There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

This article presents an overview of the developments in stainless steels made since the 1990s. Some of the new applications that involve the use of stainless steel are also introduced. A brief introduction to the various classes of stainless steels, their precipitate phases and the status quo of their production around the globe is given first. The advances in a variety of subject areas that have been made recently will then be presented. These recent advances include (1) new findings on the various precipitate phases (the new J phase, new orientation relationships, new phase diagram for the Fe–Cr system, etc.); (2) new suggestions for the prevention/mitigation of the different problems and new methods for their detection/measurement and (3) new techniques for surface/bulk property enhancement (such as laser shot peening, grain boundary engineering and grain refinement). Recent developments in topics like phase prediction, stacking fault energy, superplasticity, metadynamic recrystallisation and the calculation of mechanical properties are introduced, too. In the end of this article, several new applications that involve the use of stainless steels are presented. Some of these are the use of austenitic stainless steels for signature authentication (magnetic recording), the utilisation of the cryogenic magnetic transition of the sigma phase for hot spot detection (the Sigmaplugs), the new Pt-enhanced radiopaque stainless steel (PERSS) coronary stents and stainless steel stents that may be used for magnetic drug targeting. Besides recent developments in conventional stainless steels, those in the high-nitrogen, low-Ni (or Ni-free) varieties are also introduced. These recent developments include new methods for attaining very high nitrogen contents, new guidelines for alloy design, the merits/demerits associated with high nitrogen contents, etc.

Recent developments in stainless steels

In the laser treatment of a workpiece (9), e.g. for surface hardening, melting, alloying, cladding, welding or cutting, the adverse effect of reflectivity of the surface, when a pure, monochromatic laser (6) is used, is remedied by the simultaneous application of a relatively shorter wavelength beam (1). The two beams (1)(5) may be combined by a beam coupler (4) or may reach the workpiece (9) by separate optical paths (not shown). The shorter wavelength beam (1) improves the coupling efficiency of the higher- powered laser beam (5).

Laser Material Processing

The photocatalytic properties of titanium dioxide are well known and have many applications including the removal of organic contaminants and production of self-cleaning glass. There is an increasing interest in the application of the photocatalytic properties of TiO2 for disinfection of surfaces, air and water. Reviews of the applications of photocatalysis in disinfection (Gamage and Zhang 2010; Chong et al., Wat Res 44(10):2997–3027, 2010) and of modelling of TiO2 action have recently been published (Dalrymple et al. , Appl Catal B 98(1–2):27–38, 2010). In this review, we give an overview of the effects of photoactivated TiO2 on microorganisms. The activity has been shown to be capable of killing a wide range of Gram-negative and Gram-positive bacteria, filamentous and unicellular fungi, algae, protozoa, mammalian viruses and bacteriophage. Resting stages, particularly bacterial endospores, fungal spores and protozoan cysts, are generally more resistant than the vegetative forms, possibly due to the increased cell wall thickness. The killing mechanism involves degradation of the cell wall and cytoplasmic membrane due to the production of reactive oxygen species such as hydroxyl radicals and hydrogen peroxide. This initially leads to leakage of cellular contents then cell lysis and may be followed by complete mineralisation of the organism. Killing is most efficient when there is close contact between the organisms and the TiO2 catalyst. The killing activity is enhanced by the presence of other antimicrobial agents such as Cu and Ag.

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Photocatalytic disinfection using titanium dioxide: spectrum and mechanism of antimicrobial activity

In the area of materials science, corrosion of biomaterials is of paramount importance as biomaterials are required for the survival of the human beings suffering from acute heart diseases, arthritis, osteoporosis and other joint complications. The present article discusses various issues associated with biological corrosion of different kinds of implants used as cardio stents, orthopedic and dental implants. As the materials used for these implants are manifold starting from metallic materials such as stainless steel (SS), cobalt chromium, titanium and its alloys, bioceramics, composites and polymers are in constant contact with the aggressive body fluid, they often fail and finally fracture due to corrosion. The corrosion behavior of various implants and the role of the surface oxide film and the corrosion products on the failure of implants are discussed. Surface modification of implants, which is considered to be the best solution to combat corrosion and to enhance the life span of the implants and longevity of the human beings is dealt in detail and the recent advances in the coating techniques which make use of the superior properties of nanomaterials that lead to better mechanical properties and improved biocompatibility are also presented.

Biomedical Implants: Corrosion and its Prevention - A Review~!2009-12-22~!2010-01-20~!2010-05-25~!

Semiconducting and passive film properties of nitrogen-containing type 316LN stainless steels

Introduction to austenitic stainless steels Uniform corrosion of austenitic stainless steels Pitting corrosion Crevice corrosion Sensitization and testing for intergranular corrosion Metallurgical influences on stress corrosion cracking Stress corrosion cracking of austenitic stainless steel weldments Applications of fracture mechanics in stress corrosion cracking and introduction to life prediction approaches Microbiologically influenced corrosion Corrosion of austenitic stainless steel in liquid sodium High temperature corrosion of austenitic stainless steel Corrosion detection and monitoring in austenitic stainless steels using non-destructive testing and evaluation techniques Corrosion related failures of austenitic stainless steel components Surface modification for corrosion protection of austenitic stainless steels General guidelines for corrosion control.

H. S. Khatak

Papers

Semiconducting and passive film properties of nitrogen-containing type 316LN stainless steels

Corrosion of austenitic stainless steels : mechanism, mitigation and monitoring

On the pitting corrosion resistance of nitrogen alloyed cold worked austenitic stainless steels

Corrosion of Austenitic Stainless Steels

Use of eddy current testing method in detection and evaluation of sensitisation and intergranular corrosion in austenitic stainless steels