SWNT Quantum Wire
Nanostructured Carbon Conductors
Howard K. Schmidt, Ph.D.
Carbon Nanotechnology Laboratory
Rice University
Energy Advancement Leadership Conference
UH, GEMI & HARC
18 November, 2004
Carbon
Nanotechnology
Laboratory
“Making Buckytubes
“Be All They Can Be”
Launched 2003 as a division of CNST
Focuses SWNT Research of 10 Faculty in 6 Departments
Prof. Richard E. Smalley - Director
Dr. Howard K. Schmidt - Executive Director
Dr. Robert H. Hauge - Technology Director
Why SWNT?
MOLECULAR PERFECTION & EXTREME PROPERTIES
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The Strongest Fiber Possible
Thermal Conductivity of Diamond
The Unique Chemistry of Carbon
The Scale and Perfection of DNA
Selectable Electrical Properties
• Metallics Better Than Copper
• Semiconductors Better Than InSb or GaAs
• The Ultimate Engineering Material
Some SWNT Applications
Graphics Source: NASA
SWNT Quantum Wire
Expected Features
• 1-10x Copper Conductivity
• 6x Less Mass
• Stronger Than Steel
• Zero Thermal Expansion
Key Grid Benefits
• Reduced Power Loss
• Low-to-No Sag
• Reduced Mass
• Higher Power Density
SWNT Technology Benefits
• Type & Class Specific
• Higher Purity
• Lower Cost
• Polymer Dispersible
SWNT Tensile Strength
Predicted tensile
strength of single-wall
nanotubes >100 GPa
Calculated strain-tofailure >30%
Measurements on
small bundles found
strength over 60 GPa
Yakobson, et al., Comp. Mat. Sci. 8, 341 (1997).
Conductivity of Metallic SWNT
•
Measurements on individual metallic
SWNT on Si wafers with patterned
metal contacts
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Single tubes can pass 20 uA for
hours
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Equivalent to roughly a billion amps
per square centimeter!
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Conductivity measured twice that of
copper
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Ballistic conduction at low fields with
mean free path of 1.4 microns
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Similar results reported by many
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Despite chemical contaminants and
asymmetric environment
Dekker, Smalley, Nature, 386, 474-477 (1997). McEuen, et al, Phys.Rev.Lett.84, 6082
Quantum Tunneling
Alper Buldum and Jian Ping Lu, Phys. Rev. B 63, 161403 R (2001).
Tunneling Evidence
• Indirect indication of conductivity
by measuring lifetimes of photoexcited electrons
• Cooling mechanism is interaction
with phonons – just like electrical
resistivity
• Anomalously long life-times yield
mean free path of 15 microns (10x
single tubes)
• Based on bundles in
‘buckypapers’ – good local
symmetry and clean, but still
based on mixture of metals and
semi-conductors
• Results imply 10 – 25x better
conductivity than copper
Source: Tobias Hertl, et al, Phys. Rev. Lett. 84(21) (2000) 5002
Getting The Right Tubes
• Need Single Type of Metallic SWNT
• Current Growth Inadequate
– Mixtures of ~ 50 Types
– Mixtures of Metals, Semi-Metals &
Semiconductors
– Impure & Inefficient
• N,M Control Critical
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Quantum Wire
Electronics & Sensors
Biomedical Therapeutics
Energy Conversion Storage
• Seeded Growth Required
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Separates Nucleation From Growth
Eliminate By-Products & Purification
Vastly Improved Efficiency
Sort Once at Small Scale
Rolling Graphite - n,m Vectors
Chiral
angle
0,0
1,0
2,0
1,1
3,0
1,1
4,0
3,1
2,2
Zigzag
5,0
4,1
3,2
5,1
4,2
3,3
7,0
6,0
6,1
5,2
7,1
6,2
4,3
5,3
4,4
Ar
mc
8,0
ir
8,1
7,2
6,3
5,4
ha
9,0
9,1
8,2
7,3
6,4
5,5
10,0
10,1
9,2
8,3
7,4
6,5
12,0
11,1
10,2
9,3
8,4
7,5
6,6
11,0
10,3
8,5
7,6
11,3
9,6
8,7
11,5
10,6
9,7
8,8
12,3
11,4
10,5
9,5
13,1
12,2
10,4
8,6
7,7
12,1
11,2
9,4
13,0
10,7
9,8
SWNT Excitation Fluorescence
Excitation wavelength (nm) [vn cn transition]
Each peak comes from a specific semi-conducting SWNT n,m value
900
0.3000
0.2323
0.1798
0.1392
0.1078
0.08348
0.06463
0.05004
0.03875
0.03000
0.02323
0.01798
0.01392
0.01078
0.008348
0.006463
0.005004
0.003875
0.003000
800
700
600
500
400
300
900
1000
1100
1200
1300
1400
Emission wavelength (nm) [c1v1 transition]
1500
SWNT Seeded Growth
Current Results
1. Attach Catalyst
2. Deposit on Inert Surface
Key Starting Materials
• Have FeMoC Catalyst
• Have Short SWNT Seeds
• Have Soluble SWNT
Key Process Steps
• In-Solution Attachment
• Controlled Deposition
• Catalyst Docking
• Reductive Etching
• Growth is Next !!
