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WO1991005747A1 - Procede de traitement thermique de materiaux ceramiques instables par chauffage aux micro-ondes et absorbeurs de micro-ondes utilises dans ce procede. - Google Patents

Procede de traitement thermique de materiaux ceramiques instables par chauffage aux micro-ondes et absorbeurs de micro-ondes utilises dans ce procede. Download PDF

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Publication number
WO1991005747A1
WO1991005747A1 PCT/CA1990/000358 CA9000358W WO9105747A1 WO 1991005747 A1 WO1991005747 A1 WO 1991005747A1 CA 9000358 W CA9000358 W CA 9000358W WO 9105747 A1 WO9105747 A1 WO 9105747A1
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WO
WIPO (PCT)
Prior art keywords
bed
ceramic
protective
microwave
susceptor
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/CA1990/000358
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English (en)
Inventor
Prasad Shrikrishna APTÉ
Robert Murray Kimber
Mark Christopher Lawrence Patterson
Raymond Yves Roy
David Nelson Mitchell
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rio Tinto Alcan International Ltd
Original Assignee
Alcan International Ltd Canada
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Alcan International Ltd Canada filed Critical Alcan International Ltd Canada
Publication of WO1991005747A1 publication Critical patent/WO1991005747A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
    • B01J19/12—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor employing electromagnetic waves
    • B01J19/122—Incoherent waves
    • B01J19/126—Microwaves
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B30—PRESSES
    • B30B—PRESSES IN GENERAL
    • B30B11/00—Presses specially adapted for forming shaped articles from material in particulate or plastic state, e.g. briquetting presses, tabletting presses
    • B30B11/001—Presses specially adapted for forming shaped articles from material in particulate or plastic state, e.g. briquetting presses, tabletting presses using a flexible element, e.g. diaphragm, urged by fluid pressure; Isostatic presses
    • 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
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/64—Burning or sintering processes
    • 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
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/64—Burning or sintering processes
    • C04B35/645—Pressure sintering
    • C04B35/6455—Hot isostatic pressing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
    • B01J2219/12—Processes employing electromagnetic waves
    • B01J2219/1203—Incoherent waves
    • B01J2219/1206—Microwaves
    • B01J2219/1209—Features relating to the reactor or vessel
    • B01J2219/1212—Arrangements of the reactor or the reactors
    • B01J2219/1215—Single reactor

