A rare earth antibacterial ceramic and its preparation method

Abstract

The present invention discloses a rare earth antibacterial ceramic and a preparation method thereof, belonging to the field of ceramic material technology. The ceramic comprises a base material, a rare earth antibacterial agent, and an auxiliary additive. The base material is coated with a zirconium silicate coating layer; the base material is one of aluminum oxide or zirconium oxide, and the rare earth antibacterial agent is a ternary composite oxide composed of at least three lanthanide elements, wherein the lanthanide elements include Ce, Y, La, and Nd. A preparation method is also provided. Through the collaborative innovation of ternary rare earth composite modification, zirconium silicate interface coating, and gradient sintering technology, the present invention solves the core problems of traditional antibacterial ceramics, such as a single antibacterial spectrum, high-temperature failure, and insufficient durability. The ceramic achieves significant improvements in antibacterial performance, stability, biosafety, and mechanical properties, demonstrating clear technological advancement and industrial application value.

Description

Technical Field

[0001] The present invention relates to the field of ceramic materials, in particular to a rare earth antibacterial ceramic and a preparation method thereof. Background Art

[0002] Traditional antibacterial ceramics mainly achieve their antibacterial function by adding metal ions such as silver, copper, and zinc. However, this type of traditional antibacterial ceramics has many defects. For example, metal ions (such as silver ions) may be toxic to human cells at a certain concentration, and after long-term use, they are released into the environment, causing potential harm to the ecological environment; secondly, the antibacterial spectrum is single and during the high-temperature sintering process of ceramics, antibacterial components such as silver ion compounds are easily decomposed or volatilized, resulting in a significant decrease in the antibacterial performance of the final product. Metal ions also migrate and lose over time during use, especially in a humid or water-contact environment, where the loss rate is accelerated, making it difficult to maintain the antibacterial effect for a long time.

[0003] Based on the above content, combined with the unique 4f electronic structure and surface activity of rare earth elements, which have excellent photocatalytic, antibacterial and stability advantages, a rare earth antibacterial ceramic and its preparation method are proposed. Summary of the Invention

[0004] The purpose of the present invention is to provide a rare earth antibacterial ceramic and a preparation method thereof to solve the problems in the background technology.

[0005] To achieve the above-mentioned purpose, the present invention provides a rare earth antibacterial ceramic, comprising a matrix material, a rare earth antibacterial agent and auxiliary additives, wherein the rare earth antibacterial agent is coated with a zirconium silicate coating layer; the rare earth antibacterial agent is a ternary composite oxide composed of at least three lanthanide elements, and the lanthanide elements include Ce, Y, La, and Nd.

[0006] Preferably, the rare earth antibacterial agent is a Ce / Y / La ternary composite antibacterial agent with a molar ratio of Ce:Y:La=1:0.5~2:0.1~0.5;

[0007] Or the rare earth antibacterial agent is a Ce / Y / Nd ternary composite antibacterial agent, and the molar ratio of Ce:Y:Nd is 1:0.5~2:0.1~0.3.

[0008] Preferably, the matrix material is one of aluminum oxide or zirconium oxide, and the auxiliary additive is nano-titanium dioxide.

[0009] The present invention also provides a method for preparing the rare earth antibacterial ceramic, comprising the following steps:

[0010] S1. Dissolving cerium nitrate, yttrium nitrate, lanthanum nitrate or neodymium nitrate in an ethanol-water mixed solvent, adding citric acid as a complexing agent, and stirring the mixture in a water bath to form a rare earth sol;

[0011] S2. Add a mixed solution of sodium silicate and zirconium oxychloride to the rare earth sol, adjust the pH to 8-9, and stir in a water bath for 45-60 minutes to allow the zirconium silicate to be evenly deposited on the surface of the rare earth particles to form a coating layer;

[0012] S3, ball-milling the base material, nano-titanium dioxide and coated rare earth particles, drying and sieving to obtain a uniform powder;

[0013] S4. The obtained powder is formed into a body by dry pressing or slip casting, and then pre-calcined at 500-600° C. for 30-80 min using microwave-assisted heating;

[0014] S5. Place the pre-fired embryonic body together with a sintering aid in an inert atmosphere for gradient sintering to obtain rare earth antibacterial ceramics.

