MEASURING NANOTECHNOLOGY MICRO MATERIALS An Introduction to Nanomechanical testing Nanoindentation Nanoscratch/nanowear On bio-Materials and other samples Dr Krish Narain, Micro Materials Ltd., Wrexham Bringing nanomechanical measurements into the real-world MEASURING NANOTECHNOLOGY MICRO MATERIALS Why do we need nanoindentation? • Coatings are getting more complex • Mechanical properties are critical • If we can understand them then we can engineer better materials • Yield, cost and performance benefits
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MEASURING NANOTECHNOLOGY
MICROMATERIALS
An Introduction to Nanomechanical testing
NanoindentationNanoscratch/nanowear
On bio-Materials and other samples
Dr Krish Narain, Micro Materials Ltd., Wrexham
Bringing nanomechanicalmeasurements into the real-world
MEASURING NANOTECHNOLOGY
MICROMATERIALS
Why do we need nanoindentation?
• Coatings are getting more complex• Mechanical properties are critical• If we can understand them then we can
engineer better materials• Yield, cost and performance benefits
MEASURING NANOTECHNOLOGY
MICROMATERIALS
• The NanoTest investigates properties on coatings from 5nm to 200 microns
• Provides hardness and toughness data of many types
• Automated running for multiple analysis• Looks at materials under working
conditions• Single, multiple layer or bulk properties
MEASURING NANOTECHNOLOGY
MICROMATERIALS
Key advantages for biomaterials testing
• The NanoTest system is based around a pendulum (see next slides for more details) which gives these key advantages for testing biomaterials…
• Nanoindentation testing with ultra-low thermal drift (typically 0.005 nm/s or less)
• Nanoscratch testing without bending springs• Nanoscale impact/fatigue testing (no other
instrument can do this)
Bringing nanomechanicalmeasurements into the real-world
MEASURING NANOTECHNOLOGY
MICROMATERIALS
Founded 1988, based in Wales• Application labs in UK, USA, Germany, Japan• Worldwide support network: LOT Oriel in Europe...
Aim: to become the world leader in the development andmanufacture of nanomechanical testing equipment
Pioneering and progressive approach:-• First commercial nano-impact tester for measuringtoughness and fatigue resistance
• First commercial high temperature nanomechanical testing stage
Micro Materials –Innovation track record
Bringing nanomechanical measurements into the real-world
MEASURING NANOTECHNOLOGY
MICROMATERIALS
To use the NanoTest system..
1) Nanoindentation module to obtain accurate hardness (H) and reduced modulus (Er) values for the coating
2) Scanning module to obtain critical load in scratch test
3) Nano-impact module to assess fracture resistance and durability under dynamic loading
4) High temperature stage to assess coating performance at elevated temperatures (to 750 degrees C)
NanoTest nanomechanical test capability
MEASURING NANOTECHNOLOGY
MICROMATERIALS
Optimised performanceof thin film/coating system
Road-map for development of advanced materials
Mechanical propertiesHardnessStiffnessFracture toughnessLoad support
…at the nanoscaleDurable product= Satisfied customer!
NanoindentationNano-scratchNano-impact
High temp testing
Lab tests at development stage
Test under industrially relevant conditions
MEASURING NANOTECHNOLOGY
MICROMATERIALS
Nanoindentation principle
loading
unloading
• force, displacement and time are recorded throughout indentation of sample by a diamond probe
Scanning = transverse sample movement during loadingImpact = sample oscillation at constant load
Beyond nanoindentation…
• No other technique provides quantitative information about both the elastic and plasticproperties of thin films and small volumes
Indentation curve
coatingcoating
substratesubstrate
MEASURING NANOTECHNOLOGY
MICROMATERIALS Viscoelastic Effects during Indentation
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ep d
ispl
acem
ent (
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Hold time (s)
Steel
Aluminum
Polyester
Epoxy
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1 mN/s0.1 mN/s0.001 mN/s
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(mN
)
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Hold time = 100 sec
Data: Courtesy Dr Raman Singh, SUNY Stonybrook
Creep effects as a function ofloading rate
Creep at constant load
MEASURING NANOTECHNOLOGY
MICROMATERIALS ISO standards – ISO 15477
4 mandatory user calibrations are needed:• Load• Depth• Diamond area function• Frame compliance
For example without DAF – you can measure Martens hardness – but this is only applicable to Micro Hardness measurements according to ISO standards
MEASURING NANOTECHNOLOGY
MICROMATERIALS
The NanoTest pendulum Advantages of the pendulum include…• large samples possible• calibrated contact load• high temperature stage• sample oscillation (impact)• options such as pin-on-disk wear testing and 2D levelling stage• symmetrical indents• scratching inhigh stiffnessdirection
Bringing nanomechanicalmeasurements into the real-world
MEASURING NANOTECHNOLOGY
MICROMATERIALS
a flexiblenanomechanicalproperty testing centre...