Definitions

  • This invention relates to heat-treating ceramic powders. More particularly, the invention relates to a method of heat-treating thermally unstable ceramic powders utilizing microwaves to generate the required heat, to a susceptor composition used in the method and to the sintered products thus produced.
  • the body is then heated by conduction, convection and/or radiation from the susceptor powder either until the desired treatment temperature is reached or until the ceramic reaches a temperature at which it does absorb microwave energy sufficiently for further direct heating to the desired temperature.
  • the problem posed by the thermal instability or reactivity of certain ceramics can also be overcome by providing a suitable protective atmosphere for the green body during the heating procedure.
  • the decomposition and oxidation of silicon nitride can be substantially prevented by heating the material in an atmosphere containing a suitable partial pressure of nitrogen.
  • the partial pressure required in any particular case depends on the time of the procedure and on the desired treatment temperature.
  • decomposition can occur even under pure nitrogen at one atmosphere.
  • a method of heat-treating a body of thermally unstable ceramic material which comprises at least partially surrounding said body with a bed of particulate material and irradiating said bed with microwave energy in an oxygen-containing gas, said bed comprising effective amounts of: (a) a microwave susceptor if said unstable ceramic is not itself a microwave susceptor; (b) a protective material capable of generating a localized protective atmosphere which reduces decomposition and/or oxidation of the ceramic material; (c) an oxygen getter; and (d) a material having sufficiently good thermal conductivity to prevent excessive localized heating in said bed.
  • a particulate material capable of being used as a protective bed for heat- treating a body of an unstable .ceramic material with microwaves in an oxygen-containing gas, said material comprising effective amounts of: (a) a microwave susceptor, if said ceramic material is a non-susceptor; (b) a protective material capable of generating a localized atmosphere which discourages decomposition of the unstable ceramic; (c) an oxygen getter; and (d) a material having sufficiently good thermal conductivity to prevent excessive localized heating in said particulate material during microwave irradiation thereof.
  • a process for joining bodies made of thermally unstable ceramics which comprises: bringing said bodies into contact; surrounding said bodies in the area of contact with a protective bed of particulate material; irradiating said protective bed in an oxygen- containing gas with microwave ' radiation sufficiently to heat said bed and bodies to cause joining of the latter; and allowing said bodies to cool; wherein said bed of particulate material comprises effective amounts of
  • the method can be carried out in a low pressure oxygen-containing atmosphere, i.e. in a conventional microwave furnace open to atmospheric air.
  • Figure 1 is a side elevational view of a hot isostatic press used to carry o ⁇ t a preferred embodiment of one form of the present invention
  • Figure 2 is a view similar to Figure 1 except that the press is in the pressing position;
  • Figure 3 is a resonant cavity, shown on an enlarged scale, suitable for the simultaneous heating and pressing of a product;
  • Figure 4 is a cross-section of apparatus used to carry out a preferred embodiment of another form of the present invention.
  • Figure 5 is a graph showing the average grain size across the diameter of a silicon nitride sintered product produced according to Example 5 below; and Figure 6 is a photomicrograph of the sintered product of Example 5.
  • the powder bed used in the present invention may be a mixture of different ingredients each one of which provides one only of the properties (a) to .(d) mentioned above. However, a single ingredient may provide two or more, or possibly even all, of the stated functions so the number of ingredients of the powder bed should be reduced. The number of ingredients should preferably be chosen on the basis that the desired properties should be optimised, even if this means providing a separate ingredient for each property.
  • the various properties required in the powder bed are explained in more detail below. Unless the unstable ceramic is itself an adequate microwave susceptor, the powder bed should contain at least one microwave susceptor.
  • a microwave susceptor is a material that absorbs energy rom microwaves at a rate faster than the rate at which it loses energy.
  • the microwave susceptor used in the powder bed of the present invention can be any material that is capable of absorbing (coupling with) microwave radiation to the extent necessary to raise the temperature of the ceramic body at least partially buried in the bed to the desired temperature (at which the body itself absorbs sufficient energy directly from the microwaves) .
  • Silicon carbide acts as a microwave susceptor and has the advantage of also being an oxygen getter (see below) .
  • Other carbides and carbon may replace silicon carbide in this function and other suitable microwave susceptors include porcelain, soda- lime glass and barium titanate
  • the protective material used in the susceptor bed depends on the nature of the unstable ceramic used for the body to be heat-treated.
  • the protective material generally functions by generating an atmosphere around the body to be heated that protects the body against decomposition and/or oxidation.
  • the ceramic body is made of (or contains) silicon nitride
  • the protective material may itself be silicon nitride. This decomposes (Si 3 N 4 ⁇ 3Si + 2N 2 ) and forms an atmosphere having a high nitrogen partial pressure localized around the body which protects the body against further decomposition.
  • the decomposition of the silicon nitride begins in the bed (rather than the body) since the bed heats up first and is initially hotter than the body. When the body itself begins to heat, the protective nitrogen atmosphere has already been established.
  • protective materials for particular non-oxide ceramics are:
