Atmospheric and Hybrid Plasma Technologies

Tuesday, April 30, 2013 2:10 PM in Room California

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2:10 PM G3-1-1 High Performance Thin Films for Aerospace Applications
Alpana Ranade, Marvi Matos (The Boeing Company, US)
The usefulness of polymer-based materials and coatings in aircraft components is two-fold. First, weight reductions are highly desirable to decrease fuel consumption and second, polymer-based materials are usually less expensive and more convenient to manufacture than alternative transparent materials such as glass. However, when used in applications with strict optical requirements, these polymeric surfaces can be susceptible to erosion which results in increased haze and decreased clarity. For example, when staple materials such as polycarbonate or stretched acrylic are used in windows, windshields, and canopies, one of the drawbacks is the tendency to scratch and craze. Polymeric windows have been historically coated with polysiloxane or polyurethane based coatings to overcome this limitation by improving the surface resistance to scratches. Still, improvements to the processes involved can decrease the required long drying times and can offer long term solutions in which the resistance to erosion is maintained overtime. Advanced thin film coatings based on Plasma Deposition Technologies can improve the durability of many components on aircrafts. These technologies can be exploited to generate materials with high performance, which are also environmentally friendly and produced with waste free processes. We are currently focusing our efforts in the development and study of thin films that improve resistance to material erosion when deposited on polymeric substrates for applications in the aerospace industry and defense.
2:30 PM G3-1-2 The Effect of Processing Parameters and Substrate Composition on the Corrosion Resistance of Plasma Electrolytic Oxidation (PEO) Coated Magnesium Alloys
Riyad Hussein, Derek Northwood, Xueyuan Nie (University of Windsor, Canada)

Magnesium alloys are considered one of the more promising materials for future use in many engineering applications. However, due to their high chemical and electrochemical reactivity, magnesium alloys have poor corrosion resistance in aqueous environments. Improving their corrosion resistance by coating can greatly extend their application. One promising coating method is plasma electrolytic oxidation (PEO). The nature of the coating formed, and the ultimate corrosion performance, depends on the both the processing parameters (electrolyte, current density, current mode, processing time) and specific Mg-alloy substrate. In the present study, PEO coatings were produced on three different Mg-alloys ( AJ62, AM60B and AZ91D) using different processing parameters. Optical Emission Spectroscopy (OES) was used to characterize the plasma species and other parameters and scanning electron microscopy and XRD were used to characterize the coatings. The corrosion resistance was evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests in an aqueous 3.5% NaCl solution. Relationships are drawn between PEO processing parameters and substrate composition and the corrosion performance.

2:50 PM G3-1-3 PVD-Quality Coatings at Atmospheric Pressure
David Ruzic, Roland Wu, Zihao Ouyang, Priya Raman, Tae Cho (University of Illinois at Urbana-Champaign, US)
PVD-Quality coatings made with a laser-assisted plasma-coating technique at atmospheric pressure (LAPCAP) for depositing thin yttria-stabilized-zirconia (YSZ) films has been developed at Illinois. This technique allows columnar-structured YSZ films with a thickness of 1~5 µm to be prepared on a Ni-based superalloy substrate at atmospheric pressure. The atmospheric pressure plasma is generated in a microwave-induced plasma torch system with a gas temperature Tg of more than 2,000 °C. A pulsed laser ablates a YSZ sample that is inside the plasma-torch plume. The ablation energy desnisty is adjusted to produce atomic flux as opposed to clusters. In this manner, deposition is atom-by-atom just as in PVD systems. Optical emission spectroscopy (OES) technique has been used to spatially analyze some critical characteristics of plasma, such as electron density (ne > 1015 cm-3), electron temperature (Te ~ 1 eV), and plasma gas temperature (Tg ~ 800-1200 °C). The thermally grown oxide (TGO) layer is found to affect the film morphology significantly, and characteristics of TGO grown by pre-heating the substrate to 800-1200 °C are investigated. TGO in the form of α-Al2O3 with a thickness of ~ 1 µm is found to provide a means to deposit high quality, adhesive thin YSZ films on substrates with columnar microstructure, same as seen in films by high-vacuum electron-beam PVD method. The morphology and characteristics of the films have been compared at various deposition temperatures (100-1200 ºC) and laser energy density (1-10 J/cm2). Aluminum Oxide of different phases were also made with plasma coating at atmospheric pressure without laser assistance using solid Aluminum cylinders and a Helium/nitrogen gas mixture, with a thickness of 1-2 µm obtained on a stainless steel substrate. The morphology of both films were analyzed using microanalysis techniques such as scanning electron microscope (SEM), focused ion beam (FIB), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The ability to make PVD-quality thin film coatings without the need for a vacuum system opens up a host of new applications which will be dicussed.
3:30 PM G3-1-5 Atmospheric Plasma Treatment Inside Hollow Substrates
Hana Baránková, Ladislav Bardos (Uppsala University, Sweden)

