DENSIFICATION OF LMH-2.
Abstract
The study of BeH2 crystallization process parameters has provided a partial phase diagram for the P-T regime of 120-250 C and 40-140 kpsi. It shows that both the product density and distribution of crystalline polymorphs, Phase 338-208 and Phase 378-295, are simple functions of the applied pressure and temperature. Hydrostatic compaction time does not appear to be a critical variable. A pressure of at least 40 kpsi (at about 200 C) and temperature of at least 130 C (with pressures above 90 kpsi) appears necessary for crystallization. The more thermally stable Phase 378-295 evidently has a higher density (0.77-0.78 g/cc) than does Phase 338-208 (0.73-0.74 g/cc). Phase 378-295 is formed preferentially at higher pressures, requiring about 110-120 kpsi for production in its pure form. Small changes in the concentration of the Li dopant or Be metal content do not noticeably affect crystallization or polymorph distribution. Undoped BeH2 was not crystallized under conditions of 140 kpsi at 205 C even after 4 hours. However, the density was increased to 0.70 g/cc. Encapsulation of BeH2 appears necessary for successful crystallization by hydrostatic compaction. Various types of metal thimbles and closures were tested as capsules for pre-compaction and crystallization steps.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1967
- Accession Number
- AD0384989
Entities
People
- E. M. Marlett
- G. J. Brendel