High strength ceramics with novel fracture mode

Patent metadata

Field	Value
Publication number	US-11299428-B2
Application number	US-201715498709-A
Country	US
Kind code	B2
Filing date	Apr 27, 2017
Priority date	Apr 27, 2016
Publication date	Apr 12, 2022
Grant date	Apr 12, 2022

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.

First claim

What is claimed as new and desired to be protected by Letters Patent of the United States is:

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.

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

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

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

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

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

Assignees

• Us Gov Sec Navy

Inventors

• Hunt Michael
• Villalobos Guillermo R
• Rock Benjamin
• Bayya Shyam S
• Kim Woohong
• Aggarwal Ishwar D
• Sadowski Bryan
• Sanghera Jasbinder S

Classifications

• C04B2235/77

  Density · CPC title

• C04B2235/6025

  Tape casting, e.g. with a doctor blade · CPC title

• C04B35/638

  Removal thereof · CPC title

• C04B2235/3224

  Rare earth oxide or oxide forming salts thereof, e.g. scandium oxide · CPC title

• C04B2235/667

  Sintering using wave energy, e.g. microwave sintering · CPC title