ICMCTF 2022 Session GP-ThP: Surface Engineering - Applied Research and Industrial Applications (Symposium G) Poster Session

Thin film deposition is a suitable process for textile finishing at a time when environmental protection is a global concern. Thin film technology textile treatments not only avoid the harmful chemistry and resulting hazardous waste of wet chemistry, but limit the use of chemicals, water, etc., and do not require a drying system, resulting in much lower energy consumption. Various PECVD processes have therefore been developed over the years for the textile industry to overcome wet processing’s disadvantages.

Water and oil repellent finishes are amongst the most studied treatments for fabrics. With PECVD, surface modification is carried out through plasma polymerization, which produces polymers with a higher degree of cross-linkage than conventional polymers. Moreover, these plasma processes are room temperature methods, so heat-sensitive monomers can be used. Among the commercially available precursors, short perfluoroalkyls can thus be used to impart water and oil repellency to fabrics, avoiding long-chain perfluoroalkyls which endanger the environment, human and animal life through the release of PFOAs and PFOS.

Within thin film industry, hollow cathode plasma source (HC) technology is increasingly gaining attention for PECVD. The key advantages of this technology are a high deposition rate and a good uniformity over large areas. However, HC is a high-density plasma source, appropriate for the deposition of inorganic layers, typically SiO₂, but challenging for the deposition on fabrics without modifying their bulk properties or damaging their surface.

In this work, we demonstrate the successful use of HC technology to impart water and oil repellent properties on polyolefin textiles with fluorinated and silicone precursors. The effect of parameters such as power, pressure, gas composition and flow on water and oil repellency have been evaluated according to international standards, contact angle and the film composition analysed through FTIR measurements. Water contact angles greater than 150°, i.e. superhydrophobic surface, and oil repellency grade of 4 have been obtained.

Keywords: Low-pressure, hollow cathode, plasma polymerization, water and oil repellent

Thin film thermistors with negative temperature coefficient of resistance (TCR), like Pt, are desirable for temperature-sensing applications. To achieve high sensitivity in detecting a small change in temperature, a high-quality interlayer of AlO_x is required between the SiN_x membrane and the Pt thermistor. High power impulse magnetron sputtering (HiPIMS) is known to produce high-quality thin films by generating high ionization of sputtered material which can significantly improve properties of the film over conventional sputtering techniques. In the case of reactive HiPIMS, it is important to monitor the reactive gas flow, peak current, growth rate, etc, to avoid instability in the process and control the growth of the poisoned layer on the target surface.

In this study, we investigate how target poisoning on the Al surface in the presence of oxygen can be influenced by a change in pulse length or frequency. We also show that an appropriate selection of deposition parameters can systematically provide an easier control in the reactive HiPIMS process to determine the performance of the film. The present results open the possibility of using a HiPIMS-based AlO_x interlayer in Pt/AlO_x/SiN_x thermistors for achieving a high negative TCR. Additionally, we show the role of Pt target power in enhancing the TCR of Pt/AlO_x/SiN_x.

Tetrahedral amorphous carbon (ta-C) coating is a hydrogen-free carbon coating with the remarkable properties comparable with those of diamond film, such as high hardness, optical transparency and chemical inertness. Moreover, ta-C coating can be synthesized through a relatively convenient method and has a much smoother surface, making the tribological performances of ta-C coating better than those of other diamond coatings. Among the various attempts used to prepare ta-C coatings, the filtered cathodic vacuum arc (FCVA) method is a particularly suitable technique for the mass-production of industrial ta-C coatings, and the performable properties make ta-C coatings suitable for potential commercially important components in applications such as automobile accessories, optical devices, and aerospace parts. In this study, large area ta-C coating on a 300x300mm STS plate was synthesized by single-bend filtered cathodic vacuum arc (FCVA) using in-line PVD system. Source and bend filter connecting 45° bent together were used to produce carbon plasma from a graphite target with a diameter of 50mm and a purity of 99.99%. Especially, raster magnet system was designed and constructed for large area synthesis in this source. The large area ta-C coatings with 1.8μm thickness were synthesized successfully, and thickness uniformity was showed as 92.4%. Raman spectroscopy analysis showed that the ta-C coatings had high sp3/sp2 fraction over 63%, and the hardness showed high values of 48.5 GPa. In addition, the ta-C coatings with 700nm in thickness, a sp3/sp2 fraction over 74%, and about 63 GPa hardness could be synthesized with a similar uniformity. Detailed experimental results will be presented.

Acknowledgement

This work has supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. 2021R1A2C1010058)