JP5271766B2 - Porous ceramic member and filter - Google Patents

Description

  The present invention relates to a porous ceramic member and a filter, for example, a heat insulating material, a support member for a high temperature member, a honeycomb structure for an exhaust gas purification catalyst carrier for automobiles, and a honeycomb structure for particulate trap (particulate matter removal) for diesel engine automobiles. The present invention relates to a porous ceramic member and a filter that can be used for filter elements such as a honeycomb structure for consumer use such as a body, a deodorizing body, and a hot air body.

  Conventionally, low thermal expansion ceramic materials such as cordierite, β-eucryptite, β-spodumene lithium aluminosilicate (common name: LAS), and aluminum titanate have been used as a honeycomb structure of a thermal shock-resistant member.

In general, the low thermal expansion ceramic material is a ceramic having a thermal expansion coefficient of 20 ° C. to 800 ° C. of 3.0 × 10 ⁻⁶ / ° C. or less. These low thermal expansion ceramic materials have long been used as materials resistant to thermal shock. Recently, it has been used as a material for parts requiring particularly thermal shock resistance, such as honeycomb carriers for exhaust gas purification catalysts of automobiles, ceramic gas turbine housings and heat exchangers.

Cordierite (2MgO · 2Al ₂ O ₃ · 5SiO ₂ ) has excellent thermal shock resistance and has been put to practical use as a honeycomb carrier for exhaust gas purification catalysts for automobiles.

  However, since cordierite has a high heat resistance temperature of about 1350 ° C., it is difficult to use it above this temperature.

On the other hand, aluminum titanate (Al ₂ TiO ₅ ) is a low thermal expansion ceramic material having a high melting point of 1860 ° C. and higher heat resistance than cordierite, but when kept at a temperature of 900 ° C. to 1200 ° C., alumina There was a problem of thermal decomposition to titania, and there was a limit to its use.

Therefore, in order to improve the thermal decomposition resistance with respect to such an aluminum titanate, Al ₂ O ₃ powder, TiO ₂ powder, SiO ₂ , Fe ₂ O ₃ , Al ₂ O ₃ , TiO ₂ , MgO, CaO, etc. Addition of these additives has been studied (see, for example, Patent Document 1). In Patent Document 1, additives such as SiO ₂ , Fe ₂ O ₃ , Al ₂ O ₃ , TiO ₂ , MgO, and CaO are added to Al ₂ O ₃ powder and TiO ₂ powder, and molded, 1450 to 1550. It is described that it was baked at ° C.

In addition, conventionally, MgO and SiO ₂ are added to Al ₂ TiO ₅ raw material powder having an average particle size of 1.54 to 8.06 μm, and then molded, and then fired at 1500 ° C., whereby sintered body strength and low thermal expansion are obtained. A sintered body with improved properties is known (see Patent Document 2).

JP-A-8-290963 JP-A-1-249657

Conventionally, as in Patent Document 1, additives such as SiO ₂ , Fe ₂ O ₃ , Al ₂ O ₃ , TiO ₂ , MgO, and CaO are added to Al ₂ O ₃ powder and TiO ₂ powder, and molded, Firing at about 1500 ° C. is performed, and when Al ₂ O ₃ powder and TiO ₂ powder are added with SiO ₂ constituting an amorphous material and fired at the same time, Al ₂ TiO ₅ crystals are obtained. oxides of the above additives or a composition that is solid solution, by oxides on the periphery of Al ₂ TiO ₅ crystal or precipitate, thermal decomposition resistance of the Al ₂ TiO ₅ crystal is improved during.

However, when the material composed of the Al ₂ TiO ₅ crystal of Patent Document 1 is applied to a filter that comes into contact with the exhaust gas of an automobile, the heat-resistant limit temperature is low. For example, when the filter is subjected to a high temperature of 1450 ° C. or more in the regeneration process Although the filter did not melt, there was a problem that the filter was deformed and the heat resistance was still low.

Further, as in Patent Document 2, the addition of the average particle size MgO and SiO ₂ to _Al 2 TiO ₅ raw powder 1.54～8.06Myuemu, after molding, and baked at a high 1500 ° C. temperature, Al ₂ MgO is solid-dissolved in the TiO ₅ crystal surface layer. In this case, too, when applied to a filter that comes into contact with an automobile exhaust gas, the heat-resistant limit temperature is low. For example, when exposed to a high temperature of 1450 ° C. or higher during filter regeneration processing Although the filter did not melt, there was a problem that the filter was deformed and the heat resistance was still low.

  An object of this invention is to provide the porous ceramic member and filter which can improve heat resistance.

  As a result of studying an amorphous phase that joins crystal grains composed of aluminum titanate type crystals, the present inventors have found that an amorphous phase is suppressed by suppressing diffusion of Al, Mg, etc. into the amorphous phase. As a result, the inventors have found that the heat resistance of the porous ceramic member can be improved by increasing the melting temperature of the porous ceramic member.

