WO2010143494A1 - Columnar aluminum titanate, method for producing same, and honeycomb structure - Google Patents

Columnar aluminum titanate, method for producing same, and honeycomb structure Download PDF

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WO2010143494A1
WO2010143494A1 PCT/JP2010/058108 JP2010058108W WO2010143494A1 WO 2010143494 A1 WO2010143494 A1 WO 2010143494A1 JP 2010058108 W JP2010058108 W JP 2010058108W WO 2010143494 A1 WO2010143494 A1 WO 2010143494A1
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aluminum titanate
columnar
honeycomb structure
columnar aluminum
number average
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PCT/JP2010/058108
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French (fr)
Japanese (ja)
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伸樹 糸井
宏仁 森
隆寛 三島
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大塚化学株式会社
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2425—Honeycomb filters characterized by parameters related to the physical properties of the honeycomb structure material
    • B01D46/24494—Thermal expansion coefficient, heat capacity or thermal conductivity
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    • C01G23/00—Compounds of titanium
    • C01G23/003—Titanates
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    • B01D—SEPARATION
    • B01D39/00—Filtering material for liquid or gaseous fluids
    • B01D39/14—Other self-supporting filtering material ; Other filtering material
    • B01D39/20—Other self-supporting filtering material ; Other filtering material of inorganic material, e.g. asbestos paper, metallic filtering material of non-woven wires
    • B01D39/2068—Other inorganic materials, e.g. ceramics
    • B01D39/2072—Other inorganic materials, e.g. ceramics the material being particulate or granular
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    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
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    • B01D46/2418—Honeycomb filters
    • B01D46/2425—Honeycomb filters characterized by parameters related to the physical properties of the honeycomb structure material
    • B01D46/2429—Honeycomb filters characterized by parameters related to the physical properties of the honeycomb structure material of the honeycomb walls or cells
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
    • B01D46/2455—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure of the whole honeycomb or segments
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    • B01D46/2418—Honeycomb filters
    • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
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    • B01D46/2418—Honeycomb filters
    • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
    • B01D46/2482—Thickness, height, width, length or diameter
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
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    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/46—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates
    • C04B35/462—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates
    • C04B35/478—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates based on aluminium titanates
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Definitions

  • the present invention relates to a columnar aluminum titanate, a manufacturing method thereof, and a honeycomb structure manufactured using the columnar aluminum titanate.
  • Aluminum titanate is expected to be a porous material used in automobile exhaust gas treatment catalyst carriers, diesel particulate filters (DPFs), etc. because of its low thermal expansion, excellent thermal shock resistance, and high melting point. Development is underway.
  • Patent Document 1 an aluminum titanate sintered body having high strength and less mechanical strength deterioration with respect to repeated thermal history is obtained without impairing the high melting point and low thermal expansion property of aluminum titanate. Therefore, it has been proposed to sinter aluminum titanate added with magnesium oxide and silicon oxide.
  • Patent Document 2 discloses that an exhaust gas filter is manufactured using columnar aluminum titanate, and when the longitudinal direction of the columnar particles has a negative thermal expansion coefficient, the direction perpendicular to the longitudinal direction is positive thermal expansion. It has been proposed to manufacture an exhaust gas filter that has a coefficient or a negative thermal expansion coefficient in the direction perpendicular to the longitudinal direction when the longitudinal direction of the columnar particles has a positive thermal expansion coefficient.
  • a sintered body such as a honeycomb structure obtained by sintering aluminum titanate, it is required to increase the mechanical strength of the sintered body.
  • An object of the present invention is to provide a columnar aluminum titanate capable of producing a sintered body such as a honeycomb structure having a small thermal expansion coefficient and excellent mechanical strength, a method for producing the same, and the columnar aluminum titanate. It is to apply the honeycomb structure to be manufactured.
  • mullite 5 to 25% by weight of mullite and 2 to 10% by weight of aluminum oxide are attached to the surface with respect to the columnar aluminum titanate.
  • Aluminum oxide functions as a sintering aid, and a sintered body having high mechanical strength can be obtained.
  • the upper limit of the average aspect ratio is not particularly limited, but is generally 5 or less.
  • the amount of mullite deposited is 5 to 25% by weight based on the columnar aluminum titanate as described above. Therefore, 5 to 25 parts by weight of mullite adheres to the surface of the aluminum titanate with respect to 100 parts by weight of the columnar aluminum titanate.
  • the amount of mullite attached is less than 5% by weight, a sintered body having high mechanical strength cannot be obtained. If the adhesion amount of mullite exceeds 25% by weight, the thermal expansion coefficient of mullite is larger than that of aluminum titanate, so that the thermal expansion coefficient of the sintered body cannot be reduced.
  • the adhesion amount of aluminum oxide is 2 to 10% by weight, more preferably 4 to 6% by weight, based on the columnar aluminum titanate as described above. Therefore, 2 to 10 parts by weight of aluminum oxide is adhered to the surface of aluminum titanate with respect to 100 parts by weight of columnar aluminum titanate.
  • the adhesion amount of aluminum oxide is less than 2% by weight, a sintered body having high mechanical strength cannot be obtained.
  • the adhesion amount of aluminum oxide exceeds 10 parts by weight, the thermal expansion coefficient of aluminum oxide is larger than that of aluminum titanate, so that the thermal expansion coefficient of the sintered body cannot be reduced.
  • the number average minor axis diameter of the columnar aluminum titanate is preferably 10 ⁇ m or less.
  • the number average minor axis diameter is more preferably in the range of 5 to 10 ⁇ m.
  • the number average major axis diameter is preferably in the range of 7 to 17 ⁇ m.
  • the number average major axis diameter and the number average minor axis diameter of the columnar aluminum titanate can be measured by, for example, a flow type particle image analyzer.
  • the mullite and aluminum oxide adhering to the surface of the columnar aluminum titanate are fine particles, and generally have an average particle diameter in the range of 50 nm to 500 nm, more preferably 100 nm to 300 nm. It has an average particle size within the range.
  • the average particle size of mullite and aluminum oxide can be measured by observation with a scanning electron microscope (SEM).
  • the production method of the present invention is a method capable of producing the columnar aluminum titanate of the present invention, wherein the raw material containing a titanium source, an aluminum source, a silicon source, and a magnesium source is mixed while being mechanochemically ground. And a step of firing the pulverized mixture.
  • Aluminum titanate (Al 2 TiO 5 ) contains 2 moles of aluminum (Al) with respect to 1 mole of titanium (Ti). By mixing the titanium source and the aluminum source so that the amount of Al is more than 2 mol per 1 mol of Ti, Al exceeding 2 mol becomes mullite and aluminum oxide adhering to the surface of the columnar aluminum titanate. Since mullite (Al 6 Si 2 O 13 ) contains silicon (Si), it is necessary to include a silicon source in the raw material. Part of the silicon source contained in the raw material becomes silicon constituting mullite.
  • the columnar aluminum titanate of the present invention is produced by using a raw material containing a titanium source and an aluminum source so that Al is more than 2 mol relative to 1 mol of Ti, and further containing a silicon source. Can do.
  • the average aspect ratio is 1.3 or more by firing the pulverized mixture.
  • a columnar aluminum titanate can be produced. That is, columnar aluminum titanate can be produced by using a pulverized mixture that contains a magnesium source in the raw material and is mixed while being mechanochemically pulverized.
  • the temperature for firing the pulverized mixture is preferably a temperature in the range of 1300 to 1600 ° C. By firing within such a temperature range, the columnar aluminum titanate of the present invention can be produced more efficiently.
  • Calcination time is not particularly limited, but it is preferably performed within a range of 0.5 hours to 20 hours.
  • the mechanochemical pulverization includes a method of pulverizing while giving a physical impact.
  • pulverization by a vibration mill can be mentioned.
  • the disruption of atomic arrangement and the decrease in interatomic distance occur simultaneously due to the shear stress caused by the grinding of the mixed powder, resulting in atomic movement of the contact part of different particles, resulting in a metastable phase.
  • a pulverized mixture with high reaction activity is obtained, and the columnar aluminum titanate of the present invention can be produced by firing the pulverized mixture with high reaction activity.
  • the mechanochemical pulverization in the present invention is generally performed as a dry process without using water or a solvent.
  • the mixing treatment time by mechanochemical pulverization is not particularly limited, but generally it is preferably within the range of 0.1 to 6 hours.
  • the raw materials used in the present invention include a titanium source, an aluminum source, a silicon source, and a magnesium source.
  • a titanium source a compound containing titanium oxide can be used. Specific examples include titanium oxide, rutile ore, titanium hydroxide wet cake, and hydrous titania.
  • the aluminum source a compound that generates aluminum oxide by heating can be used.
  • Specific examples include aluminum oxide, aluminum hydroxide, and aluminum sulfate. Among these, aluminum oxide is particularly preferably used.
  • magnesium source a compound that generates magnesium oxide by heating can be used, and specific examples include magnesium hydroxide, magnesium oxide, and magnesium carbonate. Among these, magnesium hydroxide and magnesium oxide are particularly preferably used.
  • the magnesium source is preferably contained in the raw material so as to be in the range of 0.5 to 2.0% by weight in terms of oxide with respect to the total of the titanium source and the aluminum source. If it is less than 0.5% by weight, a sintered body having a low coefficient of thermal expansion and high mechanical strength may not be obtained. On the other hand, if it exceeds 2.0% by weight, columnar aluminum titanate having an average aspect ratio of 1.3 or more may not be obtained.
  • the raw material further contains a silicon source.
  • mullite By including the silicon source, mullite can be deposited on the surface of the aluminum titanate, decomposition of the aluminum titanate can be suppressed, and columnar aluminum titanate having excellent high-temperature stability can be produced. it can.
  • Examples of the silicon source include silicon oxide and silicon. Among these, silicon oxide is particularly preferably used.
  • the content of the silicon source in the raw material is preferably in the range of 3 to 7% by weight in terms of the respective oxides with respect to the total of the titanium source and the aluminum source. By setting it within such a range, columnar aluminum titanate can be more stably produced.
  • the aluminum source contains, in the raw material, an amount in which Al is more than 2 mol relative to 1 mol of Ti. In consideration of the amount of mullite and aluminum oxide deposited on the surface, the amount of the aluminum source that is excessive with respect to Ti is adjusted.
  • the sintered body obtained by sintering the columnar aluminum titanate of the present invention has mullite and aluminum oxide attached to the surface, and since the mullite and aluminum oxide serve as a sintering aid, mechanical strength is increased. High sintered body.
  • the honeycomb structure of the present invention is a honeycomb structure manufactured using the columnar aluminum titanate of the present invention, and has a thermal expansion coefficient of 1.0 ⁇ 10 6 between 30 and 800 ° C. in the extrusion direction of the honeycomb structure. It is ⁇ 6 / ° C. or less, and the crystal orientation ratio of the C axis with respect to the honeycomb extrusion direction is 0.75 or more.
  • the thermal expansion coefficient between 30 and 800 ° C. in the extrusion direction of the honeycomb structure is 1.0 ⁇ 10 ⁇ 6 / ° C. or less, it is possible to obtain characteristics excellent in thermal shock resistance.
