Low Temperature Synthesis of Phase Pure MoAlB Powder in Molten NaCl

Cheng Liu; Zhaoping Hou; Quanli Jia; Xueyin Liu; Shaowei Zhang

doi:10.3390/ma13030785

Low Temperature Synthesis of Phase Pure MoAlB Powder in Molten NaCl

Materials (Basel). 2020 Feb 9;13(3):785. doi: 10.3390/ma13030785.

Authors

Cheng Liu¹, Zhaoping Hou², Quanli Jia³, Xueyin Liu⁴, Shaowei Zhang¹

Affiliations

¹ College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, UK.
² College of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, China.
³ Henan Key Laboratory of High Temperature Functional Ceramics, Zhengzhou University, Zhengzhou 450052, China.
⁴ College of Civil Engineering and Architecture, Quzhou University, Quzhou 32400, Zhejiang, China.

Abstract

MoAlB fine powders were prepared in molten NaCl from Al, B and Mo powders. The effects of key parameters affecting the synthesis process and phase morphology were examined and the underpinning mechanisms proposed. MoAlB product particles exhibited different shapes/sizes, as follows: spherical grains (1~3 μm), plate-like particles (<5 μm in diameter) and columnar crystals with lengths up to 20 μm and diameters up to 5 μm, resultant from different reaction processes. Phase pure MoAlB was synthesised under the following optimal conditions: use of 140% excess Al and 6 h of firing at 1000 °C. This temperature was at least 100 °C lower than required by other methods/techniques previously reported. At the synthesis condition, Mo first reacted with Al and B, forming Al₈Mo₃ and MoB, respectively, which further reacted with excess Al to form Al-rich Al-Mo phases and MoAlB. The Al-rich Al-Mo phases further reacted with the residual B, forming additional MoAlB. The molten NaCl played an important role in accelerating the overall synthesis process.

Keywords: MoAlB; NaCl; boron; low temperature; molten salt synthesis.