A nitride nanosheet reinforced zinc alloy composite material and its preparation method

Abstract

This invention relates to a nitride nanosheet-reinforced zinc alloy composite material and its preparation method. The material comprises zinc metal and nanosheets; the mass fraction of the nanosheets in the material is 2.5% to 15%; the zinc metal is zinc or a zinc alloy, the zinc alloy is a ZnM alloy, and the metal M is one or more of aluminum, silver, copper, manganese, nickel, titanium, chromium, and cobalt. The preparation method employs ultrasonic-assisted casting and hot rolling, utilizing the influence of nanosheets on metal grain growth to further refine and strengthen the grains, thereby significantly improving the mechanical properties of the zinc metal. This invention has the advantages of simple process, convenient operation, and excellent mechanical properties and biocompatibility of the prepared composite material.

Description

Technical Field

[0001] This invention relates to a nitride nanosheet-reinforced zinc alloy composite material and its preparation method, which is generally applied in the field of biodegradable zinc-based metal biomedical devices, including bioresorbable vascular stents, bioresorbable ureteral stents, biodegradable bone implants with adjustable modulus, guiding bone formation membranes, bioresorbable dental membranes and other biomedical implants. Background Technology

[0002] In the biomedical field, traditional biomaterials made of metals (such as stainless steel, titanium alloys, and zirconium alloys) have been widely used clinically. However, they have some significant drawbacks. The main issue is that existing clinically used biomaterials are inert and cannot degrade, requiring removal after the affected area has healed. Therefore, in recent years, novel biodegradable metallic materials have been developed, including magnesium-based alloys, zinc-based alloys, and iron-based alloys. While magnesium-based materials can degrade and be eliminated from the body through the kidneys, the rapid degradation of magnesium can raise the pH level in the affected area, potentially inducing inflammation. Furthermore, the degradation process generates hydrogen gas, posing a risk of air pocket formation. Although iron-based metals can degrade, their degradation in vivo is slow. Therefore, zinc-based alloys are an ideal material for bioresorbable metallic implants.

[0003] As a crucial element in biological functions, zinc participates in many regulation processes of proliferation, differentiation, and apoptosis, and is involved in nucleic acid metabolism, signal transduction, and gene expression. Furthermore, zinc implants exhibit stable corrosion rates without causing severe inflammation, platelet aggregation, platelet formation, or intimal hyperplasia. However, the mechanical strength of pure zinc is unsuitable for load-bearing. While alloying can improve the mechanical strength of zinc metal, the presence of its alloy phase can lead to high degradation rates, making it unsuitable for internal implantation.

[0004] Currently, there are many patents for improving the properties of zinc alloys. For example, patent CN109500396B provides a method for preparing a bio-zinc alloy with intragranular-intergranular composite reinforcement, which uses cryogenic ball milling and selective laser cladding to achieve uniform distribution of nano-ceramic particles within and between the zinc matrix. This method mainly utilizes the characteristic of aluminum titanium nitride decomposing to release aluminum at high temperatures, achieving aluminum enrichment at the interface between aluminum titanium nitride and the zinc matrix, enhancing the interfacial bonding between aluminum titanium nitride and the zinc matrix, thereby enhancing the mechanical properties of the zinc alloy. Patent CN114717447A provides an ultrafine-grained biodegradable zinc alloy, its preparation method, and applications. It mainly refines the zinc alloy grains to the micron level through alloying and hot rolling, thereby optimizing the microstructure of the zinc alloy and significantly improving the mechanical strength and toughness of the alloy through a fine-grain strengthening mechanism. Although the above patents can improve the mechanical properties of zinc alloys to a certain extent, the operation is relatively complex. While they can improve the mechanical strength of zinc alloys, they do not significantly change their biocompatibility. Biocompatibility is a key performance characteristic for the application of biodegradable zinc alloys in the biomedical field. Summary of the Invention