  • the lower limit value of the thermal expansion coefficient in the extrusion direction of the honeycomb structure is not particularly limited, but is generally ⁇ 1.0 ⁇ 10 ⁇ 6 / ° C. or more.
  • the crystal orientation ratio of the C axis with respect to the honeycomb extrusion direction is 0.75 or more.
  • the thermal expansion coefficient in the extrusion direction of the honeycomb structure can be reduced.
  • the crystal orientation ratio of the C axis relative to the honeycomb extrusion direction in the present invention can be obtained from the following equation.
  • I 002 and I 230 are the extrusion surface for extrusion direction, the peak intensity of the (002) plane when the X-ray diffraction vertical plane in the vertical direction (I 002) and (230) plane peak intensity (I 230 ).
  • the C axis extends along the longitudinal direction of the columnar body. For this reason, when the honeycomb structure is extruded, the C-axis is aligned in the extrusion direction, so that the thermal expansion coefficient in the extrusion direction can be lowered.
  • the honeycomb structure of the present invention is produced by preparing a mixed composition in which, for example, a pore forming agent, a binder, a dispersant, and water are added to aluminum titanate, and this is used to form a honeycomb structure using, for example, an extruder. It can shape
  • Examples of pore-forming agents include graphite, graphite, wood powder, and polyethylene.
  • Examples of the binder include methyl cellulose, ethyl cellulose, and polyvinyl alcohol.
  • Examples of the dispersant include fatty acid soap and ethylene glycol. The amount of pore-forming agent, binder, dispersant, and water can be adjusted as appropriate.
  • a sintered body such as a honeycomb structure having a low thermal expansion coefficient and excellent mechanical strength can be manufactured.
  • the columnar aluminum titanate of the present invention can be efficiently produced.
  • FIG. 1 is a scanning electron micrograph showing columnar aluminum titanate obtained in an example according to the present invention.
  • FIG. 2 is an enlarged scanning electron micrograph showing columnar aluminum titanate obtained in an example according to the present invention.
  • FIG. 3 is a diagram showing an X-ray diffraction chart of the columnar aluminum titanate obtained in Example 1 according to the present invention.
  • FIG. 4 is a view showing an X-ray diffraction chart of the columnar aluminum titanate obtained in Example 2 according to the present invention.
  • FIG. 5 is an X-ray diffraction chart of the columnar aluminum titanate obtained in Example 3 according to the present invention.
  • 6 is a diagram showing an X-ray diffraction chart of the aluminum titanate obtained in Comparative Example 1.
  • FIG. 7 is an X-ray diffraction chart of the aluminum titanate obtained in Comparative Example 2.
  • FIG. 8 is a perspective view showing a honeycomb structure.
  • FIG. 9 is a perspective view showing a measurement sample cut out from the honeycomb structure.
  • FIG. 10 is a schematic diagram for explaining a method for measuring the bending strength of a honeycomb structure.
  • FIG. 11 is a perspective view showing a measurement sample cut out from the honeycomb structure.
  • FIG. 12 is a perspective view showing a honeycomb structure.
  • FIG. 13 is a perspective view showing a measurement sample for measuring the X-ray diffraction of the extruded surface cut out from the honeycomb structure.
  • FIG. 14 is a perspective view showing a honeycomb structure.
  • FIG. 15 is a perspective view showing a measurement sample for measuring the X-ray diffraction of the vertical plane cut out from the honeycomb structure.
  • Example 1 322.7 g of titanium oxide, 428.9 g of aluminum oxide, 17.5 g of magnesium hydroxide and 30.9 g of silicon oxide were mixed for 2.0 hours while being pulverized with a vibration mill.
  • Aluminum oxide is mixed so that the amount of Al in the aluminum oxide is more than 2 mol relative to 1 mol of Ti in the titanium oxide.
  • aluminum oxide and titanium oxide are mixed so that the aluminum oxide is about 10% by weight excess with respect to 100 parts by weight of aluminum titanate.
  • 500 g of the pulverized mixed powder obtained as described above was charged in a crucible and baked at 1500 ° C. for 4 hours in an electric furnace.
  • FIG. 3 An X-ray diffraction chart of the obtained product is shown in FIG. As shown in FIG. 3, the obtained products were Al 2 TiO 5 , Al 6 Si 2 O 13, and Al 2 O 3 . The peaks shown in the lower part of FIG. 3 are peaks of Al 2 TiO 5 , Al 6 Si 2 O 13 and Al 2 O 3 of JCPDS, respectively.
  • the contents of Al 6 Si 2 O 13 and Al 2 O 3 contained in the obtained product were determined by quantification of an internal standard.
  • the content of Al 6 Si 2 O 13 was 5.3% by weight with respect to Al 2 TiO 5
  • the content of Al 2 O 3 was 5.1% by weight with respect to Al 2 TiO 5 .
  • Example 2 295.3 g of titanium oxide, 447.8 g of aluminum oxide, 16.0 g of magnesium hydroxide and 40.9 g of silicon oxide were mixed for 2.0 hours while being pulverized with a vibration mill.
  • Aluminum oxide is mixed so that the amount of Al in the aluminum oxide is more than 2 mol relative to 1 mol of Ti in the titanium oxide.
  • aluminum oxide and titanium oxide are mixed so as to be about 20 wt% excess as aluminum oxide with respect to 100 parts by weight of aluminum titanate.
  • 500 g of the pulverized mixed powder obtained as described above was charged in a crucible and baked at 1500 ° C. for 4 hours in an electric furnace.
  • FIG. 4 An X-ray diffraction chart of the obtained product is shown in FIG. As shown in FIG. 4, the obtained products were Al 2 TiO 5 , Al 6 Si 2 O 13, and Al 2 O 3 . The peaks shown in the lower part of FIG. 4 are peaks of JCPDS Al 2 TiO 5 , Al 6 Si 2 O 13 and Al 2 O 3 , respectively.
  • the contents of Al 6 Si 2 O 13 and Al 2 O 3 contained in the obtained product were determined by quantification of an internal standard.
  • the content of Al 6 Si 2 O 13 was 16.7 wt% with respect to Al 2 TiO 5
  • the content of Al 2 O 3 was 4.8 wt% with respect to Al 2 TiO 5 .
  • Example 3 272.2 g of titanium oxide, 463.8 g of aluminum oxide, 14.7 g of magnesium hydroxide and 49.3 g of silicon oxide were mixed for 2.0 hours while being pulverized with a vibration mill.
  • Aluminum oxide is mixed so that the amount of Al in the aluminum oxide is more than 2 mol relative to 1 mol of Ti in the titanium oxide.
  • aluminum oxide and titanium oxide are mixed so as to be about 30% by weight as aluminum oxide with respect to 100 parts by weight of aluminum titanate.
  • 500 g of the pulverized mixed powder obtained as described above was charged in a crucible and baked at 1500 ° C. for 4 hours in an electric furnace.
  • FIG. 5 An X-ray diffraction chart of the obtained product is shown in FIG. As shown in FIG. 5, the obtained products were Al 2 TiO 5 , Al 6 Si 2 O 13, and Al 2 O 3 . The peaks shown in the lower part of FIG. 5 are those of JCPDS Al 2 TiO 5 , Al 6 Si 2 O 13 and Al 2 O 3 , respectively.
  • the contents of Al 6 Si 2 O 13 and Al 2 O 3 contained in the obtained product were determined by quantification of an internal standard.
  • the content of Al 6 Si 2 O 13 was 23.1 wt% with respect to Al 2 TiO 5
  • the content of Al 2 O 3 was 5.3 wt% with respect to Al 2 TiO 5 .
  • Aluminum oxide is mixed so that Al in aluminum oxide is 2 mol with respect to 1 mol of Ti in titanium oxide.
  • 500 g of the pulverized mixed powder obtained as described above was charged in a crucible and baked at 1500 ° C. for 4 hours in an electric furnace.
  • FIG. 6 An X-ray diffraction chart of the obtained product is shown in FIG. As shown in FIG. 6, the product obtained was Al 2 TiO 5 . The peaks shown in the lower part of FIG. 6 are those of JCPDS Al 2 TiO 5 and Al 2 O 3 , respectively.
  • Aluminum oxide is mixed so that the amount of Al in the aluminum oxide is more than 2 mol relative to 1 mol of Ti in the titanium oxide.
  • aluminum is mixed with titanium oxide so as to be about 35% by weight as aluminum oxide with respect to 100 parts by weight of aluminum titanate.
  • 500 g of the pulverized mixed powder obtained as described above was charged in a crucible and baked in an electric furnace at 1500 ° C. for 4 hours.
  • FIG. 7 An X-ray diffraction chart of the obtained product is shown in FIG. As shown in FIG. 7, the obtained products were Al 2 TiO 5 , Al 6 Si 2 O 13, and Al 2 O 3 . The peaks shown in the lower part of FIG. 7 are the peaks of Al 2 TiO 5 , Al 6 Si 2 O 13 and Al 2 O 3 of JCPDS, respectively.
  • the contents of Al 6 Si 2 O 13 and Al 2 O 3 contained in the obtained product were determined by quantification of an internal standard.
  • the content of Al 6 Si 2 O 13 was 28.6 wt% with respect to Al 2 TiO 5
  • the content of Al 2 O 3 was 5.5 wt% with respect to Al 2 TiO 5 .
  • Example 3 The columnar aluminum titanate obtained in Example 1 was ground in an automatic mortar for 50 hours to obtain granular aluminum titanate.
  • FIG. 1 is a scanning electron micrograph (magnification 1000 times) showing this aluminum titanate. As is apparent from FIG. 1, columnar aluminum titanate is obtained.
  • FIG. 2 is a scanning electron microscope (magnification: 7000 times) showing the above-mentioned aluminum titanate in an enlarged manner. As shown in FIG. 2, mullite and aluminum oxide are attached to the surface of the aluminum titanate.
  • honeycomb sintered body Using the aluminum titanate obtained in each of the above Examples and Comparative Examples, a honeycomb sintered body was manufactured as follows.
  • the obtained kneaded material was extruded to form a honeycomb structure with an extrusion molding machine, and then dried with a hot air dryer, and then the resulting molded body was fired at 1500 ° C. to obtain a honeycomb sintered body. Obtained.
  • FIG. 8 is a perspective view showing a honeycomb sintered body (honeycomb structure). As shown in FIG. 8, the honeycomb sintered body 1 has 8 ⁇ 8 cells, and the end face 1a has a size of 1.8 cm in length and 1.8 cm in width. An arrow A indicates the extrusion direction, and an arrow B indicates a direction perpendicular to the extrusion direction A.
  • the porosity was measured by cutting a portion corresponding to 2 ⁇ 2 cells from the center portion 2 of the above 8 ⁇ 8 cell honeycomb sintered body 1 so that the length along the extrusion direction A was about 2 cm. It was.
  • FIG. 9 is a perspective view showing the measurement sample 3. Using the measurement sample 3 shown in FIG. 9, the porosity was measured in accordance with JIS R1634.