2 loading headsNano - 10 µN - 500 mNMicro - 0.1 N - 20 N
• High Temperature Stage• Automatic 2D levelling stage• High Load Head (20 N)• Micro-scale Pin-on-disk• Continuous Compliance• Humidity Control• Spherical Indentation• Powder Adhesion• Acoustic Emission• High Resolution Microscope• Zoom Microscope• In-situ AFM• Piezo stage Imaging• Open access to signals
NanoTest Options
MEASURING NANOTECHNOLOGY
MICROMATERIALS
How homogeneous is mycoating?An example of nanoindentation as a QA tool
• rapid, automatic schedulingof arrays of indentations - 10,000 pointsper single run - or 100 scratches
Indentation: mapping (1)
MEASURING NANOTECHNOLOGY
MICROMATERIALS
• NanoTest high resolution microscope used to exactly place indents• Osteonal bone is stiffer than interstitial bone
Nanoindentation into osteonal bone…
Nanoindentation of bone
MEASURING NANOTECHNOLOGY
MICROMATERIALS Bone: Nanoindentation creep
Bone is viscoelastic, so to obtain accurate H and E values, the tests need:-
• Slow loading• Long hold period at max. load for creep (180s)• Good thermal drift (as creep recovery can be important)
• Only the NanoTest system has additional software for investigating this creep deformation – which provides additional characterisation information on rate and extent of creep
Creep of osteonalbone fittedto a log function
MEASURING NANOTECHNOLOGY
MICROMATERIALS
Use of Nanoindentation to assess new candidate surface modification technologies for biomedical applications
Data from European project
“Ion Beam Surface Modification of Polymers for Improved Friction and Wear Properties”
Micro Materials Ltd (UK)University of Birmingham (UK)Technical University of Clausthal (Germany))SC Plasmaterm (Romania)Hungarian Academy of Sciences (Hungary)
Wear resistance predicted from H/E ratio correlates to Pin-on-Disk wear testsand Nano-tribology results
Follow-up project – dynamic loading and fatigue
MEASURING NANOTECHNOLOGY
MICROMATERIALS
Variation in loading curve and creep with loading rate
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20
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60
80
100
0.0001 0.001 0.01 0.1
loading rate (mN/s)
disp
lace
men
t (nm
)
after
before
creep
1. After 30s hold period at maximum load depth is the same in very slow and fast tests
2. Only an instrument with negligible thermal drift could perform these tests, with loading rates varying by x300
Loading history on polymer = load then hold for 30 s
No thermal drift correction necessary…
MEASURING NANOTECHNOLOGY
MICROMATERIALS
Nanoindentation of polymer-clay nanocomposites…
• to produce advanced materialswith improved mechanical properties by PEO intercalation between clay layers
• to accurately characterise their nanomechanical properties so synthetic and fabrication methods can be optimised
Ben Beake (MML), Shuaijin Chen, J Barry Hull and Fengge Gao(Polymer Engineering Centre, Nottingham Trent)
2 key aims…
1
2
MEASURING NANOTECHNOLOGY
MICROMATERIALS
Improving polymer performance…
Nanoindentation of PEO/Clay Nanocomposites
MEASURING NANOTECHNOLOGY
MICROMATERIALS
Ben Beake*, Shuaijin Chen J. Barry Hull and Fengge Gao J Nanosci. Nanotech. 2002 vol 2, 73-79.
• Hardness and stiffness of PEO film are dramatically improved by addition of high clay loading
Indentation on melt-synthesised PEO
G-105 clay/solution-synthesised PEO
Pure PEO
PEO/ 20 % clayLow hardness -influenced by creep?
