阅读说明：本技术 一种梯度多孔生物活性陶瓷涂层材料及其制备方法 (Gradient porous bioactive ceramic coating material and preparation method thereof ) 是由 刘德福 邓子鑫 潘治贵 米航彪 于 2021-07-30 设计创作，主要内容包括：本发明公开了一种梯度多孔生物活性陶瓷涂层材料及其制备方法,该涂层材料包括钛基体和覆在钛基体表面的梯度多孔生物活性陶瓷涂层,梯度多孔生物活性陶瓷涂层从内至外,依次包括Ag阻挡层、羟基磷灰石/Ag复合过渡层、羟基磷灰石生物陶瓷层,羟基磷灰石生物陶瓷层为多孔结构。该梯度多孔生物活性陶瓷涂层材料中的羟基磷灰石生物陶瓷层具有多孔结构,涂层材料表面与宿主骨组织在结构上十分相似,具有更好的生物学性能；涂层材料表面的孔隙有助于蛋白质吸收和成骨细胞附着,也有助于体液环境中的离子交换、降解和HA沉积,对新生骨的形成以及良好的骨性结合有促进作用。(The invention discloses a gradient porous bioactive ceramic coating material and a preparation method thereof, the coating material comprises a titanium substrate and a gradient porous bioactive ceramic coating covering the surface of the titanium substrate, the gradient porous bioactive ceramic coating sequentially comprises an Ag barrier layer, a hydroxyapatite/Ag composite transition layer and a hydroxyapatite bioceramic layer from inside to outside, and the hydroxyapatite bioceramic layer is of a porous structure. The hydroxyapatite biological ceramic layer in the gradient porous biological active ceramic coating material has a porous structure, and the surface of the coating material is very similar to the structure of host bone tissues, so that the coating material has better biological performance; the pores on the surface of the coating material are beneficial to protein absorption and osteoblast attachment, and also beneficial to ion exchange, degradation and HA deposition in a body fluid environment, and HAs promotion effect on the formation of new bones and good osseous combination.)

1. A gradient porous bioactive ceramic coating material comprises a titanium substrate and a gradient porous bioactive ceramic coating covering the surface of the titanium substrate, wherein the gradient porous bioactive ceramic coating sequentially comprises an Ag barrier layer, a hydroxyapatite/Ag composite transition layer and a hydroxyapatite bioceramic layer from inside to outside, and is characterized in that the hydroxyapatite bioceramic layer is of a porous structure.

2. The gradient porous bioactive ceramic coating material of claim 1 wherein the hydroxyapatite bioceramic layer has an average pore size of 5 μ ι η to 10 μ ι η.

3. The gradient porous bioactive ceramic coating material of claim 1, wherein the mass fraction of Ag in the hydroxyapatite/Ag composite transition layer is 10% -40%; the thickness of the Ag barrier layer is 200-240 mu m; the thickness of the hydroxyapatite/Ag composite transition layer is 180-200 mu m; the thickness of the hydroxyapatite bioceramic layer is 220-260 μm.

4. A method of preparing a gradient porous bioactive ceramic coating material as claimed in claim 1 or 2 or 3, characterized by comprising the steps of:

(1) placing the pure titanium sample block with the surface pretreated on a constant-temperature heating table for heating, coating pure silver slurry on the surface of the pure titanium sample block, drying in vacuum, and then carrying out broadband laser cladding to form the Ag barrier layer on the surface of the pure titanium sample block;

(2) performing surface pretreatment on the sample block obtained in the step (1), then placing the sample block on a constant-temperature heating table for heating, coating slurry containing hydroxyapatite and Ag on the surface of the Ag barrier layer of the sample block, performing vacuum drying, then performing broadband laser cladding, and forming the hydroxyapatite/Ag composite transition layer on the surface of the Ag barrier layer of the sample block;

(3) and (3) performing surface pretreatment on the sample block obtained in the step (2), then placing the sample block on a constant-temperature heating table for heating, coating slurry containing carbon nano tubes and hydroxyapatite on the surface of the hydroxyapatite/Ag composite transition layer of the sample block, performing vacuum drying, then performing broadband laser cladding, and forming the hydroxyapatite biological ceramic layer on the surface of the hydroxyapatite/Ag composite transition layer of the sample block to obtain the gradient porous bioactive ceramic coating material.

5. The method for preparing the gradient porous bioactive ceramic coating material according to claim 4, wherein in the step (3), the mass ratio of hydroxyapatite to carbon nanotubes in the slurry containing carbon nanotubes and hydroxyapatite is (80-95): (5-20).

6. The preparation method of the gradient porous bioactive ceramic coating material according to claim 4, wherein in the step (3), the process conditions of the broadband laser cladding are as follows: the laser power is 1000W-1400W, the laser scanning speed is 180mm/min-240mm/min, the length of the spot size is 18mm-20mm, the width is 2mm-4mm, and the flow of protective gas argon is 15L/min-20L/min.