  • lead based ceramics e.g. lead zirconate titanate and lead lanthanate zirconate titanate
  • lead-based protective atmospheres have adequate conductivity and are microwave susceptors.
  • An oxygen getter is a material which at least partially eliminates oxygen from the localized atmosphere around the body to be heated, at least at the temper ⁇ atures at which the unstable ceramics are vulnerable to oxidation. Getters function by reacting chemically with oxygen to lower the partial pressure .of the oxygen to such an extent that oxygen is minimized.
  • Metal carbides generally, and silicon carbide in particular, are effective oxygen getters, as are carbon and oxidizable metals such as Zr, Ca, Al, Ti, W, Mo, Ta and Cu.
  • the material having good thermal conductivity can be any material that allows uniform heating in the bed and transference of the heat to the body. This prevents the development of hot spots (large temperature gradients) in the bed leading possibly to thermal runaways as well as instabilities in electrical and thermal distribution.
  • a material is often required in the bed because the other ingredients are often ceramics of low thermal conductivity.
  • Boron nitride is a particularly suitable material for this, but aluminum nitride for example, could alternatively be used.
  • a high metal content in the bed (for example, when metals are used as oxygen getters) also provides high thermal conductivity. It is difficult to give preferred conductivity ranges because optimum values vary according to bed size and composition.
  • the ingredients of the powder bed should each be present in an "effective" amount, i.e. the amount necessary to exert their desired effect (heating, protection, oxygen removal and conductivity) .
  • the minimum amount of each material depends on the nature of the material employed. For example, when the powder bed is a mixture of SiC, Si 3 N 4 and BN, the minimum amounts are respectively 25 wt%, 20 wt% and 10 wt%. The preferred relative proportions are about 40:30:30 in wt% respectively.
  • the method of the invention can be used to protect a variety of unstable ceramics especially non-oxide ceramics, in addition to those mentioned above, e.g. superconductors I, II and III using a super-conductor powder bed.
  • the method of the invention can be used for virtually any type of heat-treating of ceramic bodies including sintering, annealing, recrystallization of glassy phases, other thermal treatments and joining together of ceramic bodies.
  • the joining technique will be described more fully below.
  • sintering aids may have to be incorporated into the bodies to be heated in order to facilitate sintering.
  • Sintering aids are sometimes microwave susceptors, in which case they contribute to the heating of the body.
  • the powder bed can be prepared simply by mixing the powdered ingredients in the normal way (e.g. stirring, shaking, tumbling etc.) and the particle sizes of the different ingredients may be the same or different.
  • the average particle size is not particularly critical, although smaller average particle sizes are preferred in order to confine the protective atmosphere with the bed and to limit the penetration of air from outside.
  • a particularly preferred type of bed can be prepared by the following procedure using particles of different sizes.
  • the body to be treated can be buried in a bed of the ingredient having;the largest particles.
  • the ingredient having the second largest particles can then be poured on top of the bed and the bed gently shaken or vibrated until the smaller particles flow down into the interstices between the larger particles. This is continued until the ingredient having the smallest particles is then poured on top of the bed and the bed gently shaken or vibrated until the small particles flow down and fill the voids remaining in the bed.
  • the relative particle sizes must be such that such void filling can take place.
  • This preferred procedure produces a dense bed, usually having a void component of less than 30% by volume, which is easy to construct.
  • the small remaining void size reduces oxygen permeability and the fact that the particles have considerably different sizes means that the components are easy to separate from each other after use.
  • the protective material is used to form the smallest particles because the resulting large surface to volume ratio ensures thorough evolution of the protective gases and the size of the particles ensures a dense and uniform layer adjacent to the surface of the green body.
  • the susceptor bed can be arranged in layers of higher or lower thermal conductivity, or areas of higher or lower microwave absorption (i.e. heating) . Similar compensatory effects can be made by specifically designing the size and/or shape of the bed itself.
  • the process of the invention can also be combined with a hot isostatic pressing technique carried out as the ceramic material is being heated by the microwaves.
  • the heating and pressing steps are carried out together, provision must be made to introduce the microwaves into the pressurized cavity. This can be done by equipping the chamber with a high pressure-resistant microwave transparent window or a solid microwave antenna passing through the vessel wall in a pressure tight arrangement.
  • a wave guide can be introduced into an opening in the chamber during the heating step and then, for the pressing step, the waveguide can be removed and replaced by a high-pressure resistant closure device.
  • the pressure inside the cavity can be elevated to the desired extent (usually 40,000-50,000 psi) during the pressing step by introducing a gas from a pressurized container or a high pressure pump. If the heating and pressing steps are to be carried out simultaneously, the cavity can be sealed during heating and the body subjected to autogenously-generated pressure.
  • the pressure chamber normally made of steel, should be designed as a single or multi-mode cavity resonator for a particular wavelength.
  • the pressure chamber of a conventional press can be modified to achieve this, for example by inserting conducting cylinders of predetermined diameters into the chamber so that only the required cavity modes will resonate.
