AP13068451 "Obtaning multifunctional calcium-phosphate coatings with titanium dioxide nanoparticles by plasma-electrolytic oxidation"

Supervisor: Aldabergenova Tamara Mustafaevna, PhD, - Project Manager ORCID ID-6506076753

Relevance:

In particular, commercial pure titanium and its alloys are widely used for dental implant applications due to their good mechanical properties, excellent corrosion resistance in biological fluids, and very low toxicity. Despite their attractive properties, implants made of Ti and its alloys usually exhibit low resistance to mechanical stress and aggressive environments that exist in the implant environment, and can be destroyed with simultaneous wear and corrosion. Recently, the plasma electrolytic oxidation (PEO) process has attracted considerable interest as a cost-effective, environmentally friendly, and highly efficient technology for depositing porous, wear- and corrosion-resistant ceramic films on Ti surfaces. Bioactive ceramics based on hydroxyapatite and calcium phosphates are promising due to their biocompatibility and similarity in composition to bone tissue. However, calcium phosphate PEO coatings exhibit poor tribological properties such as high and unstable coefficients of friction and low fretting wear resistance. Therefore, the inclusion of nano- and microparticles in the composition of coatings is considered as the most important strategy for improving the properties of PEO-coatings and expanding the range of their chemical composition.

Target:

Obtaining multifunctional calcium-phosphate PEO-coatings with TiO2 nanoparticles, having high corrosion and tribological characteristics and studying the features of degregation of their structure and properties under the synergistic effects of wear and corrosion.

Expectation:

1. On the basis of complex experimental studies, multifunctional coatings for implants will be obtained with high corrosion and tribological characteristics.
2. An installation for plasma-electrolytic oxidation will be created.
3. The effect of PEO technological parameters (voltage, current density, electrolyte flow rate, electrolyte temperature) on the elemental composition of the coatings will be studied.
4. A series of experiments will be carried out to obtain calcium phosphate PEO coatings with different content of TiO2 nanoparticles.
5. The optimal concentration of TiO2 nanoparticles in calcium phosphate PEO coatings will be determined, which is necessary to improve their corrosion and tribological characteristics and is safe for living organisms.
6. The features of degradation of the surface of bioactive calcium phosphate coatings with TiO2 nanoparticles under the combined effect of corrosion and wear in special solutions will be studied.
7. The role of TiO2 nanoparticles in improving the performance of bioactive calcium phosphate PEO coatings will be revealed.

Result:

The coatings were applied by the MAO method using a KP-HI-F-40A600V pulse rectifier power source. The surface morphology was examined using a JSM-6390 LVJEOL low-vacuum scanning electron microscope. The coating roughness was measured using a model 130 profilometer. The samples were tested for microhardness using a FISCHERSCOPE HM2000. An Anton Paar TRB3 tribometer was used for tribological tests. The tribological tests were carried out under the following conditions: load up to 3 N, speed – 2.5 cm/s, radius – 2 mm, radius of the ball (Si3N4 counterbody) – 3 mm. The parameters of the MAO process for this work included the following limits: pulse duration - 100 μs, pulse frequency - 100 Hz, process duration - 10 min, electric voltage - 300 V. The microarc oxidation method was used to obtain MAO coatings on the titanium surface in the anodic mode for 10 minutes in various electrolytes based on phosphoric acid, sodium orthophosphate, potassium hydroxide (KOH) and hydroxyapatite (HA). In accordance with the object of study, three different electrolyte compositions were selected:

