RU2634394C1 - Method for manufacturing target from hydroxyapatite for ion-plasma coating deposition - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method involves the use of synthetic hydroxyapatite powder or natural hydroxyapatite or a mixture of synthetic and natural hydroxyapatite with a particle size of less than 60 microns. A plasticiser - 10% solution of polyvinyl alcohol in the amount of 6-8% of the powder mass is added. The moistened plasticized mass is kept in a closed container for 20 to 24 hours at room temperature. Briquettes are moulded at the pressure of not less than 50 MPa, then the briquettes are ground to a granule size of less than 2 mm, the resulting granules are subjected to uniaxial two-sided pressing first at the pressure of 25 to 30 MPa. The pre-pressing is stopped and the final pressing is carried out at the pressure of 60 to 80 MPa. The resulting compact is dried for 24 hours at the temperature of 70°C. It is placed on a substrate with a powder of the used hydroxyapatite, burned in air at the heating rate of 50°C per hour to the temperature of 1000 to 1100°C and maintained at the final temperature for 2 hours.

EFFECT: homogeneous composition without impurities, no overpressure cracks, slight fire shrinkage, optimum porosity, compressive strength, and bending strength.

3 ex, 1 tbl

Description

The invention relates to the field of molded ceramic products based on phosphates and can be used for the manufacture of targets made of hydroxyapatite for ion-plasma deposition of calcium phosphate coatings on the surface of medical implants.

A known method of manufacturing a target for coatings [RU 2305717 C2, C23C 14/36 (2006.01), B22F 3/105 (2006.01), publ. September 10, 2007], which consists in forming at least three tablets, forming a working spray, intermediate and initiating layers, from at least three powder mixtures having exothermic compositions capable of chemical interaction in the mode of self-propagating high-temperature synthesis after local thermal initiation. Layered layers on a profiled metal plate through a layer of a mixture of metal solder tablets of the intermediate layer, the working spray layer and the initiating layer. The process of self-propagating high-temperature synthesis in the initiating layer is started and the metal solder and metal filler, which is part of the powder mixture of at least one of the layers, are melted under its action. The layers are pressurized by pressing 2-10 s after the completion of the self-propagating high-temperature synthesis process and then maintaining the pressure for at least 5 s, as a result of which the formed working spray layer and the intermediate layer with a profiled metal plate are connected through a metal solder layer, then the initiating layer is removed . As a result of the process of self-propagating high-temperature synthesis, a working spray layer is obtained containing a skeletal porous structure from a material including carbide and / or nitride and / or carbonitride and / or boride and / or group IV-VI transition metal silicide and / or calcium oxide and / or calcium phosphate and / or zirconium oxide and / or hydroxyapatite or a mixture thereof, and a metal filler filling the pores within the skeletal porous structure. Pressing is carried out by direct pressing in a stamp or mold or quasi-isotropic pressing with a medium that transfers pressure, or pressing by a roll.

This method does not ensure the creation of a target from a pure material - hydroxyapatite, since hydroxyapatite without metal additives in the mixture is not able to independently support self-propagating high-temperature synthesis. The targets obtained in this way consist of three layers, which complicates the process of manufacturing the target.

A known method of manufacturing a target of synthetic hydroxyapatite with a particle size of up to 80 nm to obtain coatings by ion-plasma methods according to the following procedure. The synthetic hydroxyapatite powder is pressed at a pressure of 70 MPa, and then the resulting compact is fired at 1100 ° C for 1 hour in air [Aronov AM, Pichugin V.F., Eshenko EV, Ryabtseva MA, Surmenev R .A., Tverdokhlebov S.I., Shesterikov E.V. Thin calcium phosphate coatings obtained by high-frequency magnetron sputtering and the prospects for their use in medical technology // Medical equipment. - 2008. - T. 3. - S. 18-22].

