Amorphous structural stability

One of the major drawbacks to many promising copolymers is their unsatisfactory electrochemical stability. Carbonyl groups which feature in many of the back-bone/chain linking groups are likely to cause stability concerns. Likewise, urethane, alcohol, and siloxane functions are sensitive to lithium metal. With this in mind, a recent trend has been to find synthetic routes to amorphous structures with... 

Hydrated metal sulphates have long been used to study water removal processes, and characteristic kinetic behaviour is conveniently illustrated by reference to these substances. Frost and co-workers [602,603] have investigated the structures, stabilities and adsorption properties of various intermediate amorphous phases, the immediate reaction products which can later undergo reorganization to yield crystalline phase. 

In addition to Au and noble metals, Ni-Zn nanoclusters with an amorphous structure were successfully deposited on Ti02 nanoclusters. The state of Ni was metallic. The catalytic activity of Ni-Zn/Ti02 in olefin hydrogenation was ca. 10 times higher than unsupported Ni nanoclusters. Selective deposition onto Ti02 and the addition of Zn seemed to play an important role to stabilize Ni nanoclusters and to decrease the size of Ni nanoclusters, respectively. Also, clearly Zn promoted the hydrogenation activity of Ni and inhibit the growth of the size, but did not substantially affect Ni nature itself... 

This approach, however, requires the absence of ill-defined carbon deposits originating from defect-induced soot formation on the surface of nanocarbons during their synthesis. Pyrolytic structures often counteract the control over activity and selectivity in catalytic applications of well-defined nanocarbons by offering an abundance of highly reactive sites, however, in maximum structural diversity. Although some nanocarbons are equipped with a superior oxidation stability over disordered carbons [25], such amorphous structures can further induce the combustion of the well-ordered sp2 domains by creating local hotspots. Thermal or mild oxidative treatment,... 

The four protein conformations that provide mechanical stability to cells, tissues, and organs include the random coil or amorphous structure that characterizes a part of the structure of elastin, the a helix, which is represented by the keratin molecule, the collagen triple helix, and the p structure of silk. In humans the P structure is found only in short sequences connecting parts of other structures such as the a helix, but serves as an example of the relationship between protein structure and properties. The ultimate tensile strength and modulus of each structure differs as discussed below. 

The total BOs for each structure explain the structural stabilities in each system as well. The original structure models are more stable than replaced models. In the previous studies [15], the glass-formation abilities of the amorphous alloys were estimated by the calculation of the small representative clusters. However the glass-formation abilities depend not only on the stabilities of the amorphous alloys but also those of crystals. Moreover, the small clusters cannot cover the varieties of the bonds (the combinations and the distances of the pair). 

In this chapter we present a survey of our current understanding of interrelations between the electronic and ionic structure in late-transition-polyvalent-element metallic glasses. Evidence of a strong influence of conduction electrons on the ionic structure, and vice versa, of the ionic structure on the conduction electrons, is presented. We discuss as well the consequences to phase stability, the electronic density of states, dynamic properties, electronic transport, and magnetism. A scaling behaviour of many properties versus Z, the mean electron number per atom, is the most characteristic feature of these alloys. Crystalline alloys which are also strongly dominated by the conduction electrons are often called electron phases or Hume-Rothery phases. The amorphous alloys under consideration are consequently described as an Electron Phase or Hume-Rothery Phase with Amorphous Structure. Similar theoretical concepts as applied to crystalline Hume-Rothery alloys are used for the present amorphous samples. 

In accordance to the common rule of an increased glass ability in multicomponent alloys [4], the amorphous structure in Al-Ni-Ce-Sc ribbons appeared to be more stable than in Al-Ce-Sc ribbons an XRDP with a small a-Al peak of the type of Fig. 4c was registered only for the ribbon Al85Nii0Sc5 of 50 pm in thickness, and for the same ribbon of 35 pm in thickness no such peak was observed. The influence of Sc on the thermal stability in this group of alloys had a non-monotonous character introducing... 

The influence that moisture has on stability depends on how strongly it is bound, i.e., it depends on whether the moisture is in a free or bound state. Generally, degradation arises as a function of free water, which may be due to its ability to change the pH of the surfaces of candidate drug and excipient (Monkhouse 1984). On the other hand, bound water is not available if it is (1) a crystal hydrate, (2) hydrogen bonded or (3) sorbed or trapped in an amorphous structure. 

---