cosires 2004 helsinki june 28th – july 2nd irradiation-induced stiffening of carbon nanotube...

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Cosires 2004 Helsinki June Cosires 2004 Helsinki June 28th – July 2nd 28th – July 2nd Irradiation-induced Irradiation-induced stiffening of carbon stiffening of carbon nanotube bundles nanotube bundles Maria Sammalkorpi Maria Sammalkorpi (née Huhtala) (née Huhtala) 1 1 , , Arkady Krasheninnikov Arkady Krasheninnikov 2 , Antti Kuronen , Antti Kuronen 1 , , Jussi Aittoniemi Jussi Aittoniemi 1 , Kai Nordlund , Kai Nordlund 2 , Steve , Steve Stuart Stuart 3 , Kimmo Kaski , Kimmo Kaski 1 1 Laboratory of Computational Engineering, Helsinki Laboratory of Computational Engineering, Helsinki University of Technology University of Technology 2 Accelerator Laboratory, University of Helsinki Accelerator Laboratory, University of Helsinki 3 Department of Chemistry, Clemson University Department of Chemistry, Clemson University

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Cosires 2004 Helsinki June 28th – July 2ndCosires 2004 Helsinki June 28th – July 2nd

Irradiation-induced stiffening Irradiation-induced stiffening of carbon nanotube bundlesof carbon nanotube bundles

Maria Sammalkorpi Maria Sammalkorpi (née Huhtala)(née Huhtala)11,,

Arkady KrasheninnikovArkady Krasheninnikov22, Antti Kuronen, Antti Kuronen11, Jussi Aittoniemi, Jussi Aittoniemi11, , Kai NordlundKai Nordlund22, Steve Stuart, Steve Stuart33, Kimmo Kaski, Kimmo Kaski11

11Laboratory of Computational Engineering, Helsinki University of TechnologyLaboratory of Computational Engineering, Helsinki University of Technology22Accelerator Laboratory, University of HelsinkiAccelerator Laboratory, University of Helsinki

33Department of Chemistry, Clemson UniversityDepartment of Chemistry, Clemson University

Cosires 2004 Helsinki June 28th – July 2ndCosires 2004 Helsinki June 28th – July 2nd

OutlineOutline

IntroductionIntroduction

Irradiation as a means of tailoring carbon Irradiation as a means of tailoring carbon nanotube (CNT) and nanotube bundle nanotube (CNT) and nanotube bundle propertiesproperties– Irradiation effects in nanotubesIrradiation effects in nanotubes– Load transfer in multi-walled nanotubesLoad transfer in multi-walled nanotubes– Nanotube bundle stiffeningNanotube bundle stiffening

SummarySummary

Cosires 2004 Helsinki June 28th – July 2ndCosires 2004 Helsinki June 28th – July 2nd

Introduction: carbon nanotubes Introduction: carbon nanotubes (CNTs)(CNTs)

Tubular carbon moleculesTubular carbon molecules– StrongStrong covalent intra-tube covalent intra-tube

bonding bonding Outstanding axial tensile Outstanding axial tensile strength & Young’s strength & Young’s modulusmodulus

– WeakWeak van der Waals inter- van der Waals inter-tube bondingtube bonding

Ultra-low friction surfaces Ultra-low friction surfaces

Ideal candidates for Ideal candidates for reinforcement fibres in reinforcement fibres in compositescomposites– Problem: low shearProblem: low shear

Cosires 2004 Helsinki June 28th – July 2ndCosires 2004 Helsinki June 28th – July 2nd

Irradiation and nanotubesIrradiation and nanotubes

Improve load transfer?Improve load transfer?

VacanciesVacancies– axial weakeningaxial weakening– vacancy-vacancy covalent vacancy-vacancy covalent

bond formation [1]bond formation [1]

InterstitialsInterstitials– inside and between tubesinside and between tubes– mobilemobile– dimerizationdimerization

[1] R. Telling [1] R. Telling et alet al., Nat. Mat. 2, 333 ., Nat. Mat. 2, 333 (2003).(2003).

Simulation: MD with Simulation: MD with Brenner C-C interaction Brenner C-C interaction with long range van der with long range van der Waals extension by Waals extension by

Stuart Stuart et al.et al.

Cosires 2004 Helsinki June 28th – July 2ndCosires 2004 Helsinki June 28th – July 2nd

Caused by vacanciesCaused by vacancies

Young’s modulus:Young’s modulus:

YY00 intact tube Young’s modulus intact tube Young’s modulus

nnii defect concentration defect concentration

aaYiYi coefficients coefficients

Fitted aFitted aYiYi values values

Concentration must be Concentration must be high to reduce Yhigh to reduce Y

Irradiation induced structural Irradiation induced structural weakeningweakening

N

iYi ian

Y

Y

1

0 1

Cosires 2004 Helsinki June 28th – July 2ndCosires 2004 Helsinki June 28th – July 2nd

Structural weakening: Tensile Structural weakening: Tensile strengthstrength

Cosires 2004 Helsinki June 28th – July 2ndCosires 2004 Helsinki June 28th – July 2nd

Load transferLoad transfer

Can irradiation defects improve the load Can irradiation defects improve the load transfer?transfer?

Setup: What is the minimum force required Setup: What is the minimum force required to pull out the inner tube?to pull out the inner tube?

