USH302H - Ceramics containing dispersants for improved fracture toughness - Google Patents

Ceramics containing dispersants for improved fracture toughness Download PDF

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USH302H
USH302H US06/750,122 US75012285A USH302H US H302 H USH302 H US H302H US 75012285 A US75012285 A US 75012285A US H302 H USH302 H US H302H
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ceramic
ceramic composition
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matrix
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US06/750,122
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Michael V. Nevitt
Anthony T. Aldred
Sai-Kit Chan
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US Department of Energy
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US Department of Energy
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Assigned to UNITED STATES OF AMERICA, AS REPRESENTED BY THE DEPARTMENT OF ENERGY THE reassignment UNITED STATES OF AMERICA, AS REPRESENTED BY THE DEPARTMENT OF ENERGY THE ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: ALDRED, ANTHONY T., CHAN, SAI-KIT, NEVITT, MICHAEL V.
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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/495—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on vanadium, niobium, tantalum, molybdenum or tungsten oxides or solid solutions thereof with other oxides, e.g. vanadates, niobates, tantalates, molybdates or tungstates

Definitions

  • This invention relates to new ceramic compositions with useful properties extending into high temperature ranges of 800° C. and above and more particularly to ceramic compositions containing in dispersed form an additive class which absorbs stress-related energies transmitted in the composition.
  • additives may be characterized as transformation-prone rare-earth niobates, tantalates or mixtures of these with each other and/or mixtures with rare-earth vanadates.
  • the dispersant is incorporated as small particles in a ceramic matrix in order to attenuate or hinder the propagation in the matrix of cracks that arise from stress.
  • Ceramics have been proposed as replacements for metals in a number of important products including those for high temperature use such as turbine blades, cylinder liners and heads for internal combustion engines, connecting rods, and the like. Ceramics have also been used as liners in various industrial processing equipment including equipment for coal gasification.
  • Ceramics in general are composed of hard brittle materials such as Al 2 O 3 , ZrO 2 , MgO and mixtures of oxides such as mullite (Al 2 O 3 and SiO 2 ) As small particles, these materials are mixed with sintering aids and sintered at elevated temperatures to cause the particles to adhere together in the desired shape. Stresses in these materials caused by temperature variations and/or mechanical loads limit the performance of the ceramics. Excessive stresses cause cracks to form and grow across the structural shapes. In some instances, these cracks may travel at or near the speed of sound and are not effectively hindered nor blocked.
  • Some additives have been incorporated into ceramic compositions to reduce the effect of stresses on performance.
  • One of these involves the addition of an alloying ingredient (CaO is typical) to ZrO 2 in order to achieve a structure in which the matrix consisting of the cubic form of ZrO 2 contains as a dispersant fine particles of the tetragonal form of ZrO 2 .
  • Another involves adding ZrO 2 , wholly or partially in the tetragonal form, to Al 2 O 3 or mullite.
  • the principal mechanism believed to be associated with the beneficial effect of both of these additives involves the action of an advancing crack in producing a stress-induced transformation of the tetragonal form of ZrO 2 to the monoclinic form with a resultant volume change.
  • Still another limitation in the use of tetragonal ZrO 2 as a dispersant at lower temperature as well as higher temperature is the need for a complex, difficult-to-control interplay of additive composition thermal treatment and dispersant particle size that is difficult to manipulate in achieving satisfactory level of crack attenuation.
  • higher operating temperatures of 800° C. to 1200° C. are required for ceramics; and/or when additional crack-attenuating functions are sought and/or when better crack-attenuation control is required at any operating temperature: other dispersant additives would be desirable.
  • one object of the invention is an additive system to improve crack attenuation at higher temperatures in ceramics.
  • Another object of the invention is an additive system which acts as an energy absorber through one and preferably more than one mechanism.
  • An additional object of the invention is an additive system which provides a range of additives useful, effective and controllable under different temperature conditions and in different ceramics.
  • a further object of the invention is an additive system combining two or more of the above objects.
  • the invention is directed to a ceramic composition particularly useful at temperatures above about 800° C. and comprising a ceramic matrix and an additive system based on a transformation-prone rare-earth niobate, tantalate or mixtures of these with each other and/or with a rare-earth vanadate.
