JPH10245288A - Silicon carbide material with high emissivity antioxidant coat and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a surface emissivity without markedly deteriorating the antioxidative properties of a silicon carbide material by applying an composite oxide containing a lanthanoid-based rare earth element and chromium to the surface of a silicon carbide material coated with an oxide of the lanthanoid- based rate earth element or a complex oxide of the lanthanoid-based rate earth element and silicon. SOLUTION: This silicon carbide material coated with a coat containing high emissivity lanthanoid-based rate earth element oxide is obtained by applying complex oxide 3 containing the lanthanoid-based rare earth element (with the proviso that Y is included) and chromium to the surface of a silicon carbide material 11 coated with the oxide of the lanthanoid-based rate earth element (with the proviso that Y is included) or a complex oxide 2 of the lanthanoid- based rate earth element (with the proviso that Y is included) and silicon. The composition of the complex oxide of the rate earth element and the chromium is 40-50mol% oxide of the lanthanoid-based rare earth element and 35-60mol% chromium oxide, <=15mol% magnesium oxide and <=10mol% calcium oxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon carbide-coated lanthanoid-based rare earth element oxide-containing silicon carbide material which is advantageous as a structural material for space planes and next-generation supersonic passenger aircraft requiring a high heat radiation function by surface radiation at high temperatures. The present invention relates to a method for producing a silicon carbide material coated with a material and a lanthanoid-based rare earth element oxide-containing coating.

[0002]

2. Description of the Related Art A silicon carbide material whose surface is coated with a lanthanoid-based rare earth element oxide or a composite oxide of a lanthanoid-based rare earth element and silicon has been proposed with the aim of improving the oxidation resistance of the silicon carbide material. 6-1906
3). According to the proposal, in order to improve the adhesion between the coating and the substrate, which is important for forming the coating, the coating with a lanthanoid-based rare earth element oxide or a composite oxide of a lanthanoid-based rare earth element and silicon and a silicon carbide material A lanthanoid silicide, which is a reaction product of a lanthanoid-based rare earth element oxide and silicon carbide, or a reaction product of a silicon oxide and a lanthanoid-based rare earth element-silicon composite oxide. Proposed. However, the structural materials of space planes and next-generation supersonic passenger aircraft also require high thermal activity, that is, high emissivity in a high-temperature environment, in order to be used without cooling. The surface emissivity of a silicon carbide material coated with a lanthanoid-based rare earth element oxide film is, for example, about 0.5 at about 1700 ° C. with silicon carbide coated with yttrium silicate (Y ₂ SiO ₅ ). It is smaller than the emissivity of 0.7 to 0.9 which is considered to be close to ° C., and it is very difficult to use it under non-cooling conditions.

[0003]

SUMMARY OF THE INVENTION In view of the above-mentioned state of the art, the present invention does not significantly degrade the oxidation resistance of a silicon carbide material coated with a lanthanoid-based rare earth oxide coating.
An object of the present invention is to provide a silicon carbide material coated with a lanthanoid-based rare earth element oxide film having a high emissivity and a method for producing the same.

[0004]

The present invention provides the following constitutions (1) to
(5).

(1) The surface of a silicon carbide material coated with an oxide of a lanthanoid-based rare earth element (including yttrium) or a composite oxide of a lanthanoid-based rare earth element (including yttrium) and silicon, A high-emissivity lanthanoid-based rare-earth-oxide-containing coating-coated silicon carbide material characterized by being coated with a complex oxide containing a lanthanoid-based rare-earth element (including yttrium) and chromium to improve the surface emissivity ,

(2) The composition of a composite oxide containing a lanthanoid rare earth element (including yttrium) and chromium is 40 to 50 mol% of a lanthanoid rare earth element (including yttrium) oxide. Chrome is 35
(1) a high-emissivity lanthanoid-based rare earth element oxide-containing coated silicon carbide material according to the above (1), wherein the content is up to 60 mol%, magnesium oxide is 15 mol% or less, and calcium oxide is 10 mol% or less;

(3) The high-emissivity lanthanoid-based oxide-containing silicon carbide-coated silicon carbide according to (1) or (2), wherein the silicon carbide material is a carbon material whose surface is covered with silicon carbide. Material,

(4) The high-emissivity lanthanoid-based rare earth oxide-containing silicon carbide coated silicon carbide material of (3), wherein the carbon material is a carbon / carbon composite;