That is, the porous ceramic member of the present invention joins crystal particles made of an aluminum titanate type crystal containing Al, Ti, Mg and O with an amorphous phase made of an amorphous material containing Si. The amorphous phase has a thickness corresponding to the distance between the crystal grains located at both ends of the amorphous phase, and the amorphous phase. The interstitial phase has a particle vicinity part between each of the crystal grains up to 0.1 μm and an intermediate part between the particle vicinity parts, and the particle vicinity part and the intermediate part are composed of Si , Al, Ti, Mg and O, and the amount of Al in the intermediate portion of the amorphous phase is smaller than the amount of Al in the vicinity of the particles.

  In such a porous ceramic member, Al, Ti, Mg and O are contained in the vicinity of the amorphous phase composed of an amorphous material between crystal grains and in the middle portion between the vicinity of the grains. Since the amount of Al in the intermediate part of the crystalline phase is less than the amount of Al in the vicinity of the particles, the melting temperature in the intermediate part of the amorphous phase can be increased and the heat resistance can be improved.

That is, it is known that as the amount of Al ₂ O ₃ , TiO ₂ , MgO or the like in the amorphous phase increases, the melting point of the amorphous phase containing Si decreases. In the member, since additives such as SiO ₂ , Fe ₂ O ₃ , Al ₂ O ₃ , TiO ₂ , MgO, CaO were added to aluminum titanate and fired at a high temperature of about 1500 ° C., titanate The crystal grains made of aluminum-type crystals are connected with each other in an amorphous phase in which SiO ₂ , Fe ₂ O ₃ , Al ₂ O ₃ , TiO ₂ , MgO, CaO, etc. are present uniformly. SiO ₂ , Fe ₂ O ₃ , Al ₂ O ₃ , TiO ₂ , MgO, CaO and the like were uniformly present, and the amorphous phase had a low melting point.

On the other hand, in the present invention, for example, an aluminum titanate type crystal is obtained by adding SiO ₂ to an aluminum titanate type crystal powder calcined at a high temperature and firing it at a temperature lower than the calcining temperature. Diffusion of Al, Ti, Mg, etc. from the powder to the amorphous phase is suppressed, Al in the vicinity of the particles of the amorphous phase made of an amorphous material between the crystal particles, and Al in the middle between the particles, Although it contains Ti, Mg and O, the amount of Al that is most easily diffused is less in the intermediate part than the vicinity of the amorphous phase particles, and the amount of Al, Ti, Mg, etc. in the intermediate part of the amorphous phase Therefore, the melting temperature becomes high and the heat resistance of the porous ceramic member can be improved.

  The porous ceramic member of the present invention is characterized in that the Al content in the intermediate portion of the amorphous phase is 3.5 atomic% or less. In such a porous ceramic member, since the amount of Al in the intermediate part of the amorphous phase is as small as 3.5 atomic% or less, the melting temperature in the intermediate part of the amorphous phase can be increased and the heat resistance can be improved.

  Furthermore, the porous ceramic member of the present invention contains Al, Ti, and Mg uniformly in the crystal particles, and contains Al at least 20 atomic% and Mg at least 2.5 atomic%. Features. In such a porous ceramic member, the decomposition resistance can be improved by containing 20 atomic% or more of Al and 2.5 atomic% or more of Mg in the particles.

In addition, the porous ceramic member of the present invention is characterized in that the half width of the main peak of the aluminum titanate crystal is 0.20 ° or less in the X-ray diffraction measurement result. In such a porous ceramic member, the half-value width of the main peak of the aluminum titanate type crystal appearing at 2θ = 25 to 27 ° or 32 to 34 ° is 0.20 ° or less, and the crystallinity of aluminum titanate Therefore, for example, by adding SiO ₂ to an aluminum titanate type crystal powder calcined at a high temperature and firing it at a temperature lower than the calcining temperature, it becomes amorphous from the aluminum titanate type crystal powder. Diffusion of Al, Ti, Mg, etc. into the phase can be suppressed, the heat resistance of the amorphous phase can be increased, and the heat resistance of the porous ceramic member can be further improved.

  The porous ceramic member of the present invention is characterized in that Fe is contained inside the crystal particles. In such a porous ceramic member, decomposition due to heat can be suppressed and the thermal decomposition resistance can be improved.

  The filter of the present invention comprises a filter element made of the above porous ceramic member. In such a filter, long-term reliability can be improved by using a porous ceramic member capable of improving heat resistance as a filter element.

  The porous ceramic member of the present invention contains Al, Ti, Mg, and O in the vicinity of the amorphous phase composed of an amorphous material between the crystal grains and in the middle part between the vicinity of the grains. Since the amount of Al in the intermediate part of the crystalline phase is less than the amount of Al in the vicinity of the particles, the melting temperature in the intermediate part of the amorphous phase can be increased and the heat resistance can be improved. Long-term reliability can be improved by using a filter element made of such a porous ceramic member for a filter.

