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Investigation Into The Powder Production And Application Of Hydroxyapatite HAp Used In Femoral Impla

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Title: Investigation Into The Powder Production And Application Of Hydroxyapatite HAp Used In Femoral Impla


1
Investigation Into The Powder Production And
Application Of Hydroxyapatite (HAp) Used In
Femoral ImplantsSharon Kehoe, Dr. Joseph Stokes
and Dr. Lisa LooneyMaterials Processing Research
Centre, Dublin City University, Dublin 9,
IrelandNational Centre for Plasma Science
Technology, Dublin City University, Ireland
Introduction Hydroxyapatite (HAp) and other
related calcium phosphate minerals have been
utilized extensively as implant materials for
many years due to their identical chemical
composition and high biocompatibility with
natural bones, skin and muscle tissues. HAp,
chemical formula Ca10(PO4)6(OH)2, is the main
mineral constituent of teeth and bones. HAp
ceramics do not exhibit any cytotoxic effects and
can directly bond to bone. Thermal spray
processes have been frequently used to deposit
functionally biomedical active coatings, such as
HAp onto prosthetic implants, but the occurrence
of several poor performances has generated
concerns over the consistency and reliability of
thermally sprayed HAp coatings. Recent
investigations using HAp coatings have shown that
process related variability has significant
influence on coating characteristics such as
phase composition, structure and chemical
composition and performance such as
bioresorption, degradation and bone apposition.
Variation in process parameters such as powder
morphology can induce microstructural and
mechanical inconsistencies that have an effect on
the service performance of the coatings.
Synthesis of Hydroxyapatite
1. Orthophosphoric Acid Dip (Precipitation
Method) Calcium Hydroxide distilled water mixed
for 24h Orthophosphoric acid is added drop wise
via aperistaltic pump _at_ 2 litres per minute for
24h Precipitate left to mix for 2
days Temperature of 40C and Ca/P ratio of 1.667
used
4. Ball Milled Agglomerated powder leaves
furnace Milling media (porcelain balls) are
required to break down powder Finally sieved by
hand to separate powder and media (2 days per
batch)
2. Drying Oven Assay dried for 1h Infra-red light
sometimes used
3. Furnace Crcucibles placed in a furnace for 4h
at 1210C Mortar used to grind samples into fine
powder
Addition of Lubricant Binder
5. Spray Dryer Atomisation occurs as slurry is
pumped through peristaltic pump Slurry pumped
upwards as it is dried by gas burner The
resulting powder falls into a collection and is
extracted through a cyclone
8. V Blender The small and medium particles are
blended together again Rotation occurs for 2h
7. Sweco and Feeder Powder placed in a furnace
for 4h at 1200C Powder then fed into Sweco at a
very slow rate which separates powder into 3
different particle sizes
Project Aims The aim of the project will be to
identify the FDA standards and compare the
differences between these standards and the
results found from the HAp powder produced in
Ireland. An experimental matrix will be designed
to correct the difference in order to yield an
approved HAp powder, which can be utilised on the
femoral implant.
9. Final Preparation/Plasma Thermal Sprayed onto
Implant
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