No. 1 - Na2HPO4 (6 g), HA (2 g), KOH (2 g);
No. 2 - H3PO4 (15%), HA (2 g), CaCO3 (5 g);
No. 3 - Na3HPO4 (5 g), HA (3 g), CaCO3 (5 g).
As a result of measuring the friction coefficient for the first electrolyte, it was µ=0.109, for the second µ=0.133 and for the third µ=0.532, while for the original titanium without coating – µ=0.773. A study of the microphotograph of the cross-section of the MAO coatings showed that the coating thickness can vary from 23 µm to 52 µm, the roughness varied from 2.96 µm to 3.96 µm; Using the microarc oxidation method, coatings of titanium dioxide TiO2 in the modification of rutile and anatase were obtained on the titanium surface. The results of the studies revealed that the coatings formed in the Na2HPO4+GA+KOH electrolyte have a low dry friction coefficient (Si3N4 counterbody) by approximately 6 times and a high microhardness value by 2 times, compared to the
coatings obtained with H3PO4+GA+CaCO3 and Na3HPO4+GA+CaCO3 electrolytes. The morphology of the coating surface (size, number of pores, presence of cracks) formed by the MAO method depends on the composition of the electrolyte and the substrate. However, all MAO coatings are characterized by the presence of pores, which are channels for electrical breakdowns and a consequence of the release of gas bubbles to the surface. Analysis of the images of the surface of samples with coatings formed in electrolytes of various compositions, obtained using SEM, showed that the most porous surface of all the studied coatings are those formed in an electrolyte with the addition of potassium hydroxide (KOH). This result can be explained by the fact that adding KOH to the electrolyte and increasing the current density contribute to an increase in the intensity of the gas evolution process during MAO. It should be noted that an alkaline environment is necessary for the stability of the electrolyte, the required pH of which is usually created using potassium hydroxide KOH or sodium NaOH. Calcium phosphate coatings with the addition of various concentrations of titanium dioxide (TiO2) nanoparticles were successfully obtained using plasma electrolytic oxidation (PEO). Microhardness tests were carried out on coatings with various concentrations (0.5 g, 0.75 g, 1 g) of TiO2. It was found that the addition of TiO2 nanoparticles significantly increases the hardness of calcium phosphate coatings. The maximum
increase in hardness is observed at a concentration of 0.75 g TiO2 nanoparticles, which was revealed during the experiments. Optimum concentrations of TiO2 nanoparticles in PEO coatings that are safe for living organisms were experimentally determined.
The results of the study showed that the addition of TiO2 nanoparticles to calcium phosphate coatings can significantly improve their mechanical properties, provided that the optimal concentrations are observed. It was found that coatings with low and medium TiO2 concentrations demonstrate high biocompatibility. High TiO2 concentrations have a negative effect on biocompatibility, reducing its indicators. Calcium phosphate PEO coatings with different concentrations of TiO2 nanoparticles (0.5 g, 0.75 g and 1.0 g) were applied to titanium disks. Samples were sterilized by autoclaving at 121 °C for 20 minutes. Osteoblast cell lines were used to assess cytotoxicity. Cells were cultured on the coating surface and incubated for 24, 48 and 72 hours. MTT reagent was added to the cells cultured on the coated samples. After incubation, formazan was dissolved in DMSO and the optical.

2023

  • Байжан, Д. Р., Рахадилов, Б. K., Алдабергенова, Т. М., Баятанова, Л. Б., Курбанбеков, Ш. Р., & Буйткенов, Д. Б. (2023). Obtaining of calcium-phosphate coatings on the titanium surface by micro-arc oxidation. Eurasian Physical Technical Journal, 20(1 (43)), 34-41. https://doi.org/10.31489/2023No1/34-41
  • Bayatanova, L. B., Zhassulankyzy, A. Z., Magazov, N. M., Rakhadilov, B. K., Muktanova, N., & Uazyrkhanova, G. K. (2023). Effect of plasma-electrolytic oxidation on mechanical properties of titanium coatings. Bulletin of the Karaganda University" Physics Series", 111(3), 65-74. https://doi.org/10.31489/2023ph3/65-74

2024

  • Rakhadilov B., Zhassulan A., Baizhan D., Shynarbek A., Ormanbekov K., Aldabergenova, T. The effect of the electrolyte composition on the microstructure and properties of coatings formed on a titanium substrate by microarc oxidation //AIMS Materials Science. – 2024. – Т. 11. – №. 3. – С. 547-564. https://doi.org/10.3934/matersci.2024027

Study Team Members

  • Fullname: Касымов Аскар Багдатович, PhD

    Scopus Id: 56298368800

    Researcher Id: ---

    ORCID: 0000-0002-1983-6508

    Additionally:

  • Fullname: Кожанова Рауан Сабырбековна

    Scopus Id: 57216911622

    Researcher Id: ---

    ORCID: 0000-0002-3271-226_

    Additionally:

  • Fullname: Байжан Дарын Рашитұлы

    Scopus Id: 57214891142

    Researcher Id: ---

    ORCID: 0000-0002-9105-3129

    Additionally:

  • Fullname: Магазов Нуртолеу Магзумбекович

    Scopus Id: 57220041350

    Researcher Id: ---

    ORCID: 0000-0002-9941-9199

    Additionally: