CN108546093B - Alumina short fiber reinforced magnesium oxide base crucible and preparation method thereof - Google Patents

Alumina short fiber reinforced magnesium oxide base crucible and preparation method thereof Download PDF

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CN108546093B
CN108546093B CN201810306499.7A CN201810306499A CN108546093B CN 108546093 B CN108546093 B CN 108546093B CN 201810306499 A CN201810306499 A CN 201810306499A CN 108546093 B CN108546093 B CN 108546093B
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crucible
magnesia
short fiber
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alumina
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CN108546093A (en
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刘子利
刘希琴
叶兵
刘思雨
丁之光
丁文江
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Fengyang L S Light Alloy Net Forming Co ltd
Nanjing University of Aeronautics and Astronautics
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Fengyang L S Light Alloy Net Forming Co ltd
Nanjing University of Aeronautics and Astronautics
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Abstract

The invention discloses an alumina short fiber reinforced magnesia-based crucible which can realize sintering at low temperature and has excellent chemical stability and thermal shock resistance and a preparation method thereof, wherein the method comprises the following steps: (1) preparing 15-25% of nano aluminum sol, 0.8-1.5% of rheological agent and the balance of electric melting magnesia ceramic powder containing nano lanthanum oxide and alumina short fibers according to the mass percentage, adding a proper amount of deionized water, performing ball milling and uniform mixing, and then performing vacuum exhaust to prepare ceramic slurry with the solid content of 70-80%; (2) preparing a crucible biscuit; (3) preparing a crucible blank; (4) and (2) carrying out vacuum infiltration treatment on the magnesium oxide base crucible blank in alumina sol, then carrying out surface polishing treatment, drying, carrying out high-temperature secondary sintering at the temperature of 1400-1600 ℃, and cooling to room temperature along with the furnace to obtain the magnesium oxide base crucible.

Description

Alumina short fiber reinforced magnesium oxide base crucible and preparation method thereof
Technical Field
The invention relates to a magnesium oxide-based crucible and a preparation method thereof, in particular to an aluminum oxide short fiber reinforced magnesium oxide-based crucible and a preparation method thereof, belonging to the field of metal materials and metallurgy. The magnesium oxide-based crucible prepared by the invention is particularly suitable for smelting magnesium and magnesium alloy.
Background
In recent years, the demand for light weight has led to rapid development of applications of magnesium alloys and aluminum alloys, and the production of both wrought magnesium alloys and cast magnesium alloys and aluminum alloys cannot be separated from casting equipment. Magnesium is active in chemical property, is easy to react with oxygen, nitrogen and water vapor, is easy to oxidize and burn during melting and refining, and the generated products remain in magnesium to deteriorate the internal quality and performance of products. For aluminum alloy, except large-scale manufacturing enterprises which adopt large-scale reverberatory furnaces, crucible furnaces are still the main equipment for casting aluminum alloy in small and medium-scale casting enterprises.
The crucible is the key for determining the smelting quality of the crucible furnace, and the metal casting crucible applied in industry mainly comprises an iron crucible (such as cast iron and stainless steel) and a non-metal crucible. Iron crucibles (carbon steel, stainless steel, etc.) are commonly used for casting magnesium and aluminum alloy at present, but molten alloy liquid and liquid flux easily corrode the crucibles during heating to reduce the service life of the crucibles, and iron easily enters the molten alloy liquid to pollute the alloy. Among the non-metallic crucibles, the graphite crucible is low in strength, the crucible is easily broken when it is not operated properly or heated unevenly, and the thermal conductivity is remarkably decreased after a long time, and therefore, the graphite crucible is rarely used at present.
The application of the ceramic crucible greatly promotes the development of the metallurgical industry, particularly the special smelting of nuclear materials. The magnesium alloy is smelted by adopting a ceramic crucible or a potteryThe ceramic lining can prevent iron crucible from mixing harmful elements such as Fe, Cu, Cr and the like in the casting process of magnesium alloy to the maximum extent, and improve the corrosion resistance of magnesium alloy products. Although the smelting temperature of the magnesium alloy is not high (similar to that of the aluminum alloy, about 700 ℃), the chemical property of the magnesium alloy is very active, the standard free enthalpy of MgO generation is very low, the magnesium alloy is very easy to oxidize in the smelting process, the generated loose magnesium oxide can not provide protection for a melt, and the generated heat can accelerate oxidation combustion; on the other hand, the vapor pressure of magnesium is quite high (1037 Pa at 727 ℃), magnesium alloy liquid and vapor are very easy to permeate into the porous ceramic material and react with the porous ceramic material, the physical properties of a reaction product, such as thermal expansion coefficient, elastic modulus and the like, are different from those of a ceramic matrix, stress is easily generated to lead the reaction product to fall off from the ceramic matrix, so that the ceramic is deteriorated, the structure is loose, the reaction product is damaged and alloy melt is polluted, for example, the magnesium melt with high activity is very easy to be compared with Al which is widely used at present2O3,ZrO2,SiC、SiO2The ceramic matrix crucible material undergoes the reactions of the formulas (1) to (4) to rapidly damage and pollute magnesium alloy melt, so the ceramic material for smelting the magnesium alloy is more strict, and the existing Al2O3,ZrO2,SiC、SiO2The ceramic crucible is not suitable for casting magnesium and magnesium alloy, and the related reports about the ceramic material for smelting magnesium alloy are less.
3Mg(l)+Al2O3(s)=3MgO(s)+2Al(l) (1)
2Mg(l)+ZrO2(s)=2MgO(s)+Zr(s) (2)
6Mg(l)+4Al(l)+3SiC(s)=3Mg2Si(s)+Al4C3(s) (3)
4Mg(l)+SiO2(s)=2MgO(s)+Mg2Si(s) (4)
MgO is a cubic NaCl type structure with a lattice constant of 0.411nm, belongs to an ionic bond compound, has a melting point of 2852 ℃, and is much higher than that of common Al2O3(2054 ℃ C.) and SiO2(1650 +/-50 ℃), so that the magnesium oxide product has good chemical stability, high resistivity and strong metal, slag and alkaline solutionResistance to erosion, etc. Compared with the common ceramic material, MgO, magnesium and alloy melt thereof have good high-temperature chemical stability, the use temperature of the MgO, magnesium and alloy melt is as high as 1600-1850 ℃, the MgO, magnesium and alloy melt do not react with flux inclusion consisting of molten chloride and fluonate, and the MgO and flux inclusion have smaller wetting angle and are easy to absorb flux inclusion in the magnesium melt, so the MgO ceramic crucible is an ideal choice for smelting and purifying magnesium alloy liquid. Furthermore, dense MgO ceramics are also considered to be preferred smelting vessel materials for smelting high-purity iron and its alloys, and nickel, uranium, thorium, zinc, tin, aluminum and its alloys.