A known method of manufacturing a target of hydroxyapatite for coating on various substrates by high-frequency magnetron sputtering [Ievlev VM, Domashevskaya EP, Terekhov VA, Kashkarov VM, Vakhtel VM, Tretyakov Yu. D., Putlyaev V.I., Barinov S.M., Smirnov V.V., Belonogov E.K., Kostyuchenko A.V. Synthesis of nanocrystalline hydroxyapatite films // Condensed Matter and Interphase Boundaries. - 2007. - T. 9. - No. 3. - S. 209-215], selected as a prototype. Hydroxyapatite synthesized by precipitation of the corresponding salts from aqueous solutions is used to make the target. A plasticizer and an additive intensifying the compaction process are added. Uniaxial pressing is performed under a pressure of 150 MPa. To remove the plasticizer from the compact mass, preliminary heating is carried out, and then final firing at 900 ° C and incubated at a final temperature for 2 hours.

The methods for manufacturing targets from finely dispersed nanopowders of synthetic hydroxyapatite, described above, are characterized by difficult removal of air from the press during pressing of the target with a thickness of more than 4 mm, which, as a rule, leads to the formation of repressive cracks and shrinkage of more than 10%.

The objective of the invention is the manufacture of a solid state target of hydroxyapatite for spraying coatings by vacuum ion-plasma methods.

In the proposed method of manufacturing a target of hydroxyapatite for ion-plasma spraying of coatings, as in the prototype, a synthetic hydroxyapatite powder with the addition of a plasticizer is used, uniaxial pressing is performed, preheating is carried out to remove the plasticizer, and final firing is held at a final temperature for 2 hours.

According to the invention, a powder of either synthetic or natural hydroxyapatite or a mixture of synthetic and natural hydroxyapatite with a particle size of less than 60 microns is used. As a plasticizer use a 10% solution of polyvinyl alcohol in an amount of 6-8% by weight of the powder. Moist plasticized mass is kept in a closed container for 20 to 24 hours at room temperature. Briquettes are formed at a pressure of at least 50 MPa, which are then crushed to a granule size of less than 2 mm. The obtained granules are subjected to uniaxial double-sided pressing at a pressure of from 25 to 30 MPa. Then the preliminary pressing is stopped and the final pressing is carried out at a pressure of from 60 to 80 MPa. The resulting compact is dried for 24 hours at a temperature of 70 ° C and placed on a substrate with a powder of the used hydroxyapatite powder. Then the compact is fired in air at a heating rate of 50 ° C per hour to a temperature of from 1000 to 1100 ° C.

The use of hydroxyapatite larger than 60 microns complicates the sintering process.

The use of plasticizer - a solution of 10% polyvinyl alcohol in an amount of less than 6 wt. % by weight of the powder does not provide sufficient compressive strength, and an increase in the amount of plasticizer over 8 wt. % leads to extrusion of the liquid phase and the deterioration of the quality of the compact.

Exposure to the moistened plasticized mass in a closed container ensures uniform distribution of the plasticizer solution over the volume of the moistened powder. At the same time, exposure for less than 20 hours at room temperature is insufficient to average the properties of the mass. With an exposure of up to 24 hours, the required quality of plasticized mass is achieved.

The formation of briquettes and their subsequent grinding to obtain granules increases the manufacturability of the pressing process and reduces the risk of re-cracking. In the process of briquetting, the finely dispersed powder is densified and the amount of the gas phase causing re-compression is reduced. Briquetting pressure of at least 50 MPa ensures the production of dense granules.

Granules no larger than 2 mm in size have good flowability, which allows uniformly filling the mold volume.

Pre-pressing during the manufacture of the target removes most of the air located in the space between the pressing granules, moreover, closed pores are formed at pressures above 30 MPa, from which compressed air is difficult to exit, and at pressures less than 25 MPa, pressing does not provide the required pressing density.

Final pressing at a pressure of less than 60 MPa does not provide sufficient density and strength of the pressing. Pressure above 80 MPa does not lead to a significant compaction of the compact, but increases the risk of re-cracking cracks.

Preheating to remove the plasticizer for 24 hours at 70 ° C avoids cracking of the compact due to the absence of a large amount of evaporating moisture. In order not to adhere the compact to the substrate during the firing process, the used hydroxyapatite is poured from the powder, which allows not to contaminate the compact and avoid cracking during shrinkage of the compact.

