Integrated thermal process for the continuous synthesis of nanoscale powders

• US 5,851,507 A
• Filed: 09/03/1996
• Issued: 12/22/1998
• Est. Priority Date: 09/03/1996
• Status: Expired due to Term

• Current Assignee: PPG Industries Ohio Incorporated (Nouryon BV)
• Original Assignee: Nanomaterials Research Corp.
• Inventors: Pirzada, Shahid, Yadav, Tapesh
• Primary Examiner(s): LANGEL, WAYNE A
• Application Number:
  US08/706,819
• Time in Patent Office: 840 Days
• Field of Search: 423/412, 423/592, 423/409, 423/439, 423/440, 423/659, 423/606, 423/345, 423/289, 75/343, 75/351
• US Class Current: 423/659
• CPC Class Codes: B01J 12/005 carried out at high temperatures, e.g. by pyrolysis
• CPC Class Codes: B01J 12/02 for obtaining at least one reaction product which, at normal temperature, is in the solid state
• CPC Class Codes: B01J 19/088 giving rise to electric discharges for heating purposes H05B7/00; for the production of ozone C01B13/11, H01T19/00
• CPC Class Codes: B01J 19/24 Stationary reactors without moving elements inside B01J19/08, B01J19/26 take precedence; with stationary particles B01J8/02
• CPC Class Codes: B01J 2219/00094 Jackets
• CPC Class Codes: B01J 2219/00135 Electric resistance heaters
• CPC Class Codes: B01J 2219/00155 using insulating materials or refractories
• CPC Class Codes: B01J 2219/00177 controlling the pH
• CPC Class Codes: B01J 2219/0018 controlling the conductivity
• CPC Class Codes: B01J 2219/0894 Processes carried out in the presence of a plasma
• 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 9/12 starting from gaseous material
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: B82Y 5/00 Nanobiotechnology or nanomedicine, e.g. protein engineering or drug delivery
• CPC Class Codes: C01B 13/145 After-treatment of oxides or hydroxides, e.g. pulverising, drying, decreasing the acidity
• CPC Class Codes: C01B 19/007 Tellurides or selenides of metals C01B19/002 takes precedence
• CPC Class Codes: C01B 21/062 with chromium, molybdenum or tungsten
• CPC Class Codes: C01B 32/956 Silicon carbide
• CPC Class Codes: C01B 35/04 : Metal borides
• CPC Class Codes: C01F 11/06 : of carbonates
• CPC Class Codes: C01F 17/235 : Cerium oxides or hydroxides
• CPC Class Codes: C01F 5/06 : by thermal decomposition of magnesium compounds calcining magnesite or dolomite C04B2/10
• CPC Class Codes: C01G 23/006 : Alkaline earth titanates
• CPC Class Codes: C01G 41/02 : Oxides; Hydroxides
• CPC Class Codes: C01G 53/006 : Compounds containing, besides nickel, two or more other elements, with the exception of oxygen or hydrogen nickelates C01G53/40
• CPC Class Codes: C01P 2002/01 : depicted by a TEM-image
• CPC Class Codes: C01P 2002/34 : perovskite-type (ABO3)
• CPC Class Codes: C01P 2002/72 : by d-values or two theta-values, e.g. as X-ray diagram
• CPC Class Codes: C01P 2004/03 : obtained by SEM
• CPC Class Codes: C01P 2004/04 : obtained by TEM, STEM, STM or AFM
• CPC Class Codes: C01P 2004/38 : cube-like
• CPC Class Codes: C01P 2004/51 : Particles with a specific particle size distribution
• CPC Class Codes: C01P 2004/61 : Micrometer sized, i.e. from 1-100 micrometer
• CPC Class Codes: C01P 2004/64 : Nanometer sized, i.e. from 1-100 nanometer
• CPC Class Codes: C01P 2006/10 : Solid density
• CPC Class Codes: C01P 2006/12 : Surface area
• CPC Class Codes: C01P 2006/40 : Electric properties
• CPC Class Codes: C01P 2006/60 : Optical properties, e.g. expressed in CIELAB-values
• CPC Class Codes: C04B 2/10 : Preheating, burning calcining or cooling decarbonation during burning of cement raw materials C04B7/43; obtaining CaO or MgO otherwise than by thermal decomposition of the corresponding carbonates C01F11/02, C01F5/02
• CPC Class Codes: Y02P 20/129 : Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines

Abstract

A continuous process that produces nanoscale powders from different types of precursor material by evaporating the material and quenching the vaporized phase in a converging-diverging expansion nozzle. The precursor material suspended in a carrier gas is continuously vaporized in a thermal reaction chamber under conditions that favor nucleation of the resulting vapor. Immediately after the initial nucleation stages, the vapor stream is rapidly and uniformly quenched at rates of at least 1,000 K/sec, preferably above 1,000,000 K/sec, to block the continued growth of the nucleated particles and produce a nanosize powder suspension of narrow particle-size distribution. The nanopowder is then harvested by filtration from the quenched vapor stream and the carrier medium is purified, compressed and recycled for mixing with new precursor material in the feed stream.