[0005] The purpose of this invention is to address the problems of insufficient mechanical strength, excessively high degradation rate, and generally poor biocompatibility in current biodegradable zinc alloys by providing a nitride nanosheet-reinforced zinc alloy composite material and its preparation method. This method primarily employs ultrasonic-assisted casting and hot rolling. By adding nitride nanosheets to the zinc matrix, the nanosheets influence metal grain growth, further refining and strengthening the grains, thus significantly improving the mechanical properties of zinc metal while minimizing its impact on degradation performance. Furthermore, the addition of nitride nanosheets also enhances the biocompatibility of the metal, promoting osteogenic differentiation and tissue regeneration. This invention offers advantages such as simple process, convenient operation, and excellent performance of the prepared composite material in terms of mechanical properties and biocompatibility.

[0006] The technical solution of this invention is as follows:

[0007] A nitride nanosheet-reinforced zinc alloy composite material, comprising zinc metal and nanosheets; wherein the mass fraction of nanosheets in the material is 2.5% to 15%;

[0008] The zinc metal is zinc or a zinc alloy, the zinc alloy is a ZnM alloy, and the metal M is one or more of aluminum (Al), silver (Ag), copper (Cu), manganese (Mn), nickel (Ni), titanium (Ti), chromium (Cr), and cobalt (Co);

[0009] The mass percentage of M is 0.1%-3%;

[0010] The nanosheets have a diameter of 30nm-180nm and a thickness of 3-50nm.

[0011] The nanosheets include one or more of metal nitrides and non-metal nitrides.

[0012] The nanosheets are specifically one or more of lithium nitride (Li3N), magnesium nitride (Mg3N2), aluminum nitride (AlN), titanium nitride (TiN), tantalum nitride (TaN), boron nitride (BN), phosphorus pentazonide (P3N5), and silicon tetranitride (Si3N4).

[0013] The method for preparing the nitride nanosheet reinforced zinc alloy composite material includes the following preparation steps:

[0014] (1) Weigh out the zinc metal raw material and nitride raw material according to the design ratio;

[0015] (2) Potassium aluminum fluoride (KAlF4) is mixed with nanosheets; wherein potassium aluminum fluoride accounts for 0.05%-0.2% of the mass fraction of the nitride nanosheets;

[0016] (3) Under the protection of inert gas, pure zinc ingots are first melted in a graphite crucible at 600-900℃; then a mixture of potassium aluminum fluoride (KAlF4) and nanosheets is added, and then the mixture is mechanically stirred for 0.5-2h to add molten zinc.

[0017] (4) Cover the surface of the stirred molten zinc with a mixture of sodium chloride and potassium chloride, and then use an ultrasonic processor to break up the agglomerated nanoparticles for 0.5-3 hours with an ultrasonic assisted method (500-3000W, 20KHz). Pour the melt into a mold and obtain the composite metal after cooling.

[0018] When the zinc metal is a zinc alloy, the following steps are also required: After the ultrasonic processor, add a ZnM intermediate metal containing the designed amount of M to the melt. At this time, the melting temperature is 600-900℃, and mechanically stir for 0.5-2 hours. Then pour the melt into a mold for cooling to obtain the composite metal.

[0019] The volume of the mixture of sodium chloride and potassium chloride added is 2%-4% of the volume of zinc metal (the mixture of sodium chloride and potassium chloride is mainly to isolate the zinc alloy from air and prevent oxidation; due to their different densities, they float on the surface of the molten metal).

[0020] (5) The composite metal obtained by casting is rolled at a temperature of 200℃-550℃, the rolling pressure is 1KN-30KN, the rolling speed is 1-50mm / min, and the rolling deformation is 60-80%, finally obtaining nitride nanosheet reinforced zinc alloy composite material.

[0021] The inert gas used in the above preparation method is a mixture of 99% argon and 1% sulfur hexafluoride gas under protection.

