The investigation of precipitation behavior of titanium compounds for high titanium steel based on in situ observation.

The effects of cooling rate, Ti content, and casting temperature on titanium compounds for high titanium steel were investigated. In-situ observation of high titanium steel during remelting and solidification was carried out by using a High Temperature Confocal Scanning Laser Microscope (HTCSLM), and the observed results were in good agreement with the thermodynamic and kinetic calculations. The observation and calculation results both show that the inclusions in high titanium steel first precipitate in the form of TiN, followed by TiC precipitates as temperature decreases, eventually forming TiCxN1-x type inclusions at room temperature. The initial precipitation temperature of the inclusions increases with the increase of Ti content in molten steel, whereas casting temperature has little effect on the initial precipitation temperature of inclusions. In addition, the size of TiN inclusions increases with the increase of Ti content in steel but decreases with the increase in cooling rate.

Mitigation of microbial corrosion by Cu addition to X65 pipeline steel by Pseudomonas aeruginosa MCCC 1A00099.

Microbiologically influenced corrosion (MIC) is becoming a knotty problem for transmission pipelines. Developing MIC mitigation strategies for pipelines is increasingly urgent. In this study, MIC resistance against Pseudomonas aeruginosa of the X65 pipeline steels with (X65Cu) and without (X65) Cu addition was comparatively studied by electrochemical measurements and surface observation. Experimental results demonstrated that the corrosion rate of X65Cu steel was lower than that of X65 steel no matter in sterile or bacteria-containing media. Cu addition is helpful to the formation of the rust layer in the sterile medium. Surface observation showed that X65Cu steel exhibited a better MIC resistance against P. aeruginosa than that of X65 steel. Cu ions released from the X65Cu steel could effectively kill the P. aeruginosa attached on the steel surface, thus evidently decreased the pit depth and diameter.

Antibacterial and anti-inflammatory activities of chitosan/copper complex coating on medical catheters: In vitro and in vivo.

Copper ions (Cu) grafted chitosan coating was prepared using the pneumatic spraying method on the silicone rubber surface. Coating's surface properties, morphology, composition, Cu releasing behavior, antibacterial, and anti-inflammatory activities are investigated and discussed. Surface properties, composition, and morphology were investigated by scanning electron microscopy (SEM) and contact angle measurements. The antibacterial activity has been tested with Escherichia coli and Staphylococcus aureus suspensions in vitro. Besides, the morphology of the biofilm was inspected with a field emission SEM. To evaluate the anti-inflammatory activity and biosafety of the coating in vivo, the optimized coating samples and control groups were implanted subcutaneously into the back of mice. The bacterial environment model was established by injection of the bacterial suspension. The morphology and bacterial adhered on the surface of catheters and the surrounding tissues were analyzed after 5 days of implantation. As in vitro results, the number of adhered bacterial on the surface of the silicon rubber surface was decreased, and the anti-inflammatory rate was increased by the intensify of the Cu content in chitosan coating. As for in vivo results, after 5 days of implantation, there was no evident inflammation in the surrounding tissues of all catheters in all without the S. aureus injected group. In the injected chitosan/Cu coated group; the inflammation, the number of the adhered bacteria were observed less than other injected samples without Cu; no inflammation were noticeable. Results indicate that the Cu-modified chitosan coating can confer excellent antibacterial and anti-inflammatory activity as applied on medical catheters.