Mid-Infrared Resonant Ablation of PMMA

Abstract

Laser alloying using carbide forming elements (Ti, Nb, and V) was carried out to form an MCFe composite coating on a carbon steel substrate for improving wear resistance. The microstructure of laser alloyed zone was studied by OM, SEM/EDS, STEM, and XRD to reveal the effect of additional elements and laser alloying conditions on the distribution of carbides. The laser alloyed zone was found to consist of MC carbide and iron matrix. Hardness and wear properties of the laser alloyed zone were improved as compared with the laser transformation hardened sample. Dispersion of carbide within the laser alloyed zone is shown to be effective in decreasing the friction coefficient and improving wear resistance.Keywords: laser surface alloying, microstructure, metal matrix composite, carbide, steel IntroductionMetal matrix composites (MMC) that use ceramic particles for reinforcement have good toughness and wear resistance when applied to wear resistant materials such as tools and die [1]. MMCs are generally produced by a powder metallurgy or casting processes. In the powder metallurgy process, it is difficult to produce large and complex shaped components. In contrast, complex shapes can be produced using the casting process, however, it requires a lot of energy to melt a high melting temperature matrix such as iron. However, it is efficient if MMC coatings are locally formed on only the required area of low cost materials by using a laser surface modification process. Recently, a number of researchers have investigated MMC coating using laser cladding or laser surface alloying [2][3][4][5][6].Laser surface alloying is one route of producing an MMC coating on a substrate. This process consists of melting the surface of a substrate with additional materials, mixing these components, followed by rapid solidification of the mixture [7][8][9]. Advantages of this process are as follows: low thermal strain, fine microstructure, and flexibility of the choice of substrates and additional materials. MMC coatings can be produced by injection of hard particles into the molten matrix [10][11] or in-situ synthesis of hard particles in the molten pool [12][13].In this study, laser surface alloying using graphite and pure carbide forming elements such as titanium, niobium, and vanadium was carried out to form MC-Fe composite coating on carbon steel in order to improve wear resistance. Carbon steel is a typical low cost industrial material, and MC carbides such as TiC, NbC, VC, have high hardness and are chemically stable in a ferrous matrix, hence each carbide is effective for improving wear resistance [14].The issue of MMC coating by the laser surface alloying process is to control the distribution of reinforcements and to enhance the uniformity of the coating layer. In the laser

Resonant polymer ablation using a compact 3.44 μm fiber laser

“…To date, the lack of mid-IR laser sources restricted most demonstrations to non-resonant regimes, for instance near 10.6 µm. The few studies that were performed in mid-infrared resonant laser ablation regimes were conducted with complex laser systems: Bubb et al (2001) used a free-electron laser source and Naithani et al (2014) used an OPO laser source. In the demonstration reported by Naithani et al (2014), resonant laser ablation near the C-H bands was realized on PMMA with an OPO that emitted ~15 ns pulses at wavelengths from 3.20 to 3.39 μm at a repetition rate of 20 kHz and an average power of 165 mW.…”

Surface Modifications of Poly(methyl methacrylate) Induced by Controlled Electronic and Molecular Vibrational Excitation Applying Ultrafast Mid-IR Laser Radiation

“…The PMMA is excited by single-pulsed laser radiation at different wavelengths λ pump and pulse durations τ H (Table 1) at an angle of incidence θ = 0°, varying the peak fluence in the range of 0 J/cm 2 ≤ H 0 ≤ 4.5 J/cm 2 . The applied peak fluence is calculated by (11) with the pulse energy Q p , and the determined focal radius w 0 ≈ 7.5 μm of the radiation 56 on the sample surface.…”

“…Thus, the photothermal ablation after vibrational excitation may generate less radicals in the irradiated volume. The resonant excitation of polymers has been investigated at different pulse durations from a few picoseconds and nanoseconds up to a few microseconds. , However, these researchers mostly used pulse sequences and did not investigate the difference between electronic and vibrational excitation in detail.…”

Linear and Nonlinear Excitation of P3HT Induced by Spectral-Shaped Ultrafast Mid-IR Laser Radiation

“…abs gap e (7) considering the temporal evolution of the ponderomotive potential from eq 3 needed to excite the current electron density n e . The collision frequency of electrons in disordered organic materials might be smaller than in a crystalline inorganic semiconductor, 26−28 and thus the collision time is in the range of femtoseconds.…”

“…Nowadays, organic materials are applied in many electronic components, such as organic light-emitting diodes (OLEDs) or organic photovoltaic devices. − Therefore, the production of integrated circuits requires high precise processing methods, like laser structuring. , Usually, the applied laser radiation has photon energies in the eV range (UV–vis) and a sufficient high pulse energy to excite the electrons of the molecules and finally induce material ablation. A quite new approach is laser processing by resonant infrared ablation (RIA), − with photon energies in the meV range (mid-IR). Thus, the oscillating electrical field of the laser radiation can excite molecular vibrations, when the laser frequency equals one vibrational resonance.…”