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Silicothermic synthesis of phase‐pure HfB 2 fine powder
Author(s) -
Zhang Jinhua,
Xiong Si,
Wang Jingran,
Ni Yue’e,
Ke Changming
Publication year - 2021
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.17498
Subject(s) - sodium silicate , raw material , silicon , phase (matter) , evaporation , halide , sodium , materials science , silicate , chemical engineering , nuclear chemistry , chemistry , inorganic chemistry , metallurgy , organic chemistry , physics , engineering , thermodynamics
Abstract Phase pure and nano‐sized hafnium diboride (HfB 2 ) fine powder was prepared via a novel sustainable silicothermic route at 1100°C from inexpensive raw materials HfO 2 , Na 2 B 4 O 7 and Si. By introducing sodium oxysalts as source of Na 2 O into the batch mixtures, the SiO 2 / Na 2 O modulus in the melt were reduced from 5:1 to 2:1, and the original water‐insoluble byproduct SiO 2 was taken by the melt at test temperature and converted into water soluble sodium silicate (Na 2 Si 2 O 5 ) which was easily removed from the reacted mass via simple hot water washing. Consequently, the aqua sodium silicate could be readily recycled and used as a precursor for preparing many other valuable materials due to absence of foreign salts (eg halides, especially in the molten salt‐assisted synthesis process) in the synthesis process, and the relevant environmental concerns could be alleviated. Using excessive amount of 20 wt% Si and 15 wt% Na 2 B 4 O 7 as compensation for the evaporation loss of silicon, in the form of SiO (g), and B 2 O 3 in the reduction process, a high reaction extent was achieved and HfO 2 and Na 2 B 4 O 7 were completely converted into HfB 2 at 1100°C.