Process for plasma synthesis of rhenium nano and micro powders, and for coatings and near net shape deposits thereof and apparatus therefor
The process for the synthesis of rhenium powders comprises the injection of ammonium perrhenate powder through a carrier gas in a plasma torch of a plasma reactor operated using a mixture including hydrogen as the plasma gas, yielding metallic rhenium under the following chemical reaction: 2 NH 4 ReO 4 +4 H 2 →2 Re+N 2 ↑+8 H 2 O↑. The reactor is provided with a quench zone for cooling the metallic rhenium so as to yield rhenium nano and micro powders.
1. A process for the synthesis of rhenium powders comprising:
injecting ammonium perrhenate powder through a carrier gas in a plasma torch of a plasma reactor operated using a mixture including hydrogen as the plasma gas, yielding gaseous metallic rhenium under the following chemical reaction:
2 NH 4 ReO 4 +4 H 2 →2 Re↑+N 2 ↑+8 H 2 O↑; and
quenching said gaseous metallic rhenium, yielding rhenium powders,
wherein about 2 moles of hydrogen gas (H 2 ) are provided for each mole of ammonium perrhenate (NH 4 ReO 4 ).
2. A process as recited in claim 1 , wherein said rhenium powders include at least one of nano and micro powders.
3. A process as recited in claim 1 , wherein quenching said gaseous metallic rhenium includes using a quench gas to rapidly cool said gaseous metallic rhenium.
4. A process as recited in claim 3 , wherein said quench gas includes at least one of argon and hydrogen.
5. A process as recited in claim 1 , wherein said carrier gas include argon.
6. A process as recited in claim 1 , wherein said plasma torch is operated at near atmospheric pressure.
7. A process as recited in claim 1 , wherein said chemical reaction involves the following transformations:
2 NH 4 ReO 4 →Re 2 O 7 +2 NH 3 ↑+H 2 O↑;
2 NH 3 →N 2 +3 H 2 ;
Re 2 O 7 →2 Re+7/2 O 2 ↑; and
Re 2 O 7 +7 H 2 →2 Re+7 H 2 O↑;
wherein in operation, in statu nascendi formed rhenium oxide vapour is reduced by the in statu nascendi formed hydrogen released through the reaction of decomposition of the ammonia.
8. A process as recited in claim 1 , wherein said chemical reaction involves i) thermal decomposition of ammonium perrhenate, yielding Re 2 O 7 ; and ii) thermal decomposition of the formed Re 2 O 7 to metallic rhenium and oxygen at about 800° C.
9. A process for rhenium coating of a substrate comprising synthesizing rhenium powders using the process recited in claim 1 and impacting the formed rhenium powders on the substrate before complete solidification of said formed rhenium powders.