oral presenation - paulo cesar - oklahoma and boston in march 2015
DESCRIPTION
Oral Presenation - Paulo Cesar - Oklahoma and Boston in March 2015TRANSCRIPT
-
UNIVERSITY OF SO PAULOSCHOOL OF DENTISTRYDEPT. OF BIOMATERIALS AND ORAL BIOLOGY
Reinforcement of Y-TZP with carbon nanotubes using different coprecipitation techniques
L. Silva, D. Lazar, V. Ussui, W. Yoshito, R. Tango, U. Lohbauer, P. Cesar*
-
QR Code Reader
App Store
Google Play Store
-
INTRODUCTION
Reinforcement of ceramics with second-phase particles/fibers
Sgura et al., 2012
-
Reinforcement of dental ceramics:
Mechanical behavior Optical properties
Cesar et al., 2012 Kaizer et al., 2015
-
Medeiros et al., 2009J Mech Behav Biomed Mater
Al2O3/GdAlO3 particles
dental porcelain
Reinforcement of dental ceramics with Al2O3/GdAlO3 particles
-
Kaizer et al., 2015
Addition of saphire to dental porcelain
-
Addition of saphire to dental porcelain
saphire dental porcelain ControlPorcelain
+saphire
-
Addition of potassium titanate whiskers to dental porcelain
-
ControlPorcelain
+Whiskers
51.3 4.9b 76.5 11.0a
Flexural strength (MPa)
0
5
10
15
20
25
30
Tran
slu
cen
cy P
aram
ete
r
Addition of potassium titanate whiskers to dental porcelain
Translucency
controlPorcelain
+ whiskers
-
Sintered: 4.0 1.1a Hot-Pressed : 0.3 0.2b
Effect of processing method on porosity (%) of dental porcelains
-
Yu et al. (2000) Borba et al. 2010
+
Multi-Wall Carbon NanoTube(MWCNT)
Y-TZP
Addition of Nanotubes to Y-TZP
-
Ando (2010)Yu et al. (2000);
Hardness: ~500 GPa
Strength: ~30 GPa
Elastic Modulus: 950 GPa
MWCNT (Multi-Wall Carbon NanoTube)
MWCNT
-
Garmendia et al. (2010)
Addition of Nanotubes to Y-TZP
Crack bridging
Hinders Low-Temperature Degradation
-
Jagadeesan et al. (2010)
Functionalized nanotubes (white shade)
MWCNT-COOH
-
Technological challenge re: adding nanotubes to Y-TZP
Avoiding CNT degradation during processing;
Achieving good dispersion of CNT on the Y-TZP matrix.
-
Achieving good dispersion of CNT on the Y-TZP matrix
Zr(OH)4 + Y(OH)3
Synthesis of Y-TZP powders
Nanotube+
Nanotube+
150C
150 RPM 6.8 atm pH 10 16 h
WATER OR ALCOHOL ???
Y-TZP
-
OBJECTIVES
To compare two synthesis techniques:
Water-based (hidrothermal)
Alcohol-based (solvothermal)
used to facilitate the dispersion of multi-walled carbon nanotubes
(CNT) into an yttria-stabilized tetragonal zirconia pollycristal (Y-TZP).
Hypothesis: both techniques will be sucessful in producing the new
composite.
-
Zr(OH)4 + Y(OH)34g
Coating of Nanotubes with zirconia/yttria (synthesis)
Nanotube75 mg (~5 vol%)
+
METHODS
-
Functionalized nanotubes (Nanoshell)
-
150 C
150 RPM
6.8 atm
pH 10
16 h
WATER OR ALCOHOL
Coating of Nanotubes with zirconia/yttria (synthesis)
-
Coating of Nanotubes with zirconia/yttria
Y-TZP powder coating nanotubes (CNT/ZYO)
-
Coating of Nanotubes with zirconia and yttria
After filtering, washing and drying Breaking clusters
Y-TZP powder coating nanotubes (CNT/ZYO)
-
Y-TZP powder coating nanotubes (CNT/ZYO)
Transmission electron microscopy
-
Experimental groups (starting powders):
1. Control: Y-TZP commercial powder from Tosoh (TZ3YE)
2. Composite A: 1 vol% of CNT/ZYO (processed in water) + TZ3YE
3. Composite B: 1 vol% of CNT/ZYO (processed in alcohol) + TZ3YE
-
Green discs (15 x 2 mm)
Uniaxial pressing (67 MPa)
n = 3
Specimen production
-
Inert atmosphere (argon)
1,400 C /4 h
Heating rate: 5 C/min
Sintering in argon atmosphere
-
Mirror polishing
-
Characterization of experimental groups
Density (Archimedes principle)
Relative Density (based on Helium picnometry)
Indentation fracture toughness and Vickers hardness
Optical properties (Contrast Ratio, L*a*b*, and color difference)
Data analyzed by t-Student test (alpha = 0.05)
-
RESULTS
Control (Y-TZP) Y-TZP + Nanotubes(processed in water)
Y-TZP + Nanotubes(processed in alcohol)
Macroscopic aspect after sintering
-
(RD:95.3%) (RD:94.9%)
(p=0.14)
Density
-
(p=0.25)
Hardness
-
(p=0.39)
Fracture toughness
-
Optical properties (contrast ratio)
(p=0.12)
-
Control (Y-TZP) Y-TZP + Nanotubes(processed in water)
D E = 6.0 3.1
Optical properties (color difference)
-
Optical properties (CIE L*a*b* coordinates)
(less yellow)
(more red)
(more white)
-
Solvothermal technique (i.e., using alcohol) causedsevere discoloration of the Y-TZP/nanotube composite;
Hydrothermal technique (i.e., using water) resulted inY-TZP/nanotube composite with small color differencein comparison to the control;
However, mechanical properties of the produced Y-TZP/nanotube composite were not significantlyimproved by the addition of CNT.
Supported by FAPESP
2012/16027-2
CONCLUSION
-
Thank you!