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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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Page 1: GL An Introduction to Nanomechanical testingtam.northwestern.edu/summerinstitute/_links/_courses/Nanoscale... · MEASURING NANOTECHNOLOGY MICRO MATERIALS An Introduction to Nanomechanical

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

Page 2: GL An Introduction to Nanomechanical testingtam.northwestern.edu/summerinstitute/_links/_courses/Nanoscale... · MEASURING NANOTECHNOLOGY MICRO MATERIALS An Introduction to Nanomechanical

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

Page 3: GL An Introduction to Nanomechanical testingtam.northwestern.edu/summerinstitute/_links/_courses/Nanoscale... · MEASURING NANOTECHNOLOGY MICRO MATERIALS An Introduction to Nanomechanical

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

Page 4: GL An Introduction to Nanomechanical testingtam.northwestern.edu/summerinstitute/_links/_courses/Nanoscale... · MEASURING NANOTECHNOLOGY MICRO MATERIALS An Introduction to Nanomechanical

MEASURING NANOTECHNOLOGY

MICROMATERIALS

Optimised performanceof thin film/coating system

Road-map for development of advanced materials

Mechanical propertiesHardnessStiffnessFracture toughnessLoad support

Tribological propertiesFrictionAdhesionResistance to•Abrasive Wear•Sliding Wear•Brittle fracture•Fatigue wear•Dynamic Loading•Corrosion

Design-in reliability

…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

Page 5: GL An Introduction to Nanomechanical testingtam.northwestern.edu/summerinstitute/_links/_courses/Nanoscale... · MEASURING NANOTECHNOLOGY MICRO MATERIALS An Introduction to Nanomechanical

MEASURING NANOTECHNOLOGY

MICROMATERIALS Viscoelastic Effects during Indentation

0

50

100

150

200

250

300

350

0 20 40 60 80 100

Cre

ep d

ispl

acem

ent (

nm)

Hold time (s)

Steel

Aluminum

Polyester

Epoxy

0

2

4

6

8

10

12

14

16

0 500 1000 1500 2000 2500

1 mN/s0.1 mN/s0.001 mN/s

Load

(mN

)

Depth (nm)

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

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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

3 modulesIndentationScanningImpact

10 options includingHigh temp testingContinuous compliancePin-on-disk wearMicroscopes/AFM3D imaging

NanoTest platform system

Microscope

Transfer stage (indenter/microscope)

MT head

NT head

Stage Assembly+Z

+Y

+X

Repositioning to 0.5 µm

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MEASURING NANOTECHNOLOGY

MICROMATERIALS

NanoTest options…

• 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)

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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

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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

0

20

40

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…

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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

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MEASURING NANOTECHNOLOGY

MICROMATERIALS

020406080

100120140160180200

0 20 40 60 80

0

0.05

0.1

0.15

0.2

0.25

% 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…

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MEASURING NANOTECHNOLOGY

MICROMATERIALS

0

100

200

300

400

0

50

100

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300

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400

450

0255075100

125

150

175

200

225

250

275

300

325

350

375

y

z

125-150 150-175

175-200 200-225

225-250 250-275

275-300 300-325

325-350 350-375

0

100

200

300

400

0

50

100

150

200

250

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350

400

450

00.

250.5

0.751

1.251.5

1.752

2.252.5

2.753

3.253.5

3.754

4.254.5

4.755

5.255.5

5.75

y

z

5.5-5.75

5.25-5.5

5-5.25

4.75-5

4.5-4.75

4.25-4.5

4-4.25

3.75-4

3.5-3.75

3.25-3.5

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

0

0.002

0.004

0.006

0.008

0.01

0.012

0 5 10 15 20 25 30

Depth (nm)

Load

(mN

)

Ultra-low load (10 µN) testing of soft samples

• For slow loading excellent thermal stability is necessary

Ultra-low load nanoindentation

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MEASURING NANOTECHNOLOGY

MICROMATERIALS

Nanoindentation – mechanical properties (hardness, modulus, creep)

