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Ceramic particulate material and processes for forming same

a technology of applied in the field of drawing to ceramic particulate material and process for forming same, can solve the problems of confined thermal budget, and limited particle morphologies and characteristics enabled by such approaches

Inactive Publication Date: 2008-07-24
SAINT GOBAIN CERAMICS & PLASTICS INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The patent describes a ceramic particulate material with specific properties, such as a specific surface area and sphericity. The material can be formed by heat treatment of a loose powder or by combining alumina precursors with seeds and converting them into alpha-alumina particles. The resulting material has improved properties, such as better mechanical strength and improved performance in high-temperature applications. The technical effects of this patent are the improved properties of ceramic particulate materials and the methods for their formation.

Problems solved by technology

Often times, it is desired that the ceramic bodies are sinterable to a desired density under a confined thermal budget, including limitations on maximum sintering temperature and dwell times. Limitations on the thermal budget may be placed on processing due to temperature limitations on other components in case of a composite, and due to processing costs, for example.
However, the morphologies and powder characteristics enabled by such approaches are somewhat confined.
Such approaches have been successful in the formation of alpha-alumina particulate material for a wide range of applications, but also have limited particle morphologies and characteristics.

Method used

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  • Ceramic particulate material and processes for forming same
  • Ceramic particulate material and processes for forming same
  • Ceramic particulate material and processes for forming same

Examples

Experimental program
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Effect test

example 1

[0047]Example 1 illustrates the effect of temperature and pressure on conversion of seeded aluminous feedstock in the form of boehmite. Example 1 begins with the formation of an alumina sol prepared by mixing 100 grams of Disperal boehmite from Sasol Corporation into 700 ml of water with 5% alpha-alumina seeds, having a crystal size of 0.02 microns, generated by horizontal bead milling of 0.5 micron alpha-alumina and 3% of nitric acid relative to boehmite. The sample was then placed into a drying oven at 80° C. overnight. Drum drying into flakes may alternatively be utilized. The dried material was calcined into a box furnace at 500° C. for two hours, to form transition phase alumina, forming an open structure, that is, a loose particulate material having limited inter particle necking. The material was then subjected to HIPing treatment to obtain alpha-alumina powder. Table 1 below shows the effect of temperature and pressure combinations on the phase transformation of the loose po...

example 2

[0049]Further characterization studies on powder particulate sphericity were also carried out. As noted above, sphericity may be characterized in terms of concavity; concavity being the percent of particles based upon a sample of at least 100 particles, which have a concave outer peripheral portion that extends along a distance not less than 10% of d50 of the particulate material by TEM inspection, the concave outer peripheral portion having a negative radius of curvature as viewed from an interior of the particle. In this respect, a state of the art nanosized alpha-alumina powder is depicted in FIGS. 6-11 from Taimicron. Those particles marked represent particles that have the requisite concavity to be considered a concave particle. Based upon the sample analysis depicted in FIGS. 6-11, the Taimicron powder was found to have a concavity of 39.2%. A second state of the art powder from Sumitomo (commercially available as AKP700) is shown in TEM images corresponding to FIGS. 12-15. Th...

example 3

[0051]Example 3 illustrates the effect of seeding on the minimum transformation temperature required to transform seeded boehmite to alpha-alumina. A first alumina gel was prepared by mixing 100 grams of Disperal boehmite (d50=0.08 microns) into 700 ml of water and 3% of nitric acid relative to boehmite. A second gel was prepared with the same proportion but using a finer boehmite designated P2 (d50=0.05 microns). The seeding levels (wt %) as a function of peak temperature (° C.) required to convert the seeded boehmite into the alpha phase is shown in FIG. 26, where alpha transformation was determined using DTA analysis. FIG. 26 shows that the finer dispersion corresponding to the P2 alpha-alumina precursor achieves a transformation from boehmite to alpha-alumina at comparatively lower temperatures than that of the sample containing Disperal.

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Abstract

Ceramic particulate material includes alumina particles, the particles having a specific surface area (SSA) not less than 15 m2 / g and not greater than 75 m2 / g and a sphericity quantified by at least one of (i) a mean roundness not less than 0.710 as measured by Roundness Correlation Image Analysis, and (ii) a concavity less than 20%, wherein concavity is the percent of alumina particles based on a sample of at least 100 particles, which have a concave outer peripheral portion that extends along a distance not less than 10% of d50 by TEM inspection, the concave outer peripheral portion having a negative radius of curvature as viewed from an interior of the particle

Description

CROSS-REFERENCE TO RELATED APPLICATION(S)[0001]The present application claims priority from U.S. Provisional Patent Application No. 60 / 884,925, filed Jan. 15, 2007, entitled “CERAMIC PARTICULATE MATERIAL AND PROCESSES FOR FORMING SAME”, naming inventors Ralph Bauer, Doruk Yener, and Claire Theron, which application is incorporated by reference herein in its entirety.BACKGROUND[0002]1. Field of the Disclosure[0003]The present invention is generally drawn to ceramic particulate material and processes for forming same. In particular, aspects of the present invention are drawn to alumina ceramic particulate material.[0004]2. Description of the Related Art[0005]Aluminous particulate material, including hydrated aluminas, transition-phase aluminas, and the high temperature phase of alumina, alpha-alumina, have been commonly used in various industrial applications, including use as fillers, raw materials for ceramic bodies and abrasives, among many others. Certain industries, including the...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): B32B5/16B28B3/00C01F7/02C01F7/021C01F7/442
CPCB82Y30/00C01F7/02C01F7/021C01F7/442C01P2004/04C01P2004/32Y10T428/2982C01P2004/64C01P2006/12C01P2006/36C09G1/02C09K3/1409C01P2004/62
Inventor BAUER, RALPHHAERLE, ANDREW G.YENER, DORUK O.THERON, CLAIRE M.KAVANAUGH, MICHAEL D.
Owner SAINT GOBAIN CERAMICS & PLASTICS INC
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