Dynamic Nanoindentation Characterization: nanodma III. Ude Hangen, Ph.D

Transcription

1 Dynamic Nanoindentation Characterization: nanodma III Ude Hangen, Ph.D

2 Displacement 11/02/2017 Bruker Confidential 2 nm mm mm Outline Elastic-Plastic vs. Viscoelastic Materials Response nanodma Technology Minimum load pre-load DMA Application Examples Elastic-Plastic Thin-Hard-Coating PM 2000 alloy Viscoelastic 3D-Printed Polylactide Silicone with crosslinking agent Polycarbonate pn microindenter nanoindenter AFM nn mn mn N Load

3 Load (µn) Indentation Load (un) Materials Covered in this Presentation Materials Properties Elastic-Plastic Response Viscoelastic Response 1000 Load-Displacement Curve Easy to identify by quasi-static indentation Load Function Al<100> PC Time (s) Indentation Displacement (nm) 11/02/2017 Bruker Confidential 3

4 Load (µn) Indentation Load (un) Materials Covered in this Presentation Materials Properties Elastic-Plastic Response (Oliver&Pharr) Viscoelastic Response 1000 Unloading and Re-Loading Elastic Easy to identify by quasi-static indentation Load Function 600 Elastic and Plastic Deformation Al<100> PC Hysteresis Time (s) Indentation Displacement (nm) 11/02/2017 Bruker Confidential 4

5 11/02/2017 Bruker Confidential 5 Materials Covered in this Presentation Elastic-Plastic Response Thin Film Depth Profiling Viscoelastic Response Investigation of Polylactide Filaments for 3D-printing. High-Temperature Creep testing of a PM2000 alloy. Comparision of nanodma III and Macro DMA tests on silicone with cross linking agent. Polycarbonate Mastercurve.

6 Transducer & Controller Core Technology Springs Center Electrode Outer Electrode Outer Electrode Capacitive displacement sensing Small inertia of moved parts <1 g Low intrinsic dampening Indenter Load or Displacement Control 78 khz Feedback Loop Rate 38 khz Data Acquisition Rate Experimental Noise Floor <100 nn (Digital Controller) Enhanced Testing Routines Digital Signal Processor (DSP) + Field Programmable Gate Array (FPGA) + USB Architecture Modular Design Transducer Stability Specs <0.2 nm displacement noise floor <100 nn force noise floor <0.05 nm/sec thermal drift *Specs Guaranteed On-Site* Enabling Technology for Ultra-Small Materials Research 11/02/2017 Bruker Confidential 6

7 Load, P 11/02/2017 Bruker Confidential 7 Quasi-Static Nanoindentation Contact Depth (h c ) h c h max Contact Area (A c ) A P S f c h c max Elastic Modulus (E) E r reduced elastic modulus S 2 A c projected contact area (evaluated at maximum load) P max Hardness (H) H P max A c 0 0 Initial Unloading Stiffness dp S dh h max ma( h m 1 max hf ) h c A c h max h f Depth, h W.C. Oliver, G.M. Pharr, J. Mater. Res. 7 (1992) Power-law Fit to Unloading P A( h ) h f m E vi 1 vs r Ei Es Indenter Sample Poisson s Ratio Sample s Elastic Modulus

8 11/02/2017 Bruker Confidential 8 nanodma III Overview Continuously measure properties as a function of contact depth, frequency, and time. Dynamic force superimposed on quasi-static force

9 11/02/2017 Bruker Confidential 9 nanodma III Technology Oscillating Force (µn, Hz) Springs Center Electrode Outer Electrode Lock-In Amplifier Static Force Signal Outer Electrode Amplitude (nm), Phase (deg) Indenter Lock-In Amplifier Frequency Range Frequency Range for Testing: 0.1 Hz 300 Hz Typical Force Amplitude: 0.01 µn to 200 µn Typical Displacement Amplitude: 0.1 nm to 5 nm Static Displacement Signal

10 11/02/2017 Bruker Confidential 10 CMX Force & Displacement & Stiffness Dynamic Testing Force & Displacement vs. Time CMX Profile: Hardness & Modulus Lock-In Amplifier Stiffness vs. Time Amplitude & Phase vs. Time

11 Height (nm) Thin Film Nanoindentation DLC coating on high-strength steel Image of film edge on substrate In-situ SPM Metrology on coating: Cross-Section Profile Position (µm) Surface Roughness Film Thickness: 135 nm Steel Substrate: Peak To Valley = 14.8 nm Average Roughness (Ra) = nm RMS Roughness (Rq) = nm DLC-Coating: Peak To Valley = nm Average Roughness (Ra) = nm RMS Roughness (Rq) = nm 11/02/2017 Bruker Confidential 11

12 Reduced Modulus (GPa) Hardness (GPa) Thin Film Nanoindentation 3 coatings on steel Berkovich Indenter CMX-depth profile Steel Substrate 135 nm DLC 75 nm DLC 25 nm DLC Contact Depth (nm) Contact Depth (nm) 11/02/2017 Bruker Confidential 12

