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Tribological Property and Biocompatibility of Titanium Plate

Coated with Carbon Nanotubes

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Boeing 787 Dreamliner

Background

• High strength• Good corrosion resistance• Good biocompatibility • Low density

Carbon nanotubeCarbon nanotube

• Superior self-lubrication• High yield stress• High Young’s modulus• High electrical & thermal

conductivity

Stent

Implant

d= ~20nmφL= 1~5μm

10μm

Naturally uniform as bundles due to van der

Waals forces

Poor Tribology property contacted with other

materials and Ti

TitaniumTitanium

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2. Investigate the biocompatibility of pure Tiplate coated with CNTs.

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.

Objectives

1. Investigate tribological property and wearbehavior of pure Ti plate coated with CNTsunder dry sliding condition.

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CNT dispersions

CNTs bundle disassemble in zwitterionic surfactant solution

“Heads”; hydrophilic

“Tails”; hydrophobic

CNT

Headgroup

Tail

Bundled CNTs

Zwitterionic Surfactant

Un-bundled CNTs in

Zwitterionic surfactant

Self-assembly

Electrostatic force

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CNTs distributed in water with surfactants

CNTs distributed in water after ultrasonic vibration

Segregation of bundled CNTsSegregation of bundled CNTs

CNT dispersions

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Preparation of specimen

Dipped

Surfactant solution with un-bundled

CNTs

10μm

Coated with un-bundled CNTs

Annealed• Ball-on-disk

wear test• XRD & SEM-

EDS analysis

Pure Ti plate

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

SEM and AFM observation

1μm

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30 35 40 45 50 55 60 65 70 75 80

Inte

nsity

/ a.

u.

Diffraction Angle, 2θ / °

XRD result

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●TiC□α-Ti(hcp)

●

● ●□

□

□

□

□□

□

●

(a)

(b)

(c)

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

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33 34 35 36 37 38 39 40 41 42 43Diffraction Angle 2Θ / degreeDiffraction Angle, 2θ / °

Inte

nsity

(a.u

.)

●□ □ ●□

(a)

(b)

(c)

Inte

nsity

(a.u

.)

Diffraction Angle, 2θ / ° 9

XRD result

●TiC□α-Ti(hcp)

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

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XRD result

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

75.8 76 76.2 76.4 76.6

Inte

nsity

(a.u

.)

Diffraction Angle, 2θ / degree

Ti peak (1, 1, 2)

(a)

(b)

(c)

2

2

2

22

34

1

cl

ahkkh

d

h, k, l: Miller indicesa, c: Lattice constant

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

Latti

ce c

onst

ant,

a / Å

ExperimentalTheoretical

(a) (b) (c)2.94

2.95

2.96

2.97

2.98

2.99

3.00

a

c

Relationship between lattice constant

XRD result

Latti

ce c

onst

ant,

c / Å

4.66

4.67

4.68

4.69

4.70

4.71

4.72

4.73ExperimentalTheoretical

(a) (b) (c)

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Cross-section of pure Ti plate coated with CNTs annealed at 1123 K

TiCarbon

1μm

SEM-EDS analysis result

TiC Layer

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1μm

TiC Layer

CNTs Film

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

Vick

ers

mic

ro h

ardn

ess

(Hv)

0

100

200

300

400

500

600

(a) (b) (c)

1μm

Testing area

Hardness result

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Total sliding distance, L =113m ( ←31.4 mm/s×3600s)

Load F=100gf

Ti Plate

SUS304 ball(φ; 4.7mm)

Test condition: Room Temperature, No lubricant (Dry condition)

SUS304ball

Attachment

RotatingRotating

Ball-on-disk wear test equipment

Ball-on-disk wear test

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μ0 = 0.19(a) CNTs annealed at 1123K

Conditions • Counterpart Material ；SUS304 Ball• Load ；100gf•Rotating Speed；31.4mm/s

μ0 = 0.34(b) CNTs annealed at 973K

μ0 = 0.95

(c) as-received Ti Plate

Ball-on-disk wear test results

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16

100μm

1μm

Slid

ing

dire

ctio

n

Wear track of Ti plate as received (with NO film) and SUS 304 ball

Wear debris

Abrasive wear area

Pure Ti Plate

500μm

500μm500μm

500μm

Ti

Fe Cr

Counterparts material (SUS 304 ball)

Ball-on-disk wear test results

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1μm

100μmSlid

ing

dire

ctio

n

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

Ti Plate coated with CNTs

10μm 10μm

10μm 10μm

10μm

C Ti

Fe Cr

Counterparts material (SUS 304 ball)

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CNTs hold as a tissue engineering substrate ?

Biomedical application of Titanium

Surface modification of Titanium surface by CNTs

Facilitating tissue engineering

Examined

① Cell adhesion after 72 h

② Biocompatibility of rat

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

5 weeks

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Tissue engineering - Cell adhesion test result

100μm

100μm

Ti plate

Ti Plate coated with CNTs

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

Cell growing on CNT-net

3 μm

Well-demonstrated CNTsin the tissue engineering

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Observations at 5 weeks after implantation into rat Inflammatory cell infiltration was rarely observed

good biocompatibility Promoting new bone formation by CNT-net

Tissue engineering - Study of bioactivity

Evaluate the biocompatibility of CNT-net nano morphologies

Plate

head

head

tissue

tissueNew bone

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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 excellentself-lubricant effect.

3. Annealing at 1123 K caused TiC formation at interface betweenCNTs and Ti substrate, and then excellent metallurgical bondingwas obtained. As a result, CNT films were obviously remainedat wear track even after dry sliding when SUS304 stainless ballwas used as a counterpart material.

4. CNT-net nano modification provided the acceleration of newbone formation to the Ti plate surface.

Conclusions

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