Tribological and Catalytic Coatings Objectives: Study of mechanical properties of nanocomposite and nanolaminate thin films deposited by pulsed laser deposition (PLD): Nitride-based coatings (AlN, TiN, CrN) Oxide-based coatings (Al 2 O 3, ZrO 2 ) Development hard coatings with catalytic properties: Catalytic surfaces for carbon nanotube growth Transition of current materials research to industrially friendly magnetron sputtering deposition technique
Development of Tribological Coatings Using PLD (Metal-Ceramic Composites) Objectives To design and fabricate metal-ceramic thin film composites with improved mechanical properties (hardness and fracture toughness. Fe and Ni nanoparticles significantly increase hardness of films deposited at 39 lower temperatures Hardness, GPa 36 33 30 27 24 21 18 15 Al 2 O 3 Al 2 O 3 /Ni Al 2 O 3 /Fe 12 200 300 400 500 600 700 800 Substrate Temperature, C Hardness of multilayered metal/ceramic nanocomposites deposited at different substrate temperatures TEM image of multilayered structure developed by PLD method demonstrating catalytic effect of metal particles on crystallization of amorpous alumina.
Tribological Properties of Multilatered Systems (AlN-TiN nanocomposites deposited by PLD) AlN-TiN nanolaminates: Effect of layer thickness and number of layers on Critical load in scratch tests Coefficient of friction and roughness Fracture toughness Effect of substrate temperature on hardness Nanoscratch behavior of TiN thin films Effect of deposition temperature on critical load 0.4 AlN-TiN 100 layer film Coefficient of Friction 0.3 0.2 500 C Deposit 0.1 700 C Deposit Critical Load TEM image of AlN-TiN Multilayered system 0.0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 Load Applied on the Sample (mn)
Fracture Toughness of AlN-TiN Nanolaminates Fracture behavior of AlN/TiN thin films deposited at different temperatures Hardness of 6.4 nm/layer AlN/TiN thin films deposited at different temperatures 200 ºC 500 ºC 800 ºC 20 800 o C Nanohardness (GPa) 15 10 5 500 o C 200 o C xp/c 3/2 1.50 1.45 1.40 1.35 Effect of layer thickness and deposition temperature on fracture toughness of TiN-AlN thin film system Alternate 5 AlN and 5 TiN layers Layer thickness ~35 nm Total thickness ~350 nm 1.30 1.25 1.20 1.15 1.10 1.05 1.00 0.95 0.003 0.004 0.005 0.006 0.007 Zc 1/2 T K 1C σ(mpa) 500 o C 1.80-101 700 o C 1.74-115 800 o C 0.40-96 X r P/c 1.5 3.5 3.0 2.5 2.0 1.5 1.0 Alternate 50 AlN and 50 TiN layers Layer thickness ~2.3 nm Total thickness ~230 nm 0.5 0.002 0.003 0.004 0.005 0.006 0.007 Z c 0.5 T K 1c σ(mpa) 200 o C 5.1-615 500 o C 3.7-392 700 o C 1.2-75 800 o C 2.4-214 0 200 400 600 800 1000 1200 Depth of Indent (nm) Increase of deposition temperature leads to hardness increase Decrease of layer thickness with subsequent increase of number of alternate layers leads to significant improvement in fracture toughness
Cross-sectional indentation study: New method development for thin film fracture toughness and adhesion properties study Cross-sectional indentation allows to determine adhesion energy of multilayered systems. Currently we study repetability of results and discovered high importance of indentation position which require piezo- nanopositioning stage in Nanoindentor XP 40 δ 30 Load, mn 20 10 0 0 500 1000 1500 Indentation Depth, nm u 0 = δ tan 35.3º
Tribological and Catalytic Coatings (Current Activities and Future Plan) Set-up Magnetron Sputtering System (July-August) Magnetron Sputtering process optimization for: TiN (DC reactive sputtering) CoN (DC reactive sputtering) γ-alumina (DC and RF sputtering) Catalytic surface for carbon nanotube growth Fe nanoparticles embedded into alumina matrix New catalyst development by pulsed laser deposition method Optimization of the SiO 2 /Al 2 O 3 /Fe catalytic system Comparative analysis of catalytic activity of Ni, Mo, Ag, Ru and other metal nanoparticles for CVD carbon nanotube growth
Task: Optimization of TiN coating by Magnetron Sputtering (September-December 2006) Magnetron Sputtering Processing Parameters: Effect of substrate temperature Effect of RF bias Effect of DC power Partial pressures of N 2 and Ar Total gas pressure Characterization Methods (implemented for each sample): XRD SEM AFM Profilometry Nanoindentation (up to date 2 samples are studied) Up to date deposited 23 TiN samples at different substrate temperatures, gas pressure with and without RF substrate bias Example of AFM nanoroughness study: TiN (DC 150W, RF bias 5W, 300ºC, P tot. 2 mtorr) Average nanoroughness (Sa): 1.82 nm
Center for Nanoscience and Nanomaterials Optimization of TiN coating by Magnetron Sputtering Substrate Bias: 10 W Substrate Temp: 200 C Substrate Bias: 10 W Substrate Temp: 400 C Substrate Bias: None Substrate Temp: 400 C
Optimization of TiN coating by Magnetron Sputtering 111 200 220 311 222 #30 #29 #29 DC 150W Bias 5W t 300ºC P tot. 2mtorr #23 DC 150W Bias 5W t 300ºC P tot. 4mtorr #22 DC 250W Bias 0W t 300ºC P tot. 4mtorr #21 #20 DC 250W Bias 5W t 300ºC P tot. 4mtorr DC 250W Bias 0W t 400ºC P tot. 4mtorr Property Nanoroughness (nm) Sample 30 29 12.75 1.82 #19 DC 250W Bias 10W t 400ºC P tot. 4mtorr Total gas pressure (mtorr) Deposition rate (nm/s) 4 0.054 2 0.032 #17 DC 250W Bias 10W t 200ºC P tot. 4mtorr Thickness (nm) after 2 hours Hardness (GPa) 385 10 230 26 40 50 60 70 80 2-Theta Young s Modulus (GPa) Orientation on Si(100) 210 111 320 111,200
Nanoindentation results Hardness (GPa) 30 25 20 15 10 5 0 0 200 400 600 800 1000 Indentation Depth (nm) Sample #29 Sample #30 Modulus (GPa) 320 300 280 260 240 220 200 180 160 140 120 100 0 200 400 600 800 1000 Indentation Depth (nm) Sample #29 Sample #30 Importance of process optimization: Samples were deposited at identical processing parameters (DC 150W, RF Bias 5W, T=300ºC, deposition time=2 hours, P(N 2 )=0.34 mtorr) except P total (2 mtorr for sample #29 and 4 mtorr for sample #30). However, samples have totally different mechanical and microstructural properties.