Tribological Property andBiocompatibility of Titanium Plate
Coated with Carbon Nanotubes

1Background

Titanium

Carbon nanotube

Stent

d= ~20nmφ
L= 1~5μm

Implant
10μm

Boeing 787 Dreamliner••••

Superior self-lubrication
High yield stressHigh Young’s modulus
High electrical & thermal
conductivity
Naturally uniform
as bundles due to van der
Waals forces• High strength• Good corrosion resistance• Good biocompatibility• Low density
Poor Tribology property
contacted with othermaterials and Ti2

Objectives

1. Investigate tribological property and wear
behavior of pure Ti plate coated with CNTs
under dry sliding condition.
① Network-structured MWCNTs coating on Ti plate.
② Analysis on interface between CNTs and Ti substrate.
③ Effect of annealing temperature on tribologicalbehavior of CNTs coating films.

2. Investigate the biocompatibility of pure Ti
plate coated with CNTs.
3

CNT dispersions

CNTs bundle disassemble in zwitterionic surfactant solution“Heads”; hydrophilic

Self-assembly

Bundled
CNTs

ZwitterionicSurfactant“Tails”; hydrophobic
Headgroup
TailCNT

Un-bundled
CNTs inZwitterionicsurfactant

4Electrostaticforce

CNT dispersions

Segregation ofbundled CNTs

CNTs distributed in water
after ultrasonic vibration

CNTs distributed in waterwith surfactants

5Preparation of specimen

Pure Ti plate
Coated withun-bundled CNTs

Dipped• Ball-on-disk
wear test• XRD & SEMEDS analysis

Annealed

Surfactant solution
with un-bundled
CNTs
10μm
66

SEM and AFM observation

1μm

Observed by SEM & AFM on CNTs coated onpure Ti plate annealed at 1123 K
7

XRD result― with CNTs annealed at 1123 K (a)― with CNTs annealed at 973 K (b)― as-received pure Ti Plate (c)□●TiC□α-Ti(hcp)□Intensity / a.u.

●□●□● □●(a)
(b)

□□

(c)
30

3540

45

5055

6065

Diffraction
Angle, 2θ / °
870

75

80

8

XRD result

Intensity(a.u.)
Intensity (a.u.)― with CNTs annealed at 1123 K (a)― with CNTs annealed at 973 K (b)― as-received pure Ti Plate (c)
□

●35

36

●TiC
□α-Ti(hcp)
□□

●(a)
(b)
(c)

33

34

37

38

39

40

Diffraction
Angle 2θ
2Θ/ /°degree
Diffraction
DiffractionAngle,°9Angle, 2θ

4142439XRD result― with CNTs annealed at 1123 K (a)― with CNTs annealed at 973 K (b)― as-received pure Ti Plate (c)Ti peak (1, 1, 2)dIntensity (a.u.)

(a)
(b)

7676.276.4



4 h 2  k 2  hkl2
 22
3ac
h, k, l: Miller indicesa, c: Lattice constant

(c)

75.8



176.6

Diffraction Angle, 2θ / degree
10

XRD result(a) with CNTs annealed at 1123 K(b) with CNTs annealed at 973 K(c) as-received pure Ti Plateca
4.73

Experimental
Theoretical

2.99

Lattice constant, c / ÅLattice constant, a / Å

3.00

2.98
2.97
2.96
2.95

4.72

Experimental
Theoretical

4.71
4.70
4.69
4.68
4.67
4.66

2.94

(a)

(b)

(c)

(a)

Relationship between lattice constant
11(b)

(c)

SEM-EDS analysis result

CNTs Film
TiC Layer
TiC Layer
Carbon

Ti

1μm
1μm

Cross-section of pure Ti plate coated withCNTs annealed at 1123 K
1212

Hardness result(a) with CNTs annealed at 1123 K(b) with CNTs annealed at 973 K(c) as-received pure Ti Plate

Vickers micro hardness (Hv)

600500

Testing area

400
300

1μm

200
1000(a)

(b)

(c)
1313

Ball-on-disk wear test equipment

Ball-on-disk wear test
SUS304ball

Load
F=100gf
Ti Plate

Rotating

SUS304 ball(φ; 4.7mm)

Attachment

Total sliding distance, L =113m ( ←31.4 mm/s×3600s)
Test condition: Room Temperature,
No lubricant (Dry condition)1414

Ball-on-disk wear test results(a) CNTs annealed at 1123K(b) CNTs annealed at 973K

μ0 = 0.34

μ0 = 0.19(c) as-received Ti Plate
Conditions• Counterpart Material ；SUS304 Ball
• Load ；100gf•Rotating Speed；31.4mm/s

μ0 = 0.951515

Ball-on-disk wear test results
Wear track of Ti plate as received (with NO film) and SUS 304 ball

Sliding direction

Pure Ti Plate
Counterparts material (SUS 304 ball)

Ti
100μm
500μm

500μm

Wear debris

CrFe

500μm

Abrasive wear
1μm
area
16500μm

Ball-on-disk wear test results
Wear track of Ti plate coated with CNTs annealed at 1123K and SUS 304 ballCounterparts material (SUS 304 ball)

Sliding direction

Ti Plate coated with CNTs

10μm

100μm

TiC

10μm

10μm

CrFe
1μm
10μm
1710μmBiomedical application of Titanium

Object #2
Investigate the biocompatibility of pure Ti plate coated with CNTs

Surface modification of Titanium surface by CNTs
Facilitating tissue engineering
CNTs hold as a tissue engineering substrate ?
Examined① Cell adhesion after 72 h
② Biocompatibility of rat

5 weeks

18

Tissue engineering - Cell adhesion test result
Ti plate

Cell attachment and spreading out
Ti plate coated with CNTs > Ti plate

Cell growing on CNT-net
100μm
Ti Plate coated with CNTs

3 μm

Well-demonstrated CNTs
in the tissue engineering

100μm
19

Tissue engineering - Study of bioactivity
Evaluate the biocompatibility of CNT-net nano morphologies
 Observations at 5 weeks after implantation into rat
 Inflammatory cell infiltration was rarely observed

good biocompatibility
 Promoting new bone formation by CNT-netPlatetissue
headtissue
Newbonehead20Conclusions

1. CNTs were successfully coated on Ti plate annealed at 973 Kand 1123 K.
2. Formation of network-structured CNT films was effective toreduce the friction coefficient of Ti plate due to their excellent
self-lubricant effect.
3. Annealing at 1123 K caused TiC formation at interface between
CNTs and Ti substrate, and then excellent metallurgical bonding
was obtained. As a result, CNT films were obviously remained
at wear track even after dry sliding when SUS304 stainless ball
was used as a counterpart material.
4. CNT-net nano modification provided the acceleration of newbone formation to the Ti plate surface.

2121