Nanoscratch – tribological properties (resistance to abrasive/sliding wear)

The standard nanoscale mechanical/tribologicaltest techniques are very useful…

But…

• All material properties are temperature-dependent

Room Temperature or real temperature

MEASURING NANOTECHNOLOGY

MICROMATERIALS

NanoTest hot stage …

Dampingplate

Heaterelement

Thermocouple

Power supply +temperature controller

Insulation

Thermal shield

For clarity, separate diamond heater not shown

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MEASURING NANOTECHNOLOGY

MICROMATERIALS

At room temperature Si(111) undergoes phase changes…

Nanoindentation Parameters:-

Loading rate = 1.67 mN/sHold period at maximum load = 5sUnloading rate = 0.56 mN/s

“Pop-out” during unloading

Phase changes:-Si-I diamond-type to Si-II β-tin on loading…to Si-XII and Si-III on slow unloading

At slow unloading rate the pop-out only in room temp data

29 deg. C200 deg. C

• Different unloading slopes as test temperatures increases

• Elastic modulus reduced by 27% at 200 degrees C

• No observable “pop-out” at slow unloading rates

• Implications for microelectronics processing/applications

Nanoindentation of Si(111)

MEASURING NANOTECHNOLOGY

MICROMATERIALS

Reduced modulus solgel coating on Si as function of temperature

66.5

77.5

88.5

99.510

0 50 100 150

depth [nm]

Er [G

Pa] 100C

RT

20 µm spheroconical indenterRoom temp modulus agrees well with Berkovich dataModulus drops with temperature

Data courtesy Philips Research, Netherlands

Nanoindentation of solgel coatings on Si

Page 15: GL An Introduction to Nanomechanical testingtam.northwestern.edu/summerinstitute/_links/_courses/Nanoscale... · MEASURING NANOTECHNOLOGY MICRO MATERIALS An Introduction to Nanomechanical

MEASURING NANOTECHNOLOGY

MICROMATERIALS

AJ Muir Wood, V Gergely and TW Clyne, Gordon Laboratory, Dept of Materials Science and Technology, University of Cambridge. Proc SPIE 2004 (in press)

The NiTi shows shape memory behaviour above the transition temperature

Nanoindentation testing of NiTi at high temperature

MEASURING NANOTECHNOLOGY

MICROMATERIALS

High temperature friction

Double forcetransducer

Thermalinsulation

Diamond holder

Testprobe

Thermalshield

Fused quartz rod

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MEASURING NANOTECHNOLOGY

MICROMATERIALS

Friction coefficient at RT and 200ºC

Influence of Temperature on Friction Coefficient

00.10.2

0.30.40.5

0 50 100 150 200 250

Scan distance (microns)

Fric

tion

coef

ficie

nt 200C

Roomtemp.

1 mm dia. stainless steel ball + glass substrate

Scan speed 4 µµµµm/s

Normal load 4 mN

MEASURING NANOTECHNOLOGY

MICROMATERIALS

Stiction at 400ºC

Stiction at 400C and a Load of 4 mN

0

0.5

1

1.5

2

0 50 100 150 200 250

Scan distance (microns)

Fric

tion

coef

ficie

nt

Stiction at 400C and a Load of 0.4 mN

02468

101214

0 50 100 150 200 250

Scan distance (microns)

Fric

tion

coef

ficie

nt

1 mm dia. stainless steel ball + glass substrate

Scan speed 4 µµµµm/s

Normal load 4 mN

1 mm dia. stainless steel ball + glass substrate

Scan speed 4 µµµµm/s

Normal load 0.4 mN

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MEASURING NANOTECHNOLOGY

MICROMATERIALS

Influence of temperature on adhesion

Adhesion of Stainless Steel to Glass

-250

-200

-150

-100

-50

0

50

100

-1 -0.5 0 0.5 1 1.5 2 2.5 3 3.5

Load (mN)

