# US 11,299,428 B2 · High strength ceramics with novel fracture mode

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 11,299,428 B2
- Document ID: US11299428B2
- Status: Granted
- Kind: B2
- Application number: 15/498,709
- Filed: 2017-04-27
- Published: 2017-11-02
- Granted: 2022-04-12
- Earliest claimed: 2016-04-27
- Assignees: The Government of the United States of America, as represented by the Secretary of the Navy
- Applicants: The Government of the United States of America, as represented by the Secretary of the Navy
- Inventors: Michael Hunt; Guillermo R. Villalobos; Benjamin Rock; Shyam S. Bayya; Woohong Kim; Ishwar D. Aggarwal; Bryan Sadowski; Jasbinder S. Sanghera
- Web page: https://patentgrep.com/patent/US11299428B2

## CPC

- C04B 35/505: based on yttrium oxide
- C04B 35/443: Magnesium aluminate spinel
- C04B 35/4682: {based on BaTiO3 perovskite phase}
- C04B 35/50: based on rare-earth compounds {(non-oxide rare earth compounds C04B35/5156)}
- C04B 35/638: Removal thereof
- C04B 35/64: Burning or sintering processes (C04B33/32 takes precedence {; powder metallurgy B22F})
- C04B 2235/3208: Calcium oxide or oxide-forming salts thereof, e.g. lime
- C04B 2235/3215: Barium oxides or oxide-forming salts thereof
- C04B 2235/3222: Aluminates other than alumino-silicates, e.g. spinel (MgAl2O4)
- C04B 2235/3224: Rare earth oxide or oxide forming salts thereof, e.g. scandium oxide
- C04B 2235/3225: Yttrium oxide or oxide-forming salts thereof
- C04B 2235/3236: Alkaline earth titanates
- C04B 2235/5409: expressed by specific surface values
- C04B 2235/5445: submicron sized, i.e. from 0,1 to 1 micron
- C04B 2235/6025: Tape casting, e.g. with a doctor blade
- C04B 2235/6027: Slip casting
- C04B 2235/604: Pressing at temperatures other than sintering temperatures
- C04B 2235/608: Green bodies or pre-forms with well-defined density
- C04B 2235/6562: Heating rate
- C04B 2235/6567: Treatment time
- C04B 2235/667: Sintering using wave energy, e.g. microwave sintering
- C04B 2235/77: Density
- C04B 2235/786: Micrometer sized grains, i.e. from 1 to 100 micron
- 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 invention provides a method for making a high strength, small grain size ceramic having a trans-granular fracture mode by rapid densification of a green body and subsequent cooling of the densified ceramic. The ceramic may include dislocations, defects, dopants, and/or secondary phases that are formed as a result of the process and resulting in stress fields capable of redirecting or arresting cracks within the material. This ceramic can maintain transparency from ultraviolet to mid-wave infrared.

## Claims

### Claim 1

A method for making a ceramic having transgranular fracture behavior, comprising:
forming a green body comprising a ceramic powder;
densifying the green body using microwaves to heat the green body at a rate of 100° C./min to 1450° C. and then holding at 1450° C. for 15 minutes, wherein a ceramic is formed, wherein there are dislocations within the ceramic, and wherein the microwave frequency is greater than 30 GHz; and
cooling the ceramic to room temperature to trap the dislocations in the ceramic, resulting in a ceramic having a transgranular fracture mode.

### Claim 2 (depends on 1)

The method of claim 1, wherein said ceramic powder comprises magnesium aluminate spinel.

### Claim 3 (depends on 1)

The method of claim 1, wherein said green body is formed by cold isostatic pressure, slip casting, tape casting, or any combination thereof.

### Claim 4 (depends on 1)

The method of claim 1, wherein said green body is densified using a cavity designed to produce uniform heating throughout said green body.

### Claim 5 (depends on 1)

The method of claim 1, wherein the microwaves are used without the use of a susceptor or indirect heating.

### Claim 6 (depends on 1)

The method of claim 1, wherein said ceramic powder is doped with calcium prior to green body formation.