Nano-porous corundum ceramics and methods of manufacture

Patent metadata

Field	Value
Publication number	US-2016060179-A1
Application number	US-201414470243-A
Country	US
Kind code	A1
Filing date	Aug 27, 2014
Priority date	Aug 27, 2014
Publication date	Mar 3, 2016
Grant date	—

Abstract

Nano-porous corundum ceramics and methods of manufacture are disclosed. The method of forming nano-porous corundum ceramics includes milling corundum powder in aqueous slurry with beads. The method further includes processing the slurry by a liquid shaping process to form a gelled body. The method further includes sintering the gelled body between 600° C. to 1000° C.

First claim

What is claimed is:

1 . A method of forming nano-porous corundum ceramics, comprising:
milling corundum powder in an aqueous slurry with beads; processing the slurry by a liquid shaping process to form a gelled body; and sintering the gelled body between 600° C. to 1000° C.

2 . The method of claim 1 , wherein the corundum powder has a BET of 14-24 m 2 /g.

3 . The method of claim 2 , wherein the corundum powder has a BET of 17-21 m 2 /g.

4 . The method of claim 1 , wherein the beads are dense sintered corundum beads with sub-μm grain size.

5 . The method of claim 1 , wherein the beads are one of corundum beads and ZrO 2 beads with 3 mol % Y 2 O 3 .

6 . The method of claim 5 , wherein the slurry is aqueous slurry comprising distilled water and a stabilizing agent for corundum powder particles.

7 . The method of claim 6 , further comprising adding a gelling agent after milling.

8 . The method of claim 1 , wherein the sintering has a final temperature of about 800° C. for a hold time between about 0 hours and 8 hours.

9 . The method of claim 8 , wherein the sintering of the gelled body is in air, oxygen or mixtures of inert gasses with oxygen.

10 . The method of claim 8 , wherein the corundum powder has a purity of >99.9% and the beads are corundum milling beads with purity >99.9%.

11 . The method of claim 10 , wherein the corundum powder has a purity of 99.995% and the beads are corundum milling beads with purity >99.95%.

12 . The method of claim 1 , wherein the liquid shaping process comprises an ultrasonic bath, furnace with degassing process and a molding process and further comprises:
placing slurry molds in a vacuum furnace at about 20-25° C. with vacuuming air inside until it reaches a vacuum at least 50 mbar above a boiling point of the slurry; inserting nitrogen gas into the vacuum furnace until it reaches atmospheric pressure; vacuuming the nitrogen gas until it reaches a vacuum at least 50 mbar above the boiling point of the slurry; repeating for two times the inserting nitrogen gas and vacuuming; filling the vacuum furnace again with the nitrogen gas; increasing the temperature to about 40° C. to 80° C. for 0-8 hours; and reducing the temperature to about 20-25° C.

13 . A method comprising:
milling corundum powder with BET of 17-21 m 2 /g in an aqueous slurry with beads, the aqueous slurry being distilled water and HNO 3 for stabilizing a pH of the corundum powder between 3.5 and 4.5; processing the aqueous slurry by a liquid shaping process to form a gelled body; and sintering the gelled body in air at a temperature between 800° C. to 900° C.

14 . The method of claim 13 , wherein the beads are dense sintered corundum beads with sub-μm grain size.

15 . The method of claim 13 , wherein the beads are ZrO 2 beads with 3 mol % Y 2 O 3 .

16 . The method of claim 13 , wherein a sintering aid of MgO or a MgO precursor comprising <0.05 wt % MgO is added to the slurry

17 . The method of claim 13 , wherein the liquid shaping process comprises:
placing slurry molds in a vacuum furnace with vacuuming air inside; inserting nitrogen gas into the vacuum furnace until it reaches a pressure higher than an initial pressure; vacuuming the nitrogen gas; filling the vacuum furnace again with the nitrogen gas; and adjusting the temperature.

18 . The method of claim 13 , wherein the corundum powder has a purity of >99.9% and the beads are corundum milling beads with purity >99.9%.

19 . The method of claim 13 , wherein a final temperature of the sintering is about 800° C. with a hold time of about 2 hours.

20 . A nano-porous ceramic body composed of corundum powder having a thickness between 5 mm and 30 mm, porosity between 35% and 40%, <1% of the pore volume with pore size >45 nm and <1% of the pore volume with pore size <20 nm.

Assignees

• King Abdulaziz City Sci & Tech
• Fraunhofer Ges Forschung

Inventors

• Binhussain Mohammed A
• Alakeel Akeel Khalid
• Binmajid Majid Mohammed
• Klimke Jens

Classifications

• C04B38/0074

  expressed as porosity percentage · CPC title

• C04B38/0054

  the pores being microsized or nanosized · CPC title

• C04B38/0045 Primary

  by a process involving the formation of a sol or a gel, e.g. sol-gel or precipitation processes · CPC title

• C04B35/111 Primary

  Fine ceramics · CPC title

• C04B2235/3206

  Magnesium oxides or oxide-forming salts thereof · CPC title