Aerosol reduction/expansion synthesis (A-RES) for zero valent metal particles
Various embodiments provide methods of forming zero valent metal particles using an aerosol-reductive/expansion synthesis (A-RES) process. In one embodiment, an aerosol stream including metal precursor compound(s) and chemical agent(s) that produces reducing gases upon thermal decomposition can be introduced into a heated inert atmosphere of a RES reactor to form zero valent metal particles corresponding to metals used for the metal precursor compound(s).
1. A method of forming metal particles comprising:
forming an aerosol stream comprising an inert carrier gas, one or more precursor compounds and a chemical agent that produces reducing gases upon thermal decomposition, wherein each of the one or more precursor compounds comprises one or more metals, wherein the aerosol stream comprises a solid concentration ranging from about 0.01% to about 50% by volume; and
flowing the aerosol stream through a heated inert atmosphere in a reduction expansion synthesis (RES) reactor to form a plurality of zero valent metal particles corresponding to the one or more metals of the one or more precursor compounds,
wherein a temperature of the heated inert atmosphere in the RES reactor is sufficient to thermally decompose the chemical agent to produce the reducing gas, and
wherein the plurality of zero valent metal particles include hollow sphere particles having a diameter ranging from about 10 nm to about 10,000 nm and pores in the order of about 1% to about 80% of the size of the hollow sphere particles.
2. The method of claim 1 , wherein each particle of the plurality of zero valent metal particles is a metal alloy particle comprising two or more distinct metals.
3. The method of claim 2 , further comprising controlling a metal ratio between the two or more distinct metals by controlling a metal ratio between the precursor compounds in the aerosol stream, wherein the precursor compounds each comprise different metal atoms.
4. The method of claim 1 , wherein the temperature of the heated inert atmosphere in the RES reactor is between a decomposition temperature of the chemical agent and a melting temperature of each of the one or more metal particles.
5. The method of claim 1 , wherein the one or more precursor compounds comprise oxides, hydroxides, nitrates, hydrated nitrates, nitrides, oxide-nitrides, or halogens of one or more metals, and wherein each of the one or more metals comprises a metal in one or more columns of IB, IIB, VB, VIB, VIIB, IA, IIA, IIIA, or IVA in the periodic table.
6. The method of claim 1 , wherein the chemical agent that produces reducing gases upon thermal decomposition comprises one or more nitrogen-hydrogen-containing molecules comprising urea [(NH 2 ) 2 CO] or a compound containing —NH or —NH 2 .
7. The method of claim 1 , wherein each of the plurality of zero valent metal particles comprises a porous nanoparticle having a pore size ranging from about 1 nm to about 100 nm.
8. A method of forming metal particles comprising:
forming an aerosol stream comprising a metal precursor compound with a nitrogen-hydrogen (N—H) containing molecule in a carrier gas, wherein the metal precursor compound comprises a positive valent metal, wherein the aerosol stream comprises a solid concentration ranging from about 0.01% to about 50% by volume;
flowing the aerosol stream through a heated inert atmosphere in a vertically oriented reduction expansion synthesis (RES) reactor to form a plurality of zero valent metal particles corresponding to the positive valence metal; and
collecting the plurality of zero valent metal particles at a bottom end of the vertical RES reactor,
wherein the plurality of zero valent metal particles include hollow sphere particles having a diameter ranging from about 10 nm to about 10,000 nm and pores in the order of about 1% to about 80% of the size of the hollow sphere particles.
9. The method of claim 8 , wherein the heated inert atmosphere in the RES reactor has a temperature ranging from about 1000° C. to about 1500° C.
10. The method of claim 8 , wherein the aerosol stream has a flow rate ranging from about 100 cc/min to about 1500 cc/min through the heated inert atmosphere.
11. The method of claim 8 , wherein the aerosol stream flowing through the heated inert atmosphere for a residence time of less than 100 seconds.
12. The method of claim 8 , wherein the plurality of zero valent metal particles are formed of at least one metal selected from the group consisting of Ni, Sb, Co, In, Fe, and Ga.