1 is a perspective view showing a honeycomb structure (filter element) using a porous ceramic member of the present invention. (A) is explanatory drawing which shows the structure | tissue of the porous ceramic member of this invention, (b) is explanatory drawing for demonstrating an amorphous phase. It is a graph which shows content of each element, such as Al and Ti, in a crystal grain and an amorphous phase.

  FIG. 1 shows an example of a filter element 1, in which a rectangular column-shaped gas flow path 3 is formed in the height direction of a cylindrical porous ceramic member surrounded by an outer peripheral wall 2, and a partition wall 4 therebetween is porous. It is said that. FIG. 1 shows a honeycomb structure in which a square columnar cell has a basic structure and a plurality of the cells are arranged. However, the filter element 1 of the present invention is not necessarily limited to the one having a quadrangular columnar cell as a basic structure. Absent. For example, the shape can be other than the honeycomb, and even in the honeycomb structure, the cell shape can be a triangle, a hexagon, a rhombus, or a mixture of these.

  Further, all or part of the opening direction of the honeycomb may be blocked to give a sandwich structure to give impact resistance, and it can be used as a filter element. In some cases, the filter element is configured by containing a catalyst in the porous ceramic member. The filter of the present invention is configured by housing the filter element in a container.

  The porous ceramic member of the present invention is made of an amorphous material containing Si in which crystal grains of an aluminum titanate type crystal (also referred to as a pseudo-brookite type crystal) containing Al, Ti, Mg and O are made of each other. It is formed by joining. It is desirable that the average particle diameter of crystal grains made of aluminum titanate type crystals is 25 μm or more.

The aluminum titanate type crystal containing Ti, Al, Mg and O includes aluminum titanate whose composition formula by molar ratio is represented by Al ₂ TiO ₅ and magnesium titanate represented by MgTi ₂ O _5. For example, aluminum titanate and titanic acid represented by Al _{2 (1-x)} Mg _x Ti _{(1 + x)} O ₅ (0.20 ≦ x <0.5) are known. There is a crystal made of a solid solution with magnesium (also known as: aluminum magnesium titanate). In the present invention, crystal grains represented by Al _{2 (1-x)} Mg _x Ti _{(1 + x)} O ₅ (0.20 ≦ x <0.5) are desirable.

  As shown in FIG. 2, the crystal particles 11 made of aluminum titanate-type crystals are joined together by an amorphous phase 13 made of an amorphous material containing Si. The intermediate portion 13a of the amorphous phase 13 and the particle vicinity portion 13b between the intermediate portions 13a contain Si, Al, Ti, Mg, and O. These Al, Mg, and Ti are diffused from the crystal particles 11.

  In the porous ceramic member of the present invention, it is important that the amount of Al is less in the intermediate portion 13a than in the particle vicinity portion 13b of the amorphous phase 13. The amount of Al in the intermediate portion 13a of the amorphous phase 13 is desirably 3.5 atomic percent or less. In such a porous ceramic member, since the Al amount in the intermediate portion 13a of the amorphous phase 13 is as small as 3.5 atomic% or less, the melting temperature in the intermediate portion 13a of the amorphous phase 13 is increased, and the heat resistance is increased. It can be improved.

  Among Al, Mg and Ti, it is known that the diffusion amount of Al into the amorphous phase 13 is the largest, and since the diffusion amount of Al is as small as 3.5 atomic% or less, the non-migration of Mg and Ti. The amount of diffusion into the crystalline phase 13 is also reduced, the melting temperature in the intermediate portion 13a of the amorphous phase 13 can be increased, and the heat resistance can be improved.

  In particular, Si is contained at 33.0 atomic% or more in the intermediate portion 13a of the amorphous phase 13 that joins the crystal grains 11 together, Al is 3.5 atomic% or less, and Ti is 2.0 atomic% or less. , Mg is preferably 0.3 atomic% or less. Thereby, since the element diffusing from the crystal particles 11 into the amorphous phase 13 containing Si is suppressed to a predetermined amount or less, the melting temperature of the amorphous phase 13 is increased, and the heat resistance is increased. it can.

  Less Al, Ti, and Mg are present in the intermediate portion 13a of the amorphous phase 13, but due to diffusion, Al is 1.0 atomic% or more, Ti is 0.3 atomic% or more, and Mg is 0.05 More than atomic percent exists. In the present invention, Si, Al, Ti, and Mg present in the intermediate portion 13a of the amorphous phase 13 are particularly 35.0 to 40.0 atomic% Si and 1.0 to 3.5 atomic% Al. From the viewpoint of heat resistance, it is desirable to contain 0.3 to 2.0 atomic percent of Ti and 0.05 to 0.3 atomic percent of Mg.

The amorphous phase 13 containing Si is mainly composed of SiO ₂ , and additionally contains Al ₂ O ₃ , TiO ₂ , and MgO diffused from the crystal particles 11 during firing as subcomponents. As the Al ₂ O ₃ , TiO ₂ , and MgO increase, the melting point of the amorphous phase 13 decreases and the amorphous phase 13 easily deforms and heat resistance decreases. Since 13a has a low Al content of 3.5 atomic% or less, the heat resistance of the amorphous phase 13 can be maintained high.