  • the general formula for these additives is tRMO 4 where R is a rare earth element with an atomic number in the range of 57-71 and M is Nb or Ta or mixtures, with or without substitution of V, as for example, LaNb 0 .8 V 0 .2 O 4 .
  • the prefix t denotes that the dispersant particles are retained in a tetragonal crystal form at an ambient, working temperature 100°-200° C.
  • the inventive ceramic composition comprises a ceramic matrix as a continuous phase with a hardness above about 800-1000 (Vickers diamond pyramid) and as a second component a tetragonal rare-earth niobate or tantalate or mixtures of these with each other and/or with a rare-earth vanadate.
  • the second component is present in an amount below about 25 wt. % of the composition and dispersed in the matrix as particles sized below about 5 microns, the particles of the second component have a transition temperature depressed by about 100°-200° C. from the transition temperature of the component in its bulk form.
  • the additives may be identified by the formula tRMO 4 where R is a rare earth element with an atomic number of 57-71 and M is Nb or Ta or mixtures thereof with or without V additions.
  • R has an atomic number of 57-71 when M is Nb (with or without V) and 60-71 when M is Ta.
  • M is Nb
  • the tetragonal phase transforms in a bulk sample between about 500°-800° C. depending on the rare-earth partner.
  • M is Ta the tetragonal phase transforms in a bulk sample between about 1300°-1420° C. depending on the rare earth.
  • Controlled changes in composition such as mixing niobates with tantalates or partially substituting V for Nb or Ta will permit the selection of a tetragonal transformation temperature optimized for a desired operating temperature of the ceramic body to which the dispersant is added.
  • the tetragonal transformation temperature will be manipulated so that it will not occur at operating temperature in the absence of a crack-generated stress but will occur in the presence of such a stress, thus bringing into operation the crack-hindering mechanism previously described.
  • T C can be varied between about 1400° C. and -100° C. with T D always lower than T C by about 100°-200° C. A maximum operating temperature based on T C being about 1400° C. would thus be about 1200° C.
  • Another means of manipulating the tetragonal transformation temperature, in addition to composition control lies in controlling the size of the dispersant particles and their surface condition: the transformation temperature decreases with decreasing particle size.
  • the following is an illustrative example of these control processes.
  • the compound LaNbO 4 undergoes the tetragonal transformation at 500° C. in a bulk sample.
  • V for Nb LaNb 0 .8 V 0 .2 O 4
  • the bulk-sample transformation is reduced to 95° C.
  • particle-size and surface-condition control fine particles of the V-substituted compound can be made to undergo the tetragonal transformation at about -75° C.
  • T C can be varied from 1400° C. to -200° C. and (T C -T D ) can be maintained at about 200° C.
  • T C -T D can be maintained at about 200° C.
  • compositions may be utilized for the dispersant, with the principal considerations being the operating temperature of the ceramic composition and/or the desired level of crack-attenuating properties.
  • the dispersants Preferably for high temperature use, contain Ta. These dispersant additives in general have a melting temperature above about 1600° C. and a bulk elastic modulus of 1-2 ⁇ 10 12 dynes cm -2 which is typically one-half or less of those of the host materials.
  • Illustrative dispersants are: NdTa 0 .8 V 0 .2 O 4 ; YdTa 0 .9 V 0 .2 O 4 ; HoTa 0 .95 V 0 .05 O 4 ; YbTaO 4 ; LaNb 0 .95 V 0 .05 O 4 ; NdNb 0 .75 V 0 .25 O 4 ; TbNb 0 .80 V 0 .20 O 4 ; TmNbO 4 ; SmTa 0 .8 Nb 0 .2 O 4 ; DyTa 0 .6 Nb 0 .4 O 4 ; ErTa 0 .4 Nb 0 .6 O 4 ; YTa 0 .2 Nb 0 .8 O 4 .
  • NdNb0 75V0.2504 is prepared by mixing Nd203 with Nb205 and V205 in the appropriate amounts in powder form with the mixture being sintered at 1400° C. in air for about 24 hours.
  • the host ceramic may be any one of the usual important oxides and preferably is Al 2 O 3 , ZrO 2 , MgO or mixtures of Al 2 O 3 and SiO 2 such as mullite. They are used in the preparation as particles sized below about 5 microns: the principal consideration being sinterability.
  • the dispersants are also used as small particles of 5 microns and below, advantageously preferably about 0.1-5 microns and preferably about 0.1-2 microns.
  • the smaller particles tend to enhance the depressant effect on the bulk transition temperature and facilitate the generation of a uniform dispersant distribution.
  • the dispersants is incorporated into the ceramic in an amount less than about 25 wt. %.
  • the lower limit is sufficient to enhance the desired performance of the ceramic composition.
  • the range is about 3-25 wt. % and preferably about 8-15 wt. %.
  • the limitation as to upper sintering temperature is the melting point of the dispersant phase which usually ranges from 1600°-2000° C.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Compositions Of Oxide Ceramics (AREA)

