WO2019196179A1 - 一种Mg(Al, Cr)2O4复合尖晶石增强氧化镁基泡沫陶瓷过滤器及其制备方法 - Google Patents

一种Mg(Al, Cr)2O4复合尖晶石增强氧化镁基泡沫陶瓷过滤器及其制备方法 Download PDF

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WO2019196179A1
WO2019196179A1 PCT/CN2018/089568 CN2018089568W WO2019196179A1 WO 2019196179 A1 WO2019196179 A1 WO 2019196179A1 CN 2018089568 W CN2018089568 W CN 2018089568W WO 2019196179 A1 WO2019196179 A1 WO 2019196179A1
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magnesium oxide
ceramic
foam
sintering
nano
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PCT/CN2018/089568
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English (en)
French (fr)
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刘希琴
刘思雨
刘子利
李健
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江苏中翼汽车新材料科技有限公司
南京航空航天大学
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Publication of WO2019196179A1 publication Critical patent/WO2019196179A1/zh

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Definitions

  • the invention relates to a magnesium oxide based foam ceramic filter and a preparation method thereof, in particular to a Mg(Al,Cr) 2 O 4 composite spinel reinforced magnesium oxide based foam ceramic filter and a preparation method thereof, belonging to a metal material With metallurgical fields.
  • the filter prepared by the invention is particularly suitable for the filtration and purification of magnesium and its alloy melt, and can also be used for the filtration and purification of aluminum and its alloy melt.
  • Magnesium is chemically active. It is easily reacted with oxygen, nitrogen and water vapor during casting and processing. The resulting product remains in magnesium, affecting the internal quality of the product and deteriorating the performance of the product. According to the type and nature of inclusions in magnesium alloys, inclusions are generally divided into two categories: metal inclusions and non-metallic inclusions: (1) Metal inclusions: Magnesium alloys are inevitably introduced during the production and processing of raw magnesium. Some metal elements or metal compounds are intercalated, and they remain in the form of particles or clusters on the matrix or grain boundary of the magnesium alloy, mainly including metal elemental ⁇ -Fe particles and manganese-iron metal compounds such as (Fe, Mn) 3 .
  • Non-metallic inclusions in magnesium alloys are mainly magnesium oxynitrides such as MgO, Mg 3 N 2 , etc.;
  • a refining agent mainly composed of chloride KCl, NaCl, MgCl 2 , etc.
  • the flux cannot be completely removed during the refining process, and a small amount of flux remains in the magnesium melt, causing inclusion of the magnesium metal flux.
  • the suspended oxidized inclusions are pushed toward the grain boundaries by the crystallization front during crystallization, and the inclusions generally remain in the form of a film, a particle, or a cluster at the grain boundary of the magnesium alloy.
  • Statistics show that MgO accounts for more than 80% of all inclusions in magnesium alloys, and its distribution is film-like, granular and cluster-like.
  • the inclusions generated during the magnesium alloy casting process not only seriously deteriorate the mechanical properties and corrosion resistance of the alloy, but also reduce the surface quality of its machining and anodizing.
  • the content of the film-like and particulate oxide inside the alloy needs to be controlled to 100 cm 2 /kg and 100 mm 3 /kg or less to meet the normal use requirements. Therefore, the purification process for removing inclusions in the magnesium melt during the casting process to improve the purity of the melt becomes the key to the production of the magnesium alloy.
  • the melt purification process can be divided into two categories: flux purification and non-flux purification.
  • the flux purification process is a purification process commonly used in the production of magnesium alloys due to high impurity removal efficiency, low cost, and convenient operation.
  • the flux purification also has the disadvantages of increased metal loss, flux inclusion, and inability to degas, especially in the melting of rare earths.
  • the flux also consumes a large amount of rare earth elements in the alloy.
  • the non-flux purification process can not only make up for the deficiency of the flux purification process, but also has excellent purification effect.
  • the special three-dimensional porous ceramic foam ceramic filter can pass the filter cake effect due to its high porosity (70%-90%), strong adsorption capacity and chemical corrosion resistance.
  • the adsorption effect and the rectification effect have a good filtering effect on the inclusion particles in the alloy melt.
  • the foam ceramic filtration method not only filters out fine inclusion particles as small as 10 ⁇ m to 20 ⁇ m in the alloy melt, but also filters out liquid flux inclusions which are difficult to filter out by a general filter medium.
  • US Patent Document US3962081A (Ceramic foam filter), US4024212A (Ceramic foam and method of preparation), Chinese patent document CN103787691A (a method for preparing alumina foam ceramics) and the like all disclose some aluminum alloy, steel melt filtration inclusions
  • the reaction dissolves rapidly, thereby blocking its filtration pores or eroding into the melt of magnesium and its alloys as a harmful component. Therefore, these prior art foam filters are not suitable for the melt of magnesium and magnesium alloys. filter.
  • MgO is a cubic crystal NaCl structure with a lattice constant of 0.411 nm. It is an ion-bond compound with a melting point of 2852 ° C, which is much higher than the commonly used Al 2 O 3 (2054 ° C) and SiO 2 (1650 ⁇ 50 ° C). Therefore, magnesium oxide products have good chemical stability, high electrical resistivity and strong corrosion resistance to metals, slag and alkaline solutions. Compared with commonly used ceramic materials, MgO has good high-temperature chemical stability with magnesium and its alloy melts, does not react with molten slag composed of molten chloride and fluorate, and has a wetted angle with the flux. It is small and easy to adsorb the flux inclusions in the magnesium melt. Therefore, the MgO foam ceramic is an ideal material for the smelting purification of magnesium alloy liquid.
  • the research shows that the heat loss per unit product will be reduced by more than 10% for each reduction of the firing temperature in the sintering ceramics.
  • the addition of sintering aid is an important technical means to reduce the sintering temperature of MgO foam ceramics.
  • V 2 O 5 powder is added, MgO forms a liquid phase of approximately Mg 3 V 2 O 8 with V 2 O 5 at 1190 ° C, promotes sintering, and can significantly reduce the sintering temperature of MgO foam ceramic, but V 2 O 5 has a detrimental effect on the respiratory system and skin during use, and has strict restrictions on operation.
  • cobalt oxide is also a good low-temperature sintering aid, but it is also limited as a highly toxic substance and a rare resource.
  • Fluoride is a strong solvent and mineralizer commonly used in ceramic industry sintering.
  • Fluoride can enter the human body through the respiratory tract, digestive tract and skin. It has toxic effects on the central nervous system and myocardium. Low concentrations of fluorine pollution can cause brittle calcification of teeth and bones. Fluoride is specified in the Ceramic Industry Pollutant Discharge Standard (GB25464-2010). The emission standard must be less than 5.0mg/m 3 . Fluoride as a low-temperature sintering aid for magnesia ceramics will inevitably increase the emission of gaseous fluoride and increase the burden of environmental protection.
  • the fluoride ion in the solid solution fluoride remaining in ceramics is In the form of replacing oxygen ions, the chemical stability of the intergranular bond is lowered, and it is difficult to resist the long-term corrosion of the flux inclusion in the magnesium melt.
  • the foam ceramic filter disclosed in Chinese Patent Publication No. CN101138691A water glass, silica sol and ethyl silicate are used as the binder, and the presence of the SiO 2 component between the sintered foam ceramic particles makes it easy to be combined with magnesium and The alloy melt is reacted according to the formula (4), which also reduces the chemical stability of the foamed ceramic.
  • Chinese patent document CN100536986C magnesia foam ceramic filter
  • CN103553686A a magnesium aluminum spinel foam ceramic filter and its preparation method
  • boron trioxide and borax as the low temperature of magnesium oxide ceramics
  • the sintering aid forms a liquid phase when the boron trioxide is higher than 450 ° C.
  • the reaction with magnesium oxide forms magnesium borate in the form of a liquid phase to lower the sintering temperature.
  • boron trioxide is easily reacted with magnesium and aluminum, and is unstable in the melt of magnesium and aluminum alloy.
  • gallium oxide is a homologous oxide of boron trioxide, which forms a spinel-type MgGa 2 O 4 with magnesium oxide at a lower temperature to reduce the sintering temperature, but has a small amount of gallium resources (gallium is a strategy). Reserve metals), the higher price of gallium oxide limits its use in ordinary ceramics.
  • the object of the present invention is to provide a Mg(Al,Cr) 2 O 4 composite spinel reinforced magnesium oxide based foam ceramic filter which can realize sintering at low temperature and has excellent chemical stability and thermal shock resistance and preparation thereof. method.
  • a Mg(Al,Cr) 2 O 4 composite spinel reinforced magnesium oxide based ceramic foam filter which is coated on a polyurethane foam carrier by using a light-burning magnesium oxide-based ceramic slurry containing a nanometer chromium oxide sintering aid , obtained by drying and sintering.
  • a method for preparing a Mg(Al,Cr) 2 O 4 composite spinel reinforced magnesium oxide based ceramic filter comprises the following steps:
  • nano-alumina sol 15% to 25% nano-alumina sol, 0.8% to 1.5% rheological agent, and the rest are magnesium oxide ceramic powder containing nano-chromium oxide sintering aid, and add anhydrous ethanol ball mill After mixing uniformly, a ceramic slurry having a solid content of 60% to 70% is prepared.
  • the added nano-alumina sol can not only act as a binder, but also reacts in situ with MgO with nano-Cr 2 O 3 which is highly uniformly dispersed in the magnesium oxide powder particles to form a chemically stable magnesium and its alloy melt.
