CN116553922A - Magnesia-alumina spinel transparent ceramic and preparation method thereof - Google Patents
Magnesia-alumina spinel transparent ceramic and preparation method thereof Download PDFInfo
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- 239000000919 ceramic Substances 0.000 title claims abstract description 83
- 229910052596 spinel Inorganic materials 0.000 title claims abstract description 70
- 239000011029 spinel Substances 0.000 title claims abstract description 70
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 title claims abstract description 54
- 238000002360 preparation method Methods 0.000 title claims abstract description 22
- 238000005245 sintering Methods 0.000 claims abstract description 83
- 239000000843 powder Substances 0.000 claims abstract description 31
- 235000015895 biscuits Nutrition 0.000 claims abstract description 21
- 238000001513 hot isostatic pressing Methods 0.000 claims abstract description 21
- 238000001354 calcination Methods 0.000 claims abstract description 18
- 239000002994 raw material Substances 0.000 claims abstract description 15
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 12
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 11
- 239000002002 slurry Substances 0.000 claims abstract description 9
- 238000001035 drying Methods 0.000 claims abstract description 7
- 238000007873 sieving Methods 0.000 claims abstract description 7
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 claims abstract description 5
- 238000003825 pressing Methods 0.000 claims abstract description 5
- 238000002156 mixing Methods 0.000 claims abstract description 4
- 238000000034 method Methods 0.000 claims description 34
- 238000002834 transmittance Methods 0.000 claims description 28
- 239000012298 atmosphere Substances 0.000 claims description 12
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 6
- 238000009694 cold isostatic pressing Methods 0.000 claims description 6
- 238000000465 moulding Methods 0.000 claims description 6
- 239000011164 primary particle Substances 0.000 claims description 6
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- 239000012300 argon atmosphere Substances 0.000 claims description 2
- 239000000463 material Substances 0.000 claims description 2
- 239000011148 porous material Substances 0.000 description 14
- 230000000052 comparative effect Effects 0.000 description 11
- 230000003287 optical effect Effects 0.000 description 11
- 238000000280 densification Methods 0.000 description 10
- 238000000498 ball milling Methods 0.000 description 7
- 239000012071 phase Substances 0.000 description 7
- 229910052749 magnesium Inorganic materials 0.000 description 6
- 239000011777 magnesium Substances 0.000 description 6
- -1 magnesium aluminate Chemical class 0.000 description 6
- 229910010293 ceramic material Inorganic materials 0.000 description 5
- 239000013078 crystal Substances 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 4
- 230000008030 elimination Effects 0.000 description 4
- 238000003379 elimination reaction Methods 0.000 description 4
- 239000012752 auxiliary agent Substances 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 238000005498 polishing Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000002612 dispersion medium Substances 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 description 2
- 239000000395 magnesium oxide Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000004626 scanning electron microscopy Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229910016569 AlF 3 Inorganic materials 0.000 description 1
- 229910021193 La 2 O 3 Inorganic materials 0.000 description 1
- 229910018068 Li 2 O Inorganic materials 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 239000004566 building material Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 150000004820 halides Chemical class 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000011858 nanopowder Substances 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000001272 pressureless sintering Methods 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 238000003746 solid phase reaction Methods 0.000 description 1
- 238000004611 spectroscopical analysis Methods 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- 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
- C04B35/44—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 aluminates
- C04B35/443—Magnesium aluminate spinel
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- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
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- 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
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- 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
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- C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
- C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
- C04B2235/30—Constituents and secondary phases not being of a fibrous nature
- C04B2235/44—Metal salt constituents or additives chosen for the nature of the anions, e.g. hydrides or acetylacetonate
- C04B2235/444—Halide containing anions, e.g. bromide, iodate, chlorite
- C04B2235/445—Fluoride containing anions, e.g. fluosilicate
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- C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
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- C04B2235/77—Density
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- C04B2235/70—Aspects relating to sintered or melt-casted ceramic products
- C04B2235/96—Properties of ceramic products, e.g. mechanical properties such as strength, toughness, wear resistance
- C04B2235/9646—Optical properties
- C04B2235/9653—Translucent or transparent ceramics other than alumina
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Abstract
The invention relates to magnesia-alumina spinel transparent ceramic and a preparation method thereof. The preparation method of the magnesia-alumina spinel transparent ceramic comprises the following steps: mixing Xiang Mei aluminum spinel powder and sintering aid to obtain ceramic slurry, drying, sieving and calcining the ceramic slurry to obtain raw material powder; pressing and forming the raw material powder to obtain a ceramic biscuit; calcining the ceramic biscuit in sequence, and presintering under no pressure to obtain a presintered body; after the presintered body is sintered by hot isostatic pressing, the magnesia-alumina spinel transparent ceramic is obtained; the sintering aid is at least one of fluoride or oxyfluoride containing Y, la and Lu, preferably YF 3 Or YOF.
