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 review analyses the literature from the early 1990s until the beginning of 2003 and covers the use of carbon nanotubes (CNT) and nanofibers as catalysts and catalysts supports. The article is composed of three sections, the first one explains why these materials can be suitable for these applications, the second describes the different preparation methods for supporting metallic catalysts on these supports, and the last one details the catalytic results obtained with nanotubes or nanofibers based catalysts. When possible, the results were compared to those obtained on classical carbonaceous supports and explanations are proposed to clarify the different behaviors observed.

Carbon nanotubes and nanofibers in catalysis

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

Graphene: Synthesis and applications

Steam reforming reactions will play a key role in new applications of synthesis gas and in a future hydrogen economy. The aim of this review is to provide a coherent description of the catalysis of the reforming reactions. The review is not comprehensive. The first section deals with the applications of synthesis gas and hydrogen and the various synthesis gas technologies. The optimum choice of technology depends on the requirements of the gas composition and the scale of operation. Two examples are included for illustration: synthesis gas for gas-to-liquid plants and hydrogen for fuel cells. The steam reforming process is described in the second section with emphasis on the role of the catalyst and problems related to carbon formation. The third section is a summary of the empirical evidence of the catalysis of the reforming reactions. The methods of characterization are discussed, and data representing sintering, activity trends, and promotion are summarized. The fourth section is a description of the mechanism based on a combination of empirical knowledge with recent data from studies of well-defined surfaces, in-situ high-resolution electron microscopy, and calculations based on density functional theory. The central concept is the role of surface defects as the source of reactivity and the nucleation centers for whisker carbon formation.

Hydrogen and Synthesis gas by Steam- and CO2 reforming

The effects of chlorides, hydrogen chloride, and sulfur dioxide in the oxidation of steels below deposits

Chloridation and oxidation of iron, chromium, nickel and their alloys in chloridizing and oxidizing atmospheres at 400–700°C

Equilibrium surface segregation of dissolved nonmetal atoms on iron(100) faces

A survey is given on recent research on metal dusting i.e. a catastrophic carburization or rather graphitization of metals and alloys occuring in carbonaceous atmospheres at carbon activities a C >1. The thermodynamics are explained, the mechanisms for iron, low and high alloy steels, nickel and Ni-base alloys are described and the kinetics derived for iron and low alloy steels. Protection against metal dusting is possible by the presence of sulfur in the atmosphere, since adsorbed sulfur retards carbon transfer and hems graphite nucleation. Also dense oxide layers are protective, the preconditions for the formation of Cr-rich protectivee layers on steels and Ni-base alloys are shortly presenteed.

Hans Jürgen Grabke

Papers

The effects of chlorides, hydrogen chloride, and sulfur dioxide in the oxidation of steels below deposits

Chloridation and oxidation of iron, chromium, nickel and their alloys in chloridizing and oxidizing atmospheres at 400–700°C

Equilibrium surface segregation of dissolved nonmetal atoms on iron(100) faces

Thermodynamics, mechanisms and kinetics of metal dusting

Site competition in grain boundary segregation of phosphorus and nitrogen in iron