Nickel-titanium alloy material, preparation method of nickel-titanium alloy material and application of nickel-titanium alloy material in intelligent ring

Abstract

The invention belongs to the technical field of alloy materials, and particularly relates to a nickel-titanium alloy material, a preparation method thereof and application of the nickel-titanium alloy material in an intelligent ring. According to the nickel-titanium alloy material and the preparation method thereof, urea and ammonium bicarbonate are selected as compound additives and are used together with carbon-doped gadolinium oxide, and a composite coating is formed on the surface of the sintered alloy, so that the nickel-titanium alloy material is prepared, the tensile strength and the compression strength of the material are effectively improved, and the elastic modulus is increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of alloy materials, and particularly relates to a nickel-titanium alloy material, a preparation method thereof, and an application in a smart ring. Background Art

[0002] As a metal material with special properties such as superelasticity, corrosion resistance, shape memory, and biocompatibility, nickel-titanium alloy can undergo martensitic transformation under the induction of external force or temperature and recover a certain amount of deformation. It has now been widely used in fields such as aerospace, biomedicine, robotics, and microelectronics. Nickel-titanium alloy can be deformed at low temperatures and can return to its original shape when heated to a certain temperature; within a certain temperature range, nickel-titanium alloy exhibits very high elastic deformation ability, and even if it undergoes large deformation under external force, it can quickly return to its original shape after the external force is removed; it shows excellent corrosion resistance in various environments and is suitable for use under harsh conditions.

[0003] Chinese Patent (Publication No. CN116356176A) discloses a powder metallurgy porous nickel-titanium alloy and a preparation method thereof. This invention uses the method of pore formation with NaCl combined with sintering in an argon atmosphere to prepare porous nickel-titanium alloy. This method can obtain a higher porosity compared with the commonly used vacuum sintering method. At the same time, by limiting the addition amount of NaCl powder and specific sintering parameters, the prepared porous nickel-titanium alloy has a uniform pore size distribution, and the appropriate connectivity between pores can effectively promote the exchange of nutrients between pores after implantation into the human body, fully meeting the human implantation requirements. However, when the nickel-titanium alloy material is applied to a smart ring in the prior art, there are problems such as insufficient tensile strength and compressive strength, and the elastic modulus needs to be improved, which seriously affects its actual use.

[0004] Therefore, how to introduce modified components into the nickel-titanium alloy, form a composite coating on the surface of the alloy, prepare a nickel-titanium alloy material, improve the tensile strength and compressive strength of the material, and increase the elastic modulus has become the key direction to be overcome. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a nickel-titanium alloy material, a preparation method thereof, and an application in a smart ring, aiming to solve the problems of insufficient tensile strength and compressive strength and the need to improve the elastic modulus when the nickel-titanium alloy material is applied to a smart ring in the prior art.

[0006] The present invention uses urea and ammonium bicarbonate as compound additives, in combination with carbon-doped gadolinium oxide, and forms a composite coating on the surface of the sintered alloy, thereby preparing a nickel-titanium alloy material, effectively improving the tensile strength and compressive strength of the material, and increasing the elastic modulus.

[0007] The technical solution adopted by the present invention to solve the above technical problems is as follows:

[0008] In a first aspect of the present invention, a method for preparing a nickel-titanium alloy material is provided, comprising the following steps:

[0009] S1: By weight, 40-50 parts of nickel powder, 30-40 parts of titanium powder, 6-10 parts of gadolinium oxide, and 12-18 parts of an additive are mixed to obtain a mixed powder;

[0010] S2: The mixed powder is cold-pressed into a green body, and after demolding, the green body is sintered to obtain alloy A;

[0011] S3: By weight, 2-4 parts of graphene oxide are added to 400-500 parts of deionized water and ultrasonically dispersed evenly, and then 400-500 parts of a 2-4 mg / mL hydrochloric acid dopamine buffer solution are added and mixed evenly to obtain a co-deposition solution; the alloy A is pretreated and then completely immersed in the co-deposition solution for surface modification to form a composite coating on the surface of alloy A, obtaining a nickel-titanium alloy material.

