Titanium alloys are widely used in aerospace, chemical and biomedical fields, but their low hardness and poor anti-wear and anti-friction properties limit their applications. Therefore, the use of surface modification technology to improve the surface properties of titanium alloys has attracted much attention. Generally, the most commonly used method is chemical treatment or chemical oxidation to improve and improve the adhesion between the substrate and the coating layer and the corrosion resistance of the surface. However, the oxide film layer obtained by chemical oxidation is thin, and has poor corrosion resistance and durability. The oxide film on the surface of the titanium alloy makes it difficult to perform electroless plating and electroplating on titanium. In contrast, micro-arc oxidation treatment is currently generally regarded as the most promising titanium alloy surface treatment method.
Micro-arc oxidation is a process of growing a ceramic oxide film in situ on the surface of a material by applying a high voltage (DC, AC or pulse) in an electrolyte solution (usually a weak alkaline solution). This process is physical discharge and electrochemical oxidation, plasma The result of the synergistic effect of body oxidation. This technology is developed on the basis of ordinary anodic oxidation technology. Further increase the voltage so that the voltage exceeds the Faraday zone and reaches the breakdown voltage of the oxide film. Spark discharge will occur at the anode and a ceramic oxide film will be formed on the surface of the material. The plasma oxide film not only has the high performance of the ceramic film, but also maintains the bonding force between the anodized film and the substrate. These characteristics make it a research hotspot in the field of surface engineering technology. Harbin Institute of Technology in China uses micro-arc oxidation technology to add cobalt acetate to the electrolyte, thereby generating a thermal shock ceramic film on the TC4 alloy. The bonding energy between the film layer and the substrate is higher than 10 MPa. The alloy heats in 40 cycles It remained stable under vibration, indicating that the micro arc oxidation treated TC4 alloy has excellent thermal shock resistance.
In the past two years, the micro-arc oxide film layer formed in the electrolyte containing calcium and phosphorus components has high anti-wear, anti-corrosion and biocompatibility, which has attracted the interest of researchers in bone transplantation. South Korea uses micro-arc oxidation technology to generate a nanocrystalline hydrogen-based apatite ceramic layer on the surface of pure titanium. The apatite ceramic in this film layer has a high degree of crystallinity, has a strong biocompatibility, and shows a shape The application potential of surgical and dental repair technology. In China, micro-arc oxidation produced calcium- and phosphorous-titanium bioactive films. The results show that: the film is composed of anatase TiO2 and rutile TiO2, and has a dense inner layer and a porous outer layer; calcium and phosphorus atoms in the film layer The ratio gradually increases from the inside to the outside; after hydrothermal treatment, the film can be converted into a bioactive titanium dioxide layer containing hydrogen-based apatite. The rutile film layer has unique electrical and mechanical properties.
Β-Ti has excellent physical properties and biocompatibility, and is considered by the medical community as the next-generation metal for plastic surgery and dentistry. In order to improve the bone synthesis of β-Ti and human bone tissue, micro-arc oxidation can be used to improve the biological activity of the surface of β-Ti. In Taiwan, China, micro-arc oxidation technology was used to prepare TiO2 ceramic membrane on β-Ti alloy, and the experiment was carried out in vitro and implanted in the tip of the thigh of Japanese mice. The results show that a TiO2 film layer is formed, which is firmly bonded to the substrate, shows better bone formation ability than the pure titanium of the substrate, and is more suitable for application in the field of medical implant correction.
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