Phase diagram of the thermodynamically nonequilibrium state for the MgO-B2O3-18%MgCl2-H2O system at 0°C

The supersaturated solutions of MgO-B 2 O 3 -18%MgCl 2 -H 2 O with different mole ratios MgO: B 2 O 3 were prepared and kept at 0 ′ 0.1°C. The crystallization paths of boric acid, Mg-borates and Mg-oxychloride from the solutions have been determined by chemical analysis of the solution samples taken at a given time interval during crystallization, then the liquid-solid phase diagram of the thermodynamically nonequilibrium state for the MgO-B 2 O 3 -18%MgCl 2 -H 2 O system at 0°C has been constructed. In this phase diagram, there appears five crystallization fields, boric acid (H 3 BO 3 ), mcallisterite (MgO.3B 2 O 3 .7.5H 2 O), hungtsaite (MgO. 2B 2 O 3 .9H 2 O), inderite (2MgO.3B 2 O 3 .15H 2 O), and magnesium oxychloride (5Mg(OH) 2 .MgCl 2 .8H 2 O).