ORTHOPHOSPHATE THERMAL BARRIER COATING MATERIAL WITH HIGH COEFFICIENT OF THERMAL EXPANSION AND PREPARATION METHOD THEREOF

Abstract

The present disclosure relates to an orthophosphate thermal barrier coating material with high coefficient of thermal expansion and a preparation method thereof. ReM.sub.3P.sub.3O.sub.12 series ceramics with an eulytite crystal structure are prepared by a high-temperature solid-phase reaction for the first time. The ReM.sub.3P.sub.3O.sub.12 ceramic belongs to a −43 m space group of a cubic crystal system, which not only has a higher melting point and excellent high-temperature phase stability, but also has a lower thermal conductivity and a suitable coefficient of thermal expansion. It can effectively alleviate the stress caused by the mismatch of the coefficient of thermal expansion of the base material and the ceramic layer, so as to meet the requirements of thermal insulation and high-temperature oxidation and corrosion resistance of the hot end parts in long-term service, which has application prospects in the field of thermal barrier coatings.

Claims

1. An orthophosphate thermal barrier coating material with high coefficient of thermal expansion, having a general chemical formula of ReM.sub.3P.sub.3O.sub.12, which belongs to a −43 m space group of a cubic crystal system with an eulytite crystal structure, wherein Re is a rare earth element, and M is an alkaline earth metal.

2. The orthophosphate thermal barrier coating material with high coefficient of thermal expansion according to claim 1, wherein Re is one or two or a combination of more than two of Y, La, Nd, Sm, Gd, Dy, Ho, Er or Yb, and M is one or two or a combination of more than two of Sr, Ca or Ba.

3. The orthophosphate thermal barrier coating material with high coefficient of thermal expansion according to claim 1, wherein the orthophosphate thermal barrier coating material is selected from one of NdBa.sub.3P.sub.3O.sub.12, GdBa.sub.3P.sub.3O.sub.12, DyBa.sub.3P.sub.3O.sub.12, HoBa.sub.3P.sub.3O.sub.12, or ErBa.sub.3P.sub.3O.sub.12.

4. A method for preparing the orthophosphate thermal barrier coating material with high coefficient of thermal expansion according to claim 1, wherein comprising the following steps: (1) Mixing a rare earth oxide, an alkaline earth metal-containing compound and a P-containing compound uniformly according to a molar ratio of 1:(4-8):(4-8), placing in a muffle furnace, heating up to 1000° C.-1100° C., and maintaining a constant temperature to perform a first sintering for 4-6 h to obtain a pre-sintered raw material; (2) Grinding and pressing the pre-sintered raw material, placing in the muffle furnace, heating up to 1300° C.-1500° C., and performing a second sintering to obtain a pure phase material; (3) Adding the pure phase material to absolute ethanol, ball milling for 20-30 h using a wet ball milling method, then drying; grinding, sieving, and pressing into a green body; (4) Placing the green body in the muffle furnace, heating up to 1500° C.-1700° C., performing a high-temperature reaction in an air atmosphere, and cooling down with the furnace after the reaction is completed to obtain an orthophosphate thermal barrier coating material with high coefficient of thermal expansion.

5. The preparation method according to claim 4, wherein in step (1), the molar ratio of the rare earth oxide, the alkaline earth metal-containing compound and the P-containing compound is 1:6:6.

6. The preparation method according to claim 4, wherein in step (1), the rare earth oxide is one or two or a combination of more than two of Y.sub.2O.sub.3, La.sub.2O.sub.3, Nd.sub.2O.sub.3, Sm.sub.2O.sub.3, Gd.sub.2O.sub.3, Dy.sub.2O.sub.3, Ho.sub.2O.sub.3, Er.sub.2O.sub.3 or Yb.sub.2O.sub.3; the purity of the rare earth oxide is greater than 99.99%, the alkaline earth metal-containing compound is one or two or a combination of more than two of BaCO.sub.3 or SrCO.sub.3 or BaCO.sub.3, and the P-containing compound is ammonium dihydrogen phosphate.

