Refractory powder comprising coated mullite grains

Patent metadata

Field	Value
Publication number	US-9908816-B2
Application number	US-201514797901-A
Country	US
Kind code	B2
Filing date	Jul 13, 2015
Priority date	Apr 28, 2010
Publication date	Mar 6, 2018
Grant date	Mar 6, 2018

Abstract

A powder is disclosed having a coarse fraction representing more than 60% and less than 85% of the powder, as a weight percentage on the basis of the oxides, and that is constituted of particles having a size greater than or equal to 50 μm, referred to as “coarse particles”, the powder comprising at least 5% of coated grains having a size greater than or equal to 50 μm, as a weight percentage on the basis of the oxides of the powder, and a fine fraction, forming the balance to 100% as a weight percentage on the basis of the oxides, constituted of particles having a size of less than 50 μm, referred to as “matrix particles”. The powder can be applied in combustion chambers in which the temperature may reach 1400° C.

First claim

The invention claimed is:

1. A powder comprising:
a coarse fraction representing more than 60% and less than 85% of the powder, as percentage by weight based on the oxides, and consisting of particles exhibiting a size of greater than or equal to 50 μm, referred to as “coarse particles”, the powder comprising at least 5% of coated grains exhibiting a size of greater than or equal to 50 μm, as percentage by weight based on the oxides of the powder, and
a fine fraction, forming the remainder to 100% as percentage by weight based on the oxides, consisting of particles exhibiting a size of less than 50 μm, referred to as “matrix particles”,
said coated grains each comprising:
a base grain comprising more than 30% by weight of mullite;
a coating extending over more than 50% of the surface of said base grain and consisting, for more than 90% of its weight, of a coating material chosen from:
alumina;
CaSiO 3 ;
lanthanide, Ta, Ti, Sc, Y, Mg , Mo aluminates and their mixtures;
lanthanide, Sc, Y, Zr , Hf silicates and their mixtures;
oxides of one or more elements chosen from Ti, Sc, Y, Yb, Mg, Ce, Mo, Zr and Hf;
lanthanide and/or Y and/or Sc phosphates;
and their mixtures,

the powder comprising more than 20% of particles exhibiting a size greater than 150 μm, as percentage by weight based on the oxides of the powder,
the powder exhibiting a content of alumina of greater than 70%, as percentage by weight based on the oxides.

2. The powder as claimed in claim 1 , in which said coating extends over more than 70% of the surface of said base grain.

3. The powder as claimed in claim 2 , in which said coating extends over more than 90% of the surface of said base grain.

4. The powder as claimed in claim 1 , in which the surface porosity of the coating is less than 25%.

5. The powder as claimed in claim 4 , in which the surface porosity of the coating is less than 3%.

6. The powder as claimed in claim 1 , in which the base grain comprises more than 50% of mullite, as a percentage by weight based on the oxides.

7. The powder as claimed in claim 6 , in which the base grain comprises more than 80% of mullite, as a percentage by weight based on the oxides.

8. The powder as claimed in claim 1 , in which the coating is composed of:
an external layer made of said coating material, and
a transition layer which extends between the base grain and said external layer and which comprises:
silica and/or alumina,
and at least one of the constituents of the coating material.

9. The powder as claimed in claim 1 , in which the coating material is chosen from:
Al 2 O 3 ;
GdAlO 3 , Gd 4 Al 2 O 9 , Gd 3 Al 5 O 12 , AlTaO 4 , Al 2 TiO 5 , Y 3 Al 5 O 12 , YAlO 3 , Y 4 Al 2 O 9 , Yb 4 Al 2 O 9 , YbAlO 3 , Yb 3 Al 5 O 12 , MgAl 2 O 4 and their mixtures;
Gd 2 SiO 5 , Gd 2 Si 2 O 7 , Sc 2 Si 2 O 7 , Sc 2 SiO 5 , Y 2 Si 2 O 7 , Y 2 SiO 5 , Yb 2 Si 2 O 7 , Yb 2 SiO 5 , ZrSiO 4 , HfSiO 4 , (Zr,Hf)SiO 4 , CaSiO 3 ;
ZrO 2 , HfO 2 , HfTiO 4 , ScTaO 4 , Sc 4 Hf 3 O 12 , Sc 4 Zr 3 O 12 , a partially stabilized and/or stabilized zirconia, a partially stabilized and/or stabilized hafnone, and their mixtures;
LaPO 4 , YPO 4 and their mixtures;
and their mixtures.