  In the present invention, the region near the particle 13 b is from the surface of the crystal particle 11 to the amorphous phase up to 0.1 μm, and the intermediate portion is defined as the intermediate portion 13 a of the amorphous phase 13. Note that the distance between the crystal grains 11, in other words, the thickness of the amorphous phase 13 is about 2 to 10 μm, although there is variation.

  In the porous ceramic member of the present invention, Al, Ti, and Mg are almost uniformly present inside the crystal particles 11, and Al is contained in the crystal particles 11 by 20 atomic% or more, and Mg is 2.5 atomic% or more. It is desirable to contain. In such a porous ceramic member, a solid solution of aluminum titanate and magnesium titanate is formed in the crystal particles 11 by containing Al in the particles at 20.0 atomic% or more and Mg at 2.5 atomic% or more. As a result, the thermal decomposition resistance can be improved as compared with the crystal particles 11 made of only aluminum titanate.

  In the present invention, the fact that Al, Ti and Mg are uniformly present inside the crystal particle 11 means that the position is 0.1 μm from the surface of the crystal particle to the inside of the particle, and 1 to 2 μm from the surface to the inside of the particle. When the position is measured, it means that the amount of Al having the largest amount of element varies within a range of 2 atomic% or less.

  The crystal particles 11 preferably contain Al at 25.0 atomic% or less and Mg at 5.0 atomic% or less from the viewpoint of achieving both heat resistance and decomposition resistance.

  The amount of elements in the intermediate portion 13a of the amorphous phase 13 and the crystal particles 11 can be determined by energy dispersive X-ray spectroscopy (EDS).

In the porous ceramic member of the present invention, it is desirable that the half width of the main peak of the aluminum titanate crystal is 0.20 ° or less in the X-ray diffraction measurement result using Cu-kα rays. The main peak of the aluminum titanate type crystal appears at 2θ = 25 to 27 ° or 2θ = 32 to 34 ° depending on the composition, but the half width of the main peak is 0.20 ° or less, and the aluminum titanate crystallizes. For example, by adding SiO ₂ to an aluminum titanate type crystal powder calcined at a high temperature and firing at a temperature lower than the calcining temperature, the amorphous titanate type crystal powder is amorphous. Diffusion of Al, Ti, Mg or the like into the mass phase 13 can be suppressed, the heat resistance of the amorphous phase 13 can be increased, and the heat resistance of the porous ceramic member can be further improved.

  The crystal particles 11 made of an aluminum titanate crystal preferably have an average particle size of 25 μm or more. Since it has such a large particle size, the porosity can be increased and the average pore size can be increased. In particular, the average particle size of the crystal particles 11 is desirably 40 μm or more. In addition, if the porosity and the average pore diameter are too large together with the average particle diameter, the average particle diameter is desirably 100 μm or less from the viewpoint that the mechanical strength is reduced and the structure ceramic member cannot be applied. The average particle diameter can be determined by the intercept method.

Further, in the porous ceramic member of the present invention desirably contains 0.5 to 5 wt% in the total amount of Si in terms of SiO _2. By making Si 0.5 to 5% by mass in terms of SiO ₂ , crystal particles 11 made of aluminum titanate type crystals can be sufficiently connected with an amorphous material containing Si to improve strength. In addition, since the amount of Si is small, a decrease in porosity and average pore diameter can be suppressed. From the viewpoint of obtaining strength, predetermined porosity, and average pore diameter, it is desirable that the Si amount is contained in an amount of 1 to 3% by mass in terms of SiO ₂ . The amount of Si can be measured by fluorescent X-ray analysis or ICP (Inductively Coupled Plasma) emission analysis.

Furthermore, the porous ceramic member of the present invention preferably contains Fe in the crystal particles. The iron titanate type crystal containing Fe includes iron titanate, and forms a solid solution with the aluminum titanate or magnesium titanate. For example, titanic acid as represented by the composition formula Al _{2 (1-xy)} Mg _x Fe _2y Ti _{(1 + x)} O ₅ (0.20 ≦ x <0.5, 0 <y <1) There is a crystal made of a solid solution composed of three components of aluminum, magnesium titanate and iron titanate. In the porous ceramic member of the present invention, when a pseudo-brookite type crystal in which three components of aluminum titanate-magnesium titanate-iron titanate are used as a crystal is used, the crystal is a thermochemically stable component. Therefore, decomposition of crystals due to heat can be suppressed, and the thermal decomposition resistance can be improved.

  Furthermore, the filter of this invention can be made into a filter with high heat resistance and high long-term reliability by providing the filter element which consists of the said porous ceramic member.

  Next, the manufacturing method of the porous ceramic member of this invention is demonstrated.