  • the Mg(Al,Cr) 2 O 4 composite spinel phase avoids the damage of the chemical stability of the foam ceramics by adding a binder such as silica sol or ethyl silicate to the existing products.
  • the rheological agent is a mixture of polyvinyl butyral and a cellulose ether, wherein the polyvinyl butyral is 50% by mass of the rheology agent, and the cellulose ether is an industrial hydroxypropyl methyl group.
  • the polyvinyl butyral is 50% by mass of the rheology agent
  • the cellulose ether is an industrial hydroxypropyl methyl group.
  • Cellulose ether and polyvinyl butyral are not only good dispersing agents for nano-chromium oxide powder, but also prevent agglomeration of the slurry, and can act as a binder when preparing the green body.
  • the material can be relatively firmly attached to the polyurethane foam template to make the green body have great strength, and at the same time, it is easy to escape during the sintering process without polluting the product.
  • the rheological agent does not use sodium-containing salts such as sodium carboxymethyl cellulose to avoid the hindrance of the residual ionic radius of Na + to the sintering of the ceramic, and also avoids the Cr 2 O 3 in the basic oxide Na 2 In the presence of O and K 2 O, Cr 3+ is converted into an environmental problem caused by Cr 6+ which is seriously harmful to human health.
  • the ceramic powder is a mixture of light burned magnesium oxide and nano chromium oxide.
  • the nanometer chromium trioxide accounts for 1% to 2% of the mass of the ceramic powder, and the nanometer chromium oxide has a particle diameter of 30 to 60 nm.
  • the light-burned magnesium oxide powder has a particle diameter of 250 mesh to 500 mesh (median diameter d 50 is 25 ⁇ m to 58 ⁇ m).
  • the lightly burned magnesia powder has high sintering activity.
  • the nano-alumina sol and the nano-chromium oxide can be solid-dissolved into the MgO lattice during the sintering process to cause lattice distortion of the MgO crystal and activate the crystal lattice.
  • the Mg(Al,Cr) 2 O 4 composite spinel phase is formed by reaction sintering with MgO particles, thereby promoting sintering and particle phase bonding.
  • the nano-powder has the characteristics of large specific surface area, high surface energy and high activity.
  • the low-temperature sintering aid is added in the form of nano-alumina sol and nano-chromium trioxide to optimize the gradation and mixing uniformity of the ceramic particles.
  • the nano-powder Due to its surface and interfacial effects, the nano-powder has sufficient contact between the nano-sintering aid and the MgO particles to rapidly increase the reaction rate of the spinel phase, thereby further reducing the sintering temperature, and the reduction of the sintering temperature is beneficial to lowering. Energy consumption and production costs of ceramic foam filters.
  • the magnesia powder in the ceramic powder has a wide contact surface with the aluminum sol and the nano-Cr 2 O 3 , and the diffusion rate of Cr 3+ into MgO is fast, so that the perician MgO spinel is petrified. At the same time, it promotes the diffusion of Al 2 O 3 into MgO. Therefore, there is a close continuous bonding interface between MgAl 2 O 4 and MgCrO 4 formed by in-situ reaction and periclase solid solution.
  • MgAl 2 O 4 and MgCrO 4 have infinite mutual solubility, and MgO particles are directly combined with the surrounding Mg(Al,Cr) 2 O 4 composite spinel, and the pinning of the composite spinel phase inhibits oxidation.
  • the growth of magnesium particles refines the structure of the foamed ceramic and increases the density between the ceramic grains. Therefore, the prepared Mg(Al,Cr) 2 O 4 composite spinel reinforced magnesium oxide foam ceramic filter has Higher mechanical properties.
  • ion exchange diffusion at the time of firing synthesizes a spinel solid solution, and since the Al 3+ diffusion rate is slower than Mg 2+ and Cr 3+ , the magnesium oxide particles and the MgO/composite spinel are combined with the matrix.
  • the concentration gradient of Al 2 O 3 is generated at the interface, and at the same time, due to their different coefficients of thermal expansion, cracks are formed at the interface between the magnesium oxide particles and the MgO/composite spinel bonded matrix.
  • the composite spinel solid solution usually exists in the interlayer between the periclase crystals, which can compensate the stress at the interface of each phase, relax the thermal stress generated during the cooling process, and prevent the crack from expanding.
  • the nano-aluminum sol has a solid content of 20% to 25% and a pH of ⁇ 4.
  • the preparation method of the ceramic slurry is as follows: adding the lightly burned magnesia powder to the ball mill tank according to the ratio, mixing the nano aluminum sol, the nano chromium oxide, the rheological agent and the absolute ethanol and sonicating for 30 min to 60 min.
  • the nano cerium oxide powder is sufficiently dispersed and added to the ball mill tank, and then the corundum ball is added in a ratio of 2:1 of the ball to the ball, and the mixture is uniformly milled at a speed of 60 to 120 rpm for 2 to 4 hours.
  • the ceramic slurry is easily uniformly applied to the polyurethane foam template.
  • the polyurethane foam stencil has a specification of 10 PPI to 20 PPI (Pores per inch, the average number of holes per unit length); before use, the surface is immersed in a 15% to 20% NaOH aqueous solution at 40 ° C to 50 ° C for 40 min to 60 min. After that, it is washed with water and naturally dried, and then immersed in an aqueous solution of 2% to 4% of a dodecylbenzenesulfonic acid wetting agent, and then taken out and dried to obtain. After the surface is roughened by NaOH etching and treated by an aqueous solution of a dodecylbenzenesulfonate wetting agent, the ceramic slurry is easily uniformly applied to the polyurethane foam template.
  • the dried green body is placed in a sintering furnace, heated to a temperature of 1350 ° C to 1550 ° C for high-temperature sintering, and cooled to room temperature with a furnace to obtain a magnesium oxide-based ceramic foam filter.
  • the sintering process is heated to 550 ° C at a heating rate of 30 ° C / h to decompose and vaporize the organic matter (polyurethane foam, rheological agent, etc.) in the foam ceramic filter blank, and then at a heating rate of 200 ° C / h Heating to a temperature of 1100 ° C, in the low-temperature sintering stage, the lower heating rate can prevent the polyurethane foam and the rheological agent from decomposing too fast, resulting in collapse or deformation damage of the green body. Finally, it is heated to a temperature of 1350 ° C to 1550 ° C at a heating rate of 50 ° C / h and kept at this temperature for 2 to 3 h.
  • the lower heating rate can ensure the uniform temperature in the sintered body, while avoiding the uniform formation rate of the spinel and avoiding the deformation stress and cracking of the sintered body due to excessively rapid phase transformation stress. .
  • the preparation method of the magnesium oxide-based ceramic foam filter provided by the invention has the advantages of simple process, low cost, high efficiency, suitable for large-scale production, etc., and the prepared magnesium oxide-based ceramic foam filter does not contain any chemical stability.
  • the components, the added nano-aluminum sol and the nano-chromium oxide can not only reduce the sintering temperature, but also highly uniformly disperse into the magnesium oxide ceramic powder particles and react with it to form a magnesium and its alloy melt.
  • the chemically stable Mg(Al,Cr) 2 O 4 composite spinel phase fuses the magnesium oxide particles together.
  • the ceramic foam filter has good strength, chemical stability and thermal shock resistance, and is particularly suitable for use in Filtration and purification of inclusions in the melt of magnesium and its alloys can also be used for melt filtration of aluminum and its alloys.
  • the Mg(Al,Cr) 2 O 4 composite spinel reinforced magnesium oxide foam ceramic filter of the present invention has excellent chemical stability.
  • the chromium ion radius is smaller than the magnesium ion radius, and Cr 2 O 3 has an ⁇ -Al 2 O 3 structure, and the solid solubility in the periclase MgO is larger than that of Al 2 O 3 .
  • the added nano-Cr 2 O 3 is easily dissolved in the MgO phase, and a magnesium chrome spinel (MgCr 2 O 4 ) phase (melting point 2180 ° C) having high temperature stability is formed by reaction sintering.
  • the raw material component aluminum sol contains Al 2 O 3 reacting with the magnesium liquid
  • the added nano aluminum sol forms ⁇ -Al 2 O 3 on the surface of the lightly burned magnesium oxide particles and the highly uniformly dispersed nano Cr 2 O 3 powder.
  • the coating film is in situ reacted with MgO during sintering to form a high melting point magnesium aluminate spinel (MgAl 2 O 4 ) phase (melting point 2135 ° C) having a face centered cubic lattice.
  • MgAl 2 O 4 and MgCrO 4 can be completely miscible.
  • the ceramic foam filter prepared by the present invention has only the pericl MgO and MgAl 2 O 4 -MgCr 2 O 4 composite spinel phases.
  • reaction formula (1) In the reaction system of the magnesium melt and the alumina-added MgO-Al 2 O 3 sintered ceramic, in addition to the reaction formula (1), the following reaction may exist:
  • the Gibbs free energy ⁇ G 5 of the formula (5) of the reactive magnesium melt and the alumina-forming magnesium aluminate spinel is the smallest at different temperatures, indicating that the reaction takes precedence at the usual melting temperature of the magnesium alloy.
  • the reaction formula (7) of magnesium liquid and magnesium aluminum spinel is thermodynamically achievable, but the reaction is essentially a reaction between the magnesium solution and the decomposition product of magnesium aluminate spinel, but it is known from Table 1. At the melting temperature of magnesium alloy, the reaction of magnesium aluminate spinel into alumina and magnesia is difficult to carry out (reaction of reaction formula (6)), and the residual alumina in the sintered ceramic is also preferred to magnesium.
