Conditions of Synthesis of Chrysotile Fibers under Hydrothermal-Dehydration Process

Abstract

Raw material compositions and reaction conditions were studied in detail for the synthesis of chrysotile fibers under hydrothermal-dehydration process, under which as previousley reported the fibers elongated.
A suitable ratio of composition of the starting materials were as follows; silcic unhydride 1mol, brucite 2-2.5mol, magnesium bromide 3/4-1mol which catalyzed the formation of the fibers and promoted dehydration from the slurry, and water about 50mol which constituted 10% fill of the pressured space.
In this case, the slurry showed pH=7.0±0.3 at room temperature, and pressure of hydrogen evolved by the dehydration reaction was the same as the water pressure after the reaction. From this fact, it was seemed that the formation and growth of fibers were occured at relatively low water pressure which condition is analogous to the formation of natural chrysotile fibers.
Effects of other substances were examined, and it was shown from the results that magnesium bromide not only provided a suitable pH to the slurry, but also was required for the formation of intermediates in the crystallization of the fibers.