[0022] The essential features of this invention are:

[0023] This invention significantly improves the mechanical properties of zinc metal by incorporating nitride nanosheets into a zinc matrix. The nanosheets influence metal grain growth, further refining and strengthening the grains. The choice of nitride nanosheet type, diameter, and mass fraction significantly affects the mechanical strength and degradation resistance of the prepared zinc alloy, thus influencing its biocompatibility. Experiments show that a nanosheet-to-zinc mass ratio of 2.5%-15% allows for high wettability and automatic fusion of the nanosheets during zinc casting, resulting in more uniform dispersion in the molten metal and stable performance. Nanosheets with a diameter greater than 180 nm negatively impact the mechanical properties of the composite material, while those smaller than 30 nm can negatively affect zinc degradation within its microstructure. A mass fraction below 2.5% does not effectively alter the mechanical properties of the composite material, while a mass fraction above 15% affects the dispersibility of the nanosheets in the zinc matrix, reducing the material's mechanical properties.

[0024] The beneficial effects of this invention are as follows:

[0025] This invention utilizes an ultrasonic stirring-assisted casting and rolling method to uniformly disperse nitride nanosheets into a zinc alloy matrix, ensuring the nanosheets are aligned with the metal grain orientation. This results in the preparation of a nitride nanosheet-reinforced zinc alloy composite material, as detailed below:

[0026] (1) Adjustable elastic modulus. The present invention provides a nano-nitride reinforced zinc alloy composite material prepared by ultrasound assistance. The elastic modulus of the matrix can be changed by adjusting the size of the nanosheets and the content of the added nanosheets, so that the elastic modulus of the zinc alloy can be adjusted. This is very significant in the field of biodegradable biomaterials, especially in the application of bone implants, where it can match the modulus of local bone materials to achieve a more ideal therapeutic effect.

[0027] (2) Improved Mechanical Properties. This invention presents a nitride nanosheet-reinforced zinc alloy composite material prepared with ultrasonic assistance. By adding well-dispersed nitride nanosheets, the nanosheets are uniformly present between the grains and aligned with the grain growth orientation, hindering dislocation movement and limiting grain growth, thus achieving effective strengthening. Under optimal parameters, the composite material exhibits a yield strength of 132 MPa and a tensile strength of 168 MPa. Compared to the yield strength (48 MPa) and tensile strength (68 MPa) of pure zinc produced using the same process, these represent increases of 175% and 147%, respectively.

[0028] (3) Improved creep, hardness, and fatigue resistance. This invention provides a nitride nanosheet-reinforced zinc alloy composite material prepared with ultrasonic assistance. The added nanostructure can reduce the effective stress on the matrix and improve the fatigue life of the zinc-containing matrix. The high hardness of the nanosheets themselves can be combined with the hardness of the zinc-based material, thereby further improving the hardness of the matrix. Compared with the 41HV of pure zinc, the hardness of the material prepared by this invention is 58HV, which is 41.46% higher.

[0029] (4) Reducing the size of intermetallic phases in zinc alloys: Dispersed nanosheets can inhibit the growth of intermetallic phases during solidification and control grain growth. The reduction in grain size ultimately improves the ductility of zinc alloys. The grain size of pure zinc decreased from the initial 18.3 μm to 5.8 μm, a reduction of 68.31%. Ductility increased by 1.7%, compared to 1.2% for pure zinc, representing a 41.67% improvement.

[0030] (5) Maintaining good biocompatibility and moderate corrosion rate of zinc. The present invention provides a nitride nanosheet-reinforced zinc alloy composite material prepared by ultrasound assistance. The dispersed nanosheets have high reaction stability and thermal stability. The zinc-based material, including the nanostructure, does not reduce the loss of biocompatibility or the increase in biocorrosion rate.

