Microwave plasma chemical synthesis of ultrafine powders

• US 6,409,851 B1
• Filed: 03/05/1999
• Issued: 06/25/2002
• Est. Priority Date: 11/04/1996
• Status: Expired due to Term

• Current Assignee: Materials Modification Inc.
• Original Assignee: Materials Modification Inc.
• Inventors: Kalyanaraman, Raja, Sethuram, Krupashankara M.
• Primary Examiner(s): WYSZOMIERSKI, GEORGE P
• Application Number:
  US09/262,848
• Time in Patent Office: 1,208 Days
• Field of Search: 148/565, 219/121.43, 219/121.59, 423/289, 118/723.MW
• 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 positioned such that a plasma is capable of heating 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 inches 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 positioned such that a plasma is capable of heating 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.

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.

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 a reactant chemical vapor.