Silicon-barium alloys are produced by reacting reduced barium compounds (e.g., BaO or BaCO₃) with silicon (or ferrosilicon) using either the electrosilicate thermal method or the aluminum-thermal method.
1. Thermal Method Of Silicon Production (Smelting In An Electric Arc Furnace)
Applicability: Suitable for large-scale industrial production, low cost but higher energy consumption.
Raw Materials:
Barium source: Barium oxide (BaO) or barium carbonate (BaCO₃).
Reducing agent: ferrosilicon (FeSi75), silicon powder (Si)
Melting Agent: Lime (CaO, regulates slag fluidity)
Technological process:
Mixing ingredients:
Mix BaO (or BaCO₃), ferrosilicon and lime according to the stoichiometric ratio (BaO : Si ≈ 1 : 1).
Reduction in an arc furnace:
In a three-phase electric arc furnace heated to 1400~1600°C, BaO is reduced by Si: BaO+
Si→BaSi+SiO2
Iron (Fe) in ferrosilicon does not participate in the reaction and turns into an alloy (Fe-Ba-Si).
Slag Gold Department:
A silicon-barium alloy (denser) sinks to the bottom of the furnace, calcium silicate slag (CaSiO₃) floats.
Casting and crushing:
The liquid alloy is poured into ingots and, after cooling, is crushed into lump or granular products.
Specifications:
The product contains about 30%~50% Ba, the rest is Si and a small amount of Fe.
The alkalinity of the slag (CaO/SiO₂) must be controlled to increase the recovery rate of barium.
2. Thermal Method Of Aluminum Production (Self-Propagating High-Temperature Synthesis, SHS)
Application: Suitable for low-volume production of high-purity SiBa, the reaction is rapid and requires strict control.
Raw Materials:
Barium source: BaO or BaCO₃.
Reducing agent: aluminum powder (Al).
Heat generator: potassium chlorate (KClO₃, auxiliary exothermic)
Process:
Mixing ingredients:
Mix BaO, Al powder and a small amount of KClO₃ according to the stoichiometric ratio (BaO : Al ≈ 3 : 2).
Calcination reaction:
Burning in a magnesium crucible to start an aluminothermic reaction (above 2000°C):
3BaO + 2Al → 3Ba + Al2O3 + large amount of heat.
The resulting barium (Ba) combines with silicon (Si) to form a BaSi alloy.
Sedimentary separation:
The liquid silicon-barium alloy sinks to the bottom, and the Al₂O₃ slag floats.
Refining and casting:
An inert gas (e.g., Ar) is passed through the alloy to remove impurities, if necessary, and the ingots are cast.
Specifications:
The product can contain up to 60% or more Ba, with a high degree of purity.
The reaction proceeds violently, explosion-proof measures are required, and is suitable for laboratory research or the preparation of special alloys.