10. The powder as claimed in claim 9 , in which the coating material is alumina.

11. The powder as claimed in claim 1 , containing more than 40% of said coated grains with a size of greater than or equal to 50 μm, as a percentage by weight based on the oxides of the powder.

12. The powder as claimed in claim 11 , in which the coarse fraction comprises, for more than 95% of its weight, particles composed, for more than 95% of their weight, of alumina and/or zirconia and/or magnesia and/or silica, and said coated grains, and in which the fine fraction consists of particles composed of alumina and/or zirconia and/or magnesia and/or silica.

13. The powder as claimed in claim 1 , in which the fine fraction comprises less than 90% of silica, as percentage by weight based on the oxides of the fine fraction.

14. The powder as claimed in claim 1 , exhibiting a content of alumina Al 2 O 3 of greater than 60% and a content of silica SiO 2 of less than 30%, as percentage by weight based on the oxides.

15. The powder as claimed in claim 1 , exhibiting a content of alumina Al 2 O 3 of greater than 85% and a content of silica SiO 2 of less than 10%, as percentage by weight based on the oxides.

16. The powder as claimed in claim 1 , in which the thickness of the coating is less than 300 μm.

17. The powder of claim 1 exhibiting a content of greater than 80%, as percentage by weight based on the oxides.

18. The powder of claim 1 , wherein the coarse fraction comprises particles composed, for more than 95% of their weight, of alumina and/or magnesia and/or silica.

19. The power of claim 1 , wherein the coarse fraction comprises, for more than 95% of its weight:
particles composed, for more than 95% of their weight, of alumina and/or magnesia and/or silica, or mixtures of such particles, and
coated grains having base grains made of mullite / zirconia and/or mullite.

20. The powder of claim 1 , wherein the fine fraction comprises particles composed of alumina and/or magnesia and/or silica.

21. The powder of claim 20 , wherein the fine fraction consists of particles composed of alumina and/or magnesia and/or silica.

22. The powder of claim 1 , wherein the coarse fraction comprises alumina coarse particles.

23. A device chosen from a combustion chamber of a gas turbine and a reformer, said device comprising a sintered refractory product manufactured from a powder as claimed in claim 1 , in particular in the form of a protective part.

24. A sintered product manufactured according to a process comprising the following successive stages:
A) preparation of a starting charge by addition of water to a powder comprising:
a coarse fraction representing more than 60% and less than 85% of the powder, as percentage by weight based on the oxides, and consisting of particles exhibiting a size of greater than or equal to 50 μm, referred to as “coarse particles”, the powder comprising at least 5% of coated grains exhibiting a size of greater than or equal to 50 μm, as percentage by weight based on the oxides of the powder, and
a fine fraction, forming the remainder to 100% as percentage by weight based on the oxides, consisting of particles exhibiting a size of less than 50 μm, referred to as “matrix particles”,
said coated grains each comprising:
a base grain comprising more than 30% by weight of mullite;
a coating extending over more than 50% of the surface of said base grain and consisting, for more than 90% of its weight, of a coating material chosen from:
alumina;
CaSiO 3 ;
lanthanide, Ta, Ti, Sc, Y, Mg , Mo aluminates and their mixtures;
lanthanide, Sc, Y, Zr , Hf silicates and their mixtures;
oxides of one or more elements chosen from Ti, Sc, Y, Yb, Mg, Ce, Mo, Zr and Hf;
lanthanide and/or Y and/or Sc phosphates;
and their mixtures,

B) shaping said starting charge so as to form a preform;
C) sintering said preform,
the product exhibiting the appearance of a block or of a layer, said block or layer having a thickness greater than 3 mm.

25. A method comprising:
subjecting a sintered refractory product manufactured from a powder as claimed in claim 1 to gases laden with water vapor exhibiting a temperature of greater than 1000° C.

Assignees

• Saint Gobain Ct Recherches

Inventors

• Champion Thibault
• His Christian

Classifications

• C04B2235/77

  Density · CPC title

• C04B2235/3217

  Aluminum oxide or oxide forming salts thereof, e.g. bauxite, alpha-alumina · CPC title

• C04B35/62813

  Alumina or aluminates · CPC title

• C04B35/185

  Mullite {3Al2O3-2SiO2} · CPC title

• C04B2235/9692

  Acid, alkali or halogen resistance · CPC title