Microwave plasma chemical synthesis of ultrafine powders

• US 20020112794A1
• Filed: 04/04/2002
• Published: 08/22/2002
• Est. Priority Date: 11/04/1996
• Status: Abandoned Application

• Current Assignee: Materials Modification Inc.
• Original Assignee: Materials Modification Inc.
• Inventors: Kalyanaraman, Raja, Sethuram, Krupashankara M.
• Application Number:
  US10/114,993
• Publication Number:
  US 20020112794A1
• Time in Patent Office: Days
• US Class Current: 148/565
• CPC Class Codes: B01J 19/126 Microwaves
• CPC Class Codes: B01J 2219/00094 Jackets
• CPC Class Codes: B01J 2219/0883 Gas-gas
• CPC Class Codes: B01J 2219/0894 Processes carried out in the presence of a plasma
• CPC Class Codes: B01J 2219/1227 Reactors comprising tubes with open ends
• CPC Class Codes: B01J 2219/1269 Microwave guides
• CPC Class Codes: B22F 1/054 Nanosized particles
• CPC Class Codes: B22F 2202/13 Use of plasma
• CPC Class Codes: B22F 2999/00 Aspects linked to processes or compositions used in powder metallurgy
• CPC Class Codes: B22F 3/105 by using electric current other than for infrared radiant energy, laser radiation or plasma B22F3/11 takes precedence; by ultrasonic bonding B22F3/115 takes precedence
• CPC Class Codes: B22F 9/305 of metal carbonyls
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C01B 13/28 using a plasma or an electric discharge
• CPC Class Codes: C01B 21/06 Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boronazides C01B21/08
• CPC Class Codes: C01B 21/0724 using a plasma
• CPC Class Codes: C01B 32/90 Carbides
• CPC Class Codes: C01G 23/07 Producing by vapour phase processes, e.g. halide oxidation
• CPC Class Codes: C01P 2004/50 Agglomerated particles
• CPC Class Codes: C01P 2004/51 Particles with a specific particle size distribution
• CPC Class Codes: C01P 2004/62 Submicrometer sized, i.e. from 0.1-1 micrometer
• CPC Class Codes: C01P 2004/64 : Nanometer sized, i.e. from 1-100 nanometer
• CPC Class Codes: H01J 2237/339 : Synthesising components
• CPC Class Codes: H01J 37/32192 : Microwave generated discharge H01J37/32357, H01J37/32366, H01J37/32394, H01J37/32403 take precedence
• CPC Class Codes: H01J 37/3244 : Gas supply means
• CPC Class Codes: H05B 6/70 : Feed lines
• CPC Class Codes: H05B 6/806 : for laboratory use
• CPC Class Codes: H05H 1/46 : using applied electromagnetic fields, e.g. high frequency or microwave energy H05H1/26 takes precedence
• CPC Class Codes: H05H 1/463 : using antennas or applicators

Abstract

The present invention relates to the production of ultrafine powders using a microwave plasma apparatus and chemical synthesis technique. Microwaves generated by a magnetron (1) are passed through waveguides (2) before they arrive at the head of a plasmatron (3). These high energy microwaves ionize a plasma gas, thus releasing large amounts of energy. The energy thus released is utilized to initiate and sustain chemical reactions between the desired elements being pumped in a spiral pattern into the plasmatron (3). The reaction products are quenched rapidly in a reactor column (4) into ultrafine powders.

Claims

1. An apparatus for the microwave synthesis of materials, comprising:

a microwave generator;

a waveguide through which a microwave generated by said microwave generator passes into a plasma zone in which a plasma heats reactants to form reaction products;

a plasma gas inlet offset at an angle so that plasma gas passing through the inlet enters the plasma zone in a spiral-shaped pattern; and

a reaction products collector downstream from said plasma zone for collecting the reaction products.

2. The apparatus of claim 1, wherein said plasma zone comprises a microwave damper at a side of the plasma zone away from the waveguide for damping microwaves that have passed through the plasma zone to thereby reduce the power of a reflected microwave by at least 60%.

3. The apparatus of claim 2, wherein the microwave damper is a water cooled glass tube.

4. The apparatus of claim 2, wherein the microwave damper is a water cooled metal tube.

5. The apparatus of claim 2, wherein the microwave damper is a water cooled rectangular tube.

6. The apparatus of claim 1, comprising a column located between the plasma zone and the reaction products collector for cooling the reaction products leaving the plasma zone.

7. The apparatus of claim 6, wherein the column is 8-12″

long.

8. The apparatus of claim 1, comprising a plurality of plasma gas inlets.

9. The apparatus of claim 1, wherein the plasma gas inlet is offset at an angle between 5-30°

.

10. The apparatus of claim 1, wherein the plasma gas inlet is offset at 15°

.

11. An apparatus for the microwave synthesis of materials, comprising:

a microwave generator;

a waveguide through which a microwave generated by said microwave generator passes into a plasma zone in which a plasma heats reactants to form reaction products;

a microwave damper at a side of the plasma zone away from the waveguide for damping microwaves that have passed through the plasma zone to thereby reduce the power of a reflected microwave by at least 60%; and

a reaction products collector downstream from said plasma zone for collecting the reaction products.

13. The method of claim 12, further comprising:

introducing the plasma gas into the microwave applicator in a spiral shaped pattern.

14. The method of claim 12, further comprising:

introducing the plasma gas into the microwave applicator at an oblique angle to thereby produce a spiral shaped pattern.

15. The method of claim 12, wherein at least one reactant is a powder material.

16. The method of claim 13, wherein at least one reactant is chemical vapor.

18. The aggregate of powders of claim 17, wherein the particles are metal particles.

19. The aggregate of powders of claim 17, wherein the particles are ceramic particles.

20. The aggregate of powders of claim 19, wherein the ceramic particles are selected from the group consisting of oxides, carbides and nitrides.

12. A method for the microwave synthesis of materials, said method comprising:

introducing a plasma gas into a microwave applicator;

introducing at least one reactant into the microwave applicator;

generating a microwave in a microwave generator;

directing the microwave into the microwave applicator containing the plasma gas to create a heated plasma in a plasma zone;

absorbing the microwave to reduce the microwave reflection off of a surface of the microwave applicator by at least 60%; and

causing a reaction in the plasma zone thereby converting the at least one reactant into a reaction product.

17. An aggregate of powders consisting essentially of particles having an average particle size less than 1 micron, and a particle size distribution of less than 50 nm.