Single-material systems

Despite variatioas ia hardness test procedures and the variations ia physical properties of the materials tested, hardness conversions from one test to another are possible (see ASTM E140 and Table 2). This approximate relationship is only consistent within a single-material system, eg, iron, steel, or aluminum. 

Other investigators have evaluated the potential for these indices. In their studies, Williams and McGinnity have concluded that evaluation of single-material systems should precede binary or tertiary powder systems [29]. A full discussion of compaction mechanisms is given later in this chapter. 

One of the most intriguing and beautiful aspects of material specificity is revealed by the phase diagrams used to describe the different phases observed in solids. Figs. 1.4 and 6.2 revealed the complexity present even in elemental solids with the case of sulfur exhibiting the wide variety of different structures seen as the temperature and pressure are changed. The alloy case can be even more complex as evidenced by figs. 1.4 and 6.4. From the standpoint of material specificity we only wish to note that even with a single material system the atomic-level structures are as diverse as are the elements themselves. 

Bismuth telluride with the stoichiometric composition ratio (Bi TCj) is electronically neutral. However, the common carrier of the bismuth telluride alloy can be modified by adjusting the percentage of tellurium or bismuth incorporated. If the alloy is tellu-ride-rich, it can be n-type. In order to be p-type, the composition of the bismuth telluride alloy should be bismuth-rich instead of telluride-rich [59]. This is advantageous since the material deposition development can focus on a single material system which will yield both the n- and p-branches of the thermoelectric probes. 

Products consisting of only one material in a single system (non-composite) are easy and pure to re-use. With them, it is not generally necessary to separate the product structure prior to processing. This is why single-material systems are preferable when it comes to the design of products easy to recycle. Such systems, however, might meet their limits in cases where... 

One example of a complex scaffold stmcture that is manufactured from a single material but different morphologies and functionalities are flock scaffolds for cartilage repair made from chitosan. The major advantage of a single material system is the uniformity of the degradation behavior and the response of cells and immune system to the implant. 

D. Aibibu, Biodegradable and Mechanically Stable Elastic Textile Scaffold ftom a Single Material System (Man-made Fibers Congress). Dombim (11.09.2014). 

An exceptional advantage of self-reinforced thermoplastic composites is that they can be thermally recycled, but also reprocessed due to their polymer purity. This can be done by either returning the composite to a melted state or by simply re-granulating it. Thus, this process does without the complicated and expensive separation of the components, because an actual single-material system is on hand. Such a simple and useful recycling concept (in regard to material reuse) for the quantities currently in circulation has yet to be developed for the established foreign fiber reinforced thermoplastics. 

Photochromizm and Imaging, Fig. 1 Mechanisms of some typical photochromic materials, (a) Single material system, (b) Composite material system, (c) Composite material systems with reversible photoinduced processes... 

---