The impact of O/Si ratio and hydrogen content on ArF excimer laser ablation of fused silica

The impact of stoichiometry and hydrogen content on the ArF excimer laser ablation characteristics of fused silica is investigated. Nearsurface substoichiometic SiOx with x < 2 diminishes the ablation threshold as a result of increased absorption. The ablation rate is raised by an elevated hydrogen content. As confirmed by mass spectrometric analysis, the laser-induced formation of substoichiometric near-surface layers within the ablation spot sustains absorption and ablation for consecutive laser pulses

Polishing of optical media by dielectric barrier discharge inert gas plasma at atmospheric pressure

In this paper, surface smoothing of optical glasses, glass ceramic and sapphire using a low-power dielectric barrier discharge inert gas plasma at atmospheric pressure is presented. For this low temperature treatment method, no vacuum devices or chemicals are required. It is shown that by such plasma treatment the micro roughness and waviness of the investigated polished surfaces were significantly decreased, resulting in a decrease in surface scattering. Further, plasma polishing of lapped fused silica is introduced. Based on simulation results, a plasma physical process is suggested to be the underlying mechanism for initialising the observed smoothing effect

Silver nano particle formation on Ar plasma : treated cinnamyl alcohol

Metastable induced electron spectroscopy, ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy are employed to study the adsorption of silver on cinnamyl alcohol films prepared on Au(111) substrates by thermal evaporation. Additionally, the impact of an Ar atmosphere dielectric barrier discharge plasma applied to the cinnamyl alcohol film preliminary to the Ag adsorption is investigated. In both cases silver nano particles with an average diameter of 9 nm are formed. These particles do not interact chemically with the underlying cinnamyl alcohol film. We do not find any influence of the preliminary Ar plasma-treatment on the adsorption behavior at all

Impact of assisting atmospheric pressure plasma on the formation of micro- and nanoparticles during picosecond-laser ablation of titanium

In this work, we investigated the generation of particles during pure laser and plasma-assisted laser ablation of titanium. Experiments were performed using a NIR picosecond laser at a wavelength of 1030 nm and a pulse duration of 8 ps. For plasma-assisted ablation, an atmospheric pressure dielectric barrier discharge plasma was applied where the process gas was argon. Quantitative particle distributions at sizes from 10 nm to 10 μm were determined. In addition, we evaluated the amount of ablated material via laser scanning microscopy. The ablated volume was significantly increased by a factor of 2 to 3 in the case of plasma-assisted ablation, depending on the applied laser dose. It is shown that the increase in particle volume and number of particles was lower than the ablated volume. However, when applying plasma simultaneously, the generation of small nanoparticles increases notably by a factor of up to 6.63 at a laser dose of 0.7  kJ/mm² for particles with a mean diameter of 10 nm. The results suggest that even smaller particles than measurable are generated. Hence, plasma-assisted laser ablation could enhance the process efficiency, reduce the particle agglomeration, and give rise to an increase in generation of nanoparticles at the same time

Adsorption of silver on glucose studied with MIES, UPS, XPS and AFM

The adsorption behavior of silver atoms on a glucose film and their interaction was investigated by metastable induced electron spectroscopy (MIES), ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy as well as atomic force microscopy. Glucose is found to form micro droplets on gold substrates with typical diameters/dimensions of about 400 nm. The discussion of the valence band structures is carried out in comparison to various model systems. The adsorbed silver atoms on top of the glucose have been found to form silver nanoparticles that get encapsulated by a large film of glucose. Furthermore, the reduction of the glucose in the presence of these silver particles is observed. This effect is discussed with the most probable origin of the reduction being the charging by electron spectroscopy

Atmospheric pressure plasma coating of wood and MDF with polyester powder

In this study, polyester powder based on iso- and teraphthalic acid was deposited with an atmospheric plasma jet. The powder was fed into the effluent plasma zone and deposited on European beech wood (Fagus sylvatica L.), Grand fir (Abies grandis Lindl.) and medium density fiberboard (MDF). The substrates were annealed subsequent to the coating process. To exclude decomposition of the polyester layers by the plasma treatment, the surface chemistry of the layers has been examined by X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) and compared with the polyester powder reference. Furthermore, topographical investigations were carried out using laser scanning microscopy (LSM). Adhesive strength of the layers was evaluated by dolly test and gloss measurements with a goniophotometer. The deposited layers showed no chemical changes compared to the reference. The adhesive strength of the layer met practical requirements of >1 MPa. It was demonstrated that the deposition of a macroscopic layer is possible without a pretreatment or the usage of additives. Therefore this coating process by atmospheric pressure plasma for wood and wood based materials could represent an environmental-friendly alternative to conventional coating methods

Plywood made from plasma-treated veneers: Shear strength after shrinkage-swelling stress

Thermally modified and unmodified beech veneers in untreated and plasma-treated state were immersed in melamine solution at different concentrations. The plasma pre-treated veneers exhibited significantly higher melamine loads than the untreated veneers at equal impregnation duration. Subsequently the veneers were manufactured into 5-layer plywood boards; the plywood samples then underwent an extreme testing procedure based on DIN-EN 314-1/2 in order to proof the bonding quality by means of shear strength. The plywood boards made of plasma pre-treated veneers exhibited up to 2.7-fold improvement in shear strength compared to plywood made of untreated veneers. Results differed markedly based on material (unmodified/thermally modified veneer) and concentration of melamine solution

Hydrophobic recovery of atmospheric pressure plasma treated surfaces of Wood-Polymer Composites (WPC)

In this study, the behavior of atmospheric pressure plasma treated surfaces of Wood-Polymer Composites (WPC) was investigated as a function of time and environmental conditions. The surfaces of injection molded WPC based on polypropylene (PP) and polyethylene (PE) were treated by a dielectric barrier discharge (DBD) and subsequently aged under various conditions. The wettability as an indicator for change of the composite surface was assessed using water contact angle. In addition, a calculation for half-time of the contact angles was developed to predict the time span which is needed for recovery of hydrophobicity. The results showed a major influence of temperature and time, whereas the humidity only at storing conditions of 60 °C and 75% relative humidity showed a distinct effect on the activated surface. The effect of DBD treatment was stable for more than one week in the climates 20 °C and 0% RH and 20 °C and 65% RH

Comparison of three dielectric barrier discharges regarding their physical characteristics and influence on the adhesion properties on maple, high density fiberboards and wood plastic composite

In this study, three different dielectric barrier discharges, based on the same setup and run with the same power supply, are characterized by emission spectroscopy with regards to the reduced electrical field strength, and the rotational, vibrational and electron temperature. To compare discharges common for the treatment on wood, a coplanar surface barrier discharge, a direct dielectric barrier discharge and a jet system/remote plasma are chosen. To minimize influences due to the setups or power, the discharges are realized with the same electrodes and power supply and normalized to the same power. To evaluate the efficiency of the different discharges and the influence on treated materials, the surface free energy is determined on a maple wood, high density fiberboard and wood plastic composite. The influence is measured depending on the treatment time, with the highest impact in the time of 5 s