Amorphous specific strength

Melting temperature, °C Crystalline Amorphous Specific gravity Water absorption (24 h), % Dielectric strength, kV mm ... 

Furthermore, Kato et al. (1995) have shown that bulk Mg-Ca-Al alloys have a corrosion resistance superior to that of the AZ91-T6 alloy. It is therefore concluded that bulk Mg-Y-Mm, Mg-Cu-Y and Mg-Ca-Al alloys obtained by extrusion of atomized amorphous powders exhibit high tensile strength at room temperature and elevated temperatures and Mg-Ca-Al alloys a high corrosion resistance as well. These excellent properties allow us to expect that the Mg-based alloys could be used in various application fields where high specific strength and corrosion resistance are required. 

One simple means of causing slow precipitation is to add denaturant to an aqueous solution of protein until the denaturant concentration is just below that required to precipitate the protein. Then water is allowed to evaporate slowly, which gently raises the concentration of both protein and denaturant until precipitation occurs. Whether the protein forms crystals or instead forms a useless amorphous solid depends on many properties of the solution, including protein concentration, temperature, pH, and ionic strength. Finding the exact conditions to produce good crystals of a specific protein often requires many careful trials and is perhaps more art than science. I will examine crystallization methods in Chapter 3. 

Electroacoustic studies of silica at high ionic strengths produced controversial results similar to those discussed in Section 4.3.2. Amorphous materials [1813,1870] showed a shift in the IEP to high pH at 1-1 electrolyte concentrations of 0.1 M or higher. The shift was more substantial in the presence of Cs than in the presence of other monovalent cations. This result is in line with the cation specificity series reported in Section 4.1.5. However, the IEP of quartz [1813] was not shifted in the presence of 1-1 electrolytes. Montmorillonite and kaolinite [2271] showed shifts in the IEP and similar cation affinity series as amorphous silica. Contradictory results are reported for goethite [76,1318]. 

The interaction between titanium sulfate and zirconia influenced the physicochemical properties of prepared catalysts with calcination temperature. The presence of titanium sulfate delays the phase transitions of Zr02 from amorphous to tetragonal and from tetragonal to monoclinic. The specific surface area and acidity of catalysts increase in proportion to the titanium sulfate content up to 5 wt% of Ti(S04)2. The correlation between catalytic activity and acidity holds for both reactions, cumene dealkylation and 2-propanol dehydration, although the acid strength required to catalyze acid reaction is different depending on the type of reactions. 

Unique nanocrystalline microstructures can be produced by controlled crystallization of the fully amorphous product, including nanocrystalline precipitates homogeneously distributed in an amorphous alloy matrix. In some systems, both the strength and ductility increase in this partially crystalline state [24], Other alloys produce nanocrystalline intermetallic or quasicrystalline precipitates, providing a credible path for increasing the specific stiffness. Thus, a significant effort is required to study the kinetics of crystallization, the devitrification pathways and the microstructures and properties that may be produced upon devitrification. The potential for exploration of novel compositions and microstructures in this class of materials is clearly promising. 

---