Abstract

The invention is a ceramic composition containing a new class of dispersant for hindering crack propagation by means of one or more energy-dissipative mechanisms. The composition is composed of a ceramic matrix with dispersed particles of a transformation-prone rare-earth niobate, tantalate or mixtures of these with each other and/or with a rare-earth vanadate. The dispersants, having a generic composition tRMO4, where R is a rare-earth element, B is Nb or Ta and O is oxygen, are mixed in powder form with a powder of the matrix ceramic and sintered to produce a ceramic form or body. The crack-hindering mechanisms operates to provide improved performance over a wide range of temperature and operating conditions.

Description

CONTRACTUAL ORIGIN OF THE INVENTION
The United States Government has rights in this invention pursuant to Contract No. W-31-109-ENG-38 between the U.S. Department of Energy and The University of Chicago representing Argonne National Laboratory.
BACKGROUND OF THE INVENTION
This invention relates to new ceramic compositions with useful properties extending into high temperature ranges of 800° C. and above and more particularly to ceramic compositions containing in dispersed form an additive class which absorbs stress-related energies transmitted in the composition. These additives may be characterized as transformation-prone rare-earth niobates, tantalates or mixtures of these with each other and/or mixtures with rare-earth vanadates. The dispersant is incorporated as small particles in a ceramic matrix in order to attenuate or hinder the propagation in the matrix of cracks that arise from stress.
Ceramics have been proposed as replacements for metals in a number of important products including those for high temperature use such as turbine blades, cylinder liners and heads for internal combustion engines, connecting rods, and the like. Ceramics have also been used as liners in various industrial processing equipment including equipment for coal gasification.
Ceramics in general are composed of hard brittle materials such as Al2 O3, ZrO2, MgO and mixtures of oxides such as mullite (Al2 O3 and SiO2) As small particles, these materials are mixed with sintering aids and sintered at elevated temperatures to cause the particles to adhere together in the desired shape. Stresses in these materials caused by temperature variations and/or mechanical loads limit the performance of the ceramics. Excessive stresses cause cracks to form and grow across the structural shapes. In some instances, these cracks may travel at or near the speed of sound and are not effectively hindered nor blocked.
Some additives have been incorporated into ceramic compositions to reduce the effect of stresses on performance. One of these involves the addition of an alloying ingredient (CaO is typical) to ZrO2 in order to achieve a structure in which the matrix consisting of the cubic form of ZrO2 contains as a dispersant fine particles of the tetragonal form of ZrO2. Another involves adding ZrO2, wholly or partially in the tetragonal form, to Al2 O3 or mullite. The principal mechanism believed to be associated with the beneficial effect of both of these additives involves the action of an advancing crack in producing a stress-induced transformation of the tetragonal form of ZrO2 to the monoclinic form with a resultant volume change. A change in the free energy of the system occurs and, as a consequence, there is an attenuation of crack progression. Further details are provided in the article "Transformation Toughening by Dispersed Polycrystalline Zirconia" by R. Stevens and P. A. Evans, Br. Ceram. Trans. J., 83, 28-31 (1984).
While the effect of a tetragonal ZrO2 dispersant in a cubic ZrO2 matrix or in an Al2 O3 or mullite matrix has interesting results, this approach is limited in its upper operating temperature. This is because the tetragonal form of the ZrO2 dispersant necessary for the beneficial effect cannot be retained above about 800° C. Moreover, it appears that the tetragonal ZrO2 dispersant functions only by the volume-change effect of the transformation.
Still another limitation in the use of tetragonal ZrO2 as a dispersant at lower temperature as well as higher temperature is the need for a complex, difficult-to-control interplay of additive composition thermal treatment and dispersant particle size that is difficult to manipulate in achieving satisfactory level of crack attenuation. When higher operating temperatures of 800° C. to 1200° C. are required for ceramics; and/or when additional crack-attenuating functions are sought and/or when better crack-attenuation control is required at any operating temperature: other dispersant additives would be desirable.
