Method of making non-hollow, non-fragmented spherical metal or metal alloy particles
View Patent ↗The invention is directed to systems and methods for making non-hollow, non-fragmented spherical metal or metal alloy particles using diffusion dryers.
1. A method for the manufacture of spherical particles comprising one or more metals, comprising the steps:
a. providing a precursor solution comprising a solvent and one or more thermally decomposable metal containing compounds;
b. forming an aerosol comprising finely divided droplets of the precursor solution dispersed in a carrier gas;
c. passing the aerosol through one or more diffusion dryers, wherein 10% to 50% of the solvent in the aerosol particles is removed;
d. heating the aerosol wherein, upon heating, spherical metal particles are formed,
e. quenching the metal particle aerosol, and
f. collecting the spherical metal particles,
wherein the time in the diffusion dryer is between 25% and 200% of the time the particles are being heated of step d, wherein the spherical metal particles collected are non-fragmented, non-hollow.
2. The method of claim 1 wherein the metal containing compounds of step a contain one or more of the following metals: Ag, Au, Bi, Cd, Co, Cr, Cu, Fe, Ge, Hg, In, Ir, Mn, Mo, Ni, Pd, Pb, Pt, Re, Rh, Ru, Sb, Sn, Ti, W, Zn.
3. The method of claim 1 wherein the quenching of step e has a collection temperature that does not condense any solvent onto the spherical metal particles.
4. The method of claim 1 wherein the droplet concentration in forming the aerosol in step b is below the concentration where collisions and subsequent coalescence of the droplets results in a 10% reduction in droplet concentration.
5. The method of claim 1 wherein passing the aerosol through one or more diffusion dryers in step c 20% to 40% of the solvent in the aerosol particles is removed.
6. The method of claim 1 wherein the heating of step d is between 600° C. and 1500° C.
7. The method of claim 1 where the heating of step d is above the decomposition temperature of the metal containing compounds but below the melting point of the formed spherical metal particles.
8. The method of claim 1 wherein the carrier gas of step b comprises air.
9. The method of claim 1 wherein the carrier gas of step b comprises an inert gas.
10. The method of claim 1 wherein the carrier gas of step b comprises nitrogen.
11. The method of claim 10 wherein a co-solvent is present in an amount of about 1% to about 50% by volume of the solution.
12. The method of claim 1 wherein the carrier gas of step b comprises a reducing gas.
13. The method of claim 1 wherein the carrier gas of step b comprises nitrogen gas and 4% hydrogen gas.
14. The method of claim 1 wherein the precursor solution of step a further comprises a co-solvent.
15. The method of claim 14 wherein the co-solvent comprises an organic compound having 1 to 5 carbons.
16. The method of claim 15 wherein the co-solvent comprises an alcohol.
17. The method of claim 15 wherein the precursor solution of step a comprises seed particles, wherein the seed particles are colloids.
18. The method of claim 1 wherein the precursor solution further comprises seed particles.