Process of making &agr;-alumina powder

Details Process of making &agr;-alumina powder Process of making &agr;-alumina powder

2000-08-11

2002-10-08

Bos, Steven (Department: 1754)

Chemistry of inorganic compounds

Oxygen or compound thereof

Metal containing

C423S626000

Reexamination Certificate

active

06461584

ABSTRACT:

FIELD OF THE INVENTION
&agr;-Alumina powder having a particle size of less than 60 nanometers is produced from hydrated alumina.
BACKGROUND
Alumina powders are used as polishing material in the manufacture of oxidized ceramics and silicone chips. The particle size of such powders has been decreasing from micrometer level to submicrometer level, and, lately, to nanometer level. At the nanometer level, as the interval between crystallites is reduced, the quantum dispersion during calcining is tighter. In addressing the issue, T. G. Langdon,
Ceramic. Inter
., Vol. 19, 279-286, 1993, indicated the temperature required for enhancing calcination rate and reducing sintering, which eventually expanded the scope of application to ceramics. Despite this, in manufacturing nanometer &agr;-alumina, chemical co-precipitated alumina powder invariably sinters together in the calcination stage, making it impossible to obtain even finer superfine &agr;-alumina.
PRIOR ART
Taiwan patents related to manufacturing superfine &agr;-alumina powder are indexed under APIPA, including: U.S. Pat. No. 246,668, Submicrometer boehmite gel liquid; U.S. Pat. No. 175,369, Manufacturing process of &agr;-Alumina from Alumina gel; and U.S. Pat. No. 4,169,883, Process for Preparing Ultra-stable High Surface Area Alpha-Alumina. In the most prevalent practice of using a chemical solvent to produce &agr;-alumina, boehmite is the most common precursor. During heat treatment final stability is achieved through phase conversion. In recent years superfine polishing powders used for integrated circuits are primarily &agr;-alumina. The need for even finer micro-particle polishing abrasives is due to the micro-development of products. For &agr;-alumina as polishing material, the requirement is even finer than present production capability. This means that manufacturing nanometer grade abrasives is a key technology in the micro-development of integrated circuits.
SUMMARY OF THE INVENTION
High-sheer mixing boehmite with surfactant forms a micro-micelle, which is calcined at about 1,050° C. for approximately 30 minutes to produce &agr;-alumina. The product is a black net-like fragile substance, residual carbon of which is burnt off after cooling to a temperature between 800° C. and room temperature. After deagglomeration treatment and centrifugal settling in a suitable liquid, &agr;-alumina having a particle size of less than 60 nm is obtained.


REFERENCES:
patent: 4169883 (1979-10-01), Murrell et al.
patent: 5417956 (1995-05-01), Moser
patent: 175369 (1991-12-01), None
patent: 246668 (1995-05-01), None
Langdon, Ceramics Intn'l, vol. 19, “Superplastic-like Flow in Ceramics: Recent Developments . . .”, pp. 279-286, 1993, No month.
Hart, Editor, Alumina Chemicals Science and Technology Handbook, “History of Alumina Chemicals”, pp. 1-6, No date.
Zhou et al, Acta Cryst., B47, “Structures and Transformation Mechanisms of the . . . ”, pp. 617-630, 1991, No month.
Maher et al, Amer. Ceramic Society Bulletin, “Preparation and Characterization of Ceramic Fine . . . ”, pp. 72-76, May, 1993.
Maher et al, Jour of Materials Proc Tech, vol. 56, “Preparation and Characterization of Ceramic . . . ”, pp. 200-210, 1996, No month.
Napper, Polymeric Stabilization of Colloidal Dispersions, “Basic Concepts of Stability”, pp. 8-16, 1983, No month.
Wefers, Technical Paper, “Nonmenclature, Preparation, and Properties of Aluminum Oxides . . . ”, pp. 13-22, 1972, No month.

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