7. The method for preparing a gradient porous bioactive ceramic coating material according to claim 4, wherein in the step (3), the slurry containing carbon nanotubes and hydroxyapatite is obtained by mixing hydroxyapatite powder with an average particle size of 20nm and a purity of more than 99.5% and carbon nanotube powder with an average diameter of 40nm and an average length of 15 μm without ball milling, adding the mixture into a polyvinyl alcohol aqueous solution with a concentration of 2 wt.% to 3 wt.% and stirring for 10min to 15min, and then performing ultrasonic dispersion for 5min to 10 min; wherein the stirring speed is 150r/min-240 r/min.

8. The method for preparing a gradient porous bioactive ceramic coating material according to any of claims 4 to 7,

in the step (1), the process conditions of the broadband laser cladding are as follows: the laser power is 1800-2400W, the laser scanning speed is 210-400mm/min, the length of the spot size is 18-20mm, the width is 2-4mm, and the flow of protective gas argon is 15-20L/min;

in the step (2), the process conditions of the broadband laser cladding are as follows: the laser power is 1400-1650W, the laser scanning speed is 210-300mm/min, the length of the spot size is 18-20mm, the width is 2-4mm, and the flow of protective gas argon is 15-20L/min.

9. The method for preparing a gradient porous bioactive ceramic coating material according to any of claims 4 to 7,

in the step (1), the pure silver slurry is obtained by adding Ag powder with the average particle size of 1 μm and the purity of more than 99.5% into a polyvinyl alcohol aqueous solution with the concentration of 2-3 wt.%, stirring for 10-15 min, and then performing ultrasonic dispersion for 5-10 min;

in the step (2), the slurry containing hydroxyapatite and Ag is obtained by mixing Ag powder with the average particle size of 1 μm and the purity of more than 99.5% and hydroxyapatite powder with the average particle size of 20nm and the purity of more than 99.5% without ball milling, adding the mixture into a polyvinyl alcohol aqueous solution with the concentration of 2-3 wt%, stirring for 10-15 min, and then performing ultrasonic dispersion for 5-10 min; wherein the stirring speed is 150r/min-240 r/min.

10. The method for preparing a gradient porous bioactive ceramic coating material according to any of claims 4 to 7,

in the steps (1) to (3), the surface pretreatment of the test piece block is to place the test piece block in a mixed solution of deionized water and ethanol, wash the test piece block for 15min to 30min by using an ultrasonic cleaning machine, and then place the test piece block in a vacuum drying machine at 60 ℃ for drying for 8h to 10 h;

in the steps (1) to (3), the heating temperature of the constant-temperature heating table is 80-90 ℃; the temperature of vacuum drying is 60-70 ℃, and the time of vacuum drying is 24-48 h.

Technical Field

The invention relates to the technical field of bioactive ceramic materials, in particular to a gradient porous bioactive ceramic coating material and a preparation method thereof.

Background

Titanium (Ti) and its alloy have excellent biocompatibility, excellent biomechanical property, good corrosion resistance and excellent forming and processing performance, and have become the preferred materials of artificial joints. The biological ceramic coating implanted on the surface of the artificial joint handle has good biological activity and bone induction capability, the osteogenic performance and biological activity of the coating can be further improved by adding a pore-forming agent and combining a laser cladding means, and the service time and stability of the artificial joint handle are increased.

Hydroxyapatite (Ca)₁₀(PO₄)₆(OH)₂HA) is a bioactive ceramic material, is also a major inorganic component of bone, HAs excellent affinity with bone tissue, is osteoinductive and osteoconductive, and can form chemical bond with living bone tissue. In vitro tests and clinical studies prove that after the artificial joint treated by the HA surface coating is implanted into a body, surrounding bone tissues can quickly form chemical bonds with calcium and phosphorus ions of HA, and induce the adhesion and proliferation of bone cells on the surface of the artificial joint to form firm chemical bond combination, thereby playing a good biological fixation role.

Currently, HA bioactive ceramics have been widely used in the medical field, often as bone substitute materials in orthopedics and dentistry. However, HA itself is highly brittle and HAs poor fracture toughness, making it difficult to use as a single, monolithic implant. Therefore, the preparation of the porous biological ceramic coating by combining the laser cladding technology is an effective method for improving the biological activity of the biological ceramic coating on the surface of the titanium-based material and enhancing the osteogenic performance of the biological ceramic coating.