  Among porous ceramic members, an example of a method for manufacturing a honeycomb structure (filter element) used specifically for exhaust gas purification of automobiles and the like will be described here.

For example, a raw material necessary for forming a solid solution represented by Al _{2 (1-x)} Mg _x Ti _{(1 + x)} O ₅ is prepared. In some cases, Fe is dissolved in the solid solution, but here, a case where Fe is not dissolved is described. _Here, x in solid solution represented by _{Al 2 (1-x) Mg} x Ti (1 + x) O 5 is preferred in enhancing the heat resistance less than 0.5. This is because when x is 0.5 or more, Al and Mg in the crystal particles are easily diffused into the amorphous material.

  Next, for example, an alumina raw material, a titania raw material, and a magnesium carbonate raw material are prepared and mixed so as to have a predetermined composition. As long as a solid solution having the above composition formula can be formed, raw materials such as hydroxides and nitrates may be used in addition to the raw materials of metal oxides and carbonates, and these compounds may be used.

  As the alumina raw material, titania raw material, and magnesium carbonate powder, it is desirable to use high-purity ones, and it is desirable to use those having a purity of 99.0% or more, particularly 99.5% or more.

  Moreover, the mixed raw material of the said alumina raw material, titania raw material, and magnesium carbonate is granulated. Granulation is performed by dry mixing and granulation, or is put into a mill such as a rotary mill, vibration mill, bead mill, etc., and a slurry obtained by wet mixing with at least one of water, acetone, and isopropyl alcohol (IPA) is used. It is desirable to dry and granulate. As a method for drying the slurry, the slurry may be put in a container and heated, dried, granulated, dried by a spray dryer, granulated, or dried by other methods for granulation. There is no problem. Granulated powder produces granulated powder with an average particle diameter of 50-300 micrometers.

  Thereafter, the granulated powder is calcined in an oxygen-containing atmosphere, for example, air. The calcining temperature is calcined at 1500 ° C. or higher, which is higher than the temperature at which the aluminum titanate type crystal is generated (about 1200 ° C.) for 1 to 5 hours in order to sufficiently generate the aluminum titanate type crystal. The calcining temperature is particularly preferably 1510 ° C. or higher. On the other hand, from the viewpoint of preventing the calcined powder from agglomerating firmly, the calcining temperature is desirably 1550 ° C. or lower. Thus, an aluminum titanate type calcined powder in which Al, Mg, and Ti are dissolved is produced. By this calcination, a powder of almost 100% pseudo-brookite crystal is produced. Since the calcining temperature is high, Al, Ti and Mg are uniformly present in the calcined powder.

The calcined powder preferably has a half-value width of the main peak of the aluminum titanate type crystal of 0.20 ° or less in the X-ray diffraction measurement result. By using such a calcined powder, for example, by adding SiO ₂ to an aluminum titanate type crystal powder calcined at a high temperature and firing at a temperature lower than the calcining temperature, aluminum titanate Diffusion of Al, Ti, Mg, etc. from the type crystal powder into the amorphous phase can be suppressed, the heat resistance of the amorphous phase can be increased, and the heat resistance of the porous ceramic member can be further improved. Since the firing temperature is lower than the calcination temperature, the half width after calcination does not change even after firing.

  A mesh pass of the calcined powder is performed to obtain a calcined powder of 25 to 60 μm. In addition, since the calcining powder of the aluminum titanate type has a low calcining temperature, almost no grain growth is caused by the calcining, and it has almost the same particle size as the calcining powder.

Then, the SiO ₂ powder is added to and mixed with the aluminum titanate type calcined powder. The mixing method can also be performed dry or wet. As the SiO ₂ powder, a powder having an average particle diameter of 1 to 3 μm is used. By using a powder having a particle size in this range, the SiO ₂ powder can be uniformly dispersed on the surface of the calcined powder.

  A molding aid is added to the mixed powder, and the mixture is formed into a honeycomb shape by extrusion using a die. After sufficiently drying the obtained molded body, the honeycomb body is fired in an oxidizing atmosphere at a temperature lower than 1450 ° C., which is lower than the calcining temperature, for 0.5 to 5 hours without using a pore-forming agent. A porous ceramic member having a shape can be formed. The firing temperature is particularly preferably 1350 to 1440 ° C. This firing step is a step of melting an amorphous material and joining crystal grains together, and performing a mutual diffusion of elements such as Al, Mg, and Si within a certain range.

  That is, the present inventors try to diffuse Al, Mg, Ti into an amorphous phase from, for example, aluminum titanate type crystal particles having an average particle diameter of 30 μm by firing at 1350 to 1440 ° C. Since the calcination temperature is calcined at a high temperature of 1500 ° C. or higher, and calcined at a temperature lower than the calcination temperature, Al, Mg and Ti hardly diffuse from the crystal particles into the amorphous phase, and are most diffused. It is considered that Al easily forms a structure in which the amount of Al in the intermediate portion is smaller than that in the vicinity of the amorphous phase particles and is contained in the intermediate portion of the amorphous phase at 3.5 atomic% or less.