  • a cavity diameter of between 7.2 and 9.4 cm is required to excite the dominant mode in a cylindrical cavity.
  • other modes may have to be excited and this may be achieved by making the chamber larger.
  • the pressure vessel itself may be specifically designed to ensure resonance of the desired modes.
  • magnetrons can be employed to generate the microwaves, e.g. magnetrons capable of generating microwaves at 2.45 GHz or 915 MHz at power levels of about 500-600 watts. Magnetrons of this type can generate sufficient heat within the body to raise the temperature rapidly to the sintering level, e.g. up to about 2100*C in as little as 5 to 10 minutes.
  • FIG. 1 A preferred example of a hot isostatic press according to the present invention is shown in Figs. 1 and 2.
  • the press 10 comprises an open rectangular framework 11 supporting a rigid "C-shaped M beam 12.
  • a hydraulic ram 13 is supported by the lower framework members and is laterally slidable between the positions shown respectively in Figs. 1 and 2.
  • the piston 14 of the ram supports a pressure vessel 15, the interior of which forms a chamber designed to act as a resonant cavity for microwaves.
  • the chamber contains a pre-form body 16 (shown in broken lines) to be treated supported in a powder bed in accordance with the invention (not shown) .
  • the upper end of the pressure vessel has an open collar 17.
  • An engaging flange 18 is rigidly attached to the beam 12 at one side and has a central hole which receives a waveguide 19.
  • the waveguide is connected to a magnetron (not shown) which generates microwaves of the desired frequency. These microwaves are conveyed by the waveguide in the direction of the arrow into the interior of the pressure vessel 17.
  • the equipment is used as follows. Firstly, the pre ⁇ form 16 is subjected to a heating cycle. For this, the apparatus is arranged in the manner shown in Figure 1.
  • the hydraulic ram 13 presses the pressure vessel 15 against the flange 18.
  • the magnetron is operated to direct microwave energy along the waveguide 19, through the collar 17 and into the chamber where the energy is absorbed by the powder bed so that the temperature of the body rises rapidly. After a length of time suitable to raise the temperature of the body to the sintering range, the magnetron is switched off and the ram is lowered.
  • a high pressure-sealing lid 20 is placed on the pressure vessel and the assembly moves to the right hand position as shown in Figure 2 whereupon the ram is actuated to force the upper end of the pressure vessel and lid 20 against the upper end of the C-shaped beam 12 while the opposite end of the ram is braced against the lower end of the beam.
  • Gas at high pressure is introduced into the pressure vessel through inlet 21.
  • the pressurized gas introduced into the vessel during this part of the cycle may have a pressure as high as 20,000 psi or more.
  • the pressure has the same effect on the ceramic product as conventional hot isostatic pressing.
  • the body is maintained at a suitable temperature during this step by virtue of the powder bed in which it is embedded by virtue of its own thermal mass. After the pressurizing step is complete, the pressure in the pressure vessel is relieved and the product is allowed to cool down whereupon it may be removed from the pressure vessel and powder bed.
  • the apparatus may comprise two or more presses of the illustrated design, each being connected to a single magnetron via their waveguides 19.
  • Switching means are provided in the waveguides so that microwave energy may be conveyed to only one of the presses at a time. In this way, when microwave energy is no longer required for one press
  • FIG 3 shows an alternative pressure vessel 30.
  • the interior of the pressure vessel forms a chamber which acts as a resonant cavity.
  • the microwave radiation is introduced into the resonant cavity by means of antenna 31 which extends into the cavity through a high pressure seal 32.
  • a pressure head 33 completes the sealing of the cavity and a pressurized gas is introduced through inlet 35. Because this equipment is capable of both pressurizing and irradiating a sample 34 at the same time, if desired, there is no need to separate the heating step and the pressurizing step as in the previous embodiment and both can be carried out with the press in the position shown in Figure 2, i.e. with the pressure vessel clamped between the ram and the C-shaped beam.
  • alternative apparatus may comprise a chamber sealed by a lid having a microwave-transparent window and a high pressure shutter behind the window to protect the window from the high pressure in the chamber during the pressing cycle.
  • microwaves can be introduced through the window during the heating cycle and then, after closure of the shutter, pressurized gas may be introduced into the chamber for the pressing cycle.
  • the window may be made of quartz and should have an area of approximately 2 inches.
  • the body to be heat-treated by the method of the present invention is often a compact of a single powdered material but may also be a mixture of different powders or a mixture of a powder with other solid bodies, e.g. fibres.
  • the body may consist solely of one or more unstable ceramics or may be a mixture of one or more unstable ceramics with one or more stable (e.g. oxide) ceramics.
  • the latter may be, for example, sintering aids and are usually present in the minority.
  • the method of the present invention is particularly suitable for sintering nitrides, e.g. silicon nitride, aluminum nitride, etc.
  • the invention is particularly suited for the heat treatment and sintering of such additional materials as aluminum nitride containing up to 5 wt.% of Y 2 0 3 as a sintering aid, which has been sintered to densities in excess of 99% of theoretical in a powder bed comprising A1N and SiC in various proportions, e.g. 80% A1N and 20% SiC.
  • the SiC acts as a susceptor and an oxygen getter, while the A1N acts as a good thermal conductor.
  • the SiC may contaminate the product and if this is undesired its content is maintained as low as possible down to 5 wt.%.