However, the ceramic and titanium-based materials have large differences in thermal physical parameters such as linear expansion coefficient, melting point and the like, and large thermal stress is easily generated between the titanium-based material and the ceramic coating, so that cracks are caused on the interface between the ceramic coating and the titanium-based material and in the ceramic coating, the interface bonding strength is reduced, and even the ceramic coating falls off in clinical use.

Patent document CN113088958A discloses a gradient composite bioactive ceramic coating material and a preparation method thereof, wherein the coating of the bioactive ceramic coating material comprises an Ag layer, an HA/Ag composite layer, and an HA layer in sequence from bottom to top. In the gradient composite bioactive ceramic coating material, the composition and the structure of the coating are continuously changed from the matrix to the surface, the thermal expansion coefficient in the coating has certain gradient distribution, the problems that cracks are easy to appear on the interface of the ceramic coating and the titanium-based material and the inside of the ceramic coating, and the interface bonding strength is low are well solved, and the coating material has high bioactivity.

However, the above-mentioned coating material surface has low structural similarity with bone tissue, and its biological properties, binding with bone tissue, and promoting the formation of new bone are still to be further improved.

Disclosure of Invention

The invention mainly aims to provide a gradient porous bioactive ceramic coating material and a preparation method thereof.

In order to achieve the above object, according to one aspect of the present invention, there is provided a gradient porous bioactive ceramic coating material, comprising a titanium substrate and a gradient porous bioactive ceramic coating covering the surface of the titanium substrate, wherein the gradient porous bioactive ceramic coating comprises, from inside to outside, an Ag barrier layer, a hydroxyapatite/Ag composite transition layer, and a hydroxyapatite bioceramic layer in this order, and the hydroxyapatite bioceramic layer has a porous structure.

According to the gradient design principle, the components and the microstructure of the coating are designed in a gradient manner, and a hydroxyapatite bioceramic layer with a porous structure is formed on the surface of the coating material, and the bioceramic coating with the porous structure is very similar to the host bone tissue in structure, so that the bioceramic coating has better biological performance; the pores on the surface of the coating material are beneficial to protein absorption and osteoblast attachment, and the large specific surface area of the pores is also beneficial to ion exchange, degradation and HA deposition in a body fluid environment, so that the coating material HAs a promotion effect on the formation of new bones and good osseous combination. The coating material not only has good biological performance, but also has good combination with bone tissues, and can promote the bony combination of the coating material and new bones.

In addition, the composition and the structure of the coating in the coating material are continuously changed in a gradient manner from the substrate to the surface, so that the thermal expansion coefficient in the ceramic coating has a certain gradient distribution range, the coating material has good metallurgical bonding force with a pure titanium substrate, and the coating material has high bioactivity. The Ag barrier layer is introduced into the coating material, so that the floating of the titanium element of the base material can be prevented in the laser cladding process, and the problem that the ceramic coating contains a large amount of calcium titanate and loses a large amount of active substances due to the fact that the titanium element and HA are easily subjected to chemical reaction under a high-temperature environment is solved.

Further, the average pore diameter of the hydroxyapatite bioceramic layer is 5-10 μm.

Furthermore, the mass fraction of Ag in the hydroxyapatite/Ag composite transition layer is 10-40%; the thickness of the Ag barrier layer is 200-240 μm; the thickness of the hydroxyapatite/Ag composite transition layer is 180-200 mu m; the thickness of the hydroxyapatite bioceramic layer is 220-260 μm.

According to another aspect of the present invention, there is provided a method for preparing the gradient porous bioactive ceramic coating material, comprising the following steps:

(1) placing the pure titanium sample block with the surface pretreated on a constant-temperature heating table for heating, coating pure silver slurry on the surface of the pure titanium sample block, drying in vacuum, and then carrying out broadband laser cladding to form an Ag barrier layer on the surface of the pure titanium sample block;

(2) performing surface pretreatment on the sample block obtained in the step (1), then placing the sample block on a constant-temperature heating table for heating, coating slurry containing hydroxyapatite and Ag on the surface of an Ag barrier layer of the sample block, performing vacuum drying, then performing broadband laser cladding, and forming a hydroxyapatite/Ag composite transition layer on the surface of the Ag barrier layer of the sample block;

(3) and (3) performing surface pretreatment on the sample block obtained in the step (2), then placing the sample block on a constant-temperature heating table for heating, coating slurry containing carbon nano tubes and hydroxyapatite on the surface of the hydroxyapatite/Ag composite transition layer of the sample block, performing vacuum drying, then performing broadband laser cladding, and forming a hydroxyapatite biological ceramic layer on the surface of the hydroxyapatite/Ag composite transition layer of the sample block to obtain the gradient porous bioactive ceramic coating material.

