Joanna Maria Drews

Ultrasound enhanced plasma surface modification at atmospheric pressure

Abstract Efficiency of atmospheric pressure plasma treatment can be highly enhanced by simultaneous high power ultrasonic irradiation onto the treating surface. It is because ultrasonic waves with a sound pressure level (SPL) above ∼140 dB can reduce the thickness of a boundary gas layer between the plasma and the material surface, and thus, many reactive species generated in the plasma can reach the surface before they are inactivated and can be efficiently utilised for surface modification. In the present work, glass fibre reinforced polyester plates were treated using a dielectric barrier discharge and a gliding arc at atmospheric pressure to study adhesion improvement. The effect of ultrasonic irradiation with the frequency diapason between 20 and 40 kHz at the SPL of ∼150 dB was investigated. After the plasma treatment without ultrasonic irradiation, the wettability was significantly improved. The ultrasonic irradiation during the plasma treatment consistently enhanced the treatment efficiency. The principal effect of ultrasonic irradiation can be attributed to enhancing surface oxidation during plasma treatment. In addition, ultrasonic irradiation can suppress arcing, and the uniformity of the treatment can be improved.

Ultrasound Enhanced Plasma Treatment of Glass-Fibre-Reinforced Polyester in Atmospheric Pressure Air for Adhesion Improvement

A glass-fibre-reinforced polyester (GFRP) plate was treated with dielectric barrier discharge (DBD) at atmospheric pressure in air for adhesion improvement. The effects of ultrasonic irradiation using a high-power gas-jet generator during the treatment were investigated. The optical emission spectrum of the discharge remained almost unchanged by the ultrasonic irradiation, indicating that the bulk property of the discharge was not significantly influenced by the ultrasound. However, the ultrasonic irradiation during the plasma treatment suppressed occasional arcing in the DBD, preventing damage of the GFRP plates. The polar component of the surface energy of the polyester plate was 21 mJ/m2 before the treatment, increased markedly to 52 mJ/m2 after 2-s plasma treatment without ultrasonic irradiation, and further increased slightly after longer treatments. In addition, the polar component of the surface energy increased due to the simultaneous ultrasonic irradiation, indicating that the adhesive property would be further improved. This result shows a good agreement with surface characterization by X-ray photoelectron spectroscopy. Time-of-flight secondary ion mass spectrometry ion images show that nitrogen-containing functional groups were uniformly attached after the treatments. The roughness of the GFRP surfaces increased after the plasma treatment, but the ultrasonic irradiation did not enhance surface roughening.

Plasma polymerized thin films of maleic anhydride and 1,2-methylenedioxybenzene for improving adhesion to carbon surfaces

Low power 2-phase AC plasma polymerization has been used to surface modify glassy carbon substrates that are used as an experimental model for carbon fibers in reinforced composites. In order to probe the role of carboxylic acid density on the interfacial adhesion strength a combination of different plasma powers and monomer compositions was used. Maleic anhydride (MAH) and 1,2-methylenedioxybenzene (MDOB) were plasma deposited separately and as mixtures to create layers with different surface compositions. In all cases the MAH was hydrolyzed to form carboxylic acid groups. Some carboxylic acid are present on the MDOB surface as a result of the fragmentation processes in the plasma. Chemical and physical changes were investigated as a function of plasma power at constant polymerization time. Surface chemistry analysis was performed with x-ray photoelectron spectroscopy and attenuated total veflectance Fourier transform infrared spectroscopy. Atomic force microscopy was used to measure the thickness of the...

Ozone Production in a Dielectric Barrier Discharge with Ultrasonic Irradiation

Ozone production has been investigated using an atmospheric pressure dielectric barrier discharge in pure O2 at room temperature with and without ultrasonic irradiation. It was driven at a frequency of either 15 kHz or ∼40 kHz. The ozone production was highly dependent on the O2 flow rate and the discharge power. Furthermore, powerful ultrasonic irradiation at a fundamental frequency of ∼30 kHz with the sound pressure level of ∼150 dB into the discharge can improve the ozone production efficiency, particularly when operated at the frequency of 15 kHz at the flow rate of 15 L/min.

Influence of ultrasonic irradiation on ozone generation in a dielectric barrier discharge

An atmospheric pressure dielectric barrier discharge (DBD) was generated in an N2/O2 gas mixture at room temperature with and without ultrasonic irradiation to investigate ozone production. Powerful ultrasonic irradiation with the sound pressure level of approximately 150 dB into the DBD can enhance ozone production especially when the DBD was driven at a frequency of 15 kHz.

Nanostructured Materials in Different Dimensions for Sensing Applications

Future sensing elements should be more specific, more sensitive, more reversible, and faster than today’s elements. These future sensing devices will either be integrated with suitable signal detection circuitry, typically based on Si microelectronics, or with optical signal detection, and finally interfaced to relevant state-of-the-art signal recognition hard- and software. Some of the more critical uses of sensors are in the dynamic surveillance of system parameters in complex machinery or in biological systems, such as our own bodies. Most of these demands are likely to be met by the continued rapid development of functional nanomaterials including bio-nanomaterials and biocompatible nanomaterials. A strong and increasing trend, also clear at this NATO-ASI, is the focus on using Au-dots deposited on various substrates for optical field enhancements and for other synergistic effects on electronic properties such as sheet conductivity, when deposited on polymer films or on metal oxide surfaces. Gas sensing with metal oxide surfaces is another very active area of development, where the high surface to volume ratio of thin films or nano-crystalline objects are in focus. In this report we demonstrate examples of the processing of silicon surfaces, aluminum surfaces and wooden saw dust powders to create nanostructured materials with interesting functional properties in novel types of self-limiting and self-organizing growths of one-, two- and three dimensional nano-template (i.e. nano-building block) systems, with a range of functionalities, as-formed, or after further integration. However, the focus in this report is on the growth processes and further treatments, as these are relatively new, and thus not widely known, but highly relevant for the functional properties of the resulting nanostructures, and for integration of the structures with silicon or in more complex systems.