Description
Technical Field
The invention belongs to the technical field of ceramic material preparation, and particularly relates to magnesia-alumina spinel transparent ceramic and a preparation method thereof.
Background
Magnesia-alumina spinel (MgAl) 2 O 4 ) Ceramic is an excellent transparent ceramic material having good light transmittance in the 0.19-5.5 μm band range. In addition, the magnesia-alumina spinel transparent ceramic also has good thermodynamic property and chemical corrosion resistance. These excellent properties enable the magnesium aluminate spinel transparent ceramics to be widely used in the fields of armor, infrared windows, lenses, chemical reactor windows, sensors, building materials, and the like.
From 1961 the United states general electric company with Li 2 O and SiO 2 After preparing translucent magnesia-alumina spinel ceramics as sintering aids by a solid phase reaction method, scientific researchers all around the world have shown great interest in magnesia-alumina spinel transparent ceramics and have made a great deal of researches on the preparation and sintering mechanism thereof. Magnesia alumina spinel has very low O 2- Diffusion rate, a property that makes densification difficult during sintering. To solve this problem, researchers have proposed many methods in which the addition of a sintering aid as a simple and effective method has attracted a great deal of attention. At present, many scientific research institutions explore the influence of different sintering aids on the performance of magnesia-alumina spinel transparent ceramics, such as halide sintering aid LiF, naF, mgF 2 、AlF 3 、KF、NaCl、KCl、LiCl、AlCl 3 、MgCl 2 The method comprises the steps of carrying out a first treatment on the surface of the Oxide sintering aid La 2 O 3 、CaO、Y 2 O 3 、B 2 O 3 Etc.
LiF is the most commonly used sintering aid for preparing high-quality magnesia-alumina spinel transparent ceramics, but the addition of LiF aids is easy to cause coarsening of crystal grains and microcracking of crystal boundaries, thereby seriously affecting the mechanical property and optical quality of ceramic samples. Therefore, there is an urgent need to explore new sintering aid systems capable of replacing LiF, which are required to be capable of improving densification rate of magnesia-alumina spinel ceramics and guaranteeing optical quality thereof.
Disclosure of Invention
In view of the above problems, an object of the present invention is to provide a method for preparing magnesia-alumina spinel transparent ceramics. The preparation method is simple in preparation process and high in repeatability, and the obtained magnesia-alumina spinel transparent ceramic has excellent optical quality in the visible-near infrared band.
In particular, in a first aspect, the invention provides a method for preparing magnesia-alumina spinel transparent ceramics, which comprises the following steps: mixing Xiang Mei aluminum spinel powder and sintering aid to obtain ceramic slurry, drying, sieving and calcining the ceramic slurry to obtain raw material powder;
pressing and forming the raw material powder to obtain a ceramic biscuit;
calcining the ceramic biscuit in sequence, and presintering under no pressure to obtain a presintered body; after the presintered body is sintered by hot isostatic pressing, the magnesia-alumina spinel transparent ceramic is obtained;
the sintering aid is at least one of fluoride or oxyfluoride containing Y, la and Lu, preferably YF 3 Or YOF.
Preferably, the total addition amount of the sintering aid is 0.005wt.% to 0.08wt.%, preferably 0.005wt.% to 0.05wt.% based on the mass of Xiang Mei aluminum spinel powder; when the sintering aid is YF 3 When the amount added is more preferably 0.005wt.% to 0.02wt.%; when the sintering aid is YOF, the addition amount is more preferably 0.005wt.% to 0.02wt.%.