13 xsol High Temperature Stage Nanomechanical Characterization at Temperatures up to 800 C Low Thermal Expansion Design Tight Temperature Control Uniform Sample Temperature Probe Tip Heating in Uniform Environment Easy Sample Mounting Atmosphere Control Fast Warm-up and Stabilization Constructed to Handle Temperatures up to ~1000 C; Limitation by Tip Material 11/02/2017 Bruker Confidential 13

14 Reference Creep Testing Quasi-static load is held constant (in this case 5 mn). A relatively small (~1 nm) amplitude sinusoidal force is superimposed at user-specified frequency (in this case 220 Hz). Force amplitude, displacement amplitude, and phase shift are measured, allowing contact stiffness to be measured continuously. 11/02/2017 Bruker Confidential 14

15 Reference Frequency Technique nanodma III incorporates a reference frequency technique for thermal drift correction during the course of an experiment. S(Ef*, A(hc)) Enables the measurement of contact area without relying on the raw displacement data. The continuously measured stiffness is used to accurately determine contact area and contact depth in-situ. In-situ drift compensation during long duration frequency sweeps and creep tests. Stiffness vs. Depth on FQ Calibrated tip area function relates contact depth to contact area: A(h c ) = C 1 h c 2 + C 2 h c + C 3 h c 1/2 + C 4 h c 1/4 + C 5 h c 1/8 + C 6 h c 1/16 11/02/2017 Bruker Confidential 15

16 Converting Depth to Strain Rate Tensile Testing Indentation Testing The strain rate is the indenter velocity divided by the indentation depth. (Pyramidal Indenter) h ε = h / h h Uniform Stress Uniform Strain h h Stress Field Strain Field ε = h / h The mean contact pressure, is the applied force divided by the projected contact area. This is also the definition of hardness. σ = P/A = H 11/02/2017 Bruker Confidential 16

17 Steady State Creep Strain rate varies with stress and temperature: ε = Aσ m Q RT e m: Stress Exponent Q: Activation Energy T: Temperature : Stress : Strain R: Gas Constant A: Proportionality Constant h Depth h and velocity are determined from a fit to the creep curve. Pressure equals the hardness value. 11/02/2017 Bruker Confidential 17

18 Reference Creep Test on PM 2000 PM 2000 ODS Alloy: FeCrAl alloy with dispersed oxide nano-particles High creep resistance of dispersion hardened materials Typical stress exponent m = (creep rate drops fast with stress) Interaction of dislocation with dispersed oxides: Small particles can be passed by climbing Line energy between particle and dislocation is reduce Thermal activation and external stress needed Mechanism is highly dependent on external stress Indenter Used: Berkovich Sapphire Shield Gas: 95%N5%H 11/02/2017 U.Hangen et al. AEM (2015). Bruker Confidential 18

19 Finding Stress Exponent Plot ln(ε ) versus ln H and slope is stress exponent m. Temp. (C) m m 80: typical for ODS alloys m 8: thermal activated dislocation motion 11/02/2017 U.Hangen et al. AEM (2015). Bruker Confidential 19

20 11/02/2017 Bruker Confidential 20 Viscoelastic Matter Domain of Testing Strain Rate Frequency Temperature Constant Strain Rate Testing x Indentation Creep Testing x Creep and Recovery Testing x x nanodma III Testing x x nanodma III Testing + xsol x x x

21 Load (µn) 11/02/2017 Bruker Confidential 21 Polylactide Characterization Viscoelastic Response Time Dependent Deformation Hardness depends on strain rate Experimental: A constant strain rate is achieved by exponential loading. T = 23 C Force Amplitude/Quasi-static Force <<1 Dynamic Frequency 110 Hz Small displacement amplitude of 1-2 nm /s 0.1 1/s /s /s Time(s)

22 Hardness (GPa) Reduced Modulus (GPa) 11/02/2017 Bruker Confidential 22 Depth Profile Viscoelastic Response Time Dependent Deformation Reduced modulus is strain rate independent Strain rate 0.01 Strain rate 0.1 Hardness (stress under indenter) relates to a strain rate Contact Depth (nm) 8 Strain rate 0.01 Strain rate Contact Depth (nm)

23 Reduced Modulus (GPa) Force (µn) Hardness (GPa) Depth Profile with Changing Rate A load function with combined strain rate segments results in the respective hardness readings /s /s Strain rate 0.01 Strain rate 0.1 Strain rate jump Strain Rate Jumping Contact Depth (nm) Strain rate 0.01 Strain rate 0.1 Strain rate jump Time (s) Technique proposed by: V. Maier et al., J. Mater. Res., (2011) Contact Depth (nm) 11/02/2017 Bruker Confidential 23

24 Strain Rate Spectrum High Strain Rates: Constant strain rate testing; 0.01 / 0.05 / 0.1 / 0.5 1/s (left) Low Strain Rates: 1 hour reference creep experiment 0 ln (strain rate) -2-4 Creep Test 1h Creep Test 1h Creep Test 1h Strain rate 0.01 Strain rate 0.05 Strain rate 0.1 strain rate ln (H) 11/02/2017 Bruker Confidential 24