  • the length along the extrusion direction A from the central portion 2 of the 8 ⁇ 8 cell honeycomb sintered body 1 is about 2 cm. It cut out so that it might become, and it was set as the measurement sample 3. As shown in FIG. 11, the linear expansion coefficient in the extrusion direction A of the measurement sample 3 was measured according to JIS R1618.
  • Crystal orientation ratio The C-axis crystal orientation ratio of the obtained honeycomb sintered body was measured as the crystal orientation ratio.
  • the crystal orientation ratio was calculated from the crystal orientation degree in the extrusion direction and the crystal orientation degree in the direction perpendicular to the extrusion direction (vertical crystal orientation degree) as shown in the following formula.
  • Crystal orientation ratio Crystal orientation in extrusion direction / (Crystal orientation in extrusion direction + Crystal orientation in vertical direction)
  • the degree of crystal orientation was determined by X-ray diffraction.
  • the crystal orientation degree in the vertical direction was calculated by measuring X-ray diffraction of the vertical surface of the honeycomb sintered body and obtaining I (002) and I (230) in the same manner as described above.
  • 12 and 13 are perspective views showing the production of a measurement sample for measuring the X-ray diffraction of the extruded surface.
  • the region 4 including the end face 1a of the honeycomb sintered body 1 was cut out to produce a measurement sample shown in FIG.
  • the measurement sample 5 shown in FIG. 13 the X-ray diffraction of the extruded surface 5a of the measurement sample 5 was measured.
  • FIG. 14 and 15 are perspective views showing the production of a sample for measuring X-ray diffraction on a vertical plane, that is, a plane perpendicular to the extrusion plane.
  • a region 6 corresponding to 8 ⁇ 2 cells of the honeycomb sintered body 1 was cut out along the extrusion direction A to obtain a measurement sample 7 shown in FIG.
  • the measurement of the X-ray diffraction of the surface (extruded surface) 7a along the extrusion direction A of the measurement sample 7 was performed.
  • the (002) plane is a plane perpendicular to the C axis, and the high strength of the (002) plane means that the C axis is oriented.
  • the honeycomb sintered body using the columnar aluminum titanate of Examples 1 to 3 according to the present invention has higher bending strength than the honeycomb sintered body using the columnar aluminum titanate of Comparative Example 1. have. This is because the columnar aluminum titanate according to the present invention has mullite fine particles and aluminum oxide fine particles attached to the surface, and the mullite fine particles and aluminum oxide present on the surface act as a sintering aid and have excellent mechanical strength. This is considered to be because a sintered body is obtained.
  • the sintered bodies of Examples 1 to 3 have a lower linear expansion coefficient than the sintered body of Comparative Example 3. Since the crystal orientation ratio of Comparative Example 3 is lower than that of Examples 1 to 3, since the aspect ratio of Comparative Example 3 is small, the C-axis direction of aluminum titanate is not aligned with the extrusion direction of the honeycomb sintered body and is low. It is considered that the linear expansion coefficient was not obtained. In contrast, since the columnar aluminum titanates of Examples 1 to 3 have a large aspect ratio, the C-axis direction of aluminum titanate is aligned with the extrusion direction of the honeycomb sintered body, and a low linear expansion coefficient is obtained. It is considered a thing.
  • Comparative Example 2 since the mullite content is more than 25% by weight, the linear expansion coefficient is high. In addition, since the amount of mullite adhering is large, the aspect ratio of the powder is also small, which makes it difficult for aluminum titanate to be oriented in the extrusion direction, which also increases the linear expansion coefficient. It seems to be.
  • honeycomb sintered body honeycomb structure
  • DESCRIPTION OF SYMBOLS 1a End face of honeycomb structure 2 ... Center part of honeycomb structure 3 ... Measurement sample cut out from honeycomb structure 4 ... Area near end face of honeycomb structure 5 . X-ray diffraction measurement of extruded surface of honeycomb structure Sample 5a ... extruded surface 6 ... 8 ⁇ 2 cell region of honeycomb structure 7 ... Sample 7a ... vertical surface for X-ray diffraction measurement of vertical surface of honeycomb structure

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Abstract

Disclosed is a columnar aluminum titanate which enables the production of a sintered body such as a honeycomb structure that has a low thermal expansion coefficient and excellent mechanical strength. Also disclosed are a method for producing the columnar aluminum titanate, and a honeycomb structure which is produced using the columnar aluminum titanate. Specifically disclosed is a columnar aluminum titanate having an average aspect ratio (= (number average major axis length)/(number average minor axis length)) of not less than 1.3, which is characterized in that 5-25% by weight of mullite and 2-10% by weight of aluminum oxide, respectively relative to the columnar aluminum titanate, adhere to the surface of the columnar aluminum titanate.

Description

柱状チタン酸アルミニウム及びその製造方法並びにハニカム構造体Columnar aluminum titanate, method for producing the same, and honeycomb structure
　本発明は、柱状チタン酸アルミニウム及びその製造方法並びに該柱状チタン酸アルミニウムを用いて作製したハニカム構造体に関するものである。 The present invention relates to a columnar aluminum titanate, a manufacturing method thereof, and a honeycomb structure manufactured using the columnar aluminum titanate.
　チタン酸アルミニウムは、低熱膨張性で耐熱衝撃性に優れ、かつ融点が高いため、自動車の排ガス処理用触媒担体や、ディーゼルパティキュレートフィルタ（ＤＰＦ）等に用いられる多孔質材料として期待され、種々の開発が行われている。 Aluminum titanate is expected to be a porous material used in automobile exhaust gas treatment catalyst carriers, diesel particulate filters (DPFs), etc. because of its low thermal expansion, excellent thermal shock resistance, and high melting point. Development is underway.
　特許文献１においては、チタン酸アルミニウムが有する高融点、低熱膨張性を損なうことなく、高強度を有し、繰り返しの熱履歴に対して機械的強度の劣化が少ないチタン酸アルミニウム焼結体を得るため、チタン酸アルミニウムに、酸化マグネシウム及び酸化ケイ素を添加したものを焼結することが提案されている。 In Patent Document 1, an aluminum titanate sintered body having high strength and less mechanical strength deterioration with respect to repeated thermal history is obtained without impairing the high melting point and low thermal expansion property of aluminum titanate. Therefore, it has been proposed to sinter aluminum titanate added with magnesium oxide and silicon oxide.
　特許文献２においては、柱状チタン酸アルミニウムを用いて排ガスフィルタを製造することが開示されており、柱状粒子の長手方向が負の熱膨張係数であるとき長手方向と垂直な方向が正の熱膨張係数であるか、あるいは柱状粒子の長手方向が正の熱膨張係数であるとき長手方向と垂直な方向が負の熱膨張係数である排ガスフィルタを製造することが提案されている。 Patent Document 2 discloses that an exhaust gas filter is manufactured using columnar aluminum titanate, and when the longitudinal direction of the columnar particles has a negative thermal expansion coefficient, the direction perpendicular to the longitudinal direction is positive thermal expansion. It has been proposed to manufacture an exhaust gas filter that has a coefficient or a negative thermal expansion coefficient in the direction perpendicular to the longitudinal direction when the longitudinal direction of the columnar particles has a positive thermal expansion coefficient.
　しかしながら、柱状チタン酸アルミニウムの具体的な製造方法については開示されていない。 However, a specific method for producing columnar aluminum titanate is not disclosed.
　また、チタン酸アルミニウムを焼結して得られるハニカム構造体などの焼結体においては、焼結体の機械的強度を高めることが求められている。 Further, in a sintered body such as a honeycomb structure obtained by sintering aluminum titanate, it is required to increase the mechanical strength of the sintered body.
特開平１－２４９６５７号公報JP-A-1-249657 特開平９－２９０２３号公報JP-A-9-29023
　本発明の目的は、熱膨張係数が小さく、かつ機械的強度に優れたハニカム構造体などの焼結体を製造することができる柱状チタン酸アルミニウム及びその製造方法並びに該柱状チタン酸アルミニウムを用いて作製されるハニカム構造体を適用することにある。 An object of the present invention is to provide a columnar aluminum titanate capable of producing a sintered body such as a honeycomb structure having a small thermal expansion coefficient and excellent mechanical strength, a method for producing the same, and the columnar aluminum titanate. It is to apply the honeycomb structure to be manufactured.
　本発明の柱状チタン酸アルミニウムは、平均アスペクト比（＝個数平均長軸径／個数平均短軸径）が１．３以上の柱状チタン酸アルミニウムであって、柱状チタン酸アルミニウムに対し、５～２５重量％のムライト及び２～１０重量％の酸化アルミニウムが表面に付着していることを特徴としている。 The columnar aluminum titanate of the present invention is a columnar aluminum titanate having an average aspect ratio (= number average major axis diameter / number average minor axis diameter) of 1.3 or more, and is 5 to 25 relative to the columnar aluminum titanate. It is characterized by adhering to the surface by weight percent mullite and 2-10 weight percent aluminum oxide.
　本発明の柱状チタン酸アルミニウムは、平均アスペクト比（＝個数平均長軸径／個数平均短軸径）が１．３以上である。このため、ハニカム構造体のように押出成形した成形体を焼結して製造する焼結体においては、柱状チタン酸アルミニウム粒子の長手方向が押出方向に整列されやすいため、押出方向に線膨張係数が小さいハニカム構造体を製造することができる。 The columnar aluminum titanate of the present invention has an average aspect ratio (= number average major axis diameter / number average minor axis diameter) of 1.3 or more. For this reason, in a sintered body produced by sintering an extruded molded body such as a honeycomb structure, the longitudinal direction of the columnar aluminum titanate particles is easily aligned with the extrusion direction. Can be produced.
　また、本発明においては、柱状チタン酸アルミニウムに対し、５～２５重量％のムライト及び２～１０重量％の酸化アルミニウムが表面に付着しているので、焼結する際に、この表面のムライト及び酸化アルミニウムが焼結助剤として機能し、高い機械的強度を有する焼結体を得ることができる。 In the present invention, 5 to 25% by weight of mullite and 2 to 10% by weight of aluminum oxide are attached to the surface with respect to the columnar aluminum titanate. Aluminum oxide functions as a sintering aid, and a sintered body having high mechanical strength can be obtained.
　本発明において、平均アスペクト比の上限値は、特に限定されるものではないが、一般には、５以下である。 In the present invention, the upper limit of the average aspect ratio is not particularly limited, but is generally 5 or less.
　ムライトの付着量は、上述のように柱状チタン酸アルミニウムに対し５～２５重量％である。従って、柱状チタン酸アルミニウム１００重量部に対して、５～２５重量部のムライトがチタン酸アルミニウムの表面に付着している。ムライトの付着量が５重量％未満であると、高い機械的強度を有する焼結体を得ることができない。また、ムライトの付着量が２５重量％を越えると、ムライトの熱膨張係数がチタン酸アルミニウムよりも大きいので、焼結体の熱膨張係数を小さくすることができなくなる。 The amount of mullite deposited is 5 to 25% by weight based on the columnar aluminum titanate as described above. Therefore, 5 to 25 parts by weight of mullite adheres to the surface of the aluminum titanate with respect to 100 parts by weight of the columnar aluminum titanate. When the amount of mullite attached is less than 5% by weight, a sintered body having high mechanical strength cannot be obtained. If the adhesion amount of mullite exceeds 25% by weight, the thermal expansion coefficient of mullite is larger than that of aluminum titanate, so that the thermal expansion coefficient of the sintered body cannot be reduced.