  In such a method for producing a porous ceramic member, since the firing temperature is lower than the synthesis temperature (1400 ° C. or higher) of the aluminum titanate type crystal containing Al, Ti, and Mg, an amorphous material containing Si is used. In addition to being able to bond crystal grains, firing at 1350 to 1440 ° C. can suppress interdiffusion of elements such as Al, Mg, Ti, and Si, and improve heat resistance. In addition, since the mutual diffusion of elements such as Al, Mg, Ti, and Si can be suppressed, crystal grains as designed can be obtained, and heat-resistant decomposition as designed can be obtained. Since the calcination is performed by heat-treating the pseudo-brookite crystal, the crystal particles have no corners and have a round particle shape as a whole.

  Examples of the present invention will be specifically described below, but the present invention is not limited to these examples.

  The alumina raw material used was LS110 manufactured by Nippon Light Metal Co., Ltd., having an average particle size of 1.5 μm, an alkali metal impurity amount of 0.1 mass%, and a silicon impurity amount of 0.1 mass%. The titania raw material used was JA-3 manufactured by Teika Co., which had an average particle size of 0.2 μm and an alkali metal impurity content of 0.3 mass%. The magnesium carbonate raw material used is TT manufactured by Tokuyama Corporation, which has an apparent specific gravity of 0.23 g / ml and does not contain impurities of alkali metal and silica. The iron oxide raw material was JC-W made by JFE Chemical, and the average particle diameter was 1.0 μm.

  Further, as a silica raw material, Snowmark SP-3 manufactured by Marumama Kamado Ceramics Co., Ltd., having an average particle size of 1.2 μm was used.

First, the above alumina raw material, titania raw material, magnesia raw material, and iron oxide raw material are prepared so as to be an aluminum titanate type crystal powder composed of Al _1.2 Mg _0.2 Fe _0.4 Ti _1.2 O ₅ Then, isopropyl alcohol (IPA) was added to the solvent, and an alumina ball having a diameter of 10 mm was used as a medium and mixed for 72 hours with a rotary mill to prepare a slurry. The slurry was heated to 110 ° C. to volatilize IPA and dried, and then passed through a mesh.

  The granulated powder was calcined at 1500 ° C. in the atmosphere to synthesize aluminum titanate type crystal powder containing Al, Ti, Mg and Fe. The main peak of the aluminum titanate crystal using the Cu-kα ray occurred at 2θ = 32 to 34 °, and the half width was 0.17 °.

  2 parts by mass of silica powder was added to 100 parts by mass of the crystal powder and mixed with a universal kneader to obtain a raw material powder.

  Paraffin wax was added to the raw material powder, mixed and then dried to form a molding powder. Next, a disk-shaped molded body having a diameter of 20 mm × thickness of 10 mm and a cylindrical molded body having a diameter of 10 mm × height of 15 mm were produced by using this molding powder by a powder pressure molding method. Each molded body was fired in air at 1375 ° C. for 4 hours to obtain a sintered body evaluation sample. The temperature increase rate from room temperature to the sintering temperature was 200 ° C./h.

  When the average particle size of the obtained sintered body was determined by an intercept method with respect to a scanning micrograph (500 times), it was 55 μm. Further, when the porosity and average pore diameter of the sintered body were determined by mercury porosimetry, the porosity was 40% and the average pore diameter was 10 μm.

  Further, the obtained sintered body was made into a thin piece, and the structure of crystal grains and grain boundaries was observed with a TEM (transmission electron microscope). At that time, composition analysis was performed on the intermediate portion of the amorphous phase and the vicinity of the particles by energy dispersive X-ray spectroscopy (EDS), and the contents of Al, Ti, Mg, Fe, Si, and O were measured. As a result, in the middle part of the amorphous phase, Al is 3.5 atomic%, Ti is 1.0 atomic%, Mg is 0.3 atomic%, Fe is 0.1 atomic%, Si is 34 atomic%, O Was 61 atomic%.

  On the other hand, in the vicinity of the amorphous phase particles (position of 0.1 μm from the particle surface), Al is 15 atomic%, Ti is 13 atomic%, Mg is 3.5 atomic%, Fe is 4.5 atomic%, Si was 15 atomic%, O was 49 atomic%, and the amount of Al in the intermediate part was smaller than that in the vicinity of the particles.

  In addition, as a result of performing composition analysis on the position of 0.1 μm from the surface of the crystal grain to the inside of the crystal grain and the position of 2.0 μm from the surface to the inside of the crystal grain, At a position of 0.1 μm toward Al, Al is 22 atomic%, Ti is 18 atomic%, Mg is 3.2 atomic%, Fe is 5.2 atomic%, Si is 0.6 atomic%, and O is 51 atoms. %Met.