Firing below the melting point of the oxide composition is the most critical step necessary for the preparation of the ceramic material, and the sintering, grain growth, etc. that occurs at high temperatures determines the microstructure and properties of the ceramic material. The magnesium oxide ceramics prepared by pure magnesium oxide as raw material, such as Chinese patent document CN103030407B (a preparation method of high-strength, high-density and high-purity magnesium oxide crucible), Chinese patent document CN1011306B (pure magnesium oxide foam ceramic filter and preparation process thereof), etc., because MgO has very high melting point and thermal expansion coefficient (13.5 multiplied by 10)-6/° c), which results in difficulty in sintering (sintering temperature not lower than 0.8 times of its melting point) and poor thermal shock resistance, limiting the application and development of MgO ceramic.
The research shows that: the heat consumption of unit products can be reduced by more than 10 percent when the firing temperature is reduced by 100 ℃ in the ceramic sintering process, and the addition of the sintering aid is an important technical means for reducing the sintering temperature of the MgO ceramic. Addition of V2O5In the case of powder, MgO reacts with V at 1190 DEG C2O5Form an approximate composition of Mg3V2O8Can remarkably lower the sintering temperature of the MgO foamed ceramics, but V2O5Has damage to the respiratory system and the skin during the use process, and has strict limitation on the operation. And V2O5Similarly, cobalt oxide is a good low temperature sintering aid, but has limited application as a highly toxic substance and a scarce resource. Chinese patent documents CN100434390C (composition for making crucible and method thereof) and CN101785944B (for magnesium and magnesium)Fluorite (melting point 1423 ℃) and magnesium fluoride (melting point 1248 ℃) are added into the magnesia ceramic foam filter for melt filtration, and solid solution of fluoride in the sintering process not only increases lattice distortion of matrix magnesia, but also easily forms a low-melting-point liquid phase, thereby reducing the sintering temperature of the magnesia ceramic; however, F in fluoride is combined with Si, Al, Fe and Ca in the sintering process, most of the F (accounting for about 70 percent in the production of ceramic tiles) volatilizes in a gaseous state to erode a blank body and damage the quality of the sintered ceramic, more serious the F pollution is caused by the emission of the fluoride into the atmosphere, the fluoride can enter a human body through respiratory tract, digestive tract and skin, has toxic effect on the central nervous system and cardiac muscle, the low-concentration fluorine pollution can cause brittle calcification of teeth and bones, and the emission standard of the fluoride is required to be lower than 5.0mg/m in the emission standard of ceramic industrial pollutants (GB25464-2010)3The fluoride is used as the low-temperature sintering aid of the magnesium oxide ceramic, so that the emission of gaseous fluoride is increased inevitably, and the burden of environmental protection is increased; in addition, fluorine ions in solid-solution fluorides remaining in ceramics exist in the form of substituted oxygen ions, which causes a decrease in chemical stability of intergranular bonding, and makes it difficult to resist long-term erosion by flux in magnesium melt. In the slurry for preparing the ceramic foam filter disclosed in chinese patent document CN104496492B (a composite magnesia carbon refractory crucible and a method for preparing the same), silica sol and the like are used as a binder, and SiO (silicon dioxide) among sintered ceramic particles is used as a binder2The existence of the components makes the components easy to react with magnesium and magnesium alloy melt according to the formula (4), and the chemical stability of the ceramic is also reduced. In chinese patent documents CN100536986C (magnesia ceramic foam filter), CN103553686A (magnesium aluminate spinel ceramic foam filter and its preparation method), and the like, boron trioxide and borax are used as low temperature sintering aids for magnesia ceramics, and when the boron trioxide is higher than 450 ℃, it forms a liquid phase, and when the sintering temperature exceeds 1350 ℃, it reacts with magnesia to generate magnesium borate in the form of a liquid phase, thereby lowering the sintering temperature. However, boron trioxide is liable to react with magnesium and aluminum and is unstable in magnesium and aluminum alloy melts; meanwhile, as the diboron trioxide is dissolved in solvents such as water, ethanol and the like, the boric acid can be generated by absorbing water strongly in the airThe diboron trioxide added in the preparation process of the ceramic product is dissolved in water to form a boric acid aqueous solution, and the boric acid aqueous solution is easy to react with magnesium oxide to form magnesium borate precipitate so as to reduce the effect of the magnesium borate precipitate. Gallium oxide is a family oxide of diboron trioxide, and forms spinel-shaped MgGa with magnesium oxide at a lower temperature2O4But the sintering temperature is reduced, but the resource amount of gallium is very small (gallium is a strategic reserve metal), and the application of gallium oxide in common ceramics is limited due to the higher price of gallium oxide.
The production method of the ceramic crucible industry adopts a dry pressing method, and besides the small crucible, slip casting and isostatic pressing are two common preparation technologies. Although the isostatic pressing formed crucible has the advantages of high density and yield and difficult deformation of a crucible blank in the sintering process, the problems of high cost, low efficiency, poor thermal stability, easy cracking and peeling of the crucible in the rapid heating and cooling process, short service life and the like of the isostatic pressing formed crucible are found. The slip casting method is the most reasonable method for forming crucibles or other hollow products, and under the same conditions, the slip casting method can obtain green bodies with larger particle bulk density (more than 2000 kg/cm) than other forming methods3The article is also denser at the molding pressure) and the firing temperature required is also lower.
Disclosure of Invention
The invention aims to provide a preparation method of a spinel reinforced magnesia-based crucible which can realize sintering at low temperature and has excellent chemical stability and thermal shock resistance and is synthesized in situ by magnesia whiskers.
In order to achieve the technical purpose, the technical scheme of the invention is as follows:
an alumina short fiber reinforced magnesia-based crucible is characterized in that: the electric melting magnesia-based ceramic slurry containing the nano lanthanum oxide and the alumina short fiber is formed by slip casting in a gypsum mold, and is obtained by drying and sintering.
A preparation method of an alumina short fiber reinforced magnesia-based crucible comprises the following steps:
(1) according to the mass percentage, 15 to 25 percent of nano aluminum sol, 0.8 to 1.5 percent of rheological agent and the balance of electric melting magnesia ceramic powder containing nano lanthanum oxide and alumina short fiber are mixed, a proper amount of deionized water is added, the mixture is ball-milled and mixed evenly, and then the mixture is vacuum-exhausted to prepare ceramic slurry with the solid content of 70 to 80 percent.