[0031] (6) Good imaging performance. The present invention provides a nano-nitride reinforced zinc alloy composite material prepared by ultrasound assistance. The dispersed nitride nanosheets are non-magnetic, which allows for magnetic resonance imaging examination of soft tissue near nitride implants without artifacts. Attached Figure Description

[0032] Figure 1 This is a flowchart of a method for preparing a nano-nitride reinforced zinc alloy composite material according to the present invention;

[0033] Figure 2 A comparison of the mechanical properties of the nano-nitride reinforced zinc alloy composites obtained in Examples 1 and 2;

[0034] Figure 3 This is a comparison chart of the Vickers hardness of the nano-nitride reinforced zinc alloy composites obtained in Examples 1 and 2;

[0035] Figure 4 This is a comparison of the corrosion rates of the nano-nitride reinforced zinc alloy composites obtained in Examples 1 and 2.

[0036] Figure 5 This is a comparison diagram of the grain size of the nano-nitride reinforced zinc alloy composites obtained in Examples 1 and 2;

[0037] Figure 6 The image shows a comparison of cell activity of the nano-nitride reinforced zinc alloy composites obtained in Examples 1 and 2. Detailed Implementation

[0038] The present invention will be further described in detail below through specific embodiments.

[0039] Example 1

[0040] Preparation and performance testing of Zn-Si4N3 nanocomposites.

[0041] The testing method used in this embodiment is as follows:

[0042] Mechanical testing: A universal tensile testing machine was used. Specific experimental parameters and sample dimensions conformed to the national standard GB / T228.1-2010.

[0043] Vickers hardness: The test was conducted using an HMV-2T hardness tester. The automatic loading time was 15 seconds, and the load was HV0.2 (1.9 N).

[0044] In vitro corrosion: The corrosion rate was achieved using a thin slice with a sample diameter of 10 mm and a thickness of 2 mm in simulated body fluid, following the specific requirements of the national standard GB / T 16886.

[0045] Grain size: Images were taken using a DM2700 metallographic microscope and statistically analyzed using ImageJ software.

[0046] Cytotoxicity test: Performed using an extract method, with the extract in a 1.25cm solution. 2 Extraction was performed using a ratio of 1 mL surface area to DMEM solution volume, followed by filtration through a filter membrane. Serum was then added to prepare the extract for cell culture. MC3T3-E1 cells were used, and the culture medium was changed every other day. Cell viability was tested after 7 days of culture.

[0047] 1) Weigh out the zinc metal raw material and the nitride raw material respectively. The metal raw material includes pure zinc (purity of 99.99%). The composite material prepared in this embodiment uses pure zinc ingots with a mass fraction of 96.9% and Si4N3 nanosheets with a mass fraction of 3.1%, a diameter of about 30nm, and a thickness of 10nm.

[0048] 2) Mix silicon nitride (Si4N3) and potassium aluminum fluoride (KAlF4) at a mass ratio of 0.05% to silicon nitride to obtain a mixture. The powder mixture is mixed by mechanical shaking at about 300 rpm for about 30 min.

[0049] 3) Under the protection of an inert gas atmosphere, high-purity zinc ingots are melted in a graphite crucible at 600°C. Then, a mixture of potassium aluminum fluoride and silicon nitride is added. The molten potassium aluminum fluoride is used to assist in the incorporation of silicon nitride particles. After that, the mixture is mechanically stirred for 0.5 hours before being added to the molten zinc.

[0050] 4) Auxiliary ultrasonic treatment was performed using a JY-R202G ultrasonic device. The ultrasonic processor (1000W, 20KHz) was used to treat the agglomerated silicon nitride particles for 1 hour to break them up and disperse them evenly. A salt mixture (a mixture of sodium chloride and potassium chloride in a 1:1 ratio) was added. The volume of the salt mixture was 3% of the volume of the added pure zinc melt to protect the zinc alloy melt from oxidation. The melt was then poured into a mold and allowed to cool naturally to obtain an ingot.

[0051] 5) The cast metal prepared in the previous step is rolled at a temperature of 300℃, with the sample taken perpendicular to the casting mold wall, and a pressure of 10KN. The rolling speed is 10mm / min, and the rolling deformation is 70%. During the rolling process, the nanosheets uniformly distributed in the alloy play a role in "pinning" the grain boundaries, inhibiting the growth of alloy grains, making the grains more refined, and achieving the purpose of improving mechanical strength.