  On the other hand, at a position of 2.0 μm from the grain surface toward the inside of the crystal grain, Al is 21 atomic%, Ti is 19 atomic%, Mg is 3.2 atomic%, Fe is 6.2 atomic%, and Si is 0.6 Atomic%, O is 50 atomic%, Al, Ti, and Mg are almost uniformly present inside the particle, Al is 20 atomic% or more, and Mg is 2.5 atomic% or more inside the crystal particle. Contained. FIG. 3 shows the content of each element in the crystal particles and the amorphous phase.

  About the heat resistance of each sintered compact, each sample of the cylindrical sintered compact was heat-processed in air | atmosphere, and the thermal limit temperature which a cylindrical sintered compact shows a deformation | transformation of 20% or more was evaluated.

Regarding the thermal decomposition resistance of each sintered body, each sample of the disk-shaped sintered body was further subjected to a thermal decomposition test at 1100 ° C. for 300 hours in an air atmosphere to evaluate the thermal decomposition resistance. The sample prepared before and after the thermal decomposition test was measured for peak intensity by X-ray diffractometry, and an aluminum titanate type crystal having a diffraction angle 2θ of 25 to 27 ° or 32 to 34 ° was obtained. a main peak intensity _{(I AMT),} the diffraction angle 2θ of TiO ₂ phase 36.1 ° in the peak intensity _{(I T)} from the peak intensity ratio _a = I _{AMT /} a _(I AMT + _{I T)} was calculated. Furthermore, the value of (1-A ₁ / A ₀ ) was calculated with the peak intensity ratios before and after the thermal decomposition test as A ₀ and A ₁ , respectively.

Next, the aluminum titanate type crystal powder composed of Al _1.2 Mg _0.2 Fe _0.4 Ti _1.2 O ₅ and the TiO ₂ powder were mixed while changing the quantity ratio, and (1-I _AMT / was determined thermal decomposition ratio against the value of I _T) value and a calibration curve prepared by calculating the _{(1-a 1 / a 0} ).

  Moreover, about the thermal expansion coefficient, the thermal expansion coefficient of 20 degreeC-800 degreeC of the sample of the cylindrical sintered compact was measured on the conditions of the temperature increase rate of 20 degree-C / min based on JISR1618.

As a result, the heat resistant limit temperature was 1600 ° C., the thermal decomposition rate was 1%, and the thermal expansion coefficient was 2.0 × 10 ⁻⁶ / ° C., showing good characteristics.

Slurry was prepared so as to be an aluminum titanate type crystal powder composed of Al _0.8 Mg _0.3 Fe _0.6 Ti _1.3 O ₅ , and granulated powder was prepared.

  This granulated powder was calcined at 1520 ° C. in the air to synthesize aluminum titanate type crystal powder containing Al, Ti, Mg and Fe. The main peak of the aluminum titanate crystal using the Cu-kα ray occurred at 2θ = 32 to 34 °, and the half width was 0.15 °.

  3 parts by mass of silica powder was added to 100 parts by mass of the crystal powder and mixed with a universal kneader to obtain a raw material powder.

  Paraffin wax was added to the raw material powder, mixed and then dried to form a molding powder. Next, a disk-shaped molded body having a diameter of 20 mm × thickness of 10 mm and a cylindrical molded body having a diameter of 10 mm × height of 15 mm were produced by using this molding powder by a powder pressure molding method. Each molded body was fired at 1350 ° C. for 4 hours in the air to obtain a sintered body evaluation sample. The temperature increase rate from room temperature to the sintering temperature was 200 ° C./h.

  In the same manner as in Example 1, when the average particle size, porosity and average pore size of the sintered body were determined, the average particle size was 58 μm, the porosity was 45%, and the average pore size was 12 μm.

  In addition, the most diffused at the intermediate part of the amorphous phase and the vicinity of the particle, the position of 0.1 μm from the surface of the crystal grain to the inside of the crystal grain, and the position of 2.0 μm from the surface to the inside of the crystal grain. Easy Al or Al and Mg contents were measured. As a result, Al is 2.2 atomic% in the intermediate part of the amorphous phase, Al is 10 atomic% in the vicinity of the particle, Al is 21 atomic% at a position 0.1 μm inward from the surface of the crystal grain, and Mg is It was 4.5 atomic%, and the Al content in the intermediate part was smaller than that in the vicinity of the particles.

  Further, at a position of 2.0 μm from the surface of the crystal grain to the inside, Al is 22 atomic% and Mg is 4.3 atomic%, and Al and Mg are almost uniformly present inside the grain. Contained 20 atomic% or more of Al and 2.5 atomic% or more of Mg.

Further, the heat resistant limit temperature was 1580 ° C., the thermal decomposition rate was 1%, and the thermal expansion coefficient was 2.2 × 10 ⁻⁶ / ° C., indicating good characteristics.

A slurry was prepared so as to obtain an aluminum titanate type crystal powder composed of Al _0.8 Mg _0.4 Fe _0.4 Ti _1.4 O ₅ , and granulated powder was prepared.