Accordingly, one object of the invention is an additive system to improve crack attenuation at higher temperatures in ceramics. Another object of the invention is an additive system which acts as an energy absorber through one and preferably more than one mechanism. An additional object of the invention is an additive system which provides a range of additives useful, effective and controllable under different temperature conditions and in different ceramics. A further object of the invention is an additive system combining two or more of the above objects. These and other objects of the invention will become apparent from the following detailed invention.
SUMMARY OF THE INVENTION
Briefly, the invention is directed to a ceramic composition particularly useful at temperatures above about 800° C. and comprising a ceramic matrix and an additive system based on a transformation-prone rare-earth niobate, tantalate or mixtures of these with each other and/or with a rare-earth vanadate. The general formula for these additives is tRMO4 where R is a rare earth element with an atomic number in the range of 57-71 and M is Nb or Ta or mixtures, with or without substitution of V, as for example, LaNb0.8 V0.2 O4. The prefix t denotes that the dispersant particles are retained in a tetragonal crystal form at an ambient, working temperature 100°-200° C. below the temperature at which the tetragonal form would exist in a bulk sample of RMO4. The method of achieving this retention is an essential part of the invention, as will be described. These additives, when dispersed as small particles in a ceramic mixture, undergo in the temperature range 800°-1200° C., a stress-induced transformations to a monoclinic form and thereby impart the same crack-attenuating mechanism over this higher temperature range that tZrO2 provides only at 800° C. and below.
These new dispersants also in general have the capacity to provide other mechanisms for hindering crack propagation. One of these is the stress-induced motion of domain walls that occur concurrently with the transformation. This additional energy-dissipative mechanism accompanying crack impingement can slow down and ultimately halt crack motion. Another mechanism lies in the low inherent sonic velocity that is a characteristic of the tRMO4 dispersant. The velocity of crack propagation at sonic or near-sonic levels through a tRMO4 dispersant particle should be attenuated by as much as 50% relative to the velocity in a matrix such as Al2 O3, leading to a dissipative "out-of-step", noncooperative crack movement. All of the foregoing crack-hindering mechanisms can operate collectively and interactively in a tRMO4 dispersant, thus providing advantages with respect to other dispersants.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The inventive ceramic composition comprises a ceramic matrix as a continuous phase with a hardness above about 800-1000 (Vickers diamond pyramid) and as a second component a tetragonal rare-earth niobate or tantalate or mixtures of these with each other and/or with a rare-earth vanadate. The second component is present in an amount below about 25 wt. % of the composition and dispersed in the matrix as particles sized below about 5 microns, the particles of the second component have a transition temperature depressed by about 100°-200° C. from the transition temperature of the component in its bulk form.
The additives may be identified by the formula tRMO4 where R is a rare earth element with an atomic number of 57-71 and M is Nb or Ta or mixtures thereof with or without V additions. Advantageously, R has an atomic number of 57-71 when M is Nb (with or without V) and 60-71 when M is Ta. When M is Nb, the tetragonal phase transforms in a bulk sample between about 500°-800° C. depending on the rare-earth partner. When M is Ta, the tetragonal phase transforms in a bulk sample between about 1300°-1420° C. depending on the rare earth. Controlled changes in composition such as mixing niobates with tantalates or partially substituting V for Nb or Ta will permit the selection of a tetragonal transformation temperature optimized for a desired operating temperature of the ceramic body to which the dispersant is added. The tetragonal transformation temperature will be manipulated so that it will not occur at operating temperature in the absence of a crack-generated stress but will occur in the presence of such a stress, thus bringing into operation the crack-hindering mechanism previously described.
If the bulk transition temperature is TC and the depressed transition temperature is TD (TC >TD), then the operating temperature TOP is such that TC >TOP >TD. For the preferred effect, TOP should be close to but always greater than TD. By controlling the chemical composition of the dispersant material, TC can be varied between about 1400° C. and -100° C. with TD always lower than TC by about 100°-200° C. A maximum operating temperature based on TC being about 1400° C. would thus be about 1200° C.
