PREPARATION OF HIGH-DENSITY LIGHT METAL HYDRIDE-2.

Studies of the BeBH42AlR3 reaction system led to the discovery of new forms of beryllium hydride, the borane-terminated beryllium hydrides, BeH2xBH32. These materials have good physical and chemical stability and are essentially equivalent to pure BeH2 in theoretical propellant performance. They are, like BeH2, amorphous and of low density, and studies aimed at inducing BeH2xBH32 crystallization met with very limited success. Beane Ethyl Corporation BeH2 was shown to dissolve smoothly in AlCH33, forming a liquid complex. However, AlCH33 was known to form strong bonds with BeH2, and no attempt was made to recover BeH2 from the complex. Pressure studies of Beane crystallization up to 150 kilobars 2.2 million psi were carried out, and unadulterated Beane was crystallized for the first time. The most important factors in crystallization proved to be the time for which samples were held at given P-T conditions, and the rate at which they were quenched back to ambient conditions. A tentative mechanism for BeH2 crystallization was developed, and a phase diagram was prepared. Lithium-doped BeH2 was crystallized using hydrothermal pressure apparatus. Scale-up of this technique to multipound batches is well within the scope of current high-pressure technology. Author