Atmospheric plasma treatment of surfaces brings about a number of application options including inner treatment of hollow substrates and tubes. This work describes first results of both the atmospheric plasma surface treatment and the PECVD of carbonaceous films in narrow holes and tubes with the inner diameter of about 10 mm. The experiments were carried out by the Hybrid Hollow Electrode Activated Discharge (H-HEAD) atmospheric plasma source. The air plasma column inside the steel pipe increased the surface energy within seconds which provides a better adhesion of subsequent lacquers or coatings. The PECVD was tested by carbon precursors represented be alcohol vapor or a simple LPG (Liquefied Petroleum Gas). The plasma treatment was examined by the contact angle measurements. The carbonaceous coatings were studied by SEM and Raman spectroscopy. Options and arrangements for treatments of longer and broader tubes are briefly discussed.

3:50 PM G3-1-6 ICP Dual Frequency Discharges: A Potential Tool for Large Area Plasma Processing
Anurag Mishra, TaeHyung Kim, Kyongnam Kim, Geun Yeom (Sungkyunkwan University, South Korea)

The plasma processing is being extensively used in microelectronic industry for manufacturing various electronic devices. Presently, the semiconductor industry is looking forward to move for fabrication of electronic devices at a few tens of nano-meter level. However, the device fabrication cost increases as the size of electronic device reduces. Therefore, large area wafer size is necessary to be adopted in order to improve productivity and optimize the fabrication cost of such microelectronic devices. According to a technology trend forecast, the wafer size will be 450 mm in diameter within a few years.

The most significant challenge for fabrication on a large area wafer size is to precisely control the distribution of plasma species over the substrate. Various ideas, such as segmented and gridded antennas, capacitively coupled plasmas (CCP) and very high frequency capacitively coupled plasmas (VHF-CCPs) have been proposed and implemented to achieve large area plasma sources with enhanced discharge uniformity over the substrate. Due to ability of being operated at low pressure, high plasma density, easier plasma uniformity control and the separation of discharge production and ion acceleration mechanism of the ICP sources turned the research direction towards developing and investigating the ICP sources for large area microelectronic device fabrication. However, scaling up conventional ICP sources pose some problems such as increased antenna impedance that, in turn, increase RF voltage drop across the antenna and therefore, decrease average power transfer efficiency to the discharge and produces azimuthal non-uniformity due to the standing wave effect. To overcome this issue, a novel approach of dual frequency dual antenna inductively coupled plasma (DFDA-ICP) source has been adopted. The experiments that demonstrate center to edge plasma density control, modulation of plasma parameters, electron energy distribution (EED) and Ion Energy distribution (IED) will be described in this presentation.

4:10 PM G3-1-7 Effects of Low Energy Plasma Immersion Ion Implantation of Nitrogen on Titanium
RamMohan Rao (GITAM Institute of Technology, GITAM University, India)

Plasma immersion ion implantation (PIII) of nitrogen on titanium at variable energies has been performed. The samples after metallographic polishing and ultrasonic cleaning were placed in the evacuated chamber of the implanter. The post implanted samples were subjected to X-ray diffraction and Scanning Electron Microscopic studies for the phase analysis and surface topography. After implantation a layer of titanium nitride with crystallographic orientations (111) and (200) had been formed.

Potentiodynamic polarization tests of the post implanted samples in Hank’s solution were performed. Formation of nitrides in post implanted solution showed a higher resistance to corrosion at lower implantation energy.