[0012] As a preferred technical solution of the present invention, the conditions for the mixing treatment in step S1 include: in an argon atmosphere, the nickel powder and titanium powder are first mixed for a first ball milling treatment (rotation speed: 400-800 r / min, time: 6-8 h) to obtain a precursor mixed powder, and then gadolinium oxide and an additive are added to the precursor mixed powder for a second ball milling treatment (rotation speed: 100-200 r / min, time: 2-4 h).

[0013] As a preferred technical solution of the present invention, the conditions for sintering in step S2 include: sintering vacuum degree: 2-6 Pa, heating rate: 60-80 °C / min, sintering temperature: 900-1100 °C, sintering holding time: 10-20 min, and after sintering, it is naturally cooled to room temperature in the furnace and demolded.

[0014] As a preferred technical solution of the present invention, the conditions for cold pressing in step S2 include: pressure: 400-600 MPa, time: 2-4 min.

[0015] As a preferred technical solution of the present invention, the conditions for pretreatment in step S3 include: sandpaper polishing, ultrasonic cleaning with acetone, absolute ethanol, and deionized water in sequence, and drying;

[0016] As a preferred technical solution of the present invention, the conditions for surface modification in step S3 include: adjusting the pH to 8.4-8.8, soaking at 24-28 °C for 70-72 h, taking out and washing with deionized water, and vacuum drying.

[0017] Polydopamine has excellent surface adhesion and can form a uniform composite coating on the surface of nickel-titanium alloy through self-assembly. The composite coating of polydopamine-graphene oxide can form a multi-level structure by regulating the distribution and orientation of graphene oxide. Through the multi-level structure, the stress distribution can be further optimized, local stress concentration can be reduced, and thus the overall elastic modulus of the material can be improved.

[0018] As a preferred technical solution of the present invention, the gadolinium oxide is carbon-doped gadolinium oxide;

[0019] As a preferred technical solution of the present invention, the preparation method of the carbon-doped gadolinium oxide includes: by weight, adding 4-6 parts of sodium hydroxide to 100-120 parts of deionized water and dissolving it fully, then adding 6-10 parts of gadolinium chloride hexahydrate and stirring to obtain an intermediate product; adding 6-10 parts of the intermediate product and 2-4 parts of citric acid to 120-140 parts of deionized water, transferring it to a reaction kettle for heating reaction to obtain carbon-doped gadolinium oxide.

[0020] As a preferred technical solution of the present invention, the conditions of the stirring treatment include: stirring at a speed of 100-120 r / min for 18-20 h, vacuum drying at 110-120 °C for 6-8 days, and grinding.

[0021] As a preferred technical solution of the present invention, the conditions of the heating reaction include: heating at 190-200 °C for 6-8 h, cooling to room temperature, dialysis, and freeze-drying.

[0022] The carbon-doped gadolinium oxide is uniformly dispersed in the nickel-titanium alloy matrix in the form of nanoparticles, hindering the movement of dislocations as the second-phase particles. At the same time, the carbon-doped gadolinium oxide particles can serve as pinning points to prevent the excessive growth of metal grains during the high-temperature sintering process, and improve the tensile strength of the alloy through the grain refinement effect.

[0023] As a preferred technical solution of the present invention, the additives are urea and ammonium bicarbonate.

[0024] As a preferred technical solution of the present invention, the mass ratio of urea to ammonium bicarbonate in the additives is (1-2):1.