Preferably, the purity of the Xiang Mei aluminum spinel powder is more than or equal to 99.9%, and the primary particle size is 20-200 nm; the purity of the sintering auxiliary powder is more than or equal to 99.9%, and the primary particle size is 20 nm-3000 nm.
Preferably, the press forming method is dry press forming or/and cold isostatic forming, and preferably dry press forming and then cold isostatic forming are performed.
Preferably, the dry press molding process conditions are as follows: using pressure of 5-30 MPa, and keeping the pressure for 1-3 minutes; the technological conditions of cold isostatic pressing are as follows: the pressure of 150-250 MPa is used, and the pressure is kept for 3-20 minutes.
Preferably, the calcination temperature of the biscuit is 600-900 ℃ and the calcination time is 4-10 hours.
Preferably, the pressureless presintering temperature is 1300-1600 ℃, the pressureless presintering time is 1-10 hours, and the atmosphere is air atmosphere or vacuum.
Preferably, the relative density of the presintered body obtained after pressureless presintering is 90 to 99%.
Preferably, the sintering temperature of the hot isostatic pressing is 1400-1900 ℃, the sintering time is 1-6 hours, and the sintering pressure is 100-250 MPa; the atmosphere used is an inert atmosphere, preferably a nitrogen or/and argon atmosphere.
In a second aspect, the invention provides the magnesia-alumina spinel transparent ceramic obtained by the preparation method, and the linear transmittance of the magnesia-alumina spinel transparent ceramic in the wavelength range of 400 nm-2500 nm is more than or equal to 78.9% when the thickness is more than or equal to 4 mm.
Advantageous effects
1) Compared with the existing preparation technology of the magnesia-alumina spinel transparent ceramic, the sintering aid selected by the invention can effectively promote the sintering densification of the magnesia-alumina spinel ceramic, is enriched with a grain boundary, plays a role in pinning, inhibits the growth of grains and accelerates the elimination of air holes; the obtained magnesia-alumina spinel transparent ceramic has uniform grain size and no obvious air holes, the sample has high optical quality, the linear transmittance in the wavelength range of 400 nm-2500 nm is more than or equal to 78.9% when the thickness is more than or equal to 4mm, and compared with the sample without sintering auxiliary agent, the transmittance is obviously improved;
2) The preparation method provided by the invention adopts the technology of pressureless sintering and hot isostatic pressing treatment, is simple and easy to operate, has lower presintering temperature and hot isostatic pressing temperature, and can be used for mass production with lower cost under the prior art condition.
Drawings
FIG. 1 is a photograph of a transparent magnesia-alumina spinel ceramic sample prepared in example 1 after double-sided polishing;
FIG. 2 is a graph showing the linear transmittance of the magnesia-alumina spinel transparent ceramic samples prepared in example 1;
FIG. 3 is a graph showing the linear transmittance of the magnesia-alumina spinel transparent ceramic samples prepared in example 2;
FIG. 4 is a photograph of transparent magnesia-alumina spinel ceramic samples prepared in example 3 with various YOF sintering aids added;
FIG. 5 is a graph showing the comparison of the linear transmittance curves of magnesia-alumina spinel transparent ceramic samples prepared in example 3 and containing different levels of YOF sintering aids;
FIG. 6 is a photograph of transparent magnesia-alumina spinel ceramic samples prepared in example 4 with varying levels of YOF sintering aid added;
FIG. 7 is a graph showing the comparison of the linear transmittance curves of magnesia-alumina spinel transparent ceramic samples prepared in example 4 and containing different levels of YOF sintering aids;
FIG. 8 is a photograph of a magnesia-alumina spinel ceramic sample prepared in comparative example 1, which has been double-sided polished;
FIG. 9 is a photograph of a transparent ceramic sample of magnesia-alumina spinel prepared in comparative example 2, which has been double-sided polished;
FIG. 10 is a back-scattered image and a surface scanning element distribution diagram of a transparent magnesium aluminate spinel ceramic sample prepared in comparative example 2.
Detailed Description
The present invention is further illustrated by the following embodiments, which are to be understood as merely illustrative of the invention and not limiting thereof.