7. The preparation method according to claim 4, wherein in step (1), the particle sizes of rare earth oxides, carbonates, and ammonium dihydrogen phosphate are 50-100 μm, the first sintering temperature is 1000° C., the time for maintaining the constant temperature is 5 h, and the heating rate of the first sintering is 8-12° C./min.

8. The preparation method according to claim 4, wherein in step (2), the second sintering temperature is 1400° C., the time for maintaining the constant temperature is 5 h, and the heating rate of the second sintering is 8-12° C./min.

9. The preparation method according to claim 4, wherein in step (3), the mass ratio of the added amount of absolute ethanol to the pure phase material is 1: (2-6), and the pressure for pressing into a green body is 200-350 MPa.

10. The preparation method according to claim 4, wherein in step (4), the high-temperature reaction temperature is 1600-1700° C., the heating rate is 1-3° C./min, and the high-temperature reaction time is more than or equal to 5 h; preferably, the high-temperature reaction time is 8-20 h.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] 1401 FIG. 1 is an XRD pattern of the thermal barrier coating material ReM.sub.3P.sub.3O.sub.12 of Examples 1-5;

[0038] FIG. 2 shows the hardness of the thermal barrier coating material ReM.sub.3P.sub.3O.sub.12 of Examples 1-5;

[0039] FIG. 3 shows the modulus of elasticity of the thermal barrier coating material ReM.sub.3P.sub.3O.sub.12 of Examples 1-5;

[0040] FIG. 4 is a TG-DTA curve of the thermal barrier coating material ReM.sub.3P.sub.3O.sub.12 of Examples 1-5; a is NdBP material, b is GdBP material, c is DyBP material, d is HoBP material, and e is ErBP material.

[0041] FIG. 5 shows a temperature dependence of coefficient of thermal expansion of the thermal barrier coating material ReM.sub.3P.sub.3O.sub.12 of Examples 1-5;

[0042] FIG. 6 shows a temperature dependence of thermal conductivity of the thermal barrier coating material ReM.sub.3P.sub.3P.sub.12 of Examples 1-5.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] 1461 The present disclosure is further illustrated in conjunction with examples and drawings, but is not limited thereto.

Example 1

[0044] NdBa.sub.3P.sub.3O.sub.12 was prepared by cerium oxide, barium carbonate and ammonium dihydrogen phosphate, steps are as follows:

[0045] (1) Nd.sub.2O.sub.3, BaCO.sub.3 and NH.sub.4H.sub.2PO.sub.4 were taken as raw materials and mixed according to the molar ratio of 1:6:6;

[0046] (2) The raw materials prepared in step (1) were mixed uniformly and placed into an alumina crucible, then placed in a muffle furnace for a first sintering, the sintering temperature was 1000±50° C., the temperature was maintained for 5 h to remove the CO.sub.2, NH.sub.3 and H.sub.2O in the raw materials to obtain a pre-sintered raw material;

[0047] (3) The pre-sintered raw material in step (2) was ground, pressed into a rod shape, and placed in the muffle furnace for a second sintering at a sintering temperature of 1400° C. to obtain a pure phase material;

[0048] (4) The pure phase material was added to absolute ethanol and ball milled for 48 h, the mass ratio of the added amount of absolute ethanol to the pure phase material was 1:3, and then dried;

[0049] (5) The powder in step (4) was fully ground, sieved (200 mesh), and pressed into a green body under 300 MPa;

[0050] (6) The green body was placed into the muffle furnace, heated up to 1600° C., subjected to a high-temperature reaction in an air atmosphere for 10 h, and then cooled down with the furnace;

[0051] (7) The reactant after cooling was taken out to obtain a material with a chemical formula of NdBa.sub.3P.sub.3O.sub.12 (abbreviation: NdBP).

[0052] The prepared product has a thermal conductivity at room temperature of 0.95 W/m.Math.K, a coefficient of thermal expansion of 21.6×10.sup.−6/° C. (1000° C.), a hardness of 7.4 GPa, and a modulus of elasticity of 90 GPa.