Claims

1. A process for producing a nanoscale powder from a precursor material comprising the following steps:

evaporating the precursor material in a gaseous atmosphere in a thermal reactor so as to create a vapor/gas mixture with a temperature of at least 3000K;

initiating nucleation of the precursor material from the vapor/gas mixture prior to quenching in a zone adjacent to the thermal reactor; and

quenching said vapor/gas mixture by effecting its expansion through a predetermined pressure drop, thereby causing the formation of nanoscale particles of product material in a product gas.

2. The process of claim 1, wherein said pressure drop in the quenching step is sufficient to cause a temperature of the vapor/gas mixture to change at a rate of at least 1,000°

C. per second.

3. The process of claim 1, wherein said pressure drop in the quenching step is sufficient to cause a temperature of the vapor/gas mixture to change at a rate of at least 1,000,000°

C. per second.

4. The process of claim 1, wherein said expansion through a predetermined pressure drop is carried out by passing the vapor/gas mixture through a converging-diverging expansion nozzle.

5. The process of claim 4, wherein said pressure drop through the converging-diverging expansion nozzle is sufficient to cause a temperature of the vapor/gas mixture to change at a rate of at least 1,000°

C. per second.

6. The process of claim 4, wherein said pressure drop through the converging-diverging expansion nozzle is sufficient to cause a temperature of the vapor/gas mixture to change at a rate of at least 1,000,000°

C. per second.

7. The process of claim 4, wherein said pressure drop is between 50 and 650 Torr.

8. The process of claim 1, wherein said evaporation and quenching steps are carried out on a continuous basis.

9. The process of claim 8, wherein said evaporation step is carried out by feeding said precursor material to the thermal reactor as a suspension in said gaseous atmosphere and by subjecting the suspension to an input of thermal energy.

10. The process of claim 9, wherein said thermal energy is at least partially produced by an inductive source.

11. The process of claim 9, wherein said thermal energy is at least partially produced by a microwave source.

12. The process of claim 9, wherein said thermal energy is at least partially produced by an electric arc.

13. The process of claim 9, wherein said thermal energy is at least partially produced by heat of reaction.

14. The process of claim 4, further comprising the step of providing a gaseous boundary-layer stream to form a blanket over an internal surface of the nozzle.

15. The process of claim 1, further comprising the step of coating an internal surface of said thermal reactor with a layer of said precursor material.

16. The process of claim 15, wherein said expansion through a predetermined pressure drop is carried out by passing the vapor/gas mixture through a converging-diverging expansion nozzle.

17. The process of claim 16, wherein said pressure drop through the converging-diverging expansion nozzle is sufficient to cause a temperature of the vapor/gas mixture to change at a rate of at least 1,000°

C. per second.

18. The process of claim 15, further comprising the step of providing a gaseous boundary-layer stream to form a blanket over an internal surface of the nozzle.

19. The process of claim 1, further comprising the step of separating said nanoscale particles of product material from said product gas.

20. The process of claim 19, further comprising the step of recycling said product gas by feeding the product gas to the thermal reactor with said precursor material.

21. A process for producing a nanoscale powder from a precursor material comprising the following steps:

reacting the precursor material with a reactive component in a thermal reactor so as to create a vapor/gas mixture with a temperature of at least 3000K;

initiating nucleation of the precursor material from the vapor/gas mixture prior to quenching in a zone adjacent to the thermal reactor and;

quenching said vapor/gas mixture by effecting its expansion through a predetermined pressure drop, thereby causing formation of nanoscale particles of a product material in a product gas.

22. The process of claim 21, wherein said expansion through a predetermined pressure drop is carried out by passing the vapor/gas mixture through a converging-diverging expansion nozzle.

23. The process of claim 22, wherein said pressure drop through the converging-diverging expansion nozzle is sufficient to cause a temperature of the vapor/gas mixture to change at a rate of at least 1,000°

C. per second.

24. The process of claim 21, wherein said evaporation and quenching steps are carried out on a continuous basis.

25. The process of claim 22, further comprising the step of providing a gaseous boundary-layer stream to form a blanket over an internal surface of the nozzle.