(5) The silicon carbide material coated with a lanthanoid-based rare earth element oxide-containing film according to any one of (1) to (4) above, wherein a lanthanoid-based rare earth element (including yttrium) and chromium are formed on the outermost surface. A method for producing a high-emissivity lanthanoid-based rare earth oxide-containing coating-coated silicon carbide material, characterized by coating a composite oxide containing by plasma spraying,

(Function) As the silicon carbide material referred to in the present invention, a material composed mostly of silicon carbide, a material whose surface is partially covered with silicon carbide, and a material whose surface is entirely covered with silicon carbide Is raised. As a material mostly composed of silicon carbide, there is a material obtained by sintering silicon carbide powder as carbon, boron or alumina auxiliary agent, and most of commercially available materials are this silicon carbide. Examples of the material whose surface is partially covered with silicon carbide include a material in which one surface of a plate-like carbon material such as carbon / carbon composite is coated with silicon carbide by a chemical vapor deposition method, and a plate-like silicon nitride sintered body. And a material obtained by coating one side of the surface with silicon carbide by chemical vapor deposition. Examples of the material whose entire surface is covered with silicon carbide include a material in which a carbon material such as a carbon / carbon composite is entirely coated with silicon carbide by chemical vapor deposition.

Further, in the present invention, a lanthanoid-based rare earth element (including yttrium) oxide or a lanthanoid-based rare earth, which is a base material for coating a composite oxide containing lanthanoid-based rare earth element (including yttrium) and chromium, is used. A silicon carbide material coated with a composite oxide of an element (including yttrium) and silicon (hereinafter, a lanthanoid-based oxide-containing coated base material) is a portion of the surface of the silicon carbide material covered with silicon carbide A material coated on the entire surface or a part of the surface with a lanthanoid-based rare earth element (including yttrium) oxide or a lanthanoid-based rare earth element (including yttrium) and silicon composite oxide Can be In addition, in order to coat the lanthanoid-based rare earth element oxide-containing coating with good adhesion, a reaction product of a composite oxide of lanthanoid-based rare earth element (including yttrium) and silicon and silicon carbide on the surface of the silicon carbide material. Alternatively, using a conventional technique of forming a layer of a lanthanoid silicide which is a reaction product of an oxide of a lanthanoid-based rare earth element (including yttrium) and silicon carbide between a silicon carbide material and a lanthanoid oxide-containing coating. It doesn't matter.

The lanthanoid-based rare earth elements (1) to (5) (including yttrium; these elements are abbreviated as Ln hereinafter) and a composite oxide containing chromium (hereinafter referred to as Ln).
As Ln constituting rare earth chromite), lanthanum (La) is particularly excellent in that it has a high emissivity. The rare earth chromite may be a composite oxide containing only Ln and chromium, or a composite oxide containing a small amount of atoms such as magnesium and calcium. When the rare earth chromite is composed of Ln oxide and chromium oxide, Ln oxide is 4%.
Chromium oxide has a high emissivity in the composition range of 0 to 50 mol% and 50 to 60 mol%. Magnesium oxide and calcium oxide are added as a sintering aid when rare earth chromite is produced by a sintering method.
If it is 0 mol% or less, the emissivity and high-temperature stability of the rare earth chromite will not be excessively reduced. Further, in terms of sinterability and high-temperature stability, part of chromium oxide is replaced by magnesium oxide, part of Ln oxide is replaced by calcium oxide, and the composition of rare earth chromite is 40%.
-50 mol%, chromium oxide: 35-60 mol%, magnesium oxide: 15 mol% or less, calcium oxide: 10 mol% or less.

The rare earth chromite can be stably present at a high temperature with an Ln oxide-containing film (Ln oxide, composite oxide containing Ln and silicon) to be a base. Rare-earth chromite, compared to chromium oxide alone,
Due to the low vapor pressure of the gas species containing chromium at high temperatures, the rate of weight loss of the chromium oxide component is low, and high emissivity is exhibited for a long time at high temperatures. Therefore, the surface emissivity can be improved by covering the surface of the Ln oxide-containing film with rare earth chromite. However, the emissivity gradually decreases in the process of reducing the amount of the chromium oxide component from the rare earth chromite over a long period of use.

There are various methods for coating the surface of the Ln oxide-containing coating with rare earth chromite, such as a method of coating by plasma spraying, a method of applying and drying a slurry, and a sputtering method. However, plasma spraying is considered to be the most suitable method for coating the surface of the heat-resistant structural material of the spacecraft with the Ln oxide-containing coating from the industrial viewpoints such as the deposition rate and the airtightness of the film. The fact that rare earth chromite can be coated by a plasma spraying method as a process is a great industrial advantage.

