Amorphorization and recrystallization during plasma spraying of hydroxyapatite

Area of Science:

• Materials Science
• Crystallography
• Surface Engineering

Background:

• Hydroxyapatite coatings are crucial in biomedical applications for bone regeneration.
• Understanding the relationship between coating thickness and material properties is essential for optimizing performance.
• Crystallite size and crystallinity significantly impact the mechanical and biological behavior of hydroxyapatite.

Purpose of the Study:

• To investigate how the thickness of hydroxyapatite coatings affects their mean crystallite size and crystallinity.
• To determine the influence of cooling rates on the microstructural evolution of hydroxyapatite coatings.
• To identify the critical thickness for recrystallization in hydroxyapatite coatings.

Main Methods:

• X-ray diffraction (XRD) was employed to analyze the structural characteristics of hydroxyapatite coatings.
• Coating thickness was systematically varied to observe its impact on crystallographic parameters.
• Microstructural analysis focused on mean crystallite size and overall crystallinity.

Main Results:

• A decrease in mean crystallite size was observed with increasing coating thickness.
• Conversely, crystallinity of the hydroxyapatite coatings increased with greater thickness.
• A critical thickness (rc) of approximately 20 microns was identified as the point where recrystallization becomes significant.

Conclusions:

• Coating thickness is a critical factor controlling the microstructure of hydroxyapatite.
• Slower cooling rates in thicker coatings facilitate recrystallization, enhancing crystallinity.
• The findings provide insights into tailoring hydroxyapatite coating properties for specific applications.