The added nano aluminum sol forms gamma-Al on the surfaces of the magnesium oxide particles and the alumina short fibers with high uniform dispersion2O3Coating film of Al during sintering2O3Reacts with MgO in situ to generate magnesium aluminate spinel (MgAl)2O4MA) phase, which directly fuses together the cristobalite MgO grains.
The added nano aluminum sol can not only be added into the electric melting magnesium oxide particles and highly uniformly dispersed nano La2O3Forming gamma-Al on the surfaces of the powder and the alumina short fiber2O3Coating the film to act as a binder, Al during sintering2O3And La2O3React with MgO in situ to respectively generate MgAl with chemical stability to magnesium and alloy melt thereof2O4And MgLa2O4Spinel phase (La has a smaller electronegativity than Mg and Al, MgLa2O4Spinel phase chemical stability ratio MgAl2O4Higher), therefore, the spinel phase synthesized in situ in the crucible prepared by the invention directly fuses the cristobalite MgO grains together, the structure has good chemical stability in the magnesium melt, and the damage of the existing product added with silica sol, ethyl silicate and other binders to the chemical stability of the ceramic is avoided; meanwhile, the ceramic component does not contain sodium salt (for example, sodium carboxymethylcellulose is not adopted in the rheological agent), so that residual Na with larger ionic radius is avoided+The resistance to sintering of the ceramic.
The solid content of the nano aluminum sol is 20-25%.
The rheological agent is a mixture of polyvinyl alcohol and cellulose ether, wherein the polyvinyl alcohol accounts for 40% of the mass of the rheological agent, and the cellulose ether is one or a mixture of industrial hydroxyethyl cellulose and hydroxypropyl methyl cellulose;
the ceramic powder is a mixture of nano lanthanum oxide, alumina short fibers and electric melting magnesium oxide; what is needed isThe nano lanthanum oxide accounts for 1-3% of the mass of the ceramic powder, the alumina short fiber accounts for 1-3% of the mass of the ceramic powder, and the balance is fused magnesia. The particle size of the nano lanthanum oxide is 30-60 nm, and the aluminum oxide short fiber is commercial polycrystalline Al with small length-diameter ratio2O3Short fibers having a diameter of 10 to 20 μm and a length of 50 to 100 μm, wherein the fused magnesia powder has a particle size of 250 to 500 mesh (median diameter d)5058 μm).
The added nano lanthanum oxide reacts with the electric melting MgO to generate MgLa with excellent high-temperature stability2O4Spinel phase (melting point 2030 ℃ C.).
The nano alumina sol and the nano lanthanum oxide can be dissolved into the crystal lattice of MgO in a solid solution in the sintering process to enable the crystal lattice of MgO to be distorted, activate the crystal lattice, and generate a new compound MgAl through reaction sintering between the MgO particles2O4And MgLa2O4Spinel phase, thereby promoting sintering and grain-to-grain bonding. Nanopowder refers to the particle size<The 100nm superfine powder has the characteristics of large specific surface area, high surface energy, high activity and the like, so that the nanometer powder is easy to combine with other atoms, and the melting point and the sintering temperature of the nanometer powder are much lower than those of the superfine powder. The sintering aid added in the form of nano alumina sol and nano lanthanum oxide can fill gaps among the raw material micro powder particles, optimize ceramic particle gradation and mixing uniformity, and meanwhile, the nano powder has high-reactivity nano gamma-Al in the alumina sol due to the surface and interface effects of the nano powder2O3The nanometer lanthanum oxide and MgO particles are fully contacted, so that the reaction speed is rapidly improved, the sintering temperature is reduced, the density and the mechanical property of the ceramic are improved, and the reduction of the sintering temperature is beneficial to reducing the energy consumption and the production cost of the ceramic crucible.
The electro-melting magnesium oxide is selected, and has strong hydration resistance. The reaction sintering of magnesium oxide and aluminum oxide to form MA causes volume expansion (linear expansion rate of 2.3%, volume expansion rate of 6.9%) and increases the sintering load.
The mechanical property of the ceramic matrix composite material can be improved by adopting the fibers and the whiskers as the reinforcement. In the scheme provided by the inventionIn the process, the nano aluminum sol forms a continuous film on the surfaces of electric melting magnesium oxide particles and highly dispersed aluminum oxide short fibers, and reacts with MgO in situ in the sintering process to generate a magnesium aluminate spinel MA phase, and the MA directly melts and connects cristobalite MgO grains together. There is little O during MA formation2-Diffusion of ions, but only Mg2+And Al3+By interdiffusion of the fixed oxygen lattices due to Al3+Has a slow diffusion rate in Al2O3The MA generated on one side can make the MgO 4.75 times larger than that on one side, the shape of the alumina short fiber with certain directionality is more favorable for being inherited by the formed MA phase, and the pinning effect of the MA phase inhibits the rapid growth of magnesium oxide particles, thereby refining the structure of the ceramic and improving the compactness of the ceramic.
The preparation method of the ceramic slurry comprises the following steps: adding electric melting magnesium oxide powder into a ball milling tank according to a ratio, preparing a solution from nano aluminum sol, a rheological agent and a proper amount of deionized water, adding nano lanthanum oxide and aluminum oxide short fibers, performing ultrasonic treatment for 30-60 min to fully disperse the nano lanthanum oxide and the aluminum oxide short fibers in the solution, adding the solution into the ball milling tank, adding corundum balls according to a ball-to-material ratio of 2:1, performing ball milling at a rotating speed of 60-120 rpm for 2-4 h to uniformly mix the mixture, and performing vacuum exhaust for 10-15 min under a negative pressure of 0.02-0.05 MPa to obtain the composite material.
(2) Pouring the ceramic slurry into a gypsum mold by a slip casting method, demolding, and drying in a ventilation chamber at 80-120 ℃ to obtain a crucible biscuit. Specifically, the preparation method of the crucible biscuit comprises the following steps: and (2) quickly injecting the ceramic slurry into a gypsum mold, placing the gypsum mold on a vibration forming machine for vibration forming, stopping vibration when the slurry is completely filled in the mold and the surface of the slurry is uniformly spread, flattening the surface of the spread slurry, demolding when water escapes from the surface of a blank, and drying in a ventilation chamber at the temperature of 80-120 ℃ to obtain a crucible biscuit.
(3) And (3) putting the dried biscuit into a sintering furnace, heating to 1400-1600 ℃ for high-temperature sintering, and cooling to room temperature along with the furnace to obtain the magnesium oxide-based crucible blank. The sintering process comprises the following steps: heating to 550 ℃ at a heating rate of 60 ℃/h to decompose and gasify organic matters in the biscuit and discharge the organic matters, heating to 1100 ℃ at a heating rate of 200 ℃/h, then heating to 1400-1600 ℃ at a heating rate of 50 ℃/h, and preserving heat at the temperature for 2-3 h.
(4) And (2) carrying out vacuum infiltration treatment on the magnesium oxide base crucible blank in alumina sol, then carrying out surface polishing treatment, drying, carrying out high-temperature secondary sintering at the temperature of 1400-1600 ℃, and cooling to room temperature along with the furnace to obtain the magnesium oxide base crucible.
The vacuum infiltration treatment method of the magnesium oxide-based crucible blank in the alumina sol comprises the following steps: putting the magnesia-based crucible blank into alumina sol, carrying out vacuum infiltration treatment for 30min under the negative pressure of 0.02 MPa-0.05 MPa, baking the magnesia-based crucible blank in a baking oven at the temperature of 120 +/-10 ℃ for 24 hours, and then repeatedly carrying out twice according to the method; then, polishing the surface of the aluminum sol serving as cooling liquid on a grinding machine, and baking the aluminum sol in an oven at the temperature of 120 +/-10 ℃ for 24 hours; and finally, performing high-temperature secondary sintering on the dried crucible blank with the polished surface, wherein the secondary sintering process comprises the following steps: heating to 600 ℃ at a heating rate of 60 ℃/h, then heating to 1380-1480 ℃ at a heating rate of 300 ℃/h, and preserving heat for 2-3 h at the temperature.
The lower temperature rise speed in the low-temperature sintering stage can prevent the biscuit collapse or deformation damage caused by the excessively high decomposition speed of the rheological agent, and after the sintering temperature exceeds 1100 ℃ in the high-temperature sintering stage, the lower temperature rise speed can ensure the temperature in the sintering body to be consistent, and meanwhile, the generation speed of the generated spinel is prevented from being uniform, and the deformation and cracking of the sintering body caused by the excessively fast generated phase change stress are avoided.
The magnesium oxide-based crucible is prepared by a slip casting method, and has the advantages of simple process equipment, uniform crucible wall thickness, low cost, high efficiency, suitability for large-scale production and the like; the prepared magnesia-based crucible does not contain any component for reducing the chemical stability of the magnesia-based crucible, the added nano alumina sol and nano lanthanum oxide not only can play a role in reducing the sintering temperature, but also can be highly and uniformly dispersed into magnesia ceramic powder particles and react with the magnesia ceramic powder particles to generate a spinel solid solution phase with chemical stability to magnesium and magnesium alloy melt so as to weld the magnesia particles together, and meanwhile, the form of alumina short fibers with certain directionality is inherited by the formed magnesia-alumina spinel, so the prepared magnesia-based crucible has good strength, chemical stability and thermal shock resistance, and is particularly suitable for smelting magnesium and aluminum alloy. The method specifically comprises the following steps:
firstly, the preparation method of the alumina short fiber reinforced magnesia-based crucible has excellent chemical stability. The added nano lanthanum oxide reacts with the electric melting MgO to generate MgLa with excellent high-temperature stability2O4Spinel phase (melting point 2030 ℃ C.). Although the raw material alumina sol component contains gamma-Al which reacts with the magnesium liquid2O3And alumina short fiber, but the added nano aluminum sol forms gamma-Al on the surfaces of the magnesia particles and the alumina short fiber with high uniform dispersion2O3Coating film of Al during sintering2O3Reacts with MgO in situ to generate magnesium aluminate spinel (MgAl)2O4MA) phase, which directly fuses together the cristobalite MgO grains.
In the magnesium melt and MgO-Al added with alumina2O3In addition to the reaction formula (1), the following reaction may be present in the reaction system for sintering ceramics:
3Mg(l)+4Al2O3(s)=3MgAl2O4(s)+2Al(l) (5)
magnesium aluminate spinel MgAl generated by alumina and magnesia2O4The reaction of (a) is:
MgO(s)+Al2O3(s)=MgAl2O4(s) (6)
magnesium melt and magnesium aluminate spinel MgAl2O4The reactions that occur are:
3Mg(l)+MgAl2O4(s)=2Al(l)+4MgO(s) (7)
according to the pure substance thermochemistry data handbook (edited by Sudoku of Helh Sanger Valenchen, Chengmelin et al, Beijing: scientific Press, 2003), the Gibbs free energy data of the reaction system of magnesium melt and magnesium aluminate spinel at 900-1200K and the Gibbs free energy change delta G of the reactions (1), (5), (6) and (7)1、ΔG5、ΔG6、ΔG7The calculation results of (a) are shown in table 1.
TABLE 1 Gibbs free energy of each reaction in a 900-1200K magnesium melt and magnesium aluminate spinel reaction system
Change Δ G calculation result
Figure BDA0001621119620000081
Reaction formula Gibbs free energy delta G of formula (5) for forming magnesium aluminate spinel by magnesium melt and alumina5The temperature difference is minimal, which indicates that the reaction can preferentially occur at the common melting temperature of magnesium alloy. Although the reaction formula (7) of the magnesium liquid and the magnesium aluminate spinel is thermodynamically feasible, the reaction is essentially a reaction between the magnesium liquid and alumina, which is a decomposition product of the magnesium aluminate spinel, but it is known from table 1 that the reaction of the magnesium aluminate spinel to alumina and magnesia is difficult to proceed at the melting temperature of the magnesium alloy (reverse reaction of the reaction formula (6)), and the residual alumina in the sintered ceramic and the magnesium liquid preferentially form the magnesium aluminate spinel according to the reaction formula (5); on the other hand, MgO-Al2O3In the phase diagram, the MgO side is a periclase solid solution and MA spinel solid solution eutectic phase diagram, and almost no O is generated in the process of generating MA through in-situ reaction2-Diffusion, only Mg2+And Al3+Through mutual diffusion of fixed oxygen lattices, Al with slower diffusion speed is generated3+Determined that the MA phase is mainly in Al2O3One side is grown by means of an epitaxial growth, resulting in the formation of a limited solid solution between the MA phase and MgO, while the MgO content in the MA outer layer in contact with the MgO particles is much higher than its average value, while MgO does not react with the magnesium melt, so that the magnesium aluminate spinel phase fusing together the magnesium oxide particles in the sintered ceramic structure is stable in the magnesium melt.