According to the invention, the Carbon Nano Tubes (CNTs) are added into the slurry of the hydroxyapatite biological ceramic layer, and the characteristics of rapid melting/rapid solidification of the powder by laser cladding and the characteristic of easy splashing of the carbon nano tubes in the laser cladding process are utilized, so that the carbon nano tubes added into the powder are splashed out of a molten pool in the laser cladding process, and further holes are formed on the surface of the bioactive ceramic coating (in the hydroxyapatite biological ceramic layer), so that the surface of the coating material is of a porous structure similar to a bone structure, and the HA content is kept high. The coating material has good bioactivity, can be better combined with bone tissues, and can promote the bony combination of the coating material and the new bone.

In addition, the Ag barrier layer is introduced on the titanium substrate, so that the floating of the titanium element of the substrate can be hindered in the laser cladding process, and the problem that the ceramic coating contains a large amount of calcium titanate and loses a large amount of active substances due to the fact that the titanium element and HA are easy to chemically react under a high-temperature environment is solved. According to the invention, the Ag powder is introduced, and a three-layer powder paving scheme is designed to form the porous bioactive ceramic coating material with a three-layer gradient structure, so that the coating material has good bioactivity and higher bonding strength with a titanium substrate.

The Ag barrier layer in the invention is mainly used for isolatingThe active layer and the titanium substrate are separated, so that the chemical reaction between the active layer and the titanium substrate is avoided, and inactive CaTiO is generated₃The HA content of the coating is ensured to be higher; the transition layer is uniformly dispersed with two phases of Ag and HA and is mainly used for relieving the mismatch of the thermal expansion coefficients between the active layer and the matrix so as to enhance the bonding strength of the active layer and the matrix; the HA bioceramic layer with the porous structure takes HA as a main phase, so that the coating material HAs good bioactivity and is well combined with bone tissues.

Further, in the step (3), the mass ratio of hydroxyapatite to carbon nanotubes in the slurry containing carbon nanotubes and hydroxyapatite is (80-95): (5-20). The hydroxyapatite and the carbon nano tube in the slurry are in the proportion range, and the hydroxyapatite biological ceramic layer with a porous structure can be prepared.

Further, in the step (3), the process conditions of the broadband laser cladding are as follows: the laser power is 1000W-1400W, the laser scanning speed is 180mm/min-240mm/min, the length of the spot size is 18mm-20mm, the width is 2mm-4mm, and the flow of protective gas argon is 15L/min-20L/min.

Further, in the step (3), the slurry containing carbon nanotubes and hydroxyapatite is obtained by mixing hydroxyapatite powder with an average particle size of 20nm and a purity of more than 99.5% and carbon nanotube powder with an average diameter of 40nm and an average length of 15 μm without ball milling, adding the mixture into a polyvinyl alcohol aqueous solution with a concentration of 2 wt.% to 3 wt.%, stirring for 10min to 15min, and then ultrasonically dispersing for 5min to 10 min; wherein the stirring speed is 150r/min-240 r/min.

Further, in the step (1), the process conditions of the broadband laser cladding are as follows: the laser power is 1800-2400W, the laser scanning speed is 210-400mm/min, the length of the spot size is 18-20mm, the width is 2-4mm, and the flow of protective gas argon is 15-20L/min.

Further, in the step (2), the process conditions of the broadband laser cladding are as follows: the laser power is 1400-1650W, the laser scanning speed is 210-300mm/min, the length of the spot size is 18-20mm, the width is 2-4mm, and the flow of protective gas argon is 15-20L/min.

Further, in the step (1), the pure silver paste is obtained by adding Ag powder having an average particle size of 1 μm and a purity of more than 99.5% to a polyvinyl alcohol aqueous solution having a concentration of 2 wt.% to 3 wt.% and stirring for 10min to 15min, and then performing ultrasonic dispersion for 5min to 10 min.

Further, in the step (2), the slurry containing hydroxyapatite and Ag is obtained by mixing Ag powder with an average particle size of 1 μm and a purity of more than 99.5% and hydroxyapatite powder with an average particle size of 20nm and a purity of more than 99.5% without ball milling, adding the mixture into a polyvinyl alcohol aqueous solution with a concentration of 2 wt.% to 3 wt.%, stirring for 10min to 15min, and then ultrasonically dispersing for 5min to 10 min; wherein the stirring speed is 150r/min-240 r/min.

Further, in the steps (1) to (3), the surface of the test piece is pretreated by placing the test piece in a mixed solution of deionized water and ethanol, cleaning the test piece for 15min to 30min by using an ultrasonic cleaning machine, and then drying the test piece in a vacuum drying machine at 60 ℃ for 8h to 10 h.

Further, in the steps (1) to (3), the heating temperature of the constant-temperature heating table is 80-90 ℃; the temperature of vacuum drying is 60-70 ℃, and the time of vacuum drying is 24-48 h.