4. SWNT Growth
3. “Dock” Catalyst
SWNTamp Production Concept
Hydro-carbon
feedstocks
SWNT+ FeMoC Catalyst
Seeded Growth
500 < T < 700 C
Mono-Type SWNT
(1000 lb / day )
Bulk
Output
“Inner Loop” Processing
Seed Preparation. (1 lb/ day)
Cut SWNT, Prep. Catalyst,
Functionalize, Attach, Dock
Production Scale-Up Path
• Rice made 1 mg / day in 1997
• Lab-scale reactor at 1 gm / hour (2002)
• CNI Pilot plant producing 20 lb /day
• CNI now testing 100 lb / day reactor
Forming SWNT Wires
• Need macro-crystalline SWNT fiber/wire
• Starting material is tangled at several scales
• Starting material has variety of diameters
and types
• Enormous Van der Waals forces make it
hard to separate SWNT bundles
50 mm
Dispersion in Super-Acids
• SWNT bundles swell in superacids
• Dispersion due to “protonation” &
intercalation of SWNTs
in 102% H2SO4
“Spaghetti”
In Oleum
V. A. Davis et. Al., Macromolecues 37, 154 (2004)
dried SWNT fiber
W.-F Hwang and Y. Wang
Cross section
Prototype Wire
- SWNT Fibers
Current Oleum Spinning Results
• Producing Neat SWNT Fibers
• Dry-Spun from Oleum
• 6 to 14 Wt. % SWNT Dope
• Extruded as 50 µm Dia. Fibers
• 109 Tubes in Cross Section
• 100 Meters Long
• Working On Alignment & Density
Quantum Wire on The Grid
Key Grid Benefits
• Eliminate Thermal Failures
• Reduce Wasted Power
• Reduce Urban R.O.W. Costs
• Enable Remote Generation
Our Overloaded Grid
The U. S. electric grid has become more unstable since 1998, with
more failures that affect large populations of customers than the
previous 50 years would predict
Sources: DOE, Roger Anderson & Amin, IEEE Computer Applications in Power, 2001
US Power Production Map
Currently, power is generated close to population centers
Source: DOE & Nate Lewis, Caltech
Renewable Resource Maps
Renewable sources generally remote from major population centers
Source: NREL
Solar Base-Load Power
Also for:
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Nathan S. Lewis, CalTech
Nukes
Hydro
Wind
Space
Lunar
??
3 TW
20 TW
Grid Applications & Benefits
• Eliminate Thermal-Sag Failure: Now a $100B+ a year problem.
• Short-Distance AC: AQW could increase throughput up to ten-fold
without increasing losses while using only existing towers and
rights-of-way. Avoid new construction in congested urban areas –
estimated over $100M per mile.
• Medium-Distance AC: AQW could decrease resistive losses and
voltage drop ten-fold if amperage were not increased. This would
improve grid dynamics significantly in the range between 100 and
300 miles, where voltage stability limits deliverable power.
• Long-Distance HVDC: AQW could permit amperage throughput
ten fold or reduce losses ten-fold. New conventional lines cost
$1M to $2M per mile, plus about $250M per AC/DC converter
station.
• Remote Power: Could enable utilization of large-scale
renewables and remote nuclear.
The Terawatt Challenge
50
50
45
40
35
30
25
20
15
10
5
0
2003
2050
45
40
14 Terawatts
30 -- 60 Terawatts
450 – 900 MBOE/day
35
210 M BOE/day
30
25
20
15
10
0.5%
5
20st Century = OIL
21st Century = ??
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The Basis of Prosperity: Energy
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Source: Internatinal Energy Agency
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ENERGY for 1010 people
• The biggest single challenge for the next few decades
• At MINIMUM, we need 10 Terawatts (150 M BOE/day)
from some new clean energy source by 2050
•
For worldwide peace and prosperity we need it to be cheap.
•
We simply can not do this with current technology.
•
We need Boys and Girls to enter Physical Science and
Engineering as they did after Sputnik.
•
Inspire in them a sense of MISSION
( BE A SCIENTIST - SAVE THE WORLD )
• We need a bold new APOLLO PROGRAM
to find the NEW ENERGY TECHNOLOGY
Help Wanted !
PhD Degrees in Science and Engineering
25000
Asians citizens
All fields of Science &
Engineering
PhD per year
20000
15000
US citizens, all fields of Science
and Engineering, (excluding
psychology & social sciences)
10000
US citizens,
Physical Sciences and
Engineering only
5000
0
1985
1990
1995
2000
2005
Year
Source: Science and Engineering Indicators, National Science Board, 2002