Fundamental Investigation of Phosphate Bonding.
NTIS: PB/84-220748 :72 pages
This investigation utilized single crystals to study phosphate bonding, eliminating surface area and particle shape as variables and allowing the effect of crystallographic orientation to be evaluated. The morphology of the reaction products when h3po4 was reacted with alumina single crystals was related to the crystal face index. Star-shaped dendrites formed on the low index faces and equiaxed crystals formed on faces that did not correspond to low index planes and polycrystalline samples. The tensile strength of (1120) and (0001) alumina bicrystals increased as their surface finish was improved. The tensile strength of (1120) alumina bicrystals bonded with nah2po4.H2o or glass h are greater than (0001) bicrystals produced under the same conditions. The tensile strength of (1120) alumina bicrystals bonded with nah2po4.H2o varies with the amount of rotational mismatch between the crystals. Strength maximums occurred at 0 deg. and 180 deg. and a minimum of 90 deg. It appears that this strength pattern is related to the twofold symmetry of this plane. Combination of both rotational and tilt mismatch reduced the strength of (1120) and (0001) bicrystals to almost zero. The strength decreases associated with these types of bicrystal mismatches could be related to differences in thermal expansion with direction or bond misalignment.
CP; Final Contract Report;
NTIS Accession No.
Georgia Institute of Technology