The final firing temperature in air of less than 1000 ° C is not sufficient for the target to acquire the necessary mechanical strength, and firing at temperatures above 1100 ° C does not improve the quality of the target. A holding time at a final temperature of 2 hours is sufficient to complete the sintering process.

Thus, the proposed method, in comparison with the prototype, allows you to make a solid-state target of hydroxyapatite for spraying coatings with vacuum ion-plasma methods, characterized by a homogeneous composition without impurities, the absence of re-cracking cracks, small fire shrinkage from 6.4 to 7.2% due to two-stage pressing and firing, with porosity from 15.2 to 16.6%, compressive strength from 40.8 to 52.3 MPa, bending strength from 14.2 to 16.2 MPa.

Table 1 presents the manufacturing modes and properties of the finished targets.

Example 1. A powder of synthetic hydroxyapatite Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ with a particle size of less than 60 microns, obtained by mechanochemical synthesis [Chaykina MV, Bulina NV, Prosanov I.Yu., Ishenko A.V. ., Medvedko OV, Aronov AM Mechanochemical synthesis of hydroxylapatite with SiO ₄ ⁴ substitutions // Chemistry in the interests of sustainable development. - 2012. - T. 20. - No. 4. - S. 477-489], poured into a porcelain cup, added a 10% solution of polyvinyl alcohol in an amount of 6% by weight of hydroxyapatite powder and mixed. The resulting moistened plasticized mass was kept in a closed desiccator for 24 hours at room temperature. Briquettes in the form of plexiglas with a diameter of 50 mm and a height of 30 mm were pressed from the resulting mass using a MIRI-100 hydraulic press at a pressure of 60 MPa. Then the briquettes were ground in a porcelain mortar. The obtained granules were sieved through a sieve with a mesh size of 2 mm Pellets with a size of less than 2 mm were poured into a mold with a diameter of 161.6 mm and a height of 30 mm by 2/3 of its volume and performed uniaxial double-sided pressing using a MIRI-100 hydraulic press at first at a pressure of 25 MPa for 7 seconds. After that, the preliminary pressing was stopped for air to escape from the mass. Pressing was again performed at a final pressure of 80 MPa for 10 seconds. After pressing, the compact was removed from the mold and dried for 24 hours at a temperature of 70 ° C in an oven. The dried compact was placed on a corundum substrate with an addition of the used hydroxyapatite powder and burned in a TK.98-1400.3F electric furnace with silicon carbide heaters in air with a heating rate of 50 ° C per hour to 1000 ° C and holding at a final temperature of 2 hours. Thus, a disk-shaped target with a diameter of 150 mm and a height of 10 mm was obtained.

Other examples of the manufacture of targets and the properties of finished targets from hydroxyapatite of various nature are shown in table 1.

In Example 2, natural hydroxyapatite obtained from cattle bones burned at 950 ° C was used as the material for the manufacture of the target.

In Example 3, a mixture of synthetic hydroxyapatite and natural hydroxyapatite (from bones of cattle) in an equal ratio was used to make the target.

Claims (1)

A method of manufacturing a target of hydroxyapatite for ion-plasma spraying of coatings, including the use of hydroxyapatite powder, the addition of a plasticizer, uniaxial pressing, preheating to remove the plasticizer and final firing with exposure at a final temperature for 2 hours, characterized in that they use hydroxyapatite powder natural hydroxyapatite or a mixture of synthetic and natural hydroxyapatite with a particle size of less than 60 microns, and use as a plasticizer they form a 10% solution of polyvinyl alcohol in an amount of 6-8% by weight of hydroxyapatite powder, while the moistened plasticized mass is kept in a closed container for 20 to 24 hours at room temperature, briquettes are molded at a pressure of at least 50 MPa, then briquettes crushed to a granule size of less than 2 mm, the obtained granules are subjected to uniaxial double-sided pressing first at a pressure of from 25 to 30 MPa, then the preliminary pressing is stopped and the final pressing is carried out at a pressure of from 60 to 80 MPa, after h of the resulting compact was dried for 24 hours at 70 ° C, then placed on a substrate with the powder used bedding hydroxyapatite, calcined in air at 50 ° C per hour to a heating temperature from 1000 to 1100 ° C.