　酸化アルミニウムの付着量は、上述のように柱状チタン酸アルミニウムに対し２～１０重量％であり、さらに好ましくは４～６重量％である。従って、柱状チタン酸アルミニウム１００重量部に対し、２～１０重量部の酸化アルミニウムがチタン酸アルミニウムの表面に付着している。酸化アルミニウムの付着量が２重量％未満であると、高い機械的強度を有する焼結体を得ることができない。また、酸化アルミニウムの付着量が１０重量部を越えると、酸化アルミニウムの熱膨張係数がチタン酸アルミニウムよりも大きいので、焼結体の熱膨張係数を小さくすることができなくなる。 The adhesion amount of aluminum oxide is 2 to 10% by weight, more preferably 4 to 6% by weight, based on the columnar aluminum titanate as described above. Therefore, 2 to 10 parts by weight of aluminum oxide is adhered to the surface of aluminum titanate with respect to 100 parts by weight of columnar aluminum titanate. When the adhesion amount of aluminum oxide is less than 2% by weight, a sintered body having high mechanical strength cannot be obtained. On the other hand, when the adhesion amount of aluminum oxide exceeds 10 parts by weight, the thermal expansion coefficient of aluminum oxide is larger than that of aluminum titanate, so that the thermal expansion coefficient of the sintered body cannot be reduced.
　本発明において、柱状チタン酸アルミニウムの個数平均短軸径は、１０μｍ以下であることが好ましい。個数平均短軸径は、５～１０μｍの範囲内であることがさらに好ましい。また、個数平均長軸径は、７～１７μｍの範囲内であることが好ましい。 In the present invention, the number average minor axis diameter of the columnar aluminum titanate is preferably 10 μm or less. The number average minor axis diameter is more preferably in the range of 5 to 10 μm. The number average major axis diameter is preferably in the range of 7 to 17 μm.
　柱状チタン酸アルミニウムの個数平均長軸径及び個数平均短軸径は、例えば、フロー式粒子像分析装置により測定することができる。 The number average major axis diameter and the number average minor axis diameter of the columnar aluminum titanate can be measured by, for example, a flow type particle image analyzer.
　本発明において、柱状チタン酸アルミニウムの表面に付着しているムライト及び酸化アルミニウムは微粒子であり、一般には、５０ｎｍ～５００ｎｍの範囲内の平均粒子径を有しており、さらに好ましくは１００ｎｍ～３００ｎｍの範囲内の平均粒子径を有している。 In the present invention, the mullite and aluminum oxide adhering to the surface of the columnar aluminum titanate are fine particles, and generally have an average particle diameter in the range of 50 nm to 500 nm, more preferably 100 nm to 300 nm. It has an average particle size within the range.
　なお、ムライト及び酸化アルミニウムの平均粒子径は、走査型電子顕微鏡（ＳＥＭ）による観察で測定することができる。 The average particle size of mullite and aluminum oxide can be measured by observation with a scanning electron microscope (SEM).
　本発明の製造方法は、上記本発明の柱状チタン酸アルミニウムを製造することができる方法であり、チタン源、アルミニウム源、ケイ素源、及びマグネシウム源を含む原料をメカノケミカルに粉砕しながら混合する工程と、粉砕した混合物を焼成する工程とを備えることを特徴としている。 The production method of the present invention is a method capable of producing the columnar aluminum titanate of the present invention, wherein the raw material containing a titanium source, an aluminum source, a silicon source, and a magnesium source is mixed while being mechanochemically ground. And a step of firing the pulverized mixture.
　チタン酸アルミニウム（Ａｌ２ＴｉＯ５）は、チタン（Ｔｉ）１モルに対し、アルミニウム（Ａｌ）が２モル含まれている。Ｔｉ１モルに対し、２モルより多くのＡｌとなるようにチタン源及びアルミニウム源を混合することにより、２モルを越えるＡｌは、柱状チタン酸アルミニウムの表面に付着するムライト及び酸化アルミニウムとなる。ムライト（Ａｌ６Ｓｉ２Ｏ１３）は、ケイ素（Ｓｉ）を含んでいるので、原料中にケイ素源を含む必要がある。原料中に含まれるケイ素源の一部がムライトを構成するケイ素となる。Ｔｉ１モルに対して、Ａｌが２モルより過剰な量となるようにチタン源とアルミニウム源を含有し、さらにケイ素源を含有した原料を用いることにより、本発明の柱状チタン酸アルミニウムを製造することができる。 Aluminum titanate (Al 2 TiO 5 ) contains 2 moles of aluminum (Al) with respect to 1 mole of titanium (Ti). By mixing the titanium source and the aluminum source so that the amount of Al is more than 2 mol per 1 mol of Ti, Al exceeding 2 mol becomes mullite and aluminum oxide adhering to the surface of the columnar aluminum titanate. Since mullite (Al 6 Si 2 O 13 ) contains silicon (Si), it is necessary to include a silicon source in the raw material. Part of the silicon source contained in the raw material becomes silicon constituting mullite. The columnar aluminum titanate of the present invention is produced by using a raw material containing a titanium source and an aluminum source so that Al is more than 2 mol relative to 1 mol of Ti, and further containing a silicon source. Can do.
　また、チタン源、アルミニウム源、ケイ素源、及びマグネシウム源を含む原料を、メカノケミカルに粉砕しながら混合した粉砕混合物を用い、この粉砕混合物を焼成することにより、平均アスペクト比が１．３以上である柱状のチタン酸アルミニウムを製造することができる。すなわち、原料中にマグネシウム源を含み、かつメカノケミカルに粉砕しながら混合した粉砕混合物を用いることにより、柱状のチタン酸アルミニウムを製造することができる。 In addition, by using a pulverized mixture obtained by mixing raw materials including a titanium source, an aluminum source, a silicon source, and a magnesium source while being pulverized into mechanochemicals, the average aspect ratio is 1.3 or more by firing the pulverized mixture. A columnar aluminum titanate can be produced. That is, columnar aluminum titanate can be produced by using a pulverized mixture that contains a magnesium source in the raw material and is mixed while being mechanochemically pulverized.
　粉砕混合物を焼成する温度としては、１３００～１６００℃の範囲内の温度であることが好ましい。このような温度範囲内で焼成することにより、本発明の柱状チタン酸アルミニウムをより効率的に製造することができる。 The temperature for firing the pulverized mixture is preferably a temperature in the range of 1300 to 1600 ° C. By firing within such a temperature range, the columnar aluminum titanate of the present invention can be produced more efficiently.
　焼成時間は、特に限定されるものではないが、０．５時間～２０時間の範囲内で行うことが好ましい。 Calcination time is not particularly limited, but it is preferably performed within a range of 0.5 hours to 20 hours.
　本発明の製造方法において、メカノケミカルな粉砕としては、物理的な衝撃を与えながら粉砕する方法が挙げられる。具体的には、振動ミルによる粉砕が挙げられる。振動ミルによる粉砕処理を行うことにより、混合粉体の摩砕による剪断応力によって、原子配列の乱れと原子間距離の減少が同時に起こり、異種粒子の接点部分の原子移動が起こる結果、準安定相が得られると考えられる。これにより、反応活性の高い粉砕混合物が得られ、この反応活性の高い粉砕混合物を焼成することにより、上記本発明の柱状チタン酸アルミニウムを製造することができる。 In the production method of the present invention, the mechanochemical pulverization includes a method of pulverizing while giving a physical impact. Specifically, pulverization by a vibration mill can be mentioned. By pulverizing with a vibration mill, the disruption of atomic arrangement and the decrease in interatomic distance occur simultaneously due to the shear stress caused by the grinding of the mixed powder, resulting in atomic movement of the contact part of different particles, resulting in a metastable phase. Can be obtained. Thereby, a pulverized mixture with high reaction activity is obtained, and the columnar aluminum titanate of the present invention can be produced by firing the pulverized mixture with high reaction activity.
　本発明におけるメカノケミカルな粉砕は、一般に、水や溶剤を用いない乾式処理として行われる。 The mechanochemical pulverization in the present invention is generally performed as a dry process without using water or a solvent.
　メカノケミカルな粉砕による混合処理の時間は特に限定されるものではないが、一般には０．１時間～６時間の範囲内であることが好ましい。 The mixing treatment time by mechanochemical pulverization is not particularly limited, but generally it is preferably within the range of 0.1 to 6 hours.
　本発明において用いる原料には、チタン源、アルミニウム源、ケイ素源、及びマグネシウム源が含まれる。チタン源としては、酸化チタンを含有する化合物を用いることができ、具体的には、酸化チタン、ルチル鉱石、水酸化チタンウェットケーキ、含水チタニアなどが挙げられる。 The raw materials used in the present invention include a titanium source, an aluminum source, a silicon source, and a magnesium source. As the titanium source, a compound containing titanium oxide can be used. Specific examples include titanium oxide, rutile ore, titanium hydroxide wet cake, and hydrous titania.
　アルミニウム源としては、加熱により酸化アルミニウムを生じる化合物を用いることができ、具体的には、酸化アルミニウム、水酸化アルミニウム、硫酸アルミニウムなどが挙げられる。これらの中でも、特に酸化アルミニウムが好ましく用いられる。 As the aluminum source, a compound that generates aluminum oxide by heating can be used. Specific examples include aluminum oxide, aluminum hydroxide, and aluminum sulfate. Among these, aluminum oxide is particularly preferably used.
　マグネシウム源としては、加熱により酸化マグネシウムを生じる化合物を用いることができ、具体的には、水酸化マグネシウム、酸化マグネシウム、炭酸マグネシウムなどが挙げられる。これらの中でも、特に水酸化マグネシウム及び酸化マグネシウムが好ましく用いられる。 As the magnesium source, a compound that generates magnesium oxide by heating can be used, and specific examples include magnesium hydroxide, magnesium oxide, and magnesium carbonate. Among these, magnesium hydroxide and magnesium oxide are particularly preferably used.
　マグネシウム源は、チタン源及びアルミニウム源の合計に対してそれぞれ酸化物換算で０．５～２．０重量％の範囲内となるように原料中に含まれていることが好ましい。０．５重量％未満であると、低い熱膨張係数及び高い機械的強度を有する焼結体が得られない場合がある。また、２．０重量％より多くなると、平均アスペクト比が１．３以上である柱状チタン酸アルミニウムが得られない場合がある。 The magnesium source is preferably contained in the raw material so as to be in the range of 0.5 to 2.0% by weight in terms of oxide with respect to the total of the titanium source and the aluminum source. If it is less than 0.5% by weight, a sintered body having a low coefficient of thermal expansion and high mechanical strength may not be obtained. On the other hand, if it exceeds 2.0% by weight, columnar aluminum titanate having an average aspect ratio of 1.3 or more may not be obtained.