Example 2

[0053] GdBa.sub.3P.sub.3O.sub.12 was prepared by gadolinium oxide, barium carbonate and ammonium dihydrogen phosphate, steps are as follows:

[0054] (1) Gd.sub.2O.sub.3, BaCO.sub.3 and NH.sub.4H.sub.2PO.sub.4 were taken as raw materials and mixed according to the molar ratio of 1:6:6;

[0055] (2) The raw materials prepared in step (1) were mixed uniformly and placed into an alumina crucible, then placed in a muffle furnace for a first sintering, the sintering temperature was 1000±50° C., the temperature was maintained for 5 h to remove the CO.sub.2, NH.sub.3 and H.sub.2O in the raw materials to obtain a pre-sintered raw material;

[0056] (3) The pre-sintered raw material in step (2) was ground, pressed into a rod shape, and placed in the muffle furnace for a second sintering at a sintering temperature of 1400° C. to obtain a pure phase material;

[0057] (4) The pure phase material was added to absolute ethanol and ball milled for 48 h, the mass ratio of the added amount of absolute ethanol to the pure phase material was 1:3, and then dried;

[0058] (5) The powder in step (4) was fully ground, sieved (200 mesh), and pressed into a green body under 300 MPa;

[0059] (6) The green body was placed into the muffle furnace, heated up to 1600° C., subjected to a high-temperature reaction in an air atmosphere for 10 h, and then cooled down with the furnace;

[0060] (7) The reactant after cooling was taken out to obtain a material with a chemical formula of GdBa.sub.3P.sub.3O.sub.12 (abbreviation: GdBP).

[0061] The prepared product has a thermal conductivity at room temperature of 0.78 W/m.Math.K, a coefficient of thermal expansion of 20.5×10.sup.−6/° C. (1000° C.), a hardness of 7.7 GPa, and a modulus of elasticity of 105 GPa.

Example 3

[0062] DyBa.sub.3P.sub.3O.sub.12 was prepared by dysprosium oxide, barium carbonate and ammonium dihydrogen phosphate, steps are as follows:

[0063] (1) Dy.sub.2O.sub.3, BaCO.sub.3 and NH.sub.4H.sub.2PO.sub.4 were taken as raw materials and mixed according to the molar ratio of 1:6:6;

[0064] (2) The raw materials prepared in step (1) were mixed uniformly and placed into an alumina crucible, then placed in a muffle furnace for a first sintering, the sintering temperature was 1000±50° C., the temperature was maintained for 5 h to remove the CO.sub.2, NH.sub.3 and H.sub.2O in the raw materials to obtain a pre-sintered raw material;

[0065] (3) The pre-sintered raw material in step (2) was ground, pressed into a rod shape, and placed in the muffle furnace for a second sintering at a sintering temperature of 1400° C. to obtain a pure phase material;

[0066] (4) The pure phase material was added to absolute ethanol and ball milled for 48 h, the mass ratio of the added amount of absolute ethanol to the pure phase material was 1:3, and then dried;

[0067] (5) The powder in step (4) was fully ground, sieved (200 mesh), and pressed into a green body under 300 MPa;

[0068] (6) The green body was placed into the muffle furnace, heated up to 1600° C., subjected to a high-temperature reaction in an air atmosphere for 10 h, and then cooled down with the furnace;

[0069] (7) The reactant after cooling was taken out to obtain a material with a chemical formula of DyBa.sub.3P.sub.3O.sub.12 (abbreviation: DyBP).

[0070] The prepared product has a thermal conductivity at room temperature of 0.83 W/m.Math.K, a coefficient of thermal expansion of 19.8×10.sup.−6/° C. (1000° C.), a hardness of 8.2 GPa, and a modulus of elasticity of 100 GPa.