The following illustrates a preparation method of the magnesia-alumina spinel transparent ceramic provided by the invention, which mainly comprises the following steps: preparing raw material powder, forming and sintering densification.
(1) And (3) preparing raw material powder. Ball-milling and mixing the Xiang Mei aluminum spinel powder and the sintering aid uniformly to obtain ceramic slurry, wherein the grinding balls can be alumina balls, the dispersion medium can be absolute ethyl alcohol, and the mass ratio of the balls can be 5:1, a step of; and drying, sieving and calcining the ceramic slurry to obtain raw material powder.
In some embodiments, the sintering aid may be at least one of a fluoride or oxyfluoride containing Y, la, lu, preferably YF 3 Or YOF. The total addition amount of the sintering aid may be 0.005wt.% to 0.08wt.%, preferably 0.005wt.% to 0.05wt.% based on the mass of Xiang Mei aluminum spinel powder; when the sintering aid is YF 3 When the amount added is more preferably 0.005wt.% to 0.02wt.%; when the sintering aid is YOF, the addition amount is more excellentSelected to be 0.005wt.% to 0.02wt.%. The addition amount of the sintering aid is too low, so that the densification rate of the material in the subsequent sintering process is reduced, the elimination of air holes is not facilitated, and the transmittance of the prepared ceramic sample is reduced or even is not transparent; the addition of the sintering aid is too high, which is prone to precipitation of a second phase during sintering and also affects the optical properties of the transparent ceramic sample.
The purity of the Xiang Mei aluminum spinel powder is more than or equal to 99.9%, and the primary particle size is 20 nm-200 nm; the purity of the sintering auxiliary powder is more than or equal to 99.9%, and the primary particle size is 20 nm-3000 nm. The smaller the particle size of the powder, the higher the sintering activity, but the too low particle size is easy to agglomerate, which is not beneficial to the removal of gas in the sintering process, and the residual air holes can influence the transmittance of the ceramic material sample; if the particle size is too large, the sintering activity is reduced, and the preparation difficulty is high.
YOF, YF employed in the present invention 3 The sintering aid can form pinning effect at the grain boundary, inhibit grain growth and accelerate the elimination of air holes. Under the sintering condition, the fluoride or oxyfluoride sintering auxiliary agent can promote sintering densification in a liquid-phase sintering promotion mode, and the elimination of air holes is accelerated.
The ball milling process can be as follows: ball milling for 3-12 hours at the rotating speed of 250 rpm; the drying conditions may be: drying at 50-80 deg.c for 12-48 hr; the screen mesh used for sieving can be 80-200 mesh. The organic impurities introduced during the ball milling and sieving process are removed by the calcination, and the calcination process can be as follows: preserving the heat in a muffle furnace for 4 to 12 hours at the temperature of 500 to 900 ℃.
(2) And (5) molding. And (3) pressing and forming the raw material powder prepared in the step (1) to obtain a ceramic biscuit.
The forming method can be dry press forming or/and cold isostatic pressing, and is preferably dry press forming and then cold isostatic pressing. Specifically, the calcined raw material powder is put into a mold, and the dry-press molding process conditions can be as follows: using pressure of 5-30 MPa, and keeping the pressure for 1-3 minutes; the process conditions of cold isostatic pressing may be: the pressure of 150-250 MPa is used, and the pressure is kept for 3-20 minutes.
(3) And (5) sintering densification. Calcining the biscuit molded in the step (2) in sequence, and presintering the biscuit under no pressure to obtain a presintered body, so that open pores of the biscuit are closed; and (3) after sintering the presintered body by hot isostatic pressing, polishing the two sides of the presintered body to obtain the magnesia-alumina spinel transparent ceramic.
Organic impurities introduced during the molding process can be removed by biscuit calcination. In some embodiments, the temperature of the biscuit calcination may be 600 ℃ to 900 ℃ and the calcination time may be 4 to 10 hours; the pressureless presintering temperature can be 1300-1600 ℃, the pressureless presintering time can be 1-10 hours, and the used atmosphere can be air atmosphere or vacuum.
