Mathematical modeling and optimization strategies (genetic algorithm and knowledge base) applied to the continuous casting of steel

Potassium, rubidium and cesium hydrides as dehydrogenation catalysts for the lithium amide/magnesium hydride system

The 2LiNH2/MgH2 system has been identified as an attractive system for hydrogen storage, but suitable catalysts are needed to reduce the hydrogen desorption temperature and improve the rates of reaction. One of the most effective catalysts for lowering the desorption temperature and improving the desorption rate from this system has been KH. In this work a new catalytic additive, rubidium hydride (RbH), was synthesized, and its effects on hydrogen desorption from the 2LiNH2/MgH2 system were studied and compared to those of KH. Temperature-programmed desorption measurements showed that the addition of approximately 3 mol % RbH lowered the desorption temperature of the system by 94 °C, which is somewhat better than KH. Desorption enthalpies for the catalyzed samples were found to be approximately 42 kJ/mol, which is significantly lower than the 65 kJ/mol that was found for the uncatalyzed mixture. The hydrogen desorption rate of the RbH-doped sample was found to be approximately twice as fast as the KH-dope...

Rubidium Hydride: An Exceptional Dehydrogenation Catalyst for the Lithium Amide/Magnesium Hydride System

Zone refining is one of the most important procedures to purify germanium crystals for the fabrication of detectors in our laboratory. In order to properly zone refine high-purity germanium crystals, it is important to develop perfect cleaning procedures for raw materials, quartz tubes, and the containers holding raw materials. Additionally, vacuum levels, container types, the correct combination of ambient gases, the speed of zone travel, and the ratio of ingot length to molten zone length, all need to be carefully studied in order to obtain the best results possible. In this work, we investigate a number of influential factors in perfecting high-purity germanium crystal growth, specifically: cleaning procedures, boat composition, vacuum levels in the chamber, zone travel speed, and the ratio of ingot length to molten zone length. Using the van der Pauw Hall technique, we were able to measure the electrical properties of zone-refined ingots and analyze the origin and distribution of three main impurity elements (boron, aluminum and phosphorus) thereby allowing us to study potential contamination sources. After detailed analysis on the various influential factors, we were able to optimize the zone-refining procedures.

Investigation of influential factors on the purification of zone‐refined germanium ingot

Numerical study and experimental investigation of zone refining in ultra-high purification of gallium and its use in the growth of GaAs epitaxial layers

M.J.S. Bernadou

Papers

Numerical modeling and optimization of zone refining