Production of charged uniformly sized metal droplets

• US 5,266,098 A
• Filed: 01/07/1992
• Issued: 11/30/1993
• Est. Priority Date: 01/07/1992
• Status: Expired due to Term

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Passow, Christian H., Chun, Jung-Hoon
• Primary Examiner(s): WYSZOMIERSKI, GEORGE P
• Application Number:
  US07/817,517
• Time in Patent Office: 693 Days
• Field of Search: 75/331, 75/335-340, 264/10
• US Class Current: 75/335
• CPC Class Codes: B22F 2009/0836 with electric or magnetic field or induction
• CPC Class Codes: B22F 2202/01 Use of vibrations
• CPC Class Codes: B22F 2998/00 Supplementary information concerning processes or compositions relating to powder metallurgy
• CPC Class Codes: B22F 2999/00 Aspects linked to processes or compositions used in powder metallurgy
• CPC Class Codes: B22F 3/115 by spraying molten metal, i.e. spray sintering, spray casting
• CPC Class Codes: B22F 9/08 by casting, e.g. through sieves or in water, by atomising or spraying using electric discharge B22F9/14

Abstract

A process for producing charged uniformly sized metal droplets in which a quantity of metal is placed in a container and liquified, the container having a plurality of orifices to permit passage of the liquified metal therethrough. The liquified metal is vibrated in the container. The vibrating liquified metal is forced through the orifices, the vibration causing the liquified metal to form uniformly sized metal droplets. A charge is placed on the liquified metal either when it is in the container or after the liquified metal exits the container, the charging thereof causing the droplets to maintain their uniform size. The uniformly sized droplets can be used to coat a substrate with the liquified metal.

Claims

1. A process for producing and maintaining charged uniformly sized metal droplets comprising the steps of:

(1) liquefying a quantity of metal disposed in a container having at least one orifice to permit the passage of metal;

(2) vibrating the liquefied metal in said container; and

(3) forcing the vibrating liquefied metal through the at least one orifice;

said method further including a step of placing a positive or negative charge on the liquefied metal, either before or after it exits the at least one orifice, the vibration thereof thereby causing said liquefied metal to form uniformly sized liquid metal droplets, which droplets exhibit a degree of variation of less than about ±

25% from the average droplet diameter, and the charging thereof causing said droplets to maintain their uniform size.

2. The process of claim 1, wherein said vibrating step includes applying at least one oscillating gas jet to the liquified metal as it exits the at least one orifice.

3. The process of claim 1, wherein the liquefied metal is charged after it exits the at least one orifice in the container.

4. The process of claim 3, wherein the placing of a positive or negative charge on the liquefied metal comprises using a charging plate having at least one opening therein aligned with the at least one orifice so as to permit the vibrated liquefied metal exiting the orifice to pass through the charging plate and become charged.

5. The process of claim 4, wherein the liquefied metal is forced through a plurality of orifices forming a plurality of streams of uniformly sized metal droplets and passing the droplets through a plurality of openings in the charge plate thereby forming a plurality of streams of charged uniformly sized metal droplets.

6. The process of claim 3, wherein the uniformly sized droplets have a diameter which is within the range of from about 10 to 500 μ

m and wherein the droplets exhibit a degree of variation of about ±

5% of the average droplet diameter.

7. The process of claim 3, wherein said vibrating step includes applying at least one oscillating gas jet to the liquified metal as it exits the at least one orifice.

8. The process of claim 7, wherein the placing of a positive or negative charge on the liquefied metal comprises using a charging plate having at least one opening therein aligned with the at least one orifice so as to permit the liquefied metal exiting the orifice to pass through the charging plate.

9. The process of claim 7, wherein the uniformly sized droplets have a diameter which is within the range of from about 10 to 500 μ

m and wherein the droplets exhibit a degree of variation of about ±

10% of the average droplet diameter.

10. The process of claim 1, wherein the liquefied metal is charged when it is in the container before it is formed into droplets.

11. The process of claim 10, wherein said vibrating step includes applying at least one oscillating gas jet to the liquified metal as it exits the at least one orifice.

12. The process of claim 10, wherein the uniformly sized droplets have a diameter which is within the range of from about 10 to 500 μ

m and wherein the droplets exhibit a degree of variation of about ±

5% of the average droplet diameter.

13. The process of claim 1, wherein the process further comprises depositing the charged droplets onto a substrate.

14. The process of claim 1, wherein the uniformly sized droplets have a diameter which is within the range of from about 10 to 500 μ

m and wherein the droplets exhibit a degree of variation of about ±

5% of the average droplet diameter.

15. The process of claim 1, wherein the uniformly sized charged metal droplets have an initial velocity of from about 1 to 25 m/sec.

16. The process of claim 1, wherein the uniformly sized metal droplets are charged to about 10^-5 to 10^-8 Coulombs per gram.

17. The process of claim 1, further comprising applying an electric field in a flow path of the metal droplets to change their trajectories.

18. The process of claim 1, further comprising monitoring the charged metal droplets after formation to determine the sizes and the velocities of said liquid metal droplets.

19. The process of claim 1, wherein the process is performed in an inert gas atmosphere.