Influence of disodium hydrogen phosphate dodecahydrate on hydrothermal formation of hemihydrate calcium sulfate whiskers

摘要

The influence of Na_2HPO_4·12H_2O on the hydrothermal formation of hemihydrate calcium sulfate(CaSO_4·0.5H_2O) whiskers from dihydrate calcium sulfate(CaSO_4·2H_2O)at 135 ℃ was investigated.Experimental results indicate that the addition of phosphorus accelerates the hydrothermal conversion of CaSO_4·2H_2O to CaSO_4·0.5H_2O via the formation of Ca_3(PO_4)_2 and produces CaSO_4-0.5H_2O whiskers with thinner diameters and shorter lengths.Compared with the blank experiment without Na_2HPO_4·12H_2O,the existence of minor amounts(8.65 ×10^(-4)-4.36 × 10^(-3) mol/L) of Na_2HPO_4·12H_2O led to a decrease in the diameter of CaSO_4·0.5H_2O whiskers from 1.0-10.0 to 0.5-2.0 μm and lengths from 70-300 to50-200 μm.