[0025] Ammonium bicarbonate in the additives will be completely removed during the sintering process, thus achieving efficient pore formation in the nickel-titanium alloy group without generating residues; at the same time, the pores formed after the removal of ammonium bicarbonate can serve as carriers, and part of the carbon quantum dots in the carbon-doped gadolinium oxide will migrate to the pore carriers at high temperature and combine with the active nitrogen source generated by the decomposition of urea during the sintering process to form graphitic carbon nitride. The layered structure of graphitic carbon nitride can absorb part of the energy during the compression process, prevent the initiation and propagation of cracks, and thus improve the compression strength of the nickel-titanium alloy material.

[0026] In the second aspect of the present invention, a nickel-titanium alloy material prepared by the method described in the first aspect is provided.

[0027] In the third aspect of the present invention, an application of a nickel-titanium alloy material prepared by the method described in the first aspect in a smart ring is provided.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) In the present invention, urea and ammonium bicarbonate are selected to form a compound additive. Ammonium bicarbonate will be removed during the sintering process to form a pore carrier, and the carbon quantum dots in carbon-doped gadolinium oxide will migrate to the pore carrier. At the same time, the active nitrogen source generated by the decomposition of the other additive urea in the pore carrier under high-temperature conditions combines with the carbon quantum dots to form graphitic carbon nitride; in the subsequent preparation process of the composite coating, both graphene oxide and graphitic carbon nitride have a conjugated π-electron system, and polydopamine has excellent surface adhesion, and a uniform coating can be formed on the surface of the nickel-titanium alloy through a self-polymerization reaction. Both graphene oxide and graphitic carbon nitride have a conjugated π-electron system, and the two form a tight interfacial bond through π-π stacking, effectively improving the tensile strength and compressive strength of the nickel-titanium alloy material and increasing the elastic modulus.

[0030] (2) The carbon-doped gadolinium oxide in the present invention is uniformly dispersed in the nickel-titanium alloy matrix in the form of nanoparticles, hindering dislocation movement as a second-phase particle. At the same time, the carbon-doped gadolinium oxide particles can serve as pinning points to prevent the excessive growth of metal grains during the high-temperature sintering process, and improve the tensile strength of the alloy through the grain refinement effect.

[0031] (3) Ammonium bicarbonate in the additive of the present invention will be completely removed during the sintering process, thus achieving efficient pore formation in the nickel-titanium alloy group without residue; at the same time, the pores formed after the removal of ammonium bicarbonate can serve as carriers, and part of the carbon quantum dots in carbon-doped gadolinium oxide will migrate to the pore carriers at high temperature and combine with the active nitrogen source generated by the decomposition of urea during the sintering process to form graphitic carbon nitride. The layered structure of graphitic carbon nitride can absorb part of the energy during the compression process, preventing the initiation and propagation of cracks, thereby improving the compressive strength of the nickel-titanium alloy material.

[0032] (4) Polydopamine in the present invention has excellent surface adhesion and can form a uniform composite coating on the surface of the nickel-titanium alloy through self-assembly. The composite coating of polydopamine-graphene oxide can form a multi-level structure by regulating the distribution and orientation of graphene oxide. The multi-level structure can further optimize the stress distribution and reduce local stress concentration, thereby improving the overall elastic modulus of the material. Detailed implementation mode

[0033] To facilitate the understanding of the present invention, the following embodiments are listed. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0034] The sources of some components in the examples and comparative examples are as follows:

[0035] Nickel powder, CAS No. 7440-02-0, purchased from Shanghai Macklin Biochemical Co., Ltd.;

[0036] Titanium powder, CAS No. 7440-32-6, purchased from Shanghai Macklin Biochemical Co., Ltd.;

[0037] Commercially available gadolinium oxide, CAS No. 12064-62-9, purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0038] Urea, CAS No. 57-13-6, purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0039] Ammonium bicarbonate, CAS No. 1066-33-7, purchased from Shanghai Macklin Biochemical Co., Ltd.;

[0040] Sodium chloride, CAS No. 7647-14-5, purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0041] Gadolinium chloride hexahydrate, CAS No. 13450-84-5, purchased from Shanghai Macklin Biochemical Co., Ltd.;