[0052] 6) The rolled material is cut for subsequent mechanical, composition, and biocompatibility tests.

[0053] After testing, such as Figure 2 As shown, the mechanical strength of zinc metal with the addition of approximately 3.1% by mass of Si4N3 nanosheets with a diameter of approximately 30 nm and a thickness of 10 nm was improved, with a yield strength of 96 MPa and a tensile strength of 110 MPa. This is mainly due to the pinning effect of the nanosheets on the grain growth of the alloy, thereby improving the mechanical strength. Figure 3 As shown, the hardness of the metal after adding nanosheets is 52 HV, which is a certain improvement. This is mainly due to the high strength of the silicon nitride nanosheets themselves, which also increases the hardness of zinc metal. Figure 4As shown, the corrosion rate of the metal with added nanosheets was not significantly increased, and the corrosion rate after 14 days was 3.75 μg / mm. 2 The difference between the added nanosheets and the unadded nanosheets is not significant, mainly because the content of the added nanosheets is moderate, and the size of the nanosheets is optimized and uniformly distributed, thus having little impact on their degradation ability. Figure 5 The cell viability of zinc metal with added silicon nitride nanosheets was 94%, which was improved compared with the unadded zinc metal. This was mainly due to the fact that the nitrides released during the zinc metal degradation process have good biocompatibility and can promote cell proliferation.

[0054] Example 2

[0055] The testing methods used in this embodiment are the same as those in Embodiment 1.

[0056] The difference between this comparative example and Example 1 is step 1, in which zinc metal raw material and silicon nitride (Si4N3) raw material are weighed separately. The metal raw material includes pure zinc ingots (purity of 99.99%). The composite material prepared in this example uses pure zinc ingots with a mass fraction of 94.7% and Si4N3 nanosheets with a mass fraction of approximately 5.3%, a diameter of approximately 30 nm, and a thickness of 10 nm. Subsequent processes are the same as in Example 1.

[0057] After testing, such as Figure 2 As shown, the mechanical strength of zinc metal with the addition of approximately 5.3% by mass of Si4N3 nanosheets with a diameter of approximately 30 nm and a thickness of 10 nm was improved, with a yield strength of 132 MPa and a tensile strength of 168 MPa. This is mainly due to the better pinning effect of the added nanosheets on the grain growth of the alloy, further improving the mechanical strength. Figure 3 As shown, the hardness of the metal after adding nanosheets is 58 HV, which is a certain improvement. This is mainly due to the high strength of the uniformly distributed silicon nitride nanosheets, which also improve the hardness of zinc metal. Figure 4 As shown, the corrosion rate of the metal with added nanosheets was not significantly increased, and the corrosion rate after 14 days was 3.7 μg / mm. 2 The degradation rate is not significantly different from that of metals without added nanosheets, mainly because the content of added nanosheets is moderate, and the size of the nanosheets is optimized and evenly distributed, so it has little impact on the degradation ability. However, increasing the content will affect the degradation performance, so the degradation rate is slightly higher than that of composite metals with only 3.1% added nanosheets. Figure 5The zinc metal with added silicon nitride nanosheets showed a cell activity of 93%, which was improved compared to the unadded material. Compared to the composite material with 3.1% silicon nitride nanosheets, its bioactivity was slightly lower due to the decreased degradation rate. This is mainly because the addition of nanosheets altered the overall microstructure of the material, slowing down the degradation rate and reducing the release of active particles, thus resulting in slightly lower bioactivity than the material with 3.1% silicon nitride nanosheets. Overall, the added nanosheets maximized the pinning site effect, further improving the material's hardness and mechanical strength.

[0058] Example 3

[0059] Preparation of titanium nitride / aluminum nitride nano-zinc metal composite materials.

