This investigation studies the effects of Cu content and ageing treatment on the microstructural, mechanical, corrosion and antibacterial properties of SUS 304 austenitic stainless steel. Cu was added respectively to SUS 304 stainless steels in proportions of 1.5, 2.5, 3.5, 4.5 and 5.5 wt.%. A vacuum arc remelting furnace was used to remelt SUS 304 stainless steel with various added Cu contents. These ingot alloys underwent hot rolling and various heat treatments, and were then cut into test specimens. A series of microstructural investigation, tensile tests, corrosion tests and antibacterial tests were conducted to study the properties of Cu-containing SUS 304 austenitic stainless steel. Microstructural observations reveal that the amount of retained δ-ferrite in the as-cast SUS 304 steel decreases as the Cu content increases. After hot rolling, the retained δ-ferrite disappears and α′-martensite forms in the austenitic matrix. The results of the tensile tests reveal that the ultimate tensile strength (UTS) declines as the Cu content increases below 2.5 wt.%. However, the ultimate tensile strength increases with the Cu content above 2.5 wt.%. X-ray diffraction analysis reveals that adding Cu suppresses the formation of strain-induced martensite (α′-martensite). The corrosion test indicates that the pitting potential declines as the Cu content in SUS 304 steels increases. The results of the antibacterial test reveal that adding a proper amount of Cu (such as 2 wt.%) gives SUS 304 stainless steel an excellent antibacterial property.

Implant related infections remain a concern in modern surgery. Surface modification is an effective way to reduce the occurrence of these complications. Of various techniques, ion implantation shows promise. In the present work, silver and copper were ion implanted separately, into three typical medical metals, namely 317L stainless steel, titanium, and Ti–Al–Nb by a MEVVA ion source machine at various ion doses. The objective of this study was to determine the influence of silver and copper ion implantation on antibacterial performance and wear and corrosion resistance of the three materials. Antibacterial activity of silver- and copper-implanted samples against Staphylococcus aureus were assessed by the plate-counting method. The results show that silver and copper implantation improves the antibacterial rate and wear performance of all the three metals studied. It is also found that silver ion implantation does not change the corrosion resistance while the corrosion resistance of copper-implanted samples shows a significant decline. In conclusion, silver ion implantation is favorable to copper ion implantation for increasing the antibacterial nature of these three metals.

In order to study the effect of copper ion implantation on the antibacterial property of AISI 420 stainless steel (SS), specimens were implanted by copper ions in a dose ranging from 2 × 10¹⁶ to 5.0 × 10¹⁷ions cm^− 2, using metal vapor vacuum arc source at an extracting voltage of 50 kV. The microstructure, phase compositions and Cu ions concentration profile in the implanted layer were revealed by glancing angle X-ray diffraction, transmission electronic microscopy (TEM) and Auger electronic spectroscopy, respectively. Film attachment method was adopted for evaluation of antibacterial property of specimens against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). With TEM, changes of bacterial appearance on the surface of un-implanted SS and annealed Cu-implanted SS were observed separately. Results showed that novel phases such as Fe₄Cu₃ and Cu_9.9Fe_0.1 were formed in the surface layer of the annealed Cu-implanted SS and that the antibacterial property resulted from the Cu-contained and Cu-rich phase which had a damaging effect on pericellular membrane and cell wall. Furthermore, the pericellular membrane was thickened and then the karyon was degraded, and finally, bacteria died. Annealed Cu-implanted SS not only obtains excellent antibacterial property, but also keeps good corrosion resistance which is equivalent to that of common AISI 420 SS.

There is an increasing interest in reducing bacterial harmfulness in recent years. Copper-containing titanium nitride films were fabricated on commercial stainless steel using hybrid processes combining dual magnetron sputtering. The objective of this work is to obtain antibacterial surface properties through copper doping for consumer products such as household hardware. In the fabrication process, a titanium target was sputtered using a radio-frequency power supply for easy monitoring of the film color. Copper was also sputtered using a DC power supply. In order to optimize the surface properties, multi-layer films were deposited and the relative amount of copper in the films was modulated by the ratio of the deposition time of different targets. The deposited films exhibit superior corrosion resistance and the corrosion current of the treated sample is reduced to about one-sixth of that of the untreated one. The pin-on-disk results show that the treated samples possess low friction coefficients and the wear tracks are observed to be narrow and smooth. The copper-containing films are very effective in killing the bacteria Escherichia coli. A longer TiN deposition time may lead to a more superior antibacterial capability in addition to enhanced corrosion resistance and wear resistance.

Based on plasma nitriding technique, Double Glow Plasma Surface Alloying Technology (DG Technique) was developed in 1980. This technique breaks the restriction of traditional plasma nitriding and successfully applies solid alloying elements, such as Ni, Cr, W, Mo, Ti, Al, Nb et al., to realize plasma surface alloying. Numerous experiment results concerning the DG technique have demonstrated that various alloys and alloy steels, such as high speed steel, nickel base alloy and wear resistant alloys et al., have been produced upon the surfaces of carbon steels, titanium alloys, Ti–Al intermetallic compounds and copper.