[0042] Sodium hydroxide, CAS No. 1310-73-2, purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0043] Citric acid, CAS No. 77-92-9, purchased from Shanghai Macklin Biochemical Co., Ltd.;

[0044] Graphene oxide, product number G139803, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0045] Hydrochloric acid dopamine, CAS No. 62-31-7, purchased from Shanghai Macklin Biochemical Co., Ltd.;

[0046] Tris-HCl buffer solution, product number T301494, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0047] Acetone, CAS No. 67-64-1, purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0048] Absolute ethanol, CAS No. 64-17-5, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0049] Example 1

[0050] This embodiment provides a preparation method of a nickel-titanium alloy material, comprising the following steps:

[0051] S1: By weight, first mix 50 parts of nickel powder and 40 parts of titanium powder for the first ball milling treatment (rotation speed is 800 r / min, time is 6 h) to obtain a precursor mixed powder, and then add 10 parts of carbon-doped gadolinium oxide and 18 parts of additives (12 parts of urea and 6 parts of ammonium bicarbonate) to the precursor mixed powder for the second ball milling treatment (rotation speed is 200 r / min, time is 2 h) to obtain a mixed powder;

[0052] S2: Cold-press the mixed powder (pressure is 600 MPa, time is 2 min), demold to obtain a green body, then sinter the green body. The sintering vacuum degree is 6 Pa, the heating rate is 80 °C / min, the sintering temperature is 1100 °C, the sintering holding time is 10 min, and after sintering, it is naturally cooled to room temperature in the furnace, demolded to obtain alloy A;

[0053] S3: By weight, add 4 parts of graphene oxide to 500 parts of deionized water and ultrasonically disperse evenly, then add 500 parts of 4 mg / mL dopamine hydrochloride buffer solution (dissolve dopamine hydrochloride in Tris-HCl buffer solution) and mix evenly to obtain a co-deposition solution; Pretreat alloy A, polish with sandpaper, ultrasonically clean with acetone, absolute ethanol, and deionized water in sequence, dry, and then completely immerse it in the co-deposition solution for surface modification, adjust the pH to 8.8, soak at 28 °C for 70 h, take it out, wash with deionized water, vacuum dry, and form a composite coating on the surface of alloy A to obtain the nickel-titanium alloy material.

[0054] Preparation of the carbon-doped gadolinium oxide: By weight, add 6 parts of sodium hydroxide to 120 parts of deionized water and dissolve fully, then add 10 parts of gadolinium chloride hexahydrate and stir. Stir at a rotation speed of 120 r / min for 18 h, vacuum dry at 120 °C for 6 days, grind to obtain an intermediate product; Add 10 parts of the intermediate product and 4 parts of citric acid to 140 parts of deionized water, transfer to a reaction kettle for heating reaction, heat at 200 °C for 6 h, cool to room temperature, dialyze, and freeze-dry to obtain carbon-doped gadolinium oxide.

[0055] Example 2

[0056] This embodiment provides a preparation method of a nickel-titanium alloy material, comprising the following steps:

[0057] S1: By weight, in an argon atmosphere, first mix 40 parts of nickel powder and 30 parts of titanium powder for the first ball milling treatment (rotation speed: 400 r / min, time: 8 h) to obtain a precursor mixed powder. Then, add 6 parts of carbon-doped gadolinium oxide and 12 parts of additives (6 parts of urea and 6 parts of ammonium bicarbonate) to the precursor mixed powder for the second ball milling treatment (rotation speed: 100 r / min, time: 4 h) to obtain a mixed powder;

[0058] S2: Cold press the mixed powder (pressure: 400 MPa, time: 4 min). After demolding, a green compact is obtained. Then, sinter the green compact. The sintering vacuum degree is 2 Pa, the heating rate is 60 °C / min, the sintering temperature is 900 °C, and the sintering holding time is 20 min. After sintering, naturally cool it to room temperature in the furnace, demold, and obtain alloy A;