  • the A1N body may be surrounded with A1N powder held in a thin-walled alumina crucible itself embedded in a Sic powder bed so that there is no direct contact between the body and the SiC powder. This makes it clear that the components of the powder bed are not necessarily intimately mixed and may be confined to different zones which may be separated from each other. An overpressure is not so important when sintering A1N as it is when sintering silicon nitride, so the use of silicon nitride in the powder bed is not always necessary.
  • Titanium diboride has also been sintered to a density of 87% of theoretical using the process of the invention using a powder bed of alumina and silicon carbide.
  • the SiC provides high thermal conductivity and an oxygen getter ability. Less of the thermal conductor is necessary in this case because (a) the titanium diboride has a very high melting point of around 2900*C and (b) titanium diboride becomes an electrical conductor at high temperatures, thereby limiting the amount of field it is capable of absorbing.
  • the sintered silicon nitride-containing materials produced by the process of the invention such as sintered alpha and beta silicon nitride, silicon nitride mixtures with other ceramics, e.g.
  • alumina and yttria, and sialons are, in particular, are believed to be a novel and unique forms of these materials and, as such, form part of this invention.
  • the grain size of these, and most likely other, products of the invention is significantly finer than that of conventionally sintered silicon nitride-containing materials.
  • the grain size of the conventional materials is typically greater than one micron and often as course as 3-4 microns.
  • the grains forming the product of the present invention are usually elongated in shape, typically having an aspect ratio of around 10:1 and this makes the measurement of grain size somewhat difficult because sections cut for examination through a product sample intersect the grains at various inclinations between 0 and 90* to the long axis.
  • the maximum grain size is especially difficult to measure because this requires a sufficient number of grains to be intersected in a plane parallel to their long axes, an unlikely event.
  • the grain size of the product of the invention is expressed as the average minimum grain size measured by microscopic examination.
  • the average minimum grain size of the products of the invention is 0.5 microns or less. This is found to be true for sintered alpha or beta silicon nitride, silicon nitride mixed with other ceramics (such as alumina and yttria) , sialons, etc. We have found that finer grain materials have improved wear properties and are thus more desirable than the equivalent conventional materials.
  • the process of the present invention may be used for joining bodies of unstable ceramics as well as heat treating or sintering ceramics. This can be achieved by placing (and preferably pressing) together the bodies to be joined, if desired, with an intermediary interposed between the bodies. The bodies are then surrounded with a bed according to the invention and the joint area is irradiated with microwaves to raise the temperature of the materials in the vicinity of the joint so that partial melting or sintering takes place and, upon cooling, a satisfactory joint is formed.
  • FIG. 4 shows equipment 40 for joining two ceramic bodies 41 and 42 via an intermediary body 43.
  • the intermediary body 43 is preferably a compressed sinterable green body made of the same material as the bodies 41 and 42 to be joined.
  • the resulting joint area is surrounded by a protective powder bed 44.
  • the bodies 41, 42 and 43 are pressed together by means of a load 45.
  • the powder bed is contained within a housing 46 which has microwave-transparent windows 47, 48 on opposite sides of the joint. Waveguides 49 and 50 are aligned with the windows 47, 48.
  • a magnetron (not shown) is connected to waveguide 49 and a grounded movable short 51 is positioned in waveguide 50.
  • the apparatus is cooled by water pipes 52 and a linear vertical differential transducer 53 is used to measure movements of the load 45.
  • the bodies are joined by operating the magnetron and adjusting the position of the short 51 to create standing waves 54 and 55 in the waveguides so that the apparatus forms a resonant cavity with the joint area positioned for maximum microwave absorption.
  • the protective bed 44 increases in temperature and raises the temperature of the bodies 41, 42 and 43.
  • the transducer 53 first registers an upward movement of the load 45 as the bodies expand and then a downward movement as the body 43 compacts, densifies and sinters. When there is no further movement of the load 45, the pro ⁇ cedure is complete and the bodies can be allowed to cool.
  • the use of a protective bed in accordance with the invention ensures that there is little or no decomposition of the bodies 41, 42 and 43 in the joint area in the final product.
  • a silicon carbide whisker reinforced alumina body (20% by volume) was sintered to approximately 85% of the theoretical density (10% of whiskers by volume sintered to 97%) by burying the body in a packed powder bed consisting of 30% by wt silicon carbide (susceptor and oxygen getter) , 30% by wt boron nitride (good thermal conductor) and 40% by wt silicon nitride (protective material) and heating the body and bed with microwaves in air. The heating time was 40 minutes and the microwave energy was 500 watts.
  • a powder mixture of silicon nitride containing 5 wt.% of A1 2 0 3 and 5 wt.% of Y 2 0 3 in a powder bed having the same composition as the bed of Example 4 was sintered by exposure to microwave irradiation and subsequently immediately hot isostatically pressed.
  • the product was sectioned and 30 frames were taken across a horizontal section and 17 frames taken across a vertical section. The data thus obtained is shown in the following tables:
  • the variance in D.max is quite high because of the high aspect ratio discussed earlier. As can be seen, the average minimum grain size is less than 0.5 ⁇ m.
  • Figure 6 is a photomicrograph of an etched section of the product at a magnification of 10,000 diameters.
  • the invention can be applied to the production of heat-treated and sintered bodies of ceramic materials used, for example, as electronic substrates, components of tools, electrical insulators and the like.