Dis

plac

emen

t (nm

)RT

400C

1 mm dia. stainless steel ball + glass substrate

MEASURING NANOTECHNOLOGY

MICROMATERIALS Nano-and Micro-scratch test principle

loading

1. Force, displacement, friction, acoustic emission and time are recorded throughout the scratching of a test sample by a diamond probe

2. Can test much thinner coatings and more local scratch behaviour than conventional scratch test

coating substrate

Sample motion during loading makes nano-scratch tests possible…

transverse samplemotion with XYZ stage

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MEASURING NANOTECHNOLOGY

MICROMATERIALS

50 µm

100

µm

Precise determination of Critical load (Lc) for film failure • Friction force data• Displacement data• Microscopy

Carbon films on Si as protective overcoats for hard disk, MEMS

Track end

Friction

Depth

Nanoscratching of thin hard ta-C films on Si for MEMS

MEASURING NANOTECHNOLOGY

MICROMATERIALS

As hydroxyapatite isthe main CalciumPhosphate in bone,it is being considered as a biocompatible coating for artificial joint replacements

NanoTest system has been used to evaluate the abrasive wear resistance of HA coating…

Nanoscratch testing

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MEASURING NANOTECHNOLOGY

MICROMATERIALS

Multi-pass sub-critical load scratch testing

dplast

dtotalExperimental parameters:25 µm Rockwell probescratch load:- ramped to 1 mNtopography load 0.1 mNscan speed 0.5 µm/s Nano-scratching wear of PET film

Repeat scratches over the same wear track reveal gradual wear of oriented polyester [PET] film

MEASURING NANOTECHNOLOGY

MICROMATERIALS

2, 4, 6

1, 3, 5, 7

Nanotribology

MEASURING NANOTECHNOLOGY

MICROMATERIALS

2 different PET samples -clear differences in nano-scratching wearwith processing history...

Biaxially drawn PET film - 50% crystalline

dplast

dtotal

dplast

dtotal

• extent of ploughing

• differences inelastic recovery (dp/dt)

Uniaxially drawn PET film ~ 30% crystalline

Evaluate slidingwear resistance ofdifferent coatingformulations

Nanotribology

BD Beake (MML) and GJ Leggett (UMIST), Polymer 2002, 43, 319-327.

Page 20: GL An Introduction to Nanomechanical testingtam.northwestern.edu/summerinstitute/_links/_courses/Nanoscale... · MEASURING NANOTECHNOLOGY MICRO MATERIALS An Introduction to Nanomechanical

MEASURING NANOTECHNOLOGY

MICROMATERIALS Evaluation of Dental Composites

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

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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?

1N load repetitive contact testing reveals clear differences….

Collaboration with Ito Tecnologia Cerámica, Castellon, Spain

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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

100 200 300 400 500 600100

200

300

400

500

Impact depth (nm)

position (microns)

position (microns)

Variation in fatigue properties across finger nail of 42 yr old woman

2500-3000

2000-2500

1500-2000

1000-1500

500-1000

0-500

• No other nanoindentation system has the capability to do nano-impactso no other system can investigate toughness and fatigue at the nanoscale

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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?

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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)

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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

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MEASURING NANOTECHNOLOGY

MICROMATERIALS

Mapping variations in high-strain rate deformation

50 200

350

500

650

800

950

50

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

0 3 6 9 12 15 18 210

3

6

9

12

15

18

21

nm

position (microns)

position (microns)

Toughness map for ABS 25wt% rubber

360-400

320-360

280-320

240-280

200-240

Applications in Milling Prediction

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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

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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

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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

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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

0

200

400

600

800

1000

0 5 10 15 20 25rubber wt% loading

chan

ge

in c

rate

r vo

lum

e

du

rin

g im

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.

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New innovations

• Liquid cell• In two beta sites

• NanofrettingAbout to got Beta-site

status

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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

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www.micromaterials.co.ukwww.micromaterials.co.uk• references• customer profiles• application notes

[email protected]

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