[0060] The testing methods used in this embodiment are the same as those in Embodiment 1.

[0061] 1) Weigh out the zinc metal raw material and the nitride raw material separately. The metal raw material includes pure zinc (purity 99.99%). The composite material prepared in this embodiment consists of 95% pure zinc ingot by mass and approximately 5% titanium nitride / aluminum nitride mixture nanosheets with a diameter of approximately 50 nm and a thickness of 14 nm by mass. The mass ratio of titanium nitride to aluminum nitride in the mixture is 2:1.

[0062] 2) Mix the mixture of titanium nitride and lithium nitride with potassium aluminum fluoride at a mass fraction of 0.05% of the nitride nanosheets to obtain a mixture. The powder mixture is mixed on a mechanical shaker at about 300 rpm for about 30 min.

[0063] 3) Under the protection of an inert gas atmosphere, high-purity zinc ingots are melted in a graphite crucible at 650°C. Then, a mixture of potassium aluminum fluoride and titanium aluminum nitride is added. The molten potassium aluminum fluoride is used to assist in the incorporation of titanium aluminum nitride. After that, the mixture is mechanically stirred for 1 hour before being added to the molten zinc.

[0064] 4) Auxiliary ultrasonic treatment was performed using a JY-R202G ultrasonic device. The ultrasonic processor (2000W, 20KHz) was used to treat the agglomerated titanium nitride / aluminum nitride particles for 1.5 hours to break up the particles and to uniformly disperse them. A mixture of sodium chloride and potassium chloride in a 1:1 ratio was added at a concentration of 4% of the volume of the added pure zinc melt to protect the zinc alloy melt from oxidation. The melt was then poured into a mold to cool.

[0065] 5) The prepared cast metal is rolled at a temperature of 350℃, with the sample taken perpendicular to the casting mold wall, and a pressure of 15KN at a speed of 0.5mm / min. The rolling deformation is 75%. The nanosheets in the sample are used to refine the grains and improve the mechanical strength.

[0066] 6) The rolled material is cut for subsequent mechanical, composition, and biocompatibility tests.

[0067] Example 4

[0068] Preparation of titanium nitride / aluminum nitride / magnesium nitride nano-zinc metal composite materials.

[0069] The testing methods used in this embodiment are the same as those in Embodiment 1.

[0070] 1) Weigh out the zinc metal raw material and the nitride raw material separately. The metal raw material includes pure zinc (purity of 99.99%). The composite material prepared in this embodiment uses 95% pure zinc ingots by mass and 5% titanium nitride / aluminum nitride / magnesium nitride mixed nanosheets with a diameter of 50 nm and a thickness of 8 nm by mass. The ratio of the three nitrides is 4:2:1.

[0071] 2) Mix the mixture of titanium nitride / aluminum nitride / magnesium nitride and 0.1% potassium aluminum fluoride by mass of nitride nanosheets to obtain a mixture. The powder mixture is mixed on a mechanical shaker at about 300 rpm for about 30 min.

[0072] 3) Under the protection of an inert gas atmosphere, high-purity zinc ingots are melted in a graphite crucible at 700°C. Then, potassium aluminum fluoride and a mixture of titanium nitride / aluminum nitride / magnesium nitride are added. The molten potassium aluminum fluoride is used to assist in the incorporation of titanium nitride / aluminum nitride / magnesium nitride, and then the mixture is added to the molten zinc through mechanical stirring.

[0073] 4) Use JY-R202G ultrasonic equipment for ultrasonic treatment. Use an ultrasonic processor (2500W, 20KHz) for 2 hours to break up the agglomerated titanium nitride / aluminum nitride / magnesium nitride particles to uniformly disperse the titanium nitride / aluminum nitride / magnesium nitride particles. Add a mixture of sodium chloride and potassium chloride in a 1:1 ratio at a content of 3% of the volume of the added pure zinc melt to protect the zinc melt from oxidation. Then pour the melt into a mold.

[0074] 5) The prepared cast metal is rolled at a temperature of 350℃, with the rolling sample taken perpendicular to the casting mold wall, and a pressure of 10KN at a speed of 0.3mm / min. The rolling deformation is 75%, which achieves the purpose of improving mechanical strength.

[0075] 6) Cut the rolled material into samples of suitable size for subsequent mechanical, composition, and biocompatibility tests.

[0076] Example 5

[0077] The testing methods used in this embodiment are the same as those in Embodiment 1.

[0078] This embodiment differs from Embodiment 1 in steps 1 and 4. In step 1, pure zinc, zinc-magnesium master alloy raw materials, and nitride raw materials are weighed out, with the ratio of pure zinc to zinc-magnesium master alloy being 1:1. The zinc-magnesium alloy contains 98% zinc and 2% magnesium. In step 4, before casting into the steel mold, zinc master alloy (at a 1:1 weight ratio to pure zinc) is added to the crucible, and then the uniformly mixed melt is poured into the mold for cooling. Subsequent processes are the same as in Embodiment 1.

[0079] Example 6

[0080] The testing methods used in this embodiment are the same as those in Embodiment 1.

[0081] The difference between this embodiment and Embodiment 3 lies in steps 1 and 4. In step 1, zinc metal raw material and nitride raw material are weighed out, as are pure zinc, zinc-magnesium master alloy raw material, and nitride raw material. The ratio of pure zinc to zinc-magnesium master alloy is 1:1, and the zinc content in the zinc-magnesium alloy is 98% and the magnesium content is 2%. In step 4, before casting into the steel mold, a zinc-magnesium alloy with a 1:1 ratio to pure zinc is added to the crucible, and then the uniformly mixed melt is poured into the mold for cooling. Subsequent processes are the same as in Embodiment 3.

[0082] Example 7

[0083] The testing methods used in this embodiment are the same as those in Embodiment 1.

[0084] This embodiment differs from Embodiment 1 in steps 1 and 4. In step 1, pure zinc, zinc-lithium master alloy raw materials, and nitride raw materials are weighed out, with the ratio of pure zinc to zinc-lithium master alloy being 1:1. The zinc-lithium alloy contains 98% zinc and 2% lithium. In step 4, before casting into the steel mold, an appropriate amount of zinc-lithium master alloy (1:1 weight ratio) is added to the crucible, and then the melt is poured into the mold. Subsequent processes are the same as in Embodiment 1.

[0085] As can be seen from the above embodiments and comparative examples, the present invention uses nitride nanosheets with a mass fraction of about 2.5% to 15%, a diameter of 30 to 180 nm, and a thickness of 3-50 nm, which can be uniformly distributed in a zinc metal solution under ultrasonic assistance. Then, by hot rolling the ingot, the uniformly distributed nitride nanosheets are uniformly distributed in the intergranular space of the zinc alloy, which hinders grain growth and achieves the purpose of improving strength.

[0086] The composite zinc alloy is composed of nitride nanosheets and a zinc matrix. The microstructure of the nanonitrides consists of nanosheets with a diameter of 30 to 180 nm, and the mass fraction of the nitride nanosheets in the composite material is approximately 2.5% to 15%. The nitride nanosheets exist in the intergranular spaces during the zinc alloy casting process, and then, through rolling, achieve a uniform distribution of the nanosheets within the zinc matrix grains. Furthermore, they pin the zinc grains, hindering their growth and improving mechanical strength. In this invention, the diameter of the nanosheets is approximately 30 to 180 nm, and the mass fraction is 2.5% to 15%. Nanosheets that are too large or too small will not achieve the desired effect. Excessively large nanosheets will affect the mechanical properties of the composite material manufactured in this invention, while excessively small diameters will affect the degradation behavior of zinc metal. A mass fraction below 2.5% cannot effectively change the mechanical properties of the composite material of this invention, while a mass fraction above 15% will affect the dispersion of the nanosheets in the zinc matrix, reducing the mechanical properties of the material. This invention also utilizes nanosheets of optimized size to achieve high wettability with zinc metal during casting, enabling automatic fusion. The entire process employs a stirring casting and rolling method for zinc, incorporating molten salt-assisted ultrasound during casting. The microbubbles generated by the ultrasound create shock waves that prevent nanosheet aggregation, promoting uniform dispersion of the nanosheets in the molten metal and maintaining good mechanical strength and a stable degradation rate in the zinc composite material. Because nitrides themselves possess high fracture toughness, high strength, high temperature resistance, and low wear properties, they also enhance the relevant properties of the zinc alloy. During the zinc metal degradation process, the released nitrides exhibit good biocompatibility, promoting cell adhesion, proliferation, and differentiation. Furthermore, the non-magnetic nature of nitrides allows for magnetic resonance imaging (MRI) examination of soft tissue near nitride-based implants without artifacts.

[0087] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

[0088] Matters not covered in this invention are common knowledge.

Claims

1. A zinc alloy composite material reinforced with nitride nanosheets, characterized in that... The material comprises zinc metal and nanosheets; the mass fraction of nanosheets in the material ranges from 2.5% to 15%. The zinc metal is zinc or a zinc alloy, the zinc alloy is a ZnM alloy, and the metal M is one or more of aluminum, silver, copper, manganese, nickel, titanium, chromium, and cobalt. The nanosheets have a diameter of 30 nm-180 nm and a thickness of 3-50 nm. The nanosheets include one or more of metal nitrides and non-metal nitrides; The nanosheets are specifically one or more of lithium nitride, magnesium nitride, aluminum nitride, titanium nitride, tantalum nitride, boron nitride, triphosphorus pentanitride, and trisilicon tetranitride; The mass percentage of M is 0.1%-3%; The preparation method of the nitride nanosheet reinforced zinc alloy composite material includes the following preparation steps: (1) Weigh out the zinc metal raw material and nitride raw material according to the design ratio; (2) Mix potassium aluminum fluoride with nanosheets; wherein the potassium aluminum fluoride accounts for 0.05%-0.2% of the mass fraction of the nitride nanosheets; (3) Under the protection of an inert gas, pure zinc ingots are first melted in a graphite crucible at 600-900℃; then a mixture of potassium aluminum fluoride (KAlF4) and nanosheets is added, and then the mixture is mechanically stirred for 0.5-2h to add molten zinc. (4) Cover the surface of the stirred molten zinc with a mixture of sodium chloride and potassium chloride, and then use ultrasound to break up the agglomerated nanoparticles for 0.5-3 hours. Then pour the melt into a mold and cool it to obtain the composite metal. (5) The composite metal obtained by casting is rolled at a temperature of 200℃-550℃, the rolling pressure is 1KN-30KN, the rolling speed is 1-50 mm / min, the rolling deformation is 60-80%, and finally the nitride nanosheet reinforced zinc alloy composite material is obtained. When the zinc metal is a zinc alloy, the following steps are required: After the ultrasonic processor, add a ZnM intermediate metal containing the designed amount of M to the melt. At this time, the melting temperature is 600-900℃, and mechanically stir for 0.5-2 hours. Then pour the melt into a mold for cooling to obtain the composite metal.

2. The nitride nanosheet reinforced zinc alloy composite material as described in claim 1, characterized in that, In the preparation method, the inert gas used is a mixture of 99% argon and 1% sulfur hexafluoride gas under protection.

3. The nitride nanosheet reinforced zinc alloy composite material as described in claim 1, characterized in that, In the preparation method, the volume of the mixture of sodium chloride and potassium chloride added is 2%-4% of the volume of zinc metal.

4. The nitride nanosheet reinforced zinc alloy composite material as described in claim 1, characterized in that, In the preparation method, the ultrasonic processor used in the ultrasonic-assisted process is 500-3000W, 20KHz.

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