研究目的
To produce Diamond-like carbon (DLC) film on the internal surface of a long metal tube using the pulsed-DC PECVD deposition system and study the features of plasma discharges, temperature distribution, and DLC film deposition inside the tube.
研究成果
The study demonstrated the feasibility of using a pulsed-DC PECVD deposition system to produce DLC film on the internal surface of a long metal tube. The results indicated plasma discharge stability inside the tube, with the DLC film growth rate and structure properties varying along the axial direction of the tube. Surfaces of DLC film with high sp3 content provided better tribological characteristics, attributed to complex processes of local dissociation and activation.
研究不足
The study was limited by the technical constraints of the pulsed-DC PECVD deposition system and the challenges of coating the inner surface of long tubes. The temperature rise caused by the bombardment of ions, radicals, and electrons cannot be ignored during the PECVD process, and temperatures above 300 oC are generally unfavorable to DLC film growth due to a rapid graphitization process.
1：Experimental Design and Method Selection
The study used a pulsed-DC PECVD deposition system to produce DLC film on the internal surface of a long metal tube. The system was designed to coat tubes of different lengths through the use of linear rails positioned below the coupling heads to allow for the adjustment of distance between them and the tube.
2：Sample Selection and Data Sources
Polished stainless steel and silicon wafer samples were mounted on the inside tube surface for subsequent analysis of the coatings. Electrical discharge tests were carried out using a pulsed-DC PECVD system to analyze how pressure and voltage influence the discharge current of an argon plasma.
3：List of Experimental Equipment and Materials
The system consists of a 200 cm long stainless steel (SS) tube with a 10 cm diameter, used as both the deposition chamber and cathode. A pair of SS coupling heads that were 20 cm long and 20 cm in diameter were used to connect both sides of the long tube. The tube temperature was monitored in nine equidistant points using an model E40 Flir Infrared Thermometer.
4：Experimental Procedures and Operational Workflow
The tube was pumped down to a base pressure of approximately 10-4 Torr. A constant gas flow of 5 sccm was maintained throughout the tube. The pulse width and the repetition rate were kept constant at 15 μs and 21 kHz in all experiments, respectively. The total current was measured with a Rogowski coil.
5：Data Analysis Methods
Microstructural properties of DLC films were analyzed through a Raman Spectrometer. The chemical composition of sample surfaces was analyzed by X-Ray Photoelectron Spectroscopy (XPS). Film thickness was measured through field emission gun scanning electron microscopy (FEG-SEM).
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