H. W. Choi 1, 2 , K. -R. Lee, R. Wang 3 , K. H. Oh 2 - PowerPoint PPT Presentation

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H. W. Choi 1, 2 , K. -R. Lee, R. Wang 3 , K. H. Oh 2 PowerPoint Presentation
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H. W. Choi 1, 2 , K. -R. Lee, R. Wang 3 , K. H. Oh 2
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H. W. Choi 1, 2 , K. -R. Lee, R. Wang 3 , K. H. Oh 2

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  1. DLC 20μm Si buffer layer ( 2m30s – 15min) Ar pre-cleaning (15-60min) SUS 304 SUS 304 0.09-0.12mm (a) 100μm 20μm (b) (d) (c) (b) (c) (a) 20μm 20μm 20μm 20μm 20μm 20μm (d) Heart Valve Stability of DLC film on stainless steel investigated by tensile-test H. W. Choi1,2, K. -R. Lee, R. Wang3, K. H. Oh2 • Future Technology Research Division, Korea Institute of Science and Technology • Materials Science and Engineering, Seoul National University • Department of Metals and Materials Engineering, University of British Columbia, Vancouver, Canada Introduction • Biological application of DLC as a stent • General Bio application of DLC DLC for Wear Resistance Courtesy of A-san hospital (’04.7.) ● 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 Experimental condition Purpose • 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 • Ar pre-cleaning Time & adhesion Experimental Results 20μm Ar -600Vb, 15min Ar -600Vb, 30min 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 Strain- Force curve of tensile test Ar -600Vb, 60min • Bias voltage & adhesion • Annealing & adhesion • Si buffer thickness & adhesion Summary • 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 Ar -200Vb Ar -900Vb, No annealing Si -200Vb, 19nm • Evolution of spallation • ◦ Crack occurrence : Vertical of tensile direction • ◦ Spallation evolution direction : shear stress direction • Possibility of adhesion evaluation by tensile test. Ar -900Vb Ar -900Vb, 400°C annealing Si -200Vb, 84nm