Fanya Jin

Effects of external magnetic field on propagation of electromagnetic wave in uniform magnetized plasma slabs

A simple method is proposed to describe the propagation of electromagnetic waves in magnetized uniform plasma slabs. Using this method, the reflection, absorption and transmission coefficients of such plasmas for right-hand circularly waves are studied and the effects of the continuously changing external magnetic field on the power of the electromagnetic waves propagated in magnetized plasma slabs with fixed parameters are presented. Our method enables more detailed numerical analyses which are useful in practical applications pertaining to the control of the reflection or absorption coefficients of electromagnetic wave through a uniform magnetized plasma slab by adjusting the external magnetic field.

Corrosion resistance and antithrombogenic behavior of La and Nd ion implanted stainless steels

Lanthanide ions such as lanthanum (La) and neodymium (Nd) were implanted into 316 stainless steel samples using metal vapor vacuum arc to improve the surface corrosion resistance and antithrombogenic properties. X-ray photoelectron spectroscopy shows that lanthanum and neodymium exist in the +3 oxidation state in the surface layer. The corrosion properties of the implanted and untreated control samples were investigated utilizing electrochemical tests and our results show that La and Nd implantations enhance the surface corrosion resistance. In vitro activated partial thromboplastin time (APTT) tests were used to evaluate the antithrombogenic properties. The APTT time of the implanted samples was observed to be prolonged compared to that of the unimplanted stainless steel control. La and Nd ion implantations can be used to improve the surface corrosion resistance and biomedical properties of 316 stainless steels.

Dependence of ion sheath collapse on secondary electron emission in plasma immersion ion implantation

The collapse of the ion sheath in front of a dielectric substrate during argon plasma immersion ion implantation is investigated using a Langmuir probe. The probe signals during the buildup and collapse of the ion sheath are recorded from a lime glass substrate with a magnesium metal plate placed on top. The collapsing speed of the ion sheath is shown to strongly depend on the secondary electron emission coefficient of the substrate. The authors’ results show that it is possible to derive secondary electron emission coefficients from insulating materials based on the probe signals.

Bioactivity and corrosion behavior of magnesium alloys treated by plasma electrolytic oxidation

Summary form only given. As a lightweight and nontoxic metal with mechanical properties similar to those of natural bones, magnesium based materials have attracted much interest in biomedical engineering. As the materials are both biocompatible and biodegradable, they can be used in many orthopedic and load-bearing applications. However, the poor corrosion resistance of magnesium-based biomedical implants in a physiological environment has hampered their use as substitutes for human hard tissues. Recently, plasma electrolytic oxidation (PEO) that is derived from anodic oxidation technology has been applied to treat valve-metals such as Al, Mg, Ti and their alloys. By utilizing micro-arc plasma discharges sustained at a high voltage in aqueous solutions, various oxide films can be formed on these metals to improve their surface properties such as wear and corrosion resistance as well as bioactivity. In this work, PEO treatments are conducted on magnesium alloys in different electrolytes and different voltage modes. The corrosion resistance is determined in simulated body fluids (SBF) based on the potentiodynamic polarization curves, and the surface bioactivity is investigated by monitoring the apatite inducing capability. The structure and chemistry of the plasma-formed surface oxide which exhibits a porous structure are evaluated. Our results show that the corrosion resistance and bioactivity of the PEO Mg alloys are much improved