Microstructure And Andtibacterial Properties Of Austenitic Stainless Steel By Copper Ions Implantation

With the development of society and increase of people's living standard, human's consciousness of hygiene safety and cleanliness was increased also, and then the study and application of antibacterial materials were developed broadly and quickly. In the 1990's, some countries leading in industry manufactured stainless steel with antibacterial activity and had been used hi ordinary life. The method of steel making was used in preparing the antibacterial stainless steel in previous study. Metal vapor arc (MEVVA) sources have been used for copper ion implantation to prepare the antibacterial stainless steel in this dissertation.Cu-ion implantation was carried out at energies from 60keV to lOOkeV for doses ranging from 0.2 1017cm-2 to 8 1017cm-2. Antibacterial treatment at 400-700 C for 1-6 hours was applied to make the copper-rich phase precipitate dispersedly and homogeneously. The agar-plate method was adopted for evaluation of the antibacterial property against Escherichia coli, Staphylococci and the method of cycle in salt-dryness-humidity was employed for assessing antibacterial stainless steel's corrosion resistance. Copper layer's microstructure, organization and concentration profile were observed before and after implantation and antibacterial treatment by GXRD, TEM and AES. The changes of Escherichia coli on stainless steel were observed by bio-TEM.The results showed that the un-implanted stainless steel didn't showed antibacterial property. The rate of cell reduction against Escherichia coli was increased with the increasing of copper ions' dose. Stainless steel got the best antibacterial property against Escherichia coli and Staphylococci by copper ions implantation with 100keV, 8 1017cm-2 and antibacterial treatment at 500癈 for 4 hours subsequently. The study of mechanism of killing Escherichia coli by bio-TEM indicated that copper ions affect cell wall and made the cell wall coarse, the permeability of cell wall was changed, and then the substance in the cell degraded, at last, died.Trifle copper-rich phase (Cu9.9Fe0.1) was formed in stainless steel after implantation, so steel possessed antibacterial property against Escherichia coli. Abundant phase of Cu9.9Fe0.1 precipitated in the surface as form of acicular after antibacterial treatment at 500 C for 4 hours, and then steel possessed antibacterial property against Escherichia coli and Staphylococci.The copper's concentration profile accorded with Gauss distribution in stainless steel by high energy and large dose. The peak value of copper's concentration is 30%. Depth of copper ions was 100nm. After the antibacterial treatment at 500 C for 4h, thecopper ions diffused into deeper location of stainless steel, so the concentration profile became gentle and the depth was increased to 300nm. The increase of copper ions' depth will help to assure the durability of antibacterial property.The corrosion resistance deteriorated appreciably after copper ions implantation, but was recovered by antibacterial treatment at 500 C for 4 hours. So stainless steel with antibacterial property has identical corrosion resistance of common stainless steel.This work was supported by The National Science Foundation of China (Grant No.50101009).