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THERMAL OXIDATION OF TITANIUM
FOR IMPROVED MEDICAL IMPLANT
OSSEOINTEGRATION
Melanie Hamilton
NSF REU
Advisor: Dr. Cortino Sukotjo
Mentors: Arman Butt and Sweetu Patel
University of Illinois at Chicago
IMPLANT OSSEOINTEGRATION
Implants improve quality of life
 Implants require bone-implant
connection to be successful


Osseointegration
Bone
Implant
R. Van Noort: Journal of Materials Science, 1987, 22, 3801-3811.
http:/www.minuksmile.com/sosimages/cases_missing_teeth10.jpg
TITANIUM

Has many characteristics that enhance
osseointegration and are functional for dental use






Biocompatibility
Low density
High ductility
Corrosion resistance
Mechanical resistance
Ti-6Al-4V  alloy with increased mechanical
resistance
R. Van Noort: Journal of Materials Science, 1987, 22, 3801-3811.
SURFACE MODIFICATION

Creating a micro-rough
surface improves
osseointegration by
increasing surface area

Renfert Sandblaster
Sandblasting and acid
etching
Rough Surface

Adding an oxide layer
Increases biocompatibility
and corrosion resistance
 Purpose: Optimize oxide
layer functionality

E. Nasatzky, B. Boyan and Z. Schwartz: The Alpha Omegan, 2005, 98, 9-19.
L. H. Li et al.: Biomaterials, 2004, 25, 2867-2875.
Rat implant
J. Pouilleau et al.: Materials Science and Engineering, 1997, B47,
235-243.
Cells
ANATASE/HYDROXYAPATITE



When annealed at certain
temperatures, TiO2 has anatase
crystal structure
Anatase crystal structure is
similar to hydroxyapatite
Hydroxyapatite is a natural
bone growth mineral
M. Hirota et al.: Int. J. Oral Maxillofac. Surg., 2012, article in press.
M. Uchida et al.: J. Biomed. Mater. Res., 2002, 64A, 164-170.
Ti
TiO2 amorphous nanotubes
TiO2 anatase nanotubes
S. Oh et al.: Wiley Periodicals, Inc. J.
Biomed. Mater. Res., 2006, 78A, 97-103.
HYDROXYAPATITE VS. ANATASE
Superlattice:
Apatite: Xap = 9.42 Å
Anatase: Xan = 9.51 Å
Rutile: Xru = 9.19 Å
Apatite
Rutile
Anatase
Masaki Uchida, et. al.: J. Biomed. Mater. Res., 2003, 64, 164-70.
ADVANTAGES OF THERMAL OXIDATION
Oxide layer thickness is affected by time,
temperature, and pressure
 Conformal (better than CVD & PVD)
 Time efficient – Example: 30 nm oxide layer:

ALD (0.3 Å/cycle/min)  15 hours
 Thermal oxidation (550 oC)  1 hour


No precursor (Unlike CVD, PVD, & ALD)
Lower impurities
 Lower cost

CVD – Chemical Vapor Deposition
PVD – Physical Vapor Deposition
ALD – Atomic Layer Deposition
Rajesh Katamreddy, et. al.: The Electrochemical Society, 2008, 16(4), 113-122.
D. Velten, et. al. Journal of Biomedical Materials Research, 2001, 59, 18-28.
THERMAL OXIDATION SCHEMATIC
O2
http://www.eng.tau.ac.il/~yosish/courses/vlsi1/I-4-1-Oxidation.pdf
EXPERIMENT

Thermal oxidation
Atmospheric pressure
 Atmospheric air
 Constant time (5 hours)
 Changing temperatures
Thickness of oxide layers of Ti6A14V after
thermal oxidation as a function of temperature
and time measured by means of ellipsometry.
600 oC


Four temperatures
550 oC
Velten, D. et. al.: Journal of Biomedical Materials Research, 2002, 59, 18–28.
24 oC expected to be amorphous
 300 oC, 375 oC, 450 oC expected to contain anatase