The preparation method of the alumina short fiber reinforced magnesia-based crucible does not contain any component for reducing the chemical stability of the alumina short fiber reinforced magnesia-based crucible, and the added nano alumina sol can not only be used in the electric melting magnesia particles and the highly uniformly dispersed nano La2O3Surface of powder and alumina staple fiberFormation of gamma-Al2O3Coating the film to act as a binder, Al during sintering2O3And La2O3React with MgO in situ to respectively generate MgAl with chemical stability to magnesium and alloy melt thereof2O4And MgLa2O4Spinel phase (La has a smaller electronegativity than Mg and Al, MgLa2O4Spinel phase chemical stability ratio MgAl2O4Higher), therefore, the spinel phase synthesized in situ in the crucible prepared by the invention directly fuses the cristobalite MgO grains together, the structure has good chemical stability in the magnesium melt, and the damage of the existing product added with silica sol, ethyl silicate and other binders to the chemical stability of the ceramic is avoided; meanwhile, the ceramic component does not contain sodium salt (for example, sodium carboxymethylcellulose is not adopted in the rheological agent), so that residual Na with larger ionic radius is avoided+The resistance to sintering of the ceramic.
Because the reaction formulas (1) and (5) can spontaneously proceed at the common melting temperature of the magnesium alloy, and the melting temperature of the aluminum and the aluminum alloy is the same as that of the magnesium and the aluminum alloy, the reverse reactions of the reaction formulas (1) and (5) can not occur between the MgO spinel phase and the aluminum alloy melt; the same as that used for magnesium and alloy melt, avoids the damage of adding bonding agents such as silica sol, ethyl silicate and the like to the chemical stability of ceramics in aluminum and alloy melt (even if the material contains 1 percent of SiO)2The melt of aluminum and its alloy will also react with SiO in the ceramic at high temperature2Generation of Al + SiO2→Al2O3Reaction of + Si); therefore, the prepared alumina short fiber reinforced magnesia ceramic crucible can also be used for smelting and purifying aluminum and aluminum alloy. In addition, the grouting slurry for preparing the crucible can also be used as a brickwork and inner wall trowelling slurry of an aluminum alloy reflection smelting furnace.
Secondly, the preparation method of the alumina short fiber reinforced magnesia-based crucible has good low-temperature sintering performance. The nano aluminum sol and the nano lanthanum oxide can be dissolved into the crystal lattice of MgO in a solid solution in the sintering process to ensure that the crystal lattice of MgO generates distortion and activates the crystal lattice, and simultaneously, the nano aluminum sol and the nano lanthanum oxide react with the MgO particles to sinter to generate a new materialCompound (2) MgAl2O4And MgLa2O4Spinel phase, thereby promoting sintering and grain-to-grain bonding. Nanopowder refers to the particle size<The 100nm superfine powder has the characteristics of large specific surface area, high surface energy, high activity and the like, so that the nanometer powder is easy to combine with other atoms, and the melting point and the sintering temperature of the nanometer powder are much lower than those of the superfine powder. The sintering aid added in the form of nano alumina sol and nano lanthanum oxide can fill gaps among the raw material micro powder particles, optimize ceramic particle gradation and mixing uniformity, and meanwhile, the nano powder has high-reactivity nano gamma-Al in the alumina sol due to the surface and interface effects of the nano powder2O3The nanometer lanthanum oxide and MgO particles are fully contacted, so that the reaction speed is rapidly improved, the sintering temperature is reduced, the density and the mechanical property of the ceramic are improved, and the reduction of the sintering temperature is beneficial to reducing the energy consumption and the production cost of the ceramic crucible. Tests show that the sintering temperature of the preparation method of the alumina short fiber reinforced magnesia-based crucible with good tissue combination is 1400-1600 ℃.
Thirdly, the preparation method of the alumina short fiber reinforced magnesia-based crucible has good thermal shock resistance. The electro-melting magnesium oxide is selected, and has strong hydration resistance. The reaction sintering of magnesium oxide and aluminum oxide to form MA causes volume expansion (linear expansion rate of 2.3%, volume expansion rate of 6.9%) and increases the sintering load. gamma-Al2O3Alumina is a porous substance with oxygen ions close to cubic face-centered close packing, Al3+The metastable transition crystal structure irregularly distributed in octahedral and tetrahedral gaps formed by oxygen ions is the same as the crystal structure of magnesium aluminate spinel MA. Using gamma-Al2O3Substituted alpha-Al2O3The sintering characteristic of the MgO-MA material is changed, and the volume is shrunk by 2.7 percent when MA is formed, so that the sintering compactness is improved. The mechanical property of the ceramic matrix composite material can be improved by adopting the fibers and the whiskers as the reinforcement. In the scheme provided by the invention, the nano aluminum sol forms a continuous film on the surfaces of the electric melting magnesium oxide particles and the highly dispersed aluminum oxide short fibers, and reacts with MgO in situ in the sintering process to generate magnesium aluminumSpinel MA phase, MA directly welding the crystal grains of the cristobalite MgO together. There is little O during MA formation2-Diffusion of ions, but only Mg2+And Al3+By interdiffusion of the fixed oxygen lattices due to Al3+Has a slow diffusion rate in Al2O3The MA generated on one side can make the shape of alumina short fiber with certain directionality 4.75 times of that of MgO side be more favorable for being inherited by the formed MA phase, and the pinning effect of the MA phase inhibits the rapid growth of magnesia particles, thereby refining the structure of the ceramic and improving the compactness of the ceramic; with MgO and Al2O3Compared with the prior art, the thermal expansion coefficient of the magnesia-alumina spinel phase is small, and the thermal conductivity coefficient is low, so that the preparation method of the prepared alumina short fiber reinforced magnesia-based crucible has high mechanical property, high temperature impact resistance and thermal shock resistance.
In addition, the cellulose ether and the polyvinyl alcohol which are used as rheological agents are good dispersants for alumina short fibers and nano lanthanum oxide powder, can prevent slurry from agglomerating, can also play a role of a binder when a biscuit is prepared, so that the biscuit has higher strength, and can easily escape in a sintering process without polluting products, thereby ensuring the sintering quality of the crucible.
Drawings
FIG. 1 is a flow chart of a preparation process of a zirconium dioxide short fiber and magnesium oxysulfate whisker composite reinforced magnesium oxide-based crucible.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
The alumina short fiber reinforced magnesia-based crucible is prepared by slip casting electrically fused magnesia-based ceramic slurry containing nano lanthanum oxide and alumina short fiber in a gypsum mold, drying and sintering. The specific preparation process is shown in figure 1.