This paper is written in hope that the differences between plasma nitriding and DG technique will become more apparent. Some new development and experiment results of the double glow plasma surface alloying are also shown in this paper. For example, Ti–Al–Nb–C alloy has been produced on the surface of TiAl and Ti–Cu and Ti–Cr burn-resistant alloys have been formed on the surfaces of titanium and Ti6Al4V alloy by using this process; When solid graphite is used as carbon supplier, hydrogen-free carburizing has been carried out in order to avoid hydrogen embrittlement of titanium materials; Co–W–Mo–Fe age hardened high speed steel has been produced on the surfaces of carbon steels.

Coppermodified hexagonal mesoporous silica (Cu-HMS) was in situ prepared with sol-gel method. The structure and the performance of Cu-HMS were characterized by XRD, TG-DTA, ESR, UV-Vis, FT-IR, ESEM, EDS and N₂ adsorptiondesorption isotherms. Based on bacteriostasis experiments of E. coil, S. aureus, B. subtilis and G. bacillus, the antibacterial ability of the sample was also investigated. The results show that the particles of Cu-HMS look like regular thallus, the specific surface area is 533m²/g, the average pore size is 3.6nm, and the copper ions are presented in framework of the sample, especially. The sample has favorable mesoporous structure, thermal stability and ultraviolet-visible-light absorption ability. Furthermore, The bacteriostasis experimental results show that Cu-HMS has favourable and steady antibacterial ability. When the dosage of Cu-HMS is 20mg/L, the bacteriostasis ability may be visibly detected in 12h, while the dosage is up to 200mg/L, E. coil, S. aureus and B. subtilis may be killed after 24h.

采用溶胶凝胶法，原位合成了铜改性的六方介孔硅 (Cu-HMS)无机抗菌材料. XRD、TG-DTA、ESR、UV-Vis、FT-IR、ESEM、EDS及N₂吸附脱附等对材料结构与性能进行了表征；以大肠杆菌、金黄色葡萄球菌、枯草杆菌及芽孢杆菌作供试菌种，考察了材料的抗菌性能. 结果表明，材料粒子呈规则的叶片状，比表面积为553m²/g，平均孔径约3.6nm，铜以离子形式存在于材料的骨架结构中，材料具有良好的介孔结构和热稳定性，有优良的紫外-可见光吸收性能；在抗菌实验中，材料的抗菌效能较好，抗菌性能稳定持久. 材料用量20mg/L，12h即表现出明显的抑菌作用；用量为200mg/L时，24h后可彻底杀灭大肠杆菌、金黄色葡萄球菌及枯草杆菌.

A study was made on the antibacterial mechanism of copper-bearing austenitic antibacterial stainless steel by a series of methods such as atomic force microscopy (AFM) observation, force–distance curves and inductively coupled plasma mass spectrometer test. It was observed by AFM that the structure of the outer cell membrane responsible for the cell permeability was substantially changed for the bacteria after contacting with the antibacterial stainless steel, showing that cell walls were seriously damaged and a lot of contents in the cells leaked. It was also found that the adhesion force of bacteria to antibacterial stainless steel was considerably greater than that to the contrast steel, indicating that the electrostatic forces by Cu²⁺ being an important factor for killing bacteria.

Abstract

The antimicrobial properties of silver and copper nanoparticles were investigated using Escherichia coli (four strains), Bacillus subtilis and Staphylococcus aureus (three strains). The average sizes of the silver and copper nanoparticles were 3 nm and 9 nm, respectively, as determined through transmission electron microscopy. Energy-dispersive X-ray spectra of silver and copper nanoparticles revealed that while silver was in its pure form, an oxide layer existed on the copper nanoparticles. The bactericidal effect of silver and copper nanoparticles were compared based on diameter of inhibition zone in disk diffusion tests and minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of nanoparticles dispersed in batch cultures. Bacterial sensitivity to nanoparticles was found to vary depending on the microbial species. Disk diffusion studies with E. coli and S. aureus revealed greater effectiveness of the silver nanoparticles compared to the copper nanoparticles. B. subtilis depicted the highest sensitivity to nanoparticles compared to the other strains and was more adversely affected by the copper nanoparticles. Good correlation was observed between MIC and MBC (r² = 0.98) measured in liquid cultures. For copper nanoparticles a good negative correlation was observed between the inhibition zone observed in disk diffusion test and MIC/MBC determined based on liquid cultures with the various strains (r² = −0.75). Although strain-specific variation in MIC/MBC was negligible for S. aureus, some strain-specific variation was observed for E. coli.