Phosphoric Acid → Calcium bis(metaphosphate)

Participants

Reaction Conditions

Reaction Steps

Representative acicular crystalline calcium metaphosphate fibers were prepared from a composition consisting of 1473.7 parts of 86.13% H3PO4, 128.4 parts of NaH2PO4H2O, 450.0 parts CaCO3, 9.6 parts Fe PO4 and about 500 parts distilled water providing a mole percent ratio of 58.3% P2O5, 37.6% CaO, 3.9% Na2O and 0.3% Fe2O3. The ingredients were thoroughly mixed and the composition was dried at a temperature of about 200° C. Then the composition was placed in a shallow high-temperature ceramic dish and placed in a furnance and heated to 200° C. overnight to drive off residual water. The temperature was increased over a period of about six hours to 1000° C. and maintained at 1000° C. for about one hour to form a melt. The temperature of the melt was then reduced to about 710° C. over a period of about 2 hours and crystallization was induced by quick chilling by opening the furnance door for about five seconds. After the crystallization was induced the temperature was maintained at 710° C. overnight and the crystallized composition was cooled and removed from the furnance. Acicular crystalline calcium metaphosphate fibers were then recovered from the crystallized composition by breaking it into small chunks and boiling in water to dissolve the soluble matrix and filtering drying the separated fibers. The recovered acicular crystalline calcium metaphosphate fibers are relatively uniform and were not further classified. These acicular fibers are thermally stable to about 970° C., have an average density of about 2.87 g/cc and generally a mean aspect ratio of about 100:1. The acicular fibers had an average diameter of 7.2 microns and an average surface area of 2013 cm2 /g as determined using the above described Sub-Sieve Sizer.

Provenance & Evidence