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Abstract

L'invention se rapporte à un procédé de frittage de matériaux céramiques thermiquement instables (généralement non oxyde) par chauffage aux micro-ondes. Dans ce procédé, un corps du matériaux céramique est au moins partiellement entouré d'un lit protecteur de matériau particulaire, puis le corps et le lit (34) sont soumis à un rayonnement de micro-ondes destiné à assurer le chauffage et le frittage du corps. Pour permettre la réalisation du procédé dans un gaz contenant de l'oxygène, tel que de l'air, et à basse pression, le lit contient des quantités efficaces de: (A) un absorbeur de micro-ondes, lorsque le matériau céramique instable ne l'est pas déjà; (b) un matériau protecteur capable de produire une atmosphère localisée qui réduit la décomposition et/ou l'oxydation du matériau céramique instable; (c) un getter d'oxygène; et (d) un matériau de conductivité thermique suffisamment bonne pour empêcher un chauffage localisé excessif dans le lit. Ce procédé peut être combiné avec une étape de pressage isostatique à chaud effectuée simultanément ou ultérieurement. L'invention se rapporte égallement au lit de matériau particulaire utilisé dans le procédé et à un procédé permettant d'assembler des corps de matériau céramique instable par rayonnement de micro-ondes en utilisant le lit protecteur.
PCT/CA1990/000358 1989-10-19 1990-10-19 Procede de traitement thermique de materiaux ceramiques instables par chauffage aux micro-ondes et absorbeurs de micro-ondes utilises dans ce procede. Ceased WO1991005747A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CA 2001062 CA2001062A1 (fr) 1989-10-19 1989-10-19 Methode de traitement thermique aux micro-ondes de ceramiques instables; les materiaux interactifs ainsi utilises
CA2,001,062 1989-10-19