Compared with the prior art, the invention has the beneficial effects that:

(1) the hydroxyapatite biological ceramic layer in the coating material has a porous structure, so that the hydroxyapatite biological ceramic layer is very similar to a host bone tissue in structure and has better biological performance; the pores on the hydroxyapatite bioceramic layer are beneficial to protein absorption and osteoblast attachment, and the large specific surface area of the pores is also beneficial to ion exchange, degradation and HA deposition in a body fluid environment, so that the hydroxyapatite bioceramic layer HAs a promotion effect on the formation of new bones and good bone combination.

(2) According to the invention, the Carbon Nano Tubes (CNTs) are added into the hydroxyapatite slurry, and the characteristics of rapid melting/rapid solidification of powder and easiness in splashing of the carbon nano tubes in the laser cladding process are utilized, so that the carbon nano tubes added into the slurry are splashed out of a molten pool in the laser cladding process, and further holes are formed on the surface of the coating material (in the hydroxyapatite biological ceramic layer).

Drawings

FIG. 1 is a schematic structural diagram of the gradient porous bioactive ceramic coating material of the present invention.

FIG. 2 is a cross-sectional profile of the coating materials prepared in examples 1, 2, 3, 4 and 1 of the present invention under super-depth of field three-dimensional microscope observation. Wherein (a) is example 1, (b) is example 2, (c) is example 3, (d) is example 4, and (e) is comparative example 1.

Fig. 3 is an XRD pattern of the coating materials prepared in example 1, example 2, example 3, example 4 and comparative example 1 of the present invention. Wherein (a) is example 1, (b) is example 2, (c) is example 3, (d) is example 4, and (e) is comparative example 1.

FIG. 4 is a XRD spectrum of HA, TCP, TTCP, CaTiO contained in the coating materials prepared in examples 1, 2, 3, 4 and 1 according to the present invention by quantitative analysis₃And the relative content of Ag and CaO in the histogram. Wherein (a) is example 1, (b) is example 2, (c) is example 3, (d) is example 4, and (e) is comparative example 1.

Fig. 5 is a SEM electron microscope observation of the surface porous structure of the coating materials prepared in examples 1, 2, 3, 4 and 1 of the present invention. Wherein (a) is example 1, (b) is example 2, (c) is example 3, (d) is example 4, and (e) is comparative example 1.

Fig. 6 is a pore size statistical result of the gradient porous bioactive ceramic coatings prepared in examples 1, 2, 3 and 4 of the present invention. Wherein (a) is example 1, (b) is example 2, (c) is example 3, and (d) is example 4.

FIG. 7 shows the surface morphology of the coating materials prepared in examples 1, 2, 3, 4 and 1 according to the present invention and the pure titanium substrate in the friction wear test under SEM electron microscope. Wherein (a) is example 1, (b) is example 2, (c) is example 3, (d) is example 4, (e) is comparative example 1, and (f) is a pure titanium matrix.

FIG. 8 is the volume abrasion loss results of the frictional abrasion test of the gradient porous bioactive ceramic coating prepared by the present invention.

FIG. 9 is the surface topography of slurry C spread on the surface of HA/Ag composite transition layer of the coupon at various stages during the laser cladding process. Wherein, (a) is the surface morphology of the slurry C when not melted, (b) is the surface morphology of the slurry C when the slurry C starts to melt, (C) is the surface morphology of the slurry C when not completely melted, and (d) is the surface morphology of the slurry C when completely melted.

FIG. 10 is an electron microscope image of the surface of the coating material when preparing a sample of the gradient porous bioactive ceramic coating. Wherein (a) shows surface splash particles of the coating material, and (b) shows the nano-scale microstructure of the surface splash particle region 1 in (a).

In the above figures, the following reference numerals are included:

1. a titanium substrate; 2. an Ag barrier layer; 3. a hydroxyapatite/Ag composite transition layer; 4. hydroxyapatite bioceramic layer.

Detailed Description

In order to facilitate an understanding of the present invention, the present invention will be described more fully and in detail with reference to the preferred embodiments, but the scope of the present invention is not limited to the specific embodiments described below.

Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.

Example 1:

the gradient porous bioactive ceramic coating material of the embodiment of the invention has a structural schematic diagram shown in fig. 1, and comprises a titanium substrate 1 and a gradient porous bioactive ceramic coating covering the surface of the titanium substrate 1. The gradient porous bioactive ceramic coating sequentially comprises an Ag barrier layer 2, a hydroxyapatite/Ag composite transition layer 3 and a hydroxyapatite biological ceramic layer 4 from inside to outside. Wherein, the mass fraction of Ag in the hydroxyapatite/Ag composite transition layer 3 is 25%, and the mass fraction of HA (hydroxyapatite) is 75%; the thickness of the Ag barrier layer 2 is about 200-240 μm, and the thickness of the hydroxyapatite/Ag composite transition layer 3 is about 180-200 μm. The hydroxyapatite bioceramic layer 4 is of a porous structure, the average pore size of the hydroxyapatite bioceramic layer 4 is about 7.22 +/-1.88 μm, and the thickness of the hydroxyapatite bioceramic layer 4 is about 220 μm-260 μm.