　また、本発明の製造方法においては、原料中にケイ素源がさらに含まれている。 In the production method of the present invention, the raw material further contains a silicon source.
　ケイ素源が含有させることにより、チタン酸アルミニウムの表面にムライトを析出させることができるとともに、チタン酸アルミニウムの分解を抑制することができ、高温安定性に優れた柱状チタン酸アルミニウムを製造することができる。 By including the silicon source, mullite can be deposited on the surface of the aluminum titanate, decomposition of the aluminum titanate can be suppressed, and columnar aluminum titanate having excellent high-temperature stability can be produced. it can.
　ケイ素源としては、酸化ケイ素、ケイ素などが挙げられる。これらの中でも、特に酸化ケイ素が好ましく用いられる。ケイ素源の原料中における含有量は、チタン源及びアルミニウム源の合計に対してそれぞれの酸化物換算で、３～７重量％の範囲内であることが好ましい。このような範囲内とすることにより、柱状チタン酸アルミニウムをより安定して製造することができる。 Examples of the silicon source include silicon oxide and silicon. Among these, silicon oxide is particularly preferably used. The content of the silicon source in the raw material is preferably in the range of 3 to 7% by weight in terms of the respective oxides with respect to the total of the titanium source and the aluminum source. By setting it within such a range, columnar aluminum titanate can be more stably produced.
　アルミニウム源は、上述のように、Ｔｉ１モルに対してＡｌが２モルより過剰となる量を原料中に含有させる。表面に付着させるムライト及び酸化アルミニウムの量を考慮して、Ｔｉに対し過剰な量となるアルミニウム源の量を調整する。 As described above, the aluminum source contains, in the raw material, an amount in which Al is more than 2 mol relative to 1 mol of Ti. In consideration of the amount of mullite and aluminum oxide deposited on the surface, the amount of the aluminum source that is excessive with respect to Ti is adjusted.
　本発明の柱状チタン酸アルミニウムを焼結した焼結体は、上述のように、表面にムライト及び酸化アルミニウムが付着しており、このムライト及び酸化アルミニウムが焼結助剤として働くので、機械的強度の高い焼結体とすることができる。 As described above, the sintered body obtained by sintering the columnar aluminum titanate of the present invention has mullite and aluminum oxide attached to the surface, and since the mullite and aluminum oxide serve as a sintering aid, mechanical strength is increased. High sintered body.
　本発明のハニカム構造体は、上記本発明の柱状チタン酸アルミニウムを用いて作製したハニカム構造体であり、ハニカム構造体の押出方向の３０～８００℃の間の熱膨張係数が１．０×１０－６／℃以下であり、ハニカム押出方向に対するＣ軸の結晶配向比が０．７５以上であることを特徴としている。 The honeycomb structure of the present invention is a honeycomb structure manufactured using the columnar aluminum titanate of the present invention, and has a thermal expansion coefficient of 1.0 × 10 6 between 30 and 800 ° C. in the extrusion direction of the honeycomb structure. It is −6 / ° C. or less, and the crystal orientation ratio of the C axis with respect to the honeycomb extrusion direction is 0.75 or more.
　ハニカム構造体の押出方向の３０～８００℃の間の熱膨張係数が１．０×１０－６／℃以下であるので、耐熱衝撃性に優れた特性を得ることができる。 Since the thermal expansion coefficient between 30 and 800 ° C. in the extrusion direction of the honeycomb structure is 1.0 × 10 −6 / ° C. or less, it is possible to obtain characteristics excellent in thermal shock resistance.
　ハニカム構造体の押出方向の熱膨張係数の下限値は、特に限定されるものではないが、一般には－１．０×１０－６／℃以上である。 The lower limit value of the thermal expansion coefficient in the extrusion direction of the honeycomb structure is not particularly limited, but is generally −1.0 × 10 −6 / ° C. or more.
　また、ハニカム押出方向に対するＣ軸の結晶配向比は、０．７５以上である。ハニカム押出方向に対するＣ軸の結晶配向比が０．７５以上であることにより、ハニカム構造体の押出方向における熱膨張係数を小さくすることができる。 Further, the crystal orientation ratio of the C axis with respect to the honeycomb extrusion direction is 0.75 or more. When the crystal orientation ratio of the C axis with respect to the honeycomb extrusion direction is 0.75 or more, the thermal expansion coefficient in the extrusion direction of the honeycomb structure can be reduced.
　本発明におけるハニカム押出方向に対するＣ軸の結晶配向比は、以下の式から求めることができる。 The crystal orientation ratio of the C axis relative to the honeycomb extrusion direction in the present invention can be obtained from the following equation.
　ハニカム押出方向のＣ軸の結晶配向比＝Ａ／（Ａ＋Ｂ）
　Ａ：ハニカム押出方向のＣ軸配向度＝Ｉ００２／（Ｉ００２＋Ｉ２３０）
　Ｂ：ハニカム垂直方向のＣ軸配向度＝Ｉ００２／（Ｉ００２＋Ｉ２３０） C-axis crystal orientation ratio in the honeycomb extrusion direction = A / (A + B)
A: C-axis orientation in honeycomb extrusion direction = I 002 / (I 002 + I 230 )
B: C-axis orientation in the vertical direction of the honeycomb = I 002 / (I 002 + I 230 )
　Ｉ００２及びＩ２３０は、押出方向については押出面を、垂直方向については垂直面をＸ線回折したときの（００２）面のピーク強度（Ｉ００２）及び（２３０）面のピーク強度（Ｉ２３０）である。 I 002 and I 230 are the extrusion surface for extrusion direction, the peak intensity of the (002) plane when the X-ray diffraction vertical plane in the vertical direction (I 002) and (230) plane peak intensity (I 230 ).
　本発明の柱状チタン酸アルミニウムは、柱状体の長手方向に沿ってＣ軸が延びている。このため、ハニカム構造体を押出成形した際、押出方向にＣ軸が整列するため、押出方向の熱膨張係数を低くすることができる。 In the columnar aluminum titanate of the present invention, the C axis extends along the longitudinal direction of the columnar body. For this reason, when the honeycomb structure is extruded, the C-axis is aligned in the extrusion direction, so that the thermal expansion coefficient in the extrusion direction can be lowered.
　本発明のハニカム構造体は、チタン酸アルミニウムに、例えば、造孔剤、バインダー、分散剤、及び水を添加した混合組成物を作製し、これを、例えば押出成形機を用いてハニカム構造体となるように成形し、セルの開口が市松模様となるように片側の目封止を行った後、乾燥して得られた成形体を焼成して製造することができる。焼成温度としては、例えば、１４００～１６００℃が挙げられる。 The honeycomb structure of the present invention is produced by preparing a mixed composition in which, for example, a pore forming agent, a binder, a dispersant, and water are added to aluminum titanate, and this is used to form a honeycomb structure using, for example, an extruder. It can shape | mold so that it may form, and after performing the plugging of one side so that the opening of a cell may become a checkered pattern, the molded object obtained by drying can be baked and manufactured. Examples of the firing temperature include 1400 to 1600 ° C.
　造孔剤としては、黒鉛、グラファイト、木粉、ポリエチレンが挙げられる。また、バインダーとしては、メチルセルロース、エチルセルロース、ポリビニルアルコールが挙げられる。分散剤としては、脂肪酸石鹸、エチレングリコールが挙げられる。造孔剤、バインダー、分散剤、及び水の量は適宜調整することができる。 Examples of pore-forming agents include graphite, graphite, wood powder, and polyethylene. Examples of the binder include methyl cellulose, ethyl cellulose, and polyvinyl alcohol. Examples of the dispersant include fatty acid soap and ethylene glycol. The amount of pore-forming agent, binder, dispersant, and water can be adjusted as appropriate.
　本発明によれば、熱膨張係数が小さく、かつ機械的強度に優れたハニカム構造体などの焼結体を製造することができる。 According to the present invention, a sintered body such as a honeycomb structure having a low thermal expansion coefficient and excellent mechanical strength can be manufactured.
　本発明の製造方法によれば、本発明の柱状チタン酸アルミニウムを効率良く製造することができる。 According to the production method of the present invention, the columnar aluminum titanate of the present invention can be efficiently produced.
図１は、本発明に従う実施例において得られた柱状チタン酸アルミニウムを示す走査型電子顕微鏡写真の図である。FIG. 1 is a scanning electron micrograph showing columnar aluminum titanate obtained in an example according to the present invention. 図２は、本発明に従う実施例において得られた柱状チタン酸アルミニウムを拡大して示す走査型電子顕微鏡写真である。FIG. 2 is an enlarged scanning electron micrograph showing columnar aluminum titanate obtained in an example according to the present invention. 図３は、本発明に従う実施例１で得られた柱状チタン酸アルミニウムのＸ線回折チャートを示す図である。FIG. 3 is a diagram showing an X-ray diffraction chart of the columnar aluminum titanate obtained in Example 1 according to the present invention. 図４は、本発明に従う実施例２で得られた柱状チタン酸アルミニウムのＸ線回折チャートを示す図である。FIG. 4 is a view showing an X-ray diffraction chart of the columnar aluminum titanate obtained in Example 2 according to the present invention. 図５は、本発明に従う実施例３で得られた柱状チタン酸アルミニウムのＸ線回折チャートを示す図である。FIG. 5 is an X-ray diffraction chart of the columnar aluminum titanate obtained in Example 3 according to the present invention. 図６は、比較例１で得られたチタン酸アルミニウムのＸ線回折チャートを示す図である。6 is a diagram showing an X-ray diffraction chart of the aluminum titanate obtained in Comparative Example 1. FIG. 図７は、比較例２で得られたチタン酸アルミニウムのＸ線回折チャートを示す図である。FIG. 7 is an X-ray diffraction chart of the aluminum titanate obtained in Comparative Example 2. 図８は、ハニカム構造体を示す斜視図である。FIG. 8 is a perspective view showing a honeycomb structure. 図９は、ハニカム構造体から切り出した測定サンプルを示す斜視図である。FIG. 9 is a perspective view showing a measurement sample cut out from the honeycomb structure. 図１０は、ハニカム構造体の曲げ強度の測定方法を説明するための模式図である。FIG. 10 is a schematic diagram for explaining a method for measuring the bending strength of a honeycomb structure. 図１１は、ハニカム構造体から切り出した測定サンプルを示す斜視図である。FIG. 11 is a perspective view showing a measurement sample cut out from the honeycomb structure. 図１２は、ハニカム構造体を示す斜視図である。FIG. 12 is a perspective view showing a honeycomb structure. 図１３は、ハニカム構造体から切り出した押出面のＸ線回折を測定するための測定サンプルを示す斜視図である。FIG. 13 is a perspective view showing a measurement sample for measuring the X-ray diffraction of the extruded surface cut out from the honeycomb structure. 図１４は、ハニカム構造体を示す斜視図である。FIG. 14 is a perspective view showing a honeycomb structure. 図１５は、ハニカム構造体から切り出した垂直面のＸ線回折を測定するための測定サンプルを示す斜視図である。FIG. 15 is a perspective view showing a measurement sample for measuring the X-ray diffraction of the vertical plane cut out from the honeycomb structure.