Example 1
According to the proportion that the nano lanthanum oxide accounts for 1 percent of the mass of the ceramic powder, the alumina short fiber accounts for 1 percent of the mass of the ceramic powder, and the balance is the fused magnesia, the nano lanthanum oxide with the grain diameter of 60nm and the commercialized polycrystalline Al with small length-diameter ratio2O3Short fiber (diameter of 10-20 μm and length of 50-100 μm) and particle size of 250 mesh (median diameter d)5058 μm) of fused magnesia powder to prepare ceramic powder; mixing the polyvinyl alcohol and the hydroxyethyl cellulose according to the mass ratio of 2:3 to prepare the rheological agent.
According to the mass percentage, 15 percent of nano aluminum sol with the solid content of 20 percent (commercial nano aluminum sol with the pH value close to neutral is selected, the same is applied below), 0.8 percent of rheological agent and the balance of ceramic powder are mixed. Firstly, adding electric melting magnesium oxide powder into a ball milling tank according to a ratio, preparing nano aluminum sol, a rheological agent and a proper amount of deionized water (the adding amount is determined according to the solid content of ceramic slurry, the same is applied below) into a solution, adding nano lanthanum oxide and aluminum oxide short fibers, mixing and carrying out ultrasonic treatment for 30min to ensure that the nano lanthanum oxide and the aluminum oxide short fibers are fully dispersed in the solution and then added into the ball milling tank, adding corundum balls according to the ball-to-material ratio of 2:1, carrying out ball milling for 4h at the rotating speed of 60rpm to uniformly mix the mixture, and then carrying out vacuum exhaust for 15min under the negative pressure of 0.02MPa to obtain the ceramic slurry with the solid content of 70%;
and (3) quickly injecting the ceramic slurry into a gypsum mould, placing the gypsum mould on a vibration forming machine for vibration forming, stopping vibration when the mould is completely filled with the slurry and the slurry surface is uniformly overflowed, and flattening the overflowed surface. And demolding when no water escapes from the surface of the blank, and drying in a ventilation chamber at 80 ℃ to obtain a crucible biscuit.
And (2) putting the dried biscuit into a sintering furnace, heating to 550 ℃ at a heating rate of 60 ℃/h to decompose and gasify organic matters such as rheological agents in the biscuit and discharge the organic matters, heating to 1100 ℃ at a heating rate of 200 ℃/h, heating to 1600 ℃ at a heating rate of 50 ℃/h, preserving heat at the temperature for 2.5h, and cooling to room temperature along with the furnace to obtain the magnesia-based crucible blank.
Putting the magnesia-based crucible blank into alumina sol, carrying out vacuum infiltration treatment for 30min under the negative pressure of 0.02MPa, baking for 24 hours in a baking oven at the temperature of 120 +/-10 ℃, and then repeating the steps twice according to the method; then, polishing the surface of the aluminum sol serving as cooling liquid on a grinding machine, and baking the aluminum sol in an oven at the temperature of 120 +/-10 ℃ for 24 hours; and finally, performing high-temperature secondary sintering on the dried crucible blank with the polished surface, wherein the secondary sintering process comprises the steps of heating to 1100 ℃ at the heating rate of 200 ℃/h, then heating to 1600 ℃ at the heating rate of 50 ℃/h, preserving heat for 2.5h at the temperature, and cooling to room temperature along with the furnace to obtain the magnesium oxide-based crucible blank.
Example 2
According to the proportion that the nano lanthanum oxide accounts for 3 percent of the ceramic powder by mass, the alumina short fiber accounts for 3 percent of the ceramic powder by mass, and the balance is the fused magnesia, the nano lanthanum oxide with the grain diameter of 30nm and the commercialized polycrystalline Al with small length-diameter ratio2O3Short fibers (diameter of 10 to 20 μm and length of 50 to 100 μm) and a particle diameter of 500 mesh (median diameter d)5025 μm) of fused magnesia powder to prepare ceramic powder; mixing the polyvinyl alcohol and the hydroxypropyl cellulose according to the mass ratio of 2:3 to prepare the rheological agent.
According to the mass percentage, 25 percent of nano-alumina sol with the solid content of 25 percent, 1.5 percent of rheological agent and the balance of ceramic powder are mixed. Firstly, adding electric melting magnesium oxide powder into a ball milling tank according to a ratio, preparing a solution from nano aluminum sol, a rheological agent and a proper amount of deionized water, adding nano lanthanum oxide and aluminum oxide short fibers, mixing and performing ultrasonic treatment for 60min to fully disperse the nano lanthanum oxide and the aluminum oxide short fibers in the solution, adding the solution into the ball milling tank, adding corundum balls according to a ball-to-material ratio of 2:1, performing ball milling at a rotating speed of 120rpm for 2h to uniformly mix the solution, and performing vacuum exhaust for 10min under a negative pressure of 0.05MPa to obtain ceramic slurry with a solid content of 80%.
And (3) quickly injecting the ceramic slurry into a gypsum mould, placing the gypsum mould on a vibration forming machine for vibration forming, stopping vibration when the mould is completely filled with the slurry and the slurry surface is uniformly overflowed, and flattening the overflowed surface. And demolding when no water escapes from the surface of the blank, and drying in a ventilation chamber at 120 ℃ to obtain a crucible biscuit.
And (2) putting the dried biscuit into a sintering furnace, heating to 550 ℃ at a heating rate of 60 ℃/h to decompose and gasify organic matters such as rheological agents in the biscuit and discharge the organic matters, heating to 1100 ℃ at a heating rate of 200 ℃/h, heating to 1450 ℃ at a heating rate of 50 ℃/h, preserving heat at the temperature for 2h, and cooling to room temperature along with the furnace to obtain the magnesia-based crucible blank.
Putting the magnesia-based crucible blank into alumina sol, carrying out vacuum infiltration treatment for 30min under the negative pressure of 0.05MPa, baking the magnesia-based crucible blank in a baking oven at the temperature of 120 +/-10 ℃ for 24 hours, and then repeatedly carrying out twice according to the method; then, polishing the surface of the aluminum sol serving as cooling liquid on a grinding machine, and baking the aluminum sol in an oven at the temperature of 120 +/-10 ℃ for 24 hours; and finally, performing high-temperature secondary sintering on the dried crucible blank with the polished surface, wherein the secondary sintering process comprises the steps of heating to 1100 ℃ at the heating rate of 200 ℃/h, then heating to 1450 ℃ at the heating rate of 50 ℃/h, preserving heat for 2h at the temperature, and cooling to room temperature along with the furnace to obtain the magnesium oxide-based crucible blank.
