Patent US4771950A successfully refreshed from Google Patents.
US4771950A
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Hydrothermal comminution or zirconia or hafnia
Assignee: Saint Gobain Abrasives Inc
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Filing: 1987-07-06
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Granted: 1988-09-20
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Expires: 2007-07-06
Abstract
Abstract Zirconia ceramics containing substantial amounts of metastable tetragonal phase crystallites, so that they are tougher than most other ceramics, can be completely comminuted to powders, without applying any mechanical force, by treatment with water or steam at temperatures well above room temperature. This type of comminution is particularly useful for small, often hollow, spheres produced by rapidly solidifying melts of zirconia and a stabilizing oxide such as yttria. These spheres can be almost completely comminuted to a size suitable for wet vibratory milling by treatment for twenty-four hours at 250 C under sufficient steam pressure to maintain some liquid water in equilibrium.
Inventors
- 👤 William S. Coblenz
- 👤 Paul J. Pelletier
- 👤 Guilio A. Rossi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 03:12
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/01; C04B35/48; C04B35/486
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
60 words
A process for the comminution of initially macroscopic objects of metastabilized zirconia, comprising exposing said objects to water at sufficiently high temperature and pressure for a sufficient time to cause said objects to disintegrate spontaneously into particles having weighted average longest dimensions not more than one half as much as the weighted average longest dimensions of said initially macroscopic objects.
Claim 2
Dependent Claim
60 words
A process for the comminution of initially macroscopic objects of metastabilized zirconia, comprising exposing said objects to water at sufficiently high temperature and pressure for a sufficient time to cause said objects to disintegrate spontaneously into particles having weighted average longest dimensions not more than one half as much as the weighted average longest dimensions of said initially macroscopic objects.
Claim 3
Dependent Claim
15 words
A process according to claim 1, wherein said initially macroscopic objects are rapidly solidified crude.
Claim 4
Dependent Claim
20 words
A process according to claim 2, wherein at least 99% of said particles will pass through a 20 mesh screen.
Claim 5
Dependent Claim
36 words
A process according to claim 3, wherein said temperature is at least 250 C., said pressure is at least the equilibrium vapor pressure of water at 250 C., and said time is at least twenty-four hours.
Claim 6
Dependent Claim
20 words
A process according to claim 4, wherein the median particle size of said particles is not more than 100 microns.
Claim 7
Dependent Claim
89 words
A process for recycling a macroscopic object of metastabilized zirconia (MSZ), comprising the steps of: (a) exposing said object to water at sufficiently high temperature and pressure for a sufficient time to cause said object to disintegrate spontaneously into particles having weighted average longest dimensions not more than one half as much as the weighted average longest dimension of said macroscopic object; and (b) densifying by application of pressure and heat at least a portion of the particles obtained in step (a) into a new macroscopic object of MSZ.
Claim 8
Dependent Claim
89 words
A process for recycling a macroscopic object of metastabilized zirconia (MSZ), comprising the steps of: (a) exposing said object to water at sufficiently high temperature and pressure for a sufficient time to cause said object to disintegrate spontaneously into particles having weighted average longest dimensions not more than one half as much as the weighted average longest dimension of said macroscopic object; and (b) densifying by application of pressure and heat at least a portion of the particles obtained in step (a) into a new macroscopic object of MSZ.
Claim 9
Dependent Claim
22 words
A process according to claim 6, additionally comprising a step of comminuting by wet vibratory milling the particles obtained in step (a).
Claim 10
Dependent Claim
29 words
A process according to claim 6, wherein said objects have an actual density of at least 95% of the theoretical maximum density for their chemical composition and crystal structure.
Claim 11
Dependent Claim
22 words
A process according to claim 8, additionally comprising a step of comminuting by wet vibratory milling the particles obtained in step (a).
Claim 12
Dependent Claim
31 words
A process according to claim 8, wherein said exposing comprises exposure for at least twenty-four hours at 250 C. to at least the equilibrium vapor pressure of water at 250 C.
Claim 13
Dependent Claim
22 words
A process according to claim 10, additionally comprising a step of comminuting by wet vibratory milling the particles obtained in step (a).
Claim 14
Dependent Claim
31 words
A process according to claim 8, wherein said exposing comprises exposure for at least twenty-four hours at 200 C. to at least the equilibrium vapor pressure of water at 200 C.
Claim 15
Dependent Claim
53 words
A process according to claim 12, wherein said exposing additionally comprises exposure for at least twenty-four hours at 250 C. to at least the equilibrium water vapor pressure at 250 C. after said exposure for at least twenty-four hours at 200 C. to at least the equilibrium water vapor pressure at 200 C.
Claim 16
Dependent Claim
22 words
A process according to claim 13, additionally comprising a step of comminuting by wet vibratory milling the particles obtained in step (a).
Claim 17
Dependent Claim
22 words
A process according to claim 12, additionally comprising a step of comminuting by wet vibratory milling the particles obtained in step (a).
References Cited (Backward Citations)
US4565792A
Cited
US4501818A
Cited
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