　以下、本発明を具体的な実施例により詳細に説明するが、本発明は以下の実施例に限定されるものではない。 Hereinafter, the present invention will be described in detail with specific examples, but the present invention is not limited to the following examples.
　〔柱状チタン酸アルミニウムの製造〕
　（実施例１）
　酸化チタン３２２．７ｇ、酸化アルミニウム４２８．９ｇ、水酸化マグネシウム１７．５ｇ及び酸化ケイ素３０．９ｇを振動ミルにて粉砕しながら、２．０時間混合した。 [Production of columnar aluminum titanate]
Example 1
322.7 g of titanium oxide, 428.9 g of aluminum oxide, 17.5 g of magnesium hydroxide and 30.9 g of silicon oxide were mixed for 2.0 hours while being pulverized with a vibration mill.
　酸化アルミニウムは、酸化チタン中のＴｉ１モルに対し、酸化アルミニウム中のＡｌが２モルより過剰量となるように混合されている。本実施例では、チタン酸アルミニウム１００重量部に対し、酸化アルミニウムとして約１０重量％過剰となるように酸化アルミニウムと酸化チタンが混合されている。 Aluminum oxide is mixed so that the amount of Al in the aluminum oxide is more than 2 mol relative to 1 mol of Ti in the titanium oxide. In this embodiment, aluminum oxide and titanium oxide are mixed so that the aluminum oxide is about 10% by weight excess with respect to 100 parts by weight of aluminum titanate.
　以上のようにして得られた粉砕混合粉５００ｇをルツボに充填し、電気炉にて１５００℃で４時間焼成した。 500 g of the pulverized mixed powder obtained as described above was charged in a crucible and baked at 1500 ° C. for 4 hours in an electric furnace.
　得られた生成物のＸ線回折チャートを図３に示す。図３に示すように、得られた生成物は、Ａｌ２ＴｉＯ５とＡｌ６Ｓｉ２Ｏ１３とＡｌ２Ｏ３であった。図３の下方に示すピークは、それぞれＪＣＰＤＳのＡｌ２ＴｉＯ５、Ａｌ６Ｓｉ２Ｏ１３及びＡｌ２Ｏ３のピークである。 An X-ray diffraction chart of the obtained product is shown in FIG. As shown in FIG. 3, the obtained products were Al 2 TiO 5 , Al 6 Si 2 O 13, and Al 2 O 3 . The peaks shown in the lower part of FIG. 3 are peaks of Al 2 TiO 5 , Al 6 Si 2 O 13 and Al 2 O 3 of JCPDS, respectively.
　得られた生成物中に含まれるＡｌ６Ｓｉ２Ｏ１３及びＡｌ２Ｏ３の含有量を、内部標準の定量により求めた。Ａｌ６Ｓｉ２Ｏ１３の含有量は、Ａｌ２ＴｉＯ５に対し５．３重量％であり、Ａｌ２Ｏ３の含有量は、Ａｌ２ＴｉＯ５に対し５．１重量％であった。 The contents of Al 6 Si 2 O 13 and Al 2 O 3 contained in the obtained product were determined by quantification of an internal standard. The content of Al 6 Si 2 O 13 was 5.3% by weight with respect to Al 2 TiO 5 , and the content of Al 2 O 3 was 5.1% by weight with respect to Al 2 TiO 5 .
　フロー式粒子像分析により、得られた生成物の個数平均長軸径及び個数平均短軸径を測定し、アスペクト比（＝個数平均長軸径／個数平均短軸径）を算出した。測定結果を表１に示す。 The number average major axis diameter and the number average minor axis diameter of the obtained product were measured by flow type particle image analysis, and the aspect ratio (= number average major axis diameter / number average minor axis diameter) was calculated. The measurement results are shown in Table 1.
　（実施例２）
　酸化チタン２９５．３ｇ、酸化アルミニウム４４７．８ｇ、水酸化マグネシウム１６．０ｇ及び酸化ケイ素４０．９ｇを振動ミルにて粉砕しながら、２．０時間混合した。 (Example 2)
295.3 g of titanium oxide, 447.8 g of aluminum oxide, 16.0 g of magnesium hydroxide and 40.9 g of silicon oxide were mixed for 2.0 hours while being pulverized with a vibration mill.
　酸化アルミニウムは、酸化チタン中のＴｉ１モルに対し、酸化アルミニウム中のＡｌが２モルより過剰量となるように混合されている。本実施例では、チタン酸アルミニウム１００重量部に対し、酸化アルミニウムとして約２０重量％過剰となるように酸化アルミニウムと酸化チタンが混合されている。 Aluminum oxide is mixed so that the amount of Al in the aluminum oxide is more than 2 mol relative to 1 mol of Ti in the titanium oxide. In this embodiment, aluminum oxide and titanium oxide are mixed so as to be about 20 wt% excess as aluminum oxide with respect to 100 parts by weight of aluminum titanate.
　以上のようにして得られた粉砕混合粉５００ｇをルツボに充填し、電気炉にて１５００℃で４時間焼成した。 500 g of the pulverized mixed powder obtained as described above was charged in a crucible and baked at 1500 ° C. for 4 hours in an electric furnace.
　得られた生成物のＸ線回折チャートを図４に示す。図４に示すように、得られた生成物は、Ａｌ２ＴｉＯ５とＡｌ６Ｓｉ２Ｏ１３とＡｌ２Ｏ３であった。図４の下方に示すピークは、それぞれＪＣＰＤＳのＡｌ２ＴｉＯ５、Ａｌ６Ｓｉ２Ｏ１３及びＡｌ２Ｏ３のピークである。 An X-ray diffraction chart of the obtained product is shown in FIG. As shown in FIG. 4, the obtained products were Al 2 TiO 5 , Al 6 Si 2 O 13, and Al 2 O 3 . The peaks shown in the lower part of FIG. 4 are peaks of JCPDS Al 2 TiO 5 , Al 6 Si 2 O 13 and Al 2 O 3 , respectively.
　得られた生成物中に含まれるＡｌ６Ｓｉ２Ｏ１３及びＡｌ２Ｏ３の含有量を、内部標準の定量により求めた。Ａｌ６Ｓｉ２Ｏ１３の含有量は、Ａｌ２ＴｉＯ５に対し１６．７重量％であり、Ａｌ２Ｏ３の含有量は、Ａｌ２ＴｉＯ５に対し４．８重量％であった。 The contents of Al 6 Si 2 O 13 and Al 2 O 3 contained in the obtained product were determined by quantification of an internal standard. The content of Al 6 Si 2 O 13 was 16.7 wt% with respect to Al 2 TiO 5 , and the content of Al 2 O 3 was 4.8 wt% with respect to Al 2 TiO 5 .
　フロー式粒子像分析により、得られた生成物の個数平均長軸径及び個数平均短軸径を測定し、アスペクト比（＝個数平均長軸径／個数平均短軸径）を算出した。測定結果を表１に示す。 The number average major axis diameter and the number average minor axis diameter of the obtained product were measured by flow type particle image analysis, and the aspect ratio (= number average major axis diameter / number average minor axis diameter) was calculated. The measurement results are shown in Table 1.
　（実施例３）
　酸化チタン２７２．２ｇ、酸化アルミニウム４６３．８ｇ、水酸化マグネシウム１４．７ｇ及び酸化ケイ素４９．３ｇを振動ミルにて粉砕しながら、２．０時間混合した。 (Example 3)
272.2 g of titanium oxide, 463.8 g of aluminum oxide, 14.7 g of magnesium hydroxide and 49.3 g of silicon oxide were mixed for 2.0 hours while being pulverized with a vibration mill.
　酸化アルミニウムは、酸化チタン中のＴｉ１モルに対し、酸化アルミニウム中のＡｌが２モルより過剰量となるように混合されている。本実施例では、チタン酸アルミニウム１００重量部に対し、酸化アルミニウムとして約３０重量％過剰となるように酸化アルミニウムと酸化チタンが混合されている。 Aluminum oxide is mixed so that the amount of Al in the aluminum oxide is more than 2 mol relative to 1 mol of Ti in the titanium oxide. In this embodiment, aluminum oxide and titanium oxide are mixed so as to be about 30% by weight as aluminum oxide with respect to 100 parts by weight of aluminum titanate.
　以上のようにして得られた粉砕混合粉５００ｇをルツボに充填し、電気炉にて１５００℃で４時間焼成した。 500 g of the pulverized mixed powder obtained as described above was charged in a crucible and baked at 1500 ° C. for 4 hours in an electric furnace.
　得られた生成物のＸ線回折チャートを図５に示す。図５に示すように、得られた生成物は、Ａｌ２ＴｉＯ５とＡｌ６Ｓｉ２Ｏ１３とＡｌ２Ｏ３であった。図５の下方に示すピークは、それぞれＪＣＰＤＳのＡｌ２ＴｉＯ５、Ａｌ６Ｓｉ２Ｏ１３と及びＡｌ２Ｏ３のピークである。 An X-ray diffraction chart of the obtained product is shown in FIG. As shown in FIG. 5, the obtained products were Al 2 TiO 5 , Al 6 Si 2 O 13, and Al 2 O 3 . The peaks shown in the lower part of FIG. 5 are those of JCPDS Al 2 TiO 5 , Al 6 Si 2 O 13 and Al 2 O 3 , respectively.
　得られた生成物中に含まれるＡｌ６Ｓｉ２Ｏ１３及びＡｌ２Ｏ３の含有量を、内部標準の定量により求めた。Ａｌ６Ｓｉ２Ｏ１３の含有量は、Ａｌ２ＴｉＯ５に対し２３．１重量％であり、Ａｌ２Ｏ３の含有量は、Ａｌ２ＴｉＯ５に対し５．３重量％であった。 The contents of Al 6 Si 2 O 13 and Al 2 O 3 contained in the obtained product were determined by quantification of an internal standard. The content of Al 6 Si 2 O 13 was 23.1 wt% with respect to Al 2 TiO 5 , and the content of Al 2 O 3 was 5.3 wt% with respect to Al 2 TiO 5 .
　フロー式粒子像分析により、得られた生成物の個数平均長軸径及び個数平均短軸径を測定し、アスペクト比（＝個数平均長軸径／個数平均短軸径）を算出した。測定結果を表１に示す。 The number average major axis diameter and the number average minor axis diameter of the obtained product were measured by flow type particle image analysis, and the aspect ratio (= number average major axis diameter / number average minor axis diameter) was calculated. The measurement results are shown in Table 1.
　（比較例１）
　酸化チタン３３４．７ｇ、酸化アルミニウム４２７．３ｇ、水酸化マグネシウム１７．９ｇ及び酸化ケイ素２０．１ｇを振動ミルにて粉砕しながら、２．０時間混合した。 (Comparative Example 1)
334.7 g of titanium oxide, 427.3 g of aluminum oxide, 17.9 g of magnesium hydroxide and 20.1 g of silicon oxide were mixed for 2.0 hours while being pulverized by a vibration mill.
