Transcript Nanomaterials in Construction and Rehabilitation: Contributions and Perspectives of the US

Nanomaterials in Construction and
Rehabilitation:
Contributions and Perspectives of the US
National Science Foundation
Jorn Larsen-Basse and Ken P. Chong
Program Directors, Mechanics and Materials Engineering
National Science Foundation
Arlington, Virginia, USA
[email protected] [email protected]
2nd International Symposium on Nanotechnology in Construction
Bilbao, Spain, Nov. 13-16, 2005
Note: Opinions expressed are those of the authors only; NSF takes no position in
the matter
Overview of Presentation
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The National Science Foundation
Search for the Small
Technology of the Small
The Nanotechnology Initiative
Some Nanotechnology Opportunities Related to
Infrastructure
• Some Examples of Projects
• Expectations for Future
NSF
• Conceived by Roosevelt, operational 1950
• Independent US Government agency
• Supports basic research in all areas of science and
engineering
• Budget now about $ 6 billion
• Engineering is about 10%
• Infrastructure Materials Engineering is ~ 0.08%
• Mechanics and Materials Engineering is ~0.4%
NSF’s Funding Methods
• Unsolicited proposals: researcher-generated ideas (from
universities, mostly)
– free flowing, or in response to central initiatives
– most funds go to the PI-generated ideas; most new funds
are earmarked for initiatives
• Peer review; success rate low (10-20%)
• Awards - grants to universities for support of individual
investigators, groups, centers
• Some centers and networked equipment and/or computational
user facilities awarded in response to calls for proposals
• Research community helps define directions: reviewers,
program directors, workshops, unsolicited proposals
Long History of Tools to Search for “The
Small” Leads to the Present
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14th century – grinding of lenses for spectacles, Italy
1590 Dutch Janssen brothers make first microscope
1667 Robert Hooke publishes “Micrographia”
mid-19th century, metallograph (reflected light); microstructure
1938 Ruska develops electron microscope; dislocations, precipitates
1950+ electron microprobe leads to SEM; surface observations
1981 Binnig & Rohrer invent STM, Nobel Prize 1986. (Precursor
instrument used at NIST 1965-71 by Russell Young et al).
• STM leads to AFM; high resolution SEM, STEM
• Recent discoveries of new material forms fan the fires of investigation:
– 1996 Nobel prize for discovery of C60, Buckyball
– 1991 Iijima in Japan discovers carbon nanotube
Carbon Nanotubes
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SWNTs and MWNTs
Diameter: ~ 1 nm
Length: ~ 100 mm (and larger)
Perfect hexagonal structure
In-plane covalent (s) bonds: dominates
mechanical property
• Out-of-plane (p) gas cloud: determines
electrical property
Potential Applications
Nano-electronics; Nano-electro-mechanical systems;
Nano-composites
Mechanical Properties of Carbon Nanotubes
• Superior Mechanical Properties
– Elastic Modulus: ~ 1 TPa
– Yield Strain: More than 4%
– Buckling Strain: ~ 5% (aspect ratio of 1/6)
• Potential Application: Nano-composite
Compression
Bending
Torsion
Breaking Strain of Carbon Nanotubes
• Model the breaking strain calculated by molecular
dynamics as the critical strain for bifurcation in the
continuum analysis.
Breaking strain calculated by molecular dynamics
EZZ = 55%
Bifurcation strain predicted by the nanoscale continuum theory
EZZ = 52%
• Reasonable agreement between the continuum and atomistic approaches.
• No additional parameter fitting!
Properties of Carbon Nanotubes (CNT)
Best available
under development
Baseline Material,
available today
Emerging material,
carbon nanotubes
Single Crystal
bulk material (CNT)
1000
500
Specific
Modulus
GPa/(g/c3) 200
CNTFRP Composite
Long-term potential
of CNT material
100
50
20
10
0.1
CFRP Composite
Aluminum 2219
0.2
0.5
1
2
5
10
20
50
100
Specific Strength, GPa/(g/c3)
from NASA-larc
Technology of “The Small” has Advanced in
Step with Science
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Transistor – 1947, Bardeen & Brattain
Junction transistor ~ 1950, Shockley (the 3 got Nobel in ’56)
Integrated Circuit 1958, Kilby (Nobel in 2000)
Moore’s law 1964 – number of transistors/area doubles about every 1.5
years (1971: 2,250 transistors; 2003: Itanium 2 chip has 410,000,000
transistors). Constantly pushing the limits - nano is next: lithography?
quantum dots, quantum computing?
• Storage capacity of magnetic hard disk drives has followed similar path.