The preparation method of the gradient porous bioactive ceramic coating material comprises the following steps:

(1) preparing raw materials and pretreating the raw materials:

0.2g of Ag powder (purity not less than 99.5% and average particle size of 1 μm) was weighed using an electronic analytical balance, added to 1mL of a 3 wt.% aqueous polyvinyl alcohol solution, stirred for 10min, and placed in an ultrasonic dispersion table for ultrasonic dispersion for 5min to prepare slurry A (Ag slurry).

Mixing hydroxyapatite powder (purity is more than or equal to 99.5 percent and average particle size is 20nm) and Ag powder (purity is more than or equal to 99.5 percent and average particle size is 1 mu m) according to the mass content ratio of 75 percent: adding 25 percent of the mixture into a horizontal planetary ball mill for ball milling and mixing (the rotating speed is 150r/min, the ball milling time is 8 hours), and preparing into mixed powder. 0.2g of the mixed powder was weighed using an electronic analytical balance, added to 1mL of a 3 wt.% aqueous polyvinyl alcohol solution, stirred for 10min, and placed on an ultrasonic dispersion table to be ultrasonically dispersed for 5min, thereby preparing slurry B (Ag + HA mixed slurry).

Mixing hydroxyapatite powder (the purity is more than or equal to 99.5 percent and the average particle size is 20nm) and CNTs powder (the purity is more than or equal to 95 percent, the average diameter is 40nm and the average length is 15 mu m) according to the mass content ratio of 95: 5, adding the mixture into a horizontal planetary ball mill for ball milling and mixing (the rotating speed is 150r/min, the ball milling time is 8 hours), and preparing into mixed powder. 0.4g of the mixed powder was weighed using an electronic analytical balance, added to 1mL of a polyvinyl alcohol aqueous solution having a concentration of 3 wt.%, stirred for 10min, and placed in an ultrasonic dispersion table to be ultrasonically dispersed for 5min, to prepare slurry C (HA + CNTs pore-forming mixed slurry).

The method comprises the steps of cutting a pure titanium plate into sample blocks with the size of 20mm multiplied by 30mm multiplied by 4mm by a warp cutting machine, polishing the sample blocks with 80-mesh SiC abrasive paper to remove surface oxide films, then placing the polished pure titanium sample blocks into deionized water and ethanol, cleaning the sample blocks for 30min by using an ultrasonic cleaning machine, and drying the cleaned sample blocks in a vacuum drying machine at the temperature of 60 ℃ for 8h for later use.

(2) And (2) placing the sample block prepared in the step (1) on a constant-temperature heating table at 80 ℃, uniformly spreading the slurry A on the surface of a sample block substrate, and then placing the sample block substrate into a vacuum dryer at 60 ℃ for drying for 24 hours.

And adopting a broadband laser cladding process to clad Ag on the surface of the pure titanium matrix to form an Ag barrier layer. The broadband laser cladding process parameters are as follows: the laser power is 1800W, the laser scanning speed is 210mm/min, the spot size is 18mm multiplied by 2mm, and the flow of protective gas argon is 15L/min.

(3) And (3) placing the sample block with the surface coated with the Ag barrier layer prepared in the step (2) in deionized water and ethanol, cleaning the sample block for 30min by using an ultrasonic cleaning machine, and then placing the cleaned sample block in a vacuum drying machine at 60 ℃ for drying for 8 h.

And placing the dried sample block coated with the Ag barrier layer on a constant-temperature heating table at 80 ℃ for heating, uniformly spreading the slurry B on the surface of the Ag barrier layer, and drying in a vacuum dryer at 60 ℃ for 24 hours.

And adopting a broadband laser process to coat Ag and HA on the surface of the Ag barrier layer in a cladding way to form an HA/Ag composite transition layer. The parameters of the broadband laser cladding process in the process are as follows: the laser power is 1650W, the laser scanning speed is 300mm/min, the spot size is 18mm multiplied by 2mm, and the flow of protective gas argon is 15L/min.

(4) And (3) placing the sample block coated with the HA/Ag composite transition layer in the step (3) in deionized water and ethanol, cleaning for 30min by using an ultrasonic cleaning machine, and placing the cleaned sample block in a vacuum drying machine at 60 ℃ for drying for 8h for later use.

And (3) placing the sample block on a constant-temperature heating table at 80 ℃ for heating, uniformly spreading the slurry C on the surface of the HA/Ag composite transition layer of the sample block, and then placing the sample block into a vacuum dryer at 60 ℃ for drying for 24 hours.