  • Magnesium-aluminum spinel is formed according to reaction formula (5); on the other hand, the MgO side of the MgO-Al 2 O 3 phase diagram is a eutectic phase diagram of the periclase solid solution and the MA spinel solid solution, which is generated in situ by reaction. There is almost no O 2- diffusion in the MA process. Only Mg 2+ and Al 3+ diffuse through the fixed oxygen lattice. The rate of formation is determined by the slower diffusion of Al 3+ , and the MA phase is mainly in Al 2 O 3 .
  • the side is formed by the internal growth method, resulting in the formation of a finite solid solution between the MA phase and the MgO, while the MgO content in the outer layer of the MA in contact with the MgO particles is much higher than the average value, and the MgO does not react with the magnesium melt, therefore,
  • the magnesium-aluminum spinel phase in which the magnesia particles are fused together in the sintered ceramic structure is capable of being in the magnesium melt Stable enough.
  • the Mg(Al,Cr) 2 O 4 composite spinel magnesia ceramic foam filter of the invention does not contain any component which reduces its chemical stability, and the added nano aluminum sol can not only function as a binder, Moreover, in-situ reaction with MgO with nano-Cr 2 O 3 highly uniformly dispersed in magnesium oxide powder particles to form Mg(Al,Cr) 2 O 4 composite spinel which is chemically stable to magnesium and its alloy melt.
  • the phase avoids the damage of the chemical stability of the foam ceramics by adding the binders such as silica sol and ethyl silicate to the existing products; meanwhile, the ceramic component does not contain the sodium salt (for example, the carboxymethyl group is not used in the rheological agent).
  • Cellulose sodium avoids the inhibition of ceramic sintering by Na + with a large residual ionic radius, and also avoids the conversion of Cr 3 O to human by Cr 2 O 3 in the presence of basic oxides Na 2 O and K 2 O Environmental problems caused by Cr 6+, which has serious health hazards.
  • the melting temperatures of aluminum and its alloys are the same as those of magnesium and its alloys, MgO and MA spinel phases and aluminum and
  • the alloy melt does not undergo the reverse reaction of the reaction formulas (1) and (5); it is the same as that used for the melt of magnesium and its alloy, avoiding the addition of a binder such as silica sol or ethyl silicate to the foam ceramic in aluminum and Chemical stability damage in the alloy melt (even if the material contains 1% SiO 2 , the melt of aluminum and its alloy will react with SiO 2 in the ceramic to form Al+SiO 2 ⁇ Al 2 O 3 +Si at high temperature. Therefore, the prepared Mg(Al,Cr) 2 O 4 composite spinel magnesia ceramic foam filter can also be used for the smelting purification of aluminum and its alloys.
  • the Mg(Al,Cr) 2 O 4 composite spinel reinforced magnesium oxide foam ceramic filter of the invention has good low temperature sintering performance.
  • the light burned magnesia fine powder used in the invention has high sintering activity, and the nano aluminum sol and the nano chromic oxide can be solid-dissolved into the MgO lattice during the sintering process to cause lattice distortion of the MgO crystal, and the activated crystal
  • the lattice is simultaneously sintered by sintering with MgO particles to form a phase phase of Mg(Al,Cr) 2 O 4 composite spinel, thereby promoting the bonding between sintering and particle phase.
  • the nano-powder has the characteristics of large specific surface area, high surface energy and high activity.
  • the low-temperature sintering aid is added in the form of nano-alumina sol and nano-chromium trioxide to optimize the gradation and mixing uniformity of the ceramic particles. Due to its surface and interfacial effects, the nano-powder has sufficient contact between the nano-sintering aid and the MgO particles to rapidly increase the reaction rate of the spinel phase, thereby further reducing the sintering temperature, and the reduction of the sintering temperature is beneficial to lowering. Energy consumption and production costs of ceramic foam filters.
  • the test results show that the Mg(Al,Cr) 2 O 4 composite spinel reinforced magnesium oxide foam ceramic filter with insufficient sintering strength and low strength is formed when the sintering temperature is lower than 1350 °C.
  • the sintering temperature is from 1350 ° C to 1550 ° C.
  • the Mg(Al,Cr) 2 O 4 composite spinel reinforced magnesium oxide foam ceramic filter of the invention has good thermal shock resistance.
  • the solid phase component of the aluminum sol is highly active porous ⁇ -Al 2 O 3 , which has the same crystal structure as the magnesium aluminate spinel MA.
  • the high-sintering active light-burning magnesium oxide particles are surrounded by a continuous nano-alumina sol film, and react in situ during the sintering to form a magnesium-aluminum spinel MA phase.
  • the solubility of Cr 2 O 3 in periclase MgO is greater than that of Al 2 O 3 , and the effective solubility of Cr 2 O 3 and Al 2 O 3 in periclase at about 1600 ° C is about 11% and 1%, respectively.
  • the magnesia powder in the ceramic powder has a wide contact surface with the aluminum sol and the nano-Cr 2 O 3 , and the diffusion rate of Cr 3+ into MgO is fast, so that the perician MgO spinel is petrified. At the same time, it promotes the diffusion of Al 2 O 3 into MgO.
  • MgAl 2 O 4 and MgCrO 4 formed by in-situ reaction and periclase solid solution.
  • MgAl 2 O 4 and MgCrO 4 have infinite mutual solubility, and MgO particles are directly combined with the surrounding Mg(Al,Cr) 2 O 4 composite spinel, and the pinning of the composite spinel phase inhibits oxidation.
  • the growth of magnesium particles refines the structure of the foamed ceramic and increases the density between the ceramic grains. Therefore, the prepared Mg(Al,Cr) 2 O 4 composite spinel reinforced magnesium oxide foam ceramic filter has Higher mechanical properties.
  • the composite spinel solid solution usually exists in the interlayer between the periclase crystals, which can compensate the stress at the interface of each phase, relax the thermal stress generated during the cooling process, and prevent the crack from expanding, thus improving the
  • the prepared ceramic foam filter material is resistant to high temperature shock and thermal shock resistance.
  • the polyurethane foam template is roughened by NaOH etching, and after being treated by the aqueous solution of the dodecylbenzenesulfonate wetting agent, the ceramic slurry is easily uniformly applied to the polyurethane foam template.
  • cellulose ether and polyvinyl butyral as rheological agents are not only good dispersants of nano-chromium oxide powder, but also prevent agglomeration of the slurry, and can be sticky when preparing the green body.
  • the slurry after the impregnation, the slurry can be relatively firmly adhered to the polyurethane foam template to make the green body have great strength, and at the same time, it is easy to escape during the sintering process without polluting the product, thereby ensuring the foam ceramic filter. quality.
  • 1 is a flow chart showing the preparation process of a Mg(Al,Cr) 2 O 4 composite spinel reinforced magnesium oxide based ceramic foam filter.
  • Mg(Al,Cr) 2 O 4 composite spinel reinforced magnesium oxide based foam ceramic filter coating light burned magnesium oxide based ceramic slurry containing nano chromia trioxide sintering aid on polyurethane foam carrier Dry and sintered.
  • the specific preparation process is shown in Figure 1.
  • nanometer chromium oxide 1% of the mass of the ceramic powder
  • nanometer chromium oxide having a particle diameter of 30 nm and light burned magnesium oxide powder having a particle diameter of 250 mesh medium diameter d 50 of 58 ⁇ m
  • the ceramic powder was mixed and prepared; and the rheological agent was mixed according to the ratio of the ratio of polyvinyl butyral to hydroxypropyl methylcellulose of 1:1.
  • the nano-alumina sol with a solid content of 25% is 25% (selecting a near-neutral commercial nano-aluminum sol with a pH value, the same below), the rheological agent is 0.8%, and the rest is a ceramic powder for compounding.
  • the lightly burned magnesia powder is added to the ball mill tank according to the ratio, and the nano aluminum sol, the nano chromium oxide, the rheological agent and the appropriate amount of absolute ethanol are determined according to the solid content of the ceramic slurry.
  • the nano cerium oxide powder is fully dispersed and added to the ball mill tank, and then the corundum ball is added in a ratio of 2:1 of the ball to the ball, and the mixture is uniformly milled at 60 rpm for 4 hours to obtain a solid content. 60% ceramic slurry.
  • 10PPI polyurethane foam stencil was selected, immersed in a 15% NaOH aqueous solution at 40 ° C for 60 min, washed with water and dried naturally, then immersed in an aqueous solution of 2% dodecylbenzenesulfonic acid wetting agent, and taken out dry. . Then, the polyurethane foam stencil is immersed in the ceramic slurry, the polyurethane foam stencil is pressed by a roller press to remove the excess immersion slurry, and then the green body is formed, and then the ethanol solvent is removed in a ventilating chamber at 40 ° C to dry the green body. The ethanol solvent can be recovered by a recovery unit.
  • the dried green body is placed in a sintering furnace and heated to 550 ° C at a heating rate of 30 ° C / h to decompose and vaporize the organic foam such as polyurethane foam and rheological agent in the ceramic foam filter, and then at 200 ° C /
  • the heating rate of h was heated to a temperature of 1100 ° C, and finally heated to a temperature of 1550 ° C at a heating rate of 50 ° C / h and held at this temperature for 2.5 h, and cooled to room temperature with a furnace to obtain a magnesium oxide based ceramic foam filter.