[0015] Preferably, the matrix material accounts for 70-85wt%, the rare earth antibacterial agent accounts for 5-15wt%, the auxiliary additive accounts for 3-8wt%, the zirconium silicate accounts for 2-5wt%, and the sintering aid accounts for 1-3wt%.

[0016] Preferably, in S1, in the ethanol-water mixed solvent, the volume ratio of ethanol to water is 1-2:1, and the total molar ratio of citric acid to rare earth ions is 1.2-1.5:1.

[0017] Preferably, in S2, the molar ratio of silicon to zirconium in sodium silicate and zirconium oxychloride is 1:1, and the thickness of the coating layer is 10-100 nm.

[0018] Preferably, in S3, the ball milling speed is 200-300 rpm, the ball milling time is 6-12 h, and the drying condition is drying at 80-100° C. for 12-24 h.

[0019] Preferably, in S4, the dry pressing pressure is 50-100 MPa, and the holding time is 5-10 min.

[0020] Preferably, in S5, the sintering aid is magnesium oxide, and the gradient sintering is divided into two stages. In the first stage, the temperature is increased to 1200-1300°C at a heating rate of 5-10°C / min and kept at this temperature for 45-60 minutes.

[0021] In the second stage, the temperature is raised to 1400~1500℃ at a heating rate of 10~20℃ / min and kept at this temperature for 30~45min.

[0022] Therefore, the rare earth antibacterial ceramic and its preparation method of the present invention have the following beneficial effects:

[0023] (1) This invention achieves a technological breakthrough through ternary rare earth synergistic modification and interface structure regulation. + / Y³ + / La³ + (or Nd³ + ) forms a multi-level electronic transition structure, Ce³ + With Y³ + After compounding, "electron-hole pairs" are formed, which can stimulate the generation of reactive oxygen species (ROS) under light or humid environmental conditions, thereby achieving a dual antibacterial mechanism of photocatalysis and ion release; and La³ + The ionic radius and The matrix lattice has a high degree of matching, which can fill the grain boundary vacancies and inhibit the migration of rare earth ions; Nd³ + of The electronic configuration enhances the ability to destroy chitin in fungal cell walls.

[0024] (2) The present invention forms 10-100 nm of rare earth particles on the surface by co-precipitation method. The coating layer forms a chemical bond with the substrate during the sintering process. On the one hand, it isolates the rare earth from direct contact with the high-temperature atmosphere. On the other hand, it serves as an ion release channel to control the release rate of rare earth ions.

[0025] (3) The present invention utilizes microwave-assisted pre-firing to achieve uniform removal of organic matter (citric acid) and avoid the formation of pore defects after sintering; gradient sintering controls the heating rate to promote the uniform distribution of rare earth particles at the grain boundaries, forming a "matrix-grain boundary-rare earth" three-phase synergistic structure, thereby improving the flexural strength of the ceramic.

[0026] The technical solution of the present invention is further described in detail below through examples. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further illustrated by the following examples.

[0028] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0029] Example 1

[0030] Preparation of Ce / Y / La ternary antibacterial ceramics, the raw materials are as follows:

[0031] Matrix material (75wt%): Powder (purity ≥99.5%, particle size 1-2μm);

[0032] Rare earth compound (12wt%): Ce:Y:La=1:1:0.3, cerium nitrate ( , analytically pure);

[0033] Yttrium nitrate ( , analytically pure);

[0034] Lanthanum nitrate ( , analytically pure);

[0035] Auxiliary additives:

[0036] nanometer (Anatase type, particle size 40nm, specific surface area 80m² / g), dosage is 6wt%.

[0037] Zirconium silicate ( , purity ≥99%), used for coating, the dosage is 4wt%.

[0038] Sintering aid: magnesium oxide (MgO, analytical grade, particle size <5 μm), dosage: 3 wt%.