25 11/02/2017 Bruker Confidential 25 Temperature Dependent Testing Temperature range for 3D printed parts Polylactide is thermoplastic What is the glass transition temperature Tg about? Structural changes Mechanical changes As 3D-printed Deformed at T>Tg

26 xsol Sample Heating Solution Low Thermal Expansion Design Tight Temperature Control Uniform Sample Temperature Probe Tip Heating in Uniform Environment Interfaces with all testing modes: Quasi-static Testing nanodma III Testing Scratch Testing In-situ SPM imaging 11/02/2017 Bruker Confidential 26

27 Indentation Load (un) Indentation Displacement (nm) Quasi-static Indentation Viscoelastic behavior tested between 23 C and 100 C: Creep response to a fast loading step Sample recovery after fast unloading Creep 350 Controlled Un-Loading Step Response 400 µn/0.1s Recovery Displacement Creep Displacement Recovery 50 Controlled Loading Step 500 µn/0.1s 11/02/ Indentation Displacement (nm) Time (s) Bruker Confidential 27

28 Creep rate (nm/s) Recovery rate (nm) Hardness (Gpa) Bruker Confidential 28 Creep and Recovery Analysis Hardness 50 Creep rate Recovery rate Temperature (degc) Temperature (degc) Creep Rate = Creep displacement / Holding time (10s) Recovery Rate = Recovery displacement / Holding time (10s)

29 Dynamic Dynamic Compliance, m/n Compliance, m/n Phase Shift, Phase shift, theta deg 11/02/2017 Bruker Confidential 29 Dynamic Model (a) Experimental - Model fit R= (b) K i m K s C i F o sin t C s m mass of the indenter 350 mg C i system damping coeff Ns/m C s specimen damping coeff.? K i spring constant 300 N/m K s contact stiffness? Amplitude Phase X o k m F C C tan 1 i s 2 k m k K s K i o C C i s F re q u e n cy, ra d /s Frequency, rad/s Contact stiffness K s 2E * A * 2E h 24.5 S.A. Syed Asif, K.J. Wahl and R.J. Colton Rev. Sci. Instrum. 70 (1999) 2408; J. Mater. Res. 15 (2000) 546. Contact stiffness Loss K '' s C s

30 11/02/2017 Bruker Confidential 30 nanodma III for Viscoelastic Material Dynamic Measurement of Hardness, Reduced Modulus, Storage Modulus, Loss Modulus, Tan Delta Kelvin Voigt Model Typical displacement amplitude: nm The contact area is assumed to stay constant during the load cycle. No opening and closing at the edge of the contact area. Asif et al., J. Appl. Phys. 90 (2001) 1192.

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32 Indentation Load (un) 11/02/2017 Bruker Confidential 32 nanodma III - Temperature xsol Stage for Temperature Control: nanodma III testing between 23 C and 100 C 5 indentations per temperature Displacement amplitude 1 nm Dynamic test at 10 Hz at max load Indentation Displacement (nm)

33 Modulus (GPa) 11/02/2017 Bruker Confidential 33 Tan Delta nanodma III - Temperature xsol Stage for Temperature Control: E, E and tan(delta) are averaged E drop from 23 C to 100 C Tan(delta) peak at approx. 80 C Storage Modulus Loss Modulus Tan Delta Temperature (degc)

34 11/02/2017 Bruker Confidential 34 nanodma III Comparison Comparison of nanodma III and macro DMA storage modulus and tan delta for 4 silicone samples with varying amounts of crosslinking agent Samples and Macro DMA testing courtesy of Donna Ebenstein, Department of Biomedical Engineering, Bucknell University.

35 11/02/2017 Bruker Confidential 35 nanodma III - Temperature Polycarbonate Storage and Loss Modulus as a Function of Frequency and Temperature Frequency: Hz; Temperature: C

36 11/02/2017 Bruker Confidential 36 nanodma III - Temperature Time-Temperature Superposition Predict viscoelastic properties over a broad frequency range, well outside the experimental range actual measurements can be conducted

37 Polycarbonate 150 C Master Curves Combine Frequency Sweeps and Use WLF Equation for a Full Time-Temperature Analysis 14.34(T 150) log a T = (T 150) 11/02/2017 Bruker Confidential 37

38 11/02/2017 Bruker Confidential 38 Conclusions Bruker s improved nanoscale dynamic mechanical testing enables: A truly continuous measurement of x (x = hardness, storage modulus, loss modulus, complex modulus, tan-delta, etc.) as a function of contact depth, frequency, and time. Application and testing accuracy across a wide range of materials from hydrogels to ultra-hard coating. Drift correction allows for long-duration frequency sweeps and creep tests to be reliably performed. Overcomes the inaccuracies of stiffness measurements on viscoelastic materials when employing quasi-static indentation. Measurements of E, E and tan delta comparable to measurements at larger length scales.

39 11/02/2017 Bruker Confidential 39 Contact Information Sales Enquiries: Dedicated Nanoindentation Customer Support: Helpdesk: (EU) (USA)

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