　酸化アルミニウムは、酸化チタン中のＴｉ１モルに対し、酸化アルミニウム中のＡｌが２モルとなるように混合されている。 Aluminum oxide is mixed so that Al in aluminum oxide is 2 mol with respect to 1 mol of Ti in titanium oxide.
　以上のようにして得られた粉砕混合粉５００ｇをルツボに充填し、電気炉にて１５００℃で４時間焼成した。 500 g of the pulverized mixed powder obtained as described above was charged in a crucible and baked at 1500 ° C. for 4 hours in an electric furnace.
　得られた生成物のＸ線回折チャートを図６に示す。図６に示すように、得られた生成物は、Ａｌ２ＴｉＯ５であった。図６の下方に示すピークは、それぞれＪＣＰＤＳのＡｌ２ＴｉＯ５及びＡｌ２Ｏ３のピークである。 An X-ray diffraction chart of the obtained product is shown in FIG. As shown in FIG. 6, the product obtained was Al 2 TiO 5 . The peaks shown in the lower part of FIG. 6 are those of JCPDS Al 2 TiO 5 and Al 2 O 3 , respectively.
　フロー式粒子像分析により、得られた生成物の個数平均長軸径及び個数平均短軸径を測定し、アスペクト比（＝個数平均長軸径／個数平均短軸径）を算出した。測定結果を表１に示す。 The number average major axis diameter and the number average minor axis diameter of the obtained product were measured by flow type particle image analysis, and the aspect ratio (= number average major axis diameter / number average minor axis diameter) was calculated. The measurement results are shown in Table 1.
　（比較例２）
　酸化チタン２５２．５ｇ、酸化アルミニウム４７７．４ｇ、水酸化マグネシウム１３．７ｇ及び酸化ケイ素５６．４ｇを振動ミルにて粉砕しながら、２．０時間混合した。 (Comparative Example 2)
252.5 g of titanium oxide, 477.4 g of aluminum oxide, 13.7 g of magnesium hydroxide and 56.4 g of silicon oxide were mixed for 2.0 hours while being pulverized with a vibration mill.
　酸化アルミニウムは、酸化チタン中のＴｉ１モルに対し、酸化アルミニウム中のＡｌが２モルより過剰量となるように混合されている。ここでは、チタン酸アルミ１００重量部に対し、酸化アルミニウムとして約３５重量％過剰となるようにアルミニウムが酸化チタンに混合されている。 Aluminum oxide is mixed so that the amount of Al in the aluminum oxide is more than 2 mol relative to 1 mol of Ti in the titanium oxide. Here, aluminum is mixed with titanium oxide so as to be about 35% by weight as aluminum oxide with respect to 100 parts by weight of aluminum titanate.
　以上のようにして得られた粉砕混合粉５００ｇをルツボに充填し、電気炉にて１５００℃で４時間焼成した。 500 g of the pulverized mixed powder obtained as described above was charged in a crucible and baked in an electric furnace at 1500 ° C. for 4 hours.
　得られた生成物のＸ線回折チャートを図７に示す。図７に示すように、得られた生成物は、Ａｌ２ＴｉＯ５とＡｌ６Ｓｉ２Ｏ１３とＡｌ２Ｏ３であった。図７の下方に示すピークは、それぞれＪＣＰＤＳのＡｌ２ＴｉＯ５、Ａｌ６Ｓｉ２Ｏ１３及びＡｌ２Ｏ３のピークである。 An X-ray diffraction chart of the obtained product is shown in FIG. As shown in FIG. 7, the obtained products were Al 2 TiO 5 , Al 6 Si 2 O 13, and Al 2 O 3 . The peaks shown in the lower part of FIG. 7 are the peaks of Al 2 TiO 5 , Al 6 Si 2 O 13 and Al 2 O 3 of JCPDS, respectively.
　得られた生成物中に含まれるＡｌ６Ｓｉ２Ｏ１３及びＡｌ２Ｏ３の含有量を、内部標準の定量により求めた。Ａｌ６Ｓｉ２Ｏ１３の含有量は、Ａｌ２ＴｉＯ５に対し２８．６重量％であり、Ａｌ２Ｏ３の含有量は、Ａｌ２ＴｉＯ５に対し５．５重量％であった。 The contents of Al 6 Si 2 O 13 and Al 2 O 3 contained in the obtained product were determined by quantification of an internal standard. The content of Al 6 Si 2 O 13 was 28.6 wt% with respect to Al 2 TiO 5 , and the content of Al 2 O 3 was 5.5 wt% with respect to Al 2 TiO 5 .
　フロー式粒子像分析により、得られた生成物の個数平均長軸径及び個数平均短軸径を測定し、アスペクト比（＝個数平均長軸径／個数平均短軸径）を算出した。測定結果を表１に示す。 The number average major axis diameter and the number average minor axis diameter of the obtained product were measured by flow type particle image analysis, and the aspect ratio (= number average major axis diameter / number average minor axis diameter) was calculated. The measurement results are shown in Table 1.
　（比較例３）
　実施例１で得られた柱状チタン酸アルミニウムを自動乳鉢にて５０時間粉砕処理し、粒状のチタン酸アルミニウムを得た。 (Comparative Example 3)
The columnar aluminum titanate obtained in Example 1 was ground in an automatic mortar for 50 hours to obtain granular aluminum titanate.
　得られた生成物について、フロー式粒子像分析にて、個数平均長軸径、個数平均短軸径を測定し、アスペクト比を算出した。測定結果を表１に示す。 For the obtained product, the number average major axis diameter and the number average minor axis diameter were measured by flow particle image analysis, and the aspect ratio was calculated. The measurement results are shown in Table 1.
　〔走査型電子顕微鏡（ＳＥＭ）による観察〕
　実施例２で得られたチタン酸アルミニウムについて、走査型電子顕微鏡で観察した。図１は、このチタン酸アルミニウムを示す走査型電子顕微鏡写真（倍率１０００倍）である。図１から明らかなように、柱状のチタン酸アルミニウムが得られている。 [Observation with a scanning electron microscope (SEM)]
The aluminum titanate obtained in Example 2 was observed with a scanning electron microscope. FIG. 1 is a scanning electron micrograph (magnification 1000 times) showing this aluminum titanate. As is apparent from FIG. 1, columnar aluminum titanate is obtained.
　図２は、上記のチタン酸アルミニウムを拡大して示す走査型電子顕微鏡（倍率７０００倍）である。図２に示すように、チタン酸アルミニウムの表面に、ムライト及び酸化アルミニウムが付着している。 FIG. 2 is a scanning electron microscope (magnification: 7000 times) showing the above-mentioned aluminum titanate in an enlarged manner. As shown in FIG. 2, mullite and aluminum oxide are attached to the surface of the aluminum titanate.
　〔ハニカム焼結体の製造〕
　上記各実施例及び各比較例で得られたチタン酸アルミニウムを用いて、以下のようにしてハニカム焼結体を製造した。 [Manufacture of honeycomb sintered body]
Using the aluminum titanate obtained in each of the above Examples and Comparative Examples, a honeycomb sintered body was manufactured as follows.
　チタン酸アルミニウム１００重量部に対し、黒鉛２０重量部、メチルセルロース１０重量部、脂肪酸石鹸０．５重量部を配合し、さらに水を適当量添加して混練し、押出成形可能な坏土を得た。 Compounding 20 parts by weight of graphite, 10 parts by weight of methyl cellulose and 0.5 parts by weight of fatty acid soap with respect to 100 parts by weight of aluminum titanate, adding an appropriate amount of water and kneading to obtain an extrudable clay. .
　得られた坏土を押出成形機にてハニカム構造体となるように押し出して成形し、次に熱風乾燥機で乾燥した後、得られた成形体を１５００℃で焼成し、ハニカム焼結体を得た。 The obtained kneaded material was extruded to form a honeycomb structure with an extrusion molding machine, and then dried with a hot air dryer, and then the resulting molded body was fired at 1500 ° C. to obtain a honeycomb sintered body. Obtained.
　〔ハニカム焼結体の評価〕
　得られた各ハニカム焼結体について気孔率、曲げ強度、熱膨張係数、及び結晶配向比を以下のようにして測定した。 [Evaluation of honeycomb sintered body]
For each of the obtained honeycomb sintered bodies, the porosity, bending strength, thermal expansion coefficient, and crystal orientation ratio were measured as follows.
　（気孔率）
　図８は、ハニカム焼結体（ハニカム構造体）を示す斜視図である。図８に示すように、ハニカム焼結体１は、８×８セルを有し、端面１ａは、縦１．８ｃｍ、横１．８ｃｍの大きさを有している。矢印Ａは、押出方向を示しており、矢印Ｂは押出方向Ａに対し垂直な方向を示している。 (Porosity)
FIG. 8 is a perspective view showing a honeycomb sintered body (honeycomb structure). As shown in FIG. 8, the honeycomb sintered body 1 has 8 × 8 cells, and the end face 1a has a size of 1.8 cm in length and 1.8 cm in width. An arrow A indicates the extrusion direction, and an arrow B indicates a direction perpendicular to the extrusion direction A.
　気孔率は、上記の８×８セルのハニカム焼結体１の中心部２から、２×２セルに相当する部分を、押出方向Ａに沿う長さが２ｃｍ程度となるように切り出し、測定サンプルとした。 The porosity was measured by cutting a portion corresponding to 2 × 2 cells from the center portion 2 of the above 8 × 8 cell honeycomb sintered body 1 so that the length along the extrusion direction A was about 2 cm. It was.
　図９は、測定サンプル３を示す斜視図である。図９に示す測定サンプル３を用い、ＪＩＳ　Ｒ１６３４に準拠して気孔率を測定した。 FIG. 9 is a perspective view showing the measurement sample 3. Using the measurement sample 3 shown in FIG. 9, the porosity was measured in accordance with JIS R1634.
　（曲げ強度）
　図１０に示すように、上記の８×８セルのハニカム焼結体１を、支持点１１及び１２に支持した状態で、焼結体１の中心部を押圧棒１０で押圧することにより、ＪＩＳ　Ｒ１６０１に準拠して、曲げ強度を測定した。 (Bending strength)
As shown in FIG. 10, the 8 × 8 cell honeycomb sintered body 1 is supported by the support points 11 and 12, and the center portion of the sintered body 1 is pressed with a pressing rod 10, thereby JIS. The bending strength was measured according to R1601.
　（熱膨張係数）
　図８及び図９を参照して説明した、気孔率の測定サンプル３と同様にして、８×８セルのハニカム焼結体１の中心部２から、押出方向Ａに沿う長さが２ｃｍ程度となるように切り出し、測定サンプル３とした。図１１に示すように、測定サンプル３の押出方向Ａにおける線膨張係数を、ＪＩＳ　Ｒ１６１８に準拠して測定した。 (Coefficient of thermal expansion)
Similarly to the porosity measurement sample 3 described with reference to FIGS. 8 and 9, the length along the extrusion direction A from the central portion 2 of the 8 × 8 cell honeycomb sintered body 1 is about 2 cm. It cut out so that it might become, and it was set as the measurement sample 3. As shown in FIG. 11, the linear expansion coefficient in the extrusion direction A of the measurement sample 3 was measured according to JIS R1618.