After the biscuit is calcined and pressureless presintering treatment, a presintered body with 90-99% relative density and closed open pores can be obtained. Subsequent HIP sintering generally does not eliminate open pores in large amounts, but residual pores can severely affect the transmittance of the transparent ceramic sample. Therefore, reasonable control of the presintering conditions can ensure that ceramic samples with good transmittance are obtained in the subsequent hot isostatic pressing sintering process.
The principle of removing residual air holes by combining the hot isostatic pressing sintering is known that for a sample presintered at a low temperature (low relative density), the air holes in the presintered body are mainly positioned at crystal boundaries and have a small content, and are easy to remove in the hot isostatic pressing sintering process. However, when the burn-in temperature is relatively high (high relative density), part of the pores in the burn-in body will enter the inside of the crystal grains to form intra-crystal pores, and the content of the pores is relatively high, and such pores often need to be sintered by high-temperature and high-pressure hot isostatic pressing to provide enough energy to remove the pores, and the removal effect is poor. In addition, high temperature pre-sintering (which results in high relative density) tends to cause the growth of pores inside the sample, forming large pores with high coordination number, thereby impeding the later densification process. Therefore, the transmittance of the ceramic material sample obtained after the high temperature pre-sintered sample (high relative density) is generally low. The technical scheme provided by the invention realizes successful preparation of the ceramic material with higher optical quality by reasonably controlling the presintering system and selecting proper relative density.
In some embodiments, the hot isostatic pressing sintering temperature may be 1400-1900 ℃ and the sintering time may be 1-6 hours; the sintering pressure can be 100-250 MPa; the atmosphere used may be an inert gas, preferably nitrogen or/and argon. The sintering temperature of the hot isostatic pressing is too low, which is not beneficial to the removal of residual air holes, influences the transmittance of a sample, and the ceramic sample cannot be transparent; the sintering temperature of the hot isostatic pressing is too high, and the sintering aid is easy to precipitate in the form of a second phase, so that the transmittance of the ceramic sample is affected.
The hot isostatic pressing sintering can eliminate residual pores in the ceramic and heal defects, but the ceramic before treatment does not contain open pores basically, so that the green body after the pressureless presintering treatment needs to reach 90-99% of relative density.
The invention takes high-purity commercial magnesia-alumina spinel nano powder as a raw material, promotes densification and air hole removal by adding a sintering aid, and prepares magnesia-alumina spinel transparent ceramic by adopting a pressureless presintering and hot isostatic pressing sintering combined mode, thereby having higher optical quality. The magnesia-alumina spinel transparent ceramic has good optical performance in the visible-near infrared light wavelength range: when the thickness is more than or equal to 4mm, the linear transmittance in the wavelength range of 400 nm-2500 nm is more than or equal to 78.9 percent.
The present invention will be further illustrated by the following examples. It should also be understood that the following examples are given by way of illustration only and are not to be construed as limiting the scope of the invention, since numerous insubstantial modifications and adaptations of the invention to those skilled in the art will now be apparent to those in light of the foregoing disclosure, and that the specific process parameters and the like set forth below are merely one example of a suitable scope.
Example 1
(1) And (3) preparing raw material powder. Based on the total mass (60 g) of Xiang Mei aluminum spinel powder as 100wt.%, 0.01wt.% (0.006 g) of YOF auxiliary agent is added, absolute ethyl alcohol is used as a dispersion medium, high-purity aluminum oxide balls are used as ball milling media, and the ball mass ratio is controlled to be 5:1, ball milling is carried out by using a planetary ball mill, the rotating speed is 250 revolutions per minute, and the ball milling time is 12 hours. And (3) placing the ball-milled slurry in a 65 ℃ oven for drying for 12 hours, sieving the dried powder with a 100-mesh sieve, placing the sieved powder in a muffle furnace for calcining for 6 hours at 800 ℃ to obtain raw material powder.
(2) And (5) molding. And forming the calcined raw material powder by using a method of combining dry pressing with cold isostatic pressing to obtain the magnesia-alumina spinel ceramic biscuit. Wherein the dry pressure is 10MPa, and the pressure is maintained for 2 minutes; the static pressure is 200MPa, and the pressure is maintained for 3 minutes.