Very high hardness atHigh clay loadings
Nanoindentation of PEO/Clay Nanocomposites
MEASURING NANOTECHNOLOGY
MICROMATERIALS
020406080
100120140160180200
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% G-105 Clay
A B
The variation with clay is striking
when creep data are fitted to d = A ln(Bt + 1)
A determines extent of creepB determines rate of creep
More clay – slows creep processExplains small decrease in hardness at low loading
Influence of creep on hardness…
Good fit tologarithmic creep equation
Nanoindentation of PEO/Clay Nanocomposites
MEASURING NANOTECHNOLOGY
MICROMATERIALS
Depth profiling with the load-partial-unload technique
100 W
25 W
100 W
25 W
20 cycle load-partial-unload experiment – takes 30 mins
Plasma-polymers deposited at 100 W and 25 W power…
MEASURING NANOTECHNOLOGY
MICROMATERIALS
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Nanomechanical properties of burnt polyurethane foams in resin
Modulus (GPa) Hardness (MPa) optical image
Nano-mechanical properties of heterogeneous, multi-phase soft samples can be quantitatively mapped
Mapping hardness and modulus
MEASURING NANOTECHNOLOGY
MICROMATERIALS
IPP Repeat Indentations
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(mN
)
Ultra-low load (10 µN) testing of soft samples
• For slow loading excellent thermal stability is necessary
Dental composite materials used to be evaluated by standard macroscale test methods – but results were inconsistent
So the NanoTest is being used to rapidly evaluate the abrasion resistance of new improved composite materials
NanoTest wear depth data for repeat scratches on common composites…
The new composites in this study were shown to have betterabrasion resistance than conventional materials
Scr
atch
dep
th
(mic
rons
)
MEASURING NANOTECHNOLOGY
MICROMATERIALS Nano-impact testing
Materials can fail by fatigue not overload so optimisation based on nanoindentation/scratch may be insufficient
for applications where materials are exposed in service and/or in processing to fatigue wear or erosive wear (impact wear)
Dynamic nanomechanical tests (nano-impact and contact fatigue) have been developed by Micro Materials to address this problem
The need for dynamic testing
MEASURING NANOTECHNOLOGY
MICROMATERIALS
Nano-impact testing - simulating fatigue wear and failure
Impact
Sample oscillation
2 different methods…
• High frequency oscillation• High cycle fatigue
• Accurately controlled impacts• Known energy to failure• Wear mechanisms
Pendulum impulse impact
MEASURING NANOTECHNOLOGY
MICROMATERIALS
Impact at high load = Contact fatigue testing
• A and C fracture easily but B and D do not fracture within 500s• Can we correlate with fracture toughness data? • Can we correlate with microstructure?
Collaboration with Ito Tecnologia Cerámica, Castellon, Spain
MEASURING NANOTECHNOLOGY
MICROMATERIALS
Unimplanted SiO2 1 x 1016 N cm-2
implanted SiO2
Damage regimes in the impact test:1 = before impact2 = plastic deformation3 = slow crack growth (fatigue)4 = abrupt failure and material removal5 = further slow crack growth
Fracture and fatigue wear by Nano-impact testing
MEMS: nanostructured Si and SiO2
• Fatigue resistance from time-to-failure
• Ion-implantationimproves toughness
BD Beake (MML), J Lu, Q Xue, and T Xu, (all Lanzhou Institute of Chemical Physics) Proc FMC8 2003
1 impact every 4 s in these tests
MEASURING NANOTECHNOLOGY
MICROMATERIALS Nano-impact mapping of biomaterials
• Initial results suggest the nano-impact test can be used to identify osteopaenia (2-5 times greater risk of osteoporosis in later life)
Grids of impacts to determine differences in toughness/ductility…
Collaboration in progress with Universities of Limerick and Lancaster
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Impact depth (nm)
position (microns)
position (microns)
Variation in fatigue properties across finger nail of 42 yr old woman
2500-3000
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• No other nanoindentation system has the capability to do nano-impactso no other system can investigate toughness and fatigue at the nanoscale
MEASURING NANOTECHNOLOGY
MICROMATERIALS
Damage mechanism in the impact test: before impact - plastic deformation - slow crack growth (fatigue) - abrupt failure and material removal - further slow crack growth
Fatigue and Fracture Wear of ta-C films
80 nmon Si
60 nmon Si
• time-to-first-failure to rank impact resistance• some plastic deformation of the substrate does occur (depth at failure)
5 nm
on Si
80 nmon Si
MEASURING NANOTECHNOLOGY
MICROMATERIALS
Diamond-like-carbon (DLC) has high hardness and low friction so it is being considered for many applications
But its fatigue properties have not been fully tested –this is particularly important asIt is prone to poor adhesionIt has been considered as an inert coating for biomedical devices
The NanoTest is being used to investigate the toughness and durability of DLC coatings to fatigue wear with the nano-impact facility…
DLC: is it tough enough for your application?
