| 其他摘要 | Health problems should be considered from the aspects of cloth, food, housing and travel with increasing needs in life environments, sanitations and health cares. People will pay more attention to all kinds of healthy environmental problems, such as environment of living space, cleaning of goods, personal safety, etc. Therefore, application of antibacterial functional materials and products will become one of leading actors in the 21 century ecological environment. Antibacterial stainless steels are classes of new functional materials which have both mechanical and antibacterial functions, and its application fields will be broad. Research and development of new antibacterial stainless steel is of both economical and social importance. In order to provide more information for the development of new antibacterial stainless steels, in this thesis, antibacterial characteristics and mechanism of both austenitic and ferritic Cu-bearing antibacterial stainless steels, which were developed by Institute of Metal Research, Chinese Academy of Sciences, were deeply investigated, and the main conclusions have been made as follows:
(1) Study on antibacterial characteristics of antibacterial stainless steel
The film attachment method was adopted to study the broad antibacterial spectrum of the antibacterial stainless steels and effects of action time, bacterial concentration, action temperature and milling times on the antibacterial properties, indicating that the steels possess excellent antibacterial characteristics.
(2) Study on antibacterial mechanism of antibacterial stainless steels in aspect of microbe
The result of radicel-SH oxidation indicated that the antibacterial stainless steel possibly has the ability of oxidation of the reducible enzyme, and the O2- also plays an important role during the sterilization. Experimental results of ICP and EDTA complexing proved the antibacterial effect of copper ions dissolved from surface of antibacterial stainless steels. It was observed on bio-TEM that the morphology of E. coli was changed a lot after contacting with antibacterial stainless steels, cell walls being broken into pieces and lots of contents in the cells being leaked. The permeation through cells grew and the concentration of K+ in the solution greatly increased after contact of E. coli with antibacterial stainless steels for a long time.
(3) Study on antibacterial mechanism of antibacterial stainless steels pointing aspect of material
Through measurement of potentiodynamic polarization on antibacterial stainless steel and the contrast stainless steel, effect of ε-Cu precipitation on the electrochemical behavior of antibacterial stainless steels in a 0.1mol/L NaCl solution was analyzed. The results showed that after interaction between the bacteria and antibacterial stainless steels, pitting potentials of the steels decreased because of the dissolution of copper ions from the antibacterial phase. The antibacterial rate reached the maximum with the contact time between antibacterial stainless steels and bacteria, which well corresponded to the dissolution amount of copper ions from the surface of antibacterial stainless steels. Morphology changes of E.coli after contact with antibacterial stainless steels for different time were observed on AFM. The results showed that after contact with antibacterial stainless steel, the cell membrane or cell wall of bacteria was destroyed, permeability of the cell was increased and the inner contents were largely leaked, thus leading to death of bacteria.
(4) Study on microstructure of antibacterial phase in austenitic antibacterial stainless steel
Microstructural observation on austenitic antibacterial stainless steel under optical microscopy showed that the radical of Cu-rich precipitation was paralleled to (100) face of each eched square pit, growing along with the mechanical processing direction. Microstructrual observation on the antibacterial phase in austenitic antibacterial stainless steel was investigated on High Resolution TEM. The results indicated that large amounts of ε-Cu phase existed in the matrix of austenitic antibacterial stainless steel, with average diameter of 30nm, average length of 70nm and FCC structure, and orientation relationship of ε-Cu phases well matched with the matrix. Large amounts of ε-Cu precipitates dissolving from the matrix during ageing gives excellent antibacterial properties to the austenitic antibacterial stainless steel. ε-Cu phases showed much ordered atoms arrangement, compared with the distorted atoms arrangement of austenitic matrix, indicating that the austenitic matrix around ε-Cu precipitates were in the metastable state and the internal stress might be produced by ε-Cu phase. |
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