| Abstract
| - Reaction of magnesium sulfate with aqueous ammonia in a hydrothermal condition (150−180 °C) produced a fibrous magnesium hydroxide sulfate hydrate (MHSH) with a compositioncorresponding to a stoichiometry of 4.34Mg(OH)2·MgSO4·xH2O. Chemical compositionanalysis showed that the quantity of x was more likely to be 2 rather than the well-known3. The MHSH whiskers were about 0.3−2 μm in diameter and 40−100 μm in length, withan aspect ratio no less than 100. Selected area electron diffraction (SAED) and X-raydiffraction patterns (XRD) showed the whiskers were well-crystallized with an orthorhombicstructure. An interesting superlattice was observed from the ED patterns but thissuperstructure was unstable under the radiation of a high-energy electron beam especiallyunder HREM conditions. Several techniques such as XRD, TEM, EDS, HREM, XPS, TGA-DTA, FTIR, etc. were used to characterize the structural features and thermal behavior ofthe experimental products. Our sample of fibrous MHSH was found to lose two hydrationwaters at about 330 °C, to further decompose at higher treatment temperature, and totransform finally into MgO near 1000 °C.
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