(3) And (5) sintering densification. Calcining the formed biscuit in a muffle furnace at 800 ℃ for 6 hours; then presintering for 6 hours in an air atmosphere at 1470 ℃ under no pressure to obtain a presintered body with 94.70% of relative density and closed open pores; and (3) carrying out hot isostatic pressing treatment on the presintered body for 3 hours under the pressure of 200MPa and the temperature of 1550 ℃ to obtain the magnesia-alumina spinel transparent ceramic sample.
FIG. 1 is a photograph of a transparent magnesium aluminate spinel ceramic sample prepared in example 1 after double-sided polishing. As can be seen from the figure, the transparent magnesia-alumina spinel ceramic sample prepared in example 1 has high transparency.
FIG. 2 is a graph showing the linear transmittance of the magnesia-alumina spinel transparent ceramic samples prepared in example 1. The sample was 4mm thick. As can be seen from fig. 2, the magnesium aluminate spinel transparent ceramic sample to which 0.01wt.% YOF was added had a linear transmittance of 82.60% at 400nm and 87.30% at 1100nm, and the sample had excellent optical quality.
Example 2
The preparation flow of this example is referred to in example 1. The main differences are that: in step (1), 0.03wt.% YF is added 3 As a sintering aid; in the step (3), the pressureless presintering temperature of the molded biscuit is 1480 ℃.
FIG. 3 is a graph showing the linear transmittance of the magnesia-alumina spinel transparent ceramic samples prepared in example 2. The sample was double-side polished to a thickness of 4 mm. As can be seen from fig. 3, the sample has a high transmittance, 86.1% at 1100nm, approaching the theoretical transmittance; the transmittance at 400nm was 78.9%.
Example 3
The preparation flow of this example is referred to in example 1. The main differences are that: in the step (1), YOF of 0.005wt.% and YOF of 0.01wt.% are added as sintering aids, respectively; in the step (3), the pressureless presintering temperature of the molded biscuit is 1480 ℃ and the hot isostatic pressing temperature is 1600 ℃.
FIG. 4 is a photograph of transparent magnesia-alumina spinel ceramic samples prepared in example 3 with varying levels of YOF sintering aid. All samples were double-sided polished to a thickness of 4 mm.
FIG. 5 is a graph showing the comparison of the linear transmittance curves of magnesia-alumina spinel transparent ceramic samples prepared in example 3 and containing different levels of YOF sintering aids. As can be seen from FIG. 5, the samples have high transmittance, and the transmittance at 400nm is 82.0% and 80.8%, respectively.
Example 4
The preparation flow of this example is referred to in example 1. The main differences are that: in step (1), YOF was added as a sintering aid in an amount of 0.005wt.%, 0.01wt.%, and 0.05wt.%, respectively; in the step (3), the pressureless presintering temperature of the molded biscuit is 1480 ℃ and the hot isostatic pressing temperature is 1550 ℃.
FIG. 6 is a photograph of transparent magnesia-alumina spinel ceramic samples prepared in example 4 with varying levels of YOF sintering aid. All samples were double-sided polished to a thickness of 4 mm.
FIG. 7 is a graph showing the comparison of the linear transmittance curves of magnesia-alumina spinel transparent ceramic samples prepared in example 4 and containing different levels of YOF sintering aids. All samples were double-sided polished to a thickness of 4 mm. As can be seen from fig. 7, the transmittance at 400nm of the magnesium aluminate spinel transparent ceramic samples with 0.005wt.%, 0.01wt.%, and 0.05wt.% YOF promoter added was 79.9%, 80.2%, 81.6%, respectively.
Comparative example 1
The preparation procedure of this comparative example is referred to in example 1. The main differences are that: in the step (1), no sintering aid is added; in the step (3), the pressureless presintering temperature of the molded biscuit is 1470 ℃ and 1480 ℃, and the hot isostatic pressing temperature is 1550 ℃ and 1600 ℃.
FIG. 8 is a photograph of a magnesia-alumina spinel ceramic sample prepared in comparative example 1, which has been double-side polished. As can be seen from the figures, all four samples were opaque magnesia alumina spinel ceramics.
Comparative example 2
The preparation procedure of this comparative example is referred to in example 1. The main differences are that: in step (1), 0.1wt.% YOF is added as sintering aid.
