Melted magnesium aluminate grain rich in magnesium

Patent metadata

Field	Value
Publication number	US-10494308-B2
Application number	US-201615759679-A
Country	US
Kind code	B2
Filing date	Sep 14, 2016
Priority date	Sep 14, 2015
Publication date	Dec 3, 2019
Grant date	Dec 3, 2019

Abstract

A fused grain is essentially composed of a matrix of a magnesium aluminum oxide of MgAl2O4 spinel structure and/or of the MgO—MgAl2O4 eutectic structure, and of inclusions essentially composed of magnesium oxide. The grain has the following overall chemical composition, as percentages by weight, expressed in the form of oxides: more than 5.0% and less than 19.9% of Al2O3, Al2O3 and MgO together represent more than 95.0% of the weight of the grain. The cumulative content of CaO and of ZrO2 is less than 4000 ppm, by weight.

First claim

The invention claimed is:

1. A fused grain essentially composed of a matrix of a magnesium aluminum oxide of MgAl 2 O 4 spinel structure and/or of the MgO—MgAl 2 O 4 eutectic structure, and of inclusions essentially composed of magnesium oxide, said grain having the following overall chemical composition, as percentages by weight, expressed in the form of oxides:
more than 5.0% and less than 19.9% of Al 2 O 3 ,
Al 2 O 3 and MgO together represent more than 95.0% of the weight of said grain,
wherein a cumulative content of CaO and of ZrO 2 is less than 4000 ppm, by weight, and
wherein the matrix is composed of separate regions of spinel structure and of the MgO—MgAl 2 O 4 eutectic structure.

2. The fused grain as claimed in claim 1 , wherein Al 2 O 3 represents more than 8.0% by weight.

3. The fused grain as claimed in claim 1 , wherein the cumulative content of CaO and ZrO 2 is less than 3000 ppm.

4. The fused grain as claimed in claim 1 , wherein the cumulative content of CaO and ZrO 2 is less than 2500 ppm.

5. The fused grain as claimed in claim 1 , wherein the grain does not comprise an alumina Al 2 O 3 phase.

6. The fused grain as claimed in claim 1 , wherein impurities are present in the grain and include one or more of CaO, ZrO 2 , Fe 2 O 3 , SiO 2 , Na 2 O, and MnO 2 .

7. The fused grain as claimed in claim 1 , comprising less than 2000 ppm of CaO.

8. The fused grain as claimed in claim 1 , comprising less than 200 ppm of ZrO 2 .

9. The fused grain as claimed in claim 1 , wherein Al 2 O 3 and MgO together represent more than 99.0% of the weight of said grain.

10. A mixture of fused grains as claimed in claim 1 .

11. A ceramic material obtained by sintering fused grains as claimed in claim 1 .

12. The ceramic material as claimed claim 11 , comprising inclusions that are each essentially composed of calcium oxide or zirconium oxides or both calcium oxide and zirconium oxide, the number of which is less than 100 per 10 000 square micrometers, on an electron microscopy photograph.

13. A process for manufacturing grains as claimed in claim 1 , comprising:
a) mixing starting materials in order to form a starting feedstock,
b) melting the starting feedstock until a molten liquid is obtained,
c) cooling said molten liquid so that the molten liquid is completely solidified to form a solid mass,
d) grinding said solid mass so as to obtain a mixture of said fused grains.

14. A fused grain essentially composed of a matrix of a magnesium aluminum oxide of MgAl 2 O 4 spinel structure and/or of the MgO—MgAl 2 O 4 eutectic structure, and of inclusions essentially composed of magnesium oxide, said grain having the following overall chemical composition, as percentages by weight, expressed in the form of oxides:
more than 5.0% and less than 19.9% of Al 2 O 3 ,
Al 2 O 3 and MgO together represent more than 95.0% of the weight of said grain,
wherein a cumulative content of CaO and of ZrO 2 is less than 4000 ppm, by weight, and wherein fine inclusions are present in the grain, each of said fine inclusions being essentially composed of calcium oxide and or zirconium oxide or both calcium oxide and zirconium oxide, a largest dimension of the fine inclusions being less than 2 micrometers.

15. The fused grain as claimed in claim 14 , wherein the largest dimension of the fine inclusions fused grain is less than 1 micrometer.

Assignees

• Saint Gobain Ct Recherches
• Saint Gobain Centre De Rech Et Detudes European

Inventors

• Raffy Stéphane

Classifications

• C04B2235/3208

  Calcium oxide or oxide-forming salts thereof, e.g. lime · CPC title

• C04B2235/3244

  Zirconium oxides, zirconates, hafnium oxides, hafnates, or oxide-forming salts thereof · CPC title

• C04B35/6262

  of calcined, sintered clinker or ceramics · CPC title

• C04B2235/5436

  micrometer sized, i.e. from 1 to 100 micron · CPC title

• C04B35/443 Primary

  Magnesium aluminate spinel · CPC title