[0059] S3: By weight, add 2 parts of graphene oxide to 400 parts of deionized water and disperse it evenly by ultrasonic treatment. Then, add 400 parts of 2 mg / mL dopamine hydrochloride buffer solution (dissolve dopamine hydrochloride in Tris-HCl buffer solution) and mix evenly to obtain a co-deposition solution. Pretreat alloy A by sanding, and ultrasonically clean it successively with acetone, absolute ethanol, and deionized water, and then dry it. Then, completely immerse it in the co-deposition solution for surface modification. Adjust the pH to 8.4 and soak it at 24 °C for 72 h. After taking it out, wash it with deionized water and dry it in vacuum to form a composite coating on the surface of alloy A, and obtain a nickel-titanium alloy material.

[0060] Preparation of the carbon-doped gadolinium oxide: By weight, add 4 parts of sodium hydroxide to 100 parts of deionized water and dissolve it fully. Then, add 6 parts of gadolinium chloride hexahydrate and stir. Stir at a rotation speed of 100 r / min for 18 h, vacuum dry at 110 °C for 8 days, and grind to obtain an intermediate product. Add 6 parts of the intermediate product and 2 parts of citric acid to 120 parts of deionized water, transfer it to a reaction kettle for heating reaction, heat at 190 °C for 8 h, cool to room temperature, dialyze, and freeze-dry to obtain carbon-doped gadolinium oxide.

[0061] Example 3

[0062] This example provides a preparation method of a nickel-titanium alloy material, including the following steps:

[0063] S1: By weight, in an argon atmosphere, first mix 45 parts of nickel powder and 35 parts of titanium powder for the first ball milling treatment (rotation speed: 600 r / min, time: 7 h) to obtain a precursor mixed powder. Then, add 8 parts of carbon-doped gadolinium oxide and 15 parts of additives (9 parts of urea and 6 parts of ammonium bicarbonate) to the precursor mixed powder for the second ball milling treatment (rotation speed: 150 r / min, time: 3 h) to obtain a mixed powder;

[0064] S2: Cold press the mixed powder (pressure: 500 MPa, time: 3 min), demold to obtain a green body, then sinter the green body. The sintering vacuum degree is 4 Pa, the heating rate is 70 °C / min, the sintering temperature is 1000 °C, the sintering holding time is 15 min. After sintering, it is naturally cooled to room temperature in the furnace, and then demolded to obtain alloy A;

[0065] S3: By weight, add 3 parts of graphene oxide to 450 parts of deionized water and disperse evenly by ultrasonic wave, then add 450 parts of 3 mg / mL dopamine hydrochloride buffer solution (dissolve dopamine hydrochloride in Tris-HCl buffer solution) and mix evenly to obtain a co-deposition solution; Pretreat alloy A, polish it with sandpaper, ultrasonically clean it successively with acetone, absolute ethanol, and deionized water, dry it, and then completely immerse it in the co-deposition solution for surface modification. Adjust the pH to 8.6, soak it at 26 °C for 71 h, take it out, wash it with deionized water, and dry it in vacuum to form a composite coating on the surface of alloy A to obtain a nickel-titanium alloy material.

[0066] Preparation of the carbon-doped gadolinium oxide: By weight, add 5 parts of sodium hydroxide to 110 parts of deionized water and dissolve it fully, then add 8 parts of gadolinium chloride hexahydrate and stir. Stir at a speed of 110 r / min for 19 h, vacuum dry at 115 °C for 7 days, and grind to obtain an intermediate product; Add 8 parts of the intermediate product and 3 parts of citric acid to 130 parts of deionized water, transfer it to a reaction kettle for heating reaction, heat at 195 °C for 7 h, cool to room temperature, dialyze, and freeze-dry to obtain carbon-doped gadolinium oxide.

