Method of manufacturing high-surface-area silicon
View Patent ↗A method for synthesis of high surface-area (>100 m 2 /g) and nanosized (≦100 nm) silicon powder by initiation of self-sustained combustion reaction in a mixture of silicon dioxide and magnesium powders in a sealed reactor chamber under pressurized inert gas atmosphere. A specific feature of the method is rapid cooling of the product at a rate of 100 K/s to 400 K/s in the area directly behind the combustion front.
1. A method of manufacturing high-surface-area silicon powder from silicon dioxide (SiO 2 ) and magnesium (Mg) in a sealable reactor, the silicon powder having surface area equal to or greater than 100 m 2 /g and a particle size equal to or less than 100 nm, the method comprising the following steps:
(1) preparing a homogeneous reactant green mixture from silicon dioxide (SiO 2 ) and magnesium (Mg);
(2) loading the reaction mixture into the sealable reactor;
(3) filling the reactor with an inert gas and providing optimum inert gas pressure inside the reactor;
(4) providing initial local heating of the powder mixture and initiating a combustion reaction;
(5) causing self-sustained reaction under the effect of exothermic heat of the reaction and obtaining a combustion product that comprises silicon and a magnesium oxide phase;
(6) cooling the combustion product at a rate in the range of 100 K/s to 400 K/s; and
(7) carrying out post-synthesis treatment of the product that involves leaching in order to completely eliminate the magnesium oxide phase followed by short-term milling.
2. The method of claim 1 , wherein silicon dioxide comprises a powder with particle dimensions ranging from 1 to 100 μm and wherein magnesium comprises a powder with particle dimensions ranging from 50 to 200 μm.
3. The method of claim 1 , wherein to produce 1 kg of silicon powder, silicon dioxide is used in an amount of about 2146 g, and magnesium is used in an amount of about 868 g.
4. The method of claim 2 , wherein to produce 1 kg of silicon powder, silicon dioxide is used in an amount of about 2146 g, and magnesium is used in an amount of about 868 g.
5. The method of claim 1 , wherein initial local heating is carried out by locally heating about 1 mm 3 of the homogeneous reactant green mixture to the melting point of magnesium.
6. The method of claim 2 , wherein initial local heating is carried out by locally heating about 1 mm 3 of the homogeneous reactant green mixture to the melting point of magnesium.
7. The method of claim 3 , wherein initial local heating is carried out by locally heating about 1 mm 3 of the homogeneous reactant green mixture to the melting point of magnesium.
8. The method of claim 1 , wherein optimum inert gas pressure inside the reactor ranges from 10 to 20 atm.
9. The method of claim 2 , wherein optimum inert gas pressure inside the reactor ranges from 10 to 20 atm.
10. The method of claim 3 , wherein optimum inert gas pressure inside the reactor ranges from 10 to 20 atm.
11. The method of claim 1 , wherein cooling of the combustion product at a rate ranging from 100 K/s to 400 K/s is carried out directly behind the combustion front.
12. The method of claim 2 , wherein cooling of the combustion product at a rate ranging from 100 K/s to 400 K/s is carried out directly behind the combustion front.
13. The method of claim 3 , wherein cooling of the combustion product at a rate ranging from 100 K/s to 400 K/s is carried out directly behind the combustion front.
14. The method of claim 1 , wherein leaching is carried out by treating the combustion product with 36% hydrochloric acid under normal conditions for 3 hours.
15. The method of claim 14 , wherein 36% hydrochloric acid is used in a 1:1 ratio to the magnesium oxide phase.