H. W. Choi1,2, K. -R. Lee, R. Wang3, K. H. Oh2

Introduction

General Bio application of DLC

Heart Valve

DLC for Wear Resistance

Purpose

Experimental Results

Biological application of DLC as a stent

Courtesy of A-san hospital (’04.7.)

Estimated problem of DLC for bio application as a stent

○ Biomaterial : Stainless steel

○ Disadvantage of metal substrate as a biomaterial - wear debris : cause foreign body reaction, tissue reaction - harmful ion ( Cr+, Ni+) can occurrence - metal corrosion can induce bone resorption

Experimental condition

SUS 304 0.09-0.12mm

Ar pre-cleaning (15-60min) Si buffer layer ( 2m30s – 15min)

DLC

SUS 304

● Electrolytic-polishing ○ liquid : A2

○ 15V, 19flow, 30Sec ● Processing parameters

○ Ar cleaning : 3mTorr, -600Vb, 15min-60min

○ Si buffer layer - 20m Torr, 60% MFC - -200Vb, 2min 30sec-15min

○ Annealing : at room-400°C ● DLC deposition

○ R.F-PACVD

○ C6H6, -400Vb, 10mTorr, 11min

Strain- Force curve of tensile test

(a)

(b)

(c)

(d)

0.00 0.02 0.04 0.06 0.08 0.10 0.120

100

200

300

400

500

Forc

e (N

)

L/L

(a)

(b)(c)

(d)

Summary

A direction of cracks followed the perpendicular against strain direction and spallation which seem to related to its slip band propagated with its shear stress

100μm

Stability of DLC films within 2% strain. However, Observed crack occurrence from 3.8% strain.

A Relationship of adhesion depends on processing parameters. ◦ Improvement of adhesion with increasing Ar pre-cleaning time ◦ Enhancement of adhesion with increasing Bias voltage during

Ar pre-cleaning. ◦ Increasing of adhesion with increasing Si buffer layer thickness ◦ Degradation of adhesion with increasing Bias voltage during

Si buffer layer deposition ◦ Deterioration of adhesion with increasing Annealing temperature

Possibility of adhesion evaluation by tensile test.

Evolution of spallation ◦ Crack occurrence : Vertical of tensile direction ◦ Spallation evolution direction : shear stress direction

Ar pre-cleaning Time & adhesion

20μm

20μm20μm

Bias voltage & adhesion

Ar -600Vb, 30minAr -600Vb, 15min

Ar -600Vb, 60min

20μm

20μm

Ar -200Vb

Ar -900Vb

Annealing & adhesion

20μm

20μm

Ar -900Vb, No annealing

Ar -900Vb, 400°C annealing

Si buffer thickness & adhesion

20μm

20μm

Si -200Vb, 19nm

Si -200Vb, 84nm

Stability of DLC film on stainless steel investigated by tensile-test

1.Future Technology Research Division, Korea Institute of Science and Technology

2. Materials Science and Engineering, Seoul National University

3. Department of Metals and Materials Engineering, University of British Columbia, Vancouver, Canada