  • nanometer chromium oxide According to the ratio of nanometer chromium oxide to 2% of the mass of the ceramic powder, nanometer chromium oxide having a particle diameter of 60 nm and light burned magnesium oxide powder having a particle diameter of 500 mesh (medium diameter d 50 of 25 ⁇ m)
  • the ceramic powder was mixed and prepared; and the rheological agent was mixed according to the ratio of the ratio of polyvinyl butyral to hydroxypropyl methylcellulose of 1:1.
  • the nano-alumina sol with a solid content of 20% was 15%
  • the rheological agent was 1.5%
  • the rest was made of ceramic powder.
  • the lightly burned magnesia powder was added to the ball mill tank according to the ratio, and the nano-alumina sol, the nano-chromium oxide, the rheological agent and the appropriate amount of absolute ethanol were mixed and sonicated for 60 min to fully disperse the nano-cerium oxide powder.
  • the corundum ball was added in a ratio of 2:1 of the ball to the ball, and ball-milled at 120 rpm for 2 hours to obtain a ceramic slurry having a solid content of 65%.
  • 20PPI polyurethane foam stencil was used, soaked in a 20% NaOH aqueous solution at 50 °C for 40 min, washed with water and dried naturally, then immersed in an aqueous solution of 4% dodecylbenzenesulfonic acid wetting agent, and taken out dry. . Then, the polyurethane foam stencil is dipped into the ceramic slurry, and the polyurethane foam stencil is pressed by a roll press to remove the excess immersion slurry to form a green body, and then the ethanol solvent is removed in a ventilating chamber at 50 ° C to dry the green body.
  • the dried green body is placed in a sintering furnace and heated to 550 ° C at a heating rate of 30 ° C / h to decompose and vaporize the organic foam such as polyurethane foam and rheological agent in the ceramic foam filter, and then at 200 ° C /
  • the heating rate of h was heated to a temperature of 1100 ° C, and finally heated to a temperature of 1350 ° C at a heating rate of 50 ° C / h and held at this temperature for 3 h, and cooled to room temperature with a furnace to obtain a magnesia-based ceramic foam filter.
  • nanometer chromium oxide According to the ratio of nanometer chromium oxide to 1.5% of the mass of the ceramic powder, nanometer chromium oxide having a particle diameter of 50 nm and light burned magnesium oxide powder having a particle diameter of 325 mesh (medium diameter d 50 of 45 ⁇ m)
  • the ceramic powder is mixed and prepared; and the rheological agent is mixed according to the ratio of the ratio of polyvinyl butyral to hydroxyethyl cellulose of 1:1.
  • the nano-alumina sol with a solid content of 22% was 20%
  • the rheological agent was 1.0%
  • the rest was made of ceramic powder.
  • the light-burned magnesia powder was added to the ball mill tank according to the ratio, and the nano-alumina sol, the nano-chromium oxide, the rheological agent and the appropriate amount of absolute ethanol were mixed and sonicated for 45 minutes to fully disperse the nano-cerium oxide powder.
  • the corundum ball was added in a ratio of 2:1 of the ball to the ball, and ball-milled at 90 rpm for 3 hours to obtain a ceramic slurry having a solid content of 70%.
  • 15PPI polyurethane foam stencil was selected, immersed in a 15% NaOH aqueous solution at 45 ° C for 50 min, washed with water and dried naturally, then immersed in an aqueous solution of 3% dodecylbenzenesulfonic acid wetting agent, and taken out dry. . Then, the polyurethane foam stencil is dipped into the ceramic slurry, and the polyurethane foam stencil is pressed by a roll press to remove the excess immersion slurry to form a green body, and then the ethanol solvent is removed in a ventilating chamber at 45 ° C to dry the green body.
  • the dried green body is placed in a sintering furnace and heated to 550 ° C at a heating rate of 30 ° C / h to decompose and vaporize the organic foam such as polyurethane foam and rheological agent in the ceramic foam filter, and then at 200 ° C /