　（結晶配向比）
　得られたハニカム焼結体についてのＣ軸結晶配向比を、結晶配向比とした測定した。 (Crystal orientation ratio)
The C-axis crystal orientation ratio of the obtained honeycomb sintered body was measured as the crystal orientation ratio.
　結晶配向比は、以下の式に示すように、押出方向の結晶配向度と、押出方向と垂直な方向の結晶配向度（垂直方向の結晶配向度）から算出した。 The crystal orientation ratio was calculated from the crystal orientation degree in the extrusion direction and the crystal orientation degree in the direction perpendicular to the extrusion direction (vertical crystal orientation degree) as shown in the following formula.
　結晶配向比＝押出方向の結晶配向度／（押出方向の結晶配向度＋垂直方向の結晶配向度） Crystal orientation ratio = Crystal orientation in extrusion direction / (Crystal orientation in extrusion direction + Crystal orientation in vertical direction)
　結晶配向度は、Ｘ線回折により求めた。押出方向の結晶配向度は、ハニカム焼結体の押出面のＸ線回折を測定し、（００２）面の回折強度（＝Ｉ（００２））及び（２３０）面の回折強度（＝Ｉ（２３０））より、以下の式により算出した。 The degree of crystal orientation was determined by X-ray diffraction. The degree of crystal orientation in the extrusion direction is determined by measuring the X-ray diffraction of the extruded surface of the honeycomb sintered body, and the diffraction intensity of the (002) plane (= I (002)) and the diffraction intensity of the (230) plane (= I (230) )), The following formula was used.
　結晶配向度＝Ｉ（００２）／｛Ｉ（００２）＋Ｉ（２３０）｝ Crystal orientation degree = I (002) / {I (002) + I (230)}
　垂直方向の結晶配向度は、ハニカム焼結体の垂直面のＸ線回折を測定し、上記と同様にして、Ｉ（００２）及びＩ（２３０）を求めることにより算出した。 The crystal orientation degree in the vertical direction was calculated by measuring X-ray diffraction of the vertical surface of the honeycomb sintered body and obtaining I (002) and I (230) in the same manner as described above.
　なお、（００２）面の回折強度は、２θ＝５０．８°付近に現れるピークであり、（２３０）面の回折ピークは、２θ＝３３．７°付近に現れるピークである。 The diffraction intensity of the (002) plane is a peak appearing near 2θ = 50.8 °, and the diffraction peak of the (230) plane is a peak appearing near 2θ = 33.7 °.
　図１２及び図１３は、押出面のＸ線回折を測定するための測定サンプルの作製を示す斜視図である。 12 and 13 are perspective views showing the production of a measurement sample for measuring the X-ray diffraction of the extruded surface.
　図１２に示すように、ハニカム焼結体１の端面１ａを含む領域４を切り取り、図１３に示す測定サンプルを作製した。図１３に示す測定サンプル５を用い、この測定サンプル５の押出面５ａのＸ線回折を測定した。 As shown in FIG. 12, the region 4 including the end face 1a of the honeycomb sintered body 1 was cut out to produce a measurement sample shown in FIG. Using the measurement sample 5 shown in FIG. 13, the X-ray diffraction of the extruded surface 5a of the measurement sample 5 was measured.
　図１４及び図１５は、垂直面、すなわち、押出面に垂直な方向の面のＸ線回折を測定するためのサンプルの作製を示す斜視図である。 14 and 15 are perspective views showing the production of a sample for measuring X-ray diffraction on a vertical plane, that is, a plane perpendicular to the extrusion plane.
　図１４に示すように、ハニカム焼結体１の８×２セルに相当する領域６を、押出方向Ａに沿って切り出し、図１５に示す測定サンプル７を得た。この測定サンプル７の押出方向Ａに沿う面（押出面）７ａのＸ線回折の測定を行った。 As shown in FIG. 14, a region 6 corresponding to 8 × 2 cells of the honeycomb sintered body 1 was cut out along the extrusion direction A to obtain a measurement sample 7 shown in FIG. The measurement of the X-ray diffraction of the surface (extruded surface) 7a along the extrusion direction A of the measurement sample 7 was performed.
　以上のようにして、各ハニカム焼結体についての結晶配向比を算出し、結果を表１に示した。 The crystal orientation ratio for each honeycomb sintered body was calculated as described above, and the results are shown in Table 1.
　なお、（００２）面はＣ軸に垂直な面であり、（００２）面の強度が高いということは、Ｃ軸が配向していることを意味する。 Note that the (002) plane is a plane perpendicular to the C axis, and the high strength of the (002) plane means that the C axis is oriented.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１に示すように、本発明に従う実施例１～３の柱状チタン酸アルミニウムを用いたハニカム焼結体は、比較例１の柱状チタン酸アルミニウムを用いたハニカム焼結体に比べ、高い曲げ強度を有している。これは、本発明に従う柱状チタン酸アルミニウムが、ムライト微粒子及び酸化アルミニウム微粒子を表面に付着させており、表面に存在するムライト微粒子及び酸化アルミニウムが焼結助剤として働き、機械的強度に優れたハニカム焼結体が得られるためであると考えられる。 As shown in Table 1, the honeycomb sintered body using the columnar aluminum titanate of Examples 1 to 3 according to the present invention has higher bending strength than the honeycomb sintered body using the columnar aluminum titanate of Comparative Example 1. have. This is because the columnar aluminum titanate according to the present invention has mullite fine particles and aluminum oxide fine particles attached to the surface, and the mullite fine particles and aluminum oxide present on the surface act as a sintering aid and have excellent mechanical strength. This is considered to be because a sintered body is obtained.
　また、実施例１～３の焼結体は、比較例３の焼結体に比べ、低い線膨張係数を有している。比較例３の結晶配向比が実施例１～３に比べ低いことから、比較例３のアスペクト比が小さいため、ハニカム焼結体の押出方向にチタン酸アルミニウムのＣ軸方向が整列せず、低い線膨張係数が得られていないものと考えられる。これに対し、実施例１～３の柱状チタン酸アルミニウムは、アスペクト比が大きいため、ハニカム焼結体の押出方向にチタン酸アルミニウムのＣ軸方向が整列し、低い線膨張係数が得られているものと考えられる。 In addition, the sintered bodies of Examples 1 to 3 have a lower linear expansion coefficient than the sintered body of Comparative Example 3. Since the crystal orientation ratio of Comparative Example 3 is lower than that of Examples 1 to 3, since the aspect ratio of Comparative Example 3 is small, the C-axis direction of aluminum titanate is not aligned with the extrusion direction of the honeycomb sintered body and is low. It is considered that the linear expansion coefficient was not obtained. In contrast, since the columnar aluminum titanates of Examples 1 to 3 have a large aspect ratio, the C-axis direction of aluminum titanate is aligned with the extrusion direction of the honeycomb sintered body, and a low linear expansion coefficient is obtained. It is considered a thing.
　また、比較例２においては、ムライトが２５重量％より多く含有されているため、線膨張係数が高くなっている。また、ムライトの付着量が多いため、粉体のアスペクト比も小さくなっており、このため、押出方向にチタン酸アルミニウムが配向しにくくなっており、このことからも線膨張係数が高くなっているものと思われる。 Further, in Comparative Example 2, since the mullite content is more than 25% by weight, the linear expansion coefficient is high. In addition, since the amount of mullite adhering is large, the aspect ratio of the powder is also small, which makes it difficult for aluminum titanate to be oriented in the extrusion direction, which also increases the linear expansion coefficient. It seems to be.
　１…ハニカム焼結体（ハニカム構造体）
　１ａ…ハニカム構造体の端面
　２…ハニカム構造体の中心部
　３…ハニカム構造体から切り出した測定サンプル
　４…ハニカム構造体の端面近傍の領域
　５…ハニカム構造体の押出面をＸ線回折測定するためのサンプル
　５ａ…押出面
　６…ハニカム構造体の８×２セルの領域
　７…ハニカム構造体の垂直面をＸ線回折測定するためのサンプル
　７ａ…垂直面 1 ... Honeycomb sintered body (honeycomb structure)
DESCRIPTION OF SYMBOLS 1a ... End face of honeycomb structure 2 ... Center part of honeycomb structure 3 ... Measurement sample cut out from honeycomb structure 4 ... Area near end face of honeycomb structure 5 ... X-ray diffraction measurement of extruded surface of honeycomb structure Sample 5a ... extruded surface 6 ... 8 × 2 cell region of honeycomb structure 7 ... Sample 7a ... vertical surface for X-ray diffraction measurement of vertical surface of honeycomb structure

Claims (4)

  1. 　平均アスペクト比（＝個数平均長軸径／個数平均短軸径）が１．３以上の柱状チタン酸アルミニウムであって、柱状チタン酸アルミニウムに対し、５～２５重量％のムライト及び２～１０重量％の酸化アルミニウムが表面に付着していることを特徴とする柱状チタン酸アルミニウム。 Columnar aluminum titanate having an average aspect ratio (= number average major axis diameter / number average minor axis diameter) of 1.3 or more, and 5 to 25 wt% mullite and 2 to 10 wt% with respect to the columnar aluminum titanate. % Columnar aluminum titanate, characterized in that the aluminum oxide adheres to the surface.
  2. 　個数平均短軸径が、１０μｍ以下であることを特徴とする請求項１に記載の柱状チタン酸アルミニウム。 2. The columnar aluminum titanate according to claim 1, wherein the number average minor axis diameter is 10 μm or less.
  3. 　請求項１または２に記載の柱状チタン酸アルミニウムを製造する方法であって、
    　チタン源、アルミニウム源、ケイ素源、及びマグネシウム源を含む原料をメカノケミカルに粉砕しながら混合する工程と、
    　粉砕した混合物を焼成する工程とを備えることを特徴とする柱状チタン酸アルミニウムの製造方法。     A method for producing the columnar aluminum titanate according to claim 1 or 2,
    Mixing a raw material containing a titanium source, an aluminum source, a silicon source, and a magnesium source while pulverizing them into mechanochemicals;
    And a step of firing the pulverized mixture. A method for producing columnar aluminum titanate, comprising:
  4. 　請求項１または２に記載の柱状チタン酸アルミニウムを用いて作製したハニカム構造体であって、
    　ハニカム構造体の押出方向の３０～８００℃の間の熱膨張係数が１．０×１０－６／℃以下であり、ハニカム押出方向に対するＣ軸の結晶配向比が０．７５以上であることを特徴とするハニカム構造体。     A honeycomb structure manufactured using the columnar aluminum titanate according to claim 1 or 2,
    The thermal expansion coefficient between 30 and 800 ° C. in the extrusion direction of the honeycomb structure is 1.0 × 10 −6 / ° C. or less, and the C-axis crystal orientation ratio with respect to the honeycomb extrusion direction is 0.75 or more. A featured honeycomb structure.
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