FIG. 9 is a photograph of a transparent ceramic sample of magnesia-alumina spinel prepared in comparative example 2, which has been double-sided polished. As can be seen from the figure, the ceramic sample has poor optical quality. To demonstrate that too high a content of sintering aid precipitates out the second phase affecting the optical quality of the ceramic samples, the samples in this comparative example were analyzed using Scanning Electron Microscopy (SEM) and energy spectroscopy (EDS). FIG. 10 is a back-scattered image and a surface scanning element distribution diagram of a transparent magnesium aluminate spinel ceramic sample prepared in comparative example 2. As can be seen from the SEM pictures, there is a distinct second phase precipitation at the grain boundaries, and the grain size of the second phase is about 0.44 μm; the EDS face scan element distribution shows that Al, mg, O are uniformly distributed and only Y element is enriched at the second phase location, so the second phase is created by the introduction of the promoter.
While the present invention has been described in detail through the foregoing description of the preferred embodiment, it should be understood that the foregoing description is not to be considered as limiting the invention. Many modifications and substitutions of the present invention will become apparent to those of ordinary skill in the art upon reading the foregoing. Accordingly, the scope of the invention should be limited only by the attached claims.
Claims (10)
1. A method for preparing magnesia-alumina spinel transparent ceramics, which is characterized by comprising the following steps:
mixing Xiang Mei aluminum spinel powder and sintering aid to obtain ceramic slurry, drying, sieving and calcining the ceramic slurry to obtain raw material powder;
pressing and forming the raw material powder to obtain a ceramic biscuit;
calcining the ceramic biscuit in sequence, and presintering under no pressure to obtain a presintered body; after the presintered body is sintered by hot isostatic pressing, the magnesia-alumina spinel transparent ceramic is obtained;
the sintering aid is a material containingAt least one of fluoride or oxyfluoride of Y, la, lu, preferably YF 3 Or YOF.
2. The method of claim 1, wherein the total addition of sintering aid is 0.005wt to 0.08 wt%, preferably 0.005wt to 0.05 wt% by mass of Xiang Mei aluminum spinel powder; when the sintering aid is YF 3 When the amount added is more preferably 0.005wt.% to 0.02wt.%; when the sintering aid is YOF, the addition amount is more preferably 0.005-wt% to 0.02-wt%.
3. The preparation method according to claim 1 or 2, wherein the purity of the Xiang Mei aluminum spinel powder is more than or equal to 99.9%, and the primary particle size is 20 nm-200 nm; the purity of the sintering auxiliary powder is more than or equal to 99.9%, and the primary particle size is 20 nm-3000 nm.
4. A method according to any of claims 1-3, characterized in that the press forming method is dry press forming or/and cold isostatic forming, preferably dry press forming followed by cold isostatic forming.
5. The method according to any one of claims 1 to 4, wherein the dry press molding process conditions are: using pressure of 5-30 MPa, and keeping the pressure for 1-3 minutes; the technological conditions of cold isostatic pressing are as follows: the pressure of 150-250 MPa is used, and the pressure is kept for 3-20 minutes.
6. The process according to any one of claims 1 to 5, wherein the biscuit is calcined at a temperature of 600 ℃ to 900 ℃ for a calcination time of 4 to 10 hours.
7. The method according to any one of claims 1 to 6, wherein the pressureless presintering temperature is 1300 ℃ to 1600 ℃ and the pressureless presintering time is 1 to 10 hours, and the atmosphere is an air atmosphere or a vacuum.
8. The method according to any one of claims 1 to 7, wherein the relative density of the pre-sintered body obtained after pressureless pre-sintering is 90 to 99%.
9. The method according to any one of claims 1 to 8, wherein the hot isostatic pressing sintering temperature is 1400 ℃ to 1900 ℃, the sintering time is 1 to 6 hours, and the sintering pressure is 100 to 250MPa; the atmosphere used is an inert atmosphere, preferably a nitrogen or/and argon atmosphere.
10. The transparent magnesia-alumina spinel ceramic obtained by the preparation method according to claim 1, wherein the linear transmittance of the transparent magnesia-alumina spinel ceramic in the wavelength range of 400 nm-2500 nm is more than or equal to 78.9% when the thickness is more than or equal to 4 mm.
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