When the cross section of the Ln oxide-containing coated silicon carbide material coated with the rare earth chromite according to the present invention described above is observed, it is observed as shown in FIG. 1, that is, the outermost layer corresponding to the upper portion is made of rare earth chromite. The layer 3 exists, the Ln oxide-containing layer 2 exists thereunder, and the silicon carbide material 1 exists thereunder.

[0016]

EXAMPLES Hereinafter, specific examples of the present invention will be described to clarify the effects of the present invention. (Example 1) A graphite material (30 mm × 2) covered entirely with silicon carbide (hereinafter, SiC) by a chemical vapor deposition method (hereinafter, CVD method).
A sample in which several rare earth chromites were sprayed on one surface by atmospheric pressure plasma spraying was prepared using a substrate having a surface of 5 mm × 3 mm) coated with yttrium silicate (Y ₂ SiO ₅ ) by atmospheric pressure plasma spraying. .
The thickness of the silicon carbide layer was about 100 μm, the thickness of the yttrium silicate layer was about 100 μm, and the thickness of the rare earth chromite was about 10 μm. The composition of the rare earth chromite and the surface emissivity at 1700 ° C. of each sample were as shown in Table A.
The emissivity of the sample coated with rare earth chromite is 0.6 or more, and the conventional Y ₂ Si not coated with rare earth chromite
The emissivity of the O ₅ coating was significantly higher than 0.52.

[0017]

[Table 1]

Example 2 Yttrium silicate (Y) was applied to the surface of a graphite material (30 mm × 25 mm × 3 mm) whose entire surface was covered with SiC by the CVD method by the atmospheric pressure plasma spraying method.
₂ SiO ₅ ) as a base material, apply a slurry of rare earth chromite on one surface and dry to obtain 10 mg / c
A sample coated with m ² was prepared. The thickness of the silicon carbide layer is about 1
00 μm, the thickness of the yttrium silicate layer is about 100
μm. Rare earth chromite composition and 170 of each sample
The surface emissivity at 0 ° C. was as shown in Table B. The emissivity of the sample coated with rare earth chromite shows 0.6 or more,
The emissivity of the conventional Y ₂ SiO ₅ coating not coated with the rare earth chromite was significantly higher than the emissivity of 0.52. Also,
Were subjected to cross-section observation of the sample after emissivity measurements, Y ₂ SiO
_No remarkable structural change was observed in the _five layers.

[0019]

[Table 2]

(Example 3) The entire surface is formed of silicon carbide (S) by CVD.
A 30 mm × 25 mm × 3 mm carbon / carbon composite material covered with iC) coated with yttrium silicate (Y ₂ SiO ₅ ) by atmospheric pressure plasma spraying is used as a base material, and Y ₂ O ₃ is coated on one surface. Cr _{2 in} mole%
O ₃ is 50 mol% rare earth chromite and La ₂ O ₃ is 5
Rare earth chromite of 0 mol%, 40 mol% of Cr ₂ O _{3 and} 10 mol% of MgO was coated and dried to obtain 10 mg / mg.
Two kinds of samples coated with cm ² were prepared. The emissivity at 1700 ° C. was 0.62 and 0.83, respectively.

(Example 4) The entire surface is covered with SiC by the CVD method.
Graphite material (30 mm x 25 mm x 3 mm)
Yttrium silicite by atmospheric plasma spraying
(YSi_Two) Is sprayed about 10 μm,_TwoSiO
_FiveAnd Y_TwoO_ThreeWas sprayed. Furthermore, Y_TwoSiO_Five
Layer and Y_TwoO_ThreeNo. of Table A was applied to the surface of the layer. 2 and No.
Sample No. 4 was prepared by spraying rare earth chromite. Si
The thickness of the C layer is about 100 μm, Y_TwoSiO_FiveLayer and Y
_TwoO_ThreeThe thickness of each layer was about 100 μm. Y on base
_TwoSiO_FiveNo. in Table A for the samples coated with Two
And No. Of sample coated with rare earth chromite No.4
The rates are 0.72 and 0.84, respectively, and rare earth chromite
The emissivity of the uncoated sample is significantly higher than 0.52
Improved. Y on base _TwoO_ThreeTable for samples coated with
A No. 2 and No. 4 rare earth chromite coating
The emissivity of the tested samples was 0.70 and 0.80, respectively.
The emissivity of the sample not coated with chromites was 0.42.
It was much better than it was.

