Material for cold spraying

1. A material for cold spraying, comprising a powder of a compound of a rare earth element with a specific surface area of 30 m 2 /g or more as determined by a BET single-point method,

wherein the material has a volume of pores with a pore size of 3 to 20 nm of 0.08 cm 3 /g or more as determined by a gas absorption method.

2. The material for cold spraying according to claim 1 , wherein the powder has a crystallite diameter of 25 nm or less.

3. The material for cold spraying according to claim 1 , having a repose angle of from 10 to 60°.

4. The material for cold spraying according to claim 1 , having, in an L*a*b* color system, a value L of 85 or more, a value a of from −0.7 to 0.7, and a value b of from −1 to 2.5.

5. The material for cold spraying according to claim 1 , wherein the compound of the rare earth element is at least one selected from the group consisting of a rare earth element oxide, a rare earth element fluoride, and a rare earth element oxyfluoride.

6. The material for cold spraying according to claim 1 , wherein the rare earth element is yttrium.

7. The material for cold spraying according to claim 1 , wherein, in X-ray diffractometry on the material using Cu-Kα rays or Cu-Kα 1 rays, a maximum peak exhibited at 2θ=10 to 90° is assigned to YF 3 , Y 2 O 3 , YOF or Y 5 O 4 F 7 .

8. The material for cold spraying according to claim 1 ,

wherein the material has the volume of pores with the pore size of 20 nm or less of 0.03 cm 3 /g or more as determined by a mercury intrusion porosimetry.

9. A method for producing a coating by a cold spraying method,

wherein the coating contains the material according to claim 1 .

10. A method for producing the material for cold spraying according to claim 1 , the compound of a rare earth element being a rare earth element oxide,

the method comprising:

dissolving a powder of a rare earth element oxide in a warmed weakly acidic aqueous solution and then cooling down the resulting solution to thereby allow a weak acid salt of the rare earth element to precipitate; and

firing the weak acid salt at 450 to 950° C.

11. A method for producing the material for cold spraying according to claim 1 , the compound of a rare earth element being a rare earth element fluoride,

the method comprising:

mixing an aqueous solution of a water-soluble salt of a rare earth element with hydrofluoric acid to thereby allow a rare earth element fluoride to deposit; and

drying the obtained deposit at 250° C. or less,

wherein firing is not performed after the drying.

12. A method for producing the material for cold spraying according to claim 1 , the compound of a rare earth element being a rare earth element oxyfluoride,

the method comprising:

the first step of mixing, with hydrofluoric acid, a powder of a rare earth element oxide or a precursor that forms a rare earth element oxide when being fired, to thereby obtain a precursor of a rare earth element oxyfluoride; and

the second step of firing the precursor of the rare earth element oxyfluoride.

13. The method for producing the material for cold spraying according to claim 12 , further comprising: dissolving a powder of a rare earth element oxide in a warmed weakly acidic aqueous solution and then cooling down the resulting solution to thereby allow a weak acid salt of the rare earth element to precipitate; and firing the weak acid salt at 450 to 950° C. to thereby obtain a powder of a rare earth element oxide, wherein the obtained powder of a rare earth element oxide is used as the rare earth element oxide in the first step.

14. The method for producing the material for cold spraying according to claim 12 , wherein, in the first step, a rare earth element carbonate is used as the precursor that forms a rare earth element oxide when being fired.

15. The method for producing the material for cold spraying according to claim 14 , wherein the rare earth element carbonate is obtained by allowing a water-soluble salt of a rare earth element selected from the group consisting of a rare earth element nitrate and a rare earth element hydrochloride to react with a hydrogen carbonate selected from the group consisting of an ammonium hydrogen carbonate, a sodium hydrogen carbonate, and a potassium hydrogen carbonate.

16. A material for cold spraying, comprising a powder of a compound of a rare earth element with a specific surface area of 30 m 2 /g or more as determined by a BET single-point method,

wherein the material has a volume of pores with a pore size of 20 nm or less of 0.03 cm 3 /g or more as determined by a mercury intrusion porosimetry.

17. A material for cold spraying, comprising a powder of a compound of a rare earth element with a specific surface area of 45 to 325 m 2 /g as determined by a BET single-point method,

wherein the compound of the rare earth element is at least one selected from the group consisting of a rare earth element oxide, a rare earth element fluoride, and a rare earth element oxyfluoride,

the powder has a crystallite diameter of from 3 to 25 nm, and

the material has a volume of pores with a pore size of 3 to 20 nm of from 0.08 to 1.0 cm 3 /g as determined by a gas absorption method.

18. The material for cold spraying according to claim 17 ,

wherein the material has a repose angle of from 20 to 50°,

the material has a cumulative volume particle size at a cumulative volume of 50 vol % as determined by a laser diffraction/scattering particle size distribution measurement, D 50N , of from 1.5 to 80 μm,

the material has a cumulative volume particle size at cumulative volume of 50 vol % as determined by a laser diffraction/scattering particle size distribution measurement after ultrasonication at 300 W for 15 minutes, D 50D , of from 0.3 to 30 μm, and

in an L*a*b* color system, the material has a value L of 90 or more, a value a of from −0.7 to 0.7, and a value b of from −1 to 2.5.