Magnesium alloys are potential materials for use in biodegradable hard-tissue implants, but the fast degradation rate in a biological environment limits their applications. In order to improve the corrosion resistance, a dense, adhesive, and biocompatible Al 2 O 3 /Al bilayered coating is fabricated on AZ91 magnesium alloy by means of filtered cathodic arc deposition. The electrochemical behavior is systematically studied in simulated body fluids using a potentiodynamic polarization test, open-circuit potential evolution, as well as electrochemical impedance spectroscopy. Our results indicate that the corrosion resistance of the coated alloy is significantly enhanced. The deterioration mechanism and corrosion process of the coating during immersion are discussed.
In situ temperature monitoring is extremely important in plasma immersion ion implantation ͑PIII͒ of semiconductors. For instance, the silicon wafer must be heated to 600°C or higher in separation by plasma implantation of oxygen, and in the PIII/ion-cut process, the wafer temperature must remain below 300°C throughout the experiment. In this article, we present a thermocouple-based direct temperature measurement system for planar samples such as silicon wafers. In order to ensure reliable high-voltage operation and overall electrical isolation, the thermocouple assembly and wires are integrated into the sample chuck and feedthrough. Hydrogen plasma immersion ion implantation is performed in silicon to demonstrate the effectiveness and reliability of the device. Our experimental results indicate that instrumental parameters such as implantation voltage, pulse duration, and pulsing frequency affect the sample temperature to a different extent. The measured temperature rise is higher than that predicted by a theoretical model based on the Child-Langmuir law. The discrepancy is attributed to the finite-sample size and the nonplanar, conformal plasma sheath.
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