1. A. K. Mallik and D. Basu
Central Glass and Ceramic Research Institute, Kolkata
Effect of processing technologies on grain size and mechanical properties of Alumina
INTRODUCTION
MATERIALS & METHODS
SEM micrographs of samples HIPed at 1475
GRANULATION
CIP
(200–300 MPa)
GREEN MACHINING
MACHINING
SINTERING
Alumina + BINDER
Hot Iso-static Pressing
Alumina ceramics have been used as femoral heads and acetabular cup components since 1970s. There are reports of ceramic knee trials by Japanese researcher in the beginning of The ceramic HIP is used for two types of arthroplasty, a) Ceramic on Polymer and b) ceramic on ceramic. In ceramic on polymer (UHMWPE) type, the femoral head is made up of alumina and the acetabular cup component is Ultra High Molecular Weight Poly-ethylene but in the second case (ceramic total HIP) both of the components are made up of alumina ceramics. After successful technology transfer of ceramic-on-polymer HIP joint from our group, mechanical behavior of state of the art ceramic-on-ceramic HIP joints is being investigated because of its better wear properties. On the other hand ceramic femoral condyles for total knee replacements have been successful in Japan. There are more applications of alumina ceramics in biomedical field, like in spine replacement.
REMOVING BINDER
CONCLUSIONS
CGCRI – Avure Model #
Max. Working Pressure MPa
Working Zone Dimensions (Diameter x Length, mm.)
Approx. Unit Weight (kg)
Maximum Working Temperature oC
Molybdenum
Graphite
QIH-6
30,000
110 x 220
120 x 240 25
2000
Success of Hot Iso-static Processing(HIP)
over conventional
route for medical grade Al2O3
LITERATURE
Properties
ISO Specification
CGCRI
Conventional HIPed
Density, g/c.c.
> 3.90
>3.96
Chemical Composition
Alumina > 99.5 %
Alumina ~ 99.7 %
Alumina ~ 99.9%
Micro-hardness (Vickers’), GPa
20.0
> 20.0
> 21
Compressive Strength MPa
4000
> 4000
Flexural Strength, MPa
400
~ 400
543.5
Young’s modulus, GPa
> 350
Wear resistance [alumina pin against polished alumina disc with contact pr. of 5 MPa in distilled water medium], mm3/hr
< 0.01
< 0.005
~ 0.005
Coefficient of friction (Contact pr. – 5.0 MPa, Medium – Distilled water)
< 0.30
< 0.20
~ 0.2
Surface finish (Ra), m
< 0.05
High-tech aluminas are used as load bearing implants in biomedical application, e.g. ceramic femoral head and acetabular cup in HIP joints; Ceramic knee. But there are chances of failure of these implants. The majority load bearing implant fails due to fatigue and wear. Fatigue and wear properties are material as well as design dependant. Newer design and improved material property are keys for success of these implants.
Following table shows improvement of material property over decades
RESULTS
Comparison of Mechanical Properties of HIPed Alumina by Avure QIH - 6
Sample
Grain Size
microns
Sintered
2 hrs at
(oC)
HIPed
30 min 200 MPa
at (oC)
Youngs’ Modulus ( GPa)
Flexure
( 3 pt )
(MPa)
Density
HV(0.2gf)
15 sec C
1550
1475
398.82
578.91
3.9613
1996
2 C
1540
393.01
531.66
3.9532
1957
3 F
401.71
467.55
3.9735
2172
~ 2 & ~ 5
1520
398.78
508.87
3.9741
1881
~ 6
405.34
381.98
3.9700
2029
Literature
1600 NO
380
500
3.96
1900
Properties
1970s
1980s
1990s
Bending Strength, MPa
400
500
580
Compressive Strength, MPa
>4000
Fracture Toughness, MP.m1/2 4
Vickers hardness, HV
1800
1900
2000
Grain Size, microns
4.5
3.2
1.8
Density, gm/cc
3.94
3.96
3.98
Young’s Modulus, GPa
380
Hot isostatic pressed NO
YES
Suitable for ceramic-on-ceramic
Achievements
Denser Ceramic
Higher Hardness
Higher Flexural Strength
Higher Young’s Modulous
Future Goal
Fabrication of Medical devices
based on new processing technique - HIP
K1c = (E / H)1/2 P . C -3/2 = 2.56 MPa . m1/2
K1c = 3.3 MPa . m1/2
Optical Micrograph of Vickers Indentation
REFERENCES
Rietveld Analysis
Rahaman et al J. Am. Ceram. Soc., 90 [7] 1965–1988 (2007)
D. Basu et al, J. Am. Ceram. Soc., 90 [9] 2987–2991 (2007)
D. Basu, Sadhana, 28 ( 2003) 3 & 4,
Values of Cell parameters, crystallite size and strain obtained by Reitveld Analysis
ACKNOWLEDGEMENT
Sample
Alumina
a (Å)
c (Å)
Volume
( A 3 )
Crystallite Size ( nm )
Strain (%)
Coarse Grain
8.1151
949.79
162.13
0.003
Fine Grain
6.7346
407.91
60.78
0.223
Dr. H. S. Maiti, Director, CGCRI
Dr. D. K. Bhattacharya, Head, Composite Division, CGCRI
Dr. Suchitra Sen, Head, SEM-ESCA section
Head, XRD section