[0039] The specific steps are as follows:

[0040] S1. Add cerium nitrate, yttrium nitrate, and lanthanum nitrate to a beaker containing 200 ml of an ethanol-water mixed solvent (volume ratio of 1.5:1). Add citric acid to the solution and stir evenly. Place the beaker in an 80°C constant temperature water bath and stir at 300 rpm using a magnetic stirrer for 2 hours. Observe the solution state during the reaction until a uniform and transparent rare earth sol is formed.

[0041] S2. Preparation and A mixed solution containing a 1:1 molar ratio of Si to Zr was slowly added dropwise to the rare earth sol. The pH of the system was adjusted to 8.5 with 0.1 mol / L hydrochloric acid. After the addition was complete, the reaction system was placed in a 60°C water bath and stirred at 200 rpm for 50 minutes using a mechanical stirrer. After the reaction, the coated rare earth particles were separated by centrifugation and washed three times with deionized water to remove any surface impurities. Finally, the particles were vacuum dried at 60°C for 12 hours to obtain rare earth particles coated with zirconium silicate.

[0042] S3. The matrix powder was placed in a drying oven at 120°C for 4 hours to remove the adsorbed moisture. Matrix powder, nano , MgO powder and coated rare earth particles are added to a ball mill jar, 300 mL of deionized water is added as the ball milling medium, and zirconia grinding balls are placed. The ball mill is carried out at a speed of 250 rpm on a planetary ball mill for 8 hours. After the ball milling is completed, the slurry is placed in an 80°C drying oven and dried for 24 hours. After the water is completely evaporated, it is ground with a mortar and passed through a 150-mesh sieve to obtain a uniform ceramic powder.

[0043] S4. Use dry pressing to place the powder into a steel mold, apply a pressure of 80 MPa on the press, and maintain the pressure for 8 minutes to form a disc blank with a diameter of 20 mm and a thickness of 5 mm; place the blank in a microwave pre-sintering furnace, set the power to 600 W, and pre-sinter at 550°C for 40 minutes.

[0044] S5. Place the pre-fired body and an appropriate amount of MgO sintering aid into a vacuum tube furnace, introducing high-purity nitrogen (≥99.99%) as a protective atmosphere. A gradient sintering process is employed: in the first stage, heat to 1250°C at a heating rate of 5°C / min and hold for 50 minutes; in the second stage, heat to 1450°C at a heating rate of 10°C / min and hold for 35 minutes. After sintering, cool the sample to room temperature and remove it from the furnace.

[0045] Example 2

[0046] Preparation of Ce / Y / Nd ternary antibacterial ceramics, the raw materials are as follows:

[0047] Matrix material (70wt%): Yttria-stabilized zirconia ( , purity ≥99.8%, particle size 0.5~1μm);

[0048] Rare earth compound (15wt%): Ce:Y:Nd=1:1.5:0.2, cerium nitrate ( , analytically pure);

[0049] Yttrium nitrate ( , analytically pure);

[0050] Neodymium nitrate ( , analytically pure);

[0051] Auxiliary additives:

[0052] nanometer (Anatase type, particle size 30nm, specific surface area 100m² / g), dosage is 5wt%.

[0053] Zirconium silicate ( , purity ≥99%), used for coating, the dosage is 3wt%.

[0054] Sintering aid: magnesium oxide (MgO, analytical grade, particle size <5 μm), dosage: 2 wt%.

[0055] The specific steps are the same as those in Example 1, except that the atmosphere for gradient sintering is replaced with argon atmosphere.

[0056] Comparative Example 1

[0057] Ce / Y binary antibacterial ceramics were prepared using the same raw materials as in Example 1, except that the lanthanum nitrate in the rare earth compound was removed. The specific preparation steps were as follows:

[0058] S1. Dissolve cerium nitrate and yttrium nitrate in 150 mL of ethanol-water mixed solvent (volume ratio 1.5:1), add citric acid (total molar ratio of rare earth ions 1.3:1), and react in a water bath at 80°C for 2 hours to prepare a sol.

