Abstract: The new self-propagating high temperature synthesis(SHS) metallurgy method used to prepare boron powder was studied, and the adiabatic temperature is 2 604 K through calculating, which is higher than the SHS criterion parameter of 1 800 K. So the SHS reaction is feasible. Influences of addition MgO and warm-up temperature on adiabatic temperature and the thermodynamic data of correlative reactions were analysed. Results of DTA indicate that the apparent activation energy of exothermic peak is 903.75 kJ/mol and reaction order n is 1. Phases of combustion and leached products were confirmed by XRD, which proves that the three-step leaching technic is feasible. The effects of the initial conditions of self-propagating high temperature synthesis on boron purity were studied. The purity of boron powders reach 92.43% and the average diameter of boron powders is 0.5-0.8 μm.
Preparation of boron powder by self-propagating high temperature synthesis metallurgy
Abstract:
The new self-propagating high temperature synthesis(SHS) metallurgy method used to prepare boron powder was studied, and the adiabatic temperature is 2 604 K through calculating, which is higher than the SHS criterion parameter of 1 800 K. So the SHS reaction is feasible. Influences of addition MgO and warm-up temperature on adiabatic temperature and the thermodynamic data of correlative reactions were analysed. Results of DTA indicate that the apparent activation energy of exothermic peak is 903.75 kJ/mol and reaction order n is 1. Phases of combustion and leached products were confirmed by XRD, which proves that the three-step leaching technic is feasible. The effects of the initial conditions of self-propagating high temperature synthesis on boron purity were studied. The purity of boron powders reach 92.43% and the average diameter of boron powders is (0.50.8 μm.)
Fig.4 Photos of combustion products (a)—B2O3-Mg reaction system through ignition; (b)—B2O3-Mg reaction system through constant temperature explosion; (c)—B2O3-Mg-KCl reaction system through constant temperature explosion; (d)—B2O3-Mg-NaF reaction system through direct explosion
Fig.5 XRD of burned products (a)—B2O3-Mg reaction system through ignition; (b)—B2O3-Mg reaction system through thermally explosion; (c)—B2O3-Mg-KCl reaction system through thermally explosion; (d)—B2O3-Mg-NaF reaction system through thermally explosion
Table 1 Spectral and chemical analyses of elements
Element
Mass fraction/%
B
92.430
Mg
2.710
O
4.310
Si
0.010
Ca
0.030
Fe
0.003
3.4SHS反应初始条件对硼粉纯度的影响
3.4.1 反应物摩尔比的影响
图6 浸出产物的X射线衍射谱
Fig.6 XRD patterns of leaching products (a)—After firstly leaching by HCl for igniting combustion products; (b)—After leaching by NaOH for igniting combustion products; (c)—After secondly leaching by HCl for igniting combustion products; (d)—After three-step leaching for thermally exploding products