Pressure casting of submicron ceramic particles and methods of ejection

Patent metadata

Field	Value
Publication number	US-2025262798-A1
Application number	US-202519188724-A
Country	US
Kind code	A1
Filing date	Apr 24, 2025
Priority date	May 3, 2019
Publication date	Aug 21, 2025
Grant date	—

Abstract

Methods and apparatus are provided for pressure casting ceramic bodies. Methods and apparatus are provided for rapid ejection of cast ceramic bodies from a mold. A mold is described that has an impermeable cavity surface to provide dry release of the cast body. Ceramic bodies produced by the methods and apparatus have smooth, non-tacky surfaces after ejection from the mold

First claim

What is claimed is:

1 . A method for making a ceramic block, comprising:
a) providing a pressure casting apparatus that comprises a mold having an impermeable cavity surface and a cavity opening that is in direct contact with a porous casting substrate; b) delivering a ceramic slurry into the mold cavity and casting the slurry under pressure, vacuum, or a combination of pressure and vacuum greater than 20 psi, wherein the ceramic slurry comprises yttria stabilized zirconia having a particle size in the range of D(50)=20 nm to 100 nm; c) removing liquid from the slurry under pressure via the porous casting substrate; d) consolidating ceramic particles forming a ceramic green body within the cavity; e) removing the porous casting substrate from the apparatus to expose a mold opening; and f) ejecting the resulting ceramic green body from the mold opening by a dry release process using a pressure, vacuum, or a combination of pressure and vacuum greater than 5 psi that is applied directly to the green body.

2 . The method for making a ceramic block of claim 1 , wherein the slurry is cast under pressure, vacuum, or a combination of pressure and vacuum of between 20 psi and 900 psi.

3 . The method for making a ceramic block of claim 2 , wherein the slurry is cast under pressure, vacuum, or a combination of pressure and vacuum of between 150 psi and 600 psi.

4 . The method for making a ceramic block of claim 1 , wherein the green body has a first side that abuts the porous casting substrate prior to removing the porous casting substrate from the apparatus, and the pneumatic pressure is applied to a side of the green body opposite the first side.

5 . The method for making a ceramic block of claim 1 , wherein the ceramic green body is ejected from the mold opening without recirculating the liquid.

6 . The method for making a ceramic block of claim 1 , wherein the mold cavity comprises a single piece mold.

7 . The method for making a ceramic block of claim 1 , wherein the mold cavity comprises a multiple piece mold.

8 . The method for making a ceramic block of claim 1 , wherein the porous casting substrate has a median pore diameter of less than 3 μm.

9 . The method for making a ceramic block of claim 1 , wherein the porous casting substrate has a median pore diameter of less than 1 μm.

10 . The method for making a ceramic block of claim 1 , wherein the porous casting substrate has a median pore diameter of between 0.1 μm and 0.6 μm.

11 . The method for making a ceramic block of claim 1 , wherein the green body has a moisture content of at least 8 wt % when it is ejected from the mold opening.

12 . The method for making a ceramic block of claim 11 , wherein the green body has a moisture content of at least 10 wt % when it is ejected from the mold opening.

13 . The method for making a ceramic block of claim 12 , wherein the green body has a moisture content of at between 10 wt % and 12 wt % when it is ejected from the mold opening.

14 . The method for making a ceramic block of claim 1 , wherein the difference between the volume of the green body and the volume of the mold cavity is less than 2% when the green body is ejected from the mold cavity.

15 . The method for making a ceramic block of claim 1 , wherein the difference between the volume of the green body and the volume of the mold cavity is less than 0.5% when the green body is ejected from the mold cavity.

16 . The method for making a ceramic block of claim 1 , wherein the porous casting substrate comprises a permeable membrane backed against a supporting structure.

Assignees

• Glidewell James R Dental Ceramics Inc

Inventors

• Gonzalez Hugo
• Balasubramanian Sreeram
• Campbell Mathew David

Classifications

• B28B1/261

  Moulds therefor (absorbent moulds in general B28B7/344) · CPC title

• C04B35/622

  Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products · CPC title

• C04B35/486

  Fine ceramics · CPC title

• C04B2235/3225

  Yttrium oxide or oxide-forming salts thereof · CPC title

• C04B2235/5445

  submicron sized, i.e. from 0,1 to 1 micron · CPC title