MEASURING NANOTECHNOLOGY
MICROMATERIALS
Impact failure of 550 nmDLC film on Silicon
Nano-impact shows how deposition conditionsinfluence coating performance• Time-to-failure• Failure mechanism
Coating debonding - adhesion failureAbrupt depth change at failure > film thickness
Coating fracture – cohesive failureDepth change at failure less than film thickness
CVD CoatingDepositionRF Power
BD Beake et al, Diamond and Related Materials, 11, 1606, 2002
MEASURING NANOTECHNOLOGY
MICROMATERIALS
Nano-impact can be used to assess the toughness and adhesion of DLC coatings under industrially relevant conditions
DLC suffers from brittlenessDLC suffers from high stressDLC suffers from poor adhesionDLC suffers from poor resistance to fatigue
Nano-impact is a very quick and easy way to optimise DLC performance
Next slide shows typical brittle fracture and debonding of DLC after repetitive contacts (impact)
MEASURING NANOTECHNOLOGY
MICROMATERIALS
Nano-impact can assess DLC performance
1. Under a range of contact conditions (I.e. from light to severe loading) – important since many tests are too gentle
2. Quickly
3. Provides clear-cut time-to-failure data
4. Microscopy confirms failure mode…(see next slide)
5. Can test on actual component
MEASURING NANOTECHNOLOGY
MICROMATERIALS
Hydrogenated DLC (a-C:H) Hydrogen-free DLC (a-C)
50 µµµµm 50 µµµµmRing-cracking
Nano-impact results on commercial DLC
Delamination occurs for the DLC on the left – it is not suitable for severe contact conditions
MEASURING NANOTECHNOLOGY
MICROMATERIALS
Mapping variations in high-strain rate deformation
50 200
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200Impact depth
(nm)
position (microns)
position (microns)
Mapping of fatigue properties across crab shell
5000-60004000-50003000-40002000-3000
• Nano-scale ductility of crab shell varies across the shell
• Finer “mesh sizes” can be used to investigate this behaviour at much smaller scale
• At this highly localised scale the ductility varies with distribution of micron/sub-micron sized rubber particles in the ABS matrix
Grids of impacts to determine differences in toughness/ductility…
Collaboration in progress with University of Maryland
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Toughness map for ABS 25wt% rubber
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Applications in Milling Prediction
MEASURING NANOTECHNOLOGY
MICROMATERIALS
Testing the viscoelastic properties of thin films and small volumes requires the ability to access a wide range of strain rates
The NanoTest system has far greater strain rate choice than other systems because
1. Ultra-slow loading, long creep tests etc, are possible due to excellent thermal stability (~0.001-0.01 nm/s)
2. Very high strain rates accessible – use nano-impact
Indentation: viscoelastic materials
MEASURING NANOTECHNOLOGY
MICROMATERIALS
Repetitive impact tests on brittle and ductile materials
• Focus on ability to absorb energy• More plastic deformation = more ductile• Less plastic deformation = less ductile
• Little plastic deformation before failure• Clear fracture event(s)• Time-to-failure characterises impact resistance
Less ductile
More ductile
Impact behaviour:brittle and ductile materials
MEASURING NANOTECHNOLOGY
MICROMATERIALS
Nano-impact of Rubber-modified ABS Polymer
Incorporation of 25 % rubber leads to greater depth change on repetitive impact at the same position
1 impact every 7 s; 5 mN impact force; spherical test probe
Nano-impact – ductile materials
MEASURING NANOTECHNOLOGY
MICROMATERIALS
5 repeat impact tests at each composition
Very reproducible behaviour - error bars are smaller than symbols
Geometric considerations used to convert depth to volume
• Rubber incorporation improves ability to absorb energy on impact by deforming plastically rather than fracturing (improved ductility)
Nano-impact - a new method of ductility testing
Variation in impact-induced plastic deformation with rubber loading
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chan
ge
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r vo
lum
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pac
tin
g (
um
)^2
The technique has considerable potential in evaluating the local fatigue behaviour and ductility of thin polymer films that are not capable of being tested by conventional methods that were designed for bulk samples
Ben Beake, Steve Goodes, Jim Smith and Fengge Gao, J Mater Res (2004) 237-247.
MEASURING NANOTECHNOLOGY
MICROMATERIALS
New innovations
• Liquid cell• In two beta sites
• NanofrettingAbout to got Beta-site
status
MEASURING NANOTECHNOLOGY
MICROMATERIALS
Conclusions
1. Nanoindentation is fast becoming an essential tool in the optimisation of the mechanical and tribological properties of thin coated systems and advanced materials, for applications where hardness and stiffness are important.
2. The pendulum arrangement has key advantages for reliable scratchtesting. Scratching occurs in high stiffness direction for pivot and direct calibration of tangential (frictional) forces are possible.
3. Nano-scratch and nano-wear tests can accurately reveal differences in coating adhesion and wear resistance of coatings and bulk materials. This information can be used to aid materials processing and coating design.
4. Together, the combination of nanoindentation, nanoscratch and nano-impact provides much information on the plastic, elastic, adhesive, fatigue wear and fracture properties of biomaterials
Bringing nanomechanicalmeasurements into the real-world