T. Bell

Bio: T. Bell is an academic researcher from University of Birmingham. The author has contributed to research in topics: Nitriding & Surface engineering. The author has an hindex of 34, co-authored 67 publications receiving 4487 citations.

Plasma surface engineering of low alloy steel

Abstract: The surface of low alloy steel (En40B) has been engineered in the plasma of a glow discharge via plasma nitriding and ion plating of titanium nitride (TiN) coatings on the nitrided substrates with the purpose of enhancing the surface properties and fatigue strength. The nitriding response of the steel has been accessed by the evaluation of phase composition, layer thickness, hardness profile, residual stresses and nitrogen and carbon distributions. The wear and fatigue characteristics of the plasma-nitrided steel have been investigated and simple models have been developed to describe the influence of such properties as depth and strength of the nitrided case on the fatigue limit and load-bearing capacity of the nitrided steel. In order to further improve the tribological properties and load-bearing capacity of the low alloy steel, a duplex plasma surface-engineering technique has been developed. This is achieved by plasma nitriding the steel first so as to produce a thick, strong subsurface and then depositing a thin, hard and wear-resistant TiN coating on the nitrided substrate by ion plating. Dry-sliding wear tests demonstrated that the duplex-treated steel, i.e. the TiN coating-nitrided steel composite, not only exhibited enhanced wear resistance over the as-nitrided steel (by a factor of 2–8) but also had much higher load-bearing capacity than the TiN coating on unnitrided steel. Optimization of the coating-substrate combination can be achieved by correct control of the plasma-nitriding, surface preparation and ion-plating processes.

State-of-the-art overview: ion beam surface modification of polymers towards improving tribological properties

Abstract: Ion beam surface modification has shown great potential for improving the tribological behaviour as well as surface mechanical properties of polymeric materials. As a result, the past few years have seen many advances in the field of ion beam surface modification of polymeric materials in terms of applying conventional ion beam techniques to various types of polymers, and introducing innovative plasma-enhanced ion implantation techniques. In this paper, the main wear mechanisms of polymeric materials are first overviewed; the state-of-the-art of ion beam surface modification of polymeric materials for improving tribological as well as mechanical properties is assessed through a referenced literature review; the ion–polymer interaction mechanisms involved in ion beam modification of polymers are briefly discussed; finally, key areas for future development are suggested.

Surface modification of titanium alloys for combined improvements in corrosion and wear resistance

Abstract: A simple and effective surface modification technique, namely palladium-treated thermal oxidation (PTO), has been developed in the present research. Comparative investigations on both corrosion and wear resistance have been carried out on surface-engineered titanium-based materials by conventional plasma nitriding (PN), thermal oxidation (TO), and the newly developed palladium-treated thermal oxidation (PTO). Both the TO- and PTO-treated materials have a significantly superior corrosion resistance in boiling HCl solutions compared to the PN-treated and untreated materials. The lifetime for the protective surface layer breakdown of the TO-treated titanium in boiling 20% HCl solution is about 13 times that of the PN-treated titanium, whereas the lifetime of the PTO-treated material has been increased further by a factor of 2.6 over the TO-treated material. The PTO-treated material has shown a better anti-scuffing capacity than the TO-treated material under oil-lubricated conditions. Characterisation of both the TO- and PTO-treated surface layers was performed using glow discharge spectrometry (GDS), X-ray diffraction (XRD) and scanning electron microscopy (SEM).

X-ray diffraction characterisation of low temperature plasma nitrided austenitic stainless steels

Abstract: The nitrided layers produced by low temperature (400–500 °C) plasma nitriding on austenitic stainless steels, AISI 316, 304 and 321, have been characterised by X-ray diffraction, in conjunction with metallographic and chemical composition profile analysis. The thin, hard and corrosion resistant layers exhibited similar X-ray diffraction patterns, but the positions of the major diffraction peaks varied with nitriding temperature and nitrogen concentration profile. The low temperature nitrided layers are predominantly composed of a phase with a face centred cubic (fcc) structure, which is named “S” phase. However, the positions of the diffraction peaks from the “S” phase deviated in a systematic way from those for an ideal fcc lattice. Detailed analysis of the deviation suggested that very high compressive residual stresses and stacking faults were formed in the layers, resulting in a highly distorted and disordered fcc structure. The lattice parameter of the distorted and disordered “S” phase was found to increase with increasing nitrogen concentration.

Recent developments in stainless steels

Abstract: 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.

Finite Time Thermodynamic Optimization or Entropy Generation Minimization of Energy Systems

Abstract: Abstract The historical background, research development, and the state-of-the-art of finite time thermodynamic theory and applications are reviewed from the point of view of both physics and engineering. The emphasis is on the performance optimization of thermodynamic processes and devices with finite-time and/or finite-size constraints, including heat engines, refrigerators, heat pumps, chemical reactions and some other processes, with respect to the following aspects: the study of Newton's law systems, an analysis of the effect of heat resistance and other irreversible loss models on the performance, an analysis of the effect of heat reservoir models on the performance, as well as the application for real thermodynamic processes and devices. It is pointed out that the generalized thermodynamic optimization theory is the development direction of finite thermodynamics in the future.

Nanobio Silver: Its Interactions with Peptides and Bacteria, and Its Uses in Medicine

Abstract: Silver, known in metallic form since antiquity, has very early been recognized by mankind for its antimicrobial properties, a phenomenon observed, for example, in the context of drinking water (a silver coin in a well), food (silver cutlery, water storage recipients), and medicine (silver skull plates, teeth). Silver compounds were also shown to be useful. For example, dilute solutions of silver nitrate served long, and still do in some countries, as antimicrobial ointment to be instilled into Published in \" \" which should be cited to refer to this work.