Further experiments on the preparation of thorium oxide microspheres using mixtures of ethyl- and isobuthyl-alcohol instead of iso-propyl alcohol were carried out to verify the previously proposed mechanism of microsphere formation.
The mixed alcohol-water-ammonium nitrate system has a markedly different type of equilibrium diagram from that of isopropyl alcohol-water-ammonium nitrate system, and the shape of the equilibrium curve possessing minimum points vary with the composition of the mixed alcohol.
Most of the results obtained on microsphere preparation with various ammonium nitrate concentrations in thorium hydrooxide sols at various mixed alcohol compositions showed fair agreement with the microsphere formation region estimated from the equilibrium diagram. The amorphous gel formation in the expected microsphere formation region may be explained from the “oil in water” type of emulsion formed by the mixing of the two liquid phases.
The average particle diameter of the thorium oxide microspheres may be controlled within a range of 420μ at constant injection velocity by changing the mixed alcohol composition of the mixed alcohol, or the ammonium nitrate concentration in the sol.
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