Janusz S. Szmyd

Electrochemical Hydrogenation of Ti45Zr38Ni17 Quasi Crystal and Amorphous Powders Produced by Mechanical Alloying

The electrochemical properties of Ti 45 Zr 38 Ni 17 amorphous and icosahedral (i) quasi-crystal electrodes synthesized by mechanical alloying and subsequent annealing were measured in a three-electrode cell at temperatures of 298 and 328 K. During electrochemical hydrogenation, the maximum H/M (number of hydrogen atoms per metal atom) value for the i-phase electrode reached 1.4, which corresponds to a theoretical capacity of 570 mAh/g. The discharge capacities for both the amorphous and i-phase electrodes at 298 K increased with increasing charge/discharge cycles at the initial stage because of an activation process. The maximum discharge capacity for i-phase and amorphous electrodes at 298 K were 23.9 and 5.9 mAh/g, respectively, at a current density of 15 mA/g. The maximum discharge capacity for the i-phase electrode, however, reached about 88 mAh/g after the first cycle at 328 K and then decreased as the number of cycles increased. The structure of the i phase was stable even after the discharge process of the 25th cycle, but the amorphous electrode converted to (Ti,Zr)H 2 face-centered-cubic-type hydride, which substantially lowered its total discharge performance.

Magnetic Fields in Semiconductor Crystal Growth

We may define three main categories of crystal growth techniques: growth from solid, vapour, and melt. These three main categories of crystal growth methods need careful control of the phase change. We may introduce a subcategory, growth from the solution, which is strictly already included in the above definitions, and which represents crystal growth processes of solute from an impure melt. Figure 1 shows techniques commonly used for the crystal growth from the melt. All of these growth techniques can be referred to two main categories: meniscus-controlled crystal growth systems and confined crystal growth systems. In meniscus-controlled crystal growth systems (Czochralski technique, floating zone technique) there is a three-phase boundary at which crystal, melt and gaseous phase coexist. In confined crystal growth systems both crystal and melt are confined within a solid container. Such techniques can be divided into normal freezing method (in which the whole charge is melted initially and then progressively crystallized), and zone-melting method (in which a molten zone is established and traversed along an ingot). In those techniques a crystal–melt interface moves vertically or horizontally. The vertical directional solidification technique is commonly known as the Bridgman technique, while the horizontal directional solidification technique as the Chalmers technique. Zone-melting techniques are designed vertically or horizontally [1].