[0067] Comparative Example 1

[0068] This comparative example provides a preparation method of a nickel-titanium alloy material, which is different from Example 1 in that commercially available gadolinium oxide (CAS No. 12064-62-9) is used to replace the carbon-doped gadolinium oxide.

[0069] Comparative Example 2

[0070] This comparative example provides a preparation method of a nickel-titanium alloy material, which is different from Example 1 in that 18 parts of sodium chloride (CAS No. 7647-14-5) is used to replace 18 parts of the additive.

[0071] Comparative Example 3

[0072] This comparative example provides a preparation method of a nickel-titanium alloy material, which is different from Example 1 in that the dosage of urea in the additive is changed to 16 parts and the dosage of ammonium bicarbonate is changed to 2 parts.

[0073] Comparative Example 4

[0074] This comparative example provides a method for preparing a nickel-titanium alloy material, which is different from Example 1 in that: the dosage of urea in the additive is changed to 6 parts and the dosage of ammonium bicarbonate is changed to 12 parts.

[0075] Comparative Example 5

[0076] This comparative example provides a method for preparing a nickel-titanium alloy material, which is different from Example 1 in that: the preparation of the composite coating in step S3 is not carried out.

[0077] The properties of the nickel-titanium alloy materials provided in the above examples and comparative examples were tested, and the test methods are as follows:

[0078] (1) Tensile strength test: The test was carried out according to the requirements of "GB / T 228.1-2021 Metallic materials - Tensile testing - Part 1: Method of test at room temperature".

[0079] (2) Compressive strength test: The test was carried out according to the requirements of "ASTM E9-19 Standard Test Method for Compression Testing of Metallic Materials at Room Temperature".

[0080] (3) Elastic modulus test: The test was carried out according to the requirements of "ASTM E9-19 Standard Test Method for Compression Testing of Metallic Materials at Room Temperature".

[0081] The above performance test data are shown in Table 1.

[0082] Table 1 Performance test results

[0083]

[0084] As can be seen from the above, in the present invention, by selecting urea and ammonium bicarbonate as compound additives, using them in combination with carbon-doped gadolinium oxide, and forming a composite coating on the surface of the sintered alloy, a nickel-titanium alloy material (Examples 1 to 3) is prepared, with a tensile strength of 586 - 591 MPa, a compressive strength of 191 - 198 MPa, and an elastic modulus of 15.8 - 16.5 GPa.

[0085] Compared with Example 1, when commercially available gadolinium oxide (CAS No. 12064-62-9) is used to replace carbon-doped gadolinium oxide, the tensile strength decreases, the compressive strength reduces, and the elastic modulus becomes smaller (Comparative Example 1); compared with Example 1, when 18 parts of sodium chloride (CAS No. 7647-14-5) is used to replace 18 parts of the additive, the tensile strength decreases, the compressive strength reduces, and the elastic modulus becomes smaller (Comparative Example 2); compared with Example 1, when the dosage of urea in the additive is changed to 16 parts and the dosage of ammonium bicarbonate is changed to 2 parts, due to the too small dosage of ammonium bicarbonate, the pore-forming effect is poor, and the small number of pore carriers leads to poor bonding effect, so the tensile strength decreases, the compressive strength reduces, and the elastic modulus becomes smaller (Comparative Example 3); compared with Example 1, when the dosage of urea in the additive is changed to 6 parts and the dosage of ammonium bicarbonate is changed to 12 parts, due to the too small dosage of urea, there are many pore carriers but too little urea, and the bonding with carbon quantum dots is limited, resulting in poor effect, so the tensile strength decreases, the compressive strength reduces, and the elastic modulus becomes smaller (Comparative Example 4); compared with Example 1, when the preparation of the composite coating in step S3 is not carried out, the tensile strength decreases, the compressive strength reduces, and the elastic modulus becomes smaller (Comparative Example 5).