Another means of manipulating the tetragonal transformation temperature, in addition to composition control lies in controlling the size of the dispersant particles and their surface condition: the transformation temperature decreases with decreasing particle size. The following is an illustrative example of these control processes. The compound LaNbO4 undergoes the tetragonal transformation at 500° C. in a bulk sample. By a partial substitution of V for Nb (LaNb0.8 V0.2 O4), the bulk-sample transformation is reduced to 95° C. By particle-size and surface-condition control, fine particles of the V-substituted compound can be made to undergo the tetragonal transformation at about -75° C. More generally, by changing the amount and nature of M (Ta, Nb, or partial replacement by V) TC can be varied from 1400° C. to -200° C. and (TC -TD) can be maintained at about 200° C. Thus by changing the chemical concentration of the dispersant, an operating range of temperature TC >TOP >TD can be obtained suitable for different products.
The following generic compositions may be utilized for the dispersant, with the principal considerations being the operating temperature of the ceramic composition and/or the desired level of crack-attenuating properties.
a) R Ta.sub.(1-x) Vx O4 where 0≦x≦0.3
b) R Nb.sub.(1-x) Vx O4 where 0≦x≦0.3
c) R Ta.sub.(1-x) Nbx O4 where 0≦x≦1.0
for a) and c) R=elements 39 and 60-71; b) R=elementa 39 and 57-71.
Preferably for high temperature use, the dispersants contain Ta. These dispersant additives in general have a melting temperature above about 1600° C. and a bulk elastic modulus of 1-2×1012 dynes cm-2 which is typically one-half or less of those of the host materials. Illustrative dispersants are: NdTa0.8 V0.2 O4 ; YdTa0.9 V0.2 O4 ; HoTa0.95 V0.05 O4 ; YbTaO4 ; LaNb0.95 V0.05 O4 ; NdNb0.75 V0.25 O4 ; TbNb0.80 V0.20 O4 ; TmNbO4 ; SmTa0.8 Nb0.2 O4 ; DyTa0.6 Nb0.4 O4 ; ErTa0.4 Nb0.6 O4 ; YTa0.2 Nb0.8 O4. They are prepared by repetitive sintering of the requisite amounts of the component oxides (R2 O3, Ta2 O5, Nb2 O5, V2 O5) in air or air enriched with oxygen in the range 1200°-1600° C. to ensure chemical homogeniety. As an illustration, NdNb0 75V0.2504 is prepared by mixing Nd203 with Nb205 and V205 in the appropriate amounts in powder form with the mixture being sintered at 1400° C. in air for about 24 hours.
The host ceramic may be any one of the usual important oxides and preferably is Al2 O3, ZrO2, MgO or mixtures of Al2 O3 and SiO2 such as mullite. They are used in the preparation as particles sized below about 5 microns: the principal consideration being sinterability.
The dispersants are also used as small particles of 5 microns and below, advantageously preferably about 0.1-5 microns and preferably about 0.1-2 microns. The smaller particles tend to enhance the depressant effect on the bulk transition temperature and facilitate the generation of a uniform dispersant distribution.
Usually, the dispersants is incorporated into the ceramic in an amount less than about 25 wt. %. The lower limit is sufficient to enhance the desired performance of the ceramic composition. Advantageously, the range is about 3-25 wt. % and preferably about 8-15 wt. %.
Conventional state-of-the art ceramic preparation procedures are utilized for sintering the host materials. Particles of the matrix material, sized below about 5 microns are intimately mixed by ball milling with particles of the dispersant sized 0.1-5 microns. Sintering aids such as MgO or other conventional sintering aids may be added as necessary. The mixed powders are compressed into compacts of appropriate size and shape, and these are then sintered in air or in air enriched with oxygen between 1300° C. and 1600° C. for 10 hours or less.
The limitation as to upper sintering temperature is the melting point of the dispersant phase which usually ranges from 1600°-2000° C.
These new dispersants also in general have the capacity to provide other mechanisms for hindering crack propagation. One of these is the stress-induced motion of domain walls that occur concurrently with the transformation. This additional energy-dissipative mechanism accompanying crack impingement can slow down and ultimately halt crack motion. Another mechanism lies in the low inherent sonic velocity that is a characteristic of the tRMO4 dispersant. The velocity of crack propagation at sonic or near-sonic levels through a tRMO4 dispersant particle should be attenuated by as much as 50% relative to the velocity in a matrix such as Al2 O3, leading to a dissipative "out-of-step", noncooperative crack movement. All of the foregoing crack-hindering mechanisms can operate collectively and interactively in a tRMO4 dispersant, thus providing advantages with respect to other dispersants.