  • the heating rate of h was heated to a temperature of 1100 ° C, and finally heated to a temperature of 1450 ° C at a heating rate of 50 ° C / h and held at this temperature for 2 h, and cooled to room temperature with a furnace to obtain a magnesium oxide based ceramic foam filter.
  • nanometer chromium oxide According to the ratio of nanometer chromium oxide to 1% of the mass of the ceramic powder, nanometer chromium trioxide having a particle diameter of 60 nm and light burned magnesium oxide powder having a particle diameter of 300 mesh (medium diameter d 50 of 48 ⁇ m)
  • the ceramic powder is mixed and prepared; and the rheological agent is mixed according to the ratio of polyvinyl butyral: hydroxypropyl methylcellulose: hydroxyethyl cellulose in a mass ratio of 5:2:3.
  • the nano-alumina sol with a solid content of 20% was 25%
  • the rheological agent was 1.0%
  • the rest was made of ceramic powder.
  • the light-burned magnesia powder was added to the ball mill tank according to the ratio, and the nano-alumina sol, the nano-chromium oxide, the rheological agent and the appropriate amount of absolute ethanol were mixed and sonicated for 45 minutes to fully disperse the nano-cerium oxide powder.
  • the corundum ball was added in a ratio of 2:1 of the ball to the ball, and ball-milled at 100 rpm for 3 hours to obtain a ceramic slurry having a solid content of 65%.
  • 15PPI polyurethane foam stencil was selected, immersed in a 15% NaOH aqueous solution at 45 ° C for 50 min, washed with water and dried naturally, then immersed in an aqueous solution of 4% dodecylbenzenesulfonic acid wetting agent, and taken out dry. . Then, the polyurethane foam stencil is dipped into the ceramic slurry, and the polyurethane foam stencil is pressed by a roll press to remove the excess immersion slurry to form a green body, and then the ethanol solvent is removed in a ventilating chamber at 45 ° C to dry the green body.
  • the dried green body is placed in a sintering furnace and heated to 550 ° C at a heating rate of 30 ° C / h to decompose and vaporize the organic foam such as polyurethane foam and rheological agent in the ceramic foam filter, and then at 200 ° C /
  • the heating rate of h was heated to a temperature of 1100 ° C, and finally heated to a temperature of 1500 ° C at a heating rate of 50 ° C / h and held at this temperature for 2 h, and cooled to room temperature with a furnace to obtain a magnesium oxide based ceramic foam filter.

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Abstract

一种Mg(Al,Cr) 2O 4复合尖晶石增强氧化镁基泡沫陶瓷过滤器及其制备方法，该方法包括以下步骤：（1）按照质量百分比将15%~25%纳米铝溶胶，0.8%~1.5%流变剂，其余为含纳米三氧化二铬烧结助剂的氧化镁陶瓷粉料进行配料，添加无水乙醇球磨混合均匀后制成固含量为60%~70%的陶瓷浆料；（2）将聚氨酯泡沫塑料模版浸入到陶瓷浆料中，通过辊压机挤压聚氨酯泡沫塑料模版去除多余的浸挂浆料后制成素坯，然后在40℃~50℃通风室去除乙醇溶剂使素坯干燥；（3）将干燥的素坯放入烧结炉内，升温至1350℃~1550℃温度下进行高温烧结，随炉冷却至室温得到氧化镁基泡沫陶瓷过滤器。

Description

一种Mg(Al,Cr) 2O 4复合尖晶石增强氧化镁基泡沫陶瓷过滤器及其制备方法 技术领域
本发明涉及一种氧化镁基泡沫陶瓷过滤器及其制备方法，具体是一种Mg(Al,Cr) 2O 4复合尖晶石增强氧化镁基泡沫陶瓷过滤器及其制备方法，属于金属材料与冶金领域。本发明所制备的过滤器特别适用于镁及其合金熔体的过滤净化，亦可以用于铝及其合金熔体的过滤净化。
背景技术
镁的化学性质活泼，在铸造及加工过程中，极易与氧、氮及水蒸气发生化学反应，生成的产物残留在镁中，影响制品的内部质量，恶化制品性能。根据镁合金中夹杂物的种类和性质，一般将夹杂物分为金属夹杂和非金属夹杂两大类：(1)金属夹杂物：镁合金在原镁生产和后期加工过程中，会不可避免的引入一些金属单质或者金属化合物夹杂，它们以粒子状、簇状等形态残留在镁合金的基体或者晶界上，主要包括金属单质α-Fe粒子、锰-铁的金属化合物如(Fe,Mn) 3Si，(Fe,Mn) 5Si 3等；(2)非金属夹杂物：镁合金中的非金属夹杂物主要以镁的氮氧化合物为主，如MgO，Mg 3N 2等；镁合金在熔炼过程中添加以氯化物(KCl、NaCl、MgCl 2等)为主的精炼剂，精炼过程中熔剂不能完全去除，会有少量的熔剂残留在镁熔体中，造成镁金属熔剂夹杂。悬浮的氧化夹杂在结晶时由结晶前沿被推向晶界，夹杂物一般以薄膜状、粒子状、簇状的形态残留在镁合金晶界处。有统计资料表明，MgO占镁合金的所有夹杂物的80％以上，分布形态为薄膜状、粒子状及簇状。镁合金熔铸过程中产生的夹杂物不仅严重恶化合金的力学性能和耐蚀性能，而且降低了其机加工和阳极氧化处理的表面质量。对于压铸镁合金而言，其合金内部的薄膜状和粒子状氧化物的含量需要控制在100cm 2/kg和100mm 3/kg以下才能满足正常的使用要求。因此，在熔铸过程中去除镁熔体中的夹杂物以提高熔体的纯净度的净化工艺成为镁合金生产的关键。
熔体净化工艺可分为熔剂净化与非熔剂净化两大类。熔剂净化工艺因除杂效率高、成本低、操作方便而成为镁合金生产中普遍采用的净化工艺，但 是熔剂净化也存在着金属损耗增加、熔剂夹杂、不能除气等不足，尤其是在熔炼稀土镁合金时，熔剂还会大量消耗合金中的稀土元素。非熔剂净化工艺不但能弥补熔剂净化工艺的不足而且具有优异的净化效果，成为目前应用发展的重要熔体净化工艺并相继开发了过滤净化、旋转喷吹净化、电磁净化、超声波处理等多种非熔剂净化技术。相比简单的金属网熔体过滤，具有特殊的三维多孔陶瓷结构泡沫陶瓷过滤器，因其孔隙率高(70％～90％)、吸附能力强、耐化学腐蚀等特点，能够通过滤饼效应、吸附效应及整流效应对合金熔体中的夹杂物颗粒具有很好的过滤效果。泡沫陶瓷过滤法不但可以滤掉合金熔体中小至10μm～20μm的微细夹杂物颗粒,而且能过滤掉一般过滤介质难以滤除的液态熔剂夹杂。
美国专利文献US3962081A(Ceramic foam filter)，US4024212A(Ceramic foam and method of preparation)，中国专利文献CN103787691A(一种氧化铝泡沫陶瓷的制备方法)等都公开了一些用于铝合金、钢铁熔体过滤夹杂物的Al 2O 3，ZrO 2，SiC、SiO 2基泡沫陶瓷的方法，然而，MgO的标准生成自由焓很低，活性很高的镁熔体非常容易与泡沫陶瓷基体材料发生(1)～(4)式反应而迅速溶解，从而堵塞其过滤孔隙或熔蚀进入镁及其合金熔体内成为有害成分，因此，这些现有材质的泡沫过滤器并不适合于镁和镁合金熔体的过滤。