And (3) adopting a broadband laser process to coat the HA + CNTs on the surface of the HA/Ag composite transition layer to complete the preparation of the gradient porous bioactive ceramic coating material. The cladding technological parameters in the process are as follows: the laser power is 1200W, the laser scanning speed is 180mm/min, the spot size is 18mm multiplied by 2mm, and the flow of protective gas argon is 15L/min. In the broadband laser cladding process, the CNTs are splashed out of the HA layer, and the hole pits left after the CNTs are splashed enable the HA layer to form a porous structure.

The test results of the samples of the gradient porous bioactive ceramic coating material prepared in this example are shown in fig. 2 to 8; fig. 2(a) is the cross-sectional morphology of the gradient porous bioactive ceramic coating layer prepared in the embodiment, which is observed by a super-depth-of-field three-dimensional microscope, wherein a is the prepared porous hydroxyapatite biological ceramic layer, and B is a titanium substrate.

Fig. 3(a) is an XRD spectrum of the gradient porous bioactive ceramic coating prepared in this example, and as can be seen from fig. 3(a), the ceramic coating mainly contains HA (hydroxyapatite), TCP (tricalcium phosphate), and TTCP (tetracalcium phosphate) active substances, and no peak containing CNTs is found in the coating, which indicates that HA is unstable at high temperature, and is partially decomposed into TCP and TTCP, and CNTs are easy to splash, so that the CNTs content in the coating is very low.

Fig. 4(a) is a result of quantitative analysis of XRD spectrum of this example, and it can be seen that the HA content of the ceramic coating prepared in this example is about 60 wt.%, and the ceramic coating prepared retains a higher HA content.

The surface microscopic morphology of the sample of the gradient porous bioactive ceramic coating prepared in this example is shown in fig. 5(a), and as can be seen from fig. 5(a), the surface of the coating of this example is a porous structure similar to a bone structure. The statistical results of the surface pore size of the sample of the gradient porous bioactive ceramic coating prepared in this example are shown in FIG. 6(a), and it can be seen from FIG. 6(a) that the average pore size of this example is about 7.22. + -. 1.88 μm.

The results of the frictional wear test of the samples of the gradient porous bioactive ceramic coating material prepared in this example are shown in fig. 7(a) and fig. 8. As can be seen from fig. 7(a) and 8, the wear mechanisms of the porous bioactive ceramic coating material prepared in this example are adhesive wear and abrasive wear, which significantly improves the frictional wear performance of the medical titanium substrate.

The pore formation process of the HA bioceramic layer with porous structure in the sample of gradient porous bioactive ceramic coating material prepared in this example is shown in fig. 9. Fig. 9(a) shows slurry C that is prepared after drying, and it is understood that the surface of slurry C after drying is fluffy and porous, and provides conditions for forming holes in the cladding coating. Fig. 9(b) shows the slurry C which starts to melt, and it is understood that the fluffy porous state on the surface of the slurry C becomes massive. Fig. 9(C) shows the incompletely melted slurry C, and K shows splashed particles, indicating that the coating surface contains a large amount of splashed particles. Fig. 9(d) shows the completely melted slurry C, and it can be seen that the completely melted slurry C is a porous coating layer.

This example shows spattering particles when preparing a sample of a gradient porous bioactive ceramic coating material as shown in fig. 10 (a). As can be seen from fig. 10(a), the splash particle surface is in a fluff state. Fig. 10(b) is a nano-scale microstructure of the splash particle surface of region 1 in fig. 10 (a). In FIG. 10(b), L is CNTs, N is sintered HA, and it is understood that the scattering particles are HA and contain a large amount of unsintered CNTs. Namely, the formation of pores in the hydroxyapatite bioceramic layer with a porous structure is shown because the scattering of the CNTs takes away the sintered HA, and micropores are formed on the surface of the coating.

The results show that the gradient porous bioactive ceramic coating material prepared by the embodiment utilizes the characteristics of laser cladding of rapid melting/rapid solidification of the powder layer and the characteristic of easiness in splashing of the CNTs in the laser cladding process, so that the CNTs added in the coating are splashed out of a molten pool in the laser cladding process, holes are formed on the surface of the hydroxyapatite bioceramic layer, the surface of the coating material is of a porous structure similar to a bone structure, and the HA content is kept high. The coating material has good bioactivity and good application prospect, and provides a process scheme for preparing the porous ceramic coating by laser cladding.

Comparative example 1 and example 2, example 3, example 4:

comparative example 1 and examples 2, 3 and 4 differ from example 1 only in the preparation of slurry C in step (1) (see table 1), and the other preparation processes are exactly the same as example 1.

