THERMAL OXIDATION OF TITANIUM FOR IMPROVED MEDICAL IMPLANT OSSEOINTEGRATION
Melanie HamiltonNSF REUAdvisor: Dr. Cortino SukotjoMentors: Arman Butt and Sweetu PatelUniversity of Illinois at Chicago
IMPLANT OSSEOINTEGRATION Implants improve quality of life Implants require bone-implant
connection to be successful Osseointegration
R. Van Noort: Journal of Materials Science, 1987, 22, 3801-3811. http:/www.minuksmile.com/sosimages/cases_missing_teeth10.jpg
Bone
Implant
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 Sandblasting and acid
etching
Adding an oxide layer Increases biocompatibility
and corrosion resistance Purpose: Optimize oxide
layer functionality
L. H. Li et al.: Biomaterials, 2004, 25, 2867-2875. E. Nasatzky, B. Boyan and Z. Schwartz: The Alpha Omegan, 2005, 98, 9-19. J. Pouilleau et al.: Materials Science and Engineering, 1997,
B47, 235-243.
Rough Surface
Renfert Sandblaster
Rat implant
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. Uchida et al.: J. Biomed. Mater. Res., 2002, 64A, 164-170. M. Hirota et al.: Int. J. Oral Maxillofac. Surg., 2012, article in press.
S. Oh et al.: Wiley Periodicals, Inc. J. Biomed. Mater. Res., 2006, 78A, 97-103.
Ti
TiO2 amorphous nanotubes
TiO2 anatase nanotubes
Cells
HYDROXYAPATITE VS. ANATASE
Masaki Uchida, et. al.: J. Biomed. Mater. Res., 2003, 64, 164-70.
Rutile
Apatite
Anatase
Superlattice:Apatite: Xap = 9.42 ÅAnatase: Xan = 9.51 ÅRutile: Xru = 9.19 Å
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
DepositionPVD – Physical Vapor DepositionALD – 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
http://www.eng.tau.ac.il/~yosish/courses/vlsi1/I-4-1-Oxidation.pdf
O2
EXPERIMENT Thermal oxidation
Atmospheric pressure Atmospheric air Constant time (5 hours) Changing temperatures
Four temperatures 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.
Thickness of oxide layers of Ti6A14V after thermal oxidation as a function of temperature and time measured by means of ellipsometry.
Velten, D. et. al.: Journal of Biomedical Materials Research, 2002, 59, 18–28.
E. Gemelli and N.H.A. Camargo: Revista Matéria, 2007, 12, 525-531.
550 oC
600 oC
H. Tang et. al.: Journal of Applied Physics, 1994, 75, 2042-2047.
Ti-6Al-4VSample
Thermo-couple Air flow
Due to fan, only one sample can be done at a time
CHARACTERIZATIONS Ellipsometry (smooth sample)
Unsuccessful due to surface roughness Need smoother and flatter samples
Color Characterization Relates color of oxide layer to TiO2 thickness
WCA – Water Contact Angle 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)
Kangarlou, H. and Rafizadeh, S.: Proceedings of the World Congress on Engineering. International Association of Engineers. Volume 2. 2011B.E. Deal and A.S. Grove: J. Appl. Phys., 1965, 36, 3770-3778.
Güleryüz, H. and Çimenoğlu, H.: Biomaterials, 2004, 25, 3325-
3333.
COLOR CHARACTERIZATION
O. Untracht. “Jewelry Concepts and Technology”; Doubleday: Garden City, New York, 1982, 723-730.
Temp (oC) 24 300 375 450 525 600
Color None
None Slight Gold
Golden Yellow Purple-Blue
EstimatedTiO2Thickness (nm)
<10 <10 10<x<25
10<x<25 80<x<120
150<x<180
D. Velten, et. al.: Journal of Biomedical Materials Research, 2002, 59, 18–28.
Color vs. Oxide Thicknes from D. Velten, et. al.
Thermally oxidized for 5 hours
WCA – WATER CONTACT ANGLE
Roughness was affected by temperature on sandblasted surfaces (more than smooth surface)
At high temperatures (450 oC) rough samples are more hydrophilic
24 300 375 4500
10
20
30
40
50
60
70
80Smooth Samples
Rough Samples
Temperature of Oxidation (Celcius)
WCA degrees
600 800 1000 1200 Wavenumbers (cm-1)
FTIR – FOURIER TRANSFORM INFRARED SPECTROSCOPY
525 oC
375 oC
450 oC
300 oC
600 oC
Black = 600 oC Green = 525 oC Red = 450 oC Magenta = 375 oC Blue = 300 oC
FTIR – FOURIER TRANSFORM INFRARED SPECTROSCOPY
600 800 1000 Wavenumbers (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
~859 cm-1
CO2 667 cm-1
Anatase 550 cm-1
TiO2 420-460 cm-1
Anatase – 870 cm-1
Rutile – 830 cm-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
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
FUTURE WORK
Special Thanks to the National Science FoundationEEC-NSF Grant # 1062943
Questions?
ACKNOWLEDGEMENTSDr. Christos TakoudisDr. Gregory Jursich
Dmitry RoyhmanSantiago Tovar