Example 3
According to the proportion that the nano lanthanum oxide accounts for 2 percent of the ceramic powder by mass, the alumina short fiber accounts for 2 percent of the ceramic powder by mass, and the balance is the fused magnesia, the nano lanthanum oxide with the grain diameter of 45nm and the commercial polycrystalline Al with small length-diameter ratio2O3Short fiber (diameter of 10-20 μm and length of 50-100 μm) and particle size of 325 mesh (median diameter d)5045 μm) of fused magnesia powder to prepare ceramic powder; mixing the polyvinyl alcohol and the hydroxyethyl cellulose according to the mass ratio of 2:3 to prepare the rheological agent.
According to the mass percentage, 20 percent of nano aluminum sol with the solid content of 22 percent, 1 percent of rheological agent and the balance of ceramic powder are mixed. Firstly, adding electric melting magnesium oxide powder into a ball milling tank according to a ratio, preparing a solution from nano aluminum sol, a rheological agent and a proper amount of deionized water, adding nano lanthanum oxide and aluminum oxide short fibers, mixing and performing ultrasonic treatment for 45min to fully disperse the nano lanthanum oxide and the aluminum oxide short fibers in the solution, adding the solution into the ball milling tank, adding corundum balls according to a ball-to-material ratio of 2:1, performing ball milling at a rotating speed of 100rpm for 3h to uniformly mix the mixture, and performing vacuum exhaust for 12min under a negative pressure of 0.03MPa to obtain ceramic slurry with a solid content of 75%.
And (3) quickly injecting the ceramic slurry into a gypsum mould, placing the gypsum mould on a vibration forming machine for vibration forming, stopping vibration when the mould is completely filled with the slurry and the slurry surface is uniformly overflowed, and flattening the overflowed surface. And demolding when no water escapes from the surface of the blank, and drying in a ventilation chamber at 100 ℃ to obtain a crucible biscuit.
And (2) putting the dried biscuit into a sintering furnace, heating to 550 ℃ at a heating rate of 60 ℃/h to decompose and gasify organic matters such as rheological agents in the biscuit and discharge the organic matters, heating to 1100 ℃ at a heating rate of 200 ℃/h, heating to 1400 ℃ at a heating rate of 50 ℃/h, preserving heat at the temperature for 3h, and cooling to room temperature along with the furnace to obtain the magnesia-based crucible blank.
Putting the magnesia-based crucible blank into alumina sol, carrying out vacuum infiltration treatment for 30min under the negative pressure of 0.03MPa, baking the magnesia-based crucible blank in a baking oven at the temperature of 120 +/-10 ℃ for 24 hours, and then repeating the steps twice according to the method; then, polishing the surface of the aluminum sol serving as cooling liquid on a grinding machine, and baking the aluminum sol in an oven at the temperature of 120 +/-10 ℃ for 24 hours; and finally, performing high-temperature secondary sintering on the dried crucible blank with the polished surface, wherein the secondary sintering process comprises the steps of heating to 1100 ℃ at the heating rate of 200 ℃/h, then heating to 1400 ℃ at the heating rate of 50 ℃/h, preserving heat for 3h at the temperature, and cooling to room temperature along with the furnace to obtain the magnesium oxide-based crucible blank.
Example 4
According to the proportion that the nano lanthanum oxide accounts for 1.5 percent of the ceramic powder by mass, the alumina short fiber accounts for 2.5 percent of the ceramic powder by mass, and the balance is the electric melting magnesia, the nano lanthanum oxide with the grain diameter of 30nm and the commercial polycrystalline Al with small length-diameter ratio2O3Short fiber (diameter of 10-20 μm and length of 50-100 μm) and particle size of 325 mesh (median diameter d)5045 μm) of fused magnesia powder to prepare ceramic powder; according to the weight ratio of polyvinyl alcohol: hydroxypropyl methylcellulose: the hydroxyethyl cellulose is mixed according to the mass ratio of 4:3:3 to prepare the rheological agent.
According to the mass percentage, 20 percent of nano aluminum sol with the solid content of 20 percent, 1.2 percent of rheological agent and the balance of ceramic powder are mixed. Firstly, adding electric melting magnesium oxide powder into a ball milling tank according to a ratio, preparing a solution from nano aluminum sol, a rheological agent and a proper amount of deionized water, adding nano lanthanum oxide and aluminum oxide short fibers, performing ultrasonic treatment for 45min to fully disperse the nano lanthanum oxide and the aluminum oxide short fibers in the solution, adding the solution into the ball milling tank, adding corundum balls according to a ball-to-material ratio of 2:1, performing ball milling for 3h at a rotating speed of 80rpm to uniformly mix the mixture, and performing vacuum exhaust for 12min under a negative pressure of 0.04MPa to obtain ceramic slurry with a solid content of 75%.
And (3) quickly injecting the ceramic slurry into a gypsum mould, placing the gypsum mould on a vibration forming machine for vibration forming, stopping vibration when the mould is completely filled with the slurry and the slurry surface is uniformly overflowed, and flattening the overflowed surface. And demolding when no water escapes from the surface of the blank, and drying in a ventilation chamber at 100 ℃ to obtain a crucible biscuit.
And (2) putting the dried biscuit into a sintering furnace, heating to 550 ℃ at a heating rate of 60 ℃/h to decompose and gasify organic matters such as rheological agents in the biscuit and discharge the organic matters, heating to 1100 ℃ at a heating rate of 200 ℃/h, heating to 1500 ℃ at a heating rate of 50 ℃/h, preserving heat at the temperature for 2.5h, and cooling to room temperature along with the furnace to obtain the magnesia-based crucible blank.
Putting the magnesia-based crucible blank into alumina sol, carrying out vacuum infiltration treatment for 30min under the negative pressure of 0.03MPa, baking the magnesia-based crucible blank in a baking oven at the temperature of 120 +/-10 ℃ for 24 hours, and then repeating the steps twice according to the method; then, polishing the surface of the aluminum sol serving as cooling liquid on a grinding machine, and baking the aluminum sol in an oven at the temperature of 120 +/-10 ℃ for 24 hours; and finally, performing high-temperature secondary sintering on the dried crucible blank with the polished surface, wherein the secondary sintering process comprises the steps of heating to 1100 ℃ at the heating rate of 200 ℃/h, then heating to 1500 ℃ at the heating rate of 50 ℃/h, preserving heat for 2.5h at the temperature, and cooling to room temperature along with the furnace to obtain the magnesium oxide-based crucible blank.
