Method of producing nanoscale powders by quenching of vapors

• US 5,788,738 A
• Filed: 09/03/1996
• Issued: 08/04/1998
• 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): WYSZOMIERSKI, GEORGE P
• Application Number:
  US08/707,341
• Time in Patent Office: 700 Days
• Field of Search: 75/331, 75/338, 75/345, 164/46, 164/463, 239/8, 264/12
• US Class Current: 75/331
• 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 2219/00177 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 2002/02 : Amorphous compounds
• CPC Class Codes: C01P 2002/34 : perovskite-type (ABO3)
• CPC Class Codes: C01P 2002/60 : Compounds characterised by their crystallite size
• 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 2004/54 : Particles characterised by their aspect ratio, i.e. the ratio of sizes in the longest to the shortest dimension
• CPC Class Codes: C01P 2004/61 : Micrometer sized, i.e. from 1-100 micrometer
• 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: 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

Abstract

A thermal reactor system that produces nanoscale powders by ultra-rapid thermal quench processing of high-temperature vapors through a boundary-layer converging-diverging nozzle. A gas suspension of precursor material is continuously fed to a thermal reaction chamber and vaporized under conditions that minimize superheating and favor nucleation of the resulting vapor. According to one aspect of the invention, the high temperature vapor is quenched using the principle of Joule-Thompson adiabatic expansion. Immediately after the initial nucleation stages, the vapor stream is passed through the nozzle and rapidly quenched through expansion at rates of at least 1,000° C. per second, preferably greater than 1,000,000° C. per second, to block the continued growth of the nucleated particles and produce a nanosize powder suspension of narrow particle-size distribution. According to another aspect of the invention, a gaseous boundary-layer stream is injected to form a blanket over the internal surface of the nozzle to prevent vapor condensation in the throat of the nozzle and its potential failure.

Claims

1. A method of quenching a high-temperature vapor of a precursor material to produce a nanoscale powder thereof, comprising the following steps:

(a) producing a vapor stream of said high-temperature vapor from an inlet zone having an inlet pressure and passing said vapor stream through a convergent means to channel the vapor stream into a flow restriction having a cross-section;

(b) quenching the vapor stream by channeling the vapor stream out of said flow restriction through divergent means to an outlet zone having an outlet pressure which is smaller than said inlet pressure; and

(c) maintaining said inlet and outlet pressures, thereby creating a pressure differential therebetween;

wherein said pressure differential and said cross-section of the flow restriction are adapted to produce a supersonic flow of said vapor stream.

2. The method of claim 1, wherein said pressure differential 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 method of claim 1, further comprising the step of providing a gaseous boundary-layer stream to form a blanket over an internal surface of the convergent means.

4. The method according to claim 1, further comprising the step of cooling the convergent means, the flow restriction, and the divergent means as the vapor stream is passed from the convergent means to the divergent means.

5. The method according to claim 4, wherein the cooling step comprises providing a cooling stream around at least part of the convergent means, the flow restriction, and the divergent means.

6. The method according to claim 1, further comprising the step of collecting nanoscale of substantially the same chemical composition as the precursor material from the quenched vapor stream.

7. The method according to claim 6, wherein the collecting step comprises:

filtering the nanoscale powder from the quenched vapor stream using a filter; and

harvesting the nanoscale powder from the filter.

8. The method according to claim 1, further comprising, before the producing step, the step of creating the high-temperature vapor of the precursor material by (i) combining a feed stream of the precursor material with a feed stream of gas, and (ii) heating the combined feed streams of precursor material and gas to a temperature sufficient to evaporate at least some of the precursor material in the gas.

9. The method according to claim 8, wherein the combined feed streams of precursor material and gas are heated in a thermal reactor;

and

wherein interior walls of the thermal reactor are coated, at least in part, with the precursor material prior to the heating step.

10. The method according to claim 1, wherein the pressure differential is sufficient to quench the vapor stream at a rate of at least 1,000,000°

C. per second.

11. The method according to claim 1, further comprising the step of passing the vapor stream through a nucleation zone prior to passing the vapor stream through the convergent means, the nucleation zone having thermokinetic conditions which favor nucleation of precursor powder from the vapor stream;

wherein the vapor stream is passed from the nucleation zone through the convergent means as soon as nucleation of the vapor stream begins.

12. The method according to claim 11, wherein the thermokinetic conditions include a supersaturation ratio of the precursor in the vapor stream.

13. The method according to claim 11, wherein the thermokinetic conditions determined by calculating a critical cluster size required to initiate nucleation.

16. The method according to claim 1 comprising varying the rate at which the vapor stream is quenched by varying the rate at which the vapor stream expands in the divergent means.

17. The method according to claim 1, wherein the vapor stream expands supersonically in the divergent means thereby quenching the vapor stream and producing a nanoscale powder.

14. The method according to claim 14, wherein the convergent means, the flow restriction, and the divergent means comprise a Joule-Thompson converging-diverging nozzle.

15. The method according to claim 14, wherein the convergent means decreases at a convergent angle continuously from an initial cross-section to the cross-section of the flow restriction;

and

wherein the divergent means has a cross-section that increases at a divergent angle continuously from the cross-section of the flow restriction.