Foundations of Materials Science and Engineering

Organic electroluminescence (OEL) is the phenomenon of electrically-driven emission of light from organic materials; including both fluorescent and phosphorescent organic solids. The organic light-emitting device (OLED), which exploits OEL emission from organic semiconducting thin films (with thicknesses of less than a few hundred nanometers), sandwiched between electrodes, has attracted keen interest in its application to flat-panel displays, due to its high luminous efficiency, low driving voltage, tunable colors as well as a convenient device-structure design and low fabrication costs when compared with every other known display device.

Electrostatic stresses are a fascinating field where materials science, continuum mechanics and electrical engineering all come together. This is one of the reasons why the study of these so-called Maxwell stresses is so interesting.

Since the first development of lithium-ion batteries in the early 1990’s, there have been tremendous advances in the science and technology of these electrochemical energy sources. At present, lithium batteries dominate the field of advanced power sources and have almost entirely replaced their bulkier and less energetic counterparts such as nickel-cadmium and nickel-metalhydride batteries; especially in portable electronic devices. But lithium batteries are still the object of continuing intense research aimed at making further improvements in performance and safety, at lower cost, so as to make them suitable for higher-power and more demanding applications such as electric vehicles. The research and development of new electrode materials, particularly for cathodes, having an improved electrochemical performance has always been a matter of changing focus. Thus, olivine, lithium iron phosphate, has attracted considerable attention in recent years as a safe, environmentally friendly, extremely stable and very promising cathode material.

The oxidation of metals is, by definition, a reaction between a gas and a solid which usually produces a solid reaction product. At first glance, this would therefore seem to be a very simple process but, in fact, it is considerably more complex. One would like to think that the reaction product, i.e., the scale that forms on the metal, acts as a physical barrier between the reactants, and that the reaction should thus cease once the barrier is established. We know that this is unfortunately not the case, because transport of matter through the scale allows the reaction to continue. We also know that, because of density-differences between the metal and its oxide, the scale may not be sufficiently complete in coverage or may not adhere to the substrate because of cracking, spalling and detachment (wrinkling). In some extreme cases, the scale may even be a liquid which simply drips from the surface, or it may volatilize at operational temperatures. The reaction between a gas and a metal is truly very complicated.

The present monograph is the first systematic study of the non-linear characteristic of gel oxy-hydrate systems involving d- and f- elements. These are the oxyhydrates of rare-earth elements and oxides – hydroxides of d- elements (zirconium, niobium, titanium, etc.) The non-linearity of these gel systems introduces fundamental peculiarities into their structure and, consequently, their properties.

Thin slab casting and direct rolling (TSDR) technologies are nowadays one of the most promising processing routes to maintain steel as a leading material in technological applications. Initially, this process was exclusively for the production of mild steels. As industrial experience and knowledge improved, a rapid expansion of the range of products took place with higher strength grades becoming an important part of the overall production. Actually, it is widely accepted as a route to produce high value grades and it can be considered as a technology which has reached a high degree of maturity. This book aims to provide an approach to the different metallurgical aspects involved in the application of thermomechanical treatments in the TSDR route.

The world of today must face up to two contradictory energy problems: on the one hand, there is the sharply growing consumer demand in countries such as China and India. On the other hand, natural resources are dwindling. Moreover, many of those countries which still possess substantial gas and oil supplies are politically unstable. As a result, renewable natural energy sources have received great attention. Among these, solar-cell technology is one of the most promising candidates. However, there still remains the problem of the manufacturing costs of such cells. Many attempts have been made to reduce the production costs of “conventional” solar cells (manufactured from monocrystalline silicon using diffusion methods) by instead using cheaper grades of silicon, and simpler pn-junction fabrication. That is the ‘hero’ of this book; the heterojunction solar cell.

One of the oldest construction materials is wood which, technically speaking, belongs to the group of polymer matrix composites; one which is conveniently and expertly produced by Nature. Due to its organic cell-type structure, the density of wood remains modest. Thus, as its strength and stiffness can - in certain cases - attain remarkable values, its levels of specific strength and stiffness (absolute strength or stiffness divided by density) can reach magnitudes which are competitive with those of other construction materials. It is demonstrated, for instance, that the specific strength of wood in the axial direction can exceed those of low-carbon steel and concrete. Its specific stiffness can also be comparable to those of aluminum alloys and low-carbon steels, and is better than that of concrete. In constructional design, especially in the dimensioning of supports, the values of specific strength and stiffness are of utmost importance.

The use of light to channel signals around electronic chips could solve several current problems in microelectronic evolution including: power dissipation, interconnect bottlenecks, input/output from/to optical communication channels, poor signal bandwidth, etc. It is unfortunate that silicon is not a good photonic material: it has a poor light-emission efficiency and exhibits a negligible electro-optical effect. Silicon photonics is a field having the objective of improving the physical properties of silicon; thus turning it into a photonic material and permitting the full convergence of electronics and photonics.

The process by which organisms in Nature create minerals is known as biomineralization - a process that involves complex interactions between inorganic ions, crystals and organic molecules; resulting in a controlled nucleation and growth of minerals from aqueous solutions. During the last few decades, biomineralization has been intensively studied, due to its involvement in a wide range of biological events; starting with the formation of bones, teeth, cartilage, shells, coral (so-called physiological mineralization) and encompassing pathological mineralization, i.e. the formation of kidney stones, dental calculi, osteoporosis, arteriosclerosis, osteogenesis imperfecta, etc. During the same period, biomineralization has become a hot topic for world-wide research throughout the world, due to the growing expectations of a good quality and duration of life by the ever-increasing population of the aged. Young people, in particular, also make increasing demands on the quality and the appearance of the existing implants available on the market. The general goals of research and manufacture are now to create and improve implants for various applications in the human body, as well as to prevent diseases leading to the formation of minerals such as hydroxyapatite (implicated, for example, in osteogenesis, kidney stones, dental calculi, arteriosclerosis – all problems which mainly affect women).
The results presented in this book will make a significant contribution to the application of the modified surfaces of widely-studied materials as a model system for hydroxyapatite-coating, to the cultivation of cells on surfaces, as well as to the growth of hydroxyapatite by applying new technologies (such as laser-liquid-solid interaction) that facilitate nucleation and growth. In this way, materials and layers having possible applications as implants, biosensors, etc. can be obtained. The in vitro system described here is universal and can be applied not only to the production of hydroxyapatite coatings for implants, but also to investigating the basic mechanisms of mineral-formation diseases and thus identify new directions for prophylaxis. This will then make a strong contribution to improving the quality and duration of life of the population.