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ZrB2 powders were synthesized via a borothermal reduction reaction of ZrO2 with the assistance of NaCl under a flowing Ar atmosphere. The optimal temperature and reaction time were 1223 K and 3 h, respectively. Compared with the reactions conducted without the addition of NaCl, those performed with the addition of an appropriate amount of NaCl finished at substantially lower temperatures. However, the addition of too much NaCl suppressed this effect. With the assistance of NaCl, a special morphology of polyhedral ZrB2 particles covered with ZrB2 nanosheets was obtained. Moreover, the experimental results revealed that the special morphology was the result of the combined effects of B2O3 and NaCl. The formation of the special microstructure is explained on the basis of the "dissolution–recrystallization" mechanism. [ABSTRACT FROM AUTHOR]

TiB2 nanosheets were synthesized by the borothermal reduction of TiO2 in flowing argon atmosphere with the assistance of MgCl2. Phase transformation was studied by XRD and micromorphology of products was studied by SEM and TEM. In the experiment, the prepared TiB2 formed the nanoscale lamellar structure. These lamellas agglomerated together to be a net-like structure. Effects of reduction temperature, addition of MgCl2, and its amount were discussed in detail. The results indicated that the presence of MgCl2 accelerated the mass transfer of reactant. Moreover, the co-effects of MgCl2 and B2O3 contributed to the formation of TiB2 nanosheets. TiB2 could dissolve in MgCl2 and B2O3 at high temperature and then recrystallized during the cooling process. The products with a specific surface area of 99.32 m2 g−1 were obtained at 1373 K after reacting for 4 h with a MgCl2:TiO2 molar ratio of 1:1. [ABSTRACT FROM AUTHOR]

TiB2 nanosheets were synthesized by the borothermal reduction of TiO2 in flowing argon atmosphere with the assistance of MgCl2. Phase transformation was studied by XRD and micromorphology of products was studied by SEM and TEM. In the experiment, the prepared TiB2 formed the nanoscale lamellar structure. These lamellas agglomerated together to be a net-like structure. Effects of reduction temperature, addition of MgCl2, and its amount were discussed in detail. The results indicated that the presence of MgCl2 accelerated the mass transfer of reactant. Moreover, the co-effects of MgCl2 and B2O3 contributed to the formation of TiB2 nanosheets. TiB2 could dissolve in MgCl2 and B2O3 at high temperature and then recrystallized during the cooling process. The products with a specific surface area of 99.32 m2 g−1 were obtained at 1373 K after reacting for 4 h with a MgCl2:TiO2 molar ratio of 1:1. [ABSTRACT FROM AUTHOR]