  This granulated powder was calcined at 1510 ° C. in the atmosphere to synthesize aluminum titanate type crystal powder containing Al, Ti, Mg and Fe. The main peak of the aluminum titanate crystal using the Cu-kα ray occurred at 2θ = 32 to 34 °, and the half width was 0.16 °.

  2 parts by mass of silica powder was added to 100 parts by mass of the crystal powder and mixed with a universal kneader to obtain a raw material powder.

  Paraffin wax was added to the raw material powder, mixed and then dried to form a molding powder. Next, a disk-shaped molded body having a diameter of 20 mm × thickness of 10 mm and a cylindrical molded body having a diameter of 10 mm × height of 15 mm were produced by using this molding powder by a powder pressure molding method. Each molded body was fired in the atmosphere at 1400 ° C. for 4 hours to obtain a sintered body evaluation sample. The temperature increase rate from room temperature to the sintering temperature was 200 ° C./h.

  As in Example 1, when the average particle size, porosity, and average pore size of the sintered body were determined, the average particle size was 50 μm, the porosity was 42%, and the average pore size was 13 μm.

  In addition, the compositional analysis was performed for the intermediate part of the amorphous phase and the vicinity of the particle, the position of 0.1 μm from the surface to the inside of the crystal particle, and the position of 2.0 μm from the surface to the inside, and the contents of Al and Mg Was measured. As a result, Al was 2.3 atomic% in the amorphous intermediate part, and 0.10 atomic% in the vicinity of the particle, and the Al content in the intermediate part was smaller than that in the vicinity of the particle.

  Further, Al is 20 atomic% and Mg is 4.9 atomic% at a position of 0.1 μm from the surface of the crystal grain to the inside, and Al is 21 atoms at a position of 2.0 μm from the surface of the crystal grain to the inside. %, Mg is 4.5 atomic%, Al and Mg are almost uniformly present inside the grain, and Al is contained in the crystal grain within 20 atomic% or more and Mg is contained 2.5 atomic% or more. Was.

Further, the heat resistant limit temperature was 1560 ° C., the thermal decomposition rate was 1%, and the thermal expansion coefficient was 2.5 × 10 ⁻⁶ / ° C., indicating good characteristics.

Comparative example

The calcining temperature is 1450 ° C., and the silica powder is 2.2 parts by mass with respect to 100 parts by mass of the aluminum titanate type crystal powder composed of Al _1.2 Mg _0.2 Fe _0.4 Ti _1.2 O _5. A sintered body was produced in the same manner as in Example 1 except that 1 part by mass of magnesia (MgO) powder was added and the firing temperature was 1500 ° C. The average particle diameter of the obtained sintered body was 35 μm, the porosity of the sintered body was 20%, and the average pore diameter was 7 μm.

The heat resistant limit temperature is 1450 ° C., the thermal decomposition rate is 1%, and the thermal expansion coefficient is 2.8 × 10 ⁻⁶ / ° C., indicating that the heat resistance is poor. Since the present inventors have a high firing temperature of 1500 ° C., which is higher than the calcination temperature, Al, Ti, and Mg in the crystal powder diffuse into the amorphous material, and the added Mg is amorphous. It is considered that the heat resistance of the amorphous material is lowered and the heat resistance is deteriorated by diffusing into the material.

DESCRIPTION OF SYMBOLS 1 ... Filter element 2 ... Outer peripheral wall 3 ... Cell 4 ... Partition 11 ... Crystal grain 13 ... Amorphous phase 13a ... Middle part of amorphous phase 13b ...・ Particles near the amorphous phase

Claims (6)

Al, Ti, crystal grains of aluminum titanate type crystal containing Mg and O, a porous ceramic member formed by joining an amorphous phase made of an amorphous material containing Si, the The amorphous phase has a thickness corresponding to the distance between the crystal grains located at both ends of the amorphous phase, and the amorphous phase is 0% from the crystal grains. A particle vicinity part of up to 1 μm and an intermediate part between the particle vicinity parts, and the particle vicinity part and the intermediate part contain Si, Al, Ti, Mg and O In addition, the porous ceramic member is characterized in that the amount of Al in the intermediate portion of the amorphous phase is smaller than the amount of Al in the vicinity of the particles.   2. The porous ceramic member according to claim 1, wherein an Al amount in an intermediate portion of the amorphous phase is 3.5 atomic% or less.   3. The crystal grains according to claim 1 or 2, wherein Al, Ti and Mg are uniformly present in the crystal grains, and Al is contained at 20 atomic% or more and Mg is contained at 2.5 atomic% or more. Porous ceramic member.   4. The porous ceramic member according to claim 1, wherein, in the X-ray diffraction measurement result, the half-value width of the main peak of the aluminum titanate crystal is 0.20 ° or less. 5.   The porous ceramic member according to any one of claims 1 to 4, wherein Fe is contained inside the crystal particles.   A filter comprising a filter element comprising the porous ceramic member according to claim 1.

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