ContributionsContributions– capillary forcecapillary force– tube-tube shear equal at L~200nmtube-tube shear equal at L~200nm– defectsdefects

Cosires 2004 Helsinki June 28th – July 2ndCosires 2004 Helsinki June 28th – July 2nd

Force: defect-free nanotubesForce: defect-free nanotubes

Short (36Å) commensurate / incommensurate tube being pulled out from a longer one (62Å), at T=0KAt room temperature ~0.1MPa

Cosires 2004 Helsinki June 28th – July 2ndCosires 2004 Helsinki June 28th – July 2nd

Tubes with defectsTubes with defects

Single vacancies reconstruct to protrude a Single vacancies reconstruct to protrude a dangling bond 0.5-0.7Å out of plane [1]dangling bond 0.5-0.7Å out of plane [1]

Two vacancies in adjanced planes of graphite Two vacancies in adjanced planes of graphite can form a covalent bond [2]can form a covalent bond [2]

Interstitials are mobile in room temperatureInterstitials are mobile in room temperature– Model: metastable covalent configurationsModel: metastable covalent configurations

[1] El-Barbary [1] El-Barbary et alet al., PRB 68, 144107 (2003).., PRB 68, 144107 (2003).

[2] R. Telling [2] R. Telling et al.,et al., Nature Materials 2, 333 (2003). Nature Materials 2, 333 (2003).

Cosires 2004 Helsinki June 28th – July 2ndCosires 2004 Helsinki June 28th – July 2nd

Two vacancies

Interlayerinterstitial

Interlayer dimer

One vacancy(not covalent)

Tubes with defectsTubes with defects

Cosires 2004 Helsinki June 28th – July 2ndCosires 2004 Helsinki June 28th – July 2nd

Inter-shell bond strength: resultsInter-shell bond strength: results

Non-covalent bonding strength 0.1-0.4nN (vacancy)

Covalent bonding strength 4-8nN (2-vacancy)

Defects dominate at (D=6nm, L=500nm CNT)– 10-6Å-2 (~1/300nm, ~5x1017cm-3) for covalent binding– 10-5Å-2 (~1/10nm, ~2x1019cm-3) for non-covalent binding

Defects in nanotubes are realistic means for load transfer

Cosires 2004 Helsinki June 28th – July 2ndCosires 2004 Helsinki June 28th – July 2nd

Nanotube bundle stiffeningNanotube bundle stiffening

Ref. [1]: electron irradiation of bundles of Ref. [1]: electron irradiation of bundles of single-walled carbon nanotubes (SWNTs) single-walled carbon nanotubes (SWNTs) result in result in – (1) dramatic increase of the bundle bending (1) dramatic increase of the bundle bending

modulus modulus – (2) followed by a decrease at higher doses(2) followed by a decrease at higher doses

What is the reason for this nonlinear What is the reason for this nonlinear behavior?behavior?

[1] Kís [1] Kís et alet al., Nature Materials 3, 153 (2004).., Nature Materials 3, 153 (2004).

Cosires 2004 Helsinki June 28th – July 2ndCosires 2004 Helsinki June 28th – July 2nd

Bending modulusBending modulus

Bundle = cylindrical Bundle = cylindrical macroscopic barmacroscopic bar– Bending modulusBending modulus

Simulations: Y,GSimulations: Y,G– Y~vacanciesY~vacancies– G~covalent inter-tube G~covalent inter-tube

bondsbonds– YYBB

Cosires 2004 Helsinki June 28th – July 2ndCosires 2004 Helsinki June 28th – July 2nd

Young’s and shear modulus:Young’s and shear modulus:(5,5)-bundle(5,5)-bundle

aaYY = 1.2Å = 1.2Å

YY00 = 370GPa (uniformly = 370GPa (uniformly

loaded bulk bundle)loaded bulk bundle)

G = aG = aGG n nbondsbonds

aaGG = 14.5 N/m = 14.5 N/m

Ydef anY

Y10

Cosires 2004 Helsinki June 28th – July 2ndCosires 2004 Helsinki June 28th – July 2nd

Bending modulusBending modulus

Analytical approximations[1]Analytical approximations[1]– Cross sectionCross section– Number of secondary cascade Number of secondary cascade

atomsatoms

NNvacvac(dose, E)(dose, E)

NNbondsbonds(N(Nvacvac,interaction area),interaction area)

Y,G as a function of dose Y,G as a function of dose and Eand E

YYBB

[1] F. Banhart, Rep. Prog. Phys. 62, [1] F. Banhart, Rep. Prog. Phys. 62, 1181 (1999).1181 (1999).

Cosires 2004 Helsinki June 28th – July 2ndCosires 2004 Helsinki June 28th – July 2nd

SummarySummaryY only moderately sensive (-3% for 1/50Å density (5,5))Y only moderately sensive (-3% for 1/50Å density (5,5))Tensile strength may decrease by 50%Tensile strength may decrease by 50%– reconstruction improves strengthreconstruction improves strength

Irradiation induced defects pin CNTs effectivelyIrradiation induced defects pin CNTs effectively– 10-6Å-2 (covalent), 10-5Å-2 (non-covalent)

Preliminary results for bundle bending modulus– Increase and followed by decrease due to interplay between

1) Increased shear via inter-tube bonds2) Degrade of strength due to vacancies

– Overestimate of max YB, Y0 too large?

Irradiation good tool to improve nanotube mechanical properties for usage as reinforcement agents

[1] M. Sammalkorpi et al, submitted., [2] M. Huhtala et al, PRB 70, ?? (2004).

[1][1]

[2][2]