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Surface modification of hydroxyapatite. Part II. Silica
1Biomimetics, Orthopedics, and Nanomaterials Exploration (BONE) Lab, Department of Materials and Nuclear Engineering, University of Maryland, 20742, College Park, MD, USA.
Biomaterials
|June 24, 2003
Summary
Silica coating on nanophase hydroxyapatite (HAP) particles was achieved. Optimal silica coating enhanced particle stability and surface area, with potential applications in material science.
Area of Science:
- Materials Science
- Nanotechnology
- Biomaterials
Background:
- Hydroxyapatite (HAP) is a key biomaterial, but its surface properties can be modified for enhanced functionality.
- Coating HAP with silica offers a route to tune its characteristics, potentially improving its performance in various applications.
Purpose of the Study:
- To synthesize and characterize silica-coated nanophase hydroxyapatite (HAP) particles.
- To investigate the effect of varying silica coating amounts on HAP particle properties.
- To understand the coating mechanism and its impact on particle stability and surface area.
Main Methods:
- Synthesis of silica-coated HAP via tetraethyl orthosilicate hydrolysis.
- Characterization using transmission electron spectroscopy, XRD, DRIFTS, BET surface area analysis, sedimentation, acid dissolution, and zeta potential measurements.
- Analysis of spectral changes, surface area variations, and dissolution behavior with increasing silica content.
Main Results:
- DRIFTS confirmed successful silica coating, showing decreased HAP features and increased silica features.
- Specific surface area showed a non-systematic increase with silica coating, peaking at 93 m²/g for 25wt% silica, and reaching 138 m²/g for 75wt% silica.
- A decrease in surface area at 50wt% silica indicated complete surface coverage, correlating with enhanced resistance to acid dissolution.
Conclusions:
- Heterocoagulation of silica clusters (approx. 14nm) onto HAP particles explains the observed surface area behavior.
- Optimal silica coating (around 50wt%) provides a stable, complete surface layer, enhancing particle resistance to acidic environments.
- Acid treatment of coated particles resulted in the formation of calcium chloride phosphate hydrate.
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