on the original electrical property of the carbon fibre fabric. Moreover, surface morphology and functionality of laser-treated carbon fibre fabric were assessed by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy-attenuated total internal reflectance (FTIR-ATR), respectively. SEM assessment was to examine the physical change in the carbon fibre surface after laser processing. On the other hand, the FTIR-ATR measurement can help to evaluate the chemical change in the carbon fibre surface after laser processing. Full article

(This article belongs to the Special Issue Laser Surface Treatment)

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13 pages, 61489 KiB

Open AccessEditor’s ChoiceArticle

Effects of Laser Microtexturing on the Wetting Behavior of Ti6Al4V Alloy

by Juan Manuel Vazquez-Martinez, Jorge Salguero Gomez, Pedro Francisco Mayuet Ares, Severo Raul Fernandez-Vidal and Moises Batista Ponce

Coatings 2018, 8(4), 145; https://doi.org/10.3390/coatings8040145 - 17 Apr 2018

Cited by 16 | Viewed by 4510

Abstract

Surface modification procedures by laser techniques allow the generation of specific topographies and microstructures that enable the adaptation of the external layers of materials for specific applications. In laser texturing processes, it is possible to maintain control over the microgeometry and dimensions of [...] Read more.

Surface modification procedures by laser techniques allow the generation of specific topographies and microstructures that enable the adaptation of the external layers of materials for specific applications. In laser texturing processes, it is possible to maintain control over the microgeometry and dimensions of the surface pattern through varying the processing parameters. One of the main areas of interest in the field of surface modification treatments is the ability to generate topographies that are associated with specific surface finishes, in terms of roughness, that can improve the manufactured part’s functional capabilities. In this aspect, several types of phenomena have been detected, such as the friction and sliding wear behavior or wetting capacity, which maintain a high dependence on surface roughness. In this research, surface texturing treatments have been developed by laser techniques through using the scanning speed of the beam (V_s) as a control parameter in order to generate samples that have topographies with different natures. Through assessments of surface finish using specialized techniques, the dimensional and geometrical features of the texturized tracks have been characterized, analyzing their influence on the wetting behavior of the irradiated layer. In this way, more defined texturing grooves has been developed by increasing the V_s, which also improves the hydrophobic characteristics of the treated surface. However, due to the lack of uniformity in the solidification process of the irradiated area, some deviations from the expected trends and singular points can be observed. Using the contact angle method to evaluate the wetting behavior of the applied treatments found increases in the contact angle values for high texturing speeds, finding a maximum value of 65.59° for V_s = 200 mm/s. Full article

(This article belongs to the Special Issue Laser Surface Treatment)

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11 pages, 20349 KiB

Open AccessArticle

Effects of V and Cr on Laser Cladded Fe-Based Coatings

by Haiyang Wang, Song Zhang, Chunhua Zhang, Chenliang Wu, Jingbo Zhang and Adil O. Abdullah

Coatings 2018, 8(3), 107; https://doi.org/10.3390/coatings8030107 - 15 Mar 2018

Cited by 21 | Viewed by 4656

Abstract

Fe-based coatings with high V and Cr content were obtained by laser cladding using Fe-based powder with different Cr₃C₂ and FeV₅₀ content. The results showed that Fe-based coatings were uniform and dense. The constituent phases were mainly composed of [...] Read more.

Fe-based coatings with high V and Cr content were obtained by laser cladding using Fe-based powder with different Cr₃C₂ and FeV₅₀ content. The results showed that Fe-based coatings were uniform and dense. The constituent phases were mainly composed of α-Fe solid solution with the increase of Cr₃C₂ and FeV₅₀, γ-Fe and V₈C₇ phases were achieved. The microstructure of the coatings exhibited a typical dendrite structure. The concentration of C, V and Cr were saturated in dendritic areas, and the other alloying elements were mainly dissolved in the interdendritic areas. The hardness and wear resistance of Fe-based coatings were enhanced with the Cr₃C₂ and FeV₅₀ addition. The specimen with 15% Cr₃C₂ and 16% FeV50 had the highest hardness of 66.1 ± 0.6 HRC, which was 1.05 times higher than the sample with 4.5% Cr₃C₂ and 5% FeV₅₀, and the wear resistance of the former was three times greater than the latter. Full article

(This article belongs to the Special Issue Laser Surface Treatment)

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19 pages, 19940 KiB

Open AccessArticle

Effect of Laser Remelting Power on Immersion Corrosion of Amorphous Al–Ti–Ni Coatings

by Haixiang Chen and Dejun Kong

Coatings 2018, 8(2), 46; https://doi.org/10.3390/coatings8020046 - 25 Jan 2018

Cited by 4 | Viewed by 4390

Abstract

An arc-sprayed amorphous Al–Ti–Ni coating on S355 structural steel was processed by laser remelting (LR) at powers of 600, 800, and 1000 W. The surface-cross-sectional morphologies, chemical element distributions, and phase compositions of the as-obtained Al–Ti–Ni coatings were analyzed using a scanning electron [...] Read more.

An arc-sprayed amorphous Al–Ti–Ni coating on S355 structural steel was processed by laser remelting (LR) at powers of 600, 800, and 1000 W. The surface-cross-sectional morphologies, chemical element distributions, and phase compositions of the as-obtained Al–Ti–Ni coatings were analyzed using a scanning electron microscope (SEM), energy-dispersive spectrometer (EDS), and X-ray diffractometer (XRD), respectively. The immersion corrosion tests of Al–Ti–Ni coatings in 3.5% NaCl solution for 720 h were performed to investigate the effects of LR power on their immersion corrosion behaviors. The test results show that the amorphous Al–Ti–Ni coatings form good metallurgical bonding with the substrate after LR. The AlNi, Al₃Ti, Al₃Ni₂, Ti₃O₅, and Al₂O₃ amorphous phases are detected in the Al–Ti–Ni coatings after LR. The corrosion potentials of Al–Ti–Ni coatings after LR show a positive shift relative to that of S355 steel, implying that the corrosion resistance of Al–Ti–Ni coatings was superior to that of S355 steel. A dense protective Al₂O₃ film is formed on the Al–Ti–Ni coating surface at an LR power of 1000 W, at which power the highest corrosion potential of −0.233 V is observed. The corrosion mechanisms of Al–Ti–Ni coating at the LR power of 1000 W are uniform corrosion and pitting corrosion, while those of Al–Ti–Ni coatings at the LR powers of 600 and 800 W are localized corrosion and pitting corrosion. The corrosion resistance of Al–Ti–Ni coating with the LR power of 1000 W is better than those at the LR powers of 600 and 800 W, effectively improving the corrosion resistance of S355 steel. Full article

(This article belongs to the Special Issue Laser Surface Treatment)

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3638 KiB

Open AccessArticle

A Study of CO₂ Laser Treatment on Colour Properties of Cotton-Based Fabrics

by On-na Hung and Chi-wai Kan

Coatings 2017, 7(8), 131; https://doi.org/10.3390/coatings7080131 - 20 Aug 2017

Cited by 7 | Viewed by 4406

Abstract

In this study, laser was applied to two types of cotton-based woven fabrics in order to study the effect of CO₂ laser technology on colour and fabric strength properties. The woven fabrics had different fibre compositions, i.e., one was 100% cotton while [...] Read more.

In this study, laser was applied to two types of cotton-based woven fabrics in order to study the effect of CO₂ laser technology on colour and fabric strength properties. The woven fabrics had different fibre compositions, i.e., one was 100% cotton while the other had 60% cotton blended with 40% polyester. They were treated with different combinations of laser processing parameters, i.e., resolution (52, 60, and 68 dpi) and pixel time (110, 120, 130, and 140 μs). There were two approaches adopted: (1) laser treated and then dyed (LD); and (2) first dyed and then laser treated (DL), in order to study the effects of the two different sequences on the resultant colour. Colour properties include reflectance value, colour yield, CIE L*a*b* values and levelness measured by spectrophotometer; pH value and tensile strength were also measured. It was discovered that laser treatment had no influence on chromaticity of cotton fabrics. Moreover, fabrics treated with laser had a lighter shade than the control samples. This confirmed that both approaches, i.e., laser treatment conducted before and after dyeing, can provide a colour fading effect. The tensile strength of fabrics was affected differently in relation to the dyeing and laser process. According to results obtained from the pH measurement, it is confirmed that laser treatment can provide a colour fading effect without affecting the pH value, and the fabrics can be used instantly right after the laser treatment. Full article

(This article belongs to the Special Issue Laser Surface Treatment)

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6340 KiB

Open AccessArticle

Optimization of the Laser Hardening Process by Adapting the Intensity Distribution to Generate a Top-hat Temperature Distribution Using Freeform Optics

by Fritz Klocke, Martin Schulz and Stefan Gräfe

Coatings 2017, 7(6), 77; https://doi.org/10.3390/coatings7060077 - 07 Jun 2017

Cited by 33 | Viewed by 8576

Abstract

Laser hardening is a surface hardening process which enables high quality results due to the controllability of the energy input. The hardened area is determined by the heat distribution caused by the intensity profile of the laser beam. However, commonly used top-hat laser [...] Read more.

Laser hardening is a surface hardening process which enables high quality results due to the controllability of the energy input. The hardened area is determined by the heat distribution caused by the intensity profile of the laser beam. However, commonly used top-hat laser beams do not provide an ideal temperature profile. Therefore, in this paper the beam profile, and thus the temperature profile, is optimized using freeform optics. The intensity distribution is modified to generate a top-hat temperature profile on the surface. The results of laser hardening with the optimized distribution are thereupon compared with results using a top-hat intensity distribution. Full article

(This article belongs to the Special Issue Laser Surface Treatment)

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