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Towards multi-functional stainless steel surface: plasma surface alloying with N, Ag and Cu

Dong, Yangchun (2011)
Ph.D. thesis, University of Birmingham.

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Hospital-acquired infections, a large proportion of which are derived from contact transmission, represent a massive global challenge. It has been proved that surface modification of biomaterials with Ag or Cu has evolved as a potentially effective method for preventing bacterial proliferation on the devices surfaces. However, thin antimicrobial coatings on materials such as austenitic stainless steels can be easily worn and removed in relative motion with other surfaces. The purpose of this study is to develop multi-functional stainless steel surfaces which combine greatly improved wear resistance, at least maintain corrosion resistance and provide long-lasting, high efficacy, antimicrobial effects. In this thesis a series of surface engineering technologies, including active screen co-alloying, active screen plasma duplex alloying and double glow plus active screen duplex plasma alloying, were developed for surface alloying stainless steel with Ag or Cu and N; the phase constitution, microstructure, composition, and surface roughness of the alloyed surfaces were fully characterized, and the surface hardness, wear resistance, bonding strength, antimicrobial efficiency and corrosion behaviour of the treated surfaces were evaluated. In addition, further inspection of the wear mechanisms and corrosion mechanisms were conducted on post-exposure surfaces. It was found that the adhesive wear mechanism of austenite can be reduced by this alloying combination and the wear resistance was improved by up to 1000 times, and the Ag/Cu alloyed surface was bactericidal and growth-inhibitive for many pathogens including E. coli NCTC 10418 and S. epidermidis NCTC 11047 effectively up to 99%/6h. The mechanism of bactericidal efficiency of Ag/Cu is found dependent on the structure of the bacterial membrane and a higher efficiency of antibacterial agents is found associated with the higher elemental concentration of copper and silver. With regard to corrosion, it is affected largely by the configuration of surface structure and several corrosion mechanisms were evolved. One principal conclusion was that it is feasible to generate long lasting antimicrobial stainless steel surface to fulfil growing demands from industry for practically robust multifunctional medical device surfaces.

Type of Work:Ph.D. thesis.
Supervisor(s):Dong, Hanshan
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Metallurgy and Materials
Additional Information:

Publications [1] Y Dong, X Li, L Tian, T Bell, R Sammons, H Dong: “Towards long-lasting antibacterial stainless steel surfaces by combining double glow plasma silvering with active screen plasma nitriding”, Acta Biomaterialia 2010 7(1):447-457. [2] Y Dong, X Li, R Sammons, H Dong: “The generation of wear-resistant antimicrobial stainless steel surfaces by active screen plasma alloying with N and nanocrystalline Ag”, Journal of Biomedical Materials Research Part B: Applied Biomaterials 2010 93(1):185-193. [3] Y Dong, X Li, T Bell, R Sammons and H Dong: “Surface microstructure and antibacterial property of an active-screen plasma alloyed austenitic stainless steel surface with Cu and N”, Biomedical Materials 2010 5(5):054105.

Keywords:Wear resistance; Silver; Antimicrobial; Wear resistance; Attachment and adhesion;Stainless steel; Plasma nitriding; active screen plasma; E. coli; S. epidermidis; MRSA; cells;Long-lasting; Durability; Cytocompatibility; Killing rate; Contact angle; Surface free energy; EDS/WDS; TEM; Corrosion resistance; Hardness; Coating; Hydrophobicity; S-phase
Subjects:TS Manufactures
RZ Other systems of medicine
QD Chemistry
TN Mining engineering. Metallurgy
QR Microbiology
QC Physics
Institution:University of Birmingham
ID Code:1455
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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