Magnesium Aluminum Titanate Crystal Structure and Method for Producing Same

• US 20070224110A1
• Filed: 04/28/2005
• Published: 09/27/2007
• Est. Priority Date: 04/28/2004
• Status: Active Grant

• Current Assignee: OHCERA Co. Ltd.
• Original Assignee: OHCERA Co. Ltd.
• Inventors: Fukuda, Masahiro, Takahashi, Masahide, Yoko, Toshinobu, Fukuda, Tsutomu, Fukuda, Masaaki
• Granted Patent: US 8,557,216 B2
• Time in Patent Office: Days
• US Class Current: 423/598
• CPC Class Codes: C04B 2235/3206 Magnesium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3418 Silicon oxide, silicic acids, or oxide forming salts thereof, e.g. silica sol, fused silica, silica fume, cristobalite, quartz or flint glass constituents C04B2235/36
• CPC Class Codes: C04B 2235/3463 Alumino-silicates other than clay, e.g. mullite
• CPC Class Codes: C04B 2235/3472 Alkali metal alumino-silicates other than clay, e.g. spodumene, alkali feldspars such as albite or orthoclase, micas such as muscovite, zeolites such as natrolite
• CPC Class Codes: C04B 2235/3481 Alkaline earth metal alumino-silicates other than clay, e.g. cordierite, beryl, micas such as margarite, plagioclase feldspars such as anorthite, zeolites such as chabazite
• CPC Class Codes: C04B 2235/349 Clays, e.g. bentonites, smectites such as montmorillonite, vermiculites or kaolines, e.g. illite, talc or sepiolite
• CPC Class Codes: C04B 2235/6562 Heating rate
• CPC Class Codes: C04B 2235/77 Density
• CPC Class Codes: C04B 2235/96 Properties of ceramic products, e.g. mechanical properties such as strength, toughness, wear resistance
• CPC Class Codes: C04B 2235/9607 Thermal properties, e.g. thermal expansion coefficient
• CPC Class Codes: C04B 35/465 based on alkaline earth metal titanates
• CPC Class Codes: C04B 35/478 based on aluminium titanates

Abstract

To provide an aluminum magnesium titanate crystal structure which can be used stably in variable high temperatures, because of its excellent heat resistance, thermal shock resistance, high thermal decomposition resistance and high mechanical property, and a process for its production.

An aluminum magnesium titanate crystal structure, which is a solid solution wherein at least some of Al atoms in the surface layer of aluminum magnesium titanate crystal represented by the empirical formula Mg_xAl_2(1−x)Ti_(1+x)O₅ (wherein 0.1≦x<1) are substituted with Si atoms, and which has a thermal expansion coefficient of from −6×10⁻⁶ (1/K) to 6×10⁻⁶ (1/K) in a range of from 50 is to 800° C. at a temperature raising rate of 20° C./min, and a remaining ratio of aluminum magnesium titanate of at least 50%, when held in an atmosphere of 1,100° C. for 300 hours.

Claims

1. An aluminum magnesium titanate crystal structure, which is a solid solution wherein at least some of Al atoms in the surface layer of aluminum magnesium titanate crystal represented by the empirical formula Mg_xAl₂₍₁₋

x)Ti_(1+x)O₅, wherein 0.1≦

x<

1, are substituted with Si atoms, and which has a thermal expansion coefficient of from −

6×

10<sup>−

6</sup> (1/K) to 6×

10<sup>−

6</sup> (1/K) in a range of from 50 to 800°

C. at a temperature raising rate of 20°

C./min, and a remaining ratio of aluminum magnesium titanate of at least 50%, when held in an atmosphere of 1,100°

C. for 300 hours.

2. The aluminum magnesium titanate crystal structure as defined in claim 1, which is a solid solution wherein 0.1 to 1 mol % of Al atoms are substituted with Si atoms.

3. The aluminum magnesium titanate crystal structure according to claim 1, which has a three-point bending strength of at least 25 MPa in accordance with JIS R1601.

4. A process for producing the aluminum magnesium titanate crystal structure as defined in claim 1, which comprises firing at a temperature of from 1,200 to 1,700°

C., a raw material mixture having 1 to 10 parts by mass of a silicon-containing compound having a melting point of from 700 to 1,500°

C., mixed to 100 parts by mass of a mixture comprising a Mg-containing compound, Al-containing compound and Ti-containing compound in the same ratio as the metal component ratio of Mg, Al and Ti in aluminum magnesium titanate represented by the empirical formula Mg_xAl<sub>2(1−

x)</sub>Ti_(1+x)O₅, wherein 0.1≦

x<

1, as calculated as the respective oxides.

5. The process according to claim 4, wherein aluminum magnesium titanate crystal is formed in a liquid phase of the silicon-containing compound.

6. The process according to claim 4, wherein molding assistants are added to the raw material mixture, followed by firing a molded product.

7. The process according to claim 4, wherein the raw material mixture is subjected to prefiring within a temperature range of from 700 to 1,000°

C., followed by firing.

8. The process according to claim 4, wherein the silicon-containing compound is an aluminosilicate.

9. The process according to claim 8, wherein the aluminosilicate is at least one mineral selected from the group of minerals consisting of plagiocrase, feldspathoid, mica clay mineral, zeolite and cordierite.

10. The aluminum magnesium titanate crystal structure according to claim 2, which has a three-point bending strength of at least 25 MPa in accordance with JIS R1601.

11. The process according to claim 5, wherein molding assistants are added to the raw material mixture, followed by firing a molded product.

12. The process according to claim 6, wherein the raw material mixture is subjected to prefiring within a temperature range of from 700 to 1,000°

C., followed by firing.

13. The process according to claim 5, wherein the silicon-containing compound is an aluminosilicate.

14. The process according to claim 6, wherein the silicon-containing compound is an aluminosilicate.

15. The process according to claim 7, wherein the silicon-containing compound is an aluminosilicate.

16. The process according to claim 11, wherein the silicon-containing compound is an aluminosilicate.

17. The process according to claim 12, wherein the silicon-containing compound is an aluminosilicate.

18. The process according to claim 13, wherein the aluminosilicate is at least one mineral selected from the group of minerals consisting of plagiocrase, feldspathoid, mica clay mineral, zeolite and cordierite.

19. The process according to claim 14 wherein the aluminosilicate is at least one mineral selected from the group of minerals consisting of plagiocrase, feldspathoid, mica clay mineral, zeolite and cordierite.

20. The process according to claim 15, wherein the aluminosilicate is at least one mineral selected from the group of minerals consisting of plagiocrase, feldspathoid, mica clay mineral, zeolite and cordierite.

21. The process according to claim 16, wherein the aluminosilicate is at least one mineral selected from the group of minerals consisting of plagiocrase, feldspathoid, mica clay mineral, zeolite and cordierite.

22. The process according to claim 17, wherein the aluminosilicate is at least one mineral selected from the group of minerals consisting of plagiocrase, feldspathoid, mica clay mineral, zeolite and cordierite.