First 1956: 50 disks, 24” diameter, flying ht. 20+ Micrometers. First 1 Gb
storage1980,size of refrigerator, weight 550 lbs (250 kg). Now 1Gb drives
can be the size of a US quarter coin. Developments made possible by
smaller domains, smoother media, lower head flying height, thinner
overcoats and lubricants
• MEMS
• Nanotechnology
M. ROCO, ~2002
US Federally Funded Nanotechnology Initiative
(more at www.nano.gov)
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Budgets, in $$ millions
1997
National Science Foundation
65
Defence
32
Energy
7
Health, NIH
5
NIST
4
NASA
3
Total
116
2001
150
125
88
40
33
22
464
2005 (request)
305
276
211
89
53
35
982
• Similar activities in many other countries
• NSF funds small grants for exploratory research, groups of researchers,
large centers, and networks of user facilities for nanofabrication
Fiscal Year
2000
2001
2002
2003
2004
C. Plan 2005
NSF Law 03
$97M
$150M
$199M
$221M
$254M
$338M $384M
400
350
300
250
NSE ($M)
Congr. Bill
200
150
100
50
0
2000 2001 2002 2003 2004 2005
Defining the vision for the second strategic plan (II)
National Nanotechnology Initiative
2004
2004:
10-year
vision/plan
Energy
Agriculture
and Food
Societal
Implications
2004
Reports
Government
Plan (annual)
2004:
Survey
manufacturing
Other topical reports
on www.nano.gov
Update 10 year vision, and develop strategic plan
MC Roco, 3/16/05
NNI Outcomes 2001-05
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4000 projects at 500 institutions
25% or world investment in nano30,000 papers in 2004 (2x number for Si, 6x steel)
US – 875 nanotech companies, ~50% small
businesses, 60% have products, others license
• 60% of nano-patents and 70% of start-up companies
are in US; large % of patents for foreign companies
• World-wide 20,000 people work on nanotechnology
(some re-classified, e.g., from catalysts & some
cosmetics, to nano-)
Infrastructure Outcomes of 2001-2005:
NSF R&D Networks and User Facilities
• Network for Computational Nanotechnology (NCN)
7 universities (Purdue as the central node)
Nanoelectronic device simulation/modeling
• National Nanotechnology Infrastructure Network (NNIN)
13 universities with user facility
Develop measuring & manuf. tools, including NEPM
-Education and societal implications
• Oklahoma Nano Net (EPSCoR award)
• Centers:
16 Nanoscale Science and Engineering (NSEC) - 6 (2001); 2 (2003); 6 (2004); 2 (2005)
1 Nanotechnology Center for Learning and Teaching (NCLT)
6 new Materials Research Science and Engineering Centers (MRSEC)
NNI FY 2006 Budget Request
Total = $1,054 million
Areas of investment in FY2006
(Program Component Areas)
1.
2.
3.
4.
5.
6.
7.
Fundamental Nanoscale Phenomena and Processes
Nanomaterials
Nanoscale Devices and Systems
Instrumentation Research, Metrology, and Standards for
Nanotechnology
Nanomanufacturing
Major Research Facilities and Instrumentation
Acquisition
Societal Dimensions
Construction- and Infrastructure-Related
Opportunities in Nano• Most work to date has been in electronic and biomedical applications
• Potential construction-related applications:
– Smart aggregates and coatings acting as wireless sensors and
actuators
– Self-healing structural polymers, pavements; self-assembly
• Large surface/volume ratio gives new possibilities:
– Ultra-high strength, ultra-high ductility steels, polymers and even
concrete
– New composite materials; photocatalytic coatings
• Plus new tools are giving new understanding of basic materials
structure-property relations, especially needed for cement
Polymer Nanocomposites
NIST
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Flame retardant materials
Conducting polymers
Scratch resistant coatings
Self-healing materials
Self-disinfecting surfaces…
Nano-Clay Filled Polymers
NIST
• Certain types of clay naturally form
platelet structures
– Thickness just less than 1 nm
– High aspect ratios
• Lengths and widths are 25 to 2000 times the
thickness
– Gallery spacing between platelets between 1.5
nm and 2 nm
• Contain cations for charge balance
– Hold platelets together
• Use of just 1% to 5% by volume can
dramatically alter material behavior
– Properties related to flammability improved
– Mechanical properties improved
– Improvements often depend on ability to
separate and disperse platelets
• Organic treatment needs to be thermally
stable.