In Table C, the test pieces prepared in Examples 1 and 2 were simulated in an environment where the spacecraft is exposed when re-entering the atmosphere, and the environment where the partial pressure of oxygen is 0.002 atm and 1700 ° C.
The result of performing an oxidation test for 10 minutes is shown. There was no significant change in the weight loss rate of the Y ₂ SiO ₅ -coated carbon material by the rare earth chromite coating, and the Y by the rare earth chromite coating
_No deterioration of the oxidation resistance of the ₂ SiO ₅ coating was observed.

[0023]

[Table 3]

The Y ₂ SiO ₅ -coated SiC-coated carbon / carbon composite material coated with the rare earth chromite prepared in Example 3 was heated to 1700 in an environment where the partial pressure of oxygen was 0.002 atm.
An oxidation test at 10 ° C. × 10 minutes was performed. The weight loss of the sample coated with rare earth chromite of 50 mol% of Y ₂ O _{3 and} 50 mol% of Cr ₂ O ₃ was about 0.11%, 50 mol% of La ₂ O _{3 and} 40 mol of Cr ₂ O _3. The weight loss rate of the sample coated with the rare earth chromite in which the molar percentage is 10% by mole of MgO is about 0.13%, and the weight loss rate of the sample not coated with the rare earth chromite is about 0.12%. No deterioration of the oxidation resistance of the Y ₂ SiO ₅ coating due to the rare earth chromite coating was observed.

[0025]

According to the present invention, a silicon carbide material coated with an Ln oxide film having a high surface emissivity can be provided.
The industrial effect is very remarkable.

[Brief description of the drawings]

FIG. 1 is a schematic view of an Ln oxide-containing coating-coated silicon carbide material coated with a rare earth chromite of the present invention.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Riki Fujiwara 10 Nagoya Aerospace System Works, Minato-ku, Nagoya-shi, Aichi Prefecture Mitsubishi Heavy Industries, Ltd. 8-1-chome, Mitsubishi Heavy Industries, Ltd. (72) Inventor Ken Ogura 1-8-1, Koura, Kanazawa-ku, Yokohama-shi, Kanagawa, Japan 1-8-1, Yukiura, Kanazawa-ku, Mitsubishi-shi Basic Technology Research Laboratory, Mitsubishi Heavy Industries, Ltd. (72) Inventor Kei Hiroshi Notomi 5-717-1, Fukahori-cho, Nagasaki-shi, Nagasaki Sanishi Heavy Industries, Ltd. Yasuyuki 5-7-1, Fukabori-cho, Nagasaki-shi, Nagasaki Pref.

Claims (5)

[Claims] 1. A surface of a silicon carbide material coated with an oxide of a lanthanoid-based rare earth element (including yttrium) or a composite oxide of a lanthanoid-based rare earth element (including yttrium) and silicon, and a lanthanoid A high-emissivity lanthanoid-based rare-earth oxide-containing silicon-coated silicon carbide material characterized by being coated with a complex oxide containing a rare earth element (including yttrium) and chromium to improve the surface emissivity. 2. The composition of a composite oxide containing a lanthanoid-based rare earth element (including yttrium) and chromium,
40 to 50 mol% of oxide of lanthanoid rare earth element (including yttrium) and 35 to 50% of chromium oxide
The high-emissivity lanthanoid-based rare-earth-element-oxide-containing coated silicon carbide material according to claim 1, wherein the content is 60 mol%, the content of magnesium oxide is 15 mol% or less, and the content of calcium oxide is 10 mol% or less. 3. The silicon carbide material is a carbon material whose surface is covered with silicon carbide.
2. The silicon carbide material coated with a high-emissivity lanthanoid-based rare earth element oxide-containing film according to item 1. 4. The silicon carbide material coated with a high-emissivity lanthanoid-based rare earth oxide-containing coating according to claim 3, wherein the carbon material is a carbon / carbon composite. 5. A composite oxide containing the lanthanoid-based rare earth element (including yttrium) and chromium on the outermost surface of the silicon carbide material coated with a lanthanoid-based rare earth element oxide according to any one of claims 1 to 4. A method for producing a silicon carbide material coated with a high-emissivity lanthanoid-based rare earth element oxide-containing coating, characterized in that the material is coated by a plasma spraying method.