Table 1 slurries C used in examples 1, 2, 3, 4 and comparative example 1

The cross-sectional shapes of the gradient porous bioactive ceramic coatings prepared in the comparative example 1 and the examples 2, 3 and 4 observed by an ultra-depth-of-field three-dimensional microscope are respectively shown in fig. 2(e), fig. 2(b), fig. 2(c) and fig. 2(d), wherein D, F, H, J is a titanium matrix, and C, E, G, I is a coating. As can be seen from the section morphology observed by the super-depth-of-field three-dimensional microscope, the porous bioactive ceramic coating which forms good metallurgical bonding with the titanium matrix can be prepared within the protection range of the invention under the adding condition of CNTs powder with different proportions.

The XRD patterns of the gradient porous bioactive ceramic coatings prepared in comparative example 1 and examples 2, 3 and 4 are shown in fig. 3(e), 3(b), 3(c) and 3(d), respectively, and it can be known from the XRD pattern compositions that porous bioactive ceramic coatings containing active substances such as HA (hydroxyapatite), TCP (tricalcium phosphate) and TTCP (tetracalcium phosphate) can be prepared under the conditions of adding CNTs powders with different ratios within the protection scope of the present invention.

HA, TCP, TTCP, CaTiO contained in gradient porous bioactive ceramic coatings prepared in comparative example 1 and examples 2, 3 and 4₃The relative contents of Ag and CaO are shown in FIG. 4(e), FIG. 4(b), FIG. 4(c) and FIG. 4(d), respectively, and it can be seen from the analysis of the relative contents that, within the protection scope of the present invention, as the proportion of CNTs added for pore formation is from 5 to 20, the content of HA (hydroxyapatite) is reduced from 57.3% to 14.6%, the content of TCP (tricalcium phosphate) is reduced from 19% to 4.2%, and the content of TTCP (tetracalcium phosphate) is increased from 13.2% to 28.8%; it is known that the content of active substances such as HA (hydroxyapatite), TCP (tricalcium phosphate), TTCP (tetracalcium phosphate) and the like in the porous ceramic coating can be significantly influenced under the condition of adding CNTs powder with different proportions.

The surface porous structures of the gradient porous bioactive ceramic coatings prepared in the comparative example 1 and the examples 2, 3 and 4 are respectively shown in fig. 5(e), 5(b), 5(c) and 5(d) observed by an SEM electron microscope, and from the surface porous structures of the coatings, it can be known that the porous bioactive ceramic coatings can be prepared under the adding conditions of CNTs powder with different proportions within the protection range of the invention, and meanwhile, from the increase of the adding amount of the CNTs powder, the pores of the prepared porous ceramic coatings are changed into reticular pores from circular pores along with the pore-forming proportion from 5 to 20, while from the comparative example 1, the ceramic coatings prepared without adding the CNTs for pore-forming have no porous structures on the surfaces.

The pore diameter statistics of the gradient porous bioactive ceramic coatings prepared in examples 2, 3 and 4 are shown in fig. 6(b), 6(c) and 6(d), respectively, and it can be understood from the pore diameter statistics that porous bioactive ceramic coatings with pore diameters ranging from 5 μm to 10 μm can be prepared under the condition of adding CNTs powders with different ratios within the protection range of the present invention.

The surface morphology of the friction and wear test observed by the SEM electron microscope of the gradient porous bioactive ceramic coating prepared in the comparative example 1 and the gradient porous bioactive ceramic coatings prepared in the examples 2, 3 and 4 is respectively shown in FIG. 7(e), FIG. 7(b), FIG. 7(c) and FIG. 7(d), and the surface morphology of the friction and wear test observed by the SEM electron microscope of the titanium matrix is shown in FIG. 7 (f).

The results of the volume abrasion loss of the friction abrasion tests of the gradient porous bioactive ceramic coatings prepared in the comparative example 1 and the examples 2, 3 and 4 are shown in fig. 8, and it can be known from the results of the volume abrasion loss of the friction abrasion tests that the volume abrasion loss of the prepared coatings is obviously smaller than that of the medical titanium matrix under the condition of adding CNTs powder with different proportions in the protection range of the invention, so that the abrasion performance of the medical titanium is obviously improved, the medical titanium is endowed with bioactivity, and the coatings are endowed with a porous structure similar to bone tissues.

In conclusion, according to the technical scheme, the CNTs powder is added into the slurry of the hydroxyapatite biological ceramic layer, the wide-band laser cladding process is used, the gradient porous bioactive ceramic coating which forms good metallurgical bonding with the titanium-based material is prepared, the HA (hydroxyapatite) content in the coating is kept high, the biological activity of the gradient porous bioactive ceramic coating is ensured, and the coating is endowed with a porous structure similar to bone tissues.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.