3Mg (l)+Al 2O 3(s)＝3MgO (s)+2Al (l)   (1)
2Mg(l)+ZrO 2(s)＝2MgO(s)+Zr(s)  (2)
6Mg(l)+4Al(l)+3SiC(s)＝3Mg 2Si(s)+Al 4C 3(s)  (3)
4Mg(l)+SiO 2(s)＝2MgO(s)+Mg 2Si(s)   (4)
MgO为立方晶系NaCl型结构，晶格常数为0.411nm，属于离子键化合物，其熔点为2852℃，远高于常用的Al 2O 3(2054℃)和SiO 2(1650±50℃)，因此，氧化镁制品具有良好的化学稳定性、高的电阻率以及对金属、熔渣和碱性溶液有较强的抗侵蚀能力等特性。与常用的陶瓷材料相比，MgO与镁及其合金熔体具有很好的高温化学稳定性，与熔融的氯盐和氟酸盐组成的熔剂夹渣不发生反应，并且与熔剂夹杂润湿角较小而容易吸附镁熔体中的熔剂夹杂，因此，MgO材质泡沫陶瓷是镁合金液熔炼净化的理想材料。
在低于氧化物组成的熔点温度之下进行烧成是制备陶瓷材料所必须的、最关键的步骤，而在高温下所发生的烧结、晶粒长大等过程决定着陶瓷材料的显微组织和性能。中国专利文献CN1011306B(纯氧化镁泡沫陶瓷过滤器及其制取工艺)、CN101138691A(铸造用镁质泡沫陶瓷过滤器的制备方法)等以纯氧化镁为原料制备泡沫陶瓷，因MgO具有很高的熔点和热膨胀系数(13.5×10 -6/℃)高，因此，导致其烧结困难(烧结温度不低于其熔点的0.8倍)和抗热震性较差，限制了MgO泡沫陶瓷的应用与发展。
研究表明：在烧结陶瓷过程中烧成温度每降低100℃，单位产品热耗会降低10％以上，通过添加烧结助剂是降低MgO泡沫陶瓷烧结温度的重要技术手段。添加V 2O 5粉体时，MgO在1190℃时会与V 2O 5形成近似组成为Mg 3V 2O 8的液相，促进烧结，能够显著降低MgO泡沫陶瓷的烧结温度，但是V 2O 5在使用过程中对呼吸系统和皮肤有损害作用，对操作有严格的限制。与V 2O 5相同，氧化钴也是良好的低温烧结助剂，但作为高毒物质和稀有资源也限制了应用。氟化物是陶瓷工业烧结中常用的强助溶剂和矿化剂，中国专利文献CN100536986C(氧化镁质泡沫陶瓷过滤器)、CN1473947A(镁和镁合金熔体净化用泡沫陶瓷)、CN101785944B(用于镁和镁熔体过滤用氧化镁泡沫陶瓷过滤器的制备方法)中添加萤石(熔点1423℃)及氟化镁(熔点1248℃)，在烧结过程中氟化物的固溶不仅增大了基体氧化镁的晶格畸变，而且本身易形成低熔点液相，从而降低氧化镁陶瓷的烧结温度；然而，在烧结过程中氟化物中的F与Si、Al、Fe、Ca结合，大部分(在瓷砖生产中约占70％)以气态形式挥发不仅本身侵蚀坯体而损害烧结陶瓷的质量，更为严重的是排放到大气中会造成氟化物污染，氟化物可经呼吸道、消化道及皮肤进入人体，对中枢神经系统、心肌有毒性作用，低浓度氟污染会导致牙齿和骨骼脆钙化，《陶瓷工业污染物排放标准》(GB25464-2010)中规定氟化物的排放标准必须低于5.0mg/m 3，以氟化物作为氧化镁陶瓷的低温烧结助剂必然增加气态氟化物的排放并加重环保投入负担；另外，陶瓷中残留的固溶氟化物中氟离子是以取代氧离子的形式存在，造成晶粒间结合的化学稳定性降低，难以抵抗镁熔体中熔剂夹杂的长时间侵蚀。中国专利文献CN101138691A等公开的泡沫陶瓷过滤器的制备浆料中采用水玻 璃、硅溶胶及硅酸乙酯作为粘接剂，烧结的泡沫陶瓷颗粒间SiO 2成分的存在，使其易与镁及其合金熔体按(4)式反应，同样降低了泡沫陶瓷的化学稳定性。中国专利文献CN100536986C(氧化镁质泡沫陶瓷过滤器)、CN103553686A(一种镁铝尖晶石质泡沫陶瓷过滤器及其制备方法)等专利文献中，三氧化二硼及硼砂作为氧化镁陶瓷的低温烧结助剂，三氧化二硼高于450℃时即形成液相，在烧结温度超过1350℃时，与氧化镁反应生成硼酸镁以液相形式存在而降低了烧结温度。然而，三氧化二硼易与镁、铝反应，在镁、铝合金熔体中并不稳定；同时，由于三氧化二硼溶于水和乙醇等溶剂，在空气中可强烈地吸水生成硼酸，在泡沫陶瓷的制备过程中添加的三氧化二硼溶于水形成硼酸水溶液，易与氧化镁反应形成硼酸镁沉淀而降低其作用。氧化镓是三氧化二硼的同族氧化物，在较低的温度下与氧化镁形成尖晶石型的MgGa 2O 4而起到降低烧结温度的作用，但镓资源量很少(镓是战略储备金属)，氧化镓较高的价格限制了其在普通陶瓷中的应用。
发明内容
本发明的目的是提供一种能在低温下实现烧结的、化学稳定性和抗热震性优异的Mg(Al,Cr) 2O 4复合尖晶石增强氧化镁基泡沫陶瓷过滤器及其制备方法。
为了达到上述技术目的，本发明的技术方案是：
一种Mg(Al,Cr) 2O 4复合尖晶石增强氧化镁基泡沫陶瓷过滤器，将含纳米三氧化二铬烧结助剂的轻烧氧化镁基陶瓷浆料涂覆在聚氨酯泡沫载体上，经干燥、烧结得到。
一种Mg(Al,Cr) 2O 4复合尖晶石增强氧化镁基泡沫陶瓷过滤器的制备方法，包括以下步骤：
(1)按照质量百分比将15％～25％纳米铝溶胶，0.8％～1.5％流变剂，其余为含纳米三氧化二铬烧结助剂的氧化镁陶瓷粉料进行配料，添加无水乙醇球磨混合均匀后制成固含量为60％～70％的陶瓷浆料。加入的纳米铝溶胶不仅能够起到粘结剂的作用，而且与高度均匀分散到氧化镁粉体颗粒中的纳米Cr 2O 3一起与MgO原位反应生成对镁及其合金熔体具有化学稳定性的Mg(Al,Cr) 2O 4复 合尖晶石相，避免了现有产品加入硅溶胶、硅酸乙酯等粘结剂对泡沫陶瓷化学稳定性的损害。
所述流变剂为聚乙烯醇缩丁醛和纤维素醚的混合物，其中所述聚乙烯醇缩丁醛占流变剂质量的50％，所述纤维素醚为工业用羟丙基甲基纤维素、羟乙基纤维素中的一种或其混合物。纤维素醚和聚乙烯醇缩丁醛不但是纳米三氧化二铬粉体的良好分散剂，能够防止浆料产生团聚现象，而且在制备素坯时能起到粘接剂的作用，浸渍后浆料能比较地牢固附着在聚氨酯泡沫模板上使素坯具有很大的强度，同时在烧结过程中极易逸出而不污染制品。流变剂中不采用羧甲基纤维素钠等含纳的盐类，避免了残留的离子半径较大的Na +对陶瓷烧结的阻碍，也避免了Cr 2O 3在碱性氧化物Na 2O、K 2O存在时Cr 3+转化为对人类健康有严重危害的Cr 6+所带来的环保问题。
所述陶瓷粉料为轻烧氧化镁和纳米三氧化二铬的混合物。其中，所述纳米三氧化二铬占陶瓷粉料质量的1％～2％，所述纳米三氧化二铬的粒径为30～60nm。所述轻烧氧化镁粉体的粒径为250目～500目(中径d 50为25μm～58μm)。
采用的轻烧氧化镁细粉本身具有很高的烧结活性，纳米铝溶胶和纳米三氧化二铬在烧结过程中能够固溶到MgO晶格中使MgO晶体发生晶格畸变，活化晶格，同时通过与MgO颗粒间反应烧结生成Mg(Al,Cr) 2O 4复合尖晶石相相，从而促进了烧结和颗粒相间的结合。另一方面，纳米粉体具有比表面积大、表面能高、高活性等特点，以纳米铝溶胶和纳米三氧化二铬的形式加入低温烧结助剂，优化陶瓷颗粒级配和混合均匀性，同时纳米粉体因其自身的表面和界面效应，纳米烧结助剂与MgO颗粒间的充分接触使生成尖晶石相的反应速度迅速提高，从而进一步降低了烧结温度，而烧结温度的降低有利于降低能耗和泡沫陶瓷过滤器的生产成本。
加入纳米Cr 2O 3，陶瓷粉料中氧化镁细粉与铝溶胶及纳米Cr 2O 3之间有着广泛的接触面，Cr 3+向MgO中扩散速度快，使方镁石MgO尖晶石化，同时还有促进Al 2O 3向MgO中扩散的作用，因此，原位反应生成的MgAl 2O 4和MgCrO 4与方镁石固溶体间有紧密连续的结合界面。MgAl 2O 4与MgCrO 4具有无限互溶 性，MgO颗粒与周围形成的Mg(Al,Cr) 2O 4复合尖晶石相直接结合在一起，同时复合尖晶石相的钉扎作用抑制了氧化镁颗粒的生长，从而细化了泡沫陶瓷的组织并提高了陶瓷晶粒间的致密度，因此，所制备的Mg(Al,Cr) 2O 4复合尖晶石增强氧化镁泡沫陶瓷过滤器具有较高的力学性能。另一方面，在烧成时离子交换扩散合成了尖晶石固溶体，由于Al 3+扩散速度比Mg 2+和Cr 3+慢，使氧化镁颗粒和MgO/复合尖晶石结合基质之间的界面上产生了Al 2O 3的浓度梯度，同时，又由于它们的热膨胀系数不同便导致氧化镁颗粒和MgO/复合尖晶石结合基质之间的界面处产生了裂隙。同时，复合尖晶石固溶体通常呈夹层存在于方镁石晶体之间，它可以补偿各相界面上的应力，使冷却过程中产生的热应力得到松弛，并阻止裂纹的扩展。
作为优选，所述纳米铝溶胶固含量为20％～25％，其PH值≥4。
所述陶瓷浆料的制备方法为：按照配比将轻烧氧化镁粉料加入球磨罐中，将纳米铝溶胶、纳米三氧化二铬、流变剂及无水乙醇混合并超声处理30min～60min，使纳米氧化镧粉体充分分散后加入到球磨罐内，再按照球料比2:1的比例加入刚玉球，以60～120rpm转速球磨2h～4h使其混合均匀得到。通过NaOH刻蚀使其表面粗糙化，再通过十二烷基苯磺酸盐润湿剂的水溶液处理后，陶瓷浆料易于均匀涂挂到聚氨酯泡沫模板上。
(2)将聚氨酯泡沫塑料模版浸入到陶瓷浆料中，通过辊压机挤压聚氨酯泡沫塑料模版去除多余的浸挂浆料后制成素坯，然后在40℃～50℃通风室去除乙醇溶剂使素坯干燥。
所述聚氨酯泡沫塑料模版规格为10PPI～20PPI(Pores per inch，单位英寸长度上的平均孔数)；使用前在40℃～50℃的15％～20％NaOH水溶液中浸泡表面刻蚀40min～60min后用清水洗涤自然晾干，然后浸入到2％～4％十二烷基苯磺酸润湿剂的水溶液中后取出干燥后得到。通过NaOH刻蚀使其表面粗糙化，再通过十二烷基苯磺酸盐润湿剂的水溶液处理后，陶瓷浆料易于均匀涂挂到聚氨酯泡沫模板上。
