Title : Sintering Behaviour of Cerium-doped Hydroxyapatite Bioceramics

FINAL YEAR PROJECT 1(Semester2, Academic Year 2007/2008)

Prepared by:KELVIN HOH CHEE WAI (ME075719)

Department of Mechanical EngineeringUniversiti Tenaga Nasional (UNITEN)Project Supervisor:

Assoc. Prof. Ir. Dr. Ramesh Singh

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OBJECTIVE

To investigate the effects of adding small amounts of Cerium Oxide (CeO2) on the sinterability of nanocrystalline HA powder.

METHODOLOGY

Literature Review

Report preparation & presentation

Powder Characterization

Mechanical Testing & Evaluation

Preparation of Cerium-dopedHA powder

Body Preparation

Consolidation Process

FYP 1

FYP 2

INTRODUCTION

�What is Hydroxyapatite?

It is the most suitable ceramic material for hard tissue replacement implant from the point of view of Biocompatibility.

It has the chemical similarity with the mineral portions of hard tissue.(e.g. Calcium + Phosphorus)

Chemical formula: Ca10(PO4)6(OH)2

�Why Hydroxyapatite is being developed?

Metallic materials have various problems to be used as implant.(e.g. negative tissue reaction, wear and corrosion.)

Zirconia (ZrO2) and Alumina (Al2O3) belong to Bioinert materials.

Table 1 :Table 1 :Typical Properties of Bioceramics

The Limitation of HydroxyapatiteThe Limitation of Hydroxyapatite

How to improve the Hydroxyapatite?

Control of sintering temperature & atmosphere.

Manipulation of processing parameters.

Addition of additives (dopants) into the HA powder.

Ideal Sintering Additive (dopant)

Aid densification of HA without decomposition.

No effect on Biocompatibility & Bioactive phases.

Control of grain size.

Improve the mechanical properties.

X-ray Diffractometer (XRD)

1250C

1400C

1450C

-TCP

-TCP CaOTTCP

Scanning Electron Microscope (SEM)

Hall-Petch Equation

d

k yOY

d

k yOY

d

k yOY

d

k yOY

Where,ky = material constantóo = starting stress for dislocation movementd = grain diameter (m)óy = Fracture strength

Fracture Toughness vs Porosity

Vickers Hardness vs Sintering Temperature

CONCLUSIONS

Hydroxyapatite is suitable for fabricating the artificial teeth & bone due to its excellent biocompatibility.

Improvement on Fracture Toughness & Young�s Modulus is needed.

Cerium was found that it decreases the crystal�s size of the HA.

Stoichiometric

The stoichiometric Ca/P ratio of HA : 1.67

Calcium Oxide (CaO) forms if Ca/P : >1.67

-TCP and -TCP forms : <1.67(Tricalcium Phosphate)