# US 9,040,440 B2 · Method of toughening alumina

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- Number: US 9,040,440 B2
- Document ID: US9040440B2
- Status: Granted
- Kind: B2
- Application number: 14/173,050
- Filed: 2014-02-05
- Published: 2014-06-05
- Granted: 2015-05-26
- Earliest claimed: 2012-08-24
- Assignees: Superior Technical Ceramics Corporation
- Applicants: Superior Technical Ceramics Corporation
- Inventors: Tariq Quadir; Brian H. Gold
- Web page: https://patentgrep.com/patent/US9040440B2

## CPC

- C04B 35/64: Burning or sintering processes (C04B33/32 takes precedence {; powder metallurgy B22F})
- C04B 35/119: with zirconium oxide
- C04B 2235/3206: Magnesium oxides or oxide-forming salts thereof
- C04B 2235/3225: Yttrium oxide or oxide-forming salts thereof
- C04B 2235/3246: Stabilised zirconias, e.g. YSZ or cerium stabilised zirconia
- C04B 2235/77: Density
- C04B 2235/786: Micrometer sized grains, i.e. from 1 to 100 micron
- C04B 2235/96: Properties of ceramic products, e.g. mechanical properties such as strength, toughness, wear resistance
- C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE

## Abstract

The present application is directed to a zirconia toughened alumina body and process for making the body. The process involves combining tetragonally stabilized ZrO2 nanoparticles, Mg(OH)2 particles and alumina powder into a mixture. All particles of the mixture are milled, formed into a green compact and then sintered. The final composition of the body includes α-Al2O3 toughened with 0.5 to 2.5 weight percent ZrO2 in a stabilized tetragonal form and 0.03 to 0.10 weight percent MgO. The composition results in an Al2O3 body with a density less than 4.0 g/cc and strength greater than 50 kpsi.

## Claims

### Claim 1

A method of fabricating a ceramic, comprising the steps of:
a) providing (i) crystalline α-Al2O3 particles, (ii) 0.5-2.5 percent by weight crystalline ZrO2 particles less than 0.1-microns and stabilized substantially in the tetragonal crystal structure, and (iii) 0.03-0.10 percent MgO by weight as Mg(OH)2 particles;
b) combining and milling all particles;
c) forming a green compact; and
d) sintering said green compact in a temperature range of 1637° C.-1660° C.

### Claim 2 (depends on 1)

A method as recited in claim 1, wherein during said providing step a) said percent by weight crystalline ZrO2 particles is 1.0-2.0.

### Claim 3 (depends on 1)

A method as recited in claim 1, wherein during said providing step a) said percent MgO by weight is 0.03-0.05.

### Claim 4 (depends on 1)

A method as recited in claim 1, wherein during said milling of step b) all particles are milled to have a D50 diameter of less than 1.0-micron.

### Claim 5 (depends on 1)

A method as recited in claim 1, wherein said ceramic has a final actual density of less than 4.0 g/cc.

### Claim 6 (depends on 1)

A method as recited in claim 1, wherein said ceramic has a final strength greater than 50 kpsi.

### Claim 7 (depends on 1)

A method as recited in claim 1, wherein said tetragonal crystal structure of ZrO2 is stabilized with a stabilizing agent that is at least one selected from the group consisting of Y2O3 and CeO2.