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WO1991005747A1 true WO1991005747A1 (fr) 1991-05-02

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PCT/CA1990/000358 Ceased WO1991005747A1 (fr) 1989-10-19 1990-10-19 Procede de traitement thermique de materiaux ceramiques instables par chauffage aux micro-ondes et absorbeurs de micro-ondes utilises dans ce procede.

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EP (1) EP0495850A1 (fr)
JP (1) JP2628104B2 (fr)
CN (1) CN1054579A (fr)
AU (1) AU6540090A (fr)
CA (1) CA2001062A1 (fr)
WO (1) WO1991005747A1 (fr)

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0382530A3 (fr) * 1989-01-17 1992-01-02 Donald J. Adrian Compression isostatique à chauffage par micro-ondes et procédé s'y rapportant
EP0534797A1 (fr) * 1991-09-27 1993-03-31 General Mills, Inc. Céramique frittée susceptible d'être chauffée par micro-ondes
EP0631997A1 (fr) * 1993-06-30 1995-01-04 Sumitomo Electric Industries, Ltd. Corps fritté à base de nitrure de silicium et sa méthode de préparation
DE4340652A1 (de) * 1993-11-30 1995-06-01 Krupp Widia Gmbh Verbundwerkstoff und Verfahren zu seiner Herstellung
WO1995026940A1 (fr) * 1994-03-31 1995-10-12 Westaim Technologies Inc. Procede de frittage par micro-ondes
US5622905A (en) * 1993-06-30 1997-04-22 Sumitomo Electric Industries, Ltd. Silicon nitride based sintered body
US5698156A (en) * 1993-06-30 1997-12-16 Sumitomo Electric Industries, Ltd. Method of producing a silicon nitride based sintered body
RU2313508C2 (ru) * 2002-07-19 2007-12-27 Фита Цанфабрик Х.Раутер Гмбх Энд Ко. Кг Способ уплотнения керамических материалов под воздействием сантиметровых электромагнитных волн и сосуд для осуществления этого способа
WO2008077224A3 (fr) * 2006-12-27 2008-08-14 Fundacao Universidade Fed De S Compositions pour suscepteurs externes et suscepteurs externes destinés au frittage de céramiques par micro-ondes
EP2006267A4 (fr) * 2006-03-29 2009-09-02 Tokuyama Corp Procede et element de jonction de ceramique
EP1803329A4 (fr) * 2004-09-15 2011-08-03 Penn State Res Found Procede et appareil de synthese de phosphores par micro-ondes
US20130320001A1 (en) * 2012-06-04 2013-12-05 Denso Corporation Low-oxygen atmosphere apparatus
WO2018077735A1 (fr) * 2016-10-28 2018-05-03 Centre National De La Recherche Scientifique Procede de traitement thermique d'une piece en materiau ceramique par micro-ondes

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CN1111147C (zh) * 1999-07-22 2003-06-11 青岛大学 一种复合陶瓷的微波烧结方法
CN117083173A (zh) * 2021-03-12 2023-11-17 达姆施塔特工业大学 用于生产陶瓷的方法和装置以及陶瓷产品
CN113324877B (zh) * 2021-06-01 2025-04-11 上海应用技术大学 观测铝、镁熔液润湿角的极低氧分压密封室座滴法

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EP0308593A1 (fr) * 1987-09-24 1989-03-29 Questech Inc. Procédé et appareil pour la liaison par micro-ondes de corps en céramique non oxydée
EP0329338A2 (fr) * 1988-02-16 1989-08-23 Alcan International Limited Procédé et dispositif pour le chauffage de pièces à haute température et pression utilisant l'énergie de micro-ondes