~ 1 nm
Si
Al, Mg
O
OH
Some Current Project Areas Supported by the
NSF Mechanics and Materials Programs
• Cement materials science
– Measure progress of hydration by high intensity nitrogen ion
beams
– Follow strength evolution by X-ray tomography plus elastic wave
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Self cleaning photocatalytic coating, field trial
Composites: nanotubes, nanoparticles in various matrices
Multiscale modeling of concrete, composites
Biosealant for cement, derived from genetically engineered
bacteria
• Workshop on cellulose nanotubes from wood
Example – Nanoscale alumina (40nm) / PMMA
graduate student - Ben Ash (NSF - Nanoinitiative)
• Order of magnitude
increase in ductility
accompanied by a
decrease in Tg, modulus
and strength
Stronger
80
NEAT PMMA
Stress (MPa)
70
60
50
40
30
PMMA + 5wt% Alumina
20
10
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0.1
0.2
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Strain (mm/mm)
0.4
• No change in MW,
tacticity
• No residual monomer
• NMR results support this
result
Interface
0.5
Weak
Interface
Nanocomposites vs “Micron”composites
• Interparticle distance decreases
• Surface area increases
• Interaction zone
o region of altered mobility and
chain conformation
o region of altered crystallinity
o small molecule migration
o crosslink density
o chemistry
Interaction Zone
Particle
Interaction zones will overlap at low volume
fractions (2 vol%)
L. SCHADLER, RPI
Nanotube Composites Offer Promises and
Challenges
• Nanotubes are super strong and also very flexible and they
have large surface area; with strong tube-matrix interfaces
one could have composites with the unusual combination of
both high stiffness and high ductility because nanocracking
and crack deflection are possible. Many questions remain:
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Wetting, adhesion, how measure, how manipulate?
Stress transfer, how model deformation zone near reinforcement
SWNT, MWNT, ropes, how do they deform?
Mixing is problem, and eventually quality control, mass production,
cost, health and many other issues have to be dealt with
– So far, most nano-composites have been nanoparticle- or nanotubefilled polymers rather than true composites
Vaia, Wagner, Materials Today,
Nov. 2004, 32-37
Vaia, Wagner, Materials Today,
Nov. 2004, 32-37
Metal Oxide Nanoparticles in Coatings
• TiO2 and ZnO used in nanosize forms in
sunscreens
– Photoreactive behavior
hu
H2O
• Good absorbers of UV light
• Deactivate and destroy:
– Bacteria, viruses, fungi
– Organic and inorganic pollutants in air and water
– Cancer cells
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O2
O2
CB
electron –
hole +
VB
H2O
H2O
O2
O2
If charge carriers get to
• Producing energy via photoelectrochemical cells surface:
O2superoxide
Applications include:
OH. hydroxyl radical
– “Self-disinfecting” surfaces
H2O2 hydrogen peroxide
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Paints and coatings with improved durability
Indoor air cleaners
Water treatment
Mitigation of air-borne biological agents
Solar cells
and other activated oxygen species can
be generated.
All are capable of further reaction with
organic materials for good or bad
NIST
Symbol of Purity
The Lotus Leaf
S
“The white lotus, born in the water and grown in the
Water, rises beyond the water and remains unsoiled
By the water” (ancient Indian Buddhist text)
“Nano-raspberries”, strongly water repellant surface,
silica spheres bonded to epoxy-based polymer film (Eindhoven U)
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N
Materials Today, March 2005, cover
Biosealant-producing genetically engineered microorganism; a) the original strain
b) Transformed with plasmid to produce exopolymer and CaCO3 (Bang)
Compressive Strength (psi)
6000
7 days
28 days
5248
5115
5045
5000
4810
4804
4796
4609
4500
4184
4072
4000
0
1
10
20
9
50
3
Cell Concentration (×10 cells/cm )
Length and time scale of Present day
mechanics
years
minutes
Proximal Probes,
i.e. AFM
millisec
Continuum
Models
Microstructural
Models
microsec
Atomic
Simulations
picosec
femtosec
Quantum
Simulations
*Courtesy W. Goddard
0.1 nm
AFM
Engineering
Design
Friction Machines,
i.e. SFA
1 nm
10 nm
1 mm
1 cm
meters
SFA
Modeling and Measuring the Structure and
Properties of Cement-Based Materials
http://ciks.cbt.nist.gov/monograph/
nm
REAL

m
mm
MODEL
Over 10,000 users from 83 countries per month
DISCUSSIONS OF COMMON
MODELING METHODS
• FIRST PRINCIPLE CALCULATIONS - TO SOLVE
SCHRODINGER’S EQ. AB INITIO, e.g. HATREE- FOCK
APPROX., DENSITY FUNCTIONAL THEORY,…
- COMPUTIONAL INTENSIVE, O(N4)
- UP TO ~ 3000 ATOMS
MOLECULAR DYNAMICS [MD] - DETERMINISTIC, e.g. W/
LENNARD JONES POTENTIAL
- MILLIONS TIMESTEPS OF INTEGRATION; TEDIOUS
- UP TO ~ BILLION ATOMS FOR NANO-SECONDS
• COMBINED MD & CONTINUUM MECHANICS [CM], e.g.
MAAD; LSU; BRIDGING SCALE; …
- PROMISING...
Summary and Outlook
• While nanotechnology has been the subject of much hype
there are many developments on the horizon which can
benefit the infrastructure and construction fields
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Materials
Coatings
Sensors
Durability
New designs and structures taking advantage of much stronger
materials, ductile concrete (?) and other advances
• Many advances depend on serious engineering of labdemonstrated concepts, from the pretty picture to the
useful product or structure
Shirai et al,
Nanoletters
Sept. 05
“Nanocar”