FABRICATION AND PROPERTIES OF DENSE BERYLLIUM OXIDE

Journal Article · Sat Jul 01 04:00:00 EDT 1961 · J. Nuclear Materials

DOI:https://doi.org/10.1016/0022-3115(61)90125-8· OSTI ID:4839989

Carniglia, S C; Hove, J E

Nuclear grade beryllium oxide powders from commercial suppliers may be pressed at temperatures of 1500 deg to 1900 deg C and under pressures from 2000 to 6000 psi in graphite dies into a variety of shapes having densities in the range 98 to 100% of the theoretical value. Addition of 1% MgO facilitates the process and improves the rate and uniformity of densification. The compaction of BeO as a function of pressure, temperature and time may be deacribed by a flow relation involving a viscosity and a critical shear stress for grain boundary movement. Thermal expansion is isotropic to about 1700 deg C and is well described to 2000 deg C by a quadratic function of the temperature. The specific heat of BeO at 1500 deg C is 0.52 cal/g- deg C, slightly above the Dulong and Petit value. From 500 deg to about 1800 deg C the thermal conductivity decreases as 1/T, from a high value at room temperature of about 0.50 cal/cm- deg C for dense material. A decrease in density of 5% diminished the thermal conductivity by approximately 13%. Information given earlier on the creep, elastic and anelastic properties of dense material was extended, and relations were employed showing that significant fractions of thermal stresses encountered in practice may be relaxed if given time. An elasticity due to grain boundaries also appears to confirm the view on flow during densification in hot pressing. A preliminary estimate of rupture strength for completely dense material with grain size of approximately 35 mu is 36,000 psi at room temperature. Lowering the density 1% reduces the strength about 4100 psi. The status of knowledge of other properties is reviewed briefly. (auth)

• Research Organization: Atomics International, Canoga Park, Calif.
• NSA Number: NSA-15-031233
• OSTI ID: 4839989
• Journal Information: J. Nuclear Materials, Journal Name: J. Nuclear Materials Vol. Vol: 4
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ANISOTROPY
BERYLLIUM OXIDES
COMPACTING
DENSITY
DIES
ELASTICITY
EXPANSION
FABRICATION
FAILURES
FLUID FLOW
GRAIN BOUNDARIES
GRAIN SIZE
GRAPHITE
HIGH TEMPERATURE
HOT WORKING
IMPURITIES
MAGNESIUM OXIDES
MATHEMATICS
METALS, CERAMICS, AND OTHER MATERIALS
POWDERS
PRESSURE
SHEAR
SPECIFIC HEAT
STRESSES
TEMPERATURE
TENSILE PROPERTIES
THERMAL CONDUCTIVITY
THICKNESS
VISCOSITY