Claims (10)

The embodiments of this invention in which an exclusive property or privilege is claimed are defined as follows:
1. A ceramic composition consisting essentially of a ceramic matrix of Al2 O3, mullite, ZrO2, MgO or mixtures thereof as a continuous phase with a hardness above about 800 and as a second component a tetragonal rare-earth niobate, tantalate or mixtures of these with each other and/or with a rare-earth vanadate, the second embodiment being present in an amount in the range of about 3-25 wt. % of the composition and dispersed in the matrix as particles sized below about 5 microns, the particles of the second component in the matrix having a transition temperature TD being below the transition temperature for the second component in bulk or TC.
2. The ceramic composition of claim 1 wherein the second component has a depressed transition temperature TD above about 800° C. and below TC by at least about 100° C., a melting temperature above about 1600° and a hardness below about 500 (Vickers pyramid).
3. The ceramic composition of claim 1 wherein the second component has the formula tRMO4 wherein R is a rare earth, M is Nb or Ta or mixtures thereof with or without V, and R has an atomic number in the range of 39 and 57-71 when M is Nb and 39 and 60-71 where M is Ta.
4. The ceramic composition of claim 3 wherein the second component has a depressed transition temperature above about 800° C., a melting temperature above about 1600° C., and a hardness below about 500.
5. The ceramic composition of claim 5 wherein the second component has a stress-free transition temperature between 800° and 1200° C. and is present in the amount of about 8-15 wt. %.
6. The ceramic composition of claim 5 wherein the particles of the second component are sized in the range of about 0.1-2 microns.
7. The ceramic composition of claim 5 wherein R is Ho and M is Ta.
8. The ceramic composition of claim 5 wherein R is Nd and M is Ta.
9. The ceramic composition of claim 5 wherein R is Nd and M is Nb0.6 Ta0.4.
10. The ceramic composition of claim 5 wherein R is Nd and M is Ta0.8 V0.2.
US06/750,122 1985-07-01 1985-07-01 Ceramics containing dispersants for improved fracture toughness Abandoned USH302H (en)

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4939107A (en) 1988-09-19 1990-07-03 Corning Incorporated Transformation toughened ceramic alloys
US5294576A (en) * 1988-01-13 1994-03-15 Shinko Electric Industries Co., Ltd. Mullite ceramic compound
US5350927A (en) * 1992-06-17 1994-09-27 Mitech Scientific Corp. Radiation emitting ceramic materials and devices containing same
US5472720A (en) * 1992-06-17 1995-12-05 Mitec Scientific Corporation Treatment of materials with infrared radiation
CN107285768A (en) * 2017-07-04 2017-10-24 昆明理工大学 A kind of preparation method of rare earth tantalate refractory ceramics
CN107513263A (en) * 2017-10-19 2017-12-26 威海联桥新材料科技股份有限公司 A kind of thermoplastic elastomer (TPE) gasket material and its production method

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US2040215A (en) 1933-05-15 1936-05-12 Rava Alexander Method of making refractory materials
US3287143A (en) 1961-08-30 1966-11-22 Zirconium Corp Of America Gas-tight refractory article and method of making same
US4303447A (en) 1980-04-02 1981-12-01 University Of Illinois Foundation Low temperature densification of zirconia ceramics
US4406699A (en) 1981-06-09 1983-09-27 Beck David E High-temperature electrically conductive ceramic composite and method for making same
US4507394A (en) 1982-12-24 1985-03-26 Ngk Insulators, Ltd. High electric resistant zirconia and/or hafnia ceramics

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2040215A (en) 1933-05-15 1936-05-12 Rava Alexander Method of making refractory materials
US3287143A (en) 1961-08-30 1966-11-22 Zirconium Corp Of America Gas-tight refractory article and method of making same
US4303447A (en) 1980-04-02 1981-12-01 University Of Illinois Foundation Low temperature densification of zirconia ceramics
US4406699A (en) 1981-06-09 1983-09-27 Beck David E High-temperature electrically conductive ceramic composite and method for making same
US4507394A (en) 1982-12-24 1985-03-26 Ngk Insulators, Ltd. High electric resistant zirconia and/or hafnia ceramics

Non-Patent Citations (1)

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Title
Stevens and Evans, "Transformation Toughening by Dispersed Polycrystalline Zirconia", Br. Ceram. Trans. J., 83, 28-31 (1984).

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5294576A (en) * 1988-01-13 1994-03-15 Shinko Electric Industries Co., Ltd. Mullite ceramic compound
US4939107A (en) 1988-09-19 1990-07-03 Corning Incorporated Transformation toughened ceramic alloys
US5350927A (en) * 1992-06-17 1994-09-27 Mitech Scientific Corp. Radiation emitting ceramic materials and devices containing same
US5472720A (en) * 1992-06-17 1995-12-05 Mitec Scientific Corporation Treatment of materials with infrared radiation
US5707911A (en) * 1992-06-17 1998-01-13 Mitech Scientific Corp. Infrared radiation generating ceramic compositions
CN107285768A (en) * 2017-07-04 2017-10-24 昆明理工大学 A kind of preparation method of rare earth tantalate refractory ceramics
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