Example 4

[0071] HoBa.sub.3P.sub.3O.sub.12 was prepared by holmium oxide, barium carbonate and ammonium dihydrogen phosphate, steps are as follows:

[0072] (1) Ho.sub.2O.sub.3, BaCO.sub.3 and NH.sub.4H.sub.2PO.sub.4 were taken as raw materials and mixed according to the molar ratio of 1:6:6;

[0073] (2) The raw materials prepared in step (1) were mixed uniformly and placed into an alumina crucible, then placed in a muffle furnace for a first sintering, the sintering temperature was 1000±50° C., the temperature was maintained for 5 h to remove the CO.sub.2, NH.sub.3 and H.sub.2O in the raw materials to obtain a pre-sintered raw material;

[0074] (3) The pre-sintered raw material in step (2) was ground, pressed into a rod shape, and placed in the muffle furnace for a second sintering at a sintering temperature of 1400° C. to obtain a pure phase material;

[0075] (4) The pure phase material was added to absolute ethanol and ball milled for 48 h, the mass ratio of the added amount of absolute ethanol to the pure phase material was 1:3, and then dried;

[0076] (5) The powder in step (4) was fully ground, sieved (200 mesh), and pressed into a green body under 300 MPa;

[0077] (6) The green body was placed into the muffle furnace, heated up to 1600° C., subjected to a high-temperature reaction in an air atmosphere for 10 h, and then cooled down with the furnace;

[0078] (7) The reactant after cooling was taken out to obtain a material with a chemical formula of HoBa.sub.3P.sub.3O.sub.z(abbreviation: HoBP).

[0079] The prepared product has a thermal conductivity at room temperature of 0.87 W/m.Math.K, a coefficient of thermal expansion of 19.2×10.sup.−6/° C. (1000° C.), a hardness of 10.6 GPa, and a modulus of elasticity of 111 GPa.

Example 5

[0080] ErBa.sub.3P.sub.3O.sub.z was prepared by erbium oxide, barium carbonate and ammonium dihydrogen phosphate, steps are as follows:

[0081] (1) Er.sub.2O.sub.3, BaCO.sub.3 and NH.sub.4H.sub.2PO.sub.4 were taken as raw materials and mixed according to the molar ratio of 1:6:6;

[0082] (2) The raw materials prepared in step (1) were mixed uniformly and placed into an alumina crucible, then placed in a muffle furnace for a first sintering, the sintering temperature was 1000±50° C., the temperature was maintained for 5 h to remove the CO.sub.2, NH.sub.3 and H.sub.2O in the raw materials to obtain a pre-sintered raw material;

[0083] (3) The pre-sintered raw material in step (2) was ground, pressed into a rod shape, and placed in the muffle furnace for a second sintering at a sintering temperature of 1400° C. to obtain a pure phase material;

[0084] (4) The pure phase material was added to absolute ethanol and ball milled for 48 h, the mass ratio of the added amount of absolute ethanol to the pure phase material was 1:3, and then dried;

[0085] (5) The powder in step (4) was fully ground, sieved (200 mesh), and pressed into a green body under 300 MPa;

[0086] (6) The green body was placed into the muffle furnace, heated up to 1600° C., subjected to a high-temperature reaction in an air atmosphere for 10 h, and then cooled down with the furnace;

[0087] (7) The reactant after cooling was taken out to obtain a material with a chemical formula of ErBa.sub.3P.sub.3O.sub.12 (abbreviation: ErBP).

[0088] The prepared product has a thermal conductivity at room temperature of 0.77 W/m.Math.K, a coefficient of thermal expansion of 18.2×10.sup.−6/° C. (1000° C.), a hardness of 9.3 GPa, and a modulus of elasticity of 107 GPa.

Experimental Example

[0089] 1. The thermal barrier coating materials ReM.sub.3P.sub.3O.sub.z of Examples 1-5 were subjected to XRD testing, and the results are shown in FIG. 1.

[0090] 2. The hardness of the thermal barrier coating materials ReM.sub.3P.sub.3O.sub.12 of Examples 1-5 is shown in FIG. 2; the modulus of elasticity is shown in FIG. 3; the TG-DTA curve is shown in FIG. 4; the coefficient of thermal expansion is shown in FIG. 5; and the thermal conductivity is shown in FIG. 6.