(3)将干燥的素坯放入烧结炉内，升温至1350℃～1550℃温度下进行高温烧结，随炉冷却至室温得到氧化镁基泡沫陶瓷过滤器。
所述烧结工艺是以30℃/h的升温速度加热至550℃使泡沫陶瓷过滤器素坯内的有机物(聚氨酯泡沫及流变剂等)分解气化排出，然后以200℃/h的升温速度加热至1100℃温度，在低温烧结阶段，较低的升温速度可以防止聚氨酯泡沫及流变剂分解速度过快导致素坯塌陷或变形损坏。最后以50℃/h的升温速度加热至1350℃～1550℃温度并在该温度下保温2～3h。在高温烧结阶段，烧结温度超过1100℃后，较低的升温速度可以保证烧结体内的温度一致，同时避免生成尖晶石的生成速度均匀并且避免过快产生的相变应力造成烧结体变形和开裂。
本发明所提供的氧化镁基泡沫陶瓷过滤器的制备方法具有工艺简单、成本低、效率高、适合规模化生产等优点，所制备的氧化镁基泡沫陶瓷过滤器不含任何降低其化学稳定性的组分，所加入的纳米铝溶胶和纳米三氧化二铬不仅能够起到降低烧结温度的作用，而且高度均匀分散到氧化镁陶瓷粉体颗粒中并与之反应生成对镁及其合金熔体具有化学稳定性的Mg(Al,Cr) 2O 4复合尖晶石相将氧化镁颗粒熔接在一起，因此，泡沫陶瓷过滤器具有良好的强度、化学稳定性和抗热震性，特别适用于过滤净化镁及其合金熔体中的夹杂物，亦可用于铝及其合金熔体过滤净化。与现有的技术方案相比，本发明的技术效果：
一、本发明的Mg(Al,Cr) 2O 4复合尖晶石增强氧化镁泡沫陶瓷过滤器具有优异的化学稳定性。铬离子半径比镁离子半径小，Cr 2O 3具有α-Al 2O 3结构，在方镁石MgO中的固溶度比Al 2O 3大。添加的纳米Cr 2O 3极易向MgO相内固溶扩散，通过反应烧结生成具有高温稳定性的镁铬尖晶石(MgCr 2O 4)相(熔点2180℃)。虽然原料组分铝溶胶中含有与镁液反应的Al 2O 3，但添加的纳米铝溶胶在轻烧氧化镁颗粒及高度均匀分散的纳米Cr 2O 3粉体表面形成γ-Al 2O 3包覆膜，在烧结过程中和MgO原位反应生成具有面心立方晶格的高熔点镁铝尖晶石(MgAl 2O 4)相(熔点2135℃)。MgAl 2O 4与MgCrO 4可以完全互溶，根据XRD分析结果表明，本发明所制备的泡沫陶瓷过滤器只有方镁石MgO和MgAl 2O 4-MgCr 2O 4复合尖晶石相。
在镁熔体与添加氧化铝的MgO-Al 2O 3烧结陶瓷的反应体系中，除存在反应式(1)外，还可能存在如下反应：
3Mg (l)+4Al 2O 3(s)＝3MgAl 2O 4(s)+2Al (l)   (5)
氧化铝与氧化镁生成镁铝尖晶石MgAl 2O 4的反应为：
MgO (s)+Al 2O 3(s)＝MgAl 2O 4(s)   (6)
镁熔体与镁铝尖晶石MgAl 2O 4发生的反应为：
3Mg (l)+MgAl 2O 4(s)＝2Al (l)+4MgO (s)   (7)
根据《纯物质热化学数据手册》(伊赫桑·巴伦主编，程乃良等译，北京：科学出版社，2003年)，在900～1200K时镁熔体与镁铝尖晶石反应体系的物质Gibbs自由能数据和反应(1)、(5)、(6)和(7)的Gibbs自由能变化ΔG 1、ΔG 5、ΔG 6、ΔG 7的计算结果如表1所示。
表1 在900～1200K镁熔体与镁铝尖晶石反应体系中各个反应的吉布斯自由能变化ΔG计算结果
Figure PCTCN2018089568-appb-000001
反应式镁熔体与氧化铝生成镁铝尖晶石的(5)式的Gibbs自由能ΔG 5在不同温度下均最小，说明在镁合金的常用熔炼温度下该反应会优先发生。镁液与镁铝尖晶石的反应式(7)尽管从热力学上是可以进行的，但该反应本质上为镁液与镁铝尖晶石的分解产物氧化铝间反应，但由表1可知，在镁合金的熔炼温度下，镁铝尖晶石分解为氧化铝和氧化镁的反应难以进行(反应式(6)的逆反应)，同时烧结的陶瓷中残留的氧化铝也会与镁液优先按反应式(5)生成镁铝尖晶石；另一方面，MgO-Al 2O 3相图中MgO一侧为方镁石固溶体和MA尖晶石固溶体共晶相图，在原位反应生成MA过程中几乎没有O 2-扩散，只有Mg 2+和Al 3+通过固定的氧晶格相互扩散，其生成速度由扩散较慢的Al 3+所决定，MA相主要在Al 2O 3一侧通过内延生长方式生成，导致在MA相与MgO间形成有限固溶体，同时与MgO颗粒接触的MA外层中MgO含量远高于其平均值，而 MgO并不与镁熔体反应，因此，烧结陶瓷组织中将氧化镁颗粒熔接在一起的镁铝尖晶石相在镁熔体中是能够稳定存在。
本发明的Mg(Al,Cr) 2O 4复合尖晶石氧化镁泡沫陶瓷过滤器中不含任何降低其化学稳定性的组分，加入的纳米铝溶胶不仅能够起到粘结剂的作用，而且与高度均匀分散到氧化镁粉体颗粒中的纳米Cr 2O 3一起与MgO原位反应生成对镁及其合金熔体具有化学稳定性的Mg(Al,Cr) 2O 4复合尖晶石相，避免了现有产品加入硅溶胶、硅酸乙酯等粘结剂对泡沫陶瓷化学稳定性的损害；同时，陶瓷组分中亦不含钠盐(如流变剂中不采用羧甲基纤维素钠)，避免了残留的离子半径较大的Na +对陶瓷烧结的阻碍，也避免了Cr 2O 3在碱性氧化物Na 2O、K 2O存在时Cr 3+转化为对人类健康有严重危害的Cr 6+所带来的环保问题。
因反应式(1)、(5)在镁合金的常用熔炼温度下能够自发进行，而铝及其合金的熔炼温度与镁及其合金熔炼温度相同，MgO和MA尖晶石相与铝及其合金熔体不会发生反应式(1)、(5)的逆反应；与用于镁及其合金熔体相同，避免了加入硅溶胶、硅酸乙酯等粘结剂对泡沫陶瓷在铝及其合金熔体中化学稳定性的损害(即使材质中含有1％的SiO 2，铝及其合金熔体在高温下也会和陶瓷中SiO 2发生Al+SiO 2→Al 2O 3+Si的反应)；因此，所制备的Mg(Al,Cr) 2O 4复合尖晶石氧化镁泡沫陶瓷过滤器亦可以用于铝及其合金的熔炼净化。
二、本发明的Mg(Al,Cr) 2O 4复合尖晶石增强氧化镁泡沫陶瓷过滤器具有良好的低温烧结性能。本发明所采用的轻烧氧化镁细粉本身具有很高的烧结活性，纳米铝溶胶和纳米三氧化二铬在烧结过程中能够固溶到MgO晶格中使MgO晶体发生晶格畸变，活化晶格，同时通过与MgO颗粒间反应烧结生成Mg(Al,Cr) 2O 4复合尖晶石相相，从而促进了烧结和颗粒相间的结合。另一方面，纳米粉体具有比表面积大、表面能高、高活性等特点，以纳米铝溶胶和纳米三氧化二铬的形式加入低温烧结助剂，优化陶瓷颗粒级配和混合均匀性，同时纳米粉体因其自身的表面和界面效应，纳米烧结助剂与MgO颗粒间的充分接触使生成尖晶石相的反应速度迅速提高，从而进一步降低了烧结温度，而烧结温度的降低有利于降低能耗和泡沫陶瓷过滤器的生产成本。试验结果表明，烧结温度低于1350℃时氧化镁颗粒间烧结组织结合不够充分致使其强度偏低，组织结 合良好的Mg(Al,Cr) 2O 4复合尖晶石增强氧化镁泡沫陶瓷过滤器的烧结温度为1350℃～1550℃。
三、本发明的Mg(Al,Cr) 2O 4复合尖晶石增强氧化镁泡沫陶瓷过滤器具有良好的抗热震性。铝溶胶中固相成分为高活性的多孔γ-Al 2O 3，与镁铝尖晶石MA晶体结构相同。在本发明所提供的方案中，高烧结活性的轻烧氧化镁颗粒被连续的纳米铝溶胶膜包围，在烧结过程中原位反应生成镁铝尖晶石MA相。Cr 2O 3在方镁石MgO中的溶解度大于Al 2O 3，1600℃时Cr 2O 3和Al 2O 3在方镁石中的有效溶解度大约分别为11％和1％。加入纳米Cr 2O 3，陶瓷粉料中氧化镁细粉与铝溶胶及纳米Cr 2O 3之间有着广泛的接触面，Cr 3+向MgO中扩散速度快，使方镁石MgO尖晶石化，同时还有促进Al 2O 3向MgO中扩散的作用，因此，原位反应生成的MgAl 2O 4和MgCrO 4与方镁石固溶体间有紧密连续的结合界面。MgAl 2O 4与MgCrO 4具有无限互溶性，MgO颗粒与周围形成的Mg(Al,Cr) 2O 4复合尖晶石相直接结合在一起，同时复合尖晶石相的钉扎作用抑制了氧化镁颗粒的生长，从而细化了泡沫陶瓷的组织并提高了陶瓷晶粒间的致密度，因此，所制备的Mg(Al,Cr) 2O 4复合尖晶石增强氧化镁泡沫陶瓷过滤器具有较高的力学性能。另一方面，在烧成时离子交换扩散合成了尖晶石固溶体，由于Al 3+扩散速度比Mg 2+和Cr 3+慢，使氧化镁颗粒和MgO/复合尖晶石结合基质之间的界面上产生了Al 2O 3的浓度梯度，同时，又由于它们的热膨胀系数不同便导致氧化镁颗粒和MgO/复合尖晶石结合基质之间的界面处产生了裂隙。同时，复合尖晶石固溶体通常呈夹层存在于方镁石晶体之间，它可以补偿各相界面上的应力，使冷却过程中产生的热应力得到松弛，并阻止裂纹的扩展，因此，提高了所制备的泡沫陶瓷过滤器材料的耐高温冲击和抗热震性。
此外，本发明制备方法中聚氨酯泡沫塑料模板通过NaOH刻蚀使其表面粗糙化，再通过十二烷基苯磺酸盐润湿剂的水溶液处理后，陶瓷浆料易于均匀涂挂到聚氨酯泡沫模板上；同时作为流变剂的纤维素醚和聚乙烯醇缩丁醛不但是纳米三氧化二铬粉体的良好分散剂，能够防止浆料产生团聚现象，而且在制备素坯时能起到粘接剂的作用，浸渍后浆料能比较地牢固附着在聚氨酯泡沫模板上使素坯具有很大的强度，同时在烧结过程中极易逸出而不污染制品，因 而保证了泡沫陶瓷过滤器的质量。
附图说明
图1为Mg(Al,Cr) 2O 4复合尖晶石增强氧化镁基泡沫陶瓷过滤器的制备工艺流程图。
具体实施方式
下面结合附图和具体实施方式对本发明作进一步详细的说明。
Mg(Al,Cr) 2O 4复合尖晶石增强氧化镁基泡沫陶瓷过滤器，将含纳米三氧化二铬烧结助剂的轻烧氧化镁基陶瓷浆料涂覆在聚氨酯泡沫载体上，经干燥、烧结得到。具体的制备工艺如图1所示。
实施例1
