Functionally coated non-oxidized particles and methods for making the same
Air-stable coated particles, which include an oxidizable core having a coating substantially encompassing the oxidizable core, where the coating comprises a first organic ligand and/or a second organic ligand, are disclosed and described. The coated particles can also be substantially free of an oxide layer, especially oxide layers around the oxidizable core. As such, the coating of organic ligand(s) acts as a protective or passivating coating. The air-stable coated particles can be formed via a particle size-reduction process. An oxidizable particulate can be crushed and contacted with a first organic ligand and subsequently with a second organic ligand. The process conditions are maintained such that an oxide layer is preempted from forming on the oxidizable core. Such materials can be effective as high energy density additives for various fuels, pyrotechnic, ionic liquids, and rocket propellant applications and for biomedical applications.
1. A method of forming air-stable coated particles, comprising:
crushing an oxidizable particulate, wherein the step of crushing is a wet milling process including a wetting agent in which a first organic ligand and/or a second organic ligand is substantially soluble;
contacting the crushed oxidizable particulate with the first organic ligand to form an intermediate particulate; and
contacting the intermediate particulate with the second organic ligand such that the intermediate particulate is comminuted sufficient to form a particulate oxidizable core which is substantially coated by a ligand coating formed of at least one of the second organic ligand and the first organic ligand to form the air-stable coated particles and wherein the ligand coating substantially preempts formation of an oxide layer of the oxidizable core on wherein the wetting agent is hexane or jet fuel, and wherein the oxidizable particulate consists essentially of boron, aluminum, magnesium, boron carbide, boron nitride or aluminum carbide.
2. The method of claim 1 , wherein the second organic ligands displaces at least a portion of the first organic ligands.
3. The method of claim 1 , wherein the second organic ligands substantially displaces the first organic ligands.
4. The method of claim 1 , wherein the step of crushing is accomplished by ball milling, planar milling, roll milling, ultrasonic milling, or combinations thereof.
5. The method of claim 1 , wherein the step of crushing is accomplished by homogenous ball milling.
6. The method of claim 1 , wherein the step of crushing occurs in the presence of the first organic ligand.
7. The method of claim 1 , wherein the step of crushing is sufficient to form coated particles having an average diameter from about 30 nm to about 100 nm.
8. The method of claim 1 , wherein the oxidizable particulate has an average starting diameter from about 500 nm to about 1.5 μm.
9. The method of claim 1 , wherein the first organic ligand is weakly binding.
10. The method of claim 1 , wherein the second organic ligand is strongly binding.
11. The method of claim 1 , wherein the first organic ligand and/or second organic ligand is non-polar.
12. The method of claim 1 , wherein the first organic ligand and/or the second organic ligand is polar.
13. The method of claim 1 , wherein the first organic ligand and/or second organic ligand is covalently attached to the oxidizable core.
14. The method of claim 1 , further comprising purifying the particles after the step of crushing.