Process for preparing nanostructured cerium oxide materials of controlled surface chemistry of zeta potential

• US 7,517,513 B2
• Filed: 06/02/2003
• Issued: 04/14/2009
• Est. Priority Date: 06/17/2002
• Status: Active Grant

• Current Assignee: Nanophase Technologies Corporation
• Original Assignee: Nanophase Technologies Corporation
• Inventors: Piepenbrink, Jonathan, Sarkas, Harry W.
• Primary Examiner(s): BOS, STEVEN J
• Application Number:
  US10/452,736
• Publication Number:
  US 20030230479A1
• Time in Patent Office: 2,143 Days
• Field of Search: 423/263, 977/811
• US Class Current: 423/263
• 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 19/126 Microwaves
• CPC Class Codes: B01J 19/129 Radiofrequency
• CPC Class Codes: B01J 2219/0809 employing two or more electrodes
• CPC Class Codes: B01J 2219/0847 Glow discharge
• CPC Class Codes: B01J 2219/0886 Gas-solid
• CPC Class Codes: B01J 2219/0894 Processes carried out in the presence of a plasma
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C01B 13/145 After-treatment of oxides or hydroxides, e.g. pulverising, drying, decreasing the acidity
• CPC Class Codes: C01F 7/02 Aluminium oxide; Aluminium hydroxide; Aluminates
• CPC Class Codes: C01P 2004/64 Nanometer sized, i.e. from 1-100 nanometer
• CPC Class Codes: C01P 2006/12 Surface area
• CPC Class Codes: C01P 2006/22 Rheological behaviour as dispersion, e.g. viscosity, sedimentation stability
• CPC Class Codes: C01P 2006/90 Other properties not specified above
• CPC Class Codes: C23C 14/0021 Reactive sputtering or evaporation
• CPC Class Codes: C23C 14/32 by explosion; by evaporation and subsequent ionisation of the vapours , e.g. ion-platingC23C14/34 - C23C14/48 take precedence
• CPC Class Codes: C23C 4/123 Spraying molten metal
• CPC Class Codes: C23C 4/134 Plasma spraying
• CPC Class Codes: C23C 8/36 using ionised gases, e.g. ionitriding
• CPC Class Codes: Y10S 977/811 Of specified metal oxide composition, e.g. conducting or semiconducting compositions such as ITO, ZnOx
• CPC Class Codes: Y10S 977/844 : Growth by vaporization or dissociation of carbon source using a high-energy heat source, e.g. electric arc, laser, plasma, e-beam
• CPC Class Codes: Y10S 977/847 : Surface modifications, e.g. functionalization, coating
• CPC Class Codes: Y10S 977/90 : having step or means utilizing mechanical or thermal property, e.g. pressure, heat

Abstract

A process to prepare stoichiometric-nanostructured materials comprising generating a plasma, forming an “active volume” through introduction of an oxidizing gas into the plasma, before the plasma is expanded into a field-free zone, either (1) in a region in close proximity to a zone of charge carrier generation, or (2) in a region of current conduction between field generating elements, including the surface of the field generation elements, and transferring energy from the plasma to a precursor material to form in the “active volume” at least one stoichiometric-nanostructured material and a vapor that may be condensed to form a stoichiometric-nanostructured material. The surface chemistry of the resulting nanostructured materials is substantially enhanced to yield dispersion stable materials with large zeta-potentials.

Claims

1. Stoichiometric-nanostructured material produced through the steps comprising:

generating a plasma;

forming an “

active volume”

through introduction of an oxidizing gas into the plasma, before the plasma is expanded into a field free zone, in a region in close proximity to either (1) a zone of charge carrier generation, or (2) a region of current conduction between field generating elements, including the surface of the field generating electrodes; and

transferring energy from the plasma to a precursor material or materials and forming in the “

active volume”

at least one of stoichiometric-nanostructured material and a vapor that may be condensed to form a stoichiometric-nanostructured material;

wherein

the stoichiometric-nanostructured material is cerium oxide and has a surface chemistry with the value of the zeta potential greater than 20 mV.

2. The stoichiometric-nanostructured material of claim 1, wherein the stoichiometric-nanostructured material is substantially spherical nanocrystalline cerium oxide.

3. The stoichiometric-nanostructured materials of claim 1, wherein the stoichiometric-nanostructured material generally has a size distribution and range in mean diameter from about 1 nm to about 900 nm.

4. The stoichiometric-nanostructured material of claim 3, wherein the stoichiometric-nanostructured material generally has a size distribution and range in mean diameter from about 2 nm to about 100 nm.

5. The stoichiometric-nanostructured material of claim 4, wherein the stoichiometric-nanostructured material generally has a size distribution and range in mean diameter from about 5 nm to about 40 nm.

6. The stoichiometric-nanostructured material of claim 1, wherein the stoichiometric-nanostructured material has a surface chemistry having a high aqueous dispersion stability.

7. The stoichiometric-nanostructured material of claim 1, wherein the stoichiometric-nanostructured material has a surface chemistry having a low rate of hydrolysis.

8. The stoichiometric-nanostructured material of claim 1, wherein the stoichiometric-nanostructured material has a surface chemistry with the value of the zeta potential greater than 30 mV.

9. The stoichiometric-nanostructured materials of claim 8, wherein the stoichiometric-nanostructured material has a surface chemistry with the value of the zeta potential greater than 35 mV.