[0086] In summary, the present invention selects urea and ammonium bicarbonate as compound additives, uses them in combination with carbon-doped gadolinium oxide, and forms a composite coating on the surface of the sintered alloy, thereby preparing a nickel-titanium alloy material, effectively improving the tensile strength and compressive strength of the material, and increasing the elastic modulus.

Claims

1. A method for preparing a nickel-titanium alloy material, characterized in that: The following steps are involved: S1: By weight, 40 to 50 parts of nickel powder, 30 to 40 parts of titanium powder, 6 to 10 parts of gadolinium oxide and 12 to 18 parts of additives are mixed to obtain a mixed powder; S2: cold pressing the mixed powder to obtain a green body after demolding, and then sintering the green body to obtain alloy A; S3: In parts by weight, 2 to 4 parts of graphene oxide are added to 400 to 500 parts of deionized water and ultrasonically dispersed evenly, and then 400 to 500 parts of 2 to 4 mg / mL dopamine hydrochloride buffer solution are added and mixed evenly to obtain a co-deposition solution; the alloy A is pretreated and then completely immersed in the co-deposition solution for surface modification to form a composite coating on the surface of the alloy A to obtain a nickel-titanium alloy material.

2. The method for preparing a nickel-titanium alloy material according to claim 1, characterized in that: The mixing treatment conditions in step S1 include: in an argon atmosphere, first mixing nickel powder and titanium powder for a first ball milling treatment (rotation speed of 400 to 800 r / min, time of 6 to 8 hours) to obtain a precursor mixed powder, and then adding gadolinium oxide and additives to the precursor mixed powder for a second ball milling treatment (rotation speed of 100 to 200 r / min, time of 2 to 4 hours).

3. The method for preparing a nickel-titanium alloy material according to claim 1, characterized in that: The sintering conditions in step S2 include: sintering vacuum degree of 2-6 Pa, heating rate of 60-80° C. / min, sintering temperature of 900-1100° C., sintering holding time of 10-20 min, and naturally cooling to room temperature with the furnace after sintering, and demolding.

4. The method for preparing a nickel-titanium alloy material according to claim 1, characterized in that: The pretreatment conditions in step S3 include: sandpaper polishing, ultrasonic cleaning with acetone, anhydrous ethanol, and deionized water in sequence, and drying; The surface modification conditions in step S3 include: adjusting the pH to 8.4-8.8, soaking at 24-28° C. for 70-72 hours, washing with deionized water after taking out, and vacuum drying.

5. The method for preparing a nickel-titanium alloy material according to claim 1, characterized in that: The gadolinium oxide is carbon-doped gadolinium oxide; The preparation method of carbon-doped gadolinium oxide comprises: adding 4 to 6 parts of sodium hydroxide to 100 to 120 parts of deionized water by weight to fully dissolve, then adding 6 to 10 parts of gadolinium chloride hexahydrate for stirring to obtain an intermediate product; adding 6 to 10 parts of the intermediate product and 2 to 4 parts of citric acid to 120 to 140 parts of deionized water, transferring to a reactor for heating reaction, and obtaining carbon-doped gadolinium oxide.

6. The method for preparing a nickel-titanium alloy material according to claim 5, characterized in that: The stirring treatment conditions include: stirring at a speed of 100 to 120 r / min for 18 to 20 hours, vacuum drying at 110 to 120° C. for 6 to 8 days, and grinding.

7. The method for preparing a nickel-titanium alloy material according to claim 5, characterized in that: The conditions of the heating reaction include: heating at 190-200° C. for 6-8 hours, cooling to room temperature, dialysis, and freeze-drying.

8. The method for preparing a nickel-titanium alloy material according to claim 1, characterized in that: The additives are urea and ammonium bicarbonate; the mass ratio of urea to ammonium bicarbonate in the additive is (1-2):

1.

9. A nickel-titanium alloy material, characterized in that: The method is obtained by the preparation method according to any one of claims 1 to 8.

10. Application of the nickel-titanium alloy material obtained by the preparation method according to any one of claims 1 to 8 in a smart ring.

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