Research shows anatase forms around 250 C – 600 C
Goal: Determine temperatures at which anatase can be
detected and characterize the resulting oxide layers with
Ellipsometry, Goniometer, and FTIR.
H. Tang et. al.: Journal of Applied Physics, 1994, 75, 2042-2047.
E. Gemelli and N.H.A. Camargo: Revista Matéria, 2007, 12, 525-531.
Thermocouple
Air flow
Ti-6Al-4VSample
Due to fan, only one sample
can be done at a time
CHARACTERIZATIONS

Ellipsometry (smooth sample)



Color Characterization


Relates color of oxide layer to TiO2 thickness
WCA – Water Contact Angle





Unsuccessful due to surface roughness
Need smoother and flatter samples
Güleryüz, H. and Çimenoğlu, H.: Biomaterials, 2004, 25, 3325-3333.
Measures hydrophilicity
Surface roughness increases with oxidation temperature
Roughness improves hydrophilicity which improves osseointegration
Higher temperature  Increased hydrophilicity
FTIR – Fourier Transform Infrared Spectroscopy (smooth sample)
Determines chemical composition
 Crystalline phase (anatase to rutile)

B.E. Deal and A.S. Grove: J. Appl. Phys., 1965, 36, 3770-3778.
Kangarlou, H. and Rafizadeh, S.: Proceedings of the World Congress on
Engineering. International Association of Engineers. Volume 2. 2011
COLOR CHARACTERIZATION
Temp (oC)
24
Color
Estimated
TiO2
Thickness
(nm)
300
375
450
525
600
None None
Slight
Gold
Golden
Yellow
PurpleBlue
<10
10<x<25
10<x<25
80<x<120 150<x<180
<10
Thermally oxidized for 5 hours
Color vs. Oxide Thicknes from D. Velten, et. al.
O. Untracht. “Jewelry Concepts and Technology”; Doubleday: Garden City,
New York, 1982, 723-730.
D. Velten, et. al.: Journal of Biomedical Materials Research, 2002, 59, 18–28.
WCA – WATER CONTACT ANGLE
90
Smooth Samples
W
C
A
d
e
g
r
e
e
s
80
Rough Samples
70
60
50
40
30
20
10
0
24
300
375
450
Temperature of Oxidation (Celcius)


Roughness was affected by temperature on sandblasted surfaces
(more than smooth surface)
At high temperatures (450 oC) rough samples are more hydrophilic
FTIR – FOURIER TRANSFORM INFRARED SPECTROSCOPY
525 oC
600 oC
375 oC
450 oC
300 oC
1 200
1 000
8 00
6 00
W av e num be rs (c m-1 )
Black = 600 oC Green = 525 oC
Red = 450 oC Magenta = 375 oC Blue = 300 oC
FTIR – FOURIER TRANSFORM
INFRARED SPECTROSCOPY
CO2 667 cm-1
Anatase – 870 cm-1
Rutile – 830 cm-1
Black 600 oC = 831 cm-1
Green 525 oC = 838 cm-1
Red 450 oC = 847 cm-1
Magenta 375 oC = 854 cm-1
Blue 300 oC = 859 cm-1
TiO2 420-460 cm-1
Anatase
550 cm-1
~859 cm-1
1 000
8 00
6 00
W av e num be rs (c m-1 )
D. Velten, et. al.: Journal of Biomedical Materials Research, 2002, 59, 18–28.
CONCLUSIONS



Anatase exists in the range 300-450oC as the primary
crystalline structure
Oxide thickness increases with increasing
temperature
Successful optimization of furnace

Expectations were met
FUTURE WORK




Test more samples and temperatures
Obtain more accurate thickness measurements
Possibly test with XRD – X-Ray Diffraction
Santiago Tovar will continue with cell culture assay

Will relate these characterizations to cell assay results
ACKNOWLEDGEMENTS
Dr. Christos Takoudis
Dr. Gregory Jursich
Dmitry Royhman
Santiago Tovar
Special Thanks to the National Science Foundation
EEC-NSF Grant # 1062943
Questions?

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