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DE2000710B2 (de) * 1969-01-09 1977-04-21 United States Borax & Chemical Corp., Los Angeles, Calif. (V.StA.) Feuerfestes material
EP0308593A1 (fr) * 1987-09-24 1989-03-29 Questech Inc. Procédé et appareil pour la liaison par micro-ondes de corps en céramique non oxydée
EP0329338A2 (fr) * 1988-02-16 1989-08-23 Alcan International Limited Procédé et dispositif pour le chauffage de pièces à haute température et pression utilisant l'énergie de micro-ondes

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0382530A3 (fr) * 1989-01-17 1992-01-02 Donald J. Adrian Compression isostatique à chauffage par micro-ondes et procédé s'y rapportant
EP0534797A1 (fr) * 1991-09-27 1993-03-31 General Mills, Inc. Céramique frittée susceptible d'être chauffée par micro-ondes
US5622905A (en) * 1993-06-30 1997-04-22 Sumitomo Electric Industries, Ltd. Silicon nitride based sintered body
EP0631997A1 (fr) * 1993-06-30 1995-01-04 Sumitomo Electric Industries, Ltd. Corps fritté à base de nitrure de silicium et sa méthode de préparation
US5698156A (en) * 1993-06-30 1997-12-16 Sumitomo Electric Industries, Ltd. Method of producing a silicon nitride based sintered body
US6124040A (en) * 1993-11-30 2000-09-26 Widia Gmbh Composite and process for the production thereof
DE4340652A1 (de) * 1993-11-30 1995-06-01 Krupp Widia Gmbh Verbundwerkstoff und Verfahren zu seiner Herstellung
DE4340652C2 (de) * 1993-11-30 2003-10-16 Widia Gmbh Verbundwerkstoff und Verfahren zu seiner Herstellung
WO1995026940A1 (fr) * 1994-03-31 1995-10-12 Westaim Technologies Inc. Procede de frittage par micro-ondes
US5736092A (en) * 1994-03-31 1998-04-07 Microwear Corporation Microwave sintering process
US5808282A (en) * 1994-03-31 1998-09-15 Microwear Corporation Microwave sintering process
US5874377A (en) * 1994-03-31 1999-02-23 Microwear Corporation Sintered silicon nitride product
RU2313508C2 (ru) * 2002-07-19 2007-12-27 Фита Цанфабрик Х.Раутер Гмбх Энд Ко. Кг Способ уплотнения керамических материалов под воздействием сантиметровых электромагнитных волн и сосуд для осуществления этого способа
EP1803329A4 (fr) * 2004-09-15 2011-08-03 Penn State Res Found Procede et appareil de synthese de phosphores par micro-ondes
EP2006267A4 (fr) * 2006-03-29 2009-09-02 Tokuyama Corp Procede et element de jonction de ceramique
WO2008077224A3 (fr) * 2006-12-27 2008-08-14 Fundacao Universidade Fed De S Compositions pour suscepteurs externes et suscepteurs externes destinés au frittage de céramiques par micro-ondes
US20130320001A1 (en) * 2012-06-04 2013-12-05 Denso Corporation Low-oxygen atmosphere apparatus
US9642193B2 (en) * 2012-06-04 2017-05-02 Denso Corporation Low-oxygen atmosphere apparatus
WO2018077735A1 (fr) * 2016-10-28 2018-05-03 Centre National De La Recherche Scientifique Procede de traitement thermique d'une piece en materiau ceramique par micro-ondes
FR3058138A1 (fr) * 2016-10-28 2018-05-04 Centre National De La Recherche Scientifique Procede de traitement thermique d’une piece en materiau ceramique par micro-ondes
US11713280B2 (en) 2016-10-28 2023-08-01 Centre National De La Recherche Scientifique Method for thermal treatment of a ceramic part by microwaves

Also Published As

Publication number Publication date
CN1054579A (zh) 1991-09-18
CA2001062A1 (fr) 1991-04-19
EP0495850A1 (fr) 1992-07-29
JP2628104B2 (ja) 1997-07-09
AU6540090A (en) 1991-05-16
JPH05500940A (ja) 1993-02-25

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