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Mechanochemical synthesis and annealing of tungsten di‐ and tetra‐boride
Author(s) -
Long Ying,
Wu Zong,
Zheng Xin,
Lin HuaTay,
Zhang Fenglin
Publication year - 2020
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.16788
Subject(s) - boride , crystallinity , annealing (glass) , tungsten , materials science , molar ratio , nuclear chemistry , metallurgy , analytical chemistry (journal) , chemical engineering , chemistry , composite material , organic chemistry , engineering , catalysis
Tungsten diboride and tetra‐boride were synthesized by a combination of mechanochemical method and the subsequent heat treatment. To clarify the formation process of tungsten diboride (WB 2 ) and tetra‐boride (WB 4 ) using W‐B mixture system with variable B concentration, the effects of ball‐to‐powder ratio, W to B molar ratio on mechanochemical process were studied, and the relationship between phase composition and annealing temperature was built. The results show that, the synthesis of WB 2 with W:B = 1:5 can be improved by increasing ball‐to‐powder ratio from 4:1 to 6:1, but no WB 4 phase can be directly synthesized by mechanochemical method. WB 2 (AlB 2 ‐WB 2 , P6/mmm) phase can be only synthesized with W to B molar ratio of 1:4 and 1:5. Further increase in B content to W:B = 1:6 or less, W was present as the main phase with high crystallinity (>71%). WB 4 phase was formed as an annealing temperature as low as 1000°C, which was not stable and may decompose to WB 2 (WB 2 ‐WB 2 , P6/mmm) phase with the increase in temperature. The decomposition temperature of WB 4 can be improved by increasing the B content. Compared with the W‐B mixtures (W:B = 1:12) being milled for 1 hour, the powders milled for 40 hours present 20% higher of WB 4 weight fraction after being annealed at 1400°C for 2 hours.