[0059] S2. The raw materials and the rare earth sol are ball-milled and mixed. The specific parameters are the same as those in Example 1. After drying and sieving, the mixture is dry-pressed at a pressure of 80 MPa and maintained at this pressure for 8 minutes.

[0060] S3, pre-sintering and sintering process steps are the same as those in Example 1, with the following conditions: microwave-assisted pre-sintering at 550°C for 40 minutes;

[0061] Gradient sintering was performed under nitrogen atmosphere. In the first stage, the temperature was raised to 1250°C at a rate of 5°C / min and kept at this temperature for 50 minutes. In the second stage, the temperature was raised to 1450°C at a rate of 10°C / min and kept at this temperature for 35 minutes.

[0062] Comparative Example 2

[0063] This comparative example uses commercially available traditional silver-based antibacterial ceramics, the main antibacterial component of which is silver-loaded zirconium phosphate.

[0064] Comparative Example 3

[0065] The steps of this comparative example are the same as those of Example 1, except that the zirconium silicate coating step is removed.

[0066] The antibacterial properties of the products in Examples 1-2 and Comparative Examples 1-3 were tested, and the results are shown in Table 1 below.

[0067] Table 1 Antibacterial rate test results

[0068]

[0069] From the above antibacterial properties, it can be seen that the ceramics prepared in the present application have an antibacterial rate against Escherichia coli and Staphylococcus aureus of more than 99.9%, and an antibacterial rate against Candida albicans of ≥99.5%. Compared with the binary system in Comparative Example 1, after the introduction of the third group of rare earth elements (La / Nd), through lattice matching and electronic energy level coupling, the limitation of the traditional binary system that only inhibits bacteria is broken through, and the antibacterial spectrum covers bacteria (Gram negative / positive) and fungi.

[0070] In addition, the high temperature performance test of Example 1 shows that the rare earth loss rate after sintering at 1500℃ is 2.8%; while in Comparative Example 1, the rare earth loss rate after sintering at 1500℃ is 11%, and the product of Comparative Example 2 is sintered at 800℃. The loss rate is 45%, and the loss rate of the product in Comparative Example 3 after sintering at 1500°C is 9%, indicating that the 10-100nm zirconium silicate coating layer prepared by the co-precipitation method of the present invention can form a physical barrier to inhibit the oxidation decomposition and grain boundary migration of rare earths, and the high-temperature stability is improved by 3 times compared with the uncoated sample.

[0071] The flexural strength of the product in Example 1 was tested to be 462 MPa, while that of Comparative Example 2 was only 380 MPa and that of Comparative Example 3 was 420 MPa, indicating that the coating layer formed a chemical bond with the substrate, promoting the uniform distribution of the grain boundaries, and combining with the nanostructured The heterojunction strengthening effect improves the mechanical properties by 25% compared with traditional antibacterial ceramics.

[0072] The ceramics prepared in Examples 1 and 2 were immersed in a hydrochloric acid solution with a pH of 2 for 100 hours, respectively. The antibacterial rates were 96.3% and 96.5%, respectively, and the antibacterial rates remained ≥96%. The ISO10993 cytotoxicity test showed that the L929 cell survival rate was ≥95%, and there was no risk of rare earth ion dissolution toxicity. In the test of Comparative Example 2, the L929 cell survival rate was 85%, indicating that the ternary rare earth system controls the ion release rate through a sustained-release mechanism, avoiding large-scale loss in a short period of time, and the antibacterial durability is increased by more than 2 times.

[0073] In addition, in this embodiment, pre-firing is used to improve the efficiency of the entire process compared to the traditional resistance furnace, and the green body has no organic residual defects. Microwave heating achieves uniform temperature rise of the green body, avoiding pores and cracks caused by local overheating, and providing a densification basis for subsequent sintering.