In the embodiment, the prepared magnesia-based crucible has excellent thermal shock resistance and strength, and does not crack after being cooled in the air at 1000 ℃ for 100 times; the normal-temperature crushing strength of the sintering crucible is not lower than 150 MPa.
The above embodiments do not limit the present invention in any way, and all technical solutions obtained by means of equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims (9)

1. An alumina short fiber reinforced magnesia-based crucible is characterized in that: the electric melting magnesia-based ceramic slurry containing nano lanthanum oxide and alumina short fibers is formed by slip casting in a gypsum mold, and is obtained by drying and sintering; the electric melting magnesia based ceramic slurry containing nano lanthanum oxide and alumina short fiber comprises 15 to 25 mass percent of nano aluminum sol, 0.8 to 1.5 mass percent of rheological agent, and the balance of electric melting magnesia based ceramic powder containing nano lanthanum oxide and alumina short fiber; the rheological agent is a mixture of polyvinyl alcohol and cellulose ether, wherein the polyvinyl alcohol accounts for 40% of the mass of the rheological agent, and the cellulose ether is one or a mixture of industrial hydroxyethyl cellulose and hydroxypropyl methyl cellulose; the ceramic powder is a mixture of nano lanthanum oxide, alumina short fibers and electric melting magnesium oxide.
2. A preparation method of an alumina short fiber reinforced magnesia-based crucible is characterized by comprising the following steps:
(1) preparing 15-25% of nano aluminum sol, 0.8-1.5% of rheological agent and the balance of electric melting magnesia ceramic powder containing nano lanthanum oxide and alumina short fibers according to the mass percentage, adding deionized water, performing ball milling and mixing uniformly, and then performing vacuum exhaust to prepare ceramic slurry with the solid content of 70-80%; the rheological agent is a mixture of polyvinyl alcohol and cellulose ether, wherein the polyvinyl alcohol accounts for 40% of the mass of the rheological agent, and the cellulose ether is one or a mixture of industrial hydroxyethyl cellulose and hydroxypropyl methyl cellulose; the ceramic powder is a mixture of nano lanthanum oxide, alumina short fibers and electric melting magnesium oxide;
(2) pouring the ceramic slurry into a gypsum mold by a slip casting method, demolding, and drying in a ventilation chamber at 80-120 ℃ to obtain a crucible biscuit;
(3) putting the dried biscuit into a sintering furnace, heating to 1400-1600 ℃ for high-temperature sintering, and cooling to room temperature along with the furnace to obtain a magnesium oxide base crucible blank;
(4) and (2) carrying out vacuum infiltration treatment on the magnesium oxide base crucible blank in alumina sol, then carrying out surface polishing treatment, drying, carrying out high-temperature secondary sintering at the temperature of 1400-1600 ℃, and cooling to room temperature along with the furnace to obtain the magnesium oxide base crucible.
3. The method for preparing the alumina short fiber reinforced magnesia-based crucible as claimed in claim 2, wherein: the solid content of the nano aluminum sol is 20-25%.
4. The method for preparing the alumina short fiber reinforced magnesia-based crucible as claimed in claim 2, wherein: the nano lanthanum oxide accounts for 1-3% of the mass of the ceramic powder, the alumina short fiber accounts for 1-3% of the mass of the ceramic powder, and the balance is fused magnesia.
5. The method for preparing the alumina short fiber reinforced magnesia-based crucible as claimed in claim 2, wherein: the particle size of the nano lanthanum oxide is 30-60 nm, and the aluminum oxide short fiber is commercial polycrystalline Al with small length-diameter ratio2O3Short fiber with diameter of 10-20 μm and length of 50-100 μm, and the fused magnesia powder has particle size of 250-500 mesh.
6. The method for preparing the alumina short fiber reinforced magnesia-based crucible as claimed in claim 4, wherein the method for preparing the ceramic slurry comprises: adding electric melting magnesium oxide powder into a ball milling tank according to the proportion, preparing nano aluminum sol, rheological agent and deionized water into a solution, adding nano lanthanum oxide and aluminum oxide short fibers, carrying out ultrasonic treatment for 30-60 min to fully disperse the nano lanthanum oxide and the aluminum oxide short fibers in the solution, adding the solution into the ball milling tank, adding corundum balls according to the ball-to-material ratio of 2:1, carrying out ball milling for 2-4 h at the rotating speed of 60-120 rpm to uniformly mix the mixture, and carrying out vacuum exhaust for 10-15 min under the negative pressure of 0.02-0.05 MPa to obtain the composite material.
7. The method for preparing the alumina short fiber reinforced magnesia-based crucible as claimed in claim 2, wherein the method for preparing the crucible biscuit comprises the following steps: and (2) quickly injecting the ceramic slurry into a gypsum mold, placing the gypsum mold on a vibration forming machine for vibration forming, stopping vibration when the slurry is completely filled in the mold and the surface of the slurry is uniformly spread, flattening the surface of the spread slurry, demolding when water escapes from the surface of a blank, and drying in a ventilation chamber at the temperature of 80-120 ℃ to obtain a crucible biscuit.
8. The method for preparing the alumina short fiber reinforced magnesia-based crucible as claimed in claim 2, wherein: in the step (3), the sintering process is as follows: heating to 550 ℃ at a heating rate of 60 ℃/h to decompose and gasify organic matters in the biscuit and discharge the organic matters, heating to 1100 ℃ at a heating rate of 200 ℃/h, then heating to 1400-1600 ℃ at a heating rate of 50 ℃/h, and preserving heat at the temperature for 2-3 h.
9. The method for preparing the alumina short fiber reinforced magnesia-based crucible as claimed in claim 2, wherein: the vacuum infiltration treatment method of the magnesium oxide-based crucible blank in the alumina sol comprises the following steps: putting the magnesia-based crucible blank into alumina sol, carrying out vacuum infiltration treatment for 30min under the negative pressure of 0.02 MPa-0.05 MPa, baking the magnesia-based crucible blank in a baking oven at the temperature of 120 +/-10 ℃ for 24 hours, and then repeatedly carrying out twice according to the method; then, polishing the surface of the aluminum sol serving as cooling liquid on a grinding machine, and baking the aluminum sol in an oven at the temperature of 120 +/-10 ℃ for 24 hours; and finally, performing high-temperature secondary sintering on the dried crucible blank with the polished surface, wherein the secondary sintering process comprises the following steps: heating to 600 ℃ at a heating rate of 60 ℃/h, then heating to 1380-1480 ℃ at a heating rate of 300 ℃/h, and preserving heat for 2-3 h at the temperature.
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