18-01-2013, 04:35 PM
A review of plasma-assisted methods for calcium phosphate-based coatings fabrication
[attachment=47601]
introduction
Metalic implants disadvantages corrosion and wear in biological environments resulting in ions release and accumulation of wear debris, poor implant fixation owing to the lack of osteoconductivity and osteoinductivity, and infections due to bacterial adhesion and colonization at the implantation site
hydroxyapatite (HA) is a naturally occurring mineral form of calcium apatite with the formula Ca5(PO4)3(OH), but is usually written Ca10(PO4)6(OH)2
Up to 50% of bone by weight is a modified form of hydroxylapatite (known as bone mineral).
plasma-assisted techniques
U.S. Food and Drug Administration (FDA) and the International Organization for Standardization (ISO)
Plasma processes allow adjusting surface properties of solids with negligible effect on their bulk
Plasmabased technology is very promising as it can modify the surface properties, even creating a nano-sized surface topography
The reasons of coatings stoichiometry deviation
The sputtering of a multicomponent target .
The components of target may not be completely transferred owing to the low pressure.
type of sputtering system and the deposition parameters.
preferential deposition of Ca ions and loss of phosphorus ions (pumped away before reaching the substrate or be re-sputtered out of the growing film by incoming ions or neutrals).
Different sputtering rates for calcium and phosphorus at the target.
target processing that alters the target stoichiometry and difference in sputtering rate of components.
Raised annealing temperature.
maintain the integrity of CaP coatings
Annealing in situ at 350–650 °C, or after deposition, in an inert gas, water vapor, air or vacuum enhances the films crystallinity
laser treatments for increasing the HA crystallinity
hydrothermal treatment(post-treating by water vapor (WVT))
electric polarization in alkaline solution (PAS)
right angle RF magnetron sputtering
presence of water vapor in the LPS (suppress the dehydroxylation in the high temperature plasma jet)
KrF laser fluences in PLD
two excimer lasers (ablation, irradiate a substrate)
supersonic plasma nozzles
Substitution of the hydroxyl ion by fluoride (in the HA lattice renders the CaP thermally more stable)
addition of magnesium into HA improves the crystallinity
The lower is the H2 flux, the higher is the crystallinity and the lower CaO content
[attachment=47601]
introduction
Metalic implants disadvantages corrosion and wear in biological environments resulting in ions release and accumulation of wear debris, poor implant fixation owing to the lack of osteoconductivity and osteoinductivity, and infections due to bacterial adhesion and colonization at the implantation site
hydroxyapatite (HA) is a naturally occurring mineral form of calcium apatite with the formula Ca5(PO4)3(OH), but is usually written Ca10(PO4)6(OH)2
Up to 50% of bone by weight is a modified form of hydroxylapatite (known as bone mineral).
plasma-assisted techniques
U.S. Food and Drug Administration (FDA) and the International Organization for Standardization (ISO)
Plasma processes allow adjusting surface properties of solids with negligible effect on their bulk
Plasmabased technology is very promising as it can modify the surface properties, even creating a nano-sized surface topography
The reasons of coatings stoichiometry deviation
The sputtering of a multicomponent target .
The components of target may not be completely transferred owing to the low pressure.
type of sputtering system and the deposition parameters.
preferential deposition of Ca ions and loss of phosphorus ions (pumped away before reaching the substrate or be re-sputtered out of the growing film by incoming ions or neutrals).
Different sputtering rates for calcium and phosphorus at the target.
target processing that alters the target stoichiometry and difference in sputtering rate of components.
Raised annealing temperature.
maintain the integrity of CaP coatings
Annealing in situ at 350–650 °C, or after deposition, in an inert gas, water vapor, air or vacuum enhances the films crystallinity
laser treatments for increasing the HA crystallinity
hydrothermal treatment(post-treating by water vapor (WVT))
electric polarization in alkaline solution (PAS)
right angle RF magnetron sputtering
presence of water vapor in the LPS (suppress the dehydroxylation in the high temperature plasma jet)
KrF laser fluences in PLD
two excimer lasers (ablation, irradiate a substrate)
supersonic plasma nozzles
Substitution of the hydroxyl ion by fluoride (in the HA lattice renders the CaP thermally more stable)
addition of magnesium into HA improves the crystallinity
The lower is the H2 flux, the higher is the crystallinity and the lower CaO content