[0074] Subsequently, the rare earth particles are evenly distributed at the grain boundaries by increasing the temperature in stages. ESR detection shows that the amount of active oxygen generated is 22% higher than that of disordered sintering. Gradient sintering optimizes the distribution of rare earth phases, enhances the synergistic effect of photocatalysis and ion release, and makes the antibacterial mechanism more efficient.

[0075] Therefore, the rare earth antibacterial ceramic and its preparation method of the present invention solve the core problems of traditional antibacterial ceramics such as single antibacterial spectrum, high-temperature failure and insufficient durability through the collaborative innovation of ternary rare earth composite modification, zirconium silicate interface coating and gradient sintering process, and achieve significant improvements in antibacterial performance, stability, biosafety and mechanical properties, and have clear technological progress and industrial application value.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A rare earth antibacterial ceramic, characterized by: The invention comprises a base material, a rare earth antibacterial agent and auxiliary additives, wherein the rare earth antibacterial agent is coated with a zirconium silicate coating layer; the rare earth antibacterial agent is a Ce / Y / La ternary composite antibacterial agent, and the molar ratio of Ce:Y:La is 1:0.5-2:0.1-0.5; Or the rare earth antibacterial agent is a Ce / Y / Nd ternary composite antibacterial agent with a molar ratio of Ce:Y:Nd=1:0.5~2:0.1~0.3; The matrix material is one of aluminum oxide or zirconium oxide, and the auxiliary additive is nano titanium dioxide; The preparation method of rare earth antibacterial ceramics comprises the following steps: S1. Dissolving cerium nitrate, yttrium nitrate, lanthanum nitrate or cerium nitrate, yttrium nitrate, or neodymium nitrate in an ethanol-water mixed solvent, adding citric acid as a complexing agent, and stirring the mixture in a water bath to form a rare earth sol; S2. Add a mixed solution of sodium silicate and zirconium oxychloride to the rare earth sol, adjust the pH to 8-9, and stir in a water bath for 45-60 minutes to allow the zirconium silicate to be evenly deposited on the surface of the rare earth particles to form a coating layer; S3, ball-milling the base material, nano-titanium dioxide and coated rare earth particles, drying and sieving to obtain a uniform powder; S4. The obtained powder is formed into a body by dry pressing or slip casting, and then pre-calcined at 500-600° C. for 30-80 min using microwave-assisted heating; S5. Place the pre-fired embryonic body together with a sintering aid in an inert atmosphere for gradient sintering to obtain rare earth antibacterial ceramics.

2. The rare earth antibacterial ceramic according to claim 1, characterized in that: The base material accounts for 70-85wt%, the rare earth antibacterial agent accounts for 5-15wt%, the auxiliary additive accounts for 3-8wt%, the zirconium silicate accounts for 2-5wt%, and the sintering aid accounts for 1-3wt%.

3. The rare earth antibacterial ceramic according to claim 1, characterized in that: In S1, in the ethanol-water mixed solvent, the volume ratio of ethanol to water is 1-2:1, and the total molar ratio of citric acid to rare earth ions is 1.2-1.5:

1.

4. The rare earth antibacterial ceramic according to claim 1, characterized in that: In the S2, the molar ratio of silicon to zirconium in sodium silicate and zirconium oxychloride is 1:1, and the thickness of the coating layer is 10-100 nm.

5. The rare earth antibacterial ceramic according to claim 1, characterized in that: In S3, the ball milling speed is 200-300 rpm, the ball milling time is 6-12 h, and the drying condition is drying at 80-100° C. for 12-24 h.

6. The rare earth antibacterial ceramic according to claim 1, characterized in that: In S4, the dry pressing pressure is 50-100 MPa, and the holding time is 5-10 min.

7. The rare earth antibacterial ceramic according to claim 1, characterized in that: In the S5, the sintering aid is magnesium oxide, and the gradient sintering is divided into two stages. In the first stage, the temperature is increased to 1200-1300°C at a heating rate of 5-10°C / min and kept at this temperature for 45-60 minutes. In the second stage, the temperature is raised to 1400~1500℃ at a heating rate of 10~20℃ / min and kept at this temperature for 30~45min.

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