按照纳米三氧化二铬占陶瓷粉料质量的1％的配比，将粒径为30nm的纳米三氧化二铬和粒径为250目(中径d 50为58μm)的轻烧氧化镁粉体混合配制陶瓷粉料；按照聚乙烯醇缩丁醛和羟丙基甲基纤维素的质量比为1:1的比例混合配制流变剂。
按照质量百分比将固含量为25％的纳米铝溶胶25％(选择PH值近中性的商业化纳米铝溶胶，下同)，流变剂0.8％，其余为陶瓷粉料进行配料。首先按照配比将轻烧氧化镁粉料加入球磨罐中，将纳米铝溶胶、纳米三氧化二铬、流变剂及适量的无水乙醇(根据陶瓷浆料的固含量确定其加入量，下同)混合并超声处理30min，使纳米氧化镧粉体充分分散后加入到球磨罐内，再按照球料比2:1的比例加入刚玉球，以60rpm转速球磨4h使其混合均匀得到固含量为60％的陶瓷浆料。
选用10PPI聚氨酯泡沫塑料模版，在40℃的15％NaOH水溶液中浸泡表面刻蚀60min后用清水洗涤自然晾干，然后浸入到2％十二烷基苯磺酸润湿剂的水溶液中，取出干燥。然后将聚氨酯泡沫塑料模版浸入到陶瓷浆料中，通过辊压机挤压聚氨酯泡沫塑料模版去除多余的浸挂浆料后制成素坯，然后在40℃通风室去除乙醇溶剂使素坯干燥，乙醇溶剂可通过回收装置回收。
将干燥的素坯放入烧结炉内，以30℃/h的升温速度加热至550℃使泡沫陶瓷过滤器素坯内的聚氨酯泡沫及流变剂等有机物分解气化排出，然后以 200℃/h的升温速度加热至1100℃温度，最后以50℃/h的升温速度加热至1550℃温度并在该温度下保温2.5h，随炉冷却至室温得到氧化镁基泡沫陶瓷过滤器。
实施例2
按照纳米三氧化二铬占陶瓷粉料质量的2％的配比，将粒径为60nm的纳米三氧化二铬和粒径为500目(中径d 50为25μm)的轻烧氧化镁粉体混合配制陶瓷粉料；按照聚乙烯醇缩丁醛和羟丙基甲基纤维素的质量比为1:1的比例混合配制流变剂。
按照质量百分比将固含量为20％的纳米铝溶胶15％，流变剂1.5％，其余为陶瓷粉料进行配料。首先按照配比将轻烧氧化镁粉料加入球磨罐中，将纳米铝溶胶、纳米三氧化二铬、流变剂及适量的无水乙醇混合并超声处理60min，使纳米氧化镧粉体充分分散后加入到球磨罐内，再按照球料比2:1的比例加入刚玉球，以120rpm转速球磨2h使其混合均匀得到固含量为65％的陶瓷浆料。
选用20PPI聚氨酯泡沫塑料模版，在50℃的20％NaOH水溶液中浸泡表面刻蚀40min后用清水洗涤自然晾干，然后浸入到4％十二烷基苯磺酸润湿剂的水溶液中，取出干燥。然后将聚氨酯泡沫塑料模版浸入到陶瓷浆料中，通过辊压机挤压聚氨酯泡沫塑料模版去除多余的浸挂浆料后制成素坯，然后在50℃通风室去除乙醇溶剂使素坯干燥。
将干燥的素坯放入烧结炉内，以30℃/h的升温速度加热至550℃使泡沫陶瓷过滤器素坯内的聚氨酯泡沫及流变剂等有机物分解气化排出，然后以200℃/h的升温速度加热至1100℃温度，最后以50℃/h的升温速度加热至1350℃温度并在该温度下保温3h，随炉冷却至室温得到氧化镁基泡沫陶瓷过滤器。
实施例3
按照纳米三氧化二铬占陶瓷粉料质量的1.5％的配比，将粒径为50nm的纳米三氧化二铬和粒径为325目(中径d 50为45μm)的轻烧氧化镁粉体混合配制陶瓷粉料；按照聚乙烯醇缩丁醛和羟乙基纤维素的质量比为1:1的比例混合配制流变剂。
按照质量百分比将固含量为22％的纳米铝溶胶20％，流变剂1.0％，其余为陶瓷粉料进行配料。首先按照配比将轻烧氧化镁粉料加入球磨罐中，将 纳米铝溶胶、纳米三氧化二铬、流变剂及适量的无水乙醇混合并超声处理45min，使纳米氧化镧粉体充分分散后加入到球磨罐内，再按照球料比2:1的比例加入刚玉球，以90rpm转速球磨3h使其混合均匀得到固含量为70％的陶瓷浆料。
选用15PPI聚氨酯泡沫塑料模版，在45℃的18％NaOH水溶液中浸泡表面刻蚀50min后用清水洗涤自然晾干，然后浸入到3％十二烷基苯磺酸润湿剂的水溶液中，取出干燥。然后将聚氨酯泡沫塑料模版浸入到陶瓷浆料中，通过辊压机挤压聚氨酯泡沫塑料模版去除多余的浸挂浆料后制成素坯，然后在45℃通风室去除乙醇溶剂使素坯干燥。
将干燥的素坯放入烧结炉内，以30℃/h的升温速度加热至550℃使泡沫陶瓷过滤器素坯内的聚氨酯泡沫及流变剂等有机物分解气化排出，然后以200℃/h的升温速度加热至1100℃温度，最后以50℃/h的升温速度加热至1450℃温度并在该温度下保温2h，随炉冷却至室温得到氧化镁基泡沫陶瓷过滤器。
实施例4
按照纳米三氧化二铬占陶瓷粉料质量的1％的配比，将粒径为60nm的纳米三氧化二铬和粒径为300目(中径d 50为48μm)的轻烧氧化镁粉体混合配制陶瓷粉料；按照聚乙烯醇缩丁醛：羟丙基甲基纤维素：羟乙基纤维素的质量比为5:2:3的比例混合配制流变剂。
按照质量百分比将固含量为20％的纳米铝溶胶25％，流变剂1.0％，其余为陶瓷粉料进行配料。首先按照配比将轻烧氧化镁粉料加入球磨罐中，将纳米铝溶胶、纳米三氧化二铬、流变剂及适量的无水乙醇混合并超声处理45min，使纳米氧化镧粉体充分分散后加入到球磨罐内，再按照球料比2:1的比例加入刚玉球，以100rpm转速球磨3h使其混合均匀得到固含量为65％的陶瓷浆料。
选用15PPI聚氨酯泡沫塑料模版，在45℃的15％NaOH水溶液中浸泡表面刻蚀50min后用清水洗涤自然晾干，然后浸入到4％十二烷基苯磺酸润湿剂的水溶液中，取出干燥。然后将聚氨酯泡沫塑料模版浸入到陶瓷浆料中，通过辊压机挤压聚氨酯泡沫塑料模版去除多余的浸挂浆料后制成素坯，然后在45℃通风室去除乙醇溶剂使素坯干燥。
将干燥的素坯放入烧结炉内，以30℃/h的升温速度加热至550℃使泡 沫陶瓷过滤器素坯内的聚氨酯泡沫及流变剂等有机物分解气化排出，然后以200℃/h的升温速度加热至1100℃温度，最后以50℃/h的升温速度加热至1500℃温度并在该温度下保温2h，随炉冷却至室温得到氧化镁基泡沫陶瓷过滤器。
上述实施例中，实验表明所制备的泡沫陶瓷具有优异的抗热震性和强度，在900℃空气中冷却50次均未见开裂；75mm×75mm×25mm，10PPI的泡沫陶瓷过滤器的常温强度不低于2MPa。
上述实施例不以任何方式限制本发明，凡是采用等同替换或等效变换的方式获得的技术方案均落在本发明的保护范围内。

Claims (9)

  1. 一种Mg(Al,Cr) 2O 4复合尖晶石增强氧化镁基泡沫陶瓷过滤器，其特征在于：将含纳米三氧化二铬烧结助剂的轻烧氧化镁基陶瓷浆料涂覆在聚氨酯泡沫载体上，经干燥、烧结得到。
  2. 一种Mg(Al,Cr) 2O 4复合尖晶石增强氧化镁基泡沫陶瓷过滤器的制备方法，其特征在于：
    (1)按照质量百分比将15％～25％纳米铝溶胶，0.8％～1.5％流变剂，其余为含纳米三氧化二铬烧结助剂的氧化镁陶瓷粉料进行配料，添加无水乙醇球磨混合均匀后制成固含量为60％～70％的陶瓷浆料；所述流变剂为聚乙烯醇缩丁醛和纤维素醚的混合物，其中所述聚乙烯醇缩丁醛占流变剂质量的50％，所述纤维素醚为工业用羟丙基甲基纤维素、羟乙基纤维素中的一种或其混合物；所述陶瓷粉料为轻烧氧化镁和纳米三氧化二铬的混合物；
    (2)将聚氨酯泡沫塑料模版浸入到陶瓷浆料中，通过辊压机挤压聚氨酯泡沫塑料模版去除多余的浸挂浆料后制成素坯，然后在40℃～50℃通风室去除乙醇溶剂使素坯干燥；
    (3)将干燥的素坯放入烧结炉内，升温至1350℃～1550℃温度下进行高温烧结，随炉冷却至室温得到氧化镁基泡沫陶瓷过滤器。
  3. 根据权利要求2所述的一种Mg(Al,Cr) 2O 4复合尖晶石增强氧化镁基泡沫陶瓷过滤器的制备方法，其特征在于：所述纳米铝溶胶固含量为20％～25％，其PH值≥4。
  4. 根据权利要求2所述的一种Mg(Al,Cr) 2O 4复合尖晶石增强氧化镁基泡沫陶瓷过滤器的制备方法，其特征在于：所述纳米三氧化二铬占陶瓷粉料质量的1％～2％。
  5. 根据权利要求2所述的一种Mg(Al,Cr) 2O 4复合尖晶石增强氧化镁基泡沫陶瓷过滤器的制备方法，其特征在于：所述轻烧氧化镁粉体的粒径为250目～500目。
  6. 根据权利要求2所述的一种Mg(Al,Cr) 2O 4复合尖晶石增强氧化镁基泡沫 陶瓷过滤器的制备方法，其特征在于：所述纳米三氧化二铬的粒径为30～60nm。
  7. 根据权利要求2所述的一种Mg(Al,Cr) 2O 4复合尖晶石增强氧化镁基泡沫陶瓷过滤器的制备方法，其特征在于所述陶瓷浆料的制备方法为：按照配比将轻烧氧化镁粉料加入球磨罐中，将纳米铝溶胶、纳米三氧化二铬、流变剂及无水乙醇混合并超声处理30min～60min，使纳米氧化镧粉体充分分散后加入到球磨罐内，再按照球料比2:1的比例加入刚玉球，以60～120rpm转速球磨2h～4h使其混合均匀得到。
  8. 根据权利要求2所述的一种Mg(Al,Cr) 2O 4复合尖晶石增强氧化镁基泡沫陶瓷过滤器的制备方法，其特征在于：所述聚氨酯泡沫塑料模版规格为10PPI～20PPI；使用前在40℃～50℃的15％～20％NaOH水溶液中浸泡表面刻蚀40min～60min后用清水洗涤自然晾干，然后浸入到2％～4％十二烷基苯磺酸润湿剂的水溶液中后取出干燥后得到。
  9. 根据权利要求2所述的一种Mg(Al,Cr) 2O 4复合尖晶石增强氧化镁基泡沫陶瓷过滤器的制备方法，其特征在于在所述步骤(3)中，所述烧结工艺为：以30℃/h的升温速度加热至550℃使泡沫陶瓷过滤器素坯内的聚氨酯泡沫及流变剂等有机物分解气化排出，然后以200℃/h的升温速度加热至1100℃温度，最后以50℃/h的升温速度加热至1350℃～1550℃温度并在该温度下保温2～3h。
PCT/CN2018/089568 2018-04-08 2018-06-01 一种Mg(Al, Cr)2O4复合尖晶石增强